U.S. patent application number 16/495571 was filed with the patent office on 2020-04-02 for electrode for electrolysis, laminate, wound body, electrolyzer, method for producing electrolyzer, method for renewing electrode.
This patent application is currently assigned to ASAHI KASEI KABUSHIKI KAISHA. The applicant listed for this patent is ASAHI KASEI KABUSHIKI KAISHA. Invention is credited to Akiyasu FUNAKAWA, Toshinori HACHIYA, Yoshifumi KADO, Jun KOIKE.
Application Number | 20200102662 16/495571 |
Document ID | / |
Family ID | 65033958 |
Filed Date | 2020-04-02 |
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United States Patent
Application |
20200102662 |
Kind Code |
A1 |
FUNAKAWA; Akiyasu ; et
al. |
April 2, 2020 |
ELECTRODE FOR ELECTROLYSIS, LAMINATE, WOUND BODY, ELECTROLYZER,
METHOD FOR PRODUCING ELECTROLYZER, METHOD FOR RENEWING ELECTRODE,
METHOD FOR RENEWING LAMINATE, AND METHOD FOR PRODUCING WOUND
BODY
Abstract
The present invention relates to an electrode for electrolysis,
a laminate, a wound body, an electrolyzer, a method for producing
an electrolyzer, a method for renewing an electrode, a method for
renewing a laminate, and a method for producing a wound body. An
electrode for electrolysis according to one aspect of the present
invention has a mass per unit area of 48 mg/cm.sup.2 or less and a
force applied per unit massunit area of 0.08 N/mgcm.sup.2 or
more.
Inventors: |
FUNAKAWA; Akiyasu; (Tokyo,
JP) ; KADO; Yoshifumi; (Tokyo, JP) ; HACHIYA;
Toshinori; (Tokyo, JP) ; KOIKE; Jun; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASAHI KASEI KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Assignee: |
ASAHI KASEI KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
65033958 |
Appl. No.: |
16/495571 |
Filed: |
March 22, 2018 |
PCT Filed: |
March 22, 2018 |
PCT NO: |
PCT/JP2018/011535 |
371 Date: |
September 19, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25B 13/02 20130101;
C25B 11/00 20130101; C25B 15/00 20130101; C25B 11/02 20130101; C25B
11/035 20130101; C25D 1/08 20130101; C25B 9/08 20130101; C25B
11/0489 20130101; C25D 1/04 20130101; C25B 11/03 20130101; C25B
9/10 20130101; C25B 13/08 20130101 |
International
Class: |
C25B 11/04 20060101
C25B011/04; C25B 11/03 20060101 C25B011/03 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2017 |
JP |
2017-056524 |
Mar 22, 2017 |
JP |
2017-056525 |
Mar 20, 2018 |
JP |
2018-053139 |
Mar 20, 2018 |
JP |
2018-053144 |
Mar 20, 2018 |
JP |
2018-053145 |
Mar 20, 2018 |
JP |
2018-053146 |
Mar 20, 2018 |
JP |
2018-053149 |
Mar 20, 2018 |
JP |
2018-053217 |
Mar 20, 2018 |
JP |
2018-053231 |
Claims
1. An electrode for electrolysis having a mass per unit area of 48
mg/cm.sup.2 or less and a force applied per unit massunit area of
0.08 N/mgcm.sup.2 or more.
2. The electrode for electrolysis according to claim 1, wherein the
electrode for electrolysis comprises a substrate for electrode for
electrolysis and a catalytic layer, and the substrate for electrode
for electrolysis has a thickness of 300 .mu.m or less.
3. The electrode for electrolysis according to claim 1 or 2,
wherein a proportion measured by a method (3) below is 75% or more:
[Method (3)] An ion exchange membrane (170 mm square), which is
obtained by applying inorganic material particles and a binder to
both surfaces of a membrane of a perfluorocarbon polymer into which
an ion exchange group is introduced and a sample of electrode for
electrolysis (130 mm square) are laminated in this order; and the
laminate is placed on a curved surface of a polyethylene pipe
(outer diameter: 145 mm) such that the sample of electrode for
electrolysis in this laminate is positioned outside under
conditions of a temperature of 23.+-.2.degree. C. and a relative
humidity of 30.+-.5%, the laminate and the pipe are sufficiently
immersed in pure water, excess water deposited on a surface of the
laminate and the pipe is removed, and one minute after this
removal, then a proportion) of an area of a portion, in which the
sample of electrode for electrolysis is in close contact with the
membrane obtained by applying the inorganic material particles and
the binder to both the surfaces of the membrane of the
perfluorocarbon polymer into which the ion exchange group is
introduced, is measured.
4. The electrode for electrolysis according to claim 1 or 2,
wherein the electrode for electrolysis has a porous structure and
has an opening ratio of 5 to 90%.
5. The electrode for electrolysis according to claim 1 or 2,
wherein the electrode has a porous structure and has an opening
ratio of 10 to 80%.
6. The electrode for electrolysis according to claim 1 or 2,
wherein the electrode for electrolysis has a thickness of 315 or
less.
7. The electrode for electrolysis according to claim 1 or 2,
wherein a value obtained by measuring the electrode for
electrolysis by a method (A) below is 40 mm or less: [Method (A)]
Under conditions of a temperature of 23.+-.2.degree. C. and a
relative humidity of 30.+-.5%, a sample obtained by laminating the
ion exchange membrane and the electrode for electrolysis is wound
around and fixed onto a curved surface of a core material being
made of polyvinyl chloride and having an outer diameter .PHI. of 32
mm, and left to stand for 6 hours; thereafter, when the electrode
for electrolysis is separated from the sample and placed on a flat
plate, heights in a vertical direction at both edges of the
electrode for electrolysis L.sub.1 and L.sub.2 are measured, and an
average value thereof is used as a measurement value.
8. The electrode for electrolysis according to claim 1 or 2,
wherein a ventilation resistance is 24 kPas/m or less when the
electrode for electrolysis has a size of 50 mm.times.50 mm, the
ventilation resistance being measured under conditions of the
temperature of 24.degree. C., the relative humidity of 32%, a
piston speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s.
9. (canceled)
10. A laminate comprising the electrode for electrolysis according
to claim 1 or 2.
11. A wound body comprising the electrode for electrolysis
according to claim 1 or 2.
12. A laminate comprising: an electrode for electrolysis, and a
membrane or feed conductor in contact with the electrode for
electrolysis, wherein a force applied per unit massunit area of the
electrode for electrolysis on the membrane or feed conductor is
less than 1.5 N/mgcm.sup.2.
13. The laminate according to claim 12, wherein the force applied
per unit massunit area of the electrode for electrolysis on the
membrane or feed conductor is more than 0.005 N/mgcm.sup.2.
14. The laminate according to claim 12 or 13, wherein the feed
conductor is a wire mesh, a metal nonwoven fabric, a perforated
metal, an expanded metal, or a foamed metal.
15. The laminate according to claim 12 or 13, comprising, as at
least one surface layer of the membrane, a layer comprising a
mixture of hydrophilic oxide particles and a polymer into which ion
exchange groups are introduced.
16. The laminate according to claim 12 or 13, wherein a liquid is
interposed between the electrode for electrolysis and the membrane
or feed conductor.
17-60. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrode for
electrolysis, a laminate, a wound body, an electrolyzer, a method
for producing an electrolyzer, a method for renewing an electrode,
a method for renewing a laminate, and a method for producing a
wound body.
BACKGROUND ART
[0002] For electrolysis of an alkali metal chloride aqueous
solution such as salt solution and electrolysis of water, methods
by use of an electrolyzer including a membrane, more specifically
an ion exchange membrane or microporous membrane have been
employed. This electrolyzer includes many electrolytic cells
connected in series therein, in many cases. A membrane is
interposed between each of electrolytic cell to perform
electrolysis. In an electrolytic cell, a cathode chamber including
a cathode and an anode chamber including an anode are disposed back
to back with a partition wall (back plate) interposed therebetween
or via pressing by means of press pressure, bolt tightening, or the
like.
[0003] The anode and the cathode for use in these electrolyzers now
are each fixed to the anode chamber or the cathode chamber of an
electrolytic cell by a method such as welding and folding, and
thereafter, stored or transported to customers. Meanwhile, each
membrane in a state of being singly wound around a vinyl chloride
(VC) pipe is stored or transported to customers. Each customer
arranges the electrolytic cell on the frame of an electrolyzer and
interposes the membrane between electrolytic cells to assemble the
electrolyzer. In this manner, electrolytic cells are produced, and
an electrolyzer is assembled by each customer. Patent Literatures 1
and 2 each disclose a structure formed by integrating a membrane
and an electrode as a structure applicable to such an
electrolyzer.
CITATION LIST
Patent Literature
[0004] Patent Literature 1
[0005] Japanese Patent Laid-Open No. 58-048686 [0006] Patent
Literature 2
[0007] Japanese Patent Laid-Open No. 55-148775
SUMMARY OF INVENTION
Technical Problem
[0008] When electrolysis operation is started and continued, each
part deteriorates and electrolytic performance are lowered due to
various factors, and each part is replaced at a certain time point.
The membrane can be easily renewed by extracting from an
electrolytic cell and inserting a new membrane. In contrast, the
anode and the cathode are fixed to the electrolytic cell, and thus,
there is a problem of occurrence of an extremely complicated work
on renewing the electrode, in which the electrolytic cell is
removed from the electrolyzer and conveyed to a dedicated renewing
plant, fixing such as welding is removed and the old electrode is
striped off, then a new electrode is placed and fixed by a method
such as welding, and the cell is conveyed to the electrolysis plant
and placed back to the electrolyzer. It is considered herein that
the structure formed by integrating a membrane and an electrode via
thermal compression described in Patent Literatures 1 and 2 is used
for the renewing described above, but the structure, which can be
produced at a laboratory level relatively easily, is not easily
produced so as to be adapted to an electrolytic cell in an actual
commercially-available size (e.g., 1.5 m in length, 3 m in width).
Moreover, electrolytic performance (such as electrolysis voltage,
current efficiency, and common salt concentration in caustic soda)
and durability are extremely poor, and chlorine gas and hydrogen
gas are generated on the electrode interfacing the membrane. Thus,
when used in electrolysis for a long period, complete delamination
occurs, and the structure cannot be practically used.
[0009] The present invention has been made in view of the above
problems possessed by the conventional art and is intended to
provide an electrode for electrolysis, a laminate, a wound body, an
electrolyzer, a method for producing an electrolyzer, a method for
renewing an electrode, a method for renewing a laminate, and a
method for producing a wound body below.
(First Object)
[0010] It is an object of the present invention provide an
electrode for electrolysis, a laminate, and a wound body that make
transport and handling easier, markedly simplify a work when a new
electrolyzer is started or a degraded electrode is renewed, and
furthermore also can maintain or improve the electrolytic
performance.
(Second Object)
[0011] It is an object of the present invention to provide a
laminate that can improve the work efficiency during electrode
renewing in an electrolyzer and further can exhibit excellent
electrolytic performance also after renewing.
(Third Object)
[0012] It is an object of the present invention to provide a
laminate that can improve the work efficiency during electrode
renewing in an electrolyzer and further can exhibit excellent
electrolytic performance also after renewing, from a viewpoint
different from the second object described above.
(Fourth Object)
[0013] It is a fourth object of the present invention to provide an
electrolyzer, a method for producing an electrolyzer, and a method
for renewing a laminate that have excellent electrolytic
performance as well as can prevent damage of a membrane.
(Fifth Object)
[0014] It is an object of the present invention to provide a method
for producing an electrolyzer, a method for renewing an electrode,
and a method for producing a wound body that can improve the work
efficiency during electrode renewing in an electrolyzer.
(Sixth Object)
[0015] It is an object of the present invention to provide a method
for producing an electrolyzer that can improve the work efficiency
during electrode renewing in an electrolyzer, from a viewpoint
different from the fifth object described above.
(Seventh Object)
[0016] It is an object of the present invention to provide a method
for producing an electrolyzer that can improve the work efficiency
during electrode renewing in an electrolyzer, from a viewpoint
different from the fifth and sixth objects described above.
Solution to Problem
[0017] As a result of the intensive studies by the present
inventors to achieve the first object, production of an electrode
for electrolysis that has a small mass per unit area and can be
bonded to a membrane such as an ion exchange membrane and a
microporous membrane or a degraded electrode with a weak force
makes transport and handling easer, can markedly simplify a work
when a new electrolyzer is started or a degraded part is renewed,
and furthermore can markedly improve the characteristics in
comparison with the electrolytic performance in the conventional
art. Additionally, the present inventors have found that the
characteristics can be equivalent to or be improved than the
electrolytic performance of a conventional electrolytic cell, for
which renewing work is complicated, thereby having completed the
present invention.
[0018] That is, the present invention includes the following.
[1]
[0019] An electrode for electrolysis having a mass per unit area of
48 mg/cm.sup.2 or less and a force applied per unit massunit area
of 0.08 N/mgcm.sup.2 or more.
[2]
[0020] The electrode for electrolysis according to [1], wherein the
electrode for electrolysis comprises a substrate for electrode for
electrolysis and a catalytic layer, and the substrate for electrode
for electrolysis has a thickness of 300 .mu.m or less.
[3]
[0021] The electrode for electrolysis according to [1] or [2],
wherein a proportion measured by a method (3) below is 75% or
more:
[Method (3)]
[0022] A membrane (170 mm square), which is obtained by applying
inorganic material particles and a binder to both surfaces of a
membrane of a perfluorocarbon polymer into which an ion exchange
group is introduced, and a sample of electrode for electrolysis
(130 mm square) are laminated in this order; and the laminate is
placed on a curved surface of a polyethylene pipe (outer diameter:
145 mm; such that the sample of electrode for electrolysis in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then a proportion (%)
of an area of a portion, in which the sample of electrode for
electrolysis is in close contact with the membrane obtained by
applying the inorganic material particles and the binder to both
the surfaces of the membrane of the perfluorocarbon polymer into
which the ion exchange group is introduced, is measured.
[4]
[0023] The electrode for electrolysis according to any of [1] to
[3], wherein the electrode for electrolysis has a porous structure
and has an opening ratio of 5 to 90%.
[5]
[0024] The electrode for electrolysis according to any of [1] to
[4], wherein the electrode has a porous structure and has an
opening ratio of 10 to 80%.
[6]
[0025] The electrode for electrolysis according to any of [1] to
[5], wherein the electrode for electrolysis has a thickness of 315
.mu.m or less.
[7]
[0026] The electrode for electrolysis according to any of [1] to
[6], wherein a value obtained by measuring the electrode for
electrolysis by a method below is 40 mm or less:
[Method (A)]
[0027] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, a sample obtained by laminating
the ion exchange membrane and the electrode for electrolysis is
wound around and fixed onto a curved surface of a core material
being made of polyvinyl chloride and having an outer diameter .PHI.
of 32 mm, and left to stand for 6 hours; thereafter, when the
electrode for electrolysis is separated from the sample an1 placed
on a flat plate, heights in a vertical direction at both edges of
the electrode for electrolysis L.sub.1 and L.sub.2 are measured,
and an average value thereof is used as a measurement value.
[8]
[0028] The electrode for electrolysis according to any one of [1]
to [7], wherein a ventilation resistance is 24 kPas/m or less when
the electrode for electrolysis has a size of 50 mm.times.50 mm, the
ventilation resistance being measured under conditions of the
temperature of 24.degree. C., the relative humidity of 32%, a
piston speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s.
[9]
[0029] The electrode for electrolysis according to any of [1] to
[8], wherein the electrode comprises at least one element selected
from nickel (Ni) and titanium (Ti).
[10]
[0030] A laminate comprising the electrode for electrolysis
according to any of [1] to [9].
[11]
[0031] A wound body comprising the electrode for electrolysis
according to any of [1] to [9] or the laminate according to
[10].
[0032] As a result of the intensive studies to achieve the second
object, the present inventors have found that a laminate that
includes an electrode to be bonded to a membrane such as an ion
exchange membrane and a microporous membrane and to a feed
conductor such as a degraded existing electrode with a weak force
makes transport and handling easier, can markedly simplify a work
when a new electrolyzer is started or a degraded part is renewed,
and furthermore can also maintain or improve the electrolytic
performance, thereby having completed the present invention.
[0033] That is, the present invention includes the following
aspects.
[2-1]
[0034] A laminate comprising:
[0035] an electrode for electrolysis, and
[0036] a membrane or feed conductor in contact with the electrode
for electrolysis,
[0037] wherein a force applied per unit massunit area of the
electrode for electrolysis on the membrane or feed conductor is
less than 1.5 N/mgcm.sup.2.
[2-2]
[0038] The laminate according to [2-1], wherein the force applied
per unit mass'unit area of the electrode for electrolysis on the
membrane or feed conductor is more than 0.005 N/mgcm.sup.2.
[2-3]
[0039] The laminate according to [2-1] or [2-2], wherein the feed
conductor is a wire mesh, a metal nonwoven fabric, a perforated
metal, an expanded metal, or a foamed metal.
[2-4]
[0040] The laminate according to any of [2-1] to [2-3], comprising,
as at least one surface layer of the membrane, a layer comprising a
mixture of hydrophilic oxide particles and a polymer into which ion
exchange groups are introduced.
[2-5]
[0041] The laminate according to any of [2-1] to [2-4], wherein a
liquid is interposed between the electrode for electrolysis and the
membrane or feed conductor.
[0042] As a result of the intensive studies to achieve the third
object, the present inventors have found that the problems
described above can be solved by a laminate in which a membrane and
an electrode for electrolysis are partially fixed, thereby having
completed the present invention.
[0043] That is, the present invention includes the following
aspects.
[3-1]
[0044] A laminate comprising:
[0045] a membrane, and
[0046] an electrode for electrolysis fixed in at least one region
of a surface of the membrane,
[0047] wherein a proportion of the region on the surface of the
membrane is more than 0% and less than 93%.
[3-2]
[0048] The laminate according to [3-1], wherein the electrode for
electrolysis comprises at least one catalytic component selected
from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn,
Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,
Tb, and Dy.
[3-3]
[0049] The laminate according to [3-1] or [3-2], wherein at least a
portion of the electrode for electrolysis penetrates the membrane
and thereby is fixed in the region.
[3-4]
[0050] The laminate according to any one of [3-1] to [3-3], wherein
at least a portion of the electrode for electrolysis is located
inside the membrane and thereby fixed in the region.
[3-5]
[0051] The laminate according to any one of [3-1] to [3-4], further
comprising a fixing member for fixing the membrane and the
electrode for electrolysis.
[3-6]
[0052] The laminate according to [3-5], wherein at least a portion
of the fixing member externally grips the membrane and the
electrode for electrolysis.
[3-7]
[0053] The laminate according to [3-5] or [3-6], wherein at least a
portion of the fixing member fixes the membrane and the electrode
for electrolysis by magnetic force.
[3-8]
[0054] The laminate according to any one of [3-1] to [3-7],
wherein
[0055] the membrane comprises an ion exchange membrane comprising a
surface layer comprising an organic resin, and
[0056] the organic resin is present in the region.
[3-9]
[0057] The laminate according to any one of [3-1] to [3-8], wherein
the membrane comprises a first ion exchange resin layer and a
second ion exchange resin layer having an EW different from that of
the first ion exchange resin layer.
[3-10]
[0058] The laminate according to any one of [3-1] to [3-8], wherein
the membrane comprises a first ion exchange resin layer and a
second ion exchange resin layer having a functional group different
from that of the first ion exchange resin layer.
[0059] As a result of the intensive studies to achieve the fourth
object, the present inventors have found that the problems
described above can be solved by sandwiching at least a portion of
a laminate of a membrane and an electrode for electrolysis between
an anode side gasket and a cathode side gasket, thereby having
completed the present invention.
[0060] That is, the present invention includes the following
aspects.
[4-1]
[0061] An electrolyzer comprising:
[0062] an anode,
[0063] an anode frame that supports the anode,
[0064] an anode side gasket that is arranged on the anode
frame,
[0065] a cathode that is opposed to the anode,
[0066] a cathode frame that supports the cathode,
[0067] a cathode side gasket that is arranged on the cathode frame
and is opposed to the anode side gasket, and
[0068] a laminate of a membrane and an electrode for electrolysis,
the laminate being arranged between the anode side gasket and the
cathode side gasket,
[0069] wherein at least a portion of the laminate is sandwiched
between the anode side gasket and the cathode side gasket, and
[0070] a ventilation resistance is 24 kPas/m or less when the
electrode for electrolysis has a size of 50 mm.times.50 mm, the
ventilation resistance being measured under conditions of a
temperature of 24.degree. C., a relative humidity of 32%, a piston
speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s.
[4-2]
[0071] The electrolyzer according to [4-1], wherein the electrode
for electrolysis has a thickness of 315 .mu.m or less.
[4-3]
[0072] The electrolyzer according to [4-1] or [4-2], wherein a
value obtained by measuring the electrode for electrolysis by a
method (A) below is 40 mm or less:
[4-Method (A)]
[0073] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, a sample obtained by laminating
the ion exchange membrane and the electrode for electrolysis is
wound around and fixed onto a curved surface of a core material
being made of polyvinyl chloride and having an outer diameter .PHI.
of 32 mm, and left to stand for 6 hours; thereafter, when the
electrode for electrolysis is separated from the sample and placed
on a flat plate, heights in a vertical direction at both edges of
the electrode for electrolysis L1 and L2 are measured, and an
average value thereof is used as a measurement value.
[4-4]
[0074] The electrolyzer according to any of [4-1] to [4-3], wherein
a mass per unit area of the electrode for electrolysis is 48
mg/cm.sup.2 or less.
[4-5]
[0075] The electrolyzer according to any of [4-1] to [4-4], wherein
a force applied per unit massunit area of the electrode for
electrolysis is more than 0.005 N/mgcm.sup.2.
[4-6]
[0076] The electrolyzer according to any of [4-1] to [4-5], wherein
an outermost perimeter of the laminate is located farther outside
than an outermost perimeter each of the anode side gasket and the
cathode side gasket in a direction of a conducting surface.
[4-7]
[0077] The electrolyzer according to any of [4-1] to [4-6], wherein
the electrode for electrolysis comprises at least one catalytic
component selected from the group consisting of Ru, Rh, Pd, Ir, Pt,
Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W,
Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, and Dy.
[4-8]
[0078] The electrolyzer according to any of [4-1] to [4-7], wherein
at least a portion of the electrode for electrolysis penetrates the
membrane and thereby is fixed in the laminate.
[4-9]
[0079] The electrolyzer according to any of [4-1] to [4-7], wherein
at least a portion of the electrode for electrolysis is located
inside the membrane and thereby fixed in the laminate.
[4-10]
[0080] The electrolyzer according to any of [4-1] to [4-9], wherein
the laminate further comprises a fixing member for fixing the
membrane and the electrode for electrolysis.
[4-11]
[0081] The electrolyzer according to [4-10], wherein, in the
laminate, at least a portion of the fixing member penetrates and
thereby fixes the membrane and the electrode for electrolysis.
[4-12]
[0082] The electrolyzer according to [4-10] or [4-11], wherein, in
the laminate, the fixing member comprises a soluble material that
is soluble in a electrolyte solution.
[4-13]
[0083] The electrolyzer according to any of [4-10] to [4-12],
wherein, in the laminate, at least a portion of the fixing member
externally grips the membrane and the electrode for
electrolysis.
[4-14]
[0084] The electrolyzer according to any of [4-10] to [4-13],
wherein, in the laminate, at least a portion of the fixing member
fixes the membrane and the electrode for electrolysis by magnetic
force.
[4-15]
[0085] The electrolyzer according to any of [4-1] to [4-14],
wherein
[0086] the membrane comprises an ion exchange membrane comprising a
surface layer comprising an organic resin, and
[0087] the electrode for electrolysis is fixed by the organic
resin.
[4-16]
[0088] The electrolyzer according to any of [4-1] to [4-15],
wherein the membrane comprises a first ion exchange resin layer and
a second ion exchange resin layer having an EW different from that
of the first ion exchange resin layer.
[4-17]
[0089] A method for producing the electrolyzer according to any of
[4-1] to [4-16], the method comprising:
[0090] a step of sandwiching the laminate between the anode side
gasket and the cathode side gasket.
[4-18]
[0091] A method for renewing the laminate in the electrolyzer
according to any of [4-1] to [4-16], the method comprising:
[0092] a step of separating the laminate from the anode side gasket
and the cathode side gasket to thereby remove the laminate from the
electrolyzer, and
[0093] a step of sandwiching a new laminate between the anode side
gasket and the cathode side gasket.
[0094] As a result of the intensive studies to achieve the fifth
object, the present inventors have found that the problems
described above can be solved by use of an electrode for
electrolysis or a laminate of the electrode for electrolysis and a
new membrane, being in a wound body form, thereby having completed
the present invention.
[0095] That is, the present invention includes the following
aspects.
[5-1]
[0096] A method for producing a new electrolyzer by arranging an
electrode for electrolysis or a laminate of the electrode for
electrolysis and a new membrane in an existing electrolyzer
comprising an anode, a cathode that is opposed to the anode, and a
membrane that is arranged between the anode and the cathode,
[0097] wherein the electrode for electrolysis or the laminate,
being in a wound body form, is used.
[5-2]
[0098] The method for producing the electrolyzer according to
[5-1], comprising a step (A) of retaining the electrode for
electrolysis or the laminate in a wound state to thereby obtain the
wound body.
[5-3]
[0099] The method for producing the electrolyzer according to [5-1]
or [5-2], comprising a step (B) of releasing the wound state of the
wound body.
[5-4]
[0100] The method for producing the electrolyzer according to
[5-3], comprising a step (C) of arranging the electrode for
electrolysis or the laminate on a surface of at least one of the
anode and the cathode after the step (B).
[5-5]
[0101] A method for renewing an existing electrode by using an
electrode for electrolysis,
[0102] wherein the electrode for electrolysis being in a wound body
form is used.
[5-6]
[0103] The method for renewing the electrode according to [5-5],
comprising a step (A') of retaining the electrode for electrolysis
in a wound state to thereby obtain the wound body.
[5-7]
[0104] The method for renewing the electrode according to [5-5] or
[5-6], comprising a step (B') of releasing the wound state of the
wound body.
[5-8]
[0105] The method for renewing the electrode according to [5-7],
comprising a step (C') of arranging the electrode for electrolysis
on a surface of the existing electrode after the step (B').
[5-9]
[0106] A method for producing a wound body to be used for renewing
an existing electrolyzer comprising an anode, a cathode that is
opposed to the anode, and a membrane that is arranged between the
anode and the cathode, the method comprising:
[0107] a step of winding an electrode for electrolysis or a
laminate of the electrode for electrolysis and a new membrane to
thereby obtain the wound body.
[0108] As a result of the intensive studies to achieve the sixth
object, the present inventors have found that the problems
described above can be solved by integrating an electrode for
electrolysis with a new membrane at a temperature at which the
membrane does not melt, thereby having completed the present
invention.
[0109] That is, the present invention includes the following
aspects.
[6-1]
[0110] A method for producing a new electrolyzer by arranging a
laminate in an existing electrolyzer comprising an anode, a cathode
that is opposed to the anode, and a membrane that is arranged
between the anode and the cathode, the method comprising:
[0111] a step (A) of integrating an electrode for electrolysis with
a new membrane at a temperature at which the membrane does not melt
to thereby obtain the laminate, and
[0112] a step (B) of replacing the membrane in the existing
electrolyzer by the laminate after the step (A).
[6-7]
[0113] The method for producing the electrolyzer according to
[6-1], wherein the integration is carried out under normal
pressure.
[0114] As a result of the intensive studies to achieve the seventh
object, the present inventors have found that the problems
described above can be solved by an operation in an electrolyzer
frame, thereby having completed the present invention.
[0115] That is, the present invention includes the following
aspects.
[7-1]
[0116] A method for producing a new electrolyzer by arranging a
laminate comprising an electrode for electrolysis and a new
membrane in an existing electrolyzer comprising an anode, a cathode
that is opposed to the anode, a membrane that is fixed between the
anode and the cathode, and an electrolyzer frame that supports the
anode, the cathode, and the membrane, the method comprising:
[0117] a step (A) releasing a fixing of the membrane in the
electrolyzer frame, and
[0118] a step (B) of replacing the membrane by the laminate after
the step (A).
[7-2]
[0119] The method for producing the electrolyzer according to
[7-1], wherein the step (A) is carried out sliding the anode and
the cathode in an arrangement direction thereof, respectively.
[7-3]
[0120] The method for producing the electrolyzer according to [7-1]
or [7-2], wherein the laminate is fixed in the electrolyzer frame
by pressing from the anode and the cathode after the step (B).
[7-4]
[0121] The method for producing the electrolyzer according to any
of [7-1] to [7-3], wherein the laminate is fixed on a surface of at
least one of the anode and the cathode at a temperature at which
the laminate does not melt in the step (B).
[7-5]
[0122] A method for producing a new electrolyzer by arranging an
electrode for electrolysis in an existing electrolyzer comprising
an anode, a cathode that is opposed to the anode, a membrane that
is fixed between the anode and the cathode, and an electrolyzer
frame that supports the anode, the cathode, and the membrane, the
method comprising:
[0123] a step (A) of releasing a fixing of the membrane in the
electrolyzer frame, and
[0124] a step (B') of arranging the electrode for electrolysis
between the membrane and the anode or the cathode after the step
(A).
Advantageous Effects of Invention
[0125] (1) According to the electrode for electrolysis of the
present invention, it is possible to make transport and handling
easier, to markedly simplify a work when a new electrolyzer is
started or a degraded electrode is renewed, and furthermore, to
also maintain or improve the electrolytic performance.
[0126] (2) According to the laminate of the present invention, it
is possible to improve the work efficiency during electrode
renewing in an electrolyzer and furthermore, to exhibit excellent
electrolytic performance also after renewing.
[0127] (3) According to the laminate of the present invention, it
is possible to improve the work efficiency during electrode
renewing in an electrolyzer and further, to develop excellent
electrolytic performance also after renewing, from a viewpoint
different from (2) described, above.
[0128] (4) According to electrolyzer of the present invention, the
electrolyzer has excellent electrolytic performance as well as can
prevent damage of the membrane.
[0129] (5) According to the method for producing an electrolyzer of
the present invention, it is possible to improve the work
efficiency during electrode renewing in an electrolyzer.
[0130] (6) According to the method for producing an electrolyzer of
the present invention, it is possible to improve the work
efficiency during electrode renewing in an electrolyzer, from a
viewpoint different from (5) described above.
[0131] (7) According to the method for producing an electrolyzer of
the present invention, it is possible to improve the work
efficiency during electrode renewing in an electrolyzer, from a
viewpoint different from (5) and (6) described above.
BRIEF DESCRIPTION OF DRAWINGS
[0132] FIG. 1 illustrates a cross-sectional schematic view of an
electrode for electrolysis according to one embodiment of the
present invention.
[0133] FIG. 2 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane.
[0134] FIG. 3 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0135] FIG. 4 illustrates a schematic view for explaining a method
for forming the continuous holes of the ion exchange membrane.
[0136] FIG. 5 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0137] FIG. 6 illustrates a cross-sectional schematic view showing
a state of two electrolytic cells connected in series.
[0138] FIG. 7 illustrates a schematic view of an electrolyzer.
[0139] FIG. 8 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0140] FIG. 9 illustrates a cross-sectional schematic view of a
reverse current absorber included in the electrolytic cell.
[0141] FIG. 10 illustrates a schematic view of a method for
evaluating a force applied per unit massunit area (1) described in
Examples.
[0142] FIG. 11 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (1)
described in Examples.
[0143] FIG. 12 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (2)
described in Examples.
[0144] FIG. 13 illustrates a schematic view of a method for
evaluating winding around a column of 145 mm in diameter (3)
described in Examples.
[0145] FIG. 14 illustrates a schematic view of elastic deformation
test of the electrode described is Examples.
[0146] FIG. 15 illustrates a schematic view of a method for
evaluating softness after plastic deformation.
[0147] FIG. 16 illustrates a schematic view of an electrode
produced in Comparative Example 13.
[0148] FIG. 17 illustrates a schematic view of a structure used for
placing the electrode produced in Comparative Example 13 on a
nickel mesh feed conductor.
[0149] FIG. 18 illustrates a schematic view of an electrode
produced in Comparative Example 14.
[0150] FIG. 19 illustrates a schematic view of a structure used for
placing the electrode produced in Comparative Example 14 on a
nickel mesh feed conductor.
[0151] FIG. 20 illustrates a schematic view of an electrode
produced in Comparative Example 15.
[0152] FIG. 21 illustrates a schematic view of a structure used for
placing the electrode produced in Comparative Example 15 on a
nickel mesh feed conductor.
[0153] FIG. 22 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0154] FIG. 23 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane.
[0155] FIG. 24 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0156] FIG. 25 illustrates a schematic view for explaining a method
for forming the continuous holes of the ion exchange membrane.
[0157] FIG. 26 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0158] FIG. 27 illustrates a cross-sectional schematic view showing
a state of two electrolytic cells connected in series.
[0159] FIG. 28 illustrates a schematic view of an electrolyzer.
[0160] FIG. 29 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0161] FIG. 30 illustrates a cross-sectional schematic view of a
reverse current absorber included in the electrolytic cell.
[0162] FIG. 31 illustrates a schematic view of a method for
evaluating a force applied per unit massunit area (1) described in
Examples.
[0163] FIG. 32 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (1)
described in Examples.
[0164] FIG. 33 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (2)
described in Examples.
[0165] FIG. 34 illustrates a schematic view of a method for
evaluating winding around a column of 145 mm in diameter (3)
described in Examples.
[0166] FIG. 35 illustrates a schematic view of elastic deformation
test of the electrode described in Examples.
[0167] FIG. 36 illustrates a schematic view of a method for
evaluating softness after plastic deformation.
[0168] FIG. 37 illustrates a schematic view of an electrode
produced in Example 34.
[0169] FIG. 38 illustrates a schematic view of a structure used for
placing the electrode produced in Example 34 on a nickel mesh feed
conductor.
[0170] FIG. 39 illustrates a schematic view of an electrode
produced in Example 35.
[0171] FIG. 40 illustrates a schematic view of a structure used for
placing the electrode produced in Example 35 on a nickel mesh feed
conductor.
[0172] FIG. 41 illustrates a schematic view of an electrode
produced in Example 36.
[0173] FIG. 42 illustrates a schematic view of a structure used for
placing the electrode produced in Example 36 on a nickel mesh feed
conductor.
[0174] FIG. 43 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0175] FIG. 44 illustrates a cross-sectional schematic view
illustrating one embodiment of an ion exchange membrane.
[0176] FIG. 45 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0177] FIG. 46 illustrates a schematic view for explaining a method
for forming the continuous holes of the ion exchange membrane.
[0178] FIG. 47A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of an
electrode for electrolysis penetrates a membrane and thereby is
fixed. FIG. 47B illustrates an explanatory view illustrating a step
of obtaining the structure of FIG. 47A.
[0179] FIG. 48A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of an
electrode for electrolysis is located inside the membrane and
thereby fixed. FIG. 48B illustrates an explanatory view
illustrating a step of obtaining the structure of FIG. 48A.
[0180] FIGS. 49A to 49C illustrate cross-sectional schematic views
of a laminate illustrating an aspect in which a yarn-like fixing
member is used for fixing as a fixing member for fixing a membrane
and an electrode for electrolysis.
[0181] FIG. 50 illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which an organic resin is used
for fixing as a fixing member for fixing a membrane and an
electrode for electrolysis.
[0182] FIG. 51A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of a
fixing member externally grips a membrane and an electrode for
electrolysis to fix them. FIG. 51B illustrates a cross-sectional
schematic view of the laminate illustrating an aspect in which at
least a portion of a fixing member fixes the membrane and the
electrode for electrolysis by magnetic force.
[0183] FIG. 52 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0184] FIG. 53 illustrates a cross-sectional schematic view showing
a state of two electrolytic cells connected in series.
[0185] FIG. 54 illustrates a schematic view of an electrolyzer.
[0186] FIG. 55 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0187] FIG. 56 illustrates a cross-sectional schematic view of a
reverse current absorber that may be included in an electrolytic
cell.
[0188] FIG. 57 illustrates an explanatory view showing a laminate
in Example 1.
[0189] FIG. 58 illustrates an explanatory view showing a laminate
in Example 2.
[0190] FIG. 59 illustrates an explanatory view showing a laminate
in Example 3.
[0191] FIG. 60 illustrates an explanatory view showing a laminate
in Example 4.
[0192] FIG. 61 illustrates an explanatory view showing a laminate
in Example 5.
[0193] FIG. 62 illustrates an explanatory view showing a laminate
in Example 6.
[0194] FIG. 63 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0195] FIG. 64A illustrates a cross-sectional schematic view
showing a state of two electrolytic cells connected in series in a
conventional electrolyzer.
[0196] FIG. 64B illustrates a cross-sectional schematic view
showing a state of two electrolytic cells connected in series in
the electrolyzer of the present embodiment.
[0197] FIG. 65 illustrates a schematic view of an electrolyzer.
[0198] FIG. 66 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0199] FIG. 67 illustrates a cross-sectional schematic view of a
reverse current absorber that may be included in an electrolytic
cell.
[0200] FIG. 68 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0201] FIG. 69 illustrates a cross-sectional schematic view
illustrating one embodiment of an ion exchange membrane.
[0202] FIG. 70 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0203] FIG. 71 illustrates a schematic view for explaining a method
for forming the continuous holes of the ion exchange membrane.
[0204] FIG. 72 illustrates an explanatory view for explaining the
positional relation between the laminate and the gaskets.
[0205] FIG. 73 illustrates an explanatory view for explaining the
positional relation between the laminate and the gaskets.
[0206] FIG. 74A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of an
electrode for electrolysis penetrates a membrane and thereby is
fixed. FIG. 74B illustrates an explanatory view illustrating a step
of obtaining the structure of FIG. 12A.
[0207] FIG. 75A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of an
electrode for electrolysis located inside the membrane and thereby
fixed. FIG. 13B illustrates an explanatory view illustrating a step
of obtaining the structure of FIG. 75A.
[0208] FIGS. 76A to C illustrate cross-sectional schematic views of
a laminate illustrating an aspect in which a yarn-like fixing
member is used for fixing as a fixing member for fixing a membrane
and an electrode for electrolysis.
[0209] FIG. 77 illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which an organic resin is used
for fixing as a fixing member for fixing a membrane and an
electrode for electrolysis.
[0210] FIG. 78A illustrates a cross-sectional schematic view of a
laminate illustrating an aspect in which at least a portion of a
fixing member externally grips a membrane and an electrode for
electrolysis to fix them. FIG. 78B illustrates a cross-sectional
schematic view of the laminate illustrating an aspect in which at
least a portion of a fixing member fixes the membrane and the
electrode for electrolysis by magnetic force.
[0211] FIG. 79 illustrates a schematic view of a method for
evaluating a force applied per unit massunit area (1) described in
Examples.
[0212] FIG. 80 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (1)
described in Examples.
[0213] FIG. 81 illustrates a schematic view of a method for
evaluating winding around a column of 280 mm in diameter (2)
described in Examples.
[0214] FIG. 82 illustrates a schematic view of a method for
evaluating winding around a column of 145 mm in diameter (3)
described in Examples.
[0215] FIG. 83 illustrates a schematic view of flexibility
evaluation of the electrode described in Examples.
[0216] FIG. 84 illustrates a schematic view of a method for
evaluating softness after plastic deformation.
[0217] FIG. 85 illustrates a schematic view of an electrode
produced in Example 35.
[0218] FIG. 86 illustrates a schematic view of a structure used for
placing the electrode produced in Example 35 on a nickel mesh feed
conductor.
[0219] FIG. 87 illustrates a schematic view of an electrode
produced in Example 36.
[0220] FIG. 88 illustrates a schematic view of a structure used for
placing the electrode produced in Example 36 on a nickel mesh feed
conductor.
[0221] FIG. 89 illustrates a schematic view of an electrode
produced in Example 37.
[0222] FIG. 90 illustrates a schematic view of a structure used for
placing the electrode produced in Example 37 on a nickel mesh feed
conductor.
[0223] FIG. 91 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0224] FIG. 92 illustrates a cross-sectional schematic view showing
a state of two electrolytic cells connected in series.
[0225] FIG. 9a illustrates a schematic view of an electrolyzer.
[0226] FIG. 94 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0227] FIG. 95 illustrates a cross-sectional schematic view of a
reverse current absorber that may be included in an electrolytic
cell.
[0228] FIG. 96 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0229] FIG. 97 illustrates a cross-sectional schematic view
illustrating one embodiment of an ion exchange membrane.
[0230] FIG. 98 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0231] FIG. 99 illustrates a schematic view for explaining a method
for forming the continuous holes of the ion exchange membrane.
[0232] FIG. 100 illustrates a schematic view of a laminate produced
in Example 1.
[0233] FIG. 101 illustrates a schematic view of the case where the
laminate produced in Example 1 is wound to form a wound body.
[0234] FIG. 102 illustrates a schematic view of a laminate produced
in Example 4.
[0235] FIG. 103 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0236] FIG. 104 illustrates a cross-sectional schematic view
showing a state of two electrolytic cells connected in series.
[0237] FIG. 105 illustrates a schematic view of an
electrolyzer.
[0238] FIG. 106 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0239] FIG. 107 illustrates a cross-sectional schematic view of a
reverse current absorber that may be included in an electrolytic
cell.
[0240] FIG. 108 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0241] FIG. 109 illustrates a cross-sectional schematic view
illustrating one embodiment of an ion exchange membrane.
[0242] FIG. 110 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0243] FIG. 111 illustrates a schematic view for explaining a
method for forming the continuous holes of the ion exchange
membrane.
[0244] FIG. 112 illustrates a cross-sectional schematic view of an
electrolytic cell.
[0245] FIG. 113 illustrates a cross-sectional schematic view
showing a state of two electrolytic cells connected in series.
[0246] FIG. 114 illustrates a schematic view of an
electrolyzer.
[0247] FIG. 115 illustrates a schematic perspective view showing a
step of assembling the electrolyzer.
[0248] FIG. 116 illustrates a cross-sectional schematic view of a
reverse current absorber that may be included in an electrolytic
cell.
[0249] FIG. 117(A) illustrates a schematic view of an electrolyzer
for explaining one example of each step according to a first aspect
of the present embodiment. FIG. 117(B) illustrates a schematic
perspective view corresponding to FIG. 117(A).
[0250] FIG. 118(A) illustrates a schematic view of an electrolyzer
for explaining one example of each step according to a second
aspect of the present embodiment. FIG. 118(B) illustrates a
schematic perspective view corresponding to FIG. 118(A).
[0251] FIG. 119 illustrates a cross-sectional schematic view of an
electrode for electrolysis in one embodiment of the present
invention.
[0252] FIG. 120 illustrates a cross-sectional schematic view
illustrating one embodiment of an ion exchange membrane.
[0253] FIG. 121 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane.
[0254] FIG. 122 illustrates a schematic view for explaining a
method for forming the continuous holes of the ion exchange
membrane.
DESCRIPTION OF EMBODIMENTS
[0255] Hereinbelow, as for embodiments of the present invention
(hereinbelow, may be referred to as the present embodiments),
<First embodiment> to <Seventh embodiment> will be each
described in detail, with reference to drawings as required. The
embodiments below are illustration for explaining the present
invention, and the present invention is not limited to the contents
below. The accompanying drawings illustrate one example of the
embodiments, and embodiments should not be construed to be limited
thereto. The present invention may be appropriately modified and
carried out within the spirit thereof. In the drawings, positional
relations such as top, bottom, left, and right are based on the
positional relations shown in the drawing unless otherwise noted.
The dimensions and ratios in the drawings are not limited to those
shown.
First Embodiment
[0256] Here, a first embodiment of the present invention will be
described in detail with reference to FIGS. 1 to 21.
[Electrode for Electrolysis]
[0257] An electrode for electrolysis of the first embodiment
(hereinafter, in the section of <First embodiment>, simply
referred to as "the present embodiment") can provide a good
handling property, has a good adhesive force to a membrane such as
an ion exchange membrane and a microporous membrane, a degraded
electrode, a feed conductor having no catalyst coating, and the
like, and further, has a mass per unit area of 48 mg/cm.sup.2 or
less from the viewpoint of economy. The mass per unit area is
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less in respect of the above, and furthermore is
preferably 15 mg/cm.sup.2 or less from the comprehensive viewpoint
including handling property, adhesion, and economy. The lower limit
value is not particularly limited but is of the order of 1
mg/cm.sup.2, for example.
[0258] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[0259] The electrode for electrolysis of the present embodiment has
a force applied per unit massunit area of 0.08 N/(mgcm.sup.2) or
more from the viewpoint of enabling a good handling property to be
provided and having a good adhesive force to a membrane such as an
ion exchange membrane and a microporous membrane, a degraded
electrode, a feed conductor having no catalyst coating, and the
like. The force applied per unit massunit area is preferably 0.1
N/(mgcm.sup.2) or more, more preferably 0.14 N/(mgcm.sup.2) or more
in respect of the above, and more preferably 0.2 N/(mgcm.sup.2) or
more from the viewpoint of further facilitating handling in a large
size (e.g., a size of 1.5 m.times.2.5 m). The upper limit value is
not particularly limited, but is preferably 1.6 N/(mgcm.sup.2) or
less, more preferably less than 1.6 N/(mgcm.sup.2), further
preferably less than 1.5 N/(mgcm.sup.2), even further preferably
1.2 N/mgcm.sup.2 or less, still more preferably 1.20 N/mgcm.sup.2
or less. The upper limit value is even still more preferably 1.1
N/mgcm.sup.2 or less, further still more preferably 1.10
N/mgcm.sup.2 or less, particularly preferably 1.0 N/mgcm.sup.2 or
less, especially preferably 1.00 N/mgcm.sup.2 or less.
[0260] From the viewpoint that the electrode for electrolysis of
the present embodiment, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness of 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
[0261] The electrode for electrolysis of the present embodiment,
which has a good adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, as
described above, can be integrated with a membrane such as an ion
exchange membrane and a microporous membrane and used. For this
reason, on renewing the electrode, the electrode can he renewed by
a work as simple as renewing the membrane, without a complicated
substituting work such as stripping off the electrode fixed on the
electrolytic cell, and thus, the work efficiency is markedly
improved. Even in the case where only a feed conductor is placed in
a new electrolytic cell (i.e., an electrode including no catalyst
layer placed), only attaching the electrode for electrolysis of the
present embodiment to the feed conductor enables the electrode to
function. Thus, it may be also possible to markedly reduce or
eliminate catalyst coating.
[0262] Further, according to the electrode for electrolysis of the
present embodiment, it is possible to make the electrolytic
performance comparable to or higher than those of a new
electrode.
[0263] The electrode for electrolysis of the present embodiment can
be stored or transported to customers in a state where the
electrode wound around a vinyl chloride pipe or the like (in a
rolled state or the like), making handling markedly easier.
[0264] The force applied can be measured by methods (i) or (ii)
described below, which are as described in Examples in detail. As
for the force applied, the value obtained by the measurement of the
method (i) (also referred to as "the force applied (1)") and the
value obtained by the measurement of the method (ii) (also referred
to as "the force applied (2)") may be the same or different, and
either of the values is 0.08 N/(mgcm.sup.2) or more.
[0265] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[Method (i)]
[0266] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode for electrolysis (130 mm square) are laminated in this
order. After this laminate is sufficiently immersed in pure water,
excess water deposited on the surface of the laminate is removed to
obtain a sample for measurement. The arithmetic average surface
roughness (Ra) of the nickel plate after the blast treatment was
0.7 .mu.m. The specific method for calculating the arithmetic
average surface roughness (Ra) is as described in Examples.
[0267] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode for
electrolysis in this sample for measurement is raised in a vertical
direction at 10 mm/minute using a tensile and compression testing
machine, and the load when the sample of electrode for electrolysis
is raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[0268] This average value is divided by the area of the overlapping
portion of the sample of electrode for electrolysis and the ion
exchange membrane and the mass of the portion overlapping the ion
exchange membrane in the sample of electrode for electrolysis to
calculate the force applied per unit massunit area (1)
(N/mgcm.sup.2).
[0269] The force applied per unit massunit area (1) obtained by the
method is 0.08 N/(mgcm.sup.2) or more, preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode, and a feed conductor having no
catalyst coating, and more preferably 0.2 N/(mgcm.sup.2) or more
from the viewpoint of further facilitating handling in a large size
(e.g., a size of 1.5 m.times.2.5 m). The upper limit value is not
particularly limited, but is preferably 1.6 N/(mgcm.sup.2) or less,
more preferably less than 1.6 N/(mgcm.sup.2), further preferably
less than 1.5 N/(mgcm.sup.2), even further preferably 1.2
N/mgcm.sup.2 or less, still more preferably 1.20 N/mgcm.sup.2 or
less. The upper limit value is even still more preferably 1.1
N/mgcm .sup.2 or less, further still more preferably 1.10
N/mgcm.sup.2 or less, particularly preferably 1.0 N/mgcm.sup.2 or
less, especially preferably 1.00 N/mgcm.sup.2 or less.
[0270] When the electrode for electrolysis of the present
embodiment satisfies the force applied (1), the electrode can be
integrated with a membrane such as an ion exchange membrane and a
microporous membrane, for example, and used. Thus, on renewing the
electrode, the substituting work for the cathode and anode fixed on
the electrolytic cell by a method such as welding is eliminated,
and the work efficiency is markedly improved. Additionally, by use
of the electrode for electrolysis of the present embodiment as an
electrode integrated with the ion exchange membrane, it is possible
to make the electrolytic performance comparable to or higher than
those of a new electrode.
[0271] On shipping a new electrolytic cell, an electrode fixed on
an electrolytic cell has been subjected to catalyst coating
conventionally. Since only combination of an electrode having no
catalyst coating with the electrode for electrolysis of the present
embodiment can allow the electrode to function as an electrode, it
is possible to markedly reduce or eliminate the production step and
the amount of the catalyst for catalyst coating. A conventional
electrode of which catalyst coating is markedly reduced or
eliminated can be electrically connected to the electrode for
electrolysis of the present embodiment and allowed to serve as a
feed conductor for passage of an electric current.
[Method (ii)]
[0272] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode for electrolysis (130 mm square) are laminated in this
order. After this laminate is sufficiently immersed in pure water,
excess water deposited on the surface of the laminate is removed to
obtain a sample for measurement. Under conditions of a temperature
of 23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode for electrolysis in this sample for measurement
is raised in a vertical direction at 10 mm/minute using a tensile
and compression testing machine, and the load when the sample of
electrode for electrolysis is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[0273] This average value is divided by the area of the overlapping
portion of the sample of electrode for electrolysis and the nickel
plate and the mass of the sample of electrode for electrolysis in
the portion overlapping the nickel plate to calculate the adhesive
force per unit massunit area (2) (N/mgcm.sup.2).
[0274] The force applied per unit massunit area (2) obtained by the
method (ii) is 0.08 N/(mgcm.sup.2) or more, preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode, and a feed conductor having no
catalyst coating, and more preferably 0.14 N/(mgcm.sup.2) or more
from the viewpoint of further facilitating handling in a large size
(e.g., a size of 1.5 m.times.2.5 m). The upper limit value is not
particularly limited, but is preferably 1.6 N/(mgcm.sup.2) or less,
more preferably less than 1.6 N/(mgcm.sup.2), further preferably
less than 1.5 N/(mgcm.sup.2), even further preferably 1.2
N/mgcm.sup.2 or less, still more preferably 1.20 N/mgcm.sup.2 or
less. The upper limit value is even still more preferably 1.1
N/mgcm.sup.2 or less, further still more preferably 1.10
N/mgcm.sup.2 or less, particularly preferably 1.0 N/mgcm.sup.2 or
less, especially preferably 1.00 N/mgcm.sup.2 or less.
[0275] The electrode for electrolysis of the present embodiment, if
satisfies the force applied (2), can be stored or transported to
customers in a state where the electrode is wound around a vinyl
chloride pipe or the like (in a rolled state or the like), making
handling markedly easier. By attaching, the electrode for
electrolysis of the present embodiment to a degraded electrode, it
is possible to make the electrolytic performance comparable to or
higher than those of a new electrode.
[0276] In the present embodiment, as the liquid included between
the membrane such as an ion exchange membrane and a macroporous
membrane, the electrode for electrolysis or the feed conductor
(degraded electrode or electrode having no catalyst coating) and
the electrode for electrolysis, any liquid, such as water and
organic solvents, can be used as long as the liquid generates a
surface tension. The larger the surface tension of the liquid, the
larger the force applied between the membrane and the electrode for
electrolysis or the metal plate and the electrode for electrolysis.
Thus, a liquid having a larger surface tension is preferred.
Examples of the liquid include the following (the numerical value
in the parentheses is the surface tension of the liquid):
[0277] hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00
mN/m), ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and
water (72.76 mN/m).
[0278] A liquid having a large surface tension allows the membrane
and the electrode for electrolysis or the metal porous plate or
metal plate (feed conductor) and the electrode for electrolysis to
be integrated (to be a laminate) to thereby facilitate renewing of
the electrode. The liquid between the membrane and the electrode
for electrolysis or the metal porous plate or metal plate (feed
conductor) and the electrode for electrolysis may be present in an
amount such that the both adhere to each other by the surface
tension. As a result, after the laminate is placed in an
electrolytic cell, the liquid, if mixed into the electrolyte
solution, does not affect electrolysis itself due to the small
amount of the liquid.
[0279] From a practical viewpoint, a liquid having a surface
tension of 20 mN/m to 80 mN/m, such as ethanol, ethylene glycol,
and water, is preferably used as the liquid. Particularly preferred
is water or an alkaline aqueous solution prepared by dissolving
caustic soda, potassium hydroxide, lithium hydroxide, sodium
hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate,
potassium carbonate, or the like in water. Alternatively, the
surface tension can be adjusted by allowing these liquids to
contain a surfactant. When a surfactant is contained, the adhesion
between the membrane and the electrode for electrolysis or the
metal plate and the electrode for electrolysis varies to enable the
handling property to be adjusted. The surfactant is not
particularly limited, and both ionic surfactants and nonionic
surfactants may be used.
[0280] The electrode for electrolysis of the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is not particularly limited, but is
preferably 300 .mu.m or less, more preferably 205 .mu.m or less,
further preferably 155 .mu.m or less, further preferably 135 .mu.m
or less, further more preferably 125 .mu.m or less, still more
preferably 120 .mu.m or less, even still more preferably 100 .mu.m
or less from the viewpoint of enabling a good handling property to
be provided, having a good adhesive force to a membrane such as an
ion exchange membrane and a microporous membrane, a degraded
electrode, and a feed conductor having no catalyst coating, being
capable of being suitably rolled in a roll and satisfactorily
folded, and facilitating handling in a large size (e.g., a size of
1.5 m.times.2.5 m), and further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[0281] The proportion measured by the following method (2) of the
electrode for electrolysis of the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode, and a feed conductor having no
catalyst coating, and further preferably 95% or more from the
viewpoint of further facilitating handling in a large size (e.g., a
size of 1.5 m.times.2.5 m). The upper limit value is 100%.
[Method (2)]
[0282] An ion exchange membrane (170 mm square) and a sample of
electrode for electrolysis (130 mm square) are laminated in this
order. The laminate is placed on a curved surface of a polyethylene
pipe (outer diameter: 280 mm) such that the sample of electrode for
electrolysis in this laminate is positioned outside under
conditions of a temperature of 23.+-.2.degree. C. and a relative
humidity of 30.+-.5%, the laminate and the pipe are sufficiently
immersed in pure water, excess water deposited on a surface of the
laminate and the pipe is removed, and one minute after this
removal, then the proportion (%) of an area of a portion in which
the ion exchange membrane (170 mm square) is in close contact with
the sample of electrode for electrolysis is measured.
[0283] The proportion measured by the following method (3) of the
electrode for electrolysis of the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode, and a feed conductor having no
catalyst coating and being capable of being suitably rolled in a
roll and satisfactorily folded, and is further preferably 90% or
more from the viewpoint of further facilitating handling in a large
size (e.g., a size of 1.5 m.times.2.5 m). The upper limit value is
100%.
[Method (3)]
[0284] An ion exchange membrane (170 mm square) and a sample of
electrode for electrolysis (130 mm square) are laminated in this
order. The laminate is placed on a curved surface of a polyethylene
pipe (outer diameter: 145 mm) such that the sample of electrode for
electrolysis in this laminate is positioned outside under
conditions of a temperature of 23.+-.2.degree. C. and a relative
humidity of 30.+-.5%, the laminate and the pipe are sufficiently
immersed in pure water, excess water deposited on a surface of the
laminate and the pipe is removed, and one minute after this
removal, then the proportion (%) of an area of a portion in which
the ion exchange membrane (170 mm square) is in close contact with
the sample of electrode for electrolysis is measured.
[0285] The electrode for electrolysis of the present embodiment
preferably has, but is not particularly limited to, a porous
structure and an opening ratio or void ratio of 5 to 90% or less
from the viewpoint of enabling a good handling property to be
provided, having a good adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
and a feed conductor having no catalyst coating, and preventing
accumulation of gas to be generated during electrolysis. The
opening ratio is more preferably 10 to 80% or less, further
preferably 20 to 75%.
[0286] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V was calculated from the values of the gauge thickness,
width, and length of the electrode, and further, a weight W was
measured to thereby calculate an opening ratio A by the following
formula.
A=(1=(W/(V.times..rho.)).times.100
[0287] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio is appropriately
adjusted by changing the area of metal to be perforated per unit
area in the case of perforated metal, changing the values of the SW
(short diameter), LW (long diameter), and feed in the case of
expanded metal, changing the line diameter of metal fiber and mesh
number in the case of mesh, changing the pattern of a photoresist
to be used in the case of electroforming, changing the metal fiber
diameter and fiber density in the case of nonwoven fabric, changing
the mold for forming voids in the case of foamed metal, or the
like.
[0288] The value obtained by measurement by the following method
(A) of the electrode for electrolysis in the present embodiment is
preferably 40 mm or less, more preferably 29 mm or less, further
preferably 10 mm or less, further more preferably 6.5 mm or less
from the viewpoint of the handling property. The specific measuring
method is as described in Examples.
[Method (A)]
[0289] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, a sample obtained by laminating
the ion exchange membrane and the electrode for electrolysis is
wound around and fixed onto a curved surface of a core material
being made of polyvinyl chloride and having an outer diameter .PHI.
of 32 mm, and left to stand for 6 hours; thereafter, when the
electrode for electrolysis is separated from the sample and placed
on a flat plate, heights in a vertical direction at both edges of
the electrode for electrolysis L.sub.1 and L.sub.2 are measured,
and an average value thereof is used as a measurement value.
[0290] In the electrode for electrolysis in the present embodiment,
the ventilation resistance is preferably 24 kPas/m or less when the
electrode for electrolysis has a size of 50 mm.times.50 mm, the
ventilation resistance being measured under the conditions of the
temperature of 24.degree. C., the relative humidity of 32%, a
piston speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s (hereinbelow, also referred to as "measurement
condition 1") (hereinbelow, also referred to as "ventilation
resistance 1"). A larger ventilation resistance means that air is
unlikely to flow and refers to a state of a high density. In this
state, the product from electrolysis remains in the electrode and
the reaction substrate is more unlikely to diffuse inside the
electrode, and thus, the electrolytic performance (such as voltage)
tends to deteriorate. The concentration on the membrane surface
tends to increase. Specifically, the caustic concentration
increases on the cathode surface, and the supply of brine tends to
decrease on the anode surface. As a result, the product accumulates
at a high concentration on the interface at which the membrane is
in contact with the electrode. This accumulation leads to damage of
the membrane and tends to also lead to increase in the voltage and
image of the membrane on the cathode surface and damage of the
membrane on the anode surface. In the present embodiment, in order
to prevent these defects, the ventilation resistance is preferably
set at 24 kPas/m or less. From a similar viewpoint as above, the
ventilation resistance is more preferably less than 0.19 kPas/m,
further preferably 0.15 kPas/m or less, further more preferably
0.07 kPas/m or less.
[0291] In the present embodiment, when the ventilation resistance
is larger than a certain value, NaOH generated in the electrode
tends to accumulate on the interface between the electrode and the
membrane to result in a high concentration in the case of the
cathode, and the supply of brine tends to decrease to cause the
brine concentration to be lower in the case of the anode. In order
to prevent damage to the membrane that may be caused by such
accumulation, the ventilation resistance is preferably less than
0.19 kPas/m, more preferably 0.15 kPas/m or less, further
preferably 0.07 kPas/m or less.
[0292] In contrast, when the ventilation resistance is low, the
area of the electrode is reduced and the electrolysis area is
reduced. Thus, the electrolytic performance (such as voltage) tends
to deteriorate. When the ventilation resistance is zero, the feed
conductor functions as the electrode because no electrode for
electrolysis is provided, and the electrolytic performance (such as
voltage) tends to markedly deteriorate. From this viewpoint, a
preferable lower limit value identified as the ventilation
resistance 1 is not particularly limited, but is preferably more
than 0 kPas/m, more preferably 0.0001 kPas/m or more, further
preferably 0.001 kPas/m or more.
[0293] When the ventilation resistance 1 is 0.07 kPas/m or less, a
sufficient measurement accuracy may not be achieved because of the
measurement method therefor. From this viewpoint, it is also
possible to evaluate an electrode for electrolysis having a
ventilation resistance 1 of 0.07 kPas/m or less by means of a
ventilation resistance (hereinbelow, also referred to as
"ventilation resistance 2") obtained by the following measurement
method (hereinbelow, also referred to as "measurement condition
2"). That is, the ventilation resistance 2 is a ventilation
resistance measured, when the electrode for electrolysis has a size
of 50 mm.times.50 mm, under conditions of the temperature of
24.degree. C., the relative humidity of 32%, a piston speed of
cm/s, and a ventilation volume of 4 cc/cm.sup.2/s.
[0294] The specific methods for measuring the ventilation
resistances 1 and 2 are described in Examples.
[0295] The ventilation resistances 1 and 2 can be within the range
described above by appropriately adjusting an opening ratio,
thickness of the electrode, and the like, for example. More
specifically, for example, when the thickness is constant, a higher
opening ratio tends to lead to smaller ventilation resistances 1
and 2, and a lower opening ratio tends to lead to larger
ventilation resistances 1 and 2.
[0296] Hereinbelow, one aspect of the electrode for electrolysis of
the present embodiment will be described.
[0297] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[0298] As shown in FIG. 1, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode. One first layer 20 may be laminated
only on one surface of the substrate for electrode for electrolysis
10.
[0299] Also shown in FIG. 1, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[0300] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, and further, valve
metals including titanium can be used, although not limited
thereto. At least one element selected from nickel (Ni) and
titanium (Ti) is preferably included. That is, the substrate for
electrode for electrolysis preferably includes at least one element
selected from nickel (Ni) and titanium (Ti).
[0301] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[0302] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[0303] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
eletroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[0304] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, foamed metal, metal nonwoven
fabric, expanded metal, perforated metal, metal porous foil, and
the like can be used, although not limited thereto.
[0305] Examples of the substrate for electrode for electrolysis 10
include a metal foil, a wire mesh, a metal nonwoven fabric, a
perforated metal, an expanded metal, or a foamed metal.
[0306] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil preferably further subjected
to a plating treatment by use of the same element as the base
material thereof, as the post-treatment, to thereby form asperities
on the surface thereof.
[0307] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[0308] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina grid, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
It is preferable to give a plating treatment by use of the same
element as the substrate to increase the surface area.
[0309] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 5
.mu.m.
[0310] Next, a case where the electrode for electrolysis of the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[0311] In FIG. 1, a first layer 20 as a catalyst layer contains at
least one of ruthenium oxides, iridium oxides, and titanium oxides.
Examples of the ruthenium oxide include RuO.sub.2. Examples of the
iridium oxide include IrO.sub.2. Examples of the titanium oxide
include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[0312] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0313] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol of the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0314] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[0315] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[0316] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[0317] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[0318] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[0319] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness preferably 0.05 to 3 .mu.m.
[0320] Next, a case where the electrode for electrolysis of the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[0321] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Ph, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[0322] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[0323] As the platinum group metal, platinum is preferably
contained.
[0324] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[0325] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[0326] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[0327] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[0328] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[0329] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[0330] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[0331] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[0332] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[0333] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[0334] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[0335] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[0336] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The durability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[0337] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[0338] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals. The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[0339] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness is more preferably 0.1 .mu.m to 10 .mu.m. The
thickness is further preferably 0.2 .mu.m to 8 .mu.m.
[0340] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis was
measured in the same manner as the thickness of the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
(Method for Producing Electrode for Electrolysis)
[0341] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[0342] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking of a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. Among these, the pyrolysis method, plating method, and
ion plating method are preferable because the catalyst layer can be
formed while deformation of the substrate for electrode for
electrolysis is prevented. When the viewpoint of productivity is
added, the plating method and pyrolysis method are further
preferable. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, in the pyrolysis method, a catalyst
layer is formed on the substrate for electrode for electrolysis by
an application step of applying a coating liquid containing a
catalyst, a drying step of drying the coating liquid, and a
pyrolysis step of performing pyrolysis. Pyrolysis herein means that
a metal salt which is to be a precursor is decomposed by heating
into a metal or metal oxide and a gaseous substance. The
decomposition product depends on the metal species to be used, type
of the salt, and the atmosphere under which pyrolysis is performed,
and many metals tend to form oxides in an oxidizing atmosphere. In
an industrial process of producing an electrode for electrolysis,
pyrolysis is usually performed in air, and a metal oxide or a metal
hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[0343] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating is substantially
equivalent to that of the first layer 20.
[0344] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[0345] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first. coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0346] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable, 5 to 20 minutes is more preferable.
[0347] The cycle of application, drying and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer of Anode)
[0348] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[0349] The first layer 20 is obtained by applying a solution in
which metal salts of various combination are dissolved (first
coating liquid) onto the substrate for electrode for electrolysis
and then pyrolyzing (baking) the coating liquid in the presence of
oxygen. The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[0350] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as ethanol and butanol can be used. As the
solvent, water or a mixed solvent of water and an alcohol is
preferable. The total metal concentration in the first coating
liquid in which the metal salts are dissolved is, but is not
particularly limited to, preferably in the range of 10 to 150 g/L
in association with the thickness of the coating film to be formed
by a single coating.
[0351] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0352] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[0353] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further baked for a long period as required, heating in the
range of 350.degree. C. to 650.degree. C. for one minute to 90
minutes can further improve the stability of the first layer
20.
(Formation of Intermediate Layer)
[0354] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, with no solution applied thereon, in the range of
300.degree. C. to 580.degree. C. for one minute to 60 minutes.
(Formation of First Layer of Cathode by Plating)
[0355] The first layer 20 can be formed also by ion plating.
[0356] An example includes a method in which the substrate is fixed
in a chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[0357] The first layer 20 can be formed also by a plating
method.
[0358] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[0359] The first layer 20 can be formed also by thermal
spraying.
[0360] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[0361] The electrode for electrolysis of the present embodiment can
be integrated with a membrane such as an ion exchange membrane and
a macroporous membrane and used. Thus, the electrode can be used as
a membrane-integrated electrode. Then, the substituting work for
the cathode and anode on renewing the electrode is eliminated, and
the work efficiency is markedly improved.
[0362] The electrode for electrolysis of the present embodiment
forms a laminate with a membrane such as an ion exchange membrane
and a microporous membrane to be an integrated piece of the
membrane and the electrode, and then can make the electrolytic
performance comparable to or higher than those of a new electrode.
The membrane is not particularly limited as long as the membrane
can be laminated with the electrode, and will be described in
detail below.
[Ion Exchange Membrane]
[0363] The ion exchange membrane has a membrane body containing a
hydrocarbon polymer or fluorine-containing polymer having an ion
exchange group and a coating layer provided on at least one surface
of the membrane body. The coating layer contains inorganic material
particles and a binder, and the specific surface area of the
coating layer is 0.1 to 10 m.sup.2/g. In the ion exchange membrane
having such a structure, the influence of gas generated during
electrolysis on electrolytic performance is small, and stable
electrolytic performance can be exhibited.
[0364] The ion exchange membrane described above includes either
one of a sulfonic acid layer having an ion exchange group derived
from a sulfo group (a group represented by --SO.sub.3.sup.-,
hereinbelow also referred to as a "sulfonic acid group") or a
carboxylic acid layer having an ion exchange group derived from a
carboxyl group (a group represented by --CO.sub.2.sup.-,
hereinbelow also referred to as a "carboxylic acid group"). From
the viewpoint of strength and dimension stability, reinforcement
core materials are preferably further included.
[0365] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[0366] FIG. 2 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-containing polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[0367] In the ion exchange membrane 1, the membrane body 10
includes a sulfonic acid layer 3 and a carboxylic acid layer 2, and
reinforcement core materials 4 enhance the strength and dimension
stability. The ion exchange membrane 1, including the sulfonic acid
layer 3 and the carboxylic acid layer 2, is suitably used as an ion
exchange membrane.
[0368] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 2.
(Membrane Body)
[0369] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[0370] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[0371] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[0372] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[0373] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[0374] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.s--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[0375] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[0376] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time of hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[0377] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[0378]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[0379]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[0380]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[0381]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[0382] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[0383] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[0384] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[0385] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[0386]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[0387]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[0388] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[0389]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[0390]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[0391] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[0392] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[0393] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[0394] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[0395] In the membrane body 10 of the ion exchange membrane 1, a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[0396] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer 2 is
located on the cathode side of the electrolyzer.
[0397] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[0398] The carboxylic acid layer 2 preferably high anion exclusion
properties even if it has a small membrane thickness. The anion
exclusion properties here refer to the property of trying to hinder
intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[0399] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[0400] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[0401] The ion exchange membrane has a coating layer on at least
one surface of the membrane body. As shown in FIG. 2, in the ion
exchange membrane 1, coating layers 11a and 11b are formed on both
the surfaces of the membrane body 10.
[0402] The coating layers contain inorganic material particles and
a binder.
[0403] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[0404] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[0405] Here, the average particle size can be measured by a
particle size analyzer ("SALD2200", SHIMADZU CORPORATION).
[0406] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[0407] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides of Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durability, zirconium
oxide particle is more preferable.
[0408] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[0409] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurities such as iron attached to the
surface of the inorganic material particles.
[0410] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[0411] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder of the coating layer.
[0412] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[0413] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[0414] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[0415] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[0416] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contraction of the ion
exchange membrane can be controlled in the desired range. Such an
ion exchange membrane does not expand or contract more than
necessary during electrolysis and the like and can maintain
excellent dimensional stability for a long term.
[0417] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[0418] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, alkalis, etc., and a
fiber comprising a fluorine-containing polymer is preferable
because long-term heat resistance and chemical resistance are
required.
[0419] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[0420] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) is preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[0421] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[0422] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[0423] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[0424] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[0425] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[0426] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion change
membrane.
[0427] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area of a surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[0428] FIG. 3 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 3, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[0429] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[0430] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[0431] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[0432] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[0433] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[0434] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[0435] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[0436] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[0437] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[0438] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[0439] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[0440] Step (3): the step of forming into a film the above
flourine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[0441] Step (4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[0442] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[0443] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[0444] Hereinafter, each of the steps will be described in
detail.
[0445] Step (1): Step of Producing Fluorine-Containing Polymer
[0446] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[0447] Step (2): Step of Producing Reinforcing Materials
[0448] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[0449] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and comprising polyvinyl alcohol and
the like are also preferred.
[0450] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[0451] Step (3): Step of Film Formation
[0452] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[0453] Examples of the film forming method include the
following:
[0454] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[0455] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[0456] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[0457] Step (4): Step of Obtaining Membrane Body
[0458] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[0459] Preferable examples of the method for forming a membrane
body include (i) a method in which a fluorine-containing polymer
having a carboxylic acid group precursor (e.g., carboxylate
functional group) (hereinafter, a layer comprising the same is
referred to as the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[0460] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[0461] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property of sufficiently retaining
the mechanical strength of the ion exchange membrane.
[0462] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration or the
membrane body and physical properties, and the like.
[0463] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[0464] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[0465] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[0466] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[0467] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that projections, on the surface side
composed of the sulfonic acid layer. As a method for forming such
projections, which is not particularly limited, a known method also
can be employed including forming projections on a resin surface. A
specific example of the method is a method of embossing the surface
of the membrane body. For example, the above projections can be
formed by using release paper embossed in advance when the
composite film mentioned above, reinforcing material, and the like
are integrated. In the case where projections are formed by
embossing, the height and arrangement density of the projections
can be controlled by controlling the emboss shape to be transferred
(shape of the release paper).
[0468] (5) Hydrolysis Step
[0469] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[0470] In the step (5), it is also possible to form dissolution
holes in the membrane body dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[0471] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[0472] The step (5) can be performed by immersing the membrane body
obtained the step (4) in a hydrolysis solution containing acid or
alkali. An example of the hydrolysis solution that can be used is a
mixed solution containing KOH and dimethyl sulfoxide (DSMO).
[0473] The mixed solution preferably contains KOH of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[0474] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[0475] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[0476] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 4(a) and
(b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[0477] FIGS. 4(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[0478] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[0479] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[0480] FIG. 4(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
[0481] (6) Application Step
[0482] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[0483] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counter the ion exchange group by
H+ (e.g., a fluorine-containing polymer having a carboxyl group or
sulfo group). Thereby, the polymer is more likely to dissolve in
water or ethanol mentioned below, which is preferable.
[0484] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[0485] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[0486] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[0487] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating
thereby provide an ion exchange membrane.
[Microporous Membrane]
[0488] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[0489] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example, and is preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[0490] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[0491] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[0492] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[Laminate]
[0493] The laminate of the present embodiment comprises the
electrode for electrolysis of the present embodiment, and a
membrane or feed conductor in contact with the electrode for
electrolysis. The laminate of the present embodiment, as configured
as described above, can improve the work efficiency during
electrode renewing in an electrolyzer and further, can exhibit
excellent electrolytic performance also after renewing.
[0494] That is, according to the laminate of the present
embodiment, on renewing the electrode, the electrode can be renewed
by a work as simple as renewing the membrane, without a complicated
work such as stripping off the electrode fixed on the electrolytic
cell, and thus, the work efficiency is markedly improved.
[0495] Further, according to the laminate or the present invention,
it is possible to maintain the electrolytic performance comparable
to those of a new electrode or improve the electrolytic
performance. Even in the case where only a feed conductor is placed
in a new electrolytic cell (i.e., an electrode including no
catalyst layer placed), only attaching the electrode for
electrolysis of the present embodiment to the feed conductor
enables the electrode to function. Thus, it may be also possible to
markedly reduce or eliminate catalyst coating.
[0496] The laminate of the present embodiment can be stored or
transported to customers in a state where the laminate is wound
around a vinyl chloride pipe or the like (in a rolled state or the
like), making handling markedly easier.
[0497] As the feed conductor of the present embodiment, various
substrates mentioned below such as a degraded electrode (i.e., the
existing electrode) and an electrode having no catalyst coating can
be employed.
[0498] In the laminate of the present embodiment, the force applied
per unit massunit area of the electrode for electrolysis on the
membrane or feed conductor is preferably 0.08 N/(mgcm.sup.2) or
more, more preferably 0.1 N/(mgcm.sup.2) or more, further
preferably 0.14 N/(mgcm.sup.2) or more, and further more
preferably, from the viewpoint of further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m), is 0.2
N/(mgcm.sup.2) or more. The upper limit value is not particularly
limited, but is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less. The upper
limit value is ever still more preferably 1.1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[Wound Body]
[0499] The wound body of the present embodiment includes the
electrode for electrolysis of the present embodiment or the
laminate of the present embodiment. That is, the wound body of the
present embodiment is obtained by winding the electrode for
electrolysis of the present embodiment or the laminate of the
present embodiment. Downsizing the electrode for electrolysis of
the present embodiment or the laminate of the present embodiment by
winding, as the wound body of the present embodiment, can further
improve the handling property.
[Electrolyzer]
[0500] The electrolyzer of the present embodiment includes the
electrode for electrolysis of the present embodiment. Hereinafter,
the case of performing common salt electrolysis by using an ion
exchange membrane as the membrane is taken as an example, and one
embodiment of the electrolyzer will be described in detail.
[Electrolytic Cell]
[0501] FIG. 5 illustrates a cross-sectional view of an electrolytic
cell 1.
[0502] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell 1 has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 9, and the cathode 21 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer may be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support 24, the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[0503] FIG. 6 illustrates a cross-sectional view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
7 shows an electrolyzer 4. FIG. 8 shows a step of assembling the
electrolyzer 4. As shown in FIG. 6, an electrolytic cell 1, a
cation exchange membrane 2, and an electrolytic cell 1 are arranged
in series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 among
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 7, the
electrolyzer 4 is composed of a plurality of electrolytic cells 1
connected in series via the ion exchange membrane 2. That is, the
electrolyzer 4 is a bipolar electrolyzer comprising the plurality
of electrolytic cells 1 arranged in series and ion exchange
membranes 2 each arranged between adjacent electrolytic cells 1. As
shown in FIG. 8, the electrolyzer 4 is assembled by arranging the
plurality of electrolytic cells 1 in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[0504] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[0505] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[0506] The anode chamber 10 has the anode 11 or anode feed
conductor 11. When the electrode for electrolysis of the present
embodiment is inserted to the anode side, 11 serves as the anode
feed conductor. When the electrode for electrolysis of the present
embodiment is not inserted to the anode side, 11 serves as the
anode. The anode chamber 10 has an anode-side electrolyte solution
supply unit that supplies an electrolyte solution to the anode
chamber 10, a baffle plate that is arranged above the anode-side
electrolyte solution supply unit so as to be substantially parallel
or oblique to the partition wall 30, and an anode-side gas liquid
separation unit arranged above the baffle plate to separate gas
from the electrolyte solution including the gas mixed.
(Anode)
[0507] When the electrode for electrolysis of the present
embodiment is not inserted to the anode side, the anode 11 is
provided in the frame of the anode chamber 10. As the anode 11, a
metal electrode such as so-called DSA(R) can be used. DSA is an
electrode including a titanium substrate of which surface is
covered with an oxide comprising ruthenium, iridium, and titanium
as component.
[0508] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[0509] When the electrode for electrolysis of the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having a thinner catalyst coating can be also
used. Further, a used anode can be also used.
[0510] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[0511] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[0512] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 5, and below means the lower direction
in the electrolytic cell 1 in FIG. 5.
[0513] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 of the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle Plate)
[0514] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[0515] Although not shown in FIG. 5, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[0516] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[0517] In the cathode chamber 20, when the electrode for
electrolysis of the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis of the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[0518] When the electrode for electrolysis of the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20. The cathode 21
preferably has a nickel substrate and a catalyst layer that covers
the nickel substrate. Examples of the components of the catalyst
layer on the nickel substrate include metals such as Pu, C, Si, P,
S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. The cathode 21 may
be subjected to a reduction treatment, as required. As the
substrate of the cathode 21, nickel, nickel alloys, and
nickel-plated iron or stainless may be used.
[0519] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[0520] When the electrode for electrolysis of the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. As the substrate
of the cathode feed conductor 21, nickel, nickel alloys, and
nickel-plated iron or stainless may be used.
[0521] As the feed conductor 21, nickel, nickel alloys, and
nickel-plated iron or stainless, having no catalyst coating may be
used.
[0522] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current absorbing Layer)
[0523] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[0524] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[0525] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[0526] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electrolytic cells 1 connected in
series. Lowering of the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis according to the present
invention is placed in the electrolytic cell.
[0527] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning, mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[0528] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[0529] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantial perpendicular to the partition wall 30 and
the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[0530] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane 2 (see FIGS. 5 and 6).
These gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[0531] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced gas and be
usable for long period. Thus, in respect of chemical resistance and
hardness, vulcanized products and peroxide-crosslinked products of
ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 6), each
electrolytic cell 1 onto which the gasket is attached should be
tightened via ion exchange membrane 2. This tightening can prevent
the electrolyte solution, alkali metal hydroxide, chlorine gas,
hydrogen gas, and the like generated from electrolysis from leaking
out of the electrolytic cells 1.
(Ion Exchange Membrane 2)
[0532] The ion exchange membrane 2 is as described in the section
of the ion exchange membrane described above.
(Water Electrolysis)
[0533] The electrolyzer of the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
Second Embodiment
[0534] Here, a second embodiment of the present invention will be
described in detail with reference to FIGS. 22 to 42.
[Laminate]
[0535] A laminate of the second embodiment (hereinafter, in the
section of <Second embodiment>, simply referred to as "the
present embodiment") comprises an electrode for electrolysis and a
membrane or feed conductor in contact with the electrode for
electrolysis, wherein a force applied per unit massunit area of the
electrode for electrolysis on the membrane or feed conductor is
less than 1.5 N/mgcm.sup.2. The laminate of the present embodiment,
as configured as described above, can improve the work efficiency
during electrode renewing in an electrolyzer and further, can
exhibit excellent electrolytic performance also after renewing.
[0536] That is, according to the laminate of the present
embodiment, on renewing the electrode, the electrode can be renewed
by a work as simple as renewing the membrane, without a complicated
work such as stripping off the existing electrode fixed on the
electrolytic cell, and thus, the work efficiency is markedly
improved.
[0537] Further, according to the laminate of the present invention,
it is possible to maintain or improve the electrolytic performance
of a new electrode. Thus, the electrode fixed on a conventional new
electrolytic cell and serving as an anode and/or a cathode is only
required to serve as a feed conductor. Thus, it may be also
possible to markedly reduce or eliminate catalyst coating.
[0538] The laminate of the present embodiment can be stored or
transported to customers in a state where the laminate is wound
around a vinyl chloride pipe or the like (in a rolled state or the
like), making handling markedly easier.
[0539] As the feed conductor of the present embodiment, various
substrates mentioned below such as a degraded electrode (i.e., the
existing electrode) and an electrode having no catalyst coating can
be employed.
[0540] The laminate of the present embodiment may have partially a
fixed portion as long as the laminate has the configuration
described above. That is, in the case where the laminate of the
present embodiment has a fixed portion, a portion not having the
fixing is subjected to measurement, and the resulting force applied
per unit massunit area of the electrode for electrolysis should be
less than 1.5 N/mgcm.sup.2.
[Electrode for Electrolysis]
[0541] The electrode for electrolysis of the present embodiment has
a force applied per unit massunit area of less than 1.5
N/mgcm.sup.2, preferably 1.2 N/mgcm.sup.2 or less, more preferably
1.20 N/mgcm.sup.2 or less from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a feed conductor (a degraded electrode and an electrode
having no catalyst coating), and the like. The force is further
preferably 1.1 N/mgcm.sup.2 or less, further preferably 1.10
N/mgcm.sup.2 or less, still more preferably 1.0 N/mgcm.sup.2 or
less, even still more preferably 1.00 N/mgcm.sup.2 or less.
[0542] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0.2 N/(mgcm.sup.2) or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[0543] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[0544] The mass per unit area is preferably 48 mg/cm.sup.2 or less,
more preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and economy, and furthermore is preferably 15 mg/cm.sup.2 or less
from the comprehensive viewpoint including handling property,
adhesion, and economy. The lower limit value is not particularly
limited but is of the order of 1 mg/cm.sup.2, for example.
[0545] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[0546] The force applied can be measured by methods (i) or (ii)
described below, which are as described in Examples, specifically.
As for the force applied, the value obtained by the measurement of
the method (i) (also referred to as "the force applied (1)") and
the value obtained by the measurement of the method (ii) (also
referred to as "the force applied (2)") may be the same or
different, and either of the values is less than 1.5
N/mgcm.sup.2.
[Method (i)]
[0547] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. The arithmetic average surface roughness
(Pa) of the nickel plate after the blast treatment is 0.5 to 0.8
.mu.m. The specific method for calculating the arithmetic average
surface roughness (Ra) is as described in Examples.
[0548] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode in
this sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[0549] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[0550] The force applied per unit massunit area (1) obtained by the
method (i) is less than 1.5 N/mgcm.sup.2, preferably 1.2
N/mgcm.sup.2 or less, more preferably 1.20 N/mgcm.sup.2 or less,
further preferably 1.1 N/mgcm.sup.2 or less, further more
preferably 1.10 N/mgcm.sup.2 of less, still more preferably 1.0
N/mgcm.sup.2 of less, even still more preferably 1.00 N/mgcm.sup.2
or less from the viewpoint of enabling a good handling property to
be provided and having a good adhesive force to a membrane such as
an ion exchange membrane and a microporous membrane, a degraded
electrode, and a feed conductor having no catalyst coating. The
force is preferably more than 0.005 N/(mgcm.sup.2), more preferably
0.08 N/(mgcm.sup.2) or more, further preferably 0.1 N/(mgcm.sup.2)
or more from the viewpoint of further improving the electrolytic
performance, and furthermore, is further more preferably 0.14
N/(mgcm.sup.2), still more preferably 0.2 N/(mgcm.sup.2) or more
from the viewpoint of further facilitating handling in a large size
(e.g., a size of 1.5 m.times.2.5 m).
[0551] When the electrode for electrolysis of the present
embodiment satisfies the force applied (1), the electrode can be
integrated with a membrane such as an ion exchange membrane and a
microporous membrane or a feed conductor, for example, and used
(i.e., as a laminate). Thus, on renewing the electrode, the
substituting work for the cathode and anode fixed on the
electrolytic cell by a method such as welding is eliminated, and
the work efficiency is markedly improved. Additionally, by use of
the electrode for electrolysis of the present embodiment as a
laminate integrated with the ion exchange membrane, microporous
membrane, or feed conductor, it is possible to make the
electrolytic performance comparable to or higher than those of a
new electrode.
[0552] On shipping a new electrolytic cell, an electrode fixed on
an electrolytic cell has been subjected to catalyst coating
conventionally. Since only combination of an electrode having no
catalyst coating with the electrode for electrolysis of the present
embodiment can allow the electrode to function as an electrode, it
is possible to markedly reduce or eliminate the production step and
the amount of the catalyst for catalyst coating. A conventional
electrode of which catalyst coating is markedly reduced or
eliminated can be electrically connected to the electrode for
electrolysis of the present embodiment and allowed to serve as a
feed conductor for passage of an electric current.
[Method (ii)]
[0553] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[0554] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[0555] The force applied per unit massunit area (2) obtained by the
method (ii) is less than 1.5 N/mgcm.sup.2, preferably 1.2
N/mgcm.sup.2 or less, more preferably 1.20 N/mgcm.sup.2 or less,
further preferably 1.1 N/mgcm.sup.2 or less, further more
preferably 1.10 N/mgcm.sup.2 or less, still more preferably 1.0
N/mgcm.sup.2 or less, even still more preferably 1.00 N/mgcm.sup.2
or less from the viewpoint of enabling a good handling property to
be provided and having a good adhesive force to a membrane such as
an ion exchange membrane and a microporous membrane, a degraded
electrode, and a feed conductor having no catalyst coating. The
force is preferably more than 0.005 N/(mgcm.sup.2), more preferably
0.08 N/(mgcm.sup.2) or more, further preferably 0.1 N/(mgcm.sup.2)
or more from the viewpoint of further improving the electrolytic
performance, and is further more preferably 0.14 N/(mgcm.sup.2) or
more from the viewpoint of further facilitating handling in a large
size (e.g., a size of 1.5 m.times.2.5 m).
[0556] The electrode for electrolysis of the present embodiment, if
satisfies the force applied (2), can be stored or transported to
customers in a state where the electrode is wound around a vinyl
chloride pipe or the like (in a rolled state or the like), making
handling markedly easier. By attaching the electrode for
electrolysis of the present embodiment to a degraded existing
electrode to provide a laminate, it is possible to make the
electrolytic performance comparable to or higher than those of a
new electrode.
[0557] From the viewpoint that the electrode for electrolysis of
the present embodiment, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m less,
further still more preferably 135 .mu.m or less. A thickness of 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
[0558] The electrode for electrolysis of the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 120 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having no catalyst coating, being capable of being
suitably rolled in a roll and satisfactorily folded, and
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[0559] In the present embodiment, a liquid is preferably interposed
between the membrane such as an ion exchange membrane and a
microporous membrane and the electrode, or the metal porous plate
or metal plate (i.e., feed conductor) such as a degraded existing
electrode and electrode having no catalyst coating and the
electrode for electrolysis. As the liquid, any liquid, such as
water and organic solvents, can be used as long as the liquid
generates a surface tension. The larger the surface tension of the
liquid, the larger the force applied between the membrane and the
electrode for electrolysis or the metal porous plate or metal plate
and the electrode for electrolysis. Thus, a liquid having a larger
surface tension is preferred. Examples of the liquid include the
following (the numerical value in the parentheses is the surface
tension of the liquid at 20.degree. C.)
[0560] hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00
mN/m), ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and
water (72.76 mN/m).
[0561] A liquid having a large surface tension allows the membrane
and the electrode for electrolysis or the metal porous plate or
metal plate (feed conductor) and the electrode for electrolysis to
be integrated (to be a laminate) to thereby facilitate renewing of
the electrode. The liquid between the membrane and the electrode
for electrolysis or the metal porous plate or metal plate (feed
conductor) and the electrode for electrolysis may be present in an
amount such that the both adhere to each other by the surface
tension. As a result, after the laminate is placed in an
electrolytic cell, the liquid, if mixed into the electrolyte
solution, does not affect electrolysis itself due to the small
amount of the liquid.
[0562] From a practical viewpoint, a liquid having a surface
tension of 24 mN/m to 80 mN/m, such as ethanol, ethylene glycol,
and water, is preferably used as the liquid. Particularly preferred
is water or an alkaline aqueous solution prepared by dissolving
caustic soda, potassium hydroxide, lithium hydroxide, sodium
hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate,
potassium carbonate, or the like in water. Alternatively, the
surface tension can be adjusted by allowing these liquids to
contain a surfactant. When a surfactant is contained, the adhesion
between the membrane and the electrode for electrolysis or the
metal porous plate or metal plate (feed conductor) and the
electrode for electrolysis varies to enable the handling property
to be adjusted. The surfactant is not particularly limited, and
both ionic surfactants and nonionic surfactants may be used.
[0563] The proportion measured by the following method (2) of the
electrode for electrolysis of the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint or further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2)]
[0564] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[0565] The proportion measured by the following method (3) of the
electrode for electrolysis of the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[0566] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[0567] The electrode for electrolysis of the present embodiment
preferably has a porous structure and an opening ratio or void
ratio of 5 to 90% or less from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and preventing
accumulation of gas to be generated during electrolysis, although
not particularly limited. The opening ratio is more preferably 10
to 80% or less, further preferably 20 to 75%.
[0568] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V was calculated from the values of the gauge thickness,
width, and length of the electrode, and further, a weight W was
measured to thereby calculate an opening ratio A by the following
formula.
A=(1-(W/(V.times..rho.)).times.100
[0569] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio is appropriately
adjusted by changing the area of metal to be perforated per unit
area in the case of perforated metal, changing the values of the SW
(short diameter), LW (long diameter), and feed in the case of
expanded metal, changing the line diameter of metal fiber and mesh
number in the case of mesh, changing the pattern of a photoresist
to be used in the case of electroforming, changing the metal fiber
diameter and fiber density in the case of nonwoven fabric, changing
the mold for forming voids in the case of foamed metal, or the
like.
[0570] The value obtained by measurement by the following method
(A) of the electrode for electrolysis in the present embodiment is
preferably 40 mm or less, more preferably 29 mm or less, further
preferably 10 mm or less, further more preferably 6.5 mm or less
from the viewpoint of the handling property. The specific measuring
method is as described in Examples.
[Method (A)]
[0571] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, a sample obtained by laminating
the ion exchange membrane and the electrode for electrolysis is
wound around and fixed onto a curved surface of a core material
being made of polyvinyl chloride and having an outer diameter .PHI.
of 32 mm, and left to stand for 6 hours; thereafter, when the
electrode for electrolysis is separated from the sample and placed
on a flat plate, heights in a vertical direction at both edges of
the electrode for electrolysis L.sub.1 and L.sub.2 are measured,
and an average value thereof is used as a measurement value.
[0572] In the electrode for electrolysis in the present embodiment,
the ventilation resistance is preferably 24 kPas/m or less when the
electrode for electrolysis has a size of 50 mm.times.50 mm, the
ventilation resistance being measured under conditions of the
temperature of 24.degree. C., the relative humidity of 32%, a
piston speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s (hereinbelow, also referred to as "measurement
condition 1") (hereinbelow, also referred to as "ventilation
resistance 1"). A larger ventilation resistance means that air is
unlikely to flow and refers to a state of a high density. In this
state, the product from electrolysis remains in the electrode and
the reaction substrate is more unlikely to diffuse inside the
electrode, and thus, the electrolytic performance (such as voltage)
tends to deteriorate. The concentration on the membrane surface
tends to increase. Specifically, the caustic concentration
increases on the cathode surface, and the supply of brine tends to
decrease on the anode surface. As a result, the product accumulates
at a high concentration on the interface at which the membrane is
in contact with the electrode. This accumulation leads to damage of
the membrane and tends to also lead to increase in the voltage and
damage of the membrane on the cathode surface and damage of the
membrane on the anode surface. In the present embodiment, in order
to prevent these defects, the ventilation resistance is preferably
set at 24kPas/m or less. From a similar viewpoint as above, the
ventilation resistance is more preferably less than 0.19 kPas/m,
further preferably 0.15 kPas/m or less, further more preferably
0.07 kPas/m or less.
[0573] In the present embodiment, when the ventilation resistance
is larger than a certain value, NaOH generated in the electrode
tends to accumulate on the interface between the electrode and the
membrane to result in a high concentration in the case of the
cathode, and the supply of brine tends to decrease to cause the
brine concentration to be lower the case of the anode. In order to
prevent damage to the membrane that may be caused by such
accumulation, the ventilation resistance is preferably less than
0.19 kPas/m, more preferably 0.15 kPas/m or less, further
preferably 0.07 kPas/m or less.
[0574] In contrast, when the ventilation resistance is low, the
area of the electrode is reduced and the electrolysis area is
reduced. Thus, the electrolytic performance (such as voltage) tends
to deteriorate. When the ventilation resistance is zero, the feed
conductor functions as the electrode because no electrode for
electrolysis is provided, and the electrolytic performance (such as
voltage) tends to markedly deteriorate. From this viewpoint, a
preferable lower limit value identified as the ventilation
resistance 1 is not particularly limited, but is preferably more
than 0 kPas/m, more preferably 0.0001 kPas/m or more, further
preferably 0.001 kPas/m or more.
[0575] When the ventilation resistance 1 is 0.07 kPas/m or less, a
sufficient measurement accuracy may not be achieved because of the
measurement method therefor. From this viewpoint, it is also
possible to evaluate an electrode for electrolysis having a
ventilation resistance 1 of 0.07 kPas/m or less by means of a
ventilation resistance (hereinbelow, also referred to as
"ventilation resistance 2") obtained by the following measurement
method (hereinbelow, also referred to as "measurement condition
2"). That is, the ventilation resistance 2 is a ventilation
resistance measured, when the electrode for electrolysis has a size
of 50 mm.times.50 mm, under conditions of the temperature of
24.degree. C., the relative humidity of 32%, a piston speed of 2
cm/s, and a ventilation volume of 4 cc/cm.sup.2/s.
[0576] The specific methods for measuring the ventilation
resistances 1 and 2 are described in Examples.
[0577] The ventilation resistances 1 and 2 can be within the range
described above by appropriately adjusting an opening ratio,
thickness of the electrode, and the like, for example. More
specifically, for example, when the thickness is constant, a higher
opening ratio tends to lead to smaller ventilation resistances 1
and 2, and a lower opening ratio tends to lead to larger
ventilation resistances 1 and 2.
[0578] In the electrode for electrolysis of the present embodiment,
as mentioned above, the force applied per unit massunit area of the
electrode for electrolysis on the membrane or feed conductor is
less than 1.5 N/mgcm.sup.2. In this manner, the electrode for
electrolysis of the present embodiment abuts with a moderate
adhesive force on the membrane or feed conductor (e.g., the
existing anode or cathode in the electrolyzer) to thereby enable a
laminate with the membrane or feed conductor to be constituted.
That is, it is not necessary to cause the membrane or feed
conductor to firmly adhere to the electrode for electrolysis by a
complicated method such as thermal compression. The laminate is
formed only by a relatively weak force, for example, a surface
tension derived from moisture contained in the membrane such as an
ion exchange membrane and a microporous membrane, and thus, a
laminate of any scale can be easily constituted. Additionally, such
a laminate exhibits excellent electrolytic performance. Thus, the
laminate of the present embodiment is suitable for electrolysis
applications, and can be particularly preferably used for
applications related to members of electrolyzers and renewing the
members.
[0579] Hereinbelow, one aspect of the electrode for electrolysis of
the present embodiment will be described.
[0580] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[0581] As shown in FIG. 22, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[0582] Also shown in FIG. 22, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[0583] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[0584] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[0585] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[0586] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[0587] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[0588] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[0589] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[0590] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[0591] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[0592] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 8
.mu.m.
[0593] Next, a case where the electrode for electrolysis of the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[0594] In FIG. 22, a first layer 20 as a catalyst layer contains at
least one of ruthenium oxides, iridium oxides, and titanium oxides.
Examples of the ruthenium oxide include RuO.sub.2. Examples of the
iridium oxide include IrO.sub.2. Examples of the titanium oxide
include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[0595] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0596] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol of the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0597] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[0598] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[0599] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[0600] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[0601] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[0602] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[0603] Next, a case where the electrode for electrolysis of the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[0604] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[0605] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[0606] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[0607] As the platinum group metal, platinum is preferably
contained.
[0608] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[0609] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[0610] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[0611] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[0612] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[0613] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[0614] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[0615] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium.+-.lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium.+-.samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[0616] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[0617] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[0618] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[0619] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[0620] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The durability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[0621] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[0622] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Yb, and Lu, and oxides and hydroxides of the
metals.
[0623] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[0624] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness more preferably 0.1 .mu.m to 10 .mu.m. The thickness
is further preferably 0.2 .mu.m to 8 .mu.m.
[0625] The thickness of the electrode for electrolysis, that is,
the total thickness of the substrate for electrode for electrolysis
and the catalyst layer is preferably 315 .mu.m or less, more
preferably 220 .mu.m or less, further preferably 170 .mu.m or less,
further more preferably 150 .mu.m or less, particularly preferably
1.45 .mu.m or less, still more preferably 140 .mu.m or less, even
still more preferably 138 .mu.m or less, further still more
preferably 135 .mu.m or less in respect of the handling property of
the electrode for electrolysis. A thickness of 135 .mu.m or less
can provide a good handling property. Further, from a similar
viewpoint as above, the thickness is preferably 130 .mu.m or less,
more preferably less than 130 .mu.m, further preferably 115 .mu.m
or less, further more preferably 65 .mu.m or less. The lower limit
value is not particular limited, but is preferably 1 .mu.m or more,
more preferably 5 .mu.m or more for practical reasons, more
preferably 20 .mu.m or more. The thickness of the electrode can be
determined by measurement with a digimatic thickness gauge
(Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of
the substrate for electrode for electrolysis can be measured in the
same manner as in the case of the electrode for electrolysis. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode for electrolysis.
(Method for Producing Electrode for Electrolysis)
[0626] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[0627] In the present embodiment, the electrode for electrolysis
100 can be produced by for the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking or a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, a catalyst layer is formed on the
substrate for electrode for electrolysis by an application step of
applying a coating liquid containing a catalyst, a drying step of
drying the coating liquid, and a pyrolysis step of performing
pyrolysis. Pyrolysis herein means that a metal salt which is to be
a precursor is decomposed by heating into a metal or metal oxide
and a gaseous substance. The decomposition product depends on the
metal species to be used, type of the salt, and the atmosphere
under which pyrolysis is performed, and many metals tend to form
oxides in an oxidizing atmosphere. In an industrial process of
producing an electrode, pyrolysis is usually performed in air, and
a metal oxide or a metal hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[0628] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[0629] The metal salts may he chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[0630] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0631] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable 5 to 20 minutes more preferable.
[0632] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[0633] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[0634] The first layer 20 obtained by applying a solution in which
metal salts of various combination are dissolved (first coating
liquid) onto the substrate for electrode for electrolysis and then
pyrolyzing (baking) the coating liquid in the presence of oxygen.
The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[0635] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[0636] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0637] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[0638] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and the
further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[0639] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[0640] The first layer 20 can be formed also by ion plating.
[0641] An example includes a method in which the substrate is fixed
in a chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[0642] The first layer 20 can be formed also by a plating
method.
[0643] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[0644] The first layer 20 can be formed also by thermal
spraying.
[0645] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[0646] The electrode for electrolysis of the present embodiment can
be integrated with a membrane such as an exchange membrane and a
microporous membrane and used. Thus, the electrode can be used as a
membrane-integrated electrode. Then, the substituting work for the
cathode and anode on renewing the electrode is eliminated, and the
work efficiency markedly improved.
[0647] The electrode integrated with the membrane such as an ion
exchange membrane and a microporous membrane can make the
electrolytic performance comparable to or higher than those of a
new electrode.
[0648] Hereinafter, the ion exchange membrane will be described in
detail.
[Ion Exchange Membrane]
[0649] The ion exchange membrane has a membrane body containing a
hydrocarbon polymer or fluorine-containing polymer having an ion
exchange group and a coating layer provided on at least one surface
of the membrane body. The coating layer contains inorganic material
particles and a binder, and the specific surface area of the
coating layer is 0.1 to 10 m.sup.2/g. In the ion exchange membrane
having such a structure, the influence of gas generated during
electrolysis on electrolytic performance is small, and stable
electrolytic performance can be exhibited.
[0650] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO.sub.3.sup.-, hereinbelow
also referred to as a "sulfonic acid group") or a carboxylic acid
layer having an ion exchange group derived from a carboxyl group (a
group represented by --CO.sub.2.sup.-, hereinbelow also referred to
as a "carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[0651] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[0652] FIG. 23 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-contain polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[0653] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by
--SO.sub.3.sup.-, hereinbelow also referred to as a "sulfonic acid
group") and a carboxylic acid layer 2 having an ion exchange group
derived from a carboxyl group (a group represented by --CO.sub.2--,
hereinbelow also referred to as a "carboxylic acid group"), and the
reinforcement core materials 4 enhance the strength and dimension
stability. The ion exchange membrane 1, as comprising the sulfonic
acid layer 3 and the carboxylic acid layer 2, suitably used as an
anion exchange membrane.
[0654] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 23.
(Membrane Body)
[0655] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[0656] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[0657] The hydrocarbon polymer or fluorine-containing, polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[0658] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[0659] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[0660] Examples of the monomers of the second group include
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxy acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.s--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[0661] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[0662] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time of hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[0663] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group
[0664]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[0665]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[0666]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[0667]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[0668] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[0669] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[0670] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[0671] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[0672]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[0673]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[0674] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[0675]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[0676]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[0677] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[0678] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[0679] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[0680] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0. to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[0681] In the membrane body 10 of the ion exchange membrane a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[0682] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer 2 is
located on the cathode side of the electrolyzer.
[0683] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[0684] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[0685] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[0686] As the fluorine-containing polymer for use in the carboxyl
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[0687] The ion exchange membrane has a coating layer on at least
one surface of the membrane body. As shown in FIG. 23, in the ion
exchange membrane 1, coating layers 11a and 11b are formed on both
the surfaces of the membrane body 10.
[0688] The coating layers contain inorganic material particles and
a binder.
[0689] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[0690] The average particle size of the inorganic material articles
can be 2 .mu.m or less. When the average particle size of the
inorganic material particles is 2 .mu.m or less, it is possible to
prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[0691] Here, the average particle size can be measured by a partcle
size analyzer ("SALD2200", SHIMADZU CORPORATION).
[0692] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[0693] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides of Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durability, zirconium
oxide particle is more preferable.
[0694] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[0695] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurities such as iron attached to the
surface of the inorganic material particles.
[0696] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[0697] As the binder, a fluorine-containing, polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing, polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder of the coating layer.
[0698] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[0699] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperaties on the surface thereof,
the distribution density of the coating, layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[0700] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[0701] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[0702] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contraction of the ion
exchange membrane can be controlled in the desired range. Such an
ion exchange membrane does not expand or contract more than
necessary during electrolysis and the like and can maintain
excellent dimensional stability for a long term.
[0703] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[0704] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, alkalis, etc., and a
fiber comprising a fluorine-containing polymer preferable because
long-term heat resistance and chemical resistance are required.
[0705] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[0706] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) is preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[0707] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[0708] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[0709] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[0710] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred, to as MD yarns, and
yarns woven along the TD are referred to as ID yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the ID. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[0711] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[0712] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[0713] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area of a surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[0714] FIG. 24 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 24, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[0715] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[0716] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[0717] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[0718] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[0719] The continuous boles refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[0720] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[0721] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[0722] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[0723] A suitable example of a method, for producing an ion
exchange membrane includes a method including the following steps
(1) to (6):
[0724] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[0725] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[0726] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[0727] Step (4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[0728] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[0729] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step),
[0730] Hereinafter, each of the steps will be described in
detail.
[0731] Step (1): Step of Producing Fluorine-Containing Polymer
[0732] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[0733] Step (2): Step of Producing Reinforcing Materials
[0734] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[0735] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and comprising polyvinyl alcohol and
the like are also preferred.
[0736] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[0737] Step (3): Step of Film Formation
[0738] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[0739] Examples of the film forming method include the
following:
[0740] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[0741] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[0742] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[0743] Step (4): Step of Obtaining Membrane Body
[0744] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[0745] Preferable examples of the method or forming a membrane body
include a method in which a fluorine-containing polymer having a
carboxylic acid group precursor (e.g., carboxylate functional
group) (hereinafter, a layer comprising the same is referred to as
the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[0746] Coextrusion of the first layer and the second layer her en
contributes to an increase in the adhesive strength at the
interface.
[0747] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property of sufficiently retaining
the mechanical strength of the ion exchange membrane.
[0748] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[0749] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[0750] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[0751] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[0752] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[0753] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that is, projections, on the surface
side composed of the sulfonic acid layer. As a method, for forming
such projections, which is not particularly limited, a known method
also can be employed including forming projections on a resin
surface. A specific example of the method is a method of embossing
the surface of the membrane body. For example, the above
projections can be formed by using release paper embossed in
advance when the composite film mentioned above, reinforcing
material, and the like are integrated. In the case where
projections are formed by embossing, the height and arrangement
density of the projections can be controlled by controlling the
emboss shape to be transferred (shape of the release paper).
[0754] (5) Hydrolysis Step
[0755] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[0756] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[0757] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[0758] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[0759] The mixed solution preferably contains NON of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[0760] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[0761] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[0762] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 25(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[0763] FIGS. 25(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[0764] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[0765] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[0766] FIG. 25(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
[0767] (6) Application step
[0768] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[0769] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counterion of the ion exchange
group by H+ (e.g., a fluorine-containing polymer having a carboxyl
group or sulfo group). Thereby, the polymer is more likely to
dissolve in water or ethanol mentioned below, which is
preferable.
[0770] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[0771] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[0772] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[0773] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[0774] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[0775] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example, and is preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[0776] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[0777] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[0778] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[0779] The reason why the laminate with the membrane of the present
embodiment develops excellent electrolytic performance is presumed
as follows. When the membrane and the electrode firmly adhere to
each other by a method such as thermal compression, which is a
conventional technique, the electrode sinks into the membrane to
thereby physically adhere thereto. This adhesion portion inhibits
sodium ions from migrating in the membrane to thereby markedly
raise the voltage. Meanwhile, inhibition of migration of sodium
ions in the membrane, which has been a problem in the conventional
art, is eliminated by allowing the electrode for electrolysis to
abut with a moderate adhesive force on the membrane or feed
conductor, as in the present embodiment. According to the
foregoing, when the membrane or feed conductor abuts on the
electrode for electrolysis with a moderate adhesive force, the
membrane or feed conductor and the electrode for electrolysis,
despite of being an integrated piece, can develop excellent
electrolytic performance.
[Wound Body]
[0780] The wound body of the present embodiment includes the
laminate of the present embodiment. That is, the wound body of the
present embodiment is obtained by winding the laminate of the
present embodiment. Downsizing the laminate of the present
embodiment by winding, like the wound body of the present
embodiment, can further improve the handling property.
[Electrolyzer]
[0781] The electrolyzer of the present embodiment includes the
laminate of the present embodiment. Hereinafter, the case of
performing common salt electrolysis by using an ion exchange
membrane as the membrane is taken as an example, and one embodiment
of the electrolyzer will be described in detail.
[Electrolytic Cell]
[0782] FIG. 26 illustrates a cross-sectional view of an
electrolytic cell 1.
[0783] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell 1 has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 30, and the cathode 1 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer may be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support 24, the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[0784] FIG. 27 illustrates a cross-sectional view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
28 shows an electrolyzer 4. FIG. 29 shows a step of assembling the
electrolyzer 4. As shown in FIG. 27, an electrolytic cell 1, a
cation exchange membrane 2, and an electrolytic cell 1 are arranged
in series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 among
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 28, the
electrolyzer 4 is composed of a plurality of electrolytic cells 1
connected in series via the ion exchange membrane 2. That is, the
electrolyzer 4 is a bipolar electrolyzer comprising the plurality
of electrolytic cells 1 arranged in series and ion exchange
membranes 2 each arranged between adjacent electrolytic cells 1. As
shown in FIG. 29, the electrolyzer 4 is assembled by arranging the
plurality of electrolytic cells 1 in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[0785] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during, electrolysis flows
from the side or the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[0786] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell through the ion exchange
membrane to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[0787] The anode chamber 10 has the anode 11 or anode feed
conductor 11. When the electrode for electrolysis of the present
embodiment is inserted to the anode side, 11 serves as the anode
feed conductor. When the electrode for electrolysis of the present
embodiment is not inserted to the anode side, 11 serves as the
anode. The anode chamber 10 has an anode side electrolyte solution
supply unit that supplies an electrolyte solution to the anode
chamber 10, a baffle plate that is arranged above the anode-side
electrolyte solution supply unit so as to be substantially parallel
or oblique to the partition wall 30, and an anode-side gas liquid
separation unit arranged above the baffle plate to separate gas
from the electrolyte solution including the gas mixed.
(Anode)
[0788] When the electrode for electrolysis of the present
embodiment is not inserted to the anode side, the anode 11 is
provided in the frame of the anode chamber 10. As the anode 11, a
metal electrode such as so-called DSA(R) can be used. DSA is an
electrode including a titanium substrate of which surface is
covered with an oxide comprising ruthenium, iridium, and titanium
as components.
[0789] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[0790] When the electrode for electrolysis of the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having a thinner catalyst coating can be also
used. Further, a used anode can be also used.
[0791] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[0792] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[0793] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 26, and below means the lower direction
in the electrolytic cell 1 in FIG. 26.
[0794] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 of the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle Plate)
[0795] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[0796] Although not shown in FIG. 26, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[0797] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding, a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[0798] In the cathode chamber 20, when the electrode for
electrolysis of the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed, conductor. When the electrode
for electrolysis of the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[0799] When the electrode for electrolysis of the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20. The cathode 21
preferably has a nickel substrate and a catalyst layer that covers
the nickel substrate. Examples of the components of the catalyst
layer on the nickel substrate include metals such as Ru, C, Si, P,
S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include platinu, alloy plating, dispersion/composite
plating CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. The cathode 21 may
be subjected to a reduction treatment, as required. As the
substrate of the cathode 21, nickel, nickel alloys, and
nickel-plated iron or stainless may be used.
[0800] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[0801] When the electrode for electrolysis of the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Alternatively,
nickel, nickel alloys, and nickel-plated iron or stainless, having
no catalyst coating, may be used. As the substrate of the cathode
feed conductor 21, nickel, nickel alloys, and nickel-plated iron or
stainless may be used.
[0802] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[0803] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[0804] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[0805] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[0806] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entire across the plurality of electrolytic cells 1 connected in
series. Lowering of the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis according to the present
embodiment is placed in the electrolytic cell.
[0807] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[0808] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[0809] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[0810] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane 2 (See FIGS. 26 and 27).
These gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[0811] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced as and be
usable for long period. Thus, in respect of chemical resistance and
hardness, vulcanized products and peroxide-crosslinked products of
ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 27), each
electrolytic cell 1 onto which the gasket is attached should be
tightened via ion exchange membrane 2. This tightening can prevent
the electrolyte solution, alkali metal hydroxide, chlorine gas,
hydrogen gas, and the like generated from electrolysis from leaking
out of the electrolytic cells 1.
(Ion Exchange Membrane)
[0812] The ion exchange membrane 2 is as described in the section
of the ion exchange membrane described above.
(Water Electrolysis)
[0813] The electrolyzer of the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
(Application of Laminate)
[0814] The laminate of the present embodiment can improve the work
efficiency during electrode renewing in an electrolyzer and
further, can exhibit excellent electrolytic performance also after
renewing as mentioned above. In other words, the laminate of the
present embodiment can be suitably used as a laminate for
replacement of a member of an electrolyzer. A laminate to be used
in such an application is specifically referred to as a "membrane
electrode assembly".
(Package)
[0815] The laminate of the present embodiment is preferably
transported or the like while enclosed in a packaging material.
That is, the package of the present embodiment comprises the
laminate of the present embodiment and a packaging material that
packages the laminate. The package of the present embodiment,
configured as described above, can prevent adhesion of stain and
damage that may occur during transport or the like of the laminate
of the present embodiment. When used for member replacement of the
electrolyzer, the laminate is particularly preferably transported
or the like as the package of the present embodiment. As the
packaging material of the present embodiment, which is not
particularly limited, known various packaging materials can be
employed. Alternatively, the package of the present embodiment can
be produced by, for example, a method including packaging the
laminate of the present embodiment with a clean packaging material
followed by encapsulation or the like, although not limited
thereto.
Third Embodiment
[0816] Here, a third embodiment of the present invention will be
described in detail with reference to FIGS. 43 to 62.
[Laminate]
[0817] The laminate of the third embodiment (hereinafter, in the
section of <Third embodiment>, simply referred to as "the
present embodiment") has a membrane and an electrode for
electrolysis fixed at least one region of the surface of the
"membrane " (hereinafter, simply also referred to as a "fixed
region"), and the proportion of the region on the surface of the
membrane is more than 0% and less than 93%. The laminate of the
present embodiment, as configured as described above, can improve
the work efficiency during electrode renewing in an electrolyzer
and further, can exhibit excellent electrolytic performance also
after renewing.
[0818] That is, according to the laminate of the present
embodiment, on renewing the electrode, the electrode can be renewed
by a work as simple as renewing the membrane, without a complicated
work such as stripping off the existing electrode fixed on the
electrolytic cell, and thus, the work efficiency is markedly
improved.
[0819] Further, according to the laminate of the present
embodiment, it is possible to maintain the electrolytic performance
of the existing electrolytic cell comparable to those of a new
electrode or improve the electrolytic performance. Thus, the
electrode fixed on the existing electrolytic cell and serving as an
anode and/or a cathode is only required to serve as a feed
conductor. Thus, it may be also possible to markedly reduce or
eliminate catalyst coating. The feed conductor herein means a
degraded electrode (i.e., the existing electrode), an electrode
having no catalyst coating, and the like.
[Electrode for Electrolysis]
[0820] The electrode for electrolysis in the present embodiment is
not particularly limited as long as the electrode is an electrode
to be used for electrolysis, and preferably has an area of the
surface opposed to the membrane of the electrode for electrolysis
(corresponds to an area of the conducting surface 32 mentioned
below) of 0.01 m.sup.2 or more. The "surface opposed to the
membrane" means the surface on which the membrane is located of the
surfaces possessed by the electrode for electrolysis. That is, the
surface opposed to the membrane in the electrode for electrolysis
also can be the surface that abuts on the surface of the membrane.
When the area of the surface opposed to the membrane in the
electrode for electrolysis is 0.01 m.sup.2 or more, sufficient
productivity can be achieved, and especially when industrial
electrolysis is performed, sufficient productivity tends to be
obtained. In this manner, from the viewpoint of achieving
sufficient productivity and achieving practicality for a laminate
to be used in renewing of the electrolytic cell, the area of the
surface opposed to the membrane in the electrode for electrolysis
is more preferably 0.1 m.sup.2 or more, further preferably 1
m.sup.2 or more. The area can be measured by, for example, a method
described in Examples.
[0821] The electrode for electrolysis in the present embodiment has
a force applied per unit massunit area of preferably 1.6
N/(mgcm.sup.2) or less, more preferably less than 1.6
N/(mgcm.sup.2), further preferably less than 1.5 N/(mgcm.sup.2),
even further preferably 1.2 N/mgcm.sup.2 or less, still more
preferably 1.20 N/mgcm.sup.2 or less from the viewpoint of enabling
a good handling property to be provided and having a good adhesive
force to a membrane such as an ion exchange membrane and a
microporous membrane, a feed conductor (a degraded electrode and an
electrode having no catalyst coating), and the like. The force
applied is even still more preferably 1.1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[0822] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0.2 N/(mgcm.sup.2) or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[0823] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[0824] The mass per unit is preferably 48 mg/cm.sup.2 or less, more
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and of economy, and furthermore is 15 mg/cm.sup.2 or less from the
comprehensive viewpoint including handling property, adhesion, and
economy. The lower limit value is not particularly limited but is
of the order of 1 mg/cm.sup.2, for example.
[0825] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[0826] The force applied can be measured by the following method
(i) or (ii). The value obtained by the measurement of the method
(i) (also referred to as "the force applied (1)") and the value
obtained by the measurement of the method (ii) (also referred to as
"the force applied (2)") may be the same or different, and either
of the values is preferably less than 1.5 N/mgcm.sup.2.
[Method (i)]
[0827] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square), and a sample of electrode (130 mm
square) are laminated in this order. After this laminate is
sufficiently immersed in pure water, excess water deposited on the
surface of the laminate is removed to obtain a sample for
measurement. The arithmetic average surface roughness (Ra) of the
nickel plate after the blast treatment is 0.5 to 0.8 .mu.m. The
specific method for calculating the arithmetic average surface
roughness (Ra) is as described in Examples.
[0828] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode in
this sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[0829] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[0830] The force applied per unit massunit area (1) obtained by the
method (i) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mg=i.sup.2), even further. preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. The force is preferably more than 0.005 N/(mgcm.sup.2),
more preferably 0.08 N/(mgcm.sup.2) or more, further preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of further improving the
electrolytic performance, and furthermore, is further more
preferably 0.14 N/(mgcm.sup.2), still more preferably 0.2
N/(mgcm.sup.2) or more from the viewpoint of further facilitating
handling in a large size (e.g., a size of 1.5 m.times.2.5 m).
[Method (ii)]
[0831] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[0832] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[0833] The force applied per unit massunit area (2) obtained by the
method (ii) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2) even further preferably 1.2 N/mgcm.sup.2 or
less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. Further, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/(mgcm.sup.2) or more from the viewpoint of
further improving the electrolytic performance, and is further more
preferably 0.14 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[0834] The electrode for electrolysis in the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 120 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having, no catalyst coating, being capable or being
suitably rolled in a roll and satisfactorily folded, and
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[0835] The proportion measured by the following method (2) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint or further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2)]
[0836] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[0837] The proportion measured by the following method (3) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[0838] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[0839] The electrode for electrolysis in the present embodiment
preferably has a porous structure and an opening ratio or void
ratio of 5 to 90% or less from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having, no catalyst coating, and preventing
accumulation of gas to be generated during electrolysis, although
not particularly limited. The opening ratio is more preferably 10
to 80% or less, further preferably 20 to 75%.
[0840] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V was calculated from the values of the gauge thickness,
width, and length of the electrode, and further, a weight W was
measured to thereby calculate an opening ratio A by the following
formula.
A=(1-(W/(V.times..rho.)).times.100
[0841] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio is appropriately
adjusted by changing the area of metal to be perforated per unit
area in the case of perforated metal, changing the values of the SW
(short diameter), LW (long diameter), and feed in the case of
expanded metal, changing the line diameter of metal fiber and, mesh
number in the case of mesh, changing the pattern of a photoresist
to be used in the case of electroforming, changing the metal fiber
diameter and fiber density in the case of nonwoven fabric,
changing, the mold for forming, voids in the case of foamed metal,
or the like.
[0842] Hereinbelow, one aspect of the electrode for electrolysis in
the present embodiment will be described.
[0843] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[0844] As shown in FIG. 43, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[0845] Also as shown FIG. 43, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[0846] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[0847] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[0848] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[0849] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[0850] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[0851] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[0852] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[0853] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[0854] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[0855] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 8
.mu.m.
[0856] Next, a case where the electrode for electrolysis in the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[0857] In FIG. 43, a first layer 20 as a catalyst layer contains at
least one of ruthenium oxides, iridium oxides, and titanium oxides.
Examples of the ruthenium oxide include RuO.sub.2. Examples of the
iridium oxide include IrO.sub.2. Examples of the titanium oxide
include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[0858] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0859] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol or the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[0860] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[0861] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[0862] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[0863] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[0864] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[0865] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[0866] Next, a case where the electrode for electrolysis in the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[0867] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re,
Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,
Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[0868] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[0869] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[0870] As the platinum group metal, platinum is preferably
contained.
[0871] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[0872] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[0873] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[0874] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[0875] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[0876] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[0877] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[0878] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[0879] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[0880] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[0881] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[0882] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[0883] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The curability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[0884] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[0885] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Cu, Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os,
Tr, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho,
Tm, Yb, and Lu, and oxides and hydroxides of the metals.
[0886] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[0887] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness is more preferably 0.1 .mu.m to 10 .mu.m. The
thickness is further preferably 0.2 .mu.m to 8 .mu.m.
[0888] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis is
measured in the same manner as the thickness of the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
[0889] In the present embodiment, the electrode for electrolysis
preferably contains at least one catalytic component selected from
the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, Re, Os, Al, In, Sn, Sb, Ga,
Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and
Dy from the viewpoint of achieving sufficient electrolytic
performance.
[0890] In the present embodiment, from the viewpoint that the
electrode for electrolysis, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a macroporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, furthermore preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness or 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
(Method for Producing Electrode for Electrolysis)
[0891] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[0892] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking or a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, a catalyst layer is formed on the
substrate for electrode for electrolysis by an application step of
applying a coating liquid containing a catalyst, a drying step of
drying the coating liquid, and a pyrolysis step of performing
pyrolysis. Pyrolysis herein means that a metal salt which is to be
a precursor is decomposed by heating into a metal or metal oxide
and a gaseous substance. The decomposition product depends on the
metal species to be used, type of the salt, and the atmosphere
under which pyrolysis is performed, and many metals tend to form
oxides in an oxidizing atmosphere. In an industrial process of
producing an electrode, pyrolysis is usually performed in air, and
a metal oxide or a metal hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[0893] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[0894] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[0895] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0896] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable 5 to 20 minutes more preferable.
[0897] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[0898] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[0899] The first layer 20 obtained by applying a solution in which
metal salts of various combination are dissolved (first coating
liquid) onto the substrate for electrode for electrolysis and then
pyrolyzing (baking) the coating liquid in the presence of oxygen.
The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[0900] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[0901] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[0902] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[0903] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and the
further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[0904] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[0905] The first layer 20 can be formed also by ion plating. An
example includes a method in which the substrate is fixed in a
chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[0906] The first layer 20 can be formed also by a plating
method.
[0907] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[0908] The first layer 20 can be formed also by thermal
spraying.
[0909] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[0910] The electrode for electrolysis in the present embodiment can
be integrated with a membrane such as an ion exchange membrane and
a microporous membrane and used. Thus, the laminate of the present
embodiment can be used as a membrane-integrated electrode. Then,
the substituting work for the cathode and anode on renewing the
electrode is eliminated, and the work efficiency is markedly
improved.
[0911] The electrode integrated with the membrane such as an ion
exchange membrane and a microporous membrane can make the
electrolytic performance comparable to or higher than those of a
new electrode.
[0912] Hereinafter, the ion exchange membrane will be described in
detail.
[Ion Exchange Membrane]
[0913] The ion exchange membrane is not particularly limited as
long as the membrane can be laminated with the electrode for
electrolysis, and various ion exchange membranes may be employed.
In the present embodiment, an ion exchange membrane that has a
membrane body containing a hydrocarbon polymer or
fluorine-containing polymer having an ion exchange group and a
coating layer provided on at least one surface of the membrane body
is preferably used. It is preferable that the coating layer contain
inorganic material particles and a binder and the specific surface
area of the coating layer be 0.1 to 10 m.sup.2/g. The ion exchange
membrane having such a structure has a small influence of gas
generated during electrolysis on electrolytic performance and tends
to exert stable electrolytic performance.
[0914] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO.sub.3.sup.-, hereinbelow
also referred to as a "sulfonic acid group") or a carboxylic acid
layer having an ion exchange group derived from a carboxyl group (a
group represented by --CO.sub.2.sup.-, hereinbelow also referred to
as a "carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[0915] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[0916] FIG. 44 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane.
[0917] An ion exchange membrane 1 has a membrane body 10 containing
a hydrocarbon polymer or fluorine-containing polymer having an ion
exchange group and coating layers 11a and 11b formed on both the
surfaces of the membrane body 10.
[0918] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by
--SO.sub.3.sup.-, hereinbelow also referred to as a "sulfonic acid
group") and a carboxylic acid layer 2 having an ion exchange group
derived from a carboxyl group (a group represented by
--CO.sub.2.sup.-, hereinbelow also referred to as a "carboxylic
acid group"), and the reinforcement core materials 4 enhance the
strength and dimension stability. The ion exchange membrane 1, as
comprising the sulfonic acid layer 3 and the carboxylic acid layer
2, is suitably used as an anion exchange membrane.
[0919] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example FIG. 44.
(Membrane Body)
[0920] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[0921] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[0922] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[0923] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[0924] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[0925] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.s--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[0926] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[0927] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time or hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[0928] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[0929]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[0930]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[0931]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[0932]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[0933] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[0934] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[0935] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having, a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[0936] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[0937]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[0938]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[0939] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[0940]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[0941]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[0942] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[0943] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[0944] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[0945] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0.5 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[0946] In the membrane body 10 of the ion exchange membrane 1, a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[0947] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer 2
located on the cathode side of the electrolyzer.
[0948] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[0949] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[0950] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[0951] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[0952] The ion exchange membrane preferably has a coating layer on
at least one surface of the membrane body. As shown in FIG. 44, in
the ion exchange membrane 1, coating layers 11a and 11b are formed
on both the surfaces of the membrane body 10.
[0953] The coating layers contain inorganic material particles and
a binder.
[0954] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[0955] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[0956] Here, the average particle size can be measured by a
particle size analyzer ("SALD2200", SHIMADZU CORPORATION).
[0957] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[0958] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides or Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durability, zirconium
oxide particle is more preferable.
[0959] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[0960] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurities such as iron attached to the
surface of the inorganic material particles.
[0961] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint or durability to the electrolyte
solution and products from electrolysis.
[0962] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder of the coating layer.
[0963] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[0964] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[0965] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[0966] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[0967] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contract the ion exchange
membrane can be controlled in the desired range. Such an ion
exchange membrane does not expand or contract more than necessary
during electrolysis and the like and can maintain excellent
dimensional stability for a long term.
[0968] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
enforcement yarns. The reinforcement yarns here refer to yarns that
are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[0969] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, alkalis, etc., and a
fiber comprising a fluorine-containing polymer is preferable
because long-term heat resistance and chemical resistance are
required.
[0970] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[0971] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) is preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[0972] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[0973] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[0974] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[0975] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[0976] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[0977] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[0978] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area or surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[0979] FIG. 45 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 45, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting,
illustration of the other members.
[0980] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[0981] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[0982] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[0983] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[0984] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[0985] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[0986] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[0987] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[0988] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[0989] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[0990] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[0991] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[0992] Step (4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[0993] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[0994] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[0995] Hereinafter, each of the steps will be described in
detail.
[0996] Step (1): Step of Producing Fluorine-Containing Polymer
[0997] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[0998] Step (2): Step of Producing Reinforcing Materials
[0999] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[1000] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and comprising polyvinyl alcohol and
the like are also preferred.
[1001] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[1002] Step (3): Step of Film Formation
[1003] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[1004] Examples of the film forming method include the
following:
[1005] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[1006] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[1007] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[1008] Step (4): Step of Obtaining Membrane Body
[1009] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[1010] Preferable examples of the method for forming a membrane
body include a method in which a fluorine-containing polymer having
a carboxylic acid group precursor (e.g., carboxylate functional
group) (hereinafter, a layer comprising the same is referred to as
the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[1011] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[1012] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface f the
membrane body, the method has a property sufficiently retaining the
mechanical strength of the ion exchange membrane.
[1013] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[1014] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[1015] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[1016] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[1017] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[1018] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that is, projections, on the surface
side composed of the sulfonic acid layer. As a method for forming
such projections, which is not particularly limited, a known method
also can be employed including forming projections on a resin
surface. A specific example of the method is a method of embossing
the surface of the membrane body. For example, the above
projections can be formed by using release paper embossed in
advance when the composite film mentioned above, reinforcing
material, and the like are integrated. In the case where
projections are formed by embossing, the height and arrangement
density of the projections can be controlled by controlling the
emboss shape to be transferred (shape of the release paper).
[1019] (5) Hydrolysis Step
[1020] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[1021] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[1022] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[1023] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[1024] The mixed solution preferably contains KOH of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[1025] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[1026] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[1027] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 46(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[1028] FIGS. 46(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[1029] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[1030] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[1031] FIG. 46(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
[1032] (6) Application Step
[1033] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[1034] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counterion of the ion exchange
group by (e.g., a fluorine-containing polymer having a carboxyl
group or sulfo group). Thereby, the polymer is more likely to
dissolve in water or ethanol mentioned below, which is
preferable.
[1035] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[1036] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[1037] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[1038] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[1039] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[1040] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example, and is preferably 80 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[1041] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[1042] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[1043] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[1044] In the present embodiment, the membrane preferably comprises
a first ion exchange resin layer and a second ion exchange resin
layer having an EW (ion exchange capacity) different from that of
the first ion exchange resin layer. Additionally, the membrane
preferably comprises a first ion exchange resin layer and a second
ion exchange resin layer having a functional group different from
that of the first ion exchange resin layer. The ion exchange
capacity can be adjusted by the functional group to be introduced,
and functional groups that may be introduced are as mentioned
above.
[Fixed Region]
[1045] In the present embodiment, the electrode for electrolysis is
fixed in at least one region of a surface of the membrane, and in
the section of <Third embodiment>, the one or two or more
regions are also referred to as fixed regions. The fixed region in
the present embodiment is not particularly limited as long as the
region is a portion that has a function of preventing separation of
the electrode for electrolysis from the membrane and fixes the
membrane onto the electrode for electrolysis. For example, the
electrode for electrolysis per se may serve as a fixing means to
constitute the fixed region, or a fixing member, which is separate
from the electrode for electrolysis, may serve as a fixing means to
constitute the fixed region. The fixed region in the present
embodiment may be present only at the position corresponding to the
conducting surface during electrolysis or may extend to the
position corresponding to the non-conducting surface. The
"conducting surface" corresponds to a portion designed so as to
allow electrolytes to migrate between the anode chamber and the
cathode chamber. The "non-conducting surface" means a portion other
than the conducting surface.
[1046] Further, in the present embodiment, the proportion of the
fixed region on the surface of the membrane (hereinbelow, simply
also referred to as "proportion .alpha.") will be more than 0% and
less than 93%. The above proportion can be determined as the
proportion of the area of the fixed region (hereinbelow, simply
also referred to as the "area S3") to the area of the surface of
the membrane (hereinbelow, simply also referred to as the "area
S1"). In the present embodiment, "the surface of the membrane means
the surface of the side on which the electrode for electrolysis is
present among the surfaces possessed by the membrane. The area not
covered with the electrode for electrolysis in the surface of the
membrane mentioned above is also included in the area S1.
[1047] From the viewpoint of improving the stability as a laminate
of the membrane and the electrode for electrolysis, the proportion
.alpha. (=100.times.S3/S1) is preferably 0.00000001% or more, more
preferably 0.0000001% or more. In contrast, as in the conventional
art, in the case of the membrane and the electrode firmly adhere to
each other on the entire contact surface therebetween by a method
such as thermal compression (i.e., the case where the proportion is
100%), the entire contact surface of the electrode sinks into the
membrane to thereby physically adhere thereto. Such an adhesion
portion inhibits sodium ions from migrating in the membrane to
thereby markedly raise the voltage. In the present embodiment, from
the viewpoint of providing a sufficient space for ions to freely
migrate, the above proportion is less than 93%, preferably 90% or
less, more preferably 70% or less, further preferably less than
60%.
[1048] In the present embodiment, from the viewpoint of achieving
better electrolytic performance, it is preferable to adjust the
area of the portion corresponding only to the conducting surface
(hereinbelow, simply also referred to as the "area S3'") of the
area of the fixed region (area S3). That is, it is preferable to
adjust the proportion of the area S3' (hereinbelow, simply also
referred to as the "proportion .beta.") to the area of the
conducting surface (hereinbelow, simply also referred to as the
"area S2"). The area S2 can be identified as the surface area of
the electrode for electrolysis (the details will be mentioned
below). Specifically, in the present embodiment, the proportion
.beta. (=100.times.S3'/S2) is preferably more than 0% and less than
100%, more preferably 0.0000001% or more and less than 83%, further
preferably 0.000001% or more and 70% or less, even further
preferably 0.00001% or more and 25% or less.
[1049] The proportions .alpha. and .beta. described above can be
measured, for example, as follows.
[1050] First, the area of the surface of the membrane S1 is
calculated. Then, the area of the electrode for electrolysis S2 is
calculated. The areas S1 and S2 herein can be identified as the
area when the laminate of the membrane and the electrode for
electrolysis is viewed from the side of the electrode for
electrolysis (see FIG. 57).
[1051] The form of the electrode for electrolysis is not
particularly limited, and the electrode may have openings. In the
case where the form is net or the like, which has openings, and the
opening ratio is less than 90% (i), as for S2, the opening portions
thereof are included in the area S2. In contrast, in the case where
the opening ratio is 90% or more (ii), the area excluding the
opening portions is used to calculate S2 in order to achieve
electrolytic performance sufficiently. The opening ratio referred
to herein is a numerical value (%; 100.times.S'/S'') obtained by
dividing the total area of the opening portions S' in the electrode
for electrolysis by the area in the electrode for electrolysis S'',
which is obtained when the opening portions are included in the
area.
[1052] The area of the fixed region (area S3 and area S3') will be
mentioned below.
[1053] As described above, the proportion of the region .alpha.(%)
on the surface of the membrane can be determined by calculating
100.times.(S3/S1). Additionally, the proportion of the area of the
portion only corresponding to the conducting surface of the fixed
region .beta. (%) relative to the area of the conducting surface
can be determined by calculating 100.times.(S3'/S2).
[1054] More specifically, measurement can be performed by a method
described in Example mentioned below.
[1055] The area of the surface of the membrane S1 to be identified
as mentioned above is not particularly limited, but is preferably 1
time or more and 5 times or less, more preferably 1 time or more
and 4 times or less, further preferably 1 time or more and 3 times
or less the area of the conducting surface S2.
[1056] In the present embodiment, a fixing configuration in the
fixed region is not intended to be limited, but, for example, a
fixing configuration exemplified below can be employed. Only one
fixing configuration can be employed, or two or more fixing
configurations can be employed in combination.
[1057] In the present embodiment, at least a portion of the
electrode for electrolysis preferably penetrates the membrane and
thereby is fixed in the fixed region. The aspect will be described
by use of FIG. 47A.
[1058] In FIG. 47A, at least a portion of the electrode for
electrolysis 2 penetrates the membrane 3 and thereby is fixed. As
shown in FIG. 47A, the portion of the electrode for electrolysis 2
is penetrating the membrane 3. FIG. 47A shows an example in which
the electrode for electrolysis 2 is a metal porous electrode. That
is, in FIG. 47A, a plurality of portions of the electrode for
electrolysis 2 are separately shown, but these portions are
continuous. Thus, the cross-section of an integral metal porous
electrode shown (the same applies to FIGS. 48 to 51 below).
[1059] In the electrode configuration, when the membrane 3 in the
predetermined position (position to be the fixed region), for
example, is pressed onto the electrode for electrolysis 2, a
portion of the membrane 3 intrudes into the asperity geometry or
opening geometry on the surface of the electrode for electrolysis
2. Then, recesses on the electrode surface and projections around
openings penetrate the membrane 3 and preferably penetrate through
to the outer surface 3b of the membrane 3, as shown in FIG.
47A.
[1060] As described above, the fixing configuration in FIG. 47A can
be produced by pressing the membrane 3 onto the electrode for
electrolysis. In this case, the membrane 3 is softened by warming
and then subjected to thermal compression and thermal suction.
Then, the electrode for electrolysis 2 penetrates the membrane 3.
Alternatively, the membrane 3 may be used in a melt state. In this
case, the membrane 3 is preferably suctioned from the side of the
outer surface 2b (back surface side) of the electrode for
electrolysis 2 in the state shown in FIG. 47B. The region in which
the membrane 3 is pressed onto the electrode for electrolysis 2
constitutes the "fixed region".
[1061] The fixing configuration shown in FIG. 47A can be observed
by a magnifier (loupe), optical microscope, or electron microscope.
Since the electrode for electrolysis 2 has penetrated the membrane
3, it is possible to estimate the fixing configuration in FIG. 47A
by a test of the conduction between the outer surface 3b of the
membrane 3 and the outer surface 2b of the electrode for
electrolysis 2 by use of a tester or the like.
[1062] In FIG. 47A, no electrolyte solution in the anode chamber
and the cathode chamber partitioned by the membrane preferably
permeates the penetration portion. Thus, the pore size at the
penetration portion is preferably small enough not to allow the
electrolyte solution to permeate the portion. Specifically,
characteristics comparable to those of a membrane having no
penetration portion are preferably exerted when an electrolytic
test is performed. Alternatively, the penetration portion is
preferably subjected to processing for preventing permeation of the
electrolyte solution. It is preferable to use, in the penetration
portion, a material that is not eluted or decomposed by the anode
chamber electrolyte solution, products to be generated in the anode
chamber, the cathode chamber electrolyte solution, and products to
be generated in the cathode chamber. For example, EPDM and
fluorine-containing resins are preferable. A fluorine resin having
an ion exchange group is more preferable.
[1063] In the present embodiment, at least a portion of the
electrode for electrolysis is preferably located inside the
membrane and thereby fixed in the fixed region. The aspect will be
described by use of FIG. 48A.
[1064] As described above, the surface of the electrode for
electrolysis 2 has an asperity geometry or opening geometry. In the
embodiment shown in FIG. 48A, a portion of the electrode surface
enters the membrane 3 in the predetermined position (position to be
the fixed region) and is fixed thereto. The fixing configuration
shown in FIG. 48A can be produced by pressing the membrane 3 onto
the electrode for electrolysis 2. In this case, the fixing
configuration in FIG. 48A is preferably formed by softening the
membrane 3 by warming and then thermally compressing and thermally
suctioning the membrane 3. Alternatively, the fixing configuration
in FIG. 48A can be formed by melting the membrane 3. In this case,
the membrane 3 preferably suctioned from the side of the outer
surface 2b (back surface side) of the electrode for electrolysis
2.
[1065] The fixing configuration shown in FIG. 48A can be observed
by a magnifier (loupe), optical microscope, or electron microscope.
Particularly preferable is a method including subjecting the sample
to an embedding treatment, then forming a cross-section by a
microtome, and observing the cross-section. In the fixing
configuration shown in FIG. 48A, the electrode for electrolysis
does not penetrate the membrane 3. Thus, no conduction between the
outer surface 3b of the membrane 3 and the outer surface 2b of the
electrode for electrolysis 2 is identified by the conduction
test.
[1066] In the present embodiment, it is preferable to additionally
have a fixing member for fixing the membrane and the electrode for
electrolysis. The aspect will be described by use of FIGS. 49A to
C.
[1067] The fixing configuration shown in FIG. 49A is a
configuration in which a fixing member 7, which is separate from
the electrode for electrolysis 2 and the membrane 3, is used and
the fixing member 7 penetrates and thereby fixes the electrode for
electrolysis 2 and the membrane 3. The electrode for electrolysis 2
is not necessarily penetrated by the fixing member 7, and should be
fixed by the fixing member 7 so as not to be separated from the
membrane 2. The material for the fixing member 7 is not
particularly limited, and materials constituted by metal, resin,
the like, for example, can be used as the fixing member 7. Examples
of the metal include nickel, nichrome, titanium, and stainless
steel (SUS). Oxides thereof may be used. Examples of the resin that
can be used include fluorine resins (e.g., polytetrafluoroethylene
(PTFE), copolymers of tetrafluoroethylene and perfluoroalkoxy
ethylene (PFA), copolymers of tetrafluoroethylene and ethylene
(ETFE), materials for the membrane 3 described below,
polyvinylidene fluoride (PVDF), ethylene-propylene-diene rubber
(EPDM), polyethylene (PP), polypropylene (PE), on, and aramid.
[1068] In the present embodiment, for example, a yarn-like fixing
member (yarn-like metal or resin) is used to sew the predetermined
position (position to be the fixed region) between the outer
surface 2b of the electrode for electrolysis 2 and the outer
surface 3b of the membrane as shown in FIGS. 49B and C. The
yarn-like resin is not particularly limited, but examples thereof
include PTFE yarns. It is also possible to the electrode for
electrolysis 2 to the membrane 3 by use of a fixing mechanism such
as a tucker.
[1069] In FIGS. 49A to C, no electro solution in the anode chamber
and the cathode chamber partitioned by membrane preferably
permeates the penetration portion. Thus, the pore size at the
penetration portion is preferably small enough not to allow the
electrolyte solution to permeate the portion. Specifically,
characteristics comparable to those of a membrane having no
penetration portion are preferably exerted when an electrolytic
test is performed. Alternatively, the penetration portion is
preferably subjected to processing for preventing permeation of the
electrolyte solution. It is preferable to use, in the penetration
portion, a material that is not eluted or decomposed by the anode
chamber electrolyte solution, products to be generated in the anode
chamber, the cathode chamber electrolyte solution, and products to
be generated in the cathode chamber. For example, EPDM and
fluorine-containing resins are preferable. A fluorine resin having
an ion exchange group is more preferable.
[1070] The fixing configuration shown in FIG. 50 is a configuration
in which fixing is made by an organic resin (adhesion layer)
interposed between the electrode for electrolysis 2 and the
membrane 3. That is, in FIG. 50, shown is a configuration in which
an organic resin as the fixing member 7 is arranged on the
predetermined position (position to be the fixed region) between
the electrode for electrolysis 2 and the membrane 3 to thereby make
fixing by adhesion. For example, the organic resin is applied onto
the inner surface 2a of the electrode for electrolysis 2, the inner
surface 3a of the membrane 3, or one or both of the inner surface
2a of the electrode for electrolysis 2 and the inner surface 3a of
the membrane 3. Then, the fixing configuration shown in FIG. 50 can
be formed by laminating the electrode for electrolysis 2 to the
membrane 3. The materials for the organic resin are not
particularly limited, but examples thereof that can be used include
fluorine resins (e.g., PTFE, PFA, and ETFE) and resins similar to
the materials constituting the membrane 3 as mentioned above.
Commercially available fluorine-containing adhesives and PTFE
dispersions also can be used as appropriate. Additionally,
multi-purpose vinyl acetate adhesives, ethylene-vinyl acetate
copolymer adhesives, acrylic resin adhesives, .alpha.-olefin
adhesives, styrene-butadiene rubber latex adhesives, vinyl chloride
resin adhesives, chloroprene adhesives, nitrile rubber adhesives,
urethane rubber adhesives, epoxy adhesives, silicone resin
adhesives, modified silicone adhesives, epoxy-modified silicone
resin adhesives, silylated urethane resin adhesives, cyanoacrylate
adhesives, and the like also can be used.
[1071] In the present embodiment, organic resins that dissolve in
an electrolyte solution or dissolve or decompose during
electrolysis may be used. Examples of the organic resins that
dissolve in an electrolyte solution or dissolve or decompose during
electrolysis include, but are not limited to, vinyl acetate
adhesives, ethylene-vinyl acetate copolymer adhesives, acrylic
resin adhesives, .alpha.-olefin adhesives, styrene-butadiene rubber
latex adhesives, vinyl chloride resin adhesives, chloroprene
adhesives, nitrile rubber adhesives, urethane rubber adhesives,
epoxy adhesives, silicone resin adhesives, modified silicone
adhesives, epoxy-modified silicone resin adhesives, silylated
urethane resin adhesives, and cyanoacrylate adhesives.
[1072] The fixing configuration shown in FIG. 50 can be observed by
an optical microscope or electron microscope. Particularly
preferable is a method including subjecting the sample to an
embedding treatment, then forming a cross-section by a microtome,
and observing the cross-section.
[1073] In the present embodiment, at least a portion of the fixing
member preferably externally grips the membrane and the electrode
for electrolysis. The aspect will be described by use of FIG.
51A.
[1074] The fixing configuration shown in FIG. 51A is a
configuration in which the electrode for electrolysis 2 and
membrane 3 are externally gripped and fixed. That is, the outer
surface 2b of the electrode for electrolysis 2 and the outer
surface 3b of the membrane 3 are sandwiched and fixed by a gripping
member as the fixing member 7 in the fixing configuration shown in
FIG. 51A, a state in which the gripping member is engaging in the
electrode for electrolysis 2 and the membrane 3 is also included.
Examples of the gripping member include tape and clips.
[1075] In the present embodiment, a gripping member that dissolves
in an electrolyte solution may be used. Examples of the gripping
member that dissolves in an electrolyte solution include PET tape
and clips and PVA tape and clips.
[1076] In the fixing configuration shown in FIG. 51A, unlike those
in FIGS. 47 to FIG. 50, the electrode for electrolysis 2 and the
membrane 3 are not bonded at the interface therebetween, but the
inner surface 2a of the electrode for electrolysis 2 and the inner
surface 3a of the membrane 3 are only abutted or opposed to each
other. Removal of the gripping member can release the fixed state
of the electrode for electrolysis 2 and the membrane 3 and separate
the electrode for electrolysis 2 from the membrane 3.
[1077] Although not shown in FIG. 51A, it is also possible to fix
the electrode for electrolysis 2 and the membrane 3 using a
gripping member in an electrolytic cell.
[1078] For example, it is possible to fold PTFE tape back to fix
the membrane and the electrode in a sandwich manner.
[1079] Also in the present embodiment, at least a portion of the
fixing member preferably fixes the membrane and the electrode for
electrolysis by magnetic force. The aspect will be described by use
of FIG. 51B.
[1080] The fixing configuration shown in FIG. 51B is a
configuration in which the electrode for electrolysis 2 and
membrane 3 are externally gripped and fixed. The difference from
that in FIG. 51A is that a pair of magnets are used as the gripping
member, which is the fixing member. In the aspect of the fixing
configuration shown in FIG. 51B, a laminate 1 is attached to the
electrolyzer. Thereafter, during operation of the electrolyzer, the
gripping member may be left as it or may be removed from the
laminate 1.
[1081] Although not shown FIG. 51d, it is also possible to fix the
electrode for electrolysis 2 and the membrane 3 using a gripping
member in an electrolytic cell. When a magnetic material that
adheres to magnets is used as a part of the material for the
electrolytic cell, one gripping material placed on the side of the
membrane surface. Then, the gripping material and the electrolytic
cell car sandwich and fix the electrode for electrolysis 2 and the
membrane 3 therebetween.
[1082] A plurality of fired region lines can be provided. That is,
1, 2, 3, . . . n fixed region lines can be arranged from the side f
the contour toward the inner side of the laminate 1. n is an
integer of 1 or more. The m-th (m<n) fixed region line an the
L-th (m<L.ltoreq.n) fixed region line can be each formed to have
a different fixation pattern.
[1083] A fixed region line to be formed in the electroconductive
portion preferably has a line-symmetric shape. This tends to enable
stress concentration to be controlled. For example, when two
orthogonally intersecting directions are referred to as the X
direction and the Y direction, it is possible to configure the
fixed region by arranging a fixed region line each in the X
direction and the Y direction or arranging a plurality of fixed
region lines at equal intervals each in the X direction and the Y
direction. The number of fixed region lines each in the X direction
and the Y direction is not limited, but is preferably 100 or less
each in the X direction and the Y direction. From the viewpoint of
achieving the planarity of electroconductive portion, the number of
fixed region lines is preferably 50 or less each in the X direction
and the Y direction.
[1084] When the fixed region in the present embodiment has the
fixing configuration shown in FIG. 47A or FIG. 49, a sealing
material is preferably applied onto the membrane surface of the
fixed region from the viewpoint of preventing a short circuit
caused by a contact between the anode and the cathode. As the
sealing material, the materials described for the above adhesives
can be used.
[1085] When a fixing member is used, on determining the area S3 and
the area S3', as for the portion at which the fixing member
overlaps, the overlapping part is not included in the area S3 and
the area S3'. For example, when fixing is made by using the PTFE
yarns mentioned above as the fixing members, the portion at which
the PTFE yarns intersect with each other is not included as an
overlapping part in the area. When fixing is made by using the PTFE
tapes mentioned above as the fixing members, the portion at which
the PTFE tapes intersect with each other is not included as an
overlapping part in the area.
[1086] When fixing is made by using the PTFE yarn or adhesive
mentioned above as the fixing member, the area present on the back
side of the electrode for electrolysis and/or membrane is also
included in the area S3 and area S3'.
[1087] The laminate in the present embodiment may have various
fixed regions in various positions as mentioned above, but the
electrode for electrolysis preferably satisfies the "force applied"
mentioned above particularly in a portion in which no fixed region
is present (non-fixed region). That is, the force applied per
unit-mass unit area of the electrode for electrolysis in the
non-fixed region is preferably less than 1.5 N/mgcm.sup.2.
[Electrolyzes]
[1088] The electrolyzer of the present embodiment includes the
laminate of the present embodiment. Hereinafter, the case of
performing common salt electrolysis by using an ion exchange
membrane as the membrane is taken as an example, and one embodiment
of the electrolyzer will be described in detail.
[Electrolytic Cell]
[1089] FIG. 52 illustrates a cross-sectional view of an
electrolytic cell 1.
[1090] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell 1 has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 56, and the cathode 21 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer may be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support 24, the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[1091] FIG. 53 illustrates a cross-sectional view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
54 shows an electrolyzer 4. FIG. 55 shows a step of assembling the
electrolyzer 4. As shown in FIG. 53, an electrolytic cell 1, a
cation exchange membrane 2, and an electrolytic cell 1 are arranged
in series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 among
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 54, the
electrolyzer 4 is composed of a plurality of electrolytic cells 1
connected in series via the ion exchange membrane 2. That is, the
electrolyzer 4 is a bipolar electrolyzer comprising the plurality
of electrolytic cells 1 arranged in series and ion exchange
membranes 2 each arranged between adjacent electrolytic cells 1. As
shown in FIG. 55, the electrolyzer 4 is assembled by arranging the
plurality of electrolytic cells 1 in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[1092] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged the one
end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[1093] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[1094] The anode chamber 10 has the anode 11 or anode feed
conductor 11. When the electrode for electrolysis in the present
embodiment is inserted to the anode side, 11 serves as the anode
feed conductor. When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, 11 serves as the
anode. The anode chamber 10 has an anode side electrolyte solution
supply unit that supplies an electrolyte solution to the anode
chamber 10, a baffle plate that is arranged above the anode-side
electrolyte solution supply unit so as to be substantially parallel
or oblique to the partition wall 30, and an anode-side gas liquid
separation unit arranged above the baffle plate to separate gas
from the electrolyte solution including the gas mixed.
(Anode)
[1095] When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, the anode 11 is
provided in the frame of the anode chamber 10. As the anode 11, a
metal electrode such as so-called DSA(R) can be used. DSA is an
electrode including a titanium substrate of which surface is
covered with an oxide comprising ruthenium, iridium, and titanium
as components.
[1096] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[1097] When the electrode for electrolysis in the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame or the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatvely, DSA having a thinner catalyst coating can be also
used. Further, a used anode can be also used.
[1098] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[1099] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode and parallel to the bottom 19
of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[1100] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 52, and below means the lower direction
in the electrolytic cell 1 in FIG. 52.
[1101] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 in the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the gas
liquid mixed phase flow passes through the defoaming plate, bubbles
burst to thereby enable the electrolyte solution and the gas to be
separated. As a result, vibration during electrolysis can be
prevented.
(Baffle Plate)
[1102] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[1103] Although not shown in FIG. 52, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[1104] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[1105] In the cathode chamber 20, when the electrode for
electrolysis in the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis in the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[1106] When the electrode for electrolysis in the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20. The cathode 21
preferably has a nickel substrate and a catalyst layer that covers
the nickel substrate. Examples of the components of the catalyst
layer on the nickel substrate include metals such as Ru, C, Si, P,
S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ph, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. The cathode 21 may
be subjected to a reduction treatment, as required. As the
substrate of the cathode 21, nickel, nickel alloys, and
nickel-plated iron or stainless may be used.
[1107] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[1108] When the electrode for electrolysis in the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Nickel, nickel
alloys, and nickel-plated iron or stainless, having no catalyst
coating may be used. As the substrate of the cathode feed conductor
21, nickel, nickel alloys, and nickel-plated iron or stainless may
be used.
[1109] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[1110] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[1111] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[1112] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, and titanium. The
collector 23 may be a mixture, alloy, or composite oxide of these
metals. The collector 23 may have any form as long as the form
enables the function of the collector and may have a plate or net
form.
(Metal Elastic Body)
[1113] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electrolytic cells 1 connected in
series. Lowering of the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis according to the present
embodiment is placed in the electrolytic cell.
[1114] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[1115] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[1116] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[1117] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane (see FIGS. 52 and 53).
These gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[1118] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced gas and be
usable for a long period. Thus, in respect of chemical resistance
and hardness, vulcanized products and peroxide-crosslinked products
of ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 53), each
electrolytic cell 1 onto which the gasket is attached should be
tightened via ion exchange membrane 2. This tightening can prevent
the electrolyte solution, alkali metal hydroxide, chlorine gas,
hydrogen gas, and the like generated from electrolysis from leaking
out of the electrolytic cells 1.
(Ion Exchange Membrane 2)
[1119] The ion exchange membrane 2 is as described in the section
of the ion exchange membrane described above.
(Water Electrolysis)
[1120] The electrolyzer of the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
Fourth Embodiment
[1121] Here, a fourth embodiment of the present invention will be
described in detail with reference to FIGS. 63 to 90.
[Electrolyzer]
[1122] The electrolyzer according to the fourth embodiment
(hereinafter, in the section of <Fourth embodiment>, simply
referred to as "the present embodiment") comprises an anode, an
anode frame that supports the anode, an anode side gasket that is
arranged on the anode frame, a cathode that is opposed to the
anode, a cathode frame that supports the cathode, a cathode side
gasket that is arranged on the cathode frame and is opposed to the
anode side gasket, and a laminate of a membrane and an electrode
for electrolysis, the laminate being arranged between the anode
side gasket and the cathode side gasket, wherein at least a portion
of the laminate is sandwiched between the anode side gasket and the
cathode side gasket, and a ventilation resistance is 24 kPas/m or
less when the electrode for electrolysis has a size of 50
mm.times.50 mm, the ventilation resistance being measured under
conditions of a temperature of 24.degree. C., a relative humidity
of 32%, a piston speed of 0.2 cm/s, and a ventilation volume of 0.4
cc/cm.sup.2/s. As configured described above, the electrolyzer of
the present embodiment has excellent electrolytic performance as
well as can prevent damage of the membrane.
[1123] The electrolyzer of the present embodiment comprises the
constituent members mentioned above, in other words, comprises an
electrolytic cell. Hereinafter, a case of performing common salt
electrolysis by using an ion exchange membrane as the membrane is
taken as an example, and one embodiment of the electrolyzer will be
described in detail.
[Electrolytic Cell]
[1124] First, the electrolytic cell, which can be used as a
constituent unit of the electrolyzer of the present embodiment,
will be described. FIG. 63 illustrates a cross-sectional view of an
electrolytic cell 1.
[1125] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell 1 has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 67, and the cathode 1 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer may be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support 24, the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[1126] FIG. 64 illustrates a cross-sectional view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
65 shows an electrolyzer 4. FIG. 66 shows a step of assembling the
electrolyzer 4.
[1127] In a conventional electrolyzer, as shown in FIG. 64A, an
electrolytic cell 1, a membrane (herein, a cation exchange
membrane) 2, and an electrolytic cell 1 are arranged in series in
the order mentioned. The ion exchange membrane 2 is arranged
between the anode chamber of one electrolytic cell 1 of the two
electrolytic cells that are adjacent in the electrolyzer and the
cathode chamber of the other electrolytic cell 1. That is, in the
electrolyzer, the anode chamber 10 of the electrolytic cell 1 and
the cathode chamber 20 of the electrolytic cell 1 adjacent thereto
are usually separated by the cation exchange membrane 2.
[1128] Meanwhile, the present embodiment, as shown in FIG. 64B, an
electrolytic cell 1, a laminate 25 having a membrane (herein, a
cation exchange membrane) 2, and an electrode for electrolysis
(herein, a cathode for renewal) 21a, and an electrolytic cell 1 are
arranged in series in the order mentioned. The laminate 25, at the
portion thereof (in FIG. 64B, the top end portion), is sandwiched
between an anode gasket 12 and a cathode gasket 13.
[1129] As shown in FIG. 65, the electrolyzer 4 is composed of a
plurality of electrolytic cells 1 connected in series via the ion
exchange membrane 2. That is, the electrolyzer 4 is a bipolar
electrolyzer comprising the plurality of electrolytic cells 1
arranged in series and ion exchange membranes 2 each arranged
between adjacent electrolytic cells 1. As shown in FIG. 66, the
electrolyzer 4 is assembled by arranging the plurality of
electrolytic cells 1 connected in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[1130] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[1131] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
[1132] As mentioned above, the characteristics of the membrane,
cathode, and anode in the electrolyzer deteriorate usually in
association with operation of the electrolyzer and replacement by
new ones become required before long. In the case of replacement of
only the membrane, renewing can be easily performed by extracting
the existing membrane between the electrolytic cells and inserting
a new membrane therebetween, but replacement of the anode or the
cathode by means of welding is complicated because a specialized
installation is required.
[1133] Meanwhile, in the present embodiment, the laminate 25, at
the portion thereof (in FIG. 64B, the top end portion), is
sandwiched between an anode gasket 12 and a cathode gasket 13, as
described above. Particularly in the example shown in FIG. 64B, the
membrane (herein, the cation exchange membrane) 2 and the electrode
for electrolysis (herein, the cathode for renewal) 21a can be fixed
in at least the top end portion of the laminate by pressing in the
direction from the anode gasket 12 toward the laminate 25 and
pressing in the direction from the cathode gasket 13 toward the
laminate 25. This case is preferable because it is not necessary to
fix the laminate 25 (in particular, the electrode for electrolysis)
on the existing member (e.g., the existing cathode) by welding.
That is, the case where both the electrode for electrolysis and the
membrane are sandwiched between the anode side gasket and the
cathode side gasket is preferable because the work efficiency
during electrode renewing in the electrolyzer tends to be
improved.
[1134] Further, in accordance with the configuration of the
electrolyzer of the present embodiment, the membrane and the
electrode for electrolysis are sufficiently fixed as the laminate,
and thus, excellent electrolytic performance can be achieved.
(Anode Chamber)
[1135] The anode chamber 10 has the anode 11 or anode feed
conductor 11. The feed conductor herein referred to means a
degraded electrode (i.e., the existing electrode), an electrode
having no catalyst coating, and the like. When the electrode for
electrolysis in the present embodiment is inserted to the anode
side, 11 serves as an anode feed conductor. When the electrode for
electrolysis the present embodiment is not inserted to the anode
side, 11 serves as an anode. The anode chamber 10 preferably has an
anode-side electrolyte solution supply unit that supplies an
electrolyte solution to the anode chamber 10, a baffle plate that
is arranged above the anode-side electrolyte solution supply unit
so as to be substantially parallel or oblique to a partition wall
30, and an anode-side gas liquid separation unit that is arranged
above the baffle plate to separate gas from the electrolyte
solution including the gas mixed.
(Anode)
[1136] When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, an anode 11 is
provided in the frame of the anode chamber 10 (i.e., the anode
frame). As the anode 11, a metal electrode such as so-called DSA(R)
can be used. DSA is an electrode including a titanium substrate of
which surface is covered with an oxide comprising ruthenium,
iridium, and titanium as components.
[1137] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[1138] When the electrode for electrolysis in the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having thinner catalyst coating can be also
used. Further, a used anode can be also used.
[1139] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[1140] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[1141] The anode-side gas liquid separation unit is Preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 63, and below means the lower direction
in the electrolytic cell 1 in FIG. 63.
[1142] During electrolysis, produced gas generated in the
electrolytic cell and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 in the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle Plate)
[1143] The baffle plate preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electro solution (brine or
the like) to circulate internally in the anode chamber 10 to
thereby make the concentration uniform. In order to cause internal
circulation, the baffle plate is preferably arranged so as to
separate the space in proximity to the anode 11 from the space in
proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[1144] Although not shown in FIG. 63, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[1145] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[1146] In the cathode chamber 20, when the electrode for
electrolysis in the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis in the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[1147] When the electrode for electrolysis in the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20 (i.e., the cathode
frame). The cathode 21 preferably has a nickel substrate and a
catalyst layer that covers the nickel substrate. Examples of the
components of the catalyst layer on the nickel substrate include
metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,
Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb, and Lu, and oxides and hydroxides of the metals. Examples of
the method for forming the catalyst layer include plating, alloy
plating, dispersion/composite plating, CVD, PVC, pyrolysis, and
spraying. These methods may be used in combination. The catalyst
layer may have a plurality of layers and a plurality of elements,
as required. The cathode 21 may be subjected to a reduction
treatment, as required. As the substrate of the cathode 21, nickel,
nickel alloys, and nickel-plated iron or stainless may be used.
[1148] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[1149] When the electrode for electrolysis in the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Nickel, nickel
alloys, and nickel-plated iron or stainless, having no catalyst
coating may be used. As the substrate of the cathode feed conductor
21, nickel, nickel alloys, and nickel-plated iron or stainless may
be used.
[1150] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[1151] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[1152] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[1153] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[1154] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electrolytic cells 1 connected in
series. Lowering of the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis in the present embodiment
is placed in the electrolytic cell.
[1155] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[1156] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[1157] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[1158] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the laminate 25 (see FIG. 64B). These gaskets can
impart airtightness to connecting points when the plurality of
electrolytic cells 1 is connected in series via the laminate
25.
[1159] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced gas and be
usable for a long period. Thus, in respect of chemical resistance
and hardness, vulcanized products and peroxide-crosslinked products
of ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Sandwiching the laminate 25 by the anode gasket and cathode
gasket can prevent the electrolyte solution, alkali metal
hydroxide, chlorine gas, hydrogen gas, and the like generated from
electrolysis from leaking out of the electrolytic cells 1.
[Laminate]
[1160] The laminate in the present embodiment comprises a membrane
and an electrode for electrolysis. The laminate in the present
embodiment can improve the work efficiency during electrode
renewing an electrolyzer and further, can exhibit excellent
electrolytic performance also after renewing. That is, according to
the laminate in the present embodiment, on renewing the electrode,
the electrode can be renewed by a work as simple as renewing the
membrane without a complicated work such as stripping off the
existing electrode fixed on the electrolytic cell, and thus, the
work efficiency is markedly improved.
[1161] Further, according to the laminate in the present
embodiment, it is possible to maintain the electrolytic performance
of the existing electrolytic cell comparable to those of a new
electrode or improve the electrolytic performance. Thus, the
electrode fixed on the existing electrolytic cell and serving as
the anode or cathode is only required to serve as a feed conductor.
Thus, it is also possible to markedly reduce or eliminate catalyst
coating.
[Electrode for Electrolysis]
[1162] In the electrode for electrolysis in the present embodiment,
the ventilation resistance is 24 kPas/m or less when the electrode
for electrolysis has a size of 50 mm.times.50 mm, the ventilation
resistance being measured under conditions of the temperature of
24.degree. C., the relative humidity of 32%, a piston speed of 0.2
cm/s, and a ventilation volume of 0.4 cc/cm.sup.2/s (hereinbelow,
also referred to as "measurement condition 1") (hereinbelow, also
referred to as "ventilation resistance 1"). A larger ventilation
resistance means that air is unlikely to flow and refers to a state
of a high density. In this state, the product from electrolysis
remains in the electrode and a reaction substrate is more unlikely
to diffuse inside the electrode, and thus, the electrolytic
performance (such as voltage) deteriorates. The concentration on
the membrane surface increases. Specifically, the caustic
concentration increases on the cathode surface, and the supply of
brine decreases on the anode surface. As a result, the product
accumulates at a high concentration on the interface at which the
membrane is in contact with the electrode. This accumulation leads
to damage of the membrane and also leads to increase in the voltage
and damage of the membrane on the cathode surface and damage of the
membrane on the anode surface. In the present embodiment, in order
to prevent these defects, the ventilation resistance is set at 24
kPas/m or less.
[1163] In the present embodiment, when the ventilation resistance
is larger than a certain value, NaOH generated in the electrode
tends to accumulate on the interface between the electrode and
membrane to result in a high concentration in the case of the
cathode, and the supply of brine tends to decrease to cause the
brine concentration to be lower in the case of the anode. In order
to prevent damage to the membrane that may be caused by such
accumulation, the ventilation resistance is preferably less than
0.19 kPas/m, more preferably 0.15 kPas/m or less, further
preferably 0.07 kPas/m or less.
[1164] In contrast, when the ventilation resistance is low, the
area of the electrode becomes smaller, and the electroconductive
area is reduced. Thus, the electrolytic performance (such as
voltage) deteriorates. When the ventilation resistance is zero, the
feed conductor functions as the electrode because no electrode for
electrolysis is provided and the electrolytic performance (such as
voltage) markedly deteriorates. From this viewpoint, a preferable
lower limit value identified as the ventilation resistance 1 is not
particularly limited, but is preferably more than 0 kPas/m, more
preferably 0.0001 kPas/m or more, further preferably 0.001 kPas/m
or more.
[1165] When the ventilation resistance 1 is 0.07 kPas/m or less, a
sufficient measurement accuracy may not be achieved because of the
measurement method therefor. From this viewpoint, it is also
possible to evaluate an electrode for electrolysis having a
ventilation resistance 1 of 0.07 kPas/m or less by means of a
ventilation resistance (hereinbelow, also referred to as
"ventilation resistance 2") obtained by the following measurement
method (hereinbelow, also referred to as "measurement condition
2"). That is, the ventilation resistance 2 is a ventilation
resistance measured, when the electrode for electrolysis has a size
of 50 mm.times.50 mm, under conditions of the temperature of
24.degree. C., the relative humidity of 32%, a piston speed of 2
cm/s, and a ventilation volume of 4 cc/cm.sup.2/s.
[1166] The specific methods for measuring the ventilation
resistances 1 and 2 are described in Examples.
[1167] The ventilation resistances 1 and 2 can be within the range
described above by appropriately adjusting an opening ratio,
thickness of the electrode, and the like, for example. More
specifically, for example, when the thickness is constant, a higher
opening ratio tends to lead to smaller ventilation resistances 1
and 2, and a lower opening ratio tends to lead to larger
ventilation resistances 1 and 2.
[1168] The electrode for electrolysis in the present embodiment has
a force applied per unit massunit area of preferably 1.6
N/(mgcm.sup.2) or less, more preferably less than 1.6
N/(mgcm.sup.2), further preferably less than 1.5 N/(mgcm.sup.2),
even further preferably 1.2 N/mgcm.sup.2 or less, still more
preferably 1.20 N/mgcm.sup.2 or less from the viewpoint of enabling
a good handling property to be provided and having a good adhesive
force to a membrane such as an ion exchange membrane and a
microporous membrane, a feed conductor (a degraded electrode and an
electrode having no catalyst coating), and the like. The force
applied is even still more preferably 1.1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[1169] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0.2 N/(mgcm.sup.2) or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1170] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[1171] The mass per unit is preferably 48 mg/cm.sup.2 or less, more
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and of economy, and furthermore is preferably 15 mg/cm.sup.2 or
less from the comprehensive viewpoint including handling property,
adhesion, and economy. The lower limit value is not particularly
limited but is of the order of 1 mg/cm.sup.2, for example.
[1172] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[1173] The force applied can be measured by methods (i) or (ii)
described below, which are as detailed in Examples. As for the
force applied, the value obtained by the measurement of the method
(i) (also referred to as "the force applied (1)") and the value
obtained by the measurement of the method (ii) (also referred to as
"the force applied (2)") may be the same or different, and either
of the values is preferably less than 1.5 N/mgcm.sup.2.
[Method (i)]
[1174] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. The arithmetic average surface roughness
(Ra) of the nickel plate after the blast treatment is 0.5 to 0.8
.mu.m. The specific method for calculating the arithmetic average
surface roughness (Ra) is as described in Examples.
[1175] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode in
this sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[1176] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[1177] The force applied per unit massunit area (1) obtained by the
method is preferably 1.6 N/(mgcm.sup.2) or less, more preferably
less than 1.6 N/(mgcm.sup.2), further preferably less than 1.5
N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2 or less,
still more preferably 1.20 N/mgcm.sup.2 or less from the viewpoint
of enabling a good handling property to be provided and having a
good adhesive force to a membrane such as an ion exchange membrane
and a microporous membrane, a degraded electrode, and a feed
conductor having no catalyst coating. The force applied is even
still more preferably 1.1 N/mgcm.sup.2 or less, further still more
preferably 1.10 N/mgcm.sup.2 or less, particularly preferably 1.0
N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2 or
less. The force is preferably more than 0.005 N/(mgcm.sup.2), more
preferably 0.08 N/(mgcm.sup.2) or more, further preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of further improving the
electrolytic performance, and furthermore, is further more
preferably 0.14 N/(mgcm.sup.2) still more preferably 0.2
N/(mgcm.sup.2) or more from the viewpoint of further facilitating
handling in a large size (e.g., a size of 1.5 m.times.2.5 m).
[Method (ii)]
[1178] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5% only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[1179] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[1180] The force applied per unit massunit area (2) obtained by the
method (ii) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particular preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. Further, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/(mgcm.sup.2) or more from the viewpoint of
further improving the electrolytic performance, and is further more
preferably 0.14 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1181] The electrode for electrolysis in the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 170 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having no catalyst coating, being capable of being
suitably rolled in a roll and satisfactorily folded, and
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[1182] The proportion measured by the following method (2) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint of further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2)]
[1183] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1184] The proportion measured by the following method (3) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[1185] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1186] The value obtained by measurement by the following method
(A) of the electrode for electrolysis in the present embodiment is
preferably 40 mm or less, more preferably 29 mm or less, further
preferably 19 mm or less from the viewpoint of the handling
property.
[Method (A)]
[1187] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, a sample obtained by laminating an
ion exchange membrane which is obtained by applying inorganic
material particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the details of the ion exchange membrane
referred to herein are as described in Examples) and the electrode
for electrolysis is wound around and fixed onto a curved surface of
a core material being made of polyvinyl chloride and having an
outer diameter .PHI. of 32 mm, and left to stand for 6 hours;
thereafter, when the electrode for electrolysis is separated from
the sample and placed on a flat plate, heights in a vertical
direction at both edges of the electrode for electrolysis L1 and L2
are measured, and an average value thereof is used as a measurement
value.
[1188] The electrode for electrolysis in the present embodiment
preferably has a porous structure and an opening ratio or void
ratio of 5 to 90% or less from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and preventing
accumulation of gas to be generated during electrolysis, although
not particularly limited. The opening ratio is more preferably 10
to 80% or less, further preferably 20 to 75%.
[1189] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V was calculated from the values of the gauge thickness,
width, and length of the electrode, and further, a weight W was
measured to thereby calculate an opening ratio A by the following
formula.
A=(1-(V.times..rho.)).times.100
[1190] .rho. is the density of the electrode material (g/cm.sup.3)
For example, .rho. of nickel 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio can be
appropriately adjusted by changing the area of metal to be
perforated per unit area in the case of perforated metal, changing
the values of the SW (short diameter), LW (long diameter), and feed
in the case of expanded metal, changing the line diameter of metal
fiber and mesh number in the case of mesh, changing the pattern of
a photoresist to be used in the case of electroforming, changing
the metal fiber diameter and fiber density in the case of nonwoven
fabric, changing the mold for forming voids in the case of foamed
metal, or the like.
[1191] Hereinbelow, one aspect of the electrode for electrolysis in
the present embodiment will be described.
[1192] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[1193] As shown in FIG. 68, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[1194] Also shown in FIG. 68, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[1195] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[1196] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[1197] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[1198] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[1199] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[1200] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[1201] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[1202] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[1203] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[1204] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 8
.mu.m.
[1205] Next, a case where the electrode for electrolysis in the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[1206] In FIG. 68, a first layer 20 as a catalyst layer contains at
least one of ruthenium oxides, iridium oxides, and titanium oxides.
Examples of the ruthenium oxide include RuO.sub.2. Examples of the
iridium oxide include IrO.sub.2. Examples of the titanium oxide
include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[1207] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1208] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol or the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1209] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[1210] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[1211] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[1212] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[1213] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[1214] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[1215] Next, a case where the electrode for electrolysis in the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[1216] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re,
Os, Tr, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,
Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[1217] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[1218] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[1219] As the platinum group metal, platinum is preferably
contained.
[1220] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[1221] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[1222] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[1223] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[1224] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[1225] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[1226] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[1227] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[1228] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[1229] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[1230] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[1231] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[1232] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The curability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[1233] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[1234] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[1235] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[1236] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness is more preferably 0.1 .mu.m to 10 .mu.m. The
thickness is further preferably 0.2 .mu.m to 8 .mu.m.
[1237] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis is
measured in the same manner as the thickness of the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
[1238] In the present embodiment, the electrode for electrolysis
preferably contains at least one catalytic component selected from
the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb,
Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
and Dy from the viewpoint of achieving sufficient electrolytic
performance.
[1239] In the present embodiment, from the viewpoint that the
electrode for electrolysis, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a macroporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness or 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
(Method for Producing Electrode for Electrolysis)
[1240] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[1241] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking or a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, a catalyst layer is formed on the
substrate for electrode for electrolysis by an application step of
applying a coating liquid containing a catalyst, a drying step of
drying the coating liquid, and a pyrolysis step of performing
pyrolysis. Pyrolysis herein means that a metal salt which is to be
a precursor is decomposed by heating into a metal or metal oxide
and a gaseous substance. The decomposition product depends on the
metal species to be used, type of the salt, and the atmosphere
under which pyrolysis is performed, and many metals tend to form
oxides in an oxidizing atmosphere. In an industrial process of
producing an electrode, pyrolysis is usually performed in air, and
a metal oxide or a metal hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[1242] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[1243] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[1244] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1245] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable, 5 to 20 minutes more preferable.
[1246] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[1247] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[1248] The first layer 20 obtained by applying a solution in which
metal salts of various combination are dissolved (first coating
liquid) onto the substrate for electrode for electrolysis and then
pyrolyzing (baking) the coating liquid in the presence of oxygen.
The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[1249] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/m in association with the
thickness of the coating film to be formed by a single coating.
[1250] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1251] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[1252] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and the
further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[1253] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[1254] The first layer 20 can be formed also by ion plating. An
example includes a method in which the substrate is fixed in a
chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[1255] The first layer 20 can be formed also by a plating
method.
[1256] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[1257] The first layer 20 can be formed also by thermal
spraying.
[1258] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[1259] The electrode for electrolysis in the present embodiment can
be integrated with a membrane such as an ion exchange membrane and
a microporous membrane and used. Thus, the laminate in the present
embodiment can be used as a membrane-integrated electrode. Then,
the substituting work for the cathode and anode on renewing the
electrode is eliminated, and the work efficiency is markedly
improved.
[1260] The electrode integrated with the membrane such as an ion
exchange membrane and a microporous membrane can make the
electrolytic performance comparable to or higher than those of a
new electrode.
[1261] Hereinafter, the ion exchange membrane will be described in
detail.
[Ion Exchange Membrane]
[1262] The ion exchange membrane is not particularly limited as
long as the membrane can be laminated with the electrode for
electrolysis, and various ion exchange membranes may be employed.
In the present embodiment, an ion exchange membrane that has a
membrane body containing a hydrocarbon polymer or
fluorine-containing polymer having an ion exchange group and a
coating layer provided on at least one surface of the membrane body
is preferably used. It is preferable that the coating layer contain
inorganic material particles and a binder and the specific surface
area of the coating layer be 0.1 to 10 m.sup.2/g. The ion exchange
membrane having such a structure has a small influence of gas
generated during electrolysis on electrolytic performance and tends
to exert stable electrolytic performance.
[1263] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO.sub.3--, hereinbelow also
referred to as a "sulfonic acid group" or a carboxylic acid layer
having an ion exchange group derived from a carboxyl group (a group
represented by --CO.sub.2--, hereinbelow also referred to as a
"carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[1264] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[1265] FIG. 69 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-containing polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[1266] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by hereinbelow also
referred to as a "sulfonic acid group") and a carboxylic acid layer
2 having an ion exchange group derived from a carboxyl group (a
group represented by --CO.sub.2--, hereinbelow also referred to as
a "carboxylic acid group"), and the reinforcement core materials 4
enhance the strength and dimension stability. The ion exchange
membrane 1, as comprising the sulfonic acid layer 3 and the
carboxylic acid layer 2, is suitably used as an anion exchange
membrane.
[1267] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 69.
(Membrane Body)
[1268] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[1269] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[1270] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[1271] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[1272] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[1273] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.s--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[1274] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[1275] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time or hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[1276] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[1277]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[1278]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[1279]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[1280]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[1281] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[1282] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[1283] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having, a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[1284] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[1285]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[1286]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[1287] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[1288]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[1289]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[1290] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[1291] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[1292] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[1293] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0.5 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[1294] In the membrane body 10 of the ion exchange membrane 1, a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[1295] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer located on the anode
side of the electrolyzer and the carboxylic acid layer 2 located on
the cathode side of the electrolyzer.
[1296] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[1297] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[1298] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[1299] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[1300] The ion exchange membrane preferably has a coating layer on
at least one surface of the membrane body. As shown in FIG. 69, in
the ion exchange membrane 1, coating layers 11a and 11b are formed
on both the surfaces of the membrane body 10.
[1301] The coating layers contain inorganic material particles and
a binder.
[1302] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[1303] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[1304] Here, the average particle size can be measured by a
particle size analyzer ("SALD2200", SHIMADZU CORPORATION).
[1305] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[1306] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides or Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durability, zirconium
oxide particle is more preferable.
[1307] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[1308] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurities such as iron attached to the
surface of the inorganic material particles.
[1309] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[1310] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder of the coating layer.
[1311] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[1312] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[1313] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[1314] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[1315] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contract the ion exchange
membrane can be controlled in the desired range. Such an ion
exchange membrane does not expand or contract more than necessary
during electrolysis and the like and can maintain excellent
dimensional stability for a long term.
[1316] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[1317] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, alkalis, etc., and a
fiber comprising a fluorine-containing polymer is preferable
because long-term heat resistance and chemical resistance are
required.
[1318] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PEA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[1319] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) is preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[1320] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[1321] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[1322] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[1323] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[1324] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[1325] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[1326] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area or surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[1327] FIG. 70 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 70, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[1328] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[1329] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[1330] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[1331] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[1332] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[1333] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[1334] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[1335] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[1336] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[1337] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[1338] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[1339] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[1340] Step (4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[1341] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[1342] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[1343] Hereinafter, each of the steps will be described in
detail.
[1344] Step (1): Step of Producing Fluorine-Containing Polymer
[1345] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[1346] Step (2): Step of Producing Reinforcing Materials
[1347] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[1348] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and comprising polyvinyl alcohol and
the like are also preferred.
[1349] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[1350] Step (3): Step of Film Formation
[1351] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[1352] Examples of the film forming method include the
following:
[1353] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[1354] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[1355] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[1356] Step (4): Step of Obtaining Membrane Body
[1357] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[1358] Preferable examples of the method for forming a membrane
body include (i) a method in which a fluorine-containing polymer
having a carboxylic acid group precursor (e.g., carboxylate
functional group) (hereinafter, a layer comprising the same is
referred to as the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using, a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[1359] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[1360] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property capable sufficiently
retaining the mechanical strength the ion exchange membrane.
[1361] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[1362] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[1363] The method for forming the fourth layer may be a method in
which a fluorine-containing, polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[1364] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[1365] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing, material.
[1366] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that is, projections, on the surface
side composed of the sulfonic acid layer. As a method for forming
such projections, which is not particularly limited, a known method
also can be employed including forming projections on a resin
surface. A specific example of the method is a method of embossing
the surface of the membrane body. For example, the above
projections can be formed by using release paper embossed in
advance when the composite film mentioned above, reinforcing
material, and the like are integrated. In the case where
projections are formed by embossing, the height and arrangement
density of the projections can be controlled by controlling the
emboss shape to be transferred (shape of the release paper).
(5) Hydrolysis Step
[1367] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[1368] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[1369] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[1370] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[1371] The mixed solution preferably contains KOH of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[1372] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[1373] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[1374] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 71(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[1375] FIGS. 71(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[1376] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[1377] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[1378] FIG. 71(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
(6) Application Step
[1379] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[1380] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counterion of the ion exchange
group by (e.g., a fluorine-containing polymer having a carboxyl
group or sulfo group). Thereby, the polymer is more likely to
dissolve in water or ethanol mentioned below, which is
preferable.
[1381] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[1382] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[1383] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[1384] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[1385] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[1386] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example, and is preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[1387] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[1388] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[1389] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[1390] In the present embodiment, the membrane preferably comprises
a first ion exchange resin layer and a second ion exchange resin
layer having an EW (ion exchange capacity) different from that of
the first ion exchange resin layer. Additionally, the membrane
preferably comprises a first ion exchange resin layer and a second
ion exchange resin layer having a functional group different from
that of the first on exchange resin layer. The ion exchange
capacity can be adjusted by the functional group to be introduced,
and functional groups that may be introduced are as mentioned
above.
[1391] In the present embodiment, the portion of the laminate 25 to
be sandwiched between the anode gasket 12 and the cathode gasket 13
is preferably a non-conducting surface. The "conducting surface"
corresponds to a portion designed so as to allow electrolytes to
migrate between the anode chamber and the cathode chamber, and the
"non-conducting surface" is a portion not corresponding to the
conducting surface.
[1392] In the present embodiment, the outermost perimeter of the
laminate may be located on a more inner side or farther outside
than the outermost perimeter of the anode side gasket and the
cathode side gasket in the direction of the conducting surface, but
is preferably located farther outside. In the case of such a
configuration, the outermost perimeter located farther outside can
be used as a grip margin, and thus, the workability on assembling
the electrolyzer tends to be improved. The outermost perimeter of
the laminate herein is the outermost perimeter of the membrane and
the electrode for electrolysis in combination. That is, when the
outermost perimeter of the electrode for electrolysis is located
farther outside of the mutual contact surface than the outermost
perimeter of the membrane, the outermost perimeter of the laminate
means the outermost perimeter of the electrode for electrolysis. In
contrast, when the outermost perimeter of the electrode for
electrolysis is located on a more inner side of the mutual contact
surface than the outermost perimeter of the membrane, the outermost
perimeter of the laminate means the outermost perimeter of the
membrane.
[1393] The positional relation will be described by use of FIGS. 72
and 73. FIGS. 72 and 73 particularly show the positional relation
of the gaskets and the laminate when the two electrolytic in shown
in FIG. 64B, for example, are observed from the .alpha.-direction.
In FIGS. 72 and 73, a rectangular gasket A having an aperture
portion at the center is located at the most front side. A
rectangular membrane B is located at the back of A, and a
rectangular electrode for electrolysis C is further located at the
back of B. That is, the aperture portion of the gasket A is a
portion corresponding to the conducting surface of the
laminate.
[1394] In FIG. 72, the outermost perimeter A1 of the gasket A is
located on a more inner side than the outermost perimeter B1 of the
membrane B and the outermost perimeter C1 of the electrode for
electrolysis C in the direction of the conducting surface.
[1395] In FIG. 73, the outermost perimeter A1 of the gasket A is
located farther outs than the outermost perimeter C1 of the
electrode for electrolysis C in the direction of the conducting
surface, but the outermost perimeter B1 of the membrane B is
located farther outside than the outermost perimeter A1 of the
gasket A in the direction of the conducting surface.
[1396] In the present embodiment, the laminate should be sandwiched
between the anode side gasket and the cathode side gasket, and the
electrode for electrolysis per se may not be sandwiched directly
between the anode side gasket and the cathode side gasket. That is,
as long as the electrode for electrolysis per se is fixed to the
membrane, only the membrane may be sandwiched directly between the
anode side gasket and the cathode side gasket. In the present
embodiment, from the viewpoint of more stably fixing the electrode
for electrolysis in the electrolyzer, both the electrode for
electrolysis and the membrane are preferably sandwiched between the
anode side gasket and the cathode side gasket.
[1397] In the present embodiment, the membrane and the electrode
for electrolysis are fixed by at least the anode gasket and the
cathode gasket to exist as a laminate, but may take other fixing
configuration. For example, a fixing configuration exemplified
below may be employed. Only one fixing configuration can be
employed, or two or more fixing configurations can be employed in
combination.
[1398] In the present embodiment, at least a portion of the
electrode for electrolysis preferably penetrates the membrane and
thereby is fixed. The aspect will be described by use of FIG.
74A.
[1399] In FIG. 74A, at least a portion of the electrode for
electrolysis 2 penetrates the membrane 3 and thereby is fixed. FIG.
74A shows an example in which the electrode for electrolysis 2 is a
metal porous electrode. That is, in FIG. 74A, a plurality of
portions of the electrode for electrolysis 2 are separately shown,
but these portions are continuous. Thus, the cross-section of an
integral metal porous electrode is shown (the same apples to FIGS.
75 to 78 below).
[1400] In the electrode configuration, when the membrane 3 in the
predetermined position (position to be the fixed portion), for
example, is pressed onto the electrode for electrolysis 2, a
portion of the membrane 3 intrudes into the asperity geometry or
opening geometry on the surface of the electrode for electrolysis
2. Then, recesses on the electrode surface and projections around
openings penetrate the membrane 3 and preferably penetrate through
to the outer surface 3b of the membrane 3, as shown in FIG.
74A.
[1401] As described above, the fixing configuration in FIG. 74A can
be produced by pressing the membrane 3 onto the electrode for
electrolysis 2. In this case, the membrane 3 is softened by warming
and then subjected to thermal compression and thermal suction.
Then, the electrode for electrolysis 2 penetrates the membrane 3.
Alternatvely, the membrane 3 may be used in a melt state. In this
case, the membrane is preferably suctioned from the side of the
outer surface 2b (back surface side) of the electrode for
electrolysis 2 in the state shown in FIG. 74B. The region in which
the membrane 3 is pressed onto the electrode for electrolysis 2
constitutes the "fixed portion".
[1402] The fixing configuration shown in FIG. 74A can be observed
by a magnifier (loupe), optical microscope, or electron microscope.
Since the electrode for electrolysis 2 has penetrated the membrane
3, it is possible to estimate the fixing configuration in FIG. 74A
by a test of the conduction between the outer surface 3b of the
membrane 3 and the outer surface 2b of the electrode for
electrolysis 2 by use of a tester or the like.
[1403] In the present embodiment, at least a portion of the
electrode for electrolysis is located and fixed inside the membrane
in the fixed portion. The aspect will be described by use of FIG.
75A.
[1404] As described above, the surface of the electrode for
electrolysis 2 has an asperity geometry or opening geometry. In the
embodiment shown in FIG. 75A, a portion of the electrode surface
enters the membrane 3 in the predetermined position (position to be
the fixed portion) and is fixed thereto. The configuration shown in
FIG. 75A can be produced by pressing the membrane 3 onto the
electrode for electrolysis 2. In this case, the fixing
configuration in FIG. 75A is preferably formed by softening the
membrane 3 by warming and then thermally compressing and thermally
suctioning the membrane 3. Alternatively, the fixing configuration
in FIG. 75A can be formed by melting the membrane 3. In this case,
the membrane 3 is preferably suctioned from the side of the outer
surface 2b (back surface side) of the electrode for electrolysis
2.
[1405] The fixing configuration shown in FIG. 75A can be observed
by a magnifier (loupe), optical microscope, or electron microscope.
Particularly preferable is a method including subjecting the sample
to an embedding treatment, then forming a cross-section by a
microtome, and observing the cross-section. In the fixing
configuration shown in FIG. 75A, the electrode for electrolysis 2
does not penetrate the membrane 3. Thus, no conduction between the
outer surface 3b of the membrane 3 and the outer surface 2b of the
electrode for electrolysis 2 is identified by the conduction
test.
[1406] In the present embodiment, it is preferable that the
laminate further have a fixing member for fixing the membrane and
the electrode for electrolysis. The aspect will be described by use
of FIGS. 76A to C.
[1407] The fixing configuration shown FIG. 76A is a configuration
in which a fixing member 7, which is separate from the electrode
for electrolysis 2 and the membrane 3, is used and the fixing
member 7 penetrates and thereby fixes the electrode for
electrolysis 2 and the membrane 3. The electrode for electrolysis 2
is not necessarily penetrated by the fixing member 7, and should be
fixed by the fixing member 7 so as not to be separated from the
membrane 2. The material for the fixing member 7 is not
particularly limited, and materials constituted by metal, resin, or
the like, for example, can be used as the fixing member 7. Examples
of the metal include nickel, nichrome, titanium, and stainless
steel (SUS). Oxides thereof may be used. Examples of the resin that
can be used include fluorine resins (e.g., polytetrafluoroethylene
(PTFE), copolymers of tetrafluoroethylene and perfluoroalkoxy
ethylene (PFA), copolymers of tetrafluoroethylene and ethylene
(ETFE), materials for the membrane 3 described below),
polyvinylidene fluoride (PVDF), ethylene-propylene-diene rubber
(EPDM), polyethylene (PP), polypropylene (PE), nylon, and
aramid.
[1408] In the present embodiment, for example, a yarn-like metal or
resin is used to sew the predetermined position (position to be the
fixed portion) between the outer surface 2b of the electrode for
electrolysis 2 and the outer surface 3b of the membrane 3, as shown
in FIGS. 76B and C. It is also possible to fix the electrode for
electrolysis 2 to the membrane 3 by use of a fixing mechanism such
as a tucker.
[1409] The fixing configuration shown in FIG. 77 is a configuration
in which fixing is made by an organic resin (adhesion layer)
interposed between the electrode for electrolysis 2 and the
membrane 3. That is, in FIG. 77, shown is a configuration in which
an organic resin as the fixing member 7 is arranged on the
predetermined position (position to be the fixed portion) between
the electrode for electrolysis 2 and the membrane 3 to thereby make
fixing by adhesion. For example, the organic resin is applied onto
the inner surface 2a of the electrode for electrolysis 2, the inner
surface 3a of the membrane 3, or one or both of the inner surface
2a of the electrode for electrolysis 2 and the inner surface 3a of
the membrane 3. Then, the fixing configuration shown in FIG. 77 can
be formed by laminating the electrode for electrolysis 2 to the
membrane 3. The materials for the organic resin are not
particularly limited, but examples thereof that can be used include
fluorine resins (e.g., PTFE, PFE, and PFPE) and resins similar the
materials constituting the membrane 3 as mentioned above.
Commercially available fluorine-containing adhesives and PTFE
dispersions also can be used as appropriate. Additionally,
multi-purpose vinyl acetate adhesives, ethylene-vinyl acetate
copolymer adhesives, acrylic resin adhesives, .alpha.-olefin
adhesives, styrene-butadiene rubber latex adhesives, vinyl chloride
resin adhesives, chloroprene adhesives, nitrile rubber adhesives,
urethane rubber adhesives, epoxy adhesives, silicone resin
adhesives, modified silicone adhesives, epoxy-modified silicone
resin adhesives, silylated urethane resin adhesives, cyanoacrylate
adhesives, and the like also can be used.
[1410] In the present embodiment, organic resins that dissolve in
an electrolyte solution or dissolve or decompose during
electrolysis may be used. Examples of the resins that dissolve in
an electrolyte solution or dissolve or decompose during
electrolysis include, but are not limited to, vinyl acetate
adhesives, ethylene-vinyl acetate copolymer adhesives, acrylic
resin adhesives, .alpha.-olefin adhesives, styrene-butadiene rubber
latex adhesives, vinyl chloride resin adhesives, chloroprene
adhesives, nitrile rubber adhesives, urethane rubber adhesives,
epoxy adhesives, silicone resin adhesives, modified silicone
adhesives, epoxy-modified silicone resin adhesives, silylated
urethane resin adhesives, and cyanoacrylate adhesives.
[1411] The fixing configuration shown in FIG. 77 can be observed by
an optical microscope or electron microscope. Particularly
preferable is a method including subjecting the sample to an
embedding treatment, then forming a cross-section by a microtome,
and observing the cross-section.
[1412] In the present embodiment, at least a portion of the fixing
member preferably externally grips the membrane and the electrode
for electrolysis. The aspect will be described by use of FIG.
78A.
[1413] The fixing configuration shown in FIG. 78A is a
configuration in which the electrode for electrolysis 2 and
membrane 3 are externally gripped and fixed. That is, the outer
surface 2b of the electrode for electrolysis 2 and the outer
surface 3b of the membrane 3 are sandwiched and fixed by a gripping
member as the fixing member 7. In the fixing configuration shown in
FIG. 78A, a state in which the gripping member is engaging in the
electrode for electrolysis 2 and the membrane 3 is also included.
Examples of the gripping member include tape and clips.
[1414] In the present embodiment, a gripping member that dissolves
in an electrolyte solution may be used. Examples of the gripping
member that dissolves in an electrolyte solution include PET tape
and clips and PVA tape and clips.
[1415] In the fixing configuration shown in FIG. 78A, unlike those
in FIGS. 74 to FIG. 77, the electrode for electrolysis 2 and the
membrane 3 are not bonded at the interface therebetween, but the
inner surface 2a of the electrode for electrolysis 2 and the inner
surface 3a of the membrane 3 are only abutted or opposed to each
other. Removal of the gripping member can release the fixed state
of the electrode for electrolysis 2 and the membrane 3 and separate
the electrode for electrolysis 2 from the membrane 3.
[1416] Although not shown in FIG. 78A, it is also possible to fix
the electrode for electrolysis 2 and the membrane 3 using a
gripping, member in an electrolytic cell.
[1417] Also in the present embodiment, at least a portion of the
fixing member preferably fixes the membrane and the electrode for
electrolysis by magnetic force. The aspect will be described by use
of FIG. 78B.
[1418] The fixing configuration shown in FIG. 78B is a
configuration in which the electrode for electrolysis 2 and
membrane 3 are externally gripped and fixed. The difference from
that in FIG. 78A is that a pair of magnets are used as the gripping
member, which is the fixing member. In the aspect of the fixing
configuration shown in FIG. 78B, a laminate 1 is attached to the
electrolyzer. Thereafter, during operation of the electrolyzer, the
gripping member may be left as it is or may be removed from the
laminate 1.
[1419] Although not shown in FIG. 78B, it is also possible to fix
the electrode for electrolysis 2 and the membrane 3 using a
gripping member in an electrolytic cell. When a magnetic material
that adheres to magnets is used as a part of the mater al for the
electrolytic cell, one gripping material is placed on the side of
the membrane surface. Then, the gripping material and the
electrolytic cell can sandwich and fix the electrode for
electrolysis 2 and the membrane 3 therebetween.
[1420] A plurality of fixed portion lines can be provided. That is,
1, 2, 3, . . . n fixed portion lines can be arranged from the side
f the contour toward the inner side of the laminate 1. n is an
integer of 1 or more. The m-th (m<n) fixed portion line and the
L-th (m<L.ltoreq.n) fixed portion line can be each formed to
have a different fixation pattern.
[1421] A fixed portion line to be formed in the conducting surface
preferably has a line-symmetric shape. This tends to enable stress
concentration to be controlled. For example, when two orthogonally
intersecting directions are referred to as the X direction and the
Y direction, it is possible to configure the fixed portion by
arranging a fixed portion line each in the X direction and the Y
direction or arranging a plurality of fixed portion lines at equal
intervals each in the X direction and the Y direction. The number
of fixed portion lines each in the X direction and the Y direction
is not limited, but is preferably 100 or less each in the X
direction and the Y direction. From the viewpoint of achieving the
planarity of conducting surface, the number of fixed portion lines
is preferably 50 or less each in the X direction and the Y
direction.
[1422] When the fixed portion in the present embodiment has the
fixing configuration shown in FIG. 74A or FIG. 76, a sealing
material is preferably applied onto the membrane surface of the
fixed portion from the viewpoint of preventing a short circuit
caused by a contact between the anode and the cathode. As the
sealing material, the materials described for the above adhesives
can be used.
[1423] The laminate in the present embodiment may have various
fixed portions in various positions as mentioned above, but from
the viewpoint of sufficiently achieving electrolytic performance,
these fixed portions are preferably present on the non-conducting
surface.
[1424] The laminate in the present embodiment may have various
fixed portions in various positions as mentioned above, but the
electrode for electrolysis preferably satisfies the "force applied"
mentioned above particularly in a portion in which no fixed portion
is present (non-fixed portion). That is, the force applied per
unitmass unit area of the electrode for electrolysis in the
non-fixed portion is preferably less than 1.5 N/mgcm.sup.2.
[1425] In the present embodiment, it is preferable that the
membrane comprise an ion exchange membrane comprising a surface
layer containing an organic resin and the electrode for
electrolysis be fixed by the organic resin. The organic resin is as
mentioned above and can be formed as the surface layer of the ion
exchange membrane by various known methods.
(Water Electrolysis)
[1426] The electrolyzer of the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
(Method for Producing Electrolyzer and Method for Renewing
Laminate)
[1427] A method for renewing the laminate in the electrolyzer of
the present embodiment has a step of separating the laminate in the
present embodiment from the anode side gasket and the cathode side
gasket to thereby remove the laminate out of the electrolyzer, and
a step of sandwiching a new laminate between the anode side gasket
and the cathode side gasket. The new laminate means the laminate in
the present embodiment, and at least one of the electrode for
electrolysis and the membrane should be new.
[1428] In the step of sandwiching the laminate described above,
from the viewpoint of more stably fixing the electrode for
electrolysis in the electrolyzer, both the electrode for
electrolysis and the membrane are preferably sandwiched between the
anode side gasket and the cathode side gasket.
[1429] Additionally, the method for producing the electrolyzer of
the present embodiment has a step of sandwiching the laminate in
the present embodiment between the anode side gasket and the
cathode side gasket.
[1430] The method for producing the electrolyzer and method for
renewing the laminate of the present embodiment, as configured as
described above, can improve the work efficiency during electrode
renewing in the electrolyzer and further can provide excellent
electrolytic performance also after renewing.
[1431] Also in the step of sandwiching the laminate described
above, from the viewpoint of more stably fixing the electrode for
electrolysis in the electrolyzer, both the electrode for
electrolysis and the membrane are preferably sandwiched between the
anode side gasket and the cathode side gasket.
Fifth Embodiment
[1432] Here, a fifth embodiment of the present invention will be
described in detail with reference to FIGS. 91 to 102.
[Method for Producing Electrolyzer]
[1433] The method for producing an electrolyzer according to the
fifth embodiment (hereinafter, in the section of <Fifth
embodiment>, simply referred to as "the present embodiment") is
a method for producing a new electrolyzer by arranging an electrode
for electrolysis or a laminate of the electrode for electrolysis
and a new membrane in an existing electrolyzer comprising an anode,
a cathode that is opposed to the anode, and a membrane that is
arranged between the anode and the cathode, wherein the electrode
for electrolysis or the laminate, being in a wound body form, is
used. As described above, according to the method for producing an
electrolyzer in accordance with the present embodiment, an
electrode for electrolysis or a laminate of the electrode for
electrolysis and a new membrane, being in a wound body form, is
used. Thus, the electrode for electrolysis or the laminate when
used as a member of the electrolyzer can be downsized for transport
or the like, and the work efficiency during electrode renewing in
the electrolyzer can be improved.
[1434] In the present embodiment, the existing electrolyzer
comprises an anode, a cathode that is opposed to the anode, and a
membrane that is arranged between the anode and the cathode as
constituent members, in other words, comprises an electrolytic
cell. The existing electrolyzer is not particularly limited as long
as comprising the constituent members described above, and various
known configurations may be employed.
[1435] In the present embodiment, a new electrolyzer further
comprises an electrode for electrolysis or a laminate, in addition
to a member that has already served as the anode or cathode in the
existing electrolyzer. That is, the "electrode for electrolysis"
arranged on production of a new electrolyzer serves as the anode or
cathode, and is separate from the cathode and anode in the existing
electrolyzer. In the present embodiment, even in the case where the
electrolytic performance of the anode and/or cathode has
deteriorated in association with operation of the existing
electrolyzer, arrangement of an electrode for electrolysis separate
therefrom enables the characteristics of the anode and/or cathode
to be renewed. In the case where a laminate is used in the present
embodiment, a new ion exchange membrane is arranged in combination,
and thus, the characteristics of the ion exchange membrane, which
have deteriorated in association with operation, can be renewed
simultaneously.
[1436] "Renewing the characteristics" referred to herein means to
have characteristics comparable to the initial characteristics
possessed by the existing electrolyzer before being operated or to
have characteristics higher than the initial characteristics.
[1437] In the present embodiment, the existing electrolyzer is
assumed to be an "electrolyzer that has been already operated", and
the new electrolyzer is assumed to be an "electrolyzer that has not
been yet operated". That is, once an electrolyzer produced as a new
electrolyzer is operated, the electrolyzer becomes "the existing
electrolyzer in the present embodiment". Arrangement of an
electrode for electrolysis or a laminate in this existing
electrolyzer provides "a new electrolyzer of the present
embodiment".
[1438] Hereinafter, a case of performing common salt electrolysis
by using an ion exchange membrane as the membrane is taken as an
example, and one embodiment of the electrolyzer will be described
in detail. In the section of <Fifth embodiment>, unless
otherwise specified, "the electrolyzer the present embodiment"
incorporates both "the existing electrolyzer in the present
embodiment" and "the new electrolyzer in the present
embodiment".
[Electrolytic Cell]
[1439] First, the electrolytic cell, which can be used as a
constituent unit of the electrolyzer in the present embodiment,
will be described. FIG. 91 illustrates a cross-sectional view of an
electrolytic cell 1.
[1440] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required the electrolytic cell 1 has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 95, and the cathode 21 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
placed between the collector 23 and the cathode 21. The support 24
is placed between the collector 23 and the partition wall 30. The
collector 23 is electrically connected to the cathode 21 via the
metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer may be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[1441] FIG. 92 illustrates a cross-sectional view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
93 shows an electrolyzer 4. FIG. 94 shows a step of assembling the
electrolyzer 4.
[1442] As shown in FIG. 92, an electrolytic cell 1, a cation
exchange membrane 2, and an electrolytic cell 1 are arranged in
series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 among
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 93, the
electrolyzer 4 is composed of a plurality of electrolytic cells 1
connected in series via the ion exchange membrane 2. That is, the
electrolyzer 4 is a bipolar electrolyzer comprising the plurality
of electrolytic cells 1 arranged in series and ion exchange
membranes 2 each arranged between adjacent electrolytic cells 1. As
shown in FIG. 94, the electrolyzer 4 is assembled by arranging the
plurality of electrolytic cells 1 in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[1443] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[1444] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[1445] The anode chamber 10 has the anode 11 or anode feed
conductor 11. The feed conductor herein referred to mean a degraded
electrode (i.e., the existing electrode), an electrode having no
catalyst coating, and the like. When the electrode for electrolysis
in the present embodiment is inserted to the anode side, 11 serves
as an anode feed conductor. When the electrode for electrolysis in
the present embodiment is not inserted to the anode side, 11 serves
as an anode. The anode chamber 10 preferably has an anode-side
electrolyte solution supply unit that supplies an electrolyte
solution to the anode chamber 10, a baffle plate that is arranged
above the anode-side electrolyte solution supply unit so as to be
substantially parallel or oblique to a partition wall 30, and an
anode-side gas liquid separation unit that is arranged above the
baffle plate to separate gas from the electrolyte solution
including the gas mixed.
(Anode)
[1446] When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, an anode 11 is
provided in the frame of the anode chamber 10 (i.e., the anode
frame). As the anode 11, a metal electrode such as so-called DSA(R)
can be used. DSA is an electrode including a titanium substrate of
which surface is covered with an oxide comprising ruthenium,
iridium, and titanium as components.
[1447] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called, woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[1448] When the electrode for electrolysis in the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having a thinner catalyst coating can be also
used. Further, a used anode can be also used.
[1449] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[1450] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[1451] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 91, and below means the lower direction
in the electrolytic cell 1 in FIG. 91.
[1452] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 in the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle plate)
[1453] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[1454] Although not shown in FIG. 91, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[1455] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[1456] In the cathode chamber 20, when the electrode for
electrolysis in the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis in the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[1457] When the electrode for electrolysis in the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20 (i.e., cathode
frame). The cathode 21 preferably has a nickel substrate and a
catalyst layer that covers the nickel substrate. Examples of the
components of the catalyst layer on the nickel substrate include
metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,
Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb, and Lu, and oxides and hydroxides of the metals. Examples of
the method for forming the catalyst layer include plating, alloy
plating, dispersion/composite plating, CVD, PVD, pyrolysis, and
spraying. These methods may be used in combination. The catalyst
layer may have a plurality of layers and a plurality of elements,
as required. The cathode 21 may be subjected to a reduction
treatment, as required. As the substrate of the cathode 21, nickel,
nickel alloys, and nickel-plated iron or stainless may be used.
[1458] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[1459] When the electrode for electrolysis in the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mb, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Nickel, nickel
alloys, and nickel-plated iron or stainless, having no catalyst
coating may be used. As the substrate of the cathode feed conductor
21, nickel, nickel alloys, and nickel-plated iron or stainless may
be used.
[1460] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[1461] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[1462] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[1463] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[1464] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electrolytic cells 1 connected in
series. Lowering the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis in the present embodiment
is placed in the electrolytic cell.
[1465] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[1466] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[1467] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[1468] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane (see FIG. 92). These
gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[1469] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced gas and be
usable for a long period. Thus, in respect of chemical resistance
and hardness, vulcanized products and peroxide-crosslinked products
of ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (PPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 92), each
electrolytic cell 1 onto which the gasket is attached should be
tightened via ion exchange membrane 2. This tightening can prevent
the electrolyte solution, alkali metal hydroxide, chlorine gas,
hydrogen gas, and the like generated from electrolysis from leaking
out of the electrolytic cells 1.
[Step of Using Wound Body]
[1470] The wound body in the present embodiment may be the
electrode for electrolysis being in a wound body form, or may be a
laminate of the electrode for electrolysis and a new membrane,
being in a wound body form. In the method for producing an
electrolyzer according to the present embodiment, the wound body is
used. Specific examples of the step of using a wound body include,
but are not limited thereto, include a method in which, first in
the existing electrolyzer, a fixed state of the adjacent
electrolytic cell and ion exchange membrane by means of a press
device is released to provide a gap between the electrolytic cell
and the ion exchange membrane, then, an electrode for electrolysis
being in a wound body form, after its wound state is released, is
inserted into the gap, and the members are coupled again by means
of the press device. In the case where the laminate being in a
wound body form is used, examples of the method include a method in
which, after a gap is formed between the electrolytic cell and the
ion exchange membrane as described above, the existing ion exchange
membrane to be renewed is removed, then, a laminate being in a
wound body form, after its wound state is released, is inserted
into the gap, and the members are coupled again by means of the
press device. By means the method, an electrode for electrolysis or
laminate can be arranged on the surface of the anode or the cathode
of the existing electro and the characteristics of the ion exchange
membrane and the anode and/or cathode can be renewed.
[1471] As described above, in the present embodiment, the step of
using a wound body preferably has a step (B) of releasing the wound
state of a wound body, and after the step (B), more preferably has
a step (C) of arranging an electrode for electrolysis or laminate
on the surface of at least one of the anode and the cathode.
[1472] In the present embodiment, the step of using a wound body
preferably has a step of retaining the electrode for electrolysis
or laminate in a wound state to thereby obtain a wound body. In the
step (A), the electrode for electrolysis or laminate per se may be
wound to form a wound body, or the electrode for electrolysis or
laminate may be wound around a core to form a wound body. As the
core that may be used here, which is not particularly limited, a
member having a substantially cylindrical form and having a size
corresponding to the electrode for electrolysis or laminate can be
used, for example.
[Electrode for Electrolysis]
[1473] In the present embodiment, the electrode for electrolysis is
not particularly limited as long as the electrode is used as a
wound body as mentioned above, that is, is woundable. The electrode
for electrolysis may be an electrode that serves as the cathode in
the electrolyzer or may be an electrode that serves as an anode. As
the material, form, and the like of the electrode for electrolysis,
those suitable for forming a wound body may be appropriately
selected, in consideration of the step of using a wound body, the
configuration of the electrolyzer, and the like in the present
embodiment. Hereinbelow, preferable aspects of the electrode for
electrolysis in the present embodiment will be described, but these
are merely exemplary aspects preferable for forming a wound body.
Electrodes for electrolysis other than the aspects mentioned below
can be appropriately employed.
[1474] The electrode for electrolysis in the present embodiment has
a force applied per unit massunit area of preferably 1.6
N/(mgcm.sup.2) or less, more preferably less than 1.6
N/(mgcm.sup.2), further preferably less than 1.5 N/(mgcm.sup.2),
even further preferably 1.2 N/mgcm.sup.2 or less, still more
preferably 1.20 N/mgcm.sup.2 or less from the viewpoint of enabling
a good handling property to be provided and having a good adhesive
force to a membrane such as an ion exchange membrane and a
macroporous membrane, a feed conductor (a degraded electrode and an
electrode having no catalyst coating), and the like. The force
applied is even still more preferably 1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[1475] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0. 2 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1476] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[1477] The mass per unit is preferably 48 mg/cm.sup.2 or less, more
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and of economy, and furthermore is preferably 15 mg/cm.sup.2 or
less from the comprehensive viewpoint including handling property,
adhesion, and economy. The lower limit value is not particularly
limited but is of the order of 1 mg/cm.sup.2, for example.
[1478] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant a higher opening ratio tends to lead to a smaller mass per
unit area, and a lower opening ratio tends to lead to a larger mass
per unit area.
[1479] The force applied can be measured by methods (i) or (ii)
described below, which are as detailed in Examples. As for the
force applied, the value obtained by the measurement of the method
(i) (also referred to as "the force applied (1)") and the value
obtained by the measurement of the method (ii) (also referred to as
"the force applied (2)") may be the same or different, and either
of the values preferably less than 1.5 N/mgcm.sup.2.
[Method (i)]
[1480] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. The arithmetic average surface roughness
(Ra) of the nickel plate after the blast treatment is 0.5 to 0.8
.mu.m. The specific method for calculating the arithmetic average
surface roughness (Ra) is as described in Examples.
[1481] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode in
this sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[1482] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[1483] The force applied per unit massunit area (1) obtained by the
method (i) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. The force is preferably more than 0.005 N/(mgcm.sup.2),
more preferably 0.08 N/(mgcm.sup.2) or more, further preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of further improving the
electrolytic performance, and furthermore, is further more
preferably 0.14 N/(mgcm.sup.2), still more preferably 0.2
N/(mgcm.sup.2) or more from the viewpoint of further facilitating
handling in a large size (e.g., a size of 1.5 m.times.2.5 m.).
[Method (ii)]
[1484] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method. (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[1485] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[1486] The force applied per unit massunit area (2) obtained by the
method (ii) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. Further, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.02 N/(mgcm.sup.2) or more,
further preferably 0.1 N/(mgcm.sup.2) or more from the viewpoint of
further improving the electrolytic performance, and is further more
preferably 0.14 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1487] The electrode for electrolysis in the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 120 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having no catalyst coating, being capable or being
suitably rolled in a roll and satisfactorily folded, and
facilitating, handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 more preferably 15 .mu.m.
[1488] The proportion measured by the following method (2) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint of further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2) ]
[1489] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1490] The proportion measured by the following method (3) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[1491] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1492] The electrode for electrolysis in the present embodiment
preferably has, but is not particularly limited to, a porous
structure and an opening ratio or void ratio of 5 to 90% or less,
from the viewpoint of enabling a good handling property to be
provided, having a good adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode
(feed conductor), and an electrode (feed conductor) having no
catalyst coating, and preventing accumulation of gas to be
generated during electrolysis. The opening ratio is more preferably
10 to 80% or less, further preferably 20 to 75%.
[1493] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V is calculated from the values of the gauge thickness,
width, and length of electrode, and further, a weight W is measured
to thereby enable an opening ratio A to be calculated by the
following formula.
A=(1-(W/(V.times..rho.)).times.100
[1494] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio can be
appropriately adjusted by changing the area of metal to be
perforated per unit area in the case of perforated metal, changing
the values of the SW (short diameter), LW (long diameter), and feed
in the case of expanded metal, changing the line diameter of metal
fiber and mesh number in the case of mesh, changing the pattern of
a photoresist to be used in the case of electroforming, changing
the metal fiber diameter and fiber density in the case of nonwoven
fabric, changing the mold for forming voids in the case of foamed
metal, or the like.
[1495] Hereinbelow, a more specific embodiment of the electrode for
electrolysis in the present embodiment will be described.
[1496] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[1497] As shown in FIG. 96, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[1498] Also shown in FIG. 96, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[1499] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[1500] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[1501] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[1502] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[1503] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[1504] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[1505] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[1506] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[1507] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[1508] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 further preferably 0.1 to 8
.mu.m.
[1509] Next, a case where the electrode for electrolysis in the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[1510] In FIG. 96, a first layer 20 as a catalyst layer contains at
least one of ruthenium oxides, iridium oxides, and titanium oxides.
Examples of the ruthenium oxide include RuO.sub.2. Examples of the
iridium oxide include IrO.sub.2. Examples of the titanium oxide
include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[1511] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1512] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol of the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1513] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[1514] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[1515] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[1516] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[1517] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[1518] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[1519] Next, a case where the electrode for electrolysis in the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[1520] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[1521] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[1522] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[1523] As the platinum group metal, platinum is preferably
contained.
[1524] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[1525] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[1526] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[1527] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[1528] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[1529] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[1530] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[1531] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium +neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[1532] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[1533] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[1534] As the second component, a transition metal may he added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[1535] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[1536] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The durability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[1537] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[1538] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Yb, and Lu, and oxides and hydroxides of the
metals.
[1539] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[1540] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off the substrate.
The thickness is more preferably 0.05 .mu.m to 15 .mu.m. The
thickness is more preferably 0.1 .mu.m to 10 .mu.m. The thickness
is further preferably 0.2 .mu.m to 8 .mu.m.
[1541] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness is preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis is
measured in the same manner as the thickness the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
[1542] In the present embodiment, the electrode for electrolysis
preferably contains at least one catalytic component selected from
the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb,
Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
and Dy from the viewpoint of achieving sufficient electrolytic
performance.
[1543] In the present embodiment, from the viewpoint that the
electrode for electrolysis, if being an electrode having a broad
elastic deformation region can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness of 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
(Method for Producing Electrode for Electrolysis)
[1544] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[1545] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking of a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, a catalyst layer is formed on the
substrate for electrode for electrolysis by an application step of
applying a coating liquid containing a catalyst, a drying step of
drying the coating liquid, and a pyrolysis step of performing
pyrolysis. Pyrolysis herein means that a metal salt which is to be
a precursor is decomposed by heating into a metal or metal oxide
and a gaseous substance. The decomposition product depends on the
metal species to be used, type of the salt, and the atmosphere
under which pyrolysis is performed, and many metals tend to form
oxides in an oxidizing atmosphere. In an industrial process of
producing an electrode, pyrolysis is usually performed in air, and
a metal oxide or a metal hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[1546] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[1547] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[1548] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1549] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable, 5 to 20 minutes is more preferable.
[1550] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and the
further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[1551] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[1552] The first layer 20 is obtained by applying a solution in
which metal salts of various combination are dissolved (first
coating liquid) onto the substrate for electrode for electrolysis
and then pyrolyzing (baking) the coating liquid in the presence of
oxygen. The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[1553] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[1554] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1555] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 0.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[1556] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[1557] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[1558] The first layer 20 can be formed also by ion plating. An
example includes a method in which the substrate is fixed in a
chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[1559] The first layer 20 can be formed also by a plating
method.
[1560] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[1561] The first layer 20 can be formed also by thermal
spraying.
[1562] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[Laminate]
[1563] The electrode for electrolysis in the present embodiment can
be combined with a membrane such as an ion exchange membrane or a
microporous membrane and used as a laminate. That is, the laminate
in the present embodiment comprises the electrode for electrolysis
and a new membrane. The new membrane is not particularly limited as
long as being separate from the membrane in the existing
electrolyzer, and various known "membranes" can be used. The
material, form, physical properties, and the like of the new
membrane may be similar to those of the membrane in the existing
electrolyzer.
[1564] Hereinafter, an ion exchange membrane according to one
aspect of the membrane will be described in detail.
[Ion Exchange Membrane]
[1565] The ion exchange membrane is not particularly limited as
long as the membrane can be laminated with the electrode for
electrolysis, and various ion exchange membranes may be employed.
In the present embodiment, an ion exchange membrane that has a
membrane body containing a hydrocarbon polymer or
fluorine-containing polymer having an ion exchange group and a
coating layer provided on at least one surface of the membrane body
is preferably used. It is preferable that the coating layer contain
inorganic material particles and a binder and the specific surface
area of the coating layer be 0.1 to 10 m.sup.2/g. The ion exchange
membrane having such a structure has a small influence of gas
generated during electrolysis on electrolytic performance and tends
to exert stable electrolytic performance.
[1566] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO--, hereinbelow also
referred to as a "sulfonic acid group") or a carboxylic acid layer
having an ion exchange group derived from a carboxyl group (a group
represented by --CO.sub.2--, hereinbelow also referred to as a
"carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[1567] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[1568] FIG. 97 illustrates a cross-sectional schematic view showing
one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-containing polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[1569] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by --SO.sub.3--,
hereinbelow also referred to as a "sulfonic acid group") and a
carboxylic acid layer 2 having an ion exchange group derived from a
carboxyl group (a group represented by --CO.sub.2--, hereinbelow
also referred to as a "carboxylic acid group"), and the
reinforcement core materials 4 enhance the strength and dimension
stability. The ion exchange membrane as comprising the sulfonic
acid layer 3 and the carboxylic acid layer 2, is suitably used as
an anion exchange membrane.
[1570] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 97.
(Membrane Body)
[1571] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[1572] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[1573] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing, polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[1574] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[1575] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[1576] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.2--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[1577] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[1578] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time of hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[1579] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[1580]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[1581]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[1582]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[1583]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[1584] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[1585] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[1586] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[1587] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[1588]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[1589]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[1590] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[1591]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[1592]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[1593] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[1594] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[1595] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[1596] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0.5 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[1597] In the membrane body 10 of the ion exchange membrane a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[1598] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer 2 is
located on the cathode side of the electrolyzer.
[1599] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[1600] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[1601] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained, by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[1602] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[1603] The ion exchange membrane preferably has a coating layer on
at least one surface of the membrane body. As shown in FIG. 97, in
the ion exchange membrane 1, coating layers 11a and 11b are formed
on both the surfaces of the membrane body 10.
[1604] The coating layers contain inorganic material particles and
a binder.
[1605] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[1606] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[1607] Here, the average particle size can be measured by a
particle size analyzer ("SALD2200", SHIMADZU CORPORATION).
[1608] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[1609] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides of Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durabilty, zirconium
oxide particle is more preferable.
[1610] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[1611] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurites such as iron attached to the surface
of the inorganic material particles.
[1612] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[1613] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing acid fluorine-containing polymer having a
carboxylic acid group (carboxylic acid layer), a
fluorine-containing polymer having a carboxylic acid group is
further preferably used as the binder of the coating layer.
[1614] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[1615] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer preferably 0.5 to 2
mg per 1 cm.sup.2.
[1616] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[1617] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[1618] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contraction of the ion
exchange membrane can be controlled in the desired range. Such an
ion exchange membrane does not expand or contract more than
necessary during electrolysis and the like and can maintain
excellent dimensional stability for a long term.
[1619] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[1620] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, etc., and a fiber
comprising a fluorine-containing polymer is preferable because
long-term heat resistance and chemical resistance are required.
[1621] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[1622] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more prof crab 50 to 250 deniers. The
weave density (fabric count per unit length) preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[1623] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[1624] The weave and arrangement the reinforcement core materials
in the membrane body are not particularly limited, and preferred
arrangement can be appropriately provided considering the size and
form of the ion exchange membrane, physical properties desired for
the ion exchange membrane, the use environment, and the like.
[1625] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[1626] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[1627] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[1628] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[1629] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area of a surface through which
substances such as ions (an electrolyte solution and cations
contained therein sodium ions)) can pass (B) to the area of either
one surface of the membrane body (A) (B/A). The total area of the
surface through which substances such as ions can pass (B) can
refer to the total areas of regions in which in the ion exchange
membrane, cations, an electrolytic solution, and the like are not
blocked by the reinforcement core materials and the like contained
in the ion exchange membrane.
[1630] FIG. 98 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 98, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[1631] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[1632] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[1633] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[1634] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[1635] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[1636] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[1637] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[1638] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[1639] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[1640] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[1641] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[1642] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[1643] Step(4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[1644] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[1645] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[1646] Hereinafter, each of the steps will be described in
detail.
[1647] Step (1): Step of Producing Fluorine-Containing Polymer
[1648] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[1649] Step (2): Step of Producing Reinforcing Materials
[1650] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based, on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[1651] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and, comprising polyvinyl alcohol and
the like are also preferred.
[1652] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[1653] Step (3): Step of Film Formation
[1654] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[1655] Examples of the film forming method include the
following:
[1656] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[1657] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[1658] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[1659] Step (4): Step of Obtaining Membrane Body
[1660] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[1661] Preferable examples of the method for forming a membrane
body include (i) a method in which a fluorine-containing polymer
having a carboxylic acid group precursor (e.g., carboxylate
functional group) (hereinafter, a layer comprising the same is
referred to as the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[1662] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[1663] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property of sufficiently retaining
the mechanical strength of the ion exchange membrane.
[1664] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[1665] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[1666] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[1667] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[1668] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[1669] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that is, projections, on the surface
side composed of the sulfonic acid layer. As a method for forming
such projections, which is not particularly limited, a known method
also can be employed including forming projections on a resin
surface. A specific example of the method is a method of embossing
the surface of the membrane body. For example, the above
projections can be formed by using release paper embossed in
advance when the composite film mentioned above, reinforcing
material, and the like are integrated. In the case where
projections are formed by embossing, the height and arrangement
density of the projections can be controlled by controlling the
emboss shape to be transferred (shape of the release paper).
[1670] (5) Hydrolysis Step
[1671] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[1672] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[1673] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[1674] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[1675] The mixed solution preferably contains NON of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[1676] The temperature for hydrolysis is preferably, 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[1677] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[1678] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 99(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[1679] FIGS. 99(a) and (b) show reinforcement yarns 52 sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[1680] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[1681] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[1682] FIG. 99(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
(6) Application Step
[1683] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[1684] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counterion of the ion exchange
group by H+ (e.g., a fluorine-containing polymer having a carboxyl
group or sulfo group). Thereby, the polymer is more likely to
dissolve in water or ethanol mentioned below, which is
preferable.
[1685] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[1686] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[1687] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are Preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[1688] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[1689] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[1690] The porosity of the microporous membrane of the present
embodiment is not particular limited, but can be 20 to 90, for
example and preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity (1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[1691] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[1692] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[1693] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[1694] In the present embodiment, the membrane preferably comprises
a first ion exchange resin layer and a second ion exchange resin
layer having an EW (ion exchange capacity) different from that of
the first ion exchange resin layer. Additionally, the membrane
preferably comprises a first ion exchange resin layer and a second
ion exchange resin layer having a functional group different from
that of the first ion exchange resin layer. The ion exchange
capacity can be adjusted by the functional group to be introduced,
and functional groups that may be introduced are as mentioned
above.
(Water Electrolysis)
[1695] The electrolyzer in the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
[Method for Renewing Electrode]
[1696] The method for producing an electrolyzer according to the
present embodiment can be performed also as a method for renewing
an electrode (anode and/or cathode). That is, the method for
renewing an electrode according to the present embodiment is a
method for renewing an existing electrode by using an electrode for
electrolysis, wherein the electrode for electrolysis being in a
wound body form is used.
[1697] Specific examples of a step of using a wound body include,
but not particularly limited to thereto, a method in which the
electrode for electrolysis being in a wound body form, after its
wound state is released, is arranged on the surface of the existing
electrode. By means of the method, the electrode for electrolysis
can be arranged on the surface of the existing anode or cathode,
and the characteristics of the anode and/or cathode can be
renewed.
[1698] As described above, in the present embodiment, the step of
using a wound body preferably has a step (B') of releasing the
wound state of the wound body, and after the step (B'), more
preferably has a step (C') of arranging an electrode for
electrolysis on the surface of the existing electrode.
[1699] Also in the method for renewing an electrode according to
the present embodiment, the step of using a wound body preferably
has a step (A') of retaining the electrode for electrolysis in a
wound state to thereby obtain a wound body. In the step (A'), the
electrode for electrolysis per se may be wound to form a wound
body, or the electrode for electrolysis is wound around a core to
form a wound body. As the core that may be used here, which is not
particularly limited, a member having a substantially cylindrical
form and having a size corresponding to the electrode for
electrolysis can be used, for example.
[Method for Producing Wound Body]
[1700] In the method for producing an electrolyzer according to the
present embodiment and the method for renewing an electrode
according to the present embodiment, the step (A) or (A'), which
may be performed, can be performed also as a method for producing a
wound body. That is, the method for producing a wound body
according to the present embodiment is a method for producing a
wound body to be used for renewing an existing electrolyzer
comprising an anode, a cathode that is opposed to the anode, and a
membrane that is arranged between the anode and the cathode, the
method comprising a step of winding an electrode for electrolysis
or a laminate of the electrode for electrolysis and a new membrane
to thereby obtain the wound body. In the step of obtaining a wound
body, the electrode for electrolysis per se may be wound to form a
wound body, or the electrode for electrolysis may be wound around a
core to form a wound body. As the core that may be used here, which
is not particularly limited, a member having a substantially
cylindrical form and having a size corresponding to the electrode
for electrolysis can be used, for example.
Sixth Embodiment
[1701] Here, a sixth embodiment of the present invention will be
described in detail with reference to FIGS. 103 to 111.
[Method for Producing Electrolyzer]
[1702] The method for producing an electrolyzer according to the
sixth embodiment (hereinafter, in the section of <Sixth
embodiment>, simply referred to as "the present embodiment") is
a method for producing a new electrolyzer by arranging a laminate
in an existing electrolyzer comprising an anode, a cathode that is
opposed to the anode, and a membrane that is arranged between the
anode and the cathode, the method comprising a step (A) of
integrating an electrode for electrolysis with a new membrane at a
temperature at which the membrane does not melt to thereby obtain
the laminate, and a step (Ti) of replacing the membrane in the
existing electrolyzer by the laminate after the step (A).
[1703] As described above, according to the method for producing an
electrolyzer according to the present embodiment, it is possible to
integrate and use the electrode for electrolysis and the membrane,
not in accordance with an impractical method such as thermal
compression. Thus, it is possible to improve the work efficiency
during electrode renewing in an electrolyzer.
[1704] In the present embodiment, the existing electrolyzer
comprises an anode, a cathode that is opposed to the anode, and a
membrane that is arranged between the anode and the cathode as
constituent members, in other words, comprises an electrolytic
cell. The existing electrolyzer is not particularly limited as long
as comprising the constituent members described above, and various
known configurations may be employed.
[1705] In the present embodiment, a new electrolyzer further
comprises an electrode for electrolysis or a laminate, in addition
to a member that has already served as the anode or cathode in the
existing electrolyzer. That is, the "electrode for electrolysis"
arranged on production of a new electrolyzer serves as the anode or
cathode, and is separate from the cathode and anode in the existing
electrolyzer. In the present embodiment, even in the case where the
electrolytic performance of the anode and/or cathode has
deteriorated in association with operation of the existing
electrolyzer, arrangement of an electrode for electrolysis
separating therefrom enables the characteristics of the anode
and/or cathode to be renewed. Further, a new ion exchange membrane
constituting the laminate is arranged in combination, and thus, the
characteristics of the ion exchange membrane having characteristics
deteriorated in association with operation can be renewed
simultaneously. "Renewing the characteristics" referred to herein
means to have characteristics comparable to the characteristics
possessed by the existing electrolyzer before being operated or to
have characteristics higher than the initial character.
[1706] In the present embodiment, the existing electrolyzer is
assumed to be an "electrolyzer that has been already operated", and
the new electrolyzer is assumed to be an "electrolyzer that has not
been yet operated". That is, once an electrolyzer produced as a new
electrolyzer is operated, the electrolyzer becomes "the existing
electrolyzer in the present embodiment". Arrangement of an
electrode for electrolysis or a laminate in this existing
electrolyzer provides "a new electrolyzer of the present
embodiment".
[1707] Hereinafter, a case of performing common salt electrolysis
by using an ion exchange membrane as the membrane is taken as an
example, and one embodiment of the electrolyzer will be described
in detail. In the section of <Sixth embodiment>, unless
otherwise specified, "the electrolyze the present embodiment"
incorporates both "the existing electrolyzer in the present
embodiment" and "the new electrolyzer in the present
embodiment".
[Electrolytic Cell]
[1708] First, the electrolytic cell, which can be used as a
constituent unit of the electrolyzer in the present embodiment,
will be described. FIG. 103 illustrates a cross-sectional view of
an electrolytic cell 1.
[1709] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 107, and the cathode 21 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer ma be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[1710] FIG. 104 illustrates a cross-section view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
105 shows an electrolyzer 4. FIG. 106 shows a step of assembling
the electrolyzer
[1711] As shown in FIG. 104, an electrolytic cell 1, a cation
exchange membrane 2, and an electrolytic cell 1 are arranged in
series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 among
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 105, the
electrolyzer 4 is composed of a plurality of electrolytic cells 1
connected in series via the ion exchange membrane That is, the
electrolyzer 4 is a bipolar electrolyzer comprising the plurality
of electrolytic cells 1 arranged in series and ion exchange
membranes 2 each arranged between adjacent electrolytic cells 1. As
shown in FIG. 106, the electrolyzer 4 is assembled by arranging the
plurality of electrolytic cells 1 in series via the ion exchange
membrane 2 and coupling the cells by means of a press device 5.
[1712] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[1713] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[1714] The anode chamber 10 has the anode 11 or anode feed
conductor 11. The feed conductor herein referred to mean a degraded
electrode (i.e., the existing electrode), an electrode having no
catalyst coating, and the like. When the electrode for electrolysis
in the present embodiment is inserted to the anode side, 11 serves
as an anode feed conductor. When the electrode for electrolysis in
the present embodiment is not inserted to the anode side, 11 serves
as an anode. The anode chamber 10 preferably has an anode-side
electrolyte solution supply unit that supplies an electrolyte
solution to the anode chamber 10, a baffle plate that is arranged
above the anode-side electrolyte solution supply unit so as to be
substantially parallel or oblique to a partition wall 30, and an
anode-side gas liquid separation unit that is arranged above the
baffle plate to separate gas from the electrolyte solution
including the gas mixed.
(Anode)
[1715] When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, an anode 11 is
provided in the frame of the anode chamber 10 the anode frame). As
the anode 11, a metal electrode such as so-called DSA(R) can be
used. DSA is an electrode including a titanium substrate of which
surface is covered with an oxide comprising ruthenium, iridium, and
titanium as components.
[1716] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[1717] When the electrode for electrolysis in the present
embodiment is inserted to he anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having thinner catalyst coating can be also
used. Further, a used anode can be also used.
[1718] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[1719] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Liquid Separation Unit)
[1720] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 103, and below means the lower
direction in the electrolytic cell 1 in FIG. 103.
[1721] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 in the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle Plate)
[1722] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned the baffle
plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[1723] Although not shown in FIG. 103, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[1724] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[1725] In the cathode chamber 20, when the electrode for
electrolysis in the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis in the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 will be not described.
(Cathode)
[1726] When the electrode for electrolysis in the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20 (i.e., cathode
frame). The cathode 21 preferably has a nickel substrate and a
catalyst layer that covers the nickel substrate. Examples of the
components of the catalyst layer on the nickel substrate include
metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, ir, Pt,
Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb, and Lu, and oxides and hydroxides of the metals. Examples of
the method for forming the catalyst layer include plating, alloy
plating, dispersion/composite plating, CVD, PVC, pyrolysis, and
spraying. These methods may be used in combination. The catalyst
layer may have a plurality of layers and a plurality of elements,
as required. The cathode 21 may be subjected to a reduction
treatment, as required. As the substrate of the cathode 21, nickel,
nickel alloys, and nickel-plated iron or stainless may be used.
[1727] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[1728] When the electrode for electrolysis in the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals such as Ru, C, Si,
P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Nickel, nickel
alloys, and nickel-plated iron or stainless, having no catalyst
coating may be used. As the substrate of the cathode feed conductor
21, nickel, nickel alloys, and nickel-plated iron or stainless may
be used.
[1729] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[1730] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as a material for the
reverse current absorbing layer. Examples thereof include nickel
and iron.
(Collector)
[1731] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[1732] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[1733] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electro electrolytic cells 1
connected in series. Lowering of the voltage enables the power
consumption to be reduced. With the metal elastic body 22 placed,
the pressing pressure caused by the metal elastic body 22 enables
the electrode for electrolysis to be stably maintained in place
when the laminate including the electrode for electrolysis in the
present embodiment is paced in the electrolytic cell.
[1734] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[1735] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[1736] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[1737] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane 2 (See FIG. 104). These
gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[1738] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced as and be
usable for long period. Thus, in respect of chemical resistance and
hardness, vulcanized products and peroxide-crosslinked products of
ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For a picture frame-like gasket is attached with an
adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 104),
each electrolytic cell 1 onto which the gasket is attached should
be tightened via ion exchange membrane 2. This tightening can
prevent the electrolyte solution, alkali metal hydroxide, chlorine
gas, hydrogen gas, and the like generated from electrolysis from
leaking out of the electrolytic cells 1.
[Laminate]
[1739] The electrode for electrolysis in the present embodiment is
used as a laminate of a membrane such as an ion exchange membrane
or a macroporous membrane. That is, the laminate in the present
embodiment comprises the electrode for electrolysis and a new
membrane. The new membrane is not particularly limited as long as
being separate from the membrane in the existing electrolyzer, and
various known "membranes" can be used. The material, form, physical
properties, and the like of the new membrane may be similar to
those of the membrane in the existing electrolyzer. Specific
examples of the electrode for electrolysis and the membrane will be
detailed below.
(Step (A))
[1740] In the step of the present embodiment, the electrode for
electrolysis and a new membrane are integrated at a temperature at
which the membrane does not melt to thereby obtain a laminate.
[1741] The "temperature at which the membrane does not melt" can be
identified as the softening point of the new membrane. The
temperature may vary depending on the material constituting the
membrane but is preferably 0 to 100.degree. C., more preferably 5
to 80.degree. C., further preferably 10 to 50.degree. C.
[1742] The integration described above is preferably performed
under normal pressure.
[1743] As a specific method for the above integration, which are
not particularly limited, all kinds of methods, except for typical
methods for melting the membrane such as thermal compression can be
used. One preferable example is a method in which a liquid is
interposed between an electrode for electrolysis mentioned below
and the membrane and the surface tension of the liquid is used to
integrate the electrode and the "membrane.
[Step (B)]
[1744] In the step (B) in the present embodiment, the membrane in
the existing electrolyzer is replaced by a laminate after the step
(A). The replacing method is not particularly limited, and examples
thereof include a method in which, first in the existing
electrolyzer, a fixed state of the adjacent electrolytic cell and
ion exchange membrane by means of a press device is released to
provide a gap between the electrolytic cell and the ion exchange
membrane, then, the existing ion exchange membrane to be renewed is
removed, then, a laminate is inserted into the gap, and the members
are coupled again by means of the press device. By means of the
method, a laminate can be arranged on the surface of the anode or
the cathode of the existing electrolyzer, and the characteristics
of the ion exchange membrane and the anode and/or cathode can be
renewed.
[Electrode for Electrolysis]
[1745] In the present embodiment, the electrode for electrolysis is
not particularly limited as long as the electrode can be integrated
with a new membrane as mentioned above, that is, is integratable.
The electrode for electrolysis may be an electrode that serves as
the cathode in the electrolyzer or may be an electrode that serves
as an anode. As the material, form, and the like of the electrode
for electrolysis, those suitable may be appropriately selected, in
consideration of the steps (A) and (B) in the present embodiment,
the configuration of the electrolyzer, and the like. Hereinbelow,
preferable aspects of the electrode for electrolysis in the present
embodiment will be described, but these are merely exemplary
aspects preferable for integration with a new membrane. Electrodes
for electrolysis other than the aspects mentioned below can be
appropriately employed.
[1746] The electrode for electrolysis in the present embodiment has
a force applied per unit massunit area of preferably 1.6
N/(mgcm.sup.2) or less, more preferably less than 1.6
N/(mgcm.sup.2), further preferably less than 1.5 N/(mgcm.sup.2),
even further preferably 1.2 N/mgcm.sup.2 or less, still more
preferably 1.20 N/mgcm.sup.2 or less from the viewpoint of enabling
a good handling property to be provided and having a good adhesive
force to a membrane such as an ion exchange membrane and a
microporous membrane, a feed conductor (a degraded electrode and an
electrode having no catalyst coating), and the like. The force
applied is even still more preferably 1.1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[1747] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0.2 N/(mgcm.sup.2) or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1748] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[1749] The mass per unit is preferably 48 mg/cm.sup.2 or less, more
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and of economy, and furthermore preferably 15 mg/cm.sup.2 or less
from the comprehensive viewpoint including handling property,
adhesion, and economy. The lower limit value is not particularly
limited but is of the order of 1 mg/cm.sup.2, for example.
[1750] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[1751] The force applied can be measured by methods (i) or (ii)
described below, which are as detailed in Examples. As for the
force applied, the value obtained by the measurement of the method
(i) (also referred to as "the force applied (1)") and the value
obtained by the measurement of the method (ii) (also referred to as
"the force applied (2)") may the same or different, and either of
the values preferably less than 1.5 N/mgcm.sup.2.
[Method (i)]
[1752] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. The arithmetic average surface roughness
(Ra) of the nickel plate after the blast treatment is 0.5 to 0.8
.mu.m. The specific method for calculating the arithmetic average
surface roughness (Ra) is as described in Examples.
[1753] Under conditions of a temperature of 23.+-.2.degree. C. and
a relative humidity of 30.+-.5%, only the sample of electrode in
this sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[1754] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[1755] The force applied per unit massunit area (1) obtained by the
method (i) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. The force is preferably more than 0.005 N/(mgcm.sup.2),
more preferably 0.08 N/(mgcm.sup.2) or more, further preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of further improving the
electrolytic performance, and furthermore, is further more
preferably 0.14 N/(mgcm.sup.2), still more preferably 0.2
N/(mgcm.sup.2) or more from the viewpoint of further facilitating
handling in a large size (e.g., a size of 1.5 m.times.2.5 m.).
[Method (ii)]
[1756] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[1757] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[1758] The force applied per unit massunit area (2) obtained by the
method (ii) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. Further, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.02 N/(mgcm.sup.2) or more,
further preferably 0.1 N/(mgcm.sup.2) or more from the viewpoint of
further improving the electrolytic performance, and is further more
preferably 0.14 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[1759] The electrode for electrolysis in the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 120 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having no catalyst coating, being capable of being
suitably rolled in a roll and satisfactorily folded, and
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[1760] In the present embodiment, in order to integrate a new
membrane and the electrode for electrolysis, a liquid is preferably
interposed therebetween. As the liquid, any liquid, such as water
and organic solvents, can be used as long as the liquid generates a
surface tension. The larger the surface tension of the liquid, the
larger the force applied between the new membrane and the electrode
for electrolysis. Thus, a liquid having a larger surface tension is
preferred. Examples of the liquid include the following (the
numerical value in the parentheses is the surface tension of the
liquid at 20.degree. C.):
[1761] hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00
mN/m), ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and
water (72.76 mN/m).
[1762] A liquid having a large surface tension allows the new
membrane and the electrode for electrolysis to be integrated (to be
a laminate), and renewing of the electrode tends to be easier. The
liquid between the new membrane and the electrode for electrolysis
may be present in an amount such that the both adhere to each other
by the surface tension. As a result, after the laminate is placed
in an electrolytic cell, the liquid, if mixed into the electrolyte
solution, does not affect electrolysis itself due to the small
amount of the liquid.
[1763] From a practical viewpoint, a liquid having a surface
tension of 24 mN/m to 80 mN/m, such as ethanol, ethylene glycol,
and water, is preferably used as the liquid. Particularly preferred
is water or an alkaline aqueous solution prepared h dissolving
caustic soda, potassium hydroxide, lithium hydroxide, sodium
hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate,
potassium carbonate, or the like in water. Alternatively, the
surface tension can be adjusted by allowing these liquids to
contain a surfactant. When a surfactant is contained, the adhesion
between the new membrane and the electrode for electrolysis varies
to enable the handling property to be adjusted. The surfactant is
not particularly limited, and both ionic surfactants and nonionic
surfactants may be used.
[1764] The proportion measured by the following method (2) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a macroporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint of further facilitating handling in
a large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2)]
[1765] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1766] The proportion measured by the following method (3) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from the viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[1767] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[1768] The electrode for electrolysis in the present embodiment
preferably has, but is not particularly limited to, a porous
structure and an opening ratio or void ratio of 5 to 90% or less,
from the viewpoint of enabling a good handling property to be
provided, having a good adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode
(feed conductor), and an electrode (feed conductor) having no
catalyst coating, and preventing accumulation of gas to be
generated during electrolysis. The opening ratio is more preferably
10 to 80% or less, further preferably 20 to 75%.
[1769] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V is calculated from the values of the gauge thickness,
width, and length of electrode, and further, a weight W is measured
to thereby enable an opening ratio A to be calculated by the
following formula.
A=(1-(W/(V.times..rho.)).times.100
[1770] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio can be
appropriately adjusted by changing the area of metal to be
perforated per unit area in the case of perforated metal, changing
the values of the SW (short diameter), LW (long diameter), and feed
in the case of expanded metal, changing the line diameter of metal
fiber and mesh number in the case of mesh, changing the pattern of
a photoresist to be used in the case of electroforming, changing
the metal fiber diameter and fiber density in the case of nonwoven
fabric, changing the mold for forming voids in the case of foamed
metal, or the like.
[1771] Hereinbelow, a more specific embodiment of the electrode for
electrolysis in the present embodiment will be described.
[1772] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[1773] As shown in FIG. 108, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[1774] Also as shown FIG. 108, the surfaces of the first layers 20
may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[1775] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[1776] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[1777] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[1778] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[1779] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[1780] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[1781] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[1782] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[1783] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[1784] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 8
.mu.m.
[1785] Next, a case where the electrode for electrolysis in the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[1786] In FIG. 108, a first layer 20 as a catalyst layer contains
at least one of ruthenium oxides, iridium oxides, and titanium
oxides. Examples of the ruthenium oxide include RuO.sub.2. Examples
of the iridium oxide include IrO.sub.2. Examples of the titanium
oxide include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[1787] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1788] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol or the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[1789] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[1790] In addition to the compositions described above, oxides of
various compositions can he used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[1791] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 .mu.m, more preferably 0.1 to 8 .mu.m.
(Second Layer)
[1792] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[1793] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[1794] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[1795] Next, a case where the electrode for electrolysis in the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[1796] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[1797] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[1798] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[1799] As the platinum group metal, platinum is preferably
contained.
[1800] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[1801] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[1802] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[1803] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[1804] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[1805] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[1806] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[1807] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[1808] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[1809] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[1810] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained
[1811] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[1812] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The curability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[1813] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[1814] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[1815] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[1816] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness is more preferably 0.1 to 10 .mu.m. The thickness is
further preferably 0.2 to 8 .mu.m.
[1817] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness is preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis is
measured in the same manner as the thickness of the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
[1818] In the present embodiment, the electrode for electrolysis
preferably contains at least one catalytic component selected from
the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb,
Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
and Dy from the viewpoint of achieving sufficient electrolytic
performance.
[1819] In the present embodiment, from the viewpoint that the
electrode for electrolysis, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a macroporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness or 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
(Method for Producing Electrode for Electrolysis)
[1820] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[1821] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking or a coating film under an oxygen
atmosphere (pyrolysis), or ion plating, plating, or thermal
spraying. The production method of the present embodiment as
mentioned can achieve a high productivity of the electrode for
electrolysis 100. Specifically, a catalyst layer is formed on the
substrate for electrode for electrolysis by an application step of
applying a coating liquid containing a catalyst, a drying step of
drying the coating liquid, and a pyrolysis step of performing
pyrolysis. Pyrolysis herein means that a metal salt which is to be
a precursor is decomposed by heating into a metal or metal oxide
and a gaseous substance. The decomposition product depends on the
metal species to be used, type of the salt, and the atmosphere
under which pyrolysis is performed, and many metals tend to form
oxides in an oxidizing atmosphere. In an industrial process of
producing an electrode, pyrolysis is usually performed in air, and
a metal oxide or a metal hydroxide is formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[1822] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[1823] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[1824] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1825] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable 5 to 20 minutes more preferable.
[1826] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[1827] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[1828] The first layer 20 obtained by applying a solution in which
metal salts of various combination are dissolved (first coating
liquid) onto the substrate for electrode for electrolysis and then
pyrolyzing (baking) the coating liquid in the presence of oxygen.
The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[1829] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[1830] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[1831] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[1832] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and the
further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[1833] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[1834] The first layer 20 can be formed also by ion plating. An
example includes a method in which the substrate is fixed in a
chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[1835] The first layer 20 can be formed also by a plating
method.
[1836] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal Spraying)
[1837] The first layer 20 can be formed also by thermal
spraying.
[1838] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[1839] Hereinafter, an ion exchange membrane according to one
aspect of the membrane will be described in detail.
[Ion Exchange Membrane]
[1840] The ion exchange membrane is not particularly limited as
long as the membrane can be laminated with the electrode for
electrolysis, and various ion exchange membranes may be employed.
In the present embodiment, an ion exchange membrane that has a
membrane body containing a hydrocarbon polymer or
fluorine-containing polymer having an ion exchange group and a
coating layer provided on at least one surface of the membrane body
is preferably used. It is preferable that the coating layer contain
inorganic material particles and a binder and the specific surface
area of the coating layer be 0.1 to 10 m.sup.2/g. The ion exchange
membrane having such a structure has a small influence of gas
generated during electrolysis on electrolytic performance and tends
to exert stable electrolytic performance.
[1841] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO.sub.3--, hereinbelow also
referred to as a "sulfonic acid group") or a carboxylic acid layer
having an ion exchange group derived from a carboxyl group (a group
represented by --CO.sub.2--, hereinbelow also referred to as a
"carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[1842] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[1843] FIG. 109 illustrates a cross-sectional schematic view
showing one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-containing polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[1844] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by hereinbelow also
referred to as a "sulfonic acid group") and a carboxylic acid layer
2 having an ion exchange group derived from a carboxyl group (a
group represented by --CO.sub.2--, hereinbelow also referred to as
a "carboxylic acid group"), and the reinforcement core materials 4
enhance the strength and dimension stability. The ion exchange
membrane 1, as comprising the sulfonic acid layer 3 and the
carboxylic acid layer 2, is suitably used as an anion exchange
membrane.
[1845] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 109.
(Membrane Body)
[1846] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[1847] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[1848] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[1849] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[1850] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound is preferably a perfluoro monomer, and
a perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[1851] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.2--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[1852] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[1853] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time of hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[1854] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[1855]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[1856]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[1857]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[1858]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[1859] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[1860] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[1861] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[1862] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[1863]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[1864]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[1865] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[1866]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[1867]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[1868] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[1869] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[1870] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[1871] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0.5 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[1872] In the membrane body 10 of the ion exchange membrane a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[1873] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer 2 is
located on the cathode side of the electrolyzer.
[1874] The sulfonic acid layer 3 preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[1875] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[1876] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[1877] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2).sub.2COOCH.sub.3 as
the monomer of the second group.
(Coating Layer)
[1878] The ion exchange membrane preferably has a coating layer on
at least one surface of the membrane body. As shown in FIG. 109, in
the ion exchange membrane 1, coating layers 11a and 11b are formed
on both the surfaces of the membrane body 10.
[1879] The coating layers contain inorganic material particles and
a binder.
[1880] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[1881] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably 0.90 to 1.2 .mu.m.
[1882] Here, the average particle size can be measured by a
particle size analyzer ("SALD2200", SHIMADZU CORPORATION).
[1883] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[1884] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides of Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durabilty, zirconium
oxide particle is more preferable.
[1885] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[1886] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurites such as iron attached to the surface
of the inorganic material particles.
[1887] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[1888] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder the coating layer.
[1889] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[1890] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[1891] As the method for forming the coating layer, which is not
particularly limited, a known method can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing a binder.
(Reinforcement Core Materials)
[1892] The ion exchange membrane preferably has reinforcement core
materials arranged inside the membrane body.
[1893] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contraction of the ion
exchange membrane can be controlled in the desired range. Such an
ion exchange membrane does not expand or contract more than
necessary during electrolysis and the like and can maintain
excellent dimensional stability for a long term.
[1894] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[1895] The material of the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, etc., and a fiber
comprising a fluorine-containing polymer is preferable because
long-term heat resistance and chemical resistance are required.
[1896] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[1897] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[1898] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[1899] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[1900] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[1901] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[1902] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[1903] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[1904] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area of a surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[1905] FIG. 110 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 110, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[1906] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperture ratio=(B)/(A)=((A)-(C))/(A) (I)
[1907] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[1908] Examples of the shape of the reinforcement yarns include
round yarns and tape yarns.
(Continuous Holes)
[1909] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[1910] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below. The shape,
diameter, or the like of the continuous holes can be controlled by
selecting the shape or diameter of the sacrifice core materials
(sacrifice yarns).
[1911] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape of sacrifice core materials to be
used for formation of the continuous holes in accordance with the
production method described below.
[1912] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[1913] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[1914] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[1915] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[1916] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[1917] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[1918] Step(4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[1919] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[1920] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[1921] Hereinafter, each of the steps will be described in
detail.
[1922] Step (1): Step of Producing Fluorine-Containing Polymer
[1923] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[1924] Step (2); Step of Producing Reinforcing Materials
[1925] The reinforcing material is a woven fabric obtained by
weaving reinforcement yarns or the like. The reinforcing material
is embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based, on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[1926] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamides and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and, comprising polyvinyl alcohol and
the like are also preferred.
[1927] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[1928] Step (3): Step of Film Formation
[1929] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[1930] Examples of the film forming method include the
following:
[1931] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[1932] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[1933] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[1934] Step (4): Step of Obtaining Membrane Body
[1935] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[1936] Preferable examples of the method for forming a membrane
body include (i) a method in which a fluorine-containing polymer
having a carboxylic acid group precursor (e.g., carboxylate
functional group) (hereinafter, a layer comprising the same is
referred to as the first layer) located on the cathode side and a
fluorine-containing polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[1937] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[1938] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property capable of sufficiently
retaining the mechanical strength of the ion exchange membrane.
[1939] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[1940] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[1941] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[1942] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[1943] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[1944] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that is, projections, on the surface
side composed of the sulfonic acid layer. As a method for forming
such projections, which is not particularly limited, a known method
also can be employed including forming projections on a resin
surface. A specific example of the method is a method of embossing
the surface of the membrane body. For example, the above
projections can be formed by using release paper embossed in
advance when the composite film mentioned above, reinforcing
material, and the like are integrated. In the case where
projections are formed by embossing, the height and arrangement
density of the projections can be controlled by controlling the
emboss shape to be transferred (shape of the release paper).
(5) Hydrolysis Step
[1945] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[1946] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[1947] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[1948] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[1949] The mixed solution preferably contains KOH of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[1950] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[1951] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[1952] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 111(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[1953] FIGS. 111(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[1954] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[1955] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[1956] FIG. 111(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
(6) Application Step
[1957] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[1958] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counterion of the ion exchange
group by H+ (e.g., a fluorine-containing polymer having a carboxyl
group or sulfo group). Thereby, the polymer is more likely to
dissolve in water or ethanol mentioned below, which is
preferable.
[1959] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[1960] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[1961] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[1962] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[1963] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[1964] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example and preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[1965] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[1966] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactured by
Mitutoyo Corporation) or the like, for example.
[1967] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa (also
referred to as a Zirfon membrane in the present embodiment) and
those described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[1968] In the present embodiment, the membrane preferably comprises
a first ion exchange resin layer and a second ion exchange resin
layer having an EW (ion exchange capacity) different from that of
the first ion exchange resin layer. Additionally, the membrane
preferably comprises a first ion exchange resin layer and a second
ion exchange resin layer having a functional group different from
that of the first ion exchange resin layer. The ion exchange
capacity can be adjusted by the functional group to be introduced,
and functional groups that may be introduced are as mentioned
above.
(Water Electrolysis)
[1969] The electrolyzer in the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
Seventh Embodiment
[1970] Here, a seventh embodiment of the present invention will be
described in detail with reference to FIGS. 112 to 122.
[Method for Producing Electrolyzer]
[1971] The method for producing an electrolyzer according to the
first aspect (hereinafter, simply referred to as the "first
aspect") of the seventh embodiment (hereinafter, in the section of
<Seventh embodiment>, simply referred to as "the present
embodiment") is a method for producing a new electrolyzer arranging
a laminate comprising an electrode for electrolysis and a new
membrane in an existing electrolyzer comprising an anode, a cathode
that opposed to the anode, a membrane that is fixed between the
anode and the cathode, and an electrolyzer frame that supports the
anode, the cathode, and the membrane, the method comprising a step
(A) of releasing a fixing of the membrane in the electrolyzer
frame, and a step (B) of replacing the membrane by the laminate
after the step (A).
[1972] As described above, according to the method for producing an
electrolyzer according to the first aspect, it is possible to renew
the electrode without removing each component to the outside of the
electrolyzer frame, and it is possible to improve the work
efficiency during electrode renewing in an electrolyzer.
[1973] A method for producing an electrolyzer according to a second
aspect (hereinbelow, also simply referred to as the "second
aspect") of the present embodiment is a method for producing a new
electrolyzer by arranging an electrode for electrolysis in an
existing electrolyzer comprising an anode, a cathode that is
opposed to the anode, a membrane that is fixed between the anode
and the cathode, and an electrolyzer frame that supports the anode,
the cathode, and the membrane, the method comprising a step (A) of
releasing a fixing of the membrane in the electrolyzer frame, and a
step (B') of arranging the electrode for electrolysis between the
membrane and the anode or the cathode after the step (A).
[1974] As described above, also in accordance with the method for
producing an electrolyzer according to the second aspect, it is
possible to renew the electrode without removing each component to
the outside of the electrolyzer frame, and it is possible to
improve the work efficiency during electrode renewing in an
electrolyzer.
[1975] Hereinbelow, when referred to as the "method for producing
an electrolyzer according to the present embodiment", the method
for producing an electrolyzer according to the first aspect and the
method for producing an electrolyzer according to the second aspect
are incorporated.
[1976] In the method for producing an electrolyzer according to the
present embodiment, the existing electrolyzer comprises an anode, a
cathode that is opposed to the anode, a membrane that is arranged
between the anode and the cathode, and an electrolyzer frame that
supports the anode, the cathode, and the membrane as constituent
members. In other words, the existing electrolyzer comprises a
membrane, an electrolytic cell, and an electrolyzer frame that
supports the membrane and the electrolytic cell. The existing
electrolyzer is not particularly limited as long as comprising the
constituent members described above, and various known
configurations may be employed.
[1977] In the method for producing an electrolyzer according to the
present embodiment, a new electrolyzer further comprises an
electrode for electrolysis or a laminate, in addition to a member
that has already served as the anode or cathode in the existing
electrolyzer. That is, in the first aspect and the second aspect,
the "electrode for electrolysis" arranged on production of a new
electrolyzer serves as the anode or cathode and is separate from
the cathode and anode in the existing electrolyzer. In the method
for producing an electrolyzer according to the present embodiment,
even in the case where the electrolytic performance of the anode
and/or cathode has deteriorated in association with operation of
the existing electrolyzer, arrangement of an electrode for
electrolysis separate therefrom enables the characteristics of the
anode and/or cathode to be renewed. In the first aspect, in which a
laminate is used, a new ion exchange membrane is arranged in
combination, and thus, the characteristics of the ion exchange
membrane having characteristics deteriorated in association with
operation can be renewed simultaneously. "Renewing the
characteristics" referred to herein means to have characteristics
comparable to the initial characteristics possessed by the existing
electrolyzer before being operated or to have characteristics
higher than the initial characteristics.
[1978] In the method for producing an electrolyzer according to the
present embodiment, the existing electrolyzer is assumed to be an
"electrolyzer that has been already operated", and the new
electrolyzer is assumed to be an "electrolyzer that has not been
yet operated". That is, once an electrolyzer produced as a new
electrolyzer is operated, the electrolyzer becomes "the existing
electrolyzer in the present embodiment". Arrangement of an
electrode for electrolysis or a laminate in this existing
electrolyzer provides "a new electrolyzer of the present
embodiment".
[1979] Hereinafter, a case of performing common salt electrolysis
by using an ion exchange membrane as the membrane is taken as an
example, and one embodiment of the electrolyzer will be described
in detail. In the section of <Seventh embodiment>, unless
otherwise specified, "the electrolyzer in the present embodiment"
incorporates both "the existing electrolyzer in the present
embodiment" and "the new electrolyzer in the present
embodiment".
[Electrolytic Cell]
[1980] First, the electrolytic cell, which can be used as a
constituent unit of the electrolyzer in the present embodiment,
will be described. FIG. 112 illustrates a cross-sectional view of
an electrolytic cell 1.
[1981] The electrolytic cell 1 comprises an anode chamber 10, a
cathode chamber 20, a partition wall 30 placed between the anode
chamber 10 and the cathode chamber 20, an anode 11 placed in the
anode chamber 10, and a cathode 21 placed in the cathode chamber
20. As required, the electrolytic cell has a substrate 18a and a
reverse current absorbing layer 18b formed on the substrate 18a and
may comprise a reverse current absorber 18 placed in the cathode
chamber. The anode 11 and the cathode 21 belonging to the
electrolytic cell 1 are electrically connected to each other. In
other words, the electrolytic cell 1 comprises the following
cathode structure. The cathode structure 40 comprises the cathode
chamber 20, the cathode 21 placed in the cathode chamber 20, and
the reverse current absorber 18 placed in the cathode chamber 20,
the reverse current absorber 18 has the substrate 18a and the
reverse current absorbing layer 18b formed on the substrate 18a, as
shown in FIG. 116, and the cathode 21 and the reverse current
absorbing layer 18b are electrically connected. The cathode chamber
20 further has a collector 23, a support 24 supporting the
collector, and a metal elastic body 22. The metal elastic body 22
is placed between the collector 23 and the cathode 21. The support
24 is placed between the collector 23 and the partition wall 30.
The collector 23 is electrically connected to the cathode 21 via
the metal elastic body 22. The partition wall 30 is electrically
connected to the collector 23 via the support 24. Accordingly, the
partition wall 30, the support 24, the collector 23, the metal
elastic body 22, and the cathode 21 are electrically connected. The
cathode 21 and the reverse current absorbing layer 18b are
electrically connected. The cathode 21 and the reverse current
absorbing layer ma be directly connected or may be indirectly
connected via the collector, the support, the metal elastic body,
the partition wall, or the like. The entire surface of the cathode
21 is preferably covered with a catalyst layer for reduction
reaction. The form of electrical connection may be a form in which
the partition wall 30 and the support the support 24 and the
collector 23, and the collector 23 and the metal elastic body 22
are each directly attached and the cathode 21 is laminated on the
metal elastic body 22. Examples of a method for directly attaching
these constituent members to one another include welding and the
like. Alternatively, the reverse current absorber 18, the cathode
21, and the collector 23 may be collectively referred to as a
cathode structure 40.
[1982] FIG. 113 illustrates a cross-section view of two
electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG.
114 shows an electrolyzer 4 as an existing electrolyzer. FIG. 115
shows a step of assembling the electrolyzer (different from steps
(A) to (B) and steps (A') to (B')).
[1983] As shown in FIG. 113, an electrolytic cell 1, a cation
exchange membrane 2, and an electrolytic cell 1 are arranged in
series in the order mentioned. An ion exchange membrane 2 is
arranged between the anode chamber of one electrolytic cell 1 of
the two electrolytic cells that are adjacent in the electrolyzer
and the cathode chamber of the other electrolytic cell 1. That is,
the anode chamber 10 of the electrolytic cell 1 and the cathode
chamber 20 of the electrolytic cell 1 adjacent thereto is separated
by the cation exchange membrane 2. As shown in FIG. 114, the
electrolyzer 4 is composed such that the plurality of electrolytic
cells 1 connected in series via the ion exchange membranes 2 are
supported by an electrolyzer frame 8. That is, the electrolyzer 4
is a bipolar electrolyzer comprising the plurality of electrolytic
cells 1 arranged in series and ion exchange membranes 2 each
arranged between adjacent electrolytic cells 1, and the
electrolyzer frame 8 that supports the cells 1 and the membranes 2.
As shown in FIG. 115, the electrolyzer 4 is assembled by arranging
the plurality of electrolytic cells 1 connected in series via the
ion exchange membrane 2 and coupling the cells by means of a press
device 5 in the electrolyzer frame 8. The electrolyzer frame is not
particularly limited as long as being capable of supporting each of
the member as well as coupling the members, and various known
configurations may be employed. The device for coupling each of the
members, possessed by the electrolyzer frame, is not particularly
limited, and examples thereof include hydraulic presses and devices
comprising a tie rod as a mechanism.
[1984] The electrolyzer 4 has an anode terminal 7 and a cathode
terminal 6 to be connected to a power supply. The anode 11 of the
electrolytic cell 1 located at farthest end among the plurality of
electrolytic cells 1 coupled in series in the electrolyzer 4 is
electrically connected to the anode terminal 7. The cathode 21 of
the electrolytic cell located at the end opposite to the anode
terminal 7 among the plurality of electrolytic cells 1 coupled in
series in the electrolyzer 4 is electrically connected to the
cathode terminal 6. The electric current during electrolysis flows
from the side of the anode terminal 7, through the anode and
cathode of each electrolytic cell 1, toward the cathode terminal 6.
At the both ends of the coupled electrolytic cells 1, an
electrolytic cell having an anode chamber only (anode terminal
cell) and an electrolytic cell having a cathode chamber only
(cathode terminal cell) may be arranged. In this case, the anode
terminal 7 is connected to the anode terminal cell arranged at the
one end, and the cathode terminal 6 is connected to the cathode
terminal cell arranged at the other end.
[1985] In the case of electrolyzing brine, brine is supplied to
each anode chamber 10, and pure water or a low-concentration sodium
hydroxide aqueous solution is supplied to each cathode chamber 20.
Each liquid is supplied from an electrolyte solution supply pipe
(not shown in Figure), through an electrolyte solution supply hose
(not shown in Figure), to each electrolytic cell 1. The electrolyte
solution and products from electrolysis are recovered from an
electrolyte solution recovery pipe (not shown in Figure). During
electrolysis, sodium ions in the brine migrate from the anode
chamber 10 of the one electrolytic cell 1, through the ion exchange
membrane 2, to the cathode chamber 20 of the adjacent electrolytic
cell 1. Thus, the electric current during electrolysis flows in the
direction in which the electrolytic cells 1 are coupled in series.
That is, the electric current flows, through the cation exchange
membrane 2, from the anode chamber 10 toward the cathode chamber
20. As the brine is electrolyzed, chlorine gas is generated on the
side of the anode 11, and sodium hydroxide (solute) and hydrogen
gas are generated on the side of the cathode 21.
(Anode Chamber)
[1986] The anode chamber 10 has the anode 11 or anode feed
conductor 11. The feed conductor herein referred to mean a degraded
electrode (i.e., the existing electrode), an electrode having no
catalyst coating, and the like. When the electrode for electrolysis
in the present embodiment is inserted to the anode side, 11 serves
as an anode feed conductor. When the electrode for electrolysis in
the present embodiment is not inserted to the anode side, 11 serves
as an anode. The anode chamber 10 preferably has an anode-side
electrolyte solution supply unit that supplies an electrolyte
solution to the anode chamber 10, a baffle plate that is arranged
above the anode-side electrolyte solution supply unit so as to be
substantially parallel or oblique to a partition wall 30, and an
anode-side gas liquid separation unit that is arranged above the
baffle plate to separate gas from the electrolyte solution
including the gas mixed.
(Anode)
[1987] When the electrode for electrolysis in the present
embodiment is not inserted to the anode side, an anode 11 is
provided in the frame of the anode chamber 10 (i.e., the anode
frame). As the anode 11, a metal electrode such as so-called DSA(R)
can be used. DSA is an electrode including a titanium substrate of
which surface is covered with an oxide comprising ruthenium,
iridium, and titanium as components.
[1988] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode Feed Conductor)
[1989] When the electrode for electrolysis in the present
embodiment is inserted to the anode side, the anode feed conductor
11 is provided in the frame of the anode chamber 10. As the anode
feed conductor 11, a metal electrode such as so-called DSA(R) can
be used, and titanium having no catalyst coating can be also used.
Alternatively, DSA having a thinner catalyst coating can be also
used. Further, a used anode can be also used.
[1990] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Anode-Side Electrolyte Solution Supply Unit)
[1991] The anode-side electrolyte solution supply unit, which
supplies the electrolyte solution to the anode chamber 10, is
connected to the electrolyte solution supply pipe. The anode-side
electrolyte solution supply unit is preferably arranged below the
anode chamber 10. As the anode-side electrolyte solution supply
unit, for example, a pipe on the surface of which aperture portions
are formed (dispersion pipe) and the like can be used. Such a pipe
is more preferably arranged along the surface of the anode 11 and
parallel to the bottom 19 of the electrolytic cell. This pipe is
connected to an electrolyte solution supply pipe (liquid supply
nozzle) that supplies the electrolyte solution into the
electrolytic cell 1. The electrolyte solution supplied from the
liquid supply nozzle is conveyed with a pipe into the electrolytic
cell 1 and supplied from the aperture portions provided on the
surface of the pipe to inside the anode chamber 10. Arranging the
pipe along the surface of the anode 11 and parallel to the bottom
19 of the electrolytic cell is preferable because the electrolyte
solution can be uniformly supplied to inside the anode chamber
10.
(Anode-Side Gas Separation Unit)
[1992] The anode-side gas liquid separation unit is preferably
arranged above the baffle plate. The anode-side gas liquid
separation unit has a function of separating produced gas such as
chlorine gas from the electrolyte solution during electrolysis.
Unless otherwise specified, above means the upper direction in the
electrolytic cell 1 in FIG. 112, and below means the lower
direction in the electrolytic cell 1 in FIG. 112.
[1993] During electrolysis, produced gas generated in the
electrolytic cell 1 and the electrolyte solution form a mixed phase
(gas-liquid mixed phase), which is then emitted out of the system.
Subsequently, pressure fluctuations inside the electrolytic cell 1
cause vibration, which may result in physical damage of the ion
exchange membrane. In order to prevent this event, the electrolytic
cell 1 in the present embodiment is preferably provided with an
anode-side gas liquid separation unit to separate the gas from the
liquid. The anode-side gas liquid separation unit is preferably
provided with a defoaming plate to eliminate bubbles. When the
gas-liquid mixed phase flow passes through the defoaming plate,
bubbles burst to thereby enable the electrolyte solution and the
gas to be separated. As a result, vibration during electrolysis can
be prevented.
(Baffle Plate)
[1994] The baffle plate is preferably arranged above the anode-side
electrolyte solution supply unit and arranged substantially in
parallel with or obliquely to the partition wall 30. The baffle
plate is a partition plate that controls the flow of the
electrolyte solution in the anode chamber 10. When the baffle plate
is provided, it is possible to cause the electrolyte solution
(brine or the like) to circulate internally in the anode chamber 10
to thereby make the concentration uniform. In order to cause
internal circulation, the baffle plate is preferably arranged so as
to separate the space in proximity to the anode 11 from the space
in proximity to the partition wall 30. From such a viewpoint, the
baffle plate is preferably placed so as to be opposed to the
surface of the anode 11 and to the surface of the partition wall
30. In the space in proximity to the anode partitioned by the
baffle plate, as electrolysis proceeds, the electrolyte solution
concentration (brine concentration) is lowered, and produced gas
such as chlorine gas is generated. This results in a difference in
the gas-liquid specific gravity between the space in proximity to
anode 11 and the space in proximity to the partition wall 30
partitioned by the baffle plate. By use of the difference, it is
possible to promote the internal circulation of the electrolyte
solution in the anode chamber 10 to thereby make the concentration
distribution of the electrolyte solution in the anode chamber 10
more uniform.
[1995] Although not shown in FIG. 112, a collector may be
additionally provided inside the anode chamber 10. The material and
configuration of such a collector may be the same as those of the
collector of the cathode chamber mentioned below. In the anode
chamber 10, the anode 11 per se may also serve as the
collector.
(Partition Wall)
[1996] The partition wall 30 is arranged between the anode chamber
10 and the cathode chamber 20. The partition wall 30 may be
referred to as a separator, and the anode chamber 10 and the
cathode chamber 20 are partitioned by the partition wall 30. As the
partition wall 30, one known as a separator for electrolysis can be
used, and an example thereof includes a partition wall formed by
welding a plate comprising nickel to the cathode side and a plate
comprising titanium to the anode side.
(Cathode Chamber)
[1997] In the cathode chamber 20, when the electrode for
electrolysis in the present embodiment is inserted to the cathode
side, 21 serves as a cathode feed conductor. When the electrode for
electrolysis in the present embodiment is not inserted to the
cathode side, 21 serves as a cathode. When a reverse current
absorber is included, the cathode or cathode feed conductor 21 is
electrically connected to the reverse current absorber. The cathode
chamber 20, similarly to the anode chamber 10, preferably has a
cathode-side electrolyte solution supply unit and a cathode-side
gas liquid separation unit. Among the components constituting the
cathode chamber 20, components similar to those constituting the
anode chamber 10 be not described.
(Cathode)
[1998] When the electrode for electrolysis in the present
embodiment is not inserted to the cathode side, a cathode 21 is
provided in the frame of the cathode chamber 20 (i.e., cathode
frame). The cathode 21 preferably has a nickel substrate and a
catalyst layer that covers the nickel substrate. Examples of the
components of the catalyst layer on the nickel substrate include
metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,
Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb, and Lu, and oxides and hydroxides of the metals. Examples of
the method for forming the catalyst layer include plating, alloy
plating, dispersion/composite plating, CVD, PVD, pyrolysis, and
spraying. These methods may be used in combination. The catalyst
layer may have a plurality of layers and a plurality of elements,
as required. The cathode 21 may be subjected to a reduction
treatment, as required. As the substrate of the cathode 21, nickel,
nickel alloys, and nickel-plated iron or stainless may be used.
[1999] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Cathode Feed Conductor)
[2000] When the electrode for electrolysis in the present
embodiment is inserted to the cathode side, a cathode feed
conductor 21 is provided in the frame of the cathode chamber 20.
The cathode feed conductor 21 may be covered with a catalytic
component. The catalytic component may be a component that is
originally used as the cathode and remains. Examples of the
components of the catalyst layer include metals su as Ru, C, Si, P,
S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,
Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and
hydroxides of the metals. Examples of the method for forming the
catalyst layer include plating, alloy plating, dispersion/composite
plating, CVD, PVD, pyrolysis, and spraying. These methods may be
used in combination. The catalyst layer may have a plurality of
layers and a plurality of elements, as required. Nickel, nickel
alloys, and nickel-plated iron or stainless, having no catalyst
coating may be used. As the substrate of the cathode feed conductor
21, nickel, nickel alloys, and nickel-plated iron or stainless may
be used.
[2001] As the form, any of a perforated metal, nonwoven fabric,
foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used.
(Reverse Current Absorbing Layer)
[2002] A material having a redox potential less noble than the
redox potential of the element for the catalyst layer of the
cathode mentioned above may be selected as material for the reverse
current absorbing layer. Examples thereof include nickel and
iron.
(Collector)
[2003] The cathode chamber 20 preferably comprises the collector
23. The collector 23 improves current collection efficiency. In the
present embodiment, the collector 23 is a porous plate and is
preferably arranged in substantially parallel to the surface of the
cathode 21.
[2004] The collector 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The collector 23 may be a mixture, alloy, or composite
oxide of these metals. The collector 23 may have any form as long
as the form enables the function of the collector and may have a
plate or net form.
(Metal Elastic Body)
[2005] Placing the metal elastic body 22 between the collector 23
and the cathode 21 presses each cathode 21 of the plurality of
electrolytic cells 1 connected in series onto the ion exchange
membrane 2 to reduce the distance between each anode 11 and each
cathode 21. Then, it is possible to lower the voltage to be applied
entirely across the plurality of electrolytic cells 1 connected in
series. Lowering of the voltage enables the power consumption to be
reduced. With the metal elastic body 22 placed, the pressing
pressure caused by the metal elastic body 22 enables the electrode
for electrolysis to be stably maintained in place when the laminate
including the electrode for electrolysis in the present embodiment
placed in the electro electrolytic cell.
[2006] As the metal elastic body 22, spring members such as spiral
springs and coils and cushioning mats may be used. As the metal
elastic body 22, a suitable one may be appropriately employed, in
consideration of a stress to press the ion exchange membrane and
the like. The metal elastic body 22 may be provided on the surface
of the collector 23 on the side of the cathode chamber 20 or may be
provided on the surface of the partition wall on the side of the
anode chamber 10. Both the chambers are usually partitioned such
that the cathode chamber 20 becomes smaller than the anode chamber
10. Thus, from the viewpoint of the strength of the frame and the
like, the metal elastic body 22 is preferably provided between the
collector 23 and the cathode 21 in the cathode chamber 20. The
metal elastic body 23 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium.
(Support)
[2007] The cathode chamber 20 preferably comprises the support 24
that electrically connects the collector 23 to the partition wall
30. This can achieve an efficient current flow.
[2008] The support 24 preferably comprises an electrically
conductive metal such as nickel, iron, copper, silver, and
titanium. The support 24 may have any shape as long as the support
can support the collector 23 and may have a rod, plate, or net
shape. The support 24 has a plate shape, for example. A plurality
of supports 24 are arranged between the partition wall 30 and the
collector 23. The plurality of supports 24 are aligned such that
the surfaces thereof are in parallel to each other. The supports 24
are arranged substantially perpendicular to the partition wall 30
and the collector 23.
(Anode Side Gasket and Cathode Side Gasket)
[2009] The anode side gasket is preferably arranged on the frame
surface constituting the anode chamber 10. The cathode side gasket
is preferably arranged on the frame surface constituting the
cathode chamber 20. Electrolytic cells are connected to each other
such that the anode side gasket included in one electrolytic cell
and the cathode side gasket of an electrolytic cell adjacent to the
cell sandwich the ion exchange membrane 2 (see FIG. 113). These
gaskets can impart airtightness to connecting points when the
plurality of electrolytic cells 1 is connected in series via the
ion exchange membrane 2.
[2010] The gaskets form a seal between the ion exchange membrane
and electrolytic cells. Specific examples of the gaskets include
picture frame-like rubber sheets at the center of which an aperture
portion is formed. The gaskets are required to have resistance
against corrosive electrolyte solutions or produced gas and be
usable for a long period. Thus, in respect of chemical resistance
and hardness, vulcanized products and peroxide-crosslinked products
of ethylene-propylene-diene rubber (EPDM rubber) and
ethylene-propylene rubber (EPM rubber) are usually used as the
gaskets. Alternatively, gaskets of which region to be in contact
with liquid (liquid contact portion) is covered with a
fluorine-containing resin such as polytetrafluoroethylene (PTFE)
and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA)
may be employed as required. These gaskets each may have an
aperture portion so as not to inhibit the flow of the electrolyte
solution, and the shape of the aperture portion is not particularly
limited. For example, a picture frame-like gasket is attached with
an adhesive or the like along the peripheral edge of each aperture
portion of the anode chamber frame constituting the anode chamber
10 or the cathode chamber frame constituting the cathode chamber
20. Then, for example, in the case where the two electrolytic cells
1 are connected via the ion exchange membrane 2 (see FIG. 113),
each electrolytic cell 1 onto which the gasket is attached should
be tightened via ion exchange membrane 2. This tightening can
prevent the electrolyte solution, alkali metal hydroxide, chlorine
gas, hydrogen gas, and the like generated from electrolysis from
leaking out of the electrolytic cells 1.
[Laminate]
[2011] In the method for producing an electrolyzer according to the
present embodiment, the electrode for electrolysis can be used as a
laminate of a membrane such as an ion exchange membrane or a
microporous membrane. That is, the laminate in the present
embodiment comprises the electrode for electrolysis and a new
membrane. The new membrane is not particularly limited as long as
being separate from the membrane in the existing electrolyzer, and
various known "membranes" can be used. The material, form, physical
properties, and the like of the new membrane may be similar to
those of the membrane in the existing electrolyzer. Specific
examples of the electrode for electrolysis and the membrane will be
detailed below.
(Step (A))
[2012] In the step (A) in the first aspect, fixing of the membrane
is released in the electrolyzer frame. "In the electrolyzer frame"
means that the step (A) is performed while a state is maintained in
which the electrolytic cell (that is, the member comprising the
anode and the cathode) and the membrane are supported by the
electrolyzer frame, and an aspect in which the electrolytic cell is
removed from the electrolyzer frame is excluded. Examples of a
method for releasing a fixing of the membrane include, but not
particularly limited to, a method in which pressing by a press
device in the electrolyzer frame is released to form a gap between
the electrolytic cell and the membrane so as to enable the membrane
to be removable to the outside of the electrolyzer frame. In the
step (A), fixing of the membrane is preferably released in the
electrolyzer frame by sliding the anode and the cathode in the
arrangement direction thereof, respectively. The operation enables
the membrane to be removable to the outside of the electrolyzer
frame without removing the electrolytic cell to the outside of the
electrolyzer frame.
[Step (B)]
[2013] In the step (B) in the first aspect, the membrane in the
existing electrolyzer is replaced by a laminate after the step (A).
Examples of the replacing method include, but not particularly
limited to, a method in which a gap is formed between the
electrolytic cell and the ion exchange membrane, then, the existing
membrane to be renewed is removed, and then, a laminate is inserted
into the gap. By means of the method, a laminate can be arranged on
the surface of the anode or the cathode of the existing
electrolyzer, and the characteristics of the ion exchange membrane
and the anode and/or cathode can be renewed.
[2014] After the step (B) is performed, the laminate is preferably
fixed in the electrolyzer frame by pressing from the anode and the
cathode. Specifically, after the membrane is replaced by the
laminate the existing electrolyzer, the laminate and the members in
the existing electrolyzer such as the electrolytic cell can be
coupled by pressing again by means of the press device. By means of
the method, a laminate can be fixed on the surface of the anode or
the cathode in the existing electrolyzer.
[2015] A specific example of the steps (A) to (B) in the first
aspect will be described based on FIGS. 117(A) and (B). First,
pressing by a press device 5 is released, and a plurality of
electrolytic cells 1 and ion exchange membranes 2 are slid in the
arrangement direction thereof .alpha.. This enables a gap S to be
formed between the electrolytic cell 1 and the ion exchange
membrane 2 without removing the electrolytic cell 1 to the outside
of the electrolyzer frame 8, and the ion exchange membrane 2 become
removable to the outside of the electrolyzer frame 8. Subsequently,
the ion exchange membrane 2 to be replaced of the existing
electrolyzer is removed out of the electrolyzer frame 8, and a
laminate 9 of a new ion exchange membrane 2a and an electrode for
electrolysis 100 instead is inserted between adjacent electrolytic
cells 1 (that is, the gap S). In this manner, the laminate 9 is
arranged between the adjacent electrolytic cells 1, and these
components become supported by the electrolyzer frame 8. Then, the
plurality of electrolytic cells 1 and the laminate 9 are coupled by
being pressed in the arrangement direction .alpha. by means of the
press device S.
(Step (A'))
[2016] Also in the step (A') in the second aspect, fixing of the
membrane is released in the electrolyzer frame, as in the first
aspect. Also in the step (A'), fixing of the membrane is preferably
released in the electrolyzer frame by sliding the anode and the
cathode in the arrangement direction thereof, respectively. The
operation enables the membrane to be removable to the outside of
the electrolyzer frame without removing the electrolytic cell to
the outside of the electrolyzer frame.
[Step (B')]
[2017] In the step (B') in the second aspect, an electrode for
electrolysis is arranged between the membrane and the anode or
cathode after the step (A'). Examples of the method for arranging
an electrode for electrolysis include, but not particularly
limited, a method in which, for example, a gap is formed between
the electrolytic cell and the ion exchange membrane, and then, an
electrode for electrolysis is inserted into the gap. By means of
the method, the electrode for electrolysis can be arranged on the
surface of the anode or cathode in the existing electrolyzer, and
the characteristics of the anode or cathode can be renewed.
[2018] After the step (B') is performed, the electrode for
electrolysis is preferably fixed in electrolyzer frame by pressing
from the anode and the cathode. Specifically, after the electrode
for electrolysis is arranged on the surface of the anode or cathode
in the existing electrolyzer, the electrode for electrolysis and
the members in the existing electrolyzer such as the electrolytic
cell can be coupled by pressing again by means of the press device.
By means of the method, a laminate can be fixed on the surface of
the anode or the cathode in the existing electrolyzer.
[2019] A specific example of the steps (A') to (B') in the second
aspect will be described based on FIGS. 118(A) and (B). First,
pressing by a press device 5 is released, and a plurality of
electrolytic cells 1 and ion exchange membranes 2 are slid in the
arrangement direction thereof .alpha.. This enables a gap S to be
formed between the electrolytic cell 1 and the ion exchange
membrane 2 without removing the electrolytic cell 1 to the outside
of the electrolyzer frame 8. Then, the electrode for electrolysis
100 is inserted between the adjacent electrolytic cells 1 (that is,
into the gap S) In this manner, the electrode for electrolysis 100
is arranged between the adjacent electrolytic cells 1, and these
components become supported by the electrolyzer frame 8. Then, the
plurality of electrolytic cells 1 and the electrode for
electrolysis 100 are coupled by being pressed in the arrangement
direction a by means of the press device 5.
[2020] In the step (B) in the first aspect, the laminate is
preferably fixed on the surface of at least one of the anode and
cathode at a temperature at which the laminate does not melt.
[2021] The "temperature at which the laminate does not melt" can be
identified as the softening point of the new membrane. The
temperature may vary depending on the material constituting the
membrane but is preferably 0 to 100.degree. C., more preferably 5
to 80.degree. C., further preferably 10 to 50.degree. C.
[2022] The fixing described above is preferably performed under
normal pressure.
[2023] Further, the laminate is preferably obtained by integrating
the electrode for electrolysis and the new membrane at a
temperature at which the membrane does not melt and then used in
the step (B).
[2024] As a specific method for the above integration, which are
not particularly limited, all kinds of methods, except for typical
methods for melting the membrane such as thermal compression can be
used. One preferable example is a method in which a liquid is
interposed between an electrode for electrolysis mentioned below
and the membrane and the surface tension of the liquid is used to
integrate the electrode and the membrane.
[Electrode for Electrolysis]
[2025] In the method for producing an electrolyzer according to the
present embodiment, the electrode for electrolysis is not
particularly limited as long as the electrode can be used for
electrolysis. The electrode for electrolysis may be an electrode
that serves as the cathode in the electrolyzer or may be an
electrode that serves as an anode. As the material, form, and the
like of the electrode for electrolysis, those suitable may be
appropriately selected, in consideration of the configuration of
the electrolyzes and the like. Hereinbelow, preferable aspects of
the electrode for electrolysis in the present embodiment will be
described, but these are merely exemplary preferable aspects for a
case in which the electrode is integrated with a new membrane to
form a laminate in the first aspect. Electrodes for electrolysis
other than the aspects mentioned below can be appropriately
employed.
[2026] The electrode for electrolysis in the present embodiment has
a force applied per unit massunit area of preferably 1.6
N/(mgcm.sup.2) or less, more preferably less than 1.6
N/(mgcm.sup.2), further preferably less than 1.5 N/(mgcm.sup.2),
even further preferably 1.2 N/mgcm.sup.2 or less, still more
preferably 1.20 N/mgcm.sup.2 or less from the viewpoint of enabling
a good handling property to be provided and having a good adhesive
force to a membrane such as an ion exchange membrane and a
microporous membrane, a feed conductor (a degraded electrode and an
electrode having no catalyst coating), and the like. The force
applied is even still more preferably 1.1 N/mgcm.sup.2 or less,
further still more preferably 1.10 N/mgcm.sup.2 or less,
particularly preferably 1.0 N/mgcm.sup.2 or less, especially
preferably 1.00 N/mgcm.sup.2 or less.
[2027] From the viewpoint of further improving the electrolytic
performance, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/mgcm.sup.2 or more, further more
preferably 0.14 N/(mgcm.sup.2) or more. The force is further more
preferably 0.2 N/(mgcm.sup.2) or more from the viewpoint of further
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[2028] The force applied described above can be within the range
described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, arithmetic average
surface roughness, and the like, for example. More specifically,
for example, a higher opening ratio tends to lead to a smaller
force applied, and a lower opening ratio tends to lead to a larger
force applied.
[2029] The mass per unit is preferable 48 mg/cm.sup.2 or less, more
preferably 30 mg/cm.sup.2 or less, further preferably 20
mg/cm.sup.2 or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode, a feed conductor having no catalyst coating,
and of economy, and furthermore is preferably 15 mg/cm.sup.2 or
less from the comprehensive viewpoint including handling property,
adhesion, and economy. The lower limit value is not particularly
limited but is of the order of 1 mg/cm.sup.2, for example.
[2030] The mass per unit area described above can be within the
range described above by appropriately adjusting an opening ratio
described below, thickness of the electrode, and the like, for
example. More specifically, for example, when the thickness is
constant, a higher opening ratio tends to lead to a smaller mass
per unit area, and a lower opening ratio tends to lead to a larger
mass per unit area.
[2031] The force applied can be measured by methods (i) or (ii)
described below, which are as detailed in Examples. As for the
force applied, the value obtained by the measurement of the method
(i) (also referred to as "the force applied (1)") and the value
obtained by the measurement of the method (ii) (also referred to as
"the force applied (2)") may be the same or different, and either
of the values is preferably less than 1.5 N/mgcm.sup.2.
[Method (i)]
[2032] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion
exchange membrane which is obtained by applying inorganic material
particles and a binder to both surfaces of a membrane of a
perfluorocarbon polymer into which an ion exchange group is
introduced (170 mm square, the detail of the ion exchange membrane
referred to herein is as described in Examples), and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurement. The arithmetic average surface roughness
(Ra) of the nickel plate after the blast treatment is 0.5 to 0.8
.mu.m. The specific method for calculating the arithmetic average
surface roughness (Ra) is as described in Examples.
[2033] Under conditions of a temperature of 23+2.degree. C. and a
relative humidity of 30.+-.5%, only the sample of electrode in this
sample for measurement is raised in a vertical direction at 10
mm/minute using a tensile and compression testing machine, and the
load when the sample of electrode is raised by 10 mm in a vertical
direction is measured. This measurement is repeated three times,
and the average value is calculated.
[2034] This average value is divided by the area of the overlapping
portion of the sample of electrode and the ion exchange membrane
and the mass of the portion overlapping the ion exchange membrane
in the sample of electrode to calculate the force applied per unit
massunit area (1) (N/mgcm.sup.2).
[2035] The force applied per unit massunit area (1) obtained by the
method (i) preferably 1.6 N/(mgcm.sup.2) or less, more preferably
less than 1.6 N/(mgcm.sup.2), further preferably less than 1.5
N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2 or less,
still more preferably 1.20 N/mgcm.sup.2 or less from the viewpoint
of enabling a good handling property to be provided and having a
good adhesive force to a membrane such as an ion exchange membrane
and a microporous membrane, a degraded electrode, and a feed
conductor having no catalyst coating. The force applied is ever
still more preferably 1.1 N/mgcm.sup.2 or less, further still more
preferably 1.10 N/mgcm.sup.2 or less, particularly preferably 1.0
N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2 or
less. The force is preferably more Than 0.005 N/(mgcm.sup.2), more
preferably 0.08 N/(mgcm.sup.2) or more, further preferably 0.1
N/(mgcm.sup.2) or more from the viewpoint of further improving the
electrolytic performance, and furthermore, is further more
preferably 0.14 N/(mgcm.sup.2), still more preferably 0.2
N/(mgcm.sup.2) or more from the viewpoint of further facilitating
handling in a large size (e.g., a size of 1.5 m.times.2.5 T).
[Method (ii)]
[2036] A nickel plate obtained by blast processing with alumina of
grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel
plate similar to that of the method (i) above) and a sample of
electrode (130 mm square) are laminated in this order. After this
laminate is sufficiently immersed in pure water, excess water
deposited on the surface of the laminate is removed to obtain a
sample for measurements. Under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, only the
sample of electrode in this sample for measurement is raised in a
vertical direction at 10 mm/minute using a tensile and compression
testing machine, and the load when the sample of electrode is
raised by 10 mm in a vertical direction is measured. This
measurement is repeated three times, and the average value is
calculated.
[2037] This average value is divided by the area of the overlapping
portion of the sample of electrode and the nickel plate and the
mass of the sample of electrode in the portion overlapping the
nickel plate to calculate the adhesive force per unit massunit area
(2) (N/mgcm.sup.2).
[2038] The force applied per unit massunit area (2) obtained by the
method (ii) is preferably 1.6 N/(mgcm.sup.2) or less, more
preferably less than 1.6 N/(mgcm.sup.2), further preferably less
than 1.5 N/(mgcm.sup.2), even further preferably 1.2 N/mgcm.sup.2
or less, still more preferably 1.20 N/mgcm.sup.2 or less from the
viewpoint of enabling a good handling property to be provided and
having a good adhesive force to a membrane such as an ion exchange
membrane and a microporous membrane, a degraded electrode, and a
feed conductor having no catalyst coating. The force applied is
even still more preferably 1.1 N/mgcm.sup.2 or less, further still
more preferably 1.10 N/mgcm.sup.2 or less, particularly preferably
1.0 N/mgcm.sup.2 or less, especially preferably 1.00 N/mgcm.sup.2
or less. Further, the force is preferably more than 0.005
N/(mgcm.sup.2), more preferably 0.08 N/(mgcm.sup.2) or more,
further preferably 0.1 N/(mgcm.sup.2) or more from the viewpoint of
further improving the electrolytic performance, and is further more
preferably 0.14 N/(mgcm.sup.2) or more from the viewpoint of
further facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m).
[2039] The electrode for electrolysis in the present embodiment
preferably includes a substrate for electrode for electrolysis and
a catalyst layer. The thickness of the substrate for electrode for
electrolysis (gauge thickness) is, but is not particularly limited
to, preferably 300 .mu.m or less, more preferably 205 .mu.m or
less, further preferably 155 .mu.m or less, further more preferably
135 .mu.m or less, even further more preferably 125 .mu.m or less,
still more preferably 120 .mu.m or less, even still more preferably
100 .mu.m or less from the viewpoint of enabling a good handling
property to be provided, having a good adhesive force to a membrane
such as an ion exchange membrane and a microporous membrane, a
degraded electrode (feed conductor), and an electrode (feed
conductor) having no catalyst coating, being capable of being
suitably rolled in a roll and satisfactorily folded, and
facilitating handling in a large size (e.g., a size of 1.5
m.times.2.5 m), and is further still more preferably 50 .mu.m or
less from the viewpoint of a handling property and economy. The
lower limit value is not particularly limited, but is 1 .mu.m, for
example, preferably 5 .mu.m, more preferably 15 .mu.m.
[2040] In the method for producing an electrolyzer according to the
present embodiment, in order to integrate a new membrane and the
electrode for electrolysis, a liquid is preferably interposed
therebetween. As the liquid, any liquid, such as water and organic
solvents, can be used as long as the liquid generates a surface
tension. The larger the surface tension of the liquid, the larger
the force applied between the new membrane and the electrode for
electrolysis. Thus, a liquid having a larger surface tension is
preferred. Examples of the liquid include the following (the
numerical value in the parentheses is the surface tension of the
liquid at 20.degree. C.):
[2041] hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00
mN/m), ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and
water (72.76 mN/m).
[2042] A liquid having a large surface tension allows the new
membrane and the electrode for electrolysis to be integrated (to be
a laminate), and renewing of the electrode tends to be easier. The
liquid between the new membrane and the electrode for electrolysis
may be present in an amount such that the both adhere to each other
by the surface tension. As a result, after the laminate is placed
in an electrolytic cell, the liquid, if mixed into the electrolyte
solution, does not affect electrolysis itself due to the small
amount of the liquid.
[2043] From a practical viewpoint, a liquid having a surface
tension of 24 mN/m to 80 mN/m, such as ethanol, ethylene glycol,
and water, is preferably used as the liquid. Particularly preferred
is water or an alkaline aqueous solution prepared by dissolving
caustic soda, potassium hydroxide, lithium hydroxide, sodium
hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate,
potassium carbonate, or the like in water. Alternatively, the
surface tension can be adjusted by allowing these liquids to
contain a surfactant. When a surfactant is contained, the adhesion
be the new membrane and the electrode for electrolysis varies to
enable the handling property to be adjusted. The surfactant is not
particularly limited, and both ionic surfactants and nonionic
surfactants may be used.
[2044] The proportion measured by the following method (2) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 90% or more, more
preferably 92% or more from the viewpoint of enabling a good
handling property to be provided and having a good adhesive force
to a membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and further preferably
95% or more from the viewpoint of further facilitating handling a
large size (e.g., a size of 1.5 m.times.2.5 m). The upper limit
value is 100%.
[Method (2)]
[2045] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 280 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[2046] The proportion measured by the following method (3) of the
electrode for electrolysis in the present embodiment is not
particularly limited, but is preferably 75% or more, more
preferably 80% or more from tte viewpoint of enabling a good
handling property to be provided, having a good adhesive force to a
membrane such as an ion exchange membrane and a microporous
membrane, a degraded electrode (feed conductor), and an electrode
(feed conductor) having no catalyst coating, and being capable of
being suitably rolled in a roll and satisfactorily folded, and is
further preferably 90% or more from the viewpoint of further
facilitating handling in a lame size (e.g., a size of 1.5
m.times.2.5 m). The upper limit value is 100%.
[Method (3)]
[2047] An ion exchange membrane (170 mm square) and a sample of
electrode (130 mm square) are laminated in this order. The laminate
is placed on a curved surface of a polyethylene pipe (outer
diameter: 145 mm) such that the sample of electrode in this
laminate is positioned outside under conditions of a temperature of
23.+-.2.degree. C. and a relative humidity of 30.+-.5%, the
laminate and the pipe are sufficiently immersed in pure water,
excess water deposited on a surface of the laminate and the pipe is
removed, and one minute after this removal, then the proportion (%)
of an area of a portion in which the ion exchange membrane (170 mm
square) is in close contact with the sample of electrode is
measured.
[2048] The electrode for electrolysis in the present embodiment
preferably has, but is not particularly limited to, a porous
structure and an opening ratio or void ratio of 5 to 90% or less,
from the viewpoint of enabling a good handling property, to be
provided, having a good adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode
(feed conductor), and an electrode (feed conductor) having no
catalyst coating, and preventing accumulation of gas to be
generated during electrolysis. The opening ratio is more preferably
10 to 80% or less, further preferably 20 to 75%.
[2049] The opening ratio is a proportion of the opening portions
per unit volume. The calculation method may differ depending on
that opening portions in submicron size are considered or that only
visible openings are considered. In the present embodiment, a
volume V is calculated from the values of the gauge thickness,
width, and length of electrode, and further, a weight W is measured
to thereby enable an opening ratio A to be calculated by the
following formula.
A=(1-(W/(V.times..rho.)).times.100
[2050] .rho. is the density of the electrode material (g/cm.sup.3).
For example, .rho. of nickel is 8.908 g/cm.sup.3, and .rho. of
titanium is 4.506 g/cm.sup.3. The opening ratio can be
appropriately adjusted by changing the area of metal to be
perforated per unit area in the case of perforated metal, changing
the values of the SW (short diameter), LW (long diameter), and feed
in the case of expanded metal, changing the line diameter of metal
fiber and mesh number in the case of mesh, changing the pattern or
a photoresist to be used in the case of electroforming, changing
the metal fiber diameter and fiber density in the case of nonwoven
fabric, changing the mold for forming voids in the case of foamed
metal, or the like.
[2051] Hereinbelow, a more specific embodiment of the electrode for
electrolysis in the present embodiment will be described.
[2052] The electrode for electrolysis according to the present
embodiment preferably includes a substrate for electrode for
electrolysis and a catalyst layer. The catalyst layer may be
composed of a plurality of layers as shown below or may be a
single-layer configuration.
[2053] As shown in FIG. 119, an electrode for electrolysis 100
according to the present embodiment includes a substrate for
electrode for electrolysis 10 and a pair of first layers 20 with
which both the surfaces of the substrate for electrode for
electrolysis 10 are covered. The entire substrate for electrode for
electrolysis 10 is preferably covered with the first layers 20.
This covering is likely to improve the catalyst activity and
durability of the electrode for electrolysis. One first layer 20
may be laminated only on one surface of the substrate for electrode
for electrolysis 10.
[2054] Also as shown in FIG. 119, the surfaces of the first layers
20 may be covered with second layers 30. The entire first layers 20
are preferably covered by the second layers 30. Alternatively, one
second layer 30 may be laminated only one surface of the first
layer 20.
(Substrate for Electrode for Electrolysis)
[2055] As the substrate for electrode for electrolysis 10, for
example, nickel, nickel alloys, stainless steel, or valve metals
including titanium can be used, although not limited thereto. The
substrate 10 preferably contains at least one element selected from
nickel (Ni) and titanium (Ti).
[2056] When stainless steel is used in an alkali aqueous solution
of a high concentration, iron and chromium are eluted and the
electrical conductivity of stainless steel is of the order of
one-tenth of that of nickel. In consideration of the foregoing, a
substrate containing nickel (Ni) is preferable as the substrate for
electrode for electrolysis.
[2057] Alternatively, when the substrate for electrode for
electrolysis 10 is used in a salt solution of a high concentration
near the saturation under an atmosphere in which chlorine gas is
generated, the material of the substrate for electrode 10 is also
preferably titanium having high corrosion resistance.
[2058] The form of the substrate for electrode for electrolysis 10
is not particularly limited, and a form suitable for the purpose
can be selected. As the form, any of a perforated metal, nonwoven
fabric, foamed metal, expanded metal, metal porous foil formed by
electroforming, so-called woven mesh produced by knitting metal
lines, and the like can be used. Among these, a perforated metal or
expanded metal is preferable. Electroforming is a technique for
producing a metal thin film having a precise pattern by using
photolithography and electroplating in combination. It is a method
including forming a pattern on a substrate with a photoresist and
electroplating the portion not protected by the resist to provide a
metal thin film.
[2059] As for the form of the substrate for electrode for
electrolysis, a suitable specification depends on the distance
between the anode and the cathode in the electrolyzer. In the case
where the distance between the anode and the cathode is finite, an
expanded metal or perforated metal form can be used, and in the
case of a so-called zero-gap base electrolyzer, in which the ion
exchange membrane is in contact with the electrode, a woven mesh
produced by knitting thin lines, wire mesh, foamed metal, metal
nonwoven fabric, expanded metal, perforated metal, metal porous
foil, and the like can be used, although not limited thereto.
[2060] Examples of the substrate for electrode for electrolysis 10
include a metal porous foil, a wire mesh, a metal nonwoven fabric,
a perforated metal, an expanded metal, and a foamed metal.
[2061] As a plate material before processed into a perforated metal
or expanded metal, rolled plate materials and electrolytic foils
are preferable. An electrolytic foil is preferably further
subjected to a plating treatment by use of the same element as the
base material thereof, as the post-treatment, to thereby form
asperities on one or both of the surfaces.
[2062] The thickness of the substrate for electrode for
electrolysis 10 is, as mentioned above, preferably 300 .mu.m or
less, more preferably 205 .mu.m or less, further preferably 155
.mu.m or less, further more preferably 135 .mu.m or less, even
further more preferably 125 .mu.m or less, still more preferably
120 .mu.m or less, even still more preferably 100 .mu.m or less,
and further still more preferably 50 .mu.m or less from the
viewpoint of a handling property and economy. The lower limit value
is not particularly limited, but is 1 .mu.m, for example,
preferably 5 .mu.m, more preferably 15 .mu.m.
[2063] In the substrate for electrode for electrolysis, the
residual stress during processing is preferably relaxed by
annealing the substrate for electrode for electrolysis in an
oxidizing atmosphere. It is preferable to form asperities using a
steel grid, alumina powder, or the like on the surface of the
substrate for electrode for electrolysis followed by an acid
treatment to increase the surface area thereof, in order to improve
the adhesion to a catalyst layer with which the surface is covered.
Alternatively, it is preferable to give a plating treatment by use
of the same element as the substrate to increase the surface
area.
[2064] To bring the first layer 20 into close contact with the
surface of the substrate for electrode for electrolysis 10, the
substrate for electrode for electrolysis 10 is preferably subjected
to a treatment of increasing the surface area. Examples of the
treatment of increasing the surface area include a blast treatment
using a cut wire, steel grid, alumina grid or the like, an acid
treatment using sulfuric acid or hydrochloric acid, and a plating
treatment using the same element to that of the substrate. The
arithmetic average surface roughness (Ra) of the substrate surface
is not particularly limited, but is preferably 0.05 .mu.m to 50
.mu.m, more preferably 0.1 to 10 .mu.m, further preferably 0.1 to 8
.mu.m.
[2065] Next, a case where the electrode for electrolysis in the
present embodiment is used as an anode for common salt electrolysis
will be described.
(First Layer)
[2066] In FIG. 119, a first layer 20 as a catalyst layer contains
at least one of ruthenium oxides, iridium oxides, and titanium
oxides. Examples of the ruthenium oxide include RuO.sub.2. Examples
of the iridium oxide include IrO.sub.2. Examples of the titanium
oxide include TiO.sub.2. The first layer 20 preferably contains two
oxides: a ruthenium oxide and a titanium oxide or three oxides: a
ruthenium oxide, an iridium oxide, and a titanium oxide. This makes
the first layer 20 more stable and additionally improves the
adhesion with the second layer 30.
[2067] When the first layer 20 contains two oxides: a ruthenium
oxide and a titanium oxide, the first layer 20 contains preferably
1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based
on 1 mol of the ruthenium oxide contained in the first layer 20.
With the composition ratio of the two oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[2068] When the first layer 20 contains three oxides: a ruthenium
oxide, an iridium oxide, and a titanium oxide, the first layer 20
contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of
the iridium oxide based on 1 mol of the ruthenium oxide contained
in the first layer 20. The first layer 20 contains preferably 0.3
to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on
1 mol of the ruthenium oxide contained in the first layer 20. With
the composition ratio of the three oxides in this range, the
electrode for electrolysis 100 exhibits excellent durability.
[2069] When the first layer 20 contains at least two of a ruthenium
oxide, an iridium oxide, and a titanium oxide, these oxides
preferably form a solid solution. Formation of the oxide solid
solution allows the electrode for electrolysis 100 to exhibit
excellent durability.
[2070] In addition to the compositions described above, oxides of
various compositions can be used as long as at least one oxide of a
ruthenium oxide, an iridium oxide, and titanium oxide is contained.
For example, an oxide coating called DSA(R), which contains
ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt,
manganese, platinum, and the like, can be used as the first layer
20.
[2071] The first layer 20 need not be a single layer and may
include a plurality of layers. For example, the first layer 20 may
include a layer containing three oxides and a layer containing two
oxides. The thickness of the first layer 20 is preferably 0.05 to
10 more preferably 0.1 to 8 .mu.m.
(Second Layer)
[2072] The second layer 30 preferably contains ruthenium and
titanium. This enables the chlorine overvoltage immediately after
electrolysis to be further lowered.
[2073] The second layer 30 preferably contains a palladium oxide, a
solid solution of a palladium oxide and platinum, or an alloy of
palladium and platinum. This enables the chlorine overvoltage
immediately after electrolysis to be further lowered.
[2074] A thicker second layer 30 can maintain the electrolytic
performance for a longer period, but from the viewpoint of economy,
the thickness is preferably 0.05 to 3 .mu.m.
[2075] Next, a case where the electrode for electrolysis in the
present embodiment is used as a cathode for common salt
electrolysis will be described.
(First Layer)
[2076] Examples of components of the first layer 20 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[2077] The first layer 20 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
[2078] When the first layer 20 contains at least one of platinum
group metals, platinum group metal oxides, platinum group metal
hydroxides, and alloys containing a platinum group metal, the
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal
preferably contain at least one platinum group metal of platinum,
palladium, rhodium, ruthenium, and iridium.
[2079] As the platinum group metal, platinum is preferably
contained.
[2080] As the platinum group metal oxide, a ruthenium oxide is
preferably contained.
[2081] As the platinum group metal hydroxide, a ruthenium hydroxide
is preferably contained.
[2082] As the platinum group metal alloy, an alloy of platinum with
nickel, iron, and cobalt is preferably contained.
[2083] Further, as required, an oxide or hydroxide of a lanthanoid
element is preferably contained as a second component. This allows
the electrode for electrolysis 100 to exhibit excellent
durability.
[2084] As the oxide or hydroxide of a lanthanoid element, at least
one selected from lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, and dysprosium
is preferably contained.
[2085] Further, as required, an oxide or hydroxide of a transition
metal is preferably contained as a third component.
[2086] Addition of the third component enables the electrode for
electrolysis 100 to exhibit more excellent durability and the
electrolysis voltage to be lowered.
[2087] Examples of a preferable combination include ruthenium only,
ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,
ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,
ruthenium+praseodymium, ruthenium+praseodymium+platinum,
ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,
ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,
ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,
ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,
ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,
ruthenium+neodymium+nickel, ruthenium+neodymium+copper,
ruthenium+samarium, ruthenium+samarium+manganese,
ruthenium+samarium+iron, ruthenium+samarium+cobalt,
ruthenium+samarium+zinc, ruthenium+samarium+gallium,
ruthenium+samarium+sulfur, ruthenium+samarium+lead,
ruthenium+samarium+nickel, platinum+cerium,
platinum+palladium+cerium, platinum+palladium+lanthanum+cerium,
platinum+iridium, platinum+palladium, platinum+iridium+palladium,
platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of
platinum and nickel, alloys of platinum and cobalt, and alloys of
platinum and iron.
[2088] When platinum group metals, platinum group metal oxides,
platinum group metal hydroxides, and alloys containing a platinum
group metal are not contained, the main component of the catalyst
is preferably nickel element.
[2089] At least one of nickel metal, oxides, and hydroxides is
preferably contained.
[2090] As the second component, a transition metal may be added. As
the second component to be added, at least one element of titanium,
tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and
carbon is preferably contained.
[2091] Examples of a preferable combination include nickel+tin,
nickel+titanium, nickel+molybdenum, and nickel+cobalt.
[2092] As required, an intermediate layer can be placed between the
first layer 20 and the substrate for electrode for electrolysis 10.
The durability of the electrode for electrolysis 100 can be
improved by placing the intermediate layer.
[2093] As the intermediate layer, those having affinity to both the
first layer 20 and the substrate for electrode for electrolysis 10
are preferable. As the intermediate layer, nickel oxides, platinum
group metals, platinum group metal oxides, and platinum group metal
hydroxides are preferable. The intermediate layer can be formed by
applying and baking a solution containing a component that forms
the intermediate layer. Alternatively, a surface oxide layer also
can be formed by subjecting a substrate to a thermal treatment at a
temperature of 300 to 600.degree. C. in an air atmosphere. Besides,
the layer can be formed by a known method such as a thermal
spraying method and ion plating method.
(Second Layer)
[2094] Examples of components of the first layer 30 as the catalyst
layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W,
Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the
metals.
[2095] The first layer 30 may or may not contain at least one of
platinum group metals, platinum group metal oxides, platinum group
metal hydroxides, and alloys containing a platinum group metal.
Examples of a preferable combination of elements contained in the
second layer include the combinations enumerated for the first
layer. The combination of the first layer and the second layer may
be a combination in which the compositions are the same and the
composition ratios are different or may be a combination of
different compositions.
[2096] As the thickness of the catalyst layer, the total thickness
of the catalyst layer formed and the intermediate layer is
preferably 0.01 .mu.m to 20 .mu.m. With a thickness of 0.01 .mu.m
or more, the catalyst layer can sufficiently serve as the catalyst.
With a thickness of 20 .mu.m or less, it is possible to form a
robust catalyst layer that is unlikely to fall off from the
substrate. The thickness is more preferably 0.05 .mu.m to 15 .mu.m.
The thickness is more preferably 0.1 .mu.m to 10 .mu.m. The
thickness is further preferably 0.2 .mu.m to 8 .mu.m.
[2097] The thickness of the electrode, that is, the total thickness
of the substrate for electrode for electrolysis and the catalyst
layer is preferably 315 .mu.m or less, more preferably 220 .mu.m or
less, further preferably 170 .mu.m or less, further more preferably
150 .mu.m or less, particularly preferably 145 .mu.m or less, still
more preferably 140 .mu.m or less, even still more preferably 138
.mu.m or less, further still more preferably 135 .mu.m or less in
respect of the handling property of the electrode. A thickness of
135 .mu.m or less can provide a good handling property. Further,
from a similar viewpoint as above, the thickness is preferably 130
.mu.m or less, more preferably less than 130 .mu.m, further
preferably 115 .mu.m or less, further more preferably 65 .mu.m or
less. The lower limit value is not particularly limited, but is
preferably 1 .mu.m or more, more preferably 5 .mu.m or more for
practical reasons, more preferably 20 .mu.m or more. The thickness
of the electrode can be determined by measurement with a digimatic
thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The
thickness of the substrate for electrode for electrolysis is
measured in the same manner as the thickness of the electrode. The
thickness of the catalyst layer can be determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
[2098] In method for producing an electrolyzer according to the
present embodiment, the electrode for electrolysis preferably
contains at least one catalytic component selected from the group
consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni,
Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge,
B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy
from the viewpoint of achieving sufficient electrolytic
performance.
[2099] In the present embodiment, from the viewpoint that the
electrode for electrolysis, if being an electrode having a broad
elastic deformation region, can provide a better handling property
and has a better adhesive force to a membrane such as an ion
exchange membrane and a microporous membrane, a degraded electrode,
a feed conductor having no catalyst coating, and the like, the
thickness of the electrode for electrolysis is preferably 315 .mu.m
or less, more preferably 220 .mu.m or less, further preferably 170
.mu.m or less, further more preferably 150 .mu.m or less,
particularly preferably 145 .mu.m or less, still more preferably
140 .mu.m or less, even still more preferably 138 .mu.m or less,
further still more preferably 135 .mu.m or less. A thickness of 135
.mu.m or less can provide a good handling property. Further, from a
similar viewpoint as above, the thickness is preferably 130 .mu.m
or less, more preferably less than 130 .mu.m, further preferably
115 .mu.m or less, further more preferably 65 .mu.m or less. The
lower limit value is not particularly limited, but is preferably 1
.mu.m or more, more preferably 5 .mu.m or more for practical
reasons, more preferably 20 .mu.m or more. In the present
embodiment, "having a broad elastic deformation region" means that,
when an electrode for electrolysis is wound to form a wound body,
warpage derived from winding is unlikely to occur after the wound
state is released. The thickness of the electrode for electrolysis
refers to, when a catalyst layer mentioned below is included, the
total thickness of both the substrate for electrode for
electrolysis and the catalyst layer.
(Method for Producing Electrode for Electrolysis)
[2100] Next, one embodiment of the method for producing the
electrode for electrolysis 100 will be described in detail.
[2101] In the present embodiment, the electrode for electrolysis
100 can be produced by forming the first layer 20, preferably the
second layer 30, on the substrate for electrode for electrolysis by
a method such as baking of a coating film under an oxygen
atmosphere (pyrolysis), or plating, plating, or thermal spraying.
The production method of the present embodiment as mentioned can
achieve a high productivity of the electrode for electrolysis 100.
Specifically, a catalyst formed on the substrate for electrode for
electrolysis by an application step of applying a coating liquid
containing a catalyst, a drying step of crying the coating liquid,
and a pyrolysis step of performing pyrolysis. Pyrolysis herein
means that a metal salt which is to be a precursor is decomposed by
heating into a metal or metal oxide and a gaseous substance. The
decomposition product depends on the metal species to be used, type
of the salt, and the atmosphere under which pyrolysis performed,
and many metals tend to form oxides in an oxidizing atmosphere. In
an industrial process of producing an electrode, pyrolysis is
usually performed in air, and a metal oxide or a metal hydroxide is
formed in many cases.
(Formation of First Layer of Anode)
(Application Step)
[2102] The first layer 20 is obtained by applying a solution in
which at least one metal salt of ruthenium, iridium, and titanium
is dissolved (first coating liquid) onto the substrate for
electrode for electrolysis and then pyrolyzing (baking) the coating
liquid in the presence of oxygen. The content of ruthenium,
iridium, and titanium in the first coating liquid is substantially
equivalent to that of the first layer 20.
[2103] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration in the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[2104] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[2105] After being applied onto the substrate for electrode for
electrolysis 100, the first coating liquid is dried at a
temperature of 10 to 90.degree. C. and pyrolyzed in a baking
furnace heated to 350 to 650.degree. C. Between the drying and
pyrolysis, preliminary baking at 100 to 350.degree. C. may be
performed as required. The drying, preliminary baking, and
pyrolysis temperature can be appropriately selected depending on
the composition and the solvent type of the first coating liquid. A
longer time period of pyrolysis per step is preferable, but from
the viewpoint of the productivity of the electrode, 3 to 60 minutes
is preferable, 5 to 20 minutes is more preferable.
[2106] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a long period as required can further
improve the stability of the first layer 20.
(Formation of Second Layer)
[2107] The second layer 30, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound and a platinum compound or a solution containing
a ruthenium compound and a titanium compound (second coating
liquid) onto the first layer 20 and then pyrolyzing the coating
liquid in the presence of oxygen.
(Formation of First Layer of Cathode by Pyrolysis Method)
(Application Step)
[2108] The first layer 20 is obtained by applying a solution in
which metal salts various combination are dissolved (first coating
liquid) onto the substrate for electrode for electrolysis and then
pyrolyzing (baking) the coating liquid in the presence of oxygen.
The content of the metal in the first coating liquid is
substantially equivalent to that in the first layer 20.
[2109] The metal salts may be chlorides, nitrates, sulfates, metal
alkoxides, and any other forms. The solvent of the first coating
liquid can be selected depending on the type of the metal salt, and
water and alcohols such as butanol can be used. As the solvent,
water or a mixed solvent of water and an alcohol is preferable. The
total metal concentration the first coating liquid in which the
metal salts are dissolved is not particularly limited, but is
preferably in the range of 10 to 150 g/L in association with the
thickness of the coating film to be formed by a single coating.
[2110] Examples of a method used as the method for applying the
first coating liquid onto the substrate for electrode for
electrolysis 10 include a dipping method of immersing the substrate
for electrode for electrolysis 10 in the first coating liquid, a
method of brushing the first coating liquid, a roll method using a
sponge roll impregnated with the first coating liquid, and an
electrostatic coating method in which the substrate for electrode
for electrolysis 10 and the first coating liquid are oppositely
charged and spraying is performed. Among these, preferable is the
roll method or electrostatic coating method, which has an excellent
industrial productivity.
(Drying Step and Pyrolysis Step)
[2111] After being applied onto the substrate for electrode for
electrolysis 10, the first coating liquid is dried at a temperature
of 10 to 90.degree. C. and pyrolyzed in a baking furnace heated to
350 to 650.degree. C. Between the drying and pyrolysis, preliminary
baking at 100 to 350.degree. C. may be performed as required. The
drying, preliminary baking, and pyrolysis temperature can be
appropriately selected depending on the composition and the solvent
type of the first coating liquid. A longer time period of pyrolysis
per step is preferable, but from the viewpoint of the productivity
of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is
more preferable.
[2112] The cycle of application, drying, and pyrolysis described
above is repeated to form a covering (the first layer 20) to a
predetermined thickness. After the first layer 20 is formed and
then further post-baked for a lone period as required can further
improve the stability of the first layer 20.
(Formation of Intermediate Layer)
[2113] The intermediate layer, which is formed as required, is
obtained, for example, by applying a solution containing a
palladium compound or platinum compound (second coating liquid)
onto the substrate and then pyrolyzing the coating liquid in the
presence of oxygen. Alternatively, a nickel oxide intermediate
layer may be formed on the substrate surface only by heating the
substrate, without applying a solution thereon.
(Formation of First Layer of Cathode by Ion Plating)
[2114] The first layer 20 can be formed also by ion plating.
[2115] An example includes a method in which the substrate is fixed
in a chamber and the metal ruthenium target is irradiated with an
electron beam. Evaporated metal ruthenium particles are positively
charged in plasma in the chamber to deposit on the substrate
negatively charged. The plasma atmosphere is argon and oxygen, and
ruthenium deposits as ruthenium oxide on the substrate.
(Formation of First Layer of Cathode by Plating)
[2116] The first layer 20 can be formed also by a plating
method.
[2117] As an example, when the substrate is used as the cathode and
subjected to electrolytic plating in an electrolyte solution
containing, nickel and tin, alloy plating of nickel and tin can be
formed.
(Formation of First Layer of Cathode by Thermal spraying)
[2118] The first layer 20 can be formed also by thermal
spraying.
[2119] As an example, plasma spraying nickel oxide particles onto
the substrate can form a catalyst layer in which metal nickel and
nickel oxide are mixed.
[2120] Hereinafter, an ion exchange membrane according to one
aspect of the membrane will be described in detail.
[Ion Exchange Membrane]
[2121] The ion exchange membrane is not particularly limited as
long as the membrane can be laminated with the electrode for
electrolysis, and various ion exchange membranes may be employed.
In the method for producing an electrolyzer according to the
present embodiment, an ion exchange membrane that has a membrane
body containing a hydrocarbon polymer or fluorine-containing
polymer having an ion exchange group and a coating layer provided
on at least one surface of the membrane body is preferably used. It
is preferable that the coating layer contain inorganic material
particles and a binder and the specific surface area of the coating
layer be 0.1 to 10 m.sup.2/g. The ion exchange membrane having such
a structure has a small influence of gas generated during
electrolysis on electrolytic performance and tends to exert stable
electrolytic performance.
[2122] The membrane of a perfluorocarbon polymer into which an ion
exchange group is introduced described above includes either one of
a sulfonic acid layer having an ion exchange group derived from a
sulfo group (a group represented by --SO.sub.3.sup.-, hereinbelow
also referred to as a "sulfonic acid group") or a carboxylic acid
layer having an ion exchange group derived from a carboxyl group (a
group represented by --CO.sub.2.sup.-, hereinbelow also referred to
as a "carboxylic acid group"). From the viewpoint of strength and
dimension stability, reinforcement core materials are preferably
further included.
[2123] The inorganic material particles and binder will be
described in detail in the section of description of the coating
layer below.
[2124] FIG. 120 illustrates a cross-sectional schematic view
showing one embodiment of an ion exchange membrane. An ion exchange
membrane 1 has a membrane body 10 containing a hydrocarbon polymer
or fluorine-containing polymer having an ion exchange group and
coating layers 11a and 11b formed on both the surfaces of the
membrane body 10.
[2125] In the ion exchange membrane 1, the membrane body 10
comprises a sulfonic acid layer 3 having an ion exchange group
derived from a sulfo group (a group represented by hereinbelow also
referred to as a "sulfonic acid group") and a carboxylic acid layer
2 having an ion exchange group derived from a carboxyl group group
represented by --CO.sub.2--, hereinbelow also referred to as a
"carboxylic acid group"), and the reinforcement core materials 4
enhance the strength and dimension stability. The ion exchange
membrane 1, as comprising the sulfonic acid layer 3 and the
carboxylic acid layer 2, is suitably used as an anion exchange
membrane.
[2126] The ion exchange membrane may include either one of the
sulfonic acid layer and the carboxylic acid layer. The ion exchange
membrane may not be necessarily reinforced by reinforcement core
materials, and the arrangement of the reinforcement core materials
is not limited to the example in FIG. 120.
(Membrane Body)
[2127] First, the membrane body 10 constituting the ion exchange
membrane 1 will be described.
[2128] The membrane body 10 should be one that has a function of
selectively allowing cations to permeate and comprises a
hydrocarbon polymer or a fluorine-containing polymer having an ion
exchange group. Its configuration and material are not particularly
limited, and preferred ones can be appropriately selected.
[2129] The hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group in the membrane body 10 can be
obtained from a hydrocarbon polymer or fluorine-containing polymer
having an ion exchange group precursor capable of forming an ion
exchange group by hydrolysis or the like. Specifically, for
example, after a polymer comprising a main chain of a fluorinated
hydrocarbon, having, as a pendant side chain, a group convertible
into an ion exchange group by hydrolysis or the like (ion exchange
group precursor), and being melt-processable (hereinbelow, referred
to as the "fluorine-containing polymer (a)" in some cases) is used
to prepare a precursor of the membrane body 10, the membrane body
10 can be obtained by converting the ion exchange group precursor
into an ion exchange group.
[2130] The fluorine-containing polymer (a) can be produced, for
example, by copolymerizing at least one monomer selected from the
following first group and at least one monomer selected from the
following second group and/or the following third group. The
fluorine-containing polymer (a) can be also produced by
homopolymerization of one monomer selected from any of the
following first group, the following second group, and the
following third group.
[2131] Examples of the monomers of the first group include vinyl
fluoride compounds. Examples of the vinyl fluoride compounds
include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene,
and perfluoro alkyl vinyl ethers. Particularly when the ion
exchange membrane is used as a membrane for alkali electrolysis,
the vinyl fluoride compound preferably a perfluoro monomer, and a
perfluoro monomer selected from the group consisting of
tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl
ethers is preferable.
[2132] Examples of the monomers of the second group include vinyl
compounds having a functional group convertible into a carboxylic
acid-type ion exchange group (carboxylic acid group). Examples of
the vinyl compounds having a functional group convertible into a
carboxylic acid group include monomers represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.2--O(CZF).sub.t--COOR, wherein s
represents an integer of 0 to 2, t represents an integer of 1 to
12, Y and Z each independently represent F or CF.sub.3, and R
represents a lower alkyl group (a lower alkyl group is an alkyl
group having 1 to 3 carbon atoms, for example).
[2133] Among these, compounds represented by
CF.sub.2.dbd.CF(OCF.sub.2CYF).sub.n--O(CF.sub.2).sub.m--COOR are
preferable. Wherein n represents an integer of 0 to 2, m represents
an integer of 1 to 4, Y represents F or CF.sub.3, and R represents
CH.sub.3, C.sub.2H.sub.5, or C.sub.3H.sub.7.
[2134] When the ion exchange membrane is used as a cation exchange
membrane for alkali electrolysis, a perfluoro compound is
preferably at least used as the monomer, but the alkyl group (see
the above R) of the ester group is lost from the polymer at the
time of hydrolysis, and therefore the alkyl group (R) need not be a
perfluoroalkyl group in which all hydrogen atoms are replaced by
fluorine atoms.
[2135] Of the above monomers, the monomers represented below are
more preferable as the monomers of the second group:
[2136]
CF.sub.2.dbd.CFOCF.sub.2--CF(CF.sub.3)OCF.sub.2COOCH.sub.3,
[2137]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2COOCH.sub.3,
[2138]
CF.sub.2.dbd.CF[OCF.sub.2--CF(CF.sub.3)].sub.2O(CF.sub.2).sub.2COOC-
H.sub.3,
[2139]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.3COOCH.sub.3,
[2140] CF.sub.2.dbd.CFO(CF.sub.2).sub.2COOCH.sub.3, and
[2141] CF.sub.2.dbd.CFO(CF.sub.2).sub.3COOCH.sub.3.
[2142] Examples of the monomers of the third group include vinyl
compounds having a functional group convertible into a sulfone-type
ion exchange group (sulfonic acid group). As the vinyl compounds
having a functional group convertible into a sulfonic acid group,
for example, monomers represented by
CF.sub.2.dbd.CFO--X--CF.sub.2--SO.sub.2F are preferable, wherein X
represents a perfluoroalkylene group. Specific examples of these
include the monomers represented below:
[2143] CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
[2144]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F,
[2145]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub-
.2F,
[2146] CF.sub.2.dbd.CF(CF.sub.2).sub.2SO.sub.2F,
[2147]
CF.sub.2.dbd.CFO[CF.sub.2CF(CF.sub.3)O].sub.2CF.sub.2CF.sub.2SO.sub-
.2F, and
[2148]
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2OCF.sub.3)OCF.sub.2CF.sub.2SO.su-
b.2F.
[2149] Among these,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2CF.sub.2SO.sub.2F
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F
are more preferable.
[2150] The copolymer obtained from these monomers can be produced
by a polymerization method developed for homopolymerization and
copolymerization of ethylene fluoride, particularly a general
polymerization method used for tetrafluoroethylene. For example, in
a non-aqueous method, a polymerization reaction can be performed in
the presence of a radical polymerization initiator such as a
perfluorocarbon peroxide or an azo compound under the conditions of
a temperature of 0 to 200.degree. C. and a pressure of 0.1 to 20
MPa using an inert solvent such as a perfluorohydrocarbon or a
chlorofluorocarbon.
[2151] In the above copolymerization, the type of combination of
the above monomers and their proportion are not particularly
limited and are selected and determined depending on the type and
amount of the functional group desired to be imparted to the
fluorine-containing polymer to be obtained. For example, when a
fluorine-containing polymer containing only a carboxylic acid group
is formed, at least one monomer should be selected from each of the
first group and the second group described above and copolymerized.
In addition, when a fluorine-containing polymer containing only a
sulfonic acid group is formed, at least one monomer should be
selected from each of the first group and the third group and
copolymerized. Further, when a fluorine-containing polymer having a
carboxylic acid group and a sulfonic acid group is formed, at least
one monomer should be selected from each of the first group, the
second group, and the third group described above and
copolymerized. In this case, the target fluorine-containing polymer
can be obtained also by separately preparing a copolymer comprising
the monomers of the first group and the second group described
above and a copolymer comprising the monomers of the first group
and the third group described above, and then mixing the
copolymers. The mixing proportion of the monomers is not
particularly limited, and when the amount of the functional groups
per unit polymer is increased, the proportion of the monomers
selected from the second group and the third group described above
should be increased.
[2152] The total ion exchange capacity of the fluorine-containing
copolymer is not particularly limited, but is preferably 0.5 to 2.0
mg equivalent/g, more preferably 0.6 to 1.5 mg equivalent/g. The
total ion exchange capacity herein refers to the equivalent of the
exchange group per unit weight of the dry resin and can be measured
by neutralization titration or the like.
[2153] In the membrane body 10 of the ion exchange membrane 1, a
sulfonic acid layer 3 containing a fluorine-containing polymer
having a sulfonic acid group and a carboxylic acid layer 2
containing a fluorine-containing polymer having a carboxylic acid
group are laminated. By providing the membrane body 10 having such
a layer configuration, selective permeability for cations such as
sodium ions can be further improved.
[2154] The ion exchange membrane 1 is arranged in an electrolyzer
such that, usually, the sulfonic acid layer 3 is located on the
anode side of the electrolyzer and the carboxylic acid layer
located on the cathode side of the electrolyzer.
[2155] The sulfonic acid layer 3 is preferably constituted by a
material having low electrical resistance and has a membrane
thickness larger than that of the carboxylic acid layer 2 from the
viewpoint of membrane strength. The membrane thickness of the
sulfonic acid layer 3 is preferably 2 to 25 times, more preferably
3 to 15 times that of the carboxylic acid layer 2.
[2156] The carboxylic acid layer 2 preferably has high anion
exclusion properties even if it has a small membrane thickness. The
anion exclusion properties here refer to the property of trying to
hinder intrusion and permeation of anions into and through the ion
exchange membrane 1. In order to raise the anion exclusion
properties, it is effective to dispose a carboxylic acid layer
having a small ion exchange capacity to the sulfonic acid
layer.
[2157] As the fluorine-containing polymer for use in the sulfonic
acid layer 3, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F as
the monomer of the third group.
[2158] As the fluorine-containing polymer for use in the carboxylic
acid layer 2, preferable is a polymer obtained by using
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)O(CF.sub.2COOCH.sub.3 as the
monomer of the second group.
(Coating Layer)
[2159] The ion exchange membrane preferably has a coating layer on
at least one surface of the membrane body. As shown in FIG. 120, in
the ion exchange membrane 1, coating layers 11a and 11b are formed
on both the surfaces of the membrane body 10.
[2160] The coating layers contain inorganic material particles and
a binder.
[2161] The average particle size of the inorganic material
particles is preferably 0.90 .mu.m or more. When the average
particle size of the inorganic material particles is 0.90 .mu.m or
more, durability to impurities is extremely improved, in addition
to attachment of gas. That is, enlarging the average particle size
of the inorganic material particles as well as satisfying the value
of the specific surface area mentioned above can achieve a
particularly marked effect. Irregular inorganic material particles
are preferable because the average particle size and specific
surface area as above are satisfied. Inorganic material particles
obtained by melting and inorganic material particles obtained by
grinding raw ore can be used. Inorganic material particles obtained
by grinding raw ore can preferably be used.
[2162] The average particle size of the inorganic material
particles can be 2 .mu.m or less. When the average particle size of
the inorganic material particles is 2 .mu.m or less, it is possible
to prevent damage of the membrane due to the inorganic material
particles. The average particle size of the inorganic material
particle is more preferably0.90 to 1.2 .mu.m.
[2163] Here, the average particle size can be measured by particle
size analyzer ("SALD2200", SHIMADZU CORPORATION).
[2164] The inorganic material particles preferably have irregular
shapes. Such shapes improve resistance to impurities further. The
inorganic material particles preferably have a broad particle size
distribution.
[2165] The inorganic material particles preferably contain at least
one inorganic material selected from the group consisting of oxides
of Group IV elements in the Periodic Table, nitrides of Group IV
elements in the Periodic Table, and carbides of Group IV elements
in the Periodic Table. From the viewpoint of durability, zirconium
oxide particle is more preferable.
[2166] The inorganic material particles are preferably inorganic
material particles produced by grinding the raw ore of the
inorganic material particles or inorganic material particles, as
spherical particles having a uniform diameter, obtained by
melt-purifying the raw ore of the inorganic material particles.
[2167] Examples of means for grinding raw ore include, but are not
particularly limited to, ball mills, bead mills, colloid mills,
conical mills, disc mills, edge mills, grain mills, hammer mills,
pellet mills, VSI mills, Wiley mills, roller mills, and jet mills.
After grinding, the particles are preferably washed. As the washing
method, the particles are preferably treated with acid. This
treatment can reduce impurities such as iron attached to the
surface of the inorganic material particles.
[2168] The coating layer preferably contains a binder. The binder
is a component that forms the coating layers by retaining the
inorganic material particles on the surface of the ion exchange
membrane. The binder preferably contains a fluorine-containing
polymer from the viewpoint of durability to the electrolyte
solution and products from electrolysis.
[2169] As the binder, a fluorine-containing polymer having a
carboxylic acid group or sulfonic acid group is more preferable,
from the viewpoint of durability to the electrolyte solution and
products from electrolysis and adhesion to the surface of the ion
exchange membrane. When a coating layer is provided on a layer
containing a fluorine-containing polymer having a sulfonic acid
group (sulfonic acid layer), a fluorine-containing polymer having a
sulfonic acid group is further preferably used as the binder of the
coating layer. Alternatively, when a coating layer is provided on a
layer containing a fluorine-containing polymer having a carboxylic
acid group (carboxylic acid layer), a fluorine-containing polymer
having a carboxylic acid group is further preferably used as the
binder of the coating layer.
[2170] In the coating layer, the content of the inorganic material
particles is preferably 40 to 90% by mass, more preferably 50 to
90% by mass. The content of the binder is preferably 10 to 60% by
mass, more preferably 10 to 50% by mass.
[2171] The distribution density of the coating layer in the ion
exchange membrane is preferably 0.05 to 2 mg per 1 cm.sup.2. When
the ion exchange membrane has asperities on the surface thereof,
the distribution density of the coating layer is preferably 0.5 to
2 mg per 1 cm.sup.2.
[2172] As the method for forming the coating layer, which is not
particularly limited, a known method, can be used. An example is a
method including applying by a spray or the like a coating liquid
obtained by dispersing inorganic material particles in a solution
containing, a binder.
(Reinforcement Core Materials)
[2173] The ion exchange membrane preferably has reinforcement core
materials arranged, inside the membrane body.
[2174] The reinforcement core materials are members that enhance
the strength and dimensional stability of the ion exchange
membrane. By arranging the reinforcement core materials inside the
membrane body, particularly expansion and contraction of the ion
exchange membrane can be controlled in the desired range. Such an
ion exchange membrane does not expand or contract more than
necessary during electrolysis and the like and can maintain
excellent dimensional stability for a long term.
[2175] The configuration of the reinforcement core materials is not
particularly limited, and, for example, the reinforcement core
materials may be formed by spinning yarns referred to as
reinforcement yarns. The reinforcement yarns here refer to yarns
that are members constituting the reinforcement core materials, can
provide the desired dimensional stability and mechanical strength
to the ion exchange membrane, and can be stably present in the ion
exchange membrane. By using the reinforcement core materials
obtained by spinning such reinforcement yarns, better dimensional
stability and mechanical strength can be provided to the ion
exchange membrane.
[2176] The material the reinforcement core materials and the
reinforcement yarns used for these is not particularly limited but
is preferably a material resistant to acids, alkalis, etc., and a
fiber comprising a fluorine-containing polymer is preferable
because long-term heat resistance and chemical resistance are
required.
[2177] Examples of the fluorine-containing polymer to be used in
the reinforcement core materials include polytetrafluoroethylene
(PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers
(PFA), tetrafluoroethylene-ethylene copolymers (ETFE),
tetrafluoroethylene-hexafluoropropylene copolymers,
trifluorochloroethylene-ethylene copolymers, and vinylidene
fluoride polymers (PVDF). Among these, fibers comprising
polytetrafluoroethylene are preferably used from the viewpoint of
heat resistance and chemical resistance.
[2178] The yarn diameter of the reinforcement yarns used for the
reinforcement core materials is not particularly limited, but is
preferably 20 to 300 deniers, more preferably 50 to 250 deniers.
The weave density (fabric count per unit length) is preferably 5 to
50/inch. The form of the reinforcement core materials is not
particularly limited, for example, a woven fabric, a nonwoven
fabric, and a knitted fabric are used, but is preferably in the
form of a woven fabric. The thickness of the woven fabric to be
used is preferably 30 to 250 .mu.m, more preferably 30 to 150
.mu.m.
[2179] As the woven fabric or knitted fabric, monofilaments,
multifilaments, or yarns thereof, a slit yarn, or the like can be
used, and various types of weaving methods such as a plain weave, a
leno weave, a knit weave, a cord weave, and a seersucker can be
used.
[2180] The weave and arrangement of the reinforcement core
materials in the membrane body are not particularly limited, and
preferred arrangement can be appropriately provided considering the
size and form of the ion exchange membrane, physical properties
desired for the ion exchange membrane, the use environment, and the
like.
[2181] For example, the reinforcement core materials may be
arranged along one predetermined direction of the membrane body,
but from the viewpoint of dimensional stability, it is preferred
that the reinforcement core materials be arranged along a
predetermined first direction, and other reinforcement core
materials be arranged along a second direction substantially
perpendicular to the first direction. By arranging the plurality of
reinforcement core materials substantially orthogonally inside the
membrane body, it is possible to impart better dimensional
stability and mechanical strength in many directions. For example,
arrangement in which the reinforcement core materials arranged
along the longitudinal direction (warp yarns) and the reinforcement
core materials arranged along the transverse direction (weft yarns)
are woven on the surface side of the membrane body is preferred.
The arrangement is more preferably in the form of plain weave
driven and woven by allowing warps and wefts to run over and under
each other alternately, leno weave in which two warps are woven
into wefts while twisted, basket weave driven and woven by
inserting, into two or more parallelly-arranged warps, wefts of the
same number, or the like, from the viewpoint of dimension
stability, mechanical strength and easy-production.
[2182] It is preferred that particularly, the reinforcement core
materials be arranged along both directions, the MD (Machine
Direction) and TD (Transverse Direction) of the ion exchange
membrane. In other words, the reinforcement core materials are
preferably plain-woven in the MD and TD. Here, the MD refers to the
direction in which the membrane body and various core materials
(for example, the reinforcement core materials, reinforcement
yarns, and sacrifice yarns described later) are conveyed in an ion
exchange membrane production step described later (flow direction),
and the TD refers to the direction substantially perpendicular to
the MD. Yarns woven along the MD are referred to as MD yarns, and
yarns woven along the TD are referred to as TD yarns. Usually, the
ion exchange membrane used for electrolysis is rectangular, and in
many cases, the longitudinal direction is the MD, and the width
direction is the TD. By weaving the reinforcement core materials
that are MD yarns and the reinforcement core materials that are TD
yarns, it is possible to impart better dimensional stability and
mechanical strength in many directions.
[2183] The arrangement interval of the reinforcement core materials
is not particularly limited, and preferred arrangement can be
appropriately provided considering physical properties desired for
the ion exchange membrane, the use environment, and the like.
[2184] The aperture ratio for the reinforcement core materials is
not particularly limited, but is preferably 30% or more, more
preferably 50% or more and 90% or less. The aperture ratio is
preferably 30% or more from the viewpoint of the electrochemical
properties of the ion exchange membrane, and preferably 90% or less
from the viewpoint of the mechanical strength of the ion exchange
membrane.
[2185] The aperture ratio for the reinforcement core materials
herein refers to a ratio of a total area of a surface through which
substances such as ions (an electrolyte solution and cations
contained therein (e.g., sodium ions)) can pass (B) to the area of
either one surface of the membrane body (A) (B/A). The total area
of the surface through which substances such as ions can pass (B)
can refer to the total areas of regions in which in the ion
exchange membrane, cations, an electrolytic solution, and the like
are not blocked by the reinforcement core materials and the like
contained in the ion exchange membrane.
[2186] FIG. 121 illustrates a schematic view for explaining the
aperture ratio of reinforcement core materials constituting the ion
exchange membrane. FIG. 121, in which a portion of the ion exchange
membrane is enlarged, shows only the arrangement of the
reinforcement core materials 21 and 22 in the regions, omitting
illustration of the other members.
[2187] By subtracting the total area of the reinforcement core
materials (C) from the area of the region surrounded by the
reinforcement core materials 21 arranged along the longitudinal
direction and the reinforcement core materials 22 arranged along
the transverse direction, the region including the area of the
reinforcement core materials (A), the total area of regions through
which substances such as ions can pass (B) in the area of the
above-described region (A) can be obtained. That is, the aperture
ratio can be determined by the following formula (I):
Aperature ratio=(B)/(A)=((A)-(C))/(A) (I)
[2188] Among the reinforcement core materials, a particularly
preferred form is tape yarns or highly oriented monofilaments
comprising PTFE from the viewpoint of chemical resistance and heat
resistance. Specifically, reinforcement core materials forming a
plain weave in which 50 to 300 denier tape yarns obtained by
slitting a high strength porous sheet comprising PTFE into a tape
form, or 50 to 300 denier highly oriented monofilaments comprising
PTFE are used and which has a weave density of 10 to 50 yarns or
monofilaments/inch and has a thickness in the range of 50 to 100
.mu.m are more preferred. The aperture ratio of an ion exchange
membrane comprising such reinforcement core materials is further
preferably 60% or more.
[2189] Examples of the shape of the reinforcement yarns Include
round yarns and tape yarns.
(Continuous Holes)
[2190] The ion exchange membrane preferably has continuous holes
inside the membrane body.
[2191] The continuous holes refer to holes that can be flow paths
for ions generated in electrolysis and an electrolyte solution. The
continuous holes, which are tubular holes formed inside the
membrane body, are formed by dissolution of sacrifice core
materials (or sacrifice yarns) described below The shape, diameter,
or the like of the continuous holes can be controlled by selecting
the shape or diameter of the sacrifice core materials (sacrifice
yarns).
[2192] Forming the continuous holes inside the ion exchange
membrane can ensure the mobility of an electrolyte solution on
electrolysis. The shape of the continuous holes is not particularly
limited, but may be the shape sacrifice core materials to be used
for formation of the continuous holes in accordance with the
production method described below.
[2193] The continuous holes are preferably formed so as to
alternately pass on the anode side (sulfonic acid layer side) and
the cathode side (carboxylic acid layer side) of the reinforcement
core materials. With such a structure, in a portion in which
continuous holes are formed on the cathode side of the
reinforcement core materials, ions (e.g., sodium ions) transported
through the electrolyte solution with which the continuous holes
are filled can flow also on the cathode side of the reinforcement
core materials. As a result, the flow of cations is not
interrupted, and thus, it is possible to further reduce the
electrical resistance of the ion exchange membrane.
[2194] The continuous holes may be formed along only one
predetermined direction of the membrane body constituting the ion
exchange membrane, but are preferably formed in both the
longitudinal direction and the transverse direction of the membrane
body from the viewpoint of exhibiting more stable electrolytic
performance.
[Production Method]
[2195] A suitable example of a method for producing an ion exchange
membrane includes a method including the following steps (1) to
(6):
[2196] Step (1): the step of producing a fluorine-containing
polymer having an ion exchange group or an ion exchange group
precursor capable of forming an ion exchange group by
hydrolysis,
[2197] Step (2): the step of weaving at least a plurality of
reinforcement core materials, as required, and sacrifice yarns
having a property of dissolving in an acid or an alkali, and
forming continuous holes, to obtain a reinforcing material in which
the sacrifice yarns are arranged between the reinforcement core
materials adjacent to each other,
[2198] Step (3): the step of forming into a film the above
fluorine-containing polymer having an ion exchange group or an ion
exchange group precursor capable of forming an ion exchange group
by hydrolysis,
[2199] Step (4): the step of embedding the above reinforcing
materials, as required, in the above film to obtain a membrane body
inside which the reinforcing materials are arranged,
[2200] Step (5): the step of hydrolyzing the membrane body obtained
in the step (4) (hydrolysis step), and
[2201] Step (6): the step of providing a coating layer on the
membrane body obtained in the step (5) (application step).
[2202] Hereinafter, each of the steps will be described in
detail.
[2203] Step (1): Step of Producing Fluorine-Containing Polymer
[2204] In the step (1), raw material monomers described in the
first group to the third group above are used to produce a
fluorine-containing polymer. In order to control the ion exchange
capacity of the fluorine-containing polymer, the mixture ratio of
the raw material monomers should be adjusted in the production of
the fluorine-containing polymer forming the layers.
[2205] Step (2): Step of Producing Reinforcing Materials
[2206] The reinforcing material is a woven fabric obtained weaving
reinforcement yarns or the like. The reinforcing material is
embedded in the membrane to thereby form reinforcement core
materials. When an ion exchange membrane having continuous holes is
formed, sacrifice yarns are additionally woven into the reinforcing
material. The amount of the sacrifice yarns contained in this case
is preferably 10 to 80% by mass, more preferably 30 to 70% by mass
based on the entire reinforcing material. Weaving the sacrifice
yarns can also prevent yarn slippage of the reinforcement core
materials.
[2207] As the sacrifice yarns, which have solubility in the
membrane production step or under an electrolysis environment,
rayon, polyethylene terephthalate (PET), cellulose, polyamide, and
the like are used. Monofilaments or multifilaments having a
thickness of 20 to 50 deniers and comprising polyvinyl alcohol and
the like are also preferred.
[2208] In the step (2), the aperture ratio, arrangement of the
continuous holes, and the like can be controlled by adjusting the
arrangement of the reinforcement core materials and the sacrifice
yarns.
[2209] Step (3): Step of Film Formation
[2210] In the step (3), the fluorine-containing polymer obtained in
the step (1) is formed into a film by using an extruder. The film
may be a single-layer configuration, a two-layer configuration of a
sulfonic acid layer and a carboxylic acid layer as mentioned above,
or a multilayer configuration of three layers or more.
[2211] Examples of the film forming method include the
following:
[2212] a method in which a fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are separately formed into films; and
[2213] a method in which fluorine-containing polymer having a
carboxylic acid group and a fluorine-containing polymer having a
sulfonic acid group are coextruded into a composite film.
[2214] The number of each film may be more than one. Coextrusion of
different films is preferred because of its contribution to an
increase in the adhesive strength in the interface.
[2215] Step (4): Step of Obtaining Membrane Body
[2216] In the step (4), the reinforcing material obtained in the
step (2) is embedded in the film obtained in the step (3) to
provide a membrane body including the reinforcing material
therein.
[2217] Preferable examples of the method for forming a membrane
body include a method in which a fluorine-containing polymer having
a carboxylic acid group precursor (e.g., carboxylate functional
group) (hereinafter, a layer comprising the same is referred to as
the first layer) located on the cathode side and a
fluorine-containing, polymer having a sulfonic acid group precursor
(e.g., sulfonyl fluoride functional group) (hereinafter, a layer
comprising the same is referred to as the second layer) are formed
into a film by a coextrusion method, and, by using a heat source
and a vacuum source as required, a reinforcing material and the
second layer/first layer composite film are laminated in this order
on breathable heat-resistant release paper on a flat plate or drum
having many pores on the surface thereof and integrated at a
temperature at which each polymer melts while air among each of the
layers was evacuated by reduced pressure; and (ii) a method in
which, in addition to the second layer/first layer composite film,
a fluorine-containing polymer having a sulfonic acid group
precursor is singly formed into a film (the third layer) in
advance, and, by using a heat source and a vacuum source as
required, the third layer film, the reinforcement core materials,
and the composite film comprising the second layer/first layer are
laminated in this order on breathable heat-resistant release paper
on a flat plate or drum having many pores on the surface thereof
and integrated at a temperature at which each polymer melts while
air among each of the layers was evacuated by reduced pressure.
[2218] Coextrusion of the first layer and the second layer herein
contributes to an increase in the adhesive strength at the
interface.
[2219] The method including integration under a reduced pressure is
characterized by making the third layer on the reinforcing material
thicker than that of a pressure-application press method. Further,
since the reinforcing material is fixed on the inner surface of the
membrane body, the method has a property of sufficiently retaining
the mechanical strength of the ion exchange membrane.
[2220] The variations of lamination described here are exemplary,
and coextrusion can be performed after a preferred lamination
pattern (for example, the combination of layers) is appropriately
selected considering the desired layer configuration of the
membrane body and physical properties, and the like.
[2221] For the purpose of further improving the electric properties
of the ion exchange membrane, it is also possible to additionally
interpose a fourth layer comprising a fluorine-containing polymer
having both a carboxylic acid group precursor and a sulfonic acid
group precursor between the first layer and the second layer or to
use a fourth layer comprising a fluorine-containing polymer having
both a carboxylic acid group precursor and a sulfonic acid group
precursor instead of the second layer.
[2222] The method for forming the fourth layer may be a method in
which a fluorine-containing polymer having a carboxylic acid group
precursor and a fluorine-containing polymer having a sulfonic acid
group precursor are separately produced and then mixed or may be a
method in which a monomer having a carboxylic acid group precursor
and a monomer having a sulfonic acid group precursor are
copolymerized.
[2223] When the fourth layer is used as a component of the ion
exchange membrane, a coextruded film of the first layer and the
fourth layer is formed, in addition to this, the third layer and
the second layer are separately formed into films, and lamination
may be performed by the method mentioned above. Alternatively, the
three layers of the first layer/fourth layer/second layer may be
simultaneously formed into a film by coextrusion.
[2224] In this case, the direction in which the extruded film flows
is the MD. As mentioned above, it is possible to form a membrane
body containing a fluorine-containing polymer having an ion
exchange group on a reinforcing material.
[2225] Additionally, the ion exchange membrane preferably has
protruded portions composed of the fluorine-containing polymer
having a sulfonic acid group, that projections, on the surface side
composed of the sulfonic acid layer. As a method for forming such
projections, which is not particularly limited, a known method also
can be employed including forming projections on a resin surface. A
specific example of the method is a method of embossing the surface
of the membrane body. For example, the above projections can be
formed by using release paper embossed in advance when the
composite film mentioned above, reinforcing material, and the like
are integrated. In the case where projections are formed by
embossing, the height and arrangement density of the projections
can be controlled by controlling the emboss shape to be transferred
(shape of the release paper).
(5) Hydrolysis Step
[2226] In the step (5), a step of hydrolyzing the membrane body
obtained in the step (4) to convert the ion exchange group
precursor into an ion exchange group (hydrolysis step) is
performed.
[2227] In the step (5), it is also possible to form dissolution
holes in the membrane body by dissolving and removing the sacrifice
yarns included in the membrane body with acid or alkali. The
sacrifice yarns may remain in the continuous holes without being
completely dissolved and removed. The sacrifice yarns remaining in
the continuous holes may be dissolved and removed by the
electrolyte solution when the ion exchange membrane is subjected to
electrolysis.
[2228] The sacrifice yarn has solubility in acid or alkali in the
step of producing an ion exchange membrane or under an electrolysis
environment. The sacrifice yarns are eluted out to thereby form
continuous holes at corresponding sites.
[2229] The step (5) can be performed by immersing the membrane body
obtained in the step (4) in a hydrolysis solution containing acid
or alkali. An example of the hydrolysis solution that can be used
is a mixed solution containing KOH and dimethyl sulfoxide
(DMSO).
[2230] The mixed solution preferably contains KOH of 2.5 to 4.0 N
and DMSO of 25 to 35% by mass.
[2231] The temperature for hydrolysis is preferably 70 to
100.degree. C. The higher the temperature, the larger can be the
apparent thickness. The temperature is more preferably 75 to
100.degree. C.
[2232] The time for hydrolysis is preferably 10 to 120 minutes. The
longer the time, the larger can be the apparent thickness. The time
is more preferably 20 to 120 minutes.
[2233] The step of forming continuous holes by eluting the
sacrifice yarn will be now described in more detail. FIGS. 122(a)
and (b) are schematic views for explaining a method for forming the
continuous holes of the ion exchange membrane.
[2234] FIGS. 122(a) and (b) show reinforcement yarns 52, sacrifice
yarns 504a, and continuous holes 504 formed by the sacrifice yarns
504a only, omitting illustration of the other members such as a
membrane body.
[2235] First, the reinforcement yarns 52 that are to constitute
reinforcement core materials in the ion exchange membrane and the
sacrifice yarns 504a for forming the continuous holes 504 in the
ion exchange membrane are used as interwoven reinforcing materials.
Then, in the step (5), the sacrifice yarns 504a are eluted to form
the continuous holes 504.
[2236] The above method is simple because the method for
interweaving the reinforcement yarns 52 and the sacrifice yarns
504a may be adjusted depending on the arrangement of the
reinforcement core materials and continuous holes in the membrane
body of the ion exchange membrane.
[2237] FIG. 122(a) exemplifies the plain-woven reinforcing material
in which the reinforcement yarns 52 and sacrifice yarns 504a are
interwoven along both the longitudinal direction and the lateral
direction in the paper, and the arrangement of the reinforcement
yarns 52 and the sacrifice yarns 504a in the reinforcing material
may be varied as required.
(6) Application Step
[2238] In the step (6), a coating layer can be formed by preparing
a coating liquid containing inorganic material particles obtained
by grinding raw ore or melting raw ore and a binder, applying the
coating liquid onto the surface of the ion exchange membrane
obtained in the step (5), and drying the coating liquid.
[2239] A preferable binder is a binder obtained by hydrolyzing a
fluorine-containing polymer having an ion exchange group precursor
with an aqueous solution containing dimethyl sulfoxide (DMSO) and
potassium hydroxide (KOH) and then immersing the polymer in
hydrochloric acid to replace the counter of the ion exchange group
by H+ (e.g., a fluorine-containing polymer having a carboxyl group
or sulfo group). Thereby, the polymer more likely to dissolve in
water or ethanol mentioned below, which is preferable.
[2240] This binder is dissolved in a mixed solution of water and
ethanol. The volume ratio between water and ethanol is preferably
10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to
1:2. The inorganic material particles are dispersed with a ball
mill into the dissolution liquid thus obtained to thereby provide a
coating liquid. In this case, it is also possible to adjust the
average particle size and the like of the particles by adjusting
the time and rotation speed during the dispersion. The preferable
amount of the inorganic material particles and the binder to be
blended is as mentioned above.
[2241] The concentration of the inorganic material particles and
the binder in the coating liquid is not particularly limited, but a
thin coating liquid is preferable. This enables uniform application
onto the surface of the ion exchange membrane.
[2242] Additionally, a surfactant may be added to the dispersion
when the inorganic material particles are dispersed. As the
surfactant, nonionic surfactants are preferable, and examples
thereof include HS-210, NS-210, P-210, and E-212 manufactured by
NOF CORPORATION.
[2243] The coating liquid obtained is applied onto the surface of
the ion exchange membrane by spray application or roll coating to
thereby provide an ion exchange membrane.
[Microporous Membrane]
[2244] The microporous membrane of the present embodiment is not
particularly limited as long as the membrane can be formed into a
laminate with the electrode for electrolysis, as mentioned above.
Various microporous membranes may be employed.
[2245] The porosity of the microporous membrane of the present
embodiment is not particularly limited, but can be 20 to 90, for
example, and is preferably 30 to 85. The above porosity can be
calculated by the following formula:
Porosity=(1-(the weight of the membrane in a dried state)/(the
weight calculated from the volume calculated from the thickness,
width, and length of the membrane and the density of the membrane
material)).times.100
[2246] The average pore size of the microporous membrane of the
present embodiment is not particularly limited, and can be 0.01
.mu.m to 10 .mu.m, for example, preferably 0.05 .mu.m to 5 .mu.m.
With respect to the average pore size, for example, the membrane is
cut vertically to the thickness direction, and the section is
observed with an FE-SEM. The average pore size can be obtained by
measuring the diameter of about 100 pores observed and averaging
the measurements.
[2247] The thickness of the microporous membrane of the present
embodiment is not particularly limited, and can be 10 .mu.m to 1000
.mu.m, for example, preferably 50 .mu.m to 600 .mu.m. The above
thickness can be measured by using a micrometer (manufactures by
Mitutoyo Corporation) or the like, for example.
[2248] Specific examples of the microporous membrane as mentioned
above include Zirfon Perl UTP 500 manufactured by Agfa and those
described in International Publication No. WO 2013-183584 and
International Publication No. WO 2016-203701.
[2249] In the method for producing an electrolyzer according to the
present embodiment, the membrane preferably comprises a first ion
exchange resin layer and a second ion exchange resin layer having
an EW (ion exchange capacity) different from that of the first ion
exchange resin layer. Additionally, the membrane preferably
comprises a first ion exchange resin layer and a second ion
exchange resin layer having a functional group different from that
of the first ion exchange resin layer. The ion exchange capacity
can be adjusted by the functional group to be introduced, and
functional groups that may be introduced are as mentioned
above.
(Water Electrolysis)
[2250] The electrolyzer in the present embodiment, as an
electrolyzer in the case of electrolyzing water, has a
configuration in which the ion exchange membrane in an electrolyzer
for use in the case of electrolyzing common salt mentioned above is
replaced by a microporous membrane. The raw material to be
supplied, which is water, is different from that for the
electrolyzer in the case of electrolyzing common salt mentioned
above. As for the other components, components similar to that of
the electrolyzer in the case of electrolyzing common salt can be
employed also in the electrolyzer in the case of electrolyzing
water. Since chlorine gas is generated in the anode chamber in the
case of common salt electrolysis, titanium is used as the material
of the anode chamber, but in the case of water electrolysis, only
oxygen gas is generated in the anode chamber. Thus, a material
identical to that of the cathode chamber can be used. An example
thereof is nickel. For anode coating, catalyst coating for oxygen
generation is suitable. Examples of the catalyst coating include
metals, oxides, and hydroxides of the platinum group metals and
transition metal group metals. For example, elements such as
platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron
can be used.
EXAMPLES
[2251] The present invention will be described in further detail
with reference to Examples and Comparative Examples below, but the
present invention is not limited to Examples below in any way.
<Verification of First Embodiment>
[2252] As will be described below, Experiment Examples according to
the first embodiment (in the section of <Verificaton of first
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the first embodiment in the
section of <Verification of first embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 10 to 21 as appropriate.
[Evaluation Method]
(1) Opening Ratio
[2253] An electrode was cut into a size of 130 mm.times.100 mm. A
digimatic thickness gauge (manufactured by Mitutoyo Corporation,
minimum scale 0.001 mm) was used to calculate an average value of
10 points obtained by measuring evenly in the plane. The value was
used as the thickness of the electrode (gauge thickness) to
calculate the volume. Thereafter, an electronic balance was used to
measure the mass. From the specific gravity of each metal (specific
gravity of nickel=8.908 g/cm.sup.3, specific gravity of
titanium=4.506 g/cm.sup.3) the opening ratio or void ratio was
calculated.
Opening ratio (Void ratio) (%)=(1-(electrode mass)/(electrode
volume.times.metal specific gravity)).times.100
(2) Mass per Unit Area (mg/cm.sup.2)
[2254] An electrode was cut into a size of 130 mm.times.100 mm, and
the mass thereof was measured by an electronic balance. The value
was divided by the area (130 mm.times.100 mm) to calculate the mass
per unit area.
(3) Force Applied per Unit MassUnit Area (1) (Adhesive Force)
(N/mgcm.sup.2))
[2255] [Method (i)]
[2256] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-6001
type load cell).
[2257] A 200 mm square nickel plate having a thickness of 1.2 mm
was subjected to blast processing with alumina of grain-size number
320. The arithmetic average surface roughness (Ra) of the nickel
plate after the blast treatment was 0.7 .mu.m. For surface
roughness measurement herein, a probe type surface roughness
measurement instrument SJ-310 (Mitutoyo Corporation) was used. A
measurement sample was placed on the surface plate parallel to the
ground surface to measure the arithmetic average roughness Ra under
measurement conditions as described below. The measurement was
repeated 6 times, and the average value was listed.
[2258] <Probe Shape> conical taper angle=60.degree., tip
radius=2 .mu.m, static measuring force=0.75 mN
[2259] <Roughness standard> JIS2001
[2260] <Evaluation curve> R
[2261] <Filter> GAUSS
[2262] <Cutoff value .lamda.c> 0.8 mm
[2263] <Cutoff value .lamda.s> 2.5 .mu.m
[2264] <Number of sections> 5
[2265] <Pre-running, post-running> available
[2266] This nickel plate was vertically fixed on the lower chuck of
the tensile and compression testing machine.
[2267] As the membrane, an ion exchange membrane A below was
used.
[2268] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTFE) were used (hereinafter
referred to as PTFE yarns). As sacrifice yarns, yarns obtained by
twisting six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
two sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[2269] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin B of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[2270] Using these resins A and B, a two-layer film in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[2271] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[2272] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour to replace the counterion of
the ion exchange group by Na, and then washed with water. Then, the
membrane was dried at 60.degree. C.
[2273] Further, 20% by mass of zirconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. The average particle size was measured by a
particle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[2274] The ion exchange membrane (membrane) obtained above was
immersed in pure water for 12 hours or more and then used for the
test. The membrane was brought into contact with the above nickel
plate sufficiently moistened with pure water and allowed to adhere
to the plate by the tension of water. At this time, the nickel
plate and the ion exchange membrane were placed so as to align the
upper ends thereof.
[2275] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped the upper chuck of the tensile
and compression testing machine to hang the electrode. The load
applied on the testing machine at this time was set to 0 N. The
integrated piece of the stainless plates, electrode, and clips was
once removed from the tensile and compression testing machine, and
immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[2276] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the ion exchange membrane
by the surface tension of pure water. The size of the adhesive
surface at this time was 130 mm in width and 110 mm in length. Pure
water in a wash bottle was sprayed to the electrode and the ion
exchange membrane entirely so as to sufficiently moisten the
membrane and the electrode again. Thereafter, a roller formed by
winding a closed-cell type EPDM sponge rubber having a thickness of
5 mm around a vinyl chloride pipe (outer diameter: 38 mm) was
rolled downward from above with lightly pressed over the electrode
to remove excess pure water. The roller was rolled only once.
[2277] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the overlapping
portion of the electrode and the membrane reached 130 mm in width
and 100 mm in length was recorded. This measurement was repeated
three times, and the average value was calculated.
[2278] This average value was divided by the area of the
overlapping portion of the electrode and the ion exchange membrane
and the mass of the electrode of the portion overlapping the ion
exchange membrane to calculate the force applied per unit massunit
area (1). The mass of the electrode of the portion overlapping the
ion exchange membrane was determined through proportional
calculation from the value obtained in (2) Mass per unit area
(mg/cm.sup.2) described above.
[2279] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity was
30.+-.5%.
[2280] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to the ion exchange membrane that
adhered to a vertically-fixed nickel plate via the surface
tension.
[2281] A schematic view of a method for evaluating the force
applied (1) is shown in FIG. 10.
[2282] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(4) Force Applied per Unit MassUnit Area (2) (Adhesive Force)
(N/mgcm.sup.2))
[2283] [Method (ii)]
[2284] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-6001
type load cell).
[2285] A nickel plate identical to that in Method (i) was
vertically fixed on the lower chuck of the tensile and compression
testing machine.
[2286] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped by the upper chuck of the
tensile and compression testing machine to hang the electrode. The
load applied on the testing machine at this time was set to 0 N.
The integrated piece of the stainless plates, electrode, and clips
was once removed from the tensile and compression testing machine,
and immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[2287] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the nickel plate via the
surface tension of a solution. The size of the adhesive surface at
this time was 130 mm in width and 110 mm in length. Pure water in a
wash bottle was sprayed to the electrode and the nickel plate
entirely so as to sufficiently moisten the nickel plate and the
electrode again. Thereafter, a roller formed by winding a
closed-cell type EPDM sponge rubber having a thickness of 5 mm
around a vinyl chloride pipe (outer diameter: 38 mm) was rolled
downward from above with lightly pressed over the electrode to
remove excess solution. The roller was rolled only once.
[2288] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the overlapping
portion of the electrode and the nickel plate in the longitudinal
direction reached 100 mm was recorded. This measurement was
repeated three times, and the average value was calculated.
[2289] This average value was divided by the area of the
overlapping portion of the electrode and the nickel plate and the
mass of the electrode of the portion overlapping the nickel plate
to calculate the force applied per unit massunit area (2). The mass
of the electrode of the portion overlapping the membrane was
determined through proportional calculation from the value obtained
in (2) mass per unit area (mg/cm.sup.2) described above.
[2290] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity was
30.+-.5%.
[2291] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to a vertically-fixed nickel plate via
the surface tension.
[2292] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(5) Method for Evaluating Winding Around Column of 280 mm in
Diameter (1) (%)
(Membrane and Column)
[2293] The evaluation method (1) was conducted by the following
procedure.
[2294] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In Comparative Examples 10 and 11, the electrode had been
integrated with the ion exchange membrane by thermal pressing, and
thus, an integrated piece of an ion exchange membrane and an
electrode was provided (electrode of a 130 mm square). After the
ion exchange membrane was sufficiently immersed in pure water, the
membrane was placed on the curved surface of a plastic
(polyethylene) pipe having an outer diameter of 280 mm. Thereafter,
excess solution was removed with a roller formed by winding a
closed-cell type EPDM sponge rubber having a thickness of 5 mm
around a vinyl chloride pipe (outer diameter: 38 mm). The roller
was rolled over the ion exchange membrane from the left to the
right of the schematic view shown in FIG. 11. The roller was rolled
only once. One minute after, the proportion of a portion at which
the ion exchange membrane was brought into a close contact with the
plastic pipe electrode having an outer diameter of 280 mm was
measured.
(6) Method for Evaluating Winding Around Column of 280 mm in
Diameter (2) (%)
(Membrane and Electrode)
[2295] The evaluation method (2) was conducted by the following
procedure.
[2296] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
130 mm square. The ion exchange membrane was immersed in pure water
for 12 hours or more and then used for the test. The ion exchange
membrane and the electrode were sufficiently immersed in pure water
and then laminated. This laminate was placed on the curved surface
of a plastic (polyethylene) pipe having an outer diameter of 280 mm
such that the electrode was located outside. Thereafter, a roller
formed by winding a closed-cell type EPDM sponge rubber having a
thickness of 5 mm around a vinyl chloride pipe (outer diameter: 38
mm) was rolled from the left to the right of the schematic view
shown in FIG. 12 with lightly pressed over the electrode to remove
excess solution. The roller was rolled only once. One minute after,
the proportion of a portion at which the ion exchange membrane was
brought into a close contact with the electrode was measured.
(7) Method for Evaluating Winding Around Column of 145 mm in
Diameter (3) (%)
(Membrane and Electrode)
[2297] The evaluation method (3) was conducted by the following
procedure.
[2298] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
130 mm square. The ion exchange membrane was immersed in pure water
for 12 hours or more and then used for the test. The ion exchange
membrane and the electrode were sufficiently immersed in pure water
and then laminated. This laminate was placed on the curved surface
of a plastic (polyethylene) pipe having an outer diameter of 145 mm
such that the electrode was located outside. Thereafter, a roller
formed by winding a closed-cell type EPDM sponge rubber having a
thickness of 5 mm around a vinyl chloride pipe (outer diameter: 38
mm) was rolled from the left to the right of the schematic view
shown in FIG. 13 with lightly pressed over the electrode to remove
excess solution. The roller was rolled only once. One minute after,
the proportion of a portion at which the ion exchange membrane was
brought into a close contact with the electrode was measured.
(8) Handling Property (Response Evaluation)
[2299] (A) The ion exchange membrane A (membrane) produced in
[Method (i)] was cut into a 170 mm square, and the electrode was
cut into a size of 95.times.110 mm. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In each Example, the ion exchange membrane and electrode were
sufficiently immersed in three solutions: sodium bicarbonate
aqueous solution, 0.1N NaOH aqueous solution, and pure water, then
laminated, and placed still on a Teflon plate. The interval between
the anode cell and the cathode cell used in the electrolytic
evaluation was set at about 3 cm. The laminate placed still was
lifted, and an operation of inserting and holding the laminate
therebetween was conducted. This operation was conducted while the
electrode was checked for dislocation and dropping.
[2300] (B) The ion exchange membrane A (membrane) produced in
[Method (i)] was cut into a 170 mm square, and the electrode was
cut into a size of 95.times.110 mm. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In each Example, the ion exchange membrane and electrode were
sufficiently immersed in three solutions: a sodium bicarbonate
aqueous solution, a 0.1N NaOH aqueous solution, and pure water,
then laminated, and placed still on a Teflon plate. The adjacent
two corners of the membrane portion of the laminate were held by
hands to lift the laminate so as to be vertical. The two corners
held by hands were moved from this state to be close to each other
such that the membrane was protruded or recessed. This move was
repeated again to check the conformability of the electrode to the
membrane. The results were evaluated on a four level scale of 1 to
4 on the basis of the following indices:
[2301] 1: good handling property
[2302] 2: capable of being handled
[2303] 3: difficult to handle
[2304] 4: substantially incapable of being handled
[2305] Here, the sample of Comparative Example 5, provided in a
size equivalent to that of a large electrolytic cell including an
electrode in a size of 1.3 m.times.2.5 m and an ion exchange
membrane in a size of 1.5 m.times.2.8 m, was subjected to handling.
The evaluation result of Comparative Example 5 ("3" as described
below) was used as an index to evaluate the difference between the
evaluation of the above (A) and (B) and that of the large-sized
one. That is, in the case where the evaluation result of a small
laminate was "1" or "2", it was judged that there was no problem in
the handling property even if the laminate was provided in a larger
size.
(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%),
Common Salt Concentration in Caustic Soda (ppm, on the Basis of
50%))
[2306] The electrolytic performance was evaluated by the following
electrolytic experiment.
[2307] A titanium anode cell having an anode chamber in which an
anode was provided (anode terminal cell) and a cathode cell having
a nickel cathode chamber in which a cathode was provided (cathode
terminal cell) were oppositely disposed. A pair of gaskets was
arranged between the cells, and a laminate (a laminate of the ion
exchange membrane A and an electrode for electrolysis) was
sandwiched between the gaskets. Then, the anode cell, the gasket,
the laminate, the gasket, and the cathode were brought into close
contact together to obtain an electrolytic cell, and an
electrolyzer including the cell was provided.
[2308] The anode was produced by applying a mixed solution of
ruthenium chloride, iridium chloride, and titanium tetrachloride
onto a titanium substrate subjected to blasting and acid etching
treatment as the pretreatment, followed by drying and baking. The
anode was fixed in the anode chamber welding. As the cathode, one
described in each of Examples and Comparative Examples was used. As
the collector of the cathode chamber, a nickel expanded metal was
used. The collector had a size of 95 mm in length.times.110 mm in
width. As a metal elastic body, a mattress formed by knitting
nickel fine wire was used. The mattress as the metal elastic body
was placed on the collector. Nickel mesh formed by plain-weaving
nickel wire having a diameter of 150 .mu.m in a sieve mesh size of
40 was placed thereover, and a string made of Teflon (R) was used
to fix the four corners of the Ni mesh to the collector. This Ni
mesh was used as a feed conductor. This electrolytic cell has a
zero-gap structure by use of the repulsive force of the mattress as
the metal elastic body. As the gaskets, ethylene propylene diene
(EPDM) rubber gaskets were used. As the membrane, the ion exchange
membrane A (160 mm square) produced in [Method (i)] was used.
[2309] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted so as to allow the temperature in each
electrolytic cell to reach 90.degree. C. Common salt electrolysis
was performed at a current density of kA/m.sup.2 to measure the
voltage, current density, and common salt concentration in caustic
soda. The current efficiency here is the proportion of the amount
of the produced caustic soda to the passed current, and when
impurity ions and hydroxide ions rather than sodium ions move
through the ion exchange membrane due to the passed current, the
current efficiency decreases. The current efficiency was obtained
by dividing the number of moles of caustic soda produced for a
certain time by the number of moles of the electrons of the current
passing during that time. The number of moles of caustic soda was
obtained by recovering caustic soda produced by the electrolysis in
a plastic container and measuring its mass. As the common salt
concentration in caustic soda, a value obtained by converting the
caustic soda concentration on the basis of 50% was shown.
[2310] The specification of the electrode and the feed conductor
used in each of Examples and Comparative Examples is shown in Table
1
(11) Measurement of Thickness of Catalytic Layer, Substrate for
Electrode for Electrolysis, and Thickness of Electrode
[2311] For the thickness of the substrate for electrode for
electrolysis, a digimatic thickness gauge (manufactured by Mitutoyo
Corporation, minimum scale 0.001 mm) was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane. The value was used as the thickness of the substrate for
electrode for electrolysis (gauge thickness). For the thickness of
the electrode, a digimatic thickness gauge was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane, in the same manner as for the substrate for electrode. The
value was used as the thickness of the electrode (gauge thickness).
The thickness of the catalytic layer was determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
(12) Elastic Deformation Test of Electrode
[2312] The ion exchange membrane A (membrane) and the electrode
produced in [Method (i)] were each cut into a 110 mm square. The
ion exchange membrane was immersed in pure water for 12 hours or
more and then used for the test. After the ion exchange membrane
and the electrode were laminated to produce a laminate under
conditions of a temperature: 23.+-.2.degree. C. and a relative
humidity: 30.+-.5%, the laminate was wound around a PVC pipe having
an outer diameter of .PHI.32 mm and a length of 20 cm without any
gap, as shown in FIG. 14. The laminate was fixed using a
polyethylene cable tie such that the laminate wound did not come
off from the PVC pipe or loosen. The laminate was retained in this
state for 6 hours. Thereafter, the cable tie was removed, and the
laminate was unwound from the PVC pipe. Only the electrode was
placed on a surface plate, and the heights L.sub.1 and L.sub.2 of a
portion lifted from the surface plate were measured to determine an
average value. This value was used as the index of the electrode
deformation. That is, a smaller value means that the laminate is
unlikely to deform.
[2313] When an expanded metal is used, there are two winding
direction: the SW direction and the LW direction. In this test, the
laminate was wound in the SW direction.
[2314] Deformed electrodes (electrodes that did not return to their
original flat state) were evaluated for softness after plastic
deformation in accordance with a method as shown in FIG. 15. That
is, a deformed electrode was placed on a membrane sufficiently
immersed in pure water. One end of the electrode was fixed, and the
other lifted end was pressed onto the membrane to release a force,
and an evaluation was performed whether the deformed electrode
conformed to the membrane.
(13) Membrane Damage Evaluation
[2315] As the membrane, an ion exchange membrane B below was
used.
[2316] As reinforcement core materials, those obtained by twisting
100 denier tape yarns of polytetrafluoroethylene (PTFE) 900 times/m
into a thread form were used. (hereinafter referred to as PTFE
yarns). As warp sacrifice yarns, yarns obtained by twisting eight
35 denier filaments of polyethylene terephthalate (PET) 200 times/m
were used (hereinafter referred to as PET yarns). As weft sacrifice
yarns, yarns obtained by twisting eight 35 denier filaments of
polyethylene terephthalate (PET) 200 times/m were used. First, the
PTFE yarns and the sacrifice yarns were plain-woven with 24 PTFE
yarns/inch so that two sacrifice yarns were arranged between
adjacent PTFE yarns, to obtain a woven fabric having a thickness of
100 .mu.m.
[2317] Next, a polymer (A1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.92 mg equivalent/g and a
polymer (B1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g were provided.
Using these polymers (A1) and (B1), a two-layer film X in which the
thickness of a polymer (A1) layer was 25 .mu.m and the thickness of
a polymer (E1) layer was 89 .mu.m was obtained by a coextrusion T
die method. As the ion exchange capacity of each polymer, shown was
the ion exchange capacity in the case of hydrolyzing the ion
exchange group precursors of each polymer for conversion into ion
exchange groups.
[2318] Separately, a polymer (B2) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g was provided.
This polymer was single-layer extruded to obtain a film Y having a
thickness of 20 .mu.m.
[2319] Subsequently, release paper, the film Y, a reinforcing
material, and the film X were laminated in this order on a hot
plate having a heat source and a vacuum source inside and having
micropores on its surface, heated and depressurized under the
conditions of a hot plate temperature of 225.degree. C. and a
degree of reduced pressure of 0.022 MPa for two minutes, and then
the release paper was removed to obtain a composite membrane. The
resulting composite membrane was immersed in an aqueous solution
comprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH)
for an hour for saponification. Thereafter, the membrane was
immersed in 0.5N NaOH for an hour to replace the ions attached to
the ion exchange groups by Na, and then washed with water. Further,
the membrane was dried at 60.degree. C.
[2320] Additionally, a polymer (B3) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.05 mg equivalent/g were
hydrolyzed and then was turned into an acid type with hydrochloric
acid. Zirconium oxide particles having an average particle size of
primary particles of 0.02 .mu.m were added to a 50/50 (mass ratio)
mixed solution of water and ethanol in which the polymer (B3') of
this acid type was dissolved in a proportion of 5% by mass such
that the mass ratio of the polymer (B3') to the zirconium oxide
particles was 20/80. Thereafter, the polymer (B3') was dispersed in
a suspension of the zirconium oxide particles with a ball mill to
obtain a suspension.
[2321] This suspension was applied by a spray method onto both the
surfaces of the ion exchange membrane and dried to obtain an ion
exchange membrane B having a coating layer containing the polymer
(B3') and the zirconium oxide particles. The coating density of
zirconium oxide measured by fluorescent X-ray measurement was 0.35
mg/cm.sup.2.
[2322] The anode used was the same as in (9) Electrolytic
evaluation.
[2323] The cathode used was one described in each of Examples and
Comparative Examples. The collector, mattress, and feed conductor
of the cathode chamber used were the same as in (9) Electrolytic
evaluation. That is, a zero-gap structure had been provided by use
of Ni mesh as the feed conductor and the repulsive force of the
mattress as the metal elastic body. The gaskets used were the same
as in (9) Electrolytic evaluation. As the membrane, the ion
exchange membrane B produced by the method mentioned above was
used. That is, an electrolyzer equivalent to that in (9) was
provided except that the laminate of the on exchange membrane B and
the electrode for electrolysis was sandwiched between a pair of
gaskets.
[2324] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted such that the temperature in each
electrolytic cell reached 70.degree. C. Common salt electrolysis
was performed at a current density of 8 kA/m.sup.2. The
electrolysis was stopped 12 hours after the start of the
electrolysis, and the ion exchange membrane B was removed and
observed for its damage condition.
[2325] "0" means no damage. "1 to 3" means that damage was present,
and a larger number means a larger degree of damage.
(14) Ventilation Resistance of Electrode
[2326] The ventilation resistance of the electrode was measured
using an air permeability tester KES-F8 (trade name, KATO TECH CO.,
LTD.). The unit for the ventilation resistance value is kPas/m. The
measurement was repeated 5 times, and the average value was listed
in Table 2. The measurement was conducted under the following two
conditions. The temperature of the measuring chamber was 24.degree.
C. and the relative humidity was
Measurement Condition 1 (Ventilation Resistance 1)
[2327] Piston speed: 0.2 cm/s
[2328] Ventilation volume: 0.4 cc/cm.sup.2/s
[2329] Measurement range: SENSE L (low)
[2330] Sample size: 50 mm.times.50 mm
Measurement Condition 2 (Ventilation Resistance 2)
[2331] Piston speed: 2 cm/s
[2332] Ventilation volume: 4 cc/cm.sup.2/s
[2333] Measurement range: SENSE M (medium) or H (high)
[2334] Sample size: 50 mm.times.50 mm
Example 1
[2335] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 16 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.71
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[2336] A porous foil was formed by perforating this nickel foil
with circular holes by punching. The opening ratio was 49%.
[2337] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[2338] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced in Example 1 was 24 .mu.m.
The thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode, was 8 .mu.m. The
coating was formed also on the surface not roughened. The thickness
was the total thickness of ruthenium oxide and cerium oxide.
[2339] The measurement results of the adhesive force of the
electrode produced by the above method are shown in Table 2. A
sufficient adhesive force was observed.
[2340] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2341] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
[2342] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The roughened surface of the electrode was oppositely
disposed on a substantial center position of the carboxylic acid
layer side of the ion exchange membrane A (size: 160 mm.times.160
mm), produced in [Method (i)] and equilibrated with a 0.1 N NaOH
aqueous solution, and allowed to adhere thereto via the surface
tension of the aqueous solution.
[2343] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did not come
off or was not displaced.
[2344] The above membrane-integrated electrode was sandwiched
between the anode cell and the cathode cell such that the surface
onto which the electrode was attached was allowed to face the
cathode chamber side. In the sectional structure, the collector,
the mattress, the nickel mesh feed conductor, the electrode, the
membrane, and the anode are arranged in the order mentioned from
the cathode chamber side to form a zero-gap structure.
[2345] The resulting electrode was subjected to electrolytic
evaluation. The results are shown in Table 2.
[2346] The electrode exhibited a low voltage, high current
efficiency, and a low common salt concentration in caustic soda.
The handling property was also good: "1". The membrane damage was
also evaluated as good: "0".
[2347] When the amount of coating after the electrolysis was
measured by fluorescent X-ray analysis (XRF), substantially 100% of
the coating remained on the roughened surface, and the coating on
the surface not roughened was reduced. This indicates that the
surface opposed to the membrane (roughened surface) contributes to
the electrolysis and the other surface not opposed to the membrane
can achieve satisfactory electrolytic performance when the amount
of coating is small or no coating is present.
Example 2
[2348] In Example 2, an electrolytic nickel foil having a gauge
thickness of 22 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
0.96 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2349] The thickness of the electrode was 29 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 7 .mu.m. The coating was formed
also on the surface not roughened.
[2350] A sufficient adhesive force was observed.
[2351] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2352] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0033 (kPas/m) under the
measurement condition 2.
[2353] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was also evaluated as good: "0".
[2354] When the amount of coating after the electrolysis was
measured by XRE, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 3
[2355] In Example 3, an electrolytic nickel foil having a gauge
thickness of 30 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
1.38 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2356] The thickness of the electrode was 38 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m. The coating was formed
also on the surface not roughened.
[2357] A sufficient adhesive force was observed.
[2358] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2359] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[2360] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2361] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating present.
Example 4
[2362] In Example 4, an electrolytic nickel foil having a gauge
thickness of 16 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to a roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
0.71 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 75%. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2363] The thickness of the electrode was 24 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2364] A sufficient adhesive force was observed.
[2365] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2366] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[2367] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2368] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 5
[2369] In Example 5, an electrolytic nickel foil having a gauge
thickness of 20 .mu.m was provided as the substrate for electrode
for cathode electrolysis. Both the surface of this nickel foil was
subjected to a roughening treatment by means of electrolytic nickel
plating. The arithmetic average roughness Ra of the roughened
surface was 0.96 .mu.m. Both the surfaces had the same roughness.
The measurement of the surface roughness was performed under the
same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. The opening ratio
was 49%. Except for the above described, evaluation was performed
in the same manner as in Example 1, and the results are shown in
Table 2.
[2370] The thickness of the electrode was 30 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m. The coating was formed
also on the surface not roughened.
[2371] A sufficient adhesive force was observed.
[2372] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2373] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[2374] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2375] Additionally, when the amount of coating after the
electrolysis was measured by XRF, substantially 100% of the coating
remained on both the surfaces. In consideration of comparison with
Examples 1 to 4, this indicates that the other surface not opposed
to the membrane can achieve satisfactory electrolytic performance
when the amount of coating is small or no coating is present.
Example 6
[2376] In Example 6, evaluation was performed in the same manner as
in Example 1 except that coating of the substrate for electrode for
cathode electrolysis was performed by ion plating, and the results
are shown in Table 2. In the ion plating, film forming was
performed using Ru metal target at the heating temperature of
200.degree. C. and under an argon/oxygen atmosphere at a film
forming pressure of 7.times.10.sup.-2 Pa. The coating formed was
ruthenium oxide.
[2377] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode was 10 .mu.m.
[2378] A sufficient adhesive force was observed.
[2379] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2380] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPAs/m) under the
measurement condition 2.
[2381] Additionally, the electrode exhibited a low voltage, high
current efficiency and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 7
[2382] In Example 7, the substrate for electrode for cathode
electrolysis was produced by an electroforming method. The
photomask had a shape formed by vertically and horizontally
arranging 0.485 mm.times.0.485 mm squares at an interval of 0.15
mm. Exposure, development, and electroplating were sequentially
performed to obtain a nickel porous foil having a gauge thickness
of 20 .mu.m and an opening ratio of 56%. The arithmetic average
roughness Ra of the surface was 0.71 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2383] The thickness of the electrode was 37 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 17 .mu.m.
[2384] A sufficient adhesive force was observed.
[2385] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2386] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[2387] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 8
[2388] In Example 8, the substrate for electrode for cathode
electrolysis was produced by an electroforming method. The
substrate had a gauge thickness of 50 .mu.m and an opening ratio of
56%. The arithmetic average roughness Ra of the surface was 0.73
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 1, and the results are shown in Table 2.
[2389] The thickness of the electrode was 60 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2390] A sufficient adhesive force was observed.
[2391] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2392] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[2393] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 9
[2394] In Example 9, a nickel nonwoven fabric having a gauge
thickness of 150 .mu.m and a void ratio of 76% (manufactured by
NIKKO TECHNO, Ltd.) was used as the substrate for electrode for
cathode electrolysis. The nonwoven fabric had a nickel fiber
diameter of about 40 .mu.m and a basis weight of 300 g/m.sup.2.
Except for the above described, evaluation was performed in the
same manner as in Example 1, and the results are shown in Table
2.
[2395] The thickness of the electrode was 165 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 15 .mu.m.
[2396] A sufficient adhesive force was observed.
[2397] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 29 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[2398] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0612 (kPas/m) under the
measurement condition 2.
[2399] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 10
[2400] In Example 10, a nickel nonwoven fabric having a gauge
thickness of 200 .mu.m and a void ratio of 72% (manufactured by
NIKKO TECHNO, Ltd.) was used as the substrate for electrode for
cathode electrolysis. The nonwoven fabric had a nickel fiber
diameter of about 40 .mu.m and a basis weight of 500 g/m.sup.2.
Except for the above described, evaluation was performed in the
same manner as in Example 1, and the results are shown in Table
2.
[2401] The thickness of the electrode was 215 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 15 .mu.m.
[2402] A sufficient adhesive force was observed.
[2403] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 40 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electro had a satisfactory handling property.
[2404] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0164 (kPas/m) under the
measurement condition 2.
[2405] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 11
[2406] In Example 11, foamed nickel having a gauge thickness of 200
.mu.m and a void ratio of 72% (manufactured by Mitsubishi Materials
Corporation) was used as the substrate for electrode for cathode
electrolysis. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2407] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2408] A sufficient adhesive force was observed.
[2409] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 17 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[2410] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0402 (kPas/m) under the
measurement condition 2.
[2411] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 12
[2412] In Example 12, a 200-mesh nickel mesh having a line diameter
of 50 82 m, a gauge thickness of 100 .mu.m, and an opening ratio of
37% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The blast treatment did not change the
opening ratio. It is difficult to measure the roughness of the
surface of the wire mesh. Thus, in Example 12, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness or the wire
mesh. The arithmetic average roughness Ra of a wire piece of the
wire mesh was 0.64 .mu.m. The measurement of the surface roughness
was performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation was performed
in the same manner as in Example 1, and the results are shown in
Table 2.
[2413] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2414] A sufficient adhesive force was observed.
[2415] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2416] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0154 (kPas/m) under the
measurement condition 2.
[2417] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was evaluated as good: "0".
Example 13
[2418] In Example 13, a 150-mesh nickel mesh having a line diameter
of 65 .mu.m, a gauge thickness of 130 .mu.m, and an opening ratio
of 38% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The blast treatment did not change the
opening ratio. It is difficult to measure the roughness of the
surface of the wire mesh. Thus, in Example 13, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.66 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, the above evaluation was performed in the same manner as
in Example 1, and the results are shown in Table 2.
[2419] The thickness of the electrode was 133 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 3 .mu.m.
[2420] A sufficient adhesive force was observed.
[2421] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 6.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2422] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0124 (kPas/m) under the
measurement condition 2.
[2423] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was also evaluated as good: "0".
Example 14
[2424] In Example 14, a substrate identical to that of Example 3
(gauge thickness of 30 .mu.m and opening ratio or 44%) was used as
the substrate for electrode for cathode electrolysis. Electrolytic
evaluation as performed with a structure identical to that of
Example 1 except that no nickel mesh feed conductor was included.
That is, in the sectional structure of the cell, the collector, the
mattress, the membrane-integrated electrode, and the anode are
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure, and the mattress serves as the feed
conductor. Except for the above described, evaluation was performed
in the same manner as in Example 1, and the results are shown in
Table 2.
[2425] A sufficient adhesive force was observed.
[2426] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2427] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[2428] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 15
[2429] In Example 15, a substrate identical to that of Example 3
(gauge thickness of 30 .mu.m and opening ratio of 44%) was used as
the substrate for electrode for cathode electrolysis. The cathode
used in Reference Example 1, which was degraded and had an enhanced
electrolytic voltage, was placed instead of the nickel mesh feed
conductor. Except for the above described, electrolytic evaluation
was performed with a structure identical to that of Example 1. That
is, in the sectional structure of the cell, the collector, the
mattress, the cathode that was degraded and had an enhanced
electrolytic voltage (serves as the feed conductor), the electrode
for electrolysis (cathode), the membrane, and the anode are
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure, and the cathode that is degraded and has
an enhanced electrolytic voltage serves as the feed conductor.
Except for the above described, evaluation was performed in the
same manner as in Example 1, and the results are shown in Table
2.
[2430] A sufficient adhesive force was observed.
[2431] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2432] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[2433] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 16
[2434] A titanium foil having a gauge thickness of 20 .mu.m was
provided as the substrate for electrode for anode electrolysis.
Both the surfaces of the titanium foil were subjected to a
roughening treatment. A porous foil was formed by perforating this
titanium foil with circular holes by punching. The hole diameter
was 1 mm, and the opening ratio was 14%. The arithmetic average
roughness Ra of the surface was 0.37 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment.
[2435] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[2436] A vat containing, the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a chloride
(PVC) cylinder was always in contact with the coating liquid. A
coating roll around which the same EPOM had been wound was placed
at the upper portion thereof, and PVC roller was further placed
thereabove. The coating liquid was applied by allowing the
substrate for electrode to pass between the second coating roll and
the PVC roller at the uppermost portion (roll coating method).
After the above coating liquid was applied onto the titanium porous
foil, drying at 60.degree. C. for 10 minutes and baking at
475.degree. C. for 10 minutes were performed. A series of these
coating, drying, preliminary baking, and baking operations was
repeatedly performed, and then baking at 520.degree. C. was
performed for an hour.
[2437] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The cut electrode was allowed to adhere via the surface
tension of the aqueous solution to a substantial center position of
the sulfonic acid layer side of the ion exchange membrane A (size:
160 mm.times.160 mm) produced in [Method (i)] and equilibrated with
a 0.1 N NaOH aqueous solution.
[2438] The cathode was prepared in the following procedure. First,
a 40-mesh nickel wire mesh having a line diameter of 150 .mu.m was
provided as the substrate. After blasted with alumina as
pretreatment, the wire mesh was immersed in 6 N hydrochloric acid
for 5 minutes, sufficiently washed with pure water, and dried.
[2439] Next, a ruthenium chloride solution having a ruthenium
concentration of 100 g/L (Tanaka Kiknzoku Kogyo K.K.) and cerium
chloride (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the
molar ratio between the ruthenium element and the cerium element
was 1:0.25. This mixed solution was sufficiently stirred and used
as a cathode coating liquid.
[2440] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at. 300.degree. C. for 3 minutes, and
baking at 550.degree. C. for 10 minutes were performed. Thereafter,
baking at 550.degree. C. for an hour was performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated.
[2441] As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. The cathode
produced by the above method was placed thereover, and a string
made of Teflon (R) was used to fix the four corners of the mesh to
the collector.
[2442] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the anodes, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did not come
off or was not displaced.
[2443] The anode used in Reference Example 3, which was degraded
and had an enhanced electrolytic voltage, was fixed to the anode
cell by welding, and the above membrane-integrated electrode was
sandwiched between the anode cell and the cathode cell such that
the surface onto which the electrode was attached was allowed to
face the anode chamber side. That is, in the sectional structure of
the cell, the collector, the mattress, the cathode, the membrane,
the electrode for electrolysis (titanium porous foil anode), and
the anode that was degraded and had an enhanced electrolytic
voltage were arranged in the order mentioned from the cathode
chamber side to form a zero-gap structure. The anode that was
degraded and had an enhanced electrolytic voltage served as the
feed conductor. The titanium porous foil anode and the anode that
was degraded and had an enhanced electrolytic voltage were only in
physical contact with each other and were not fixed with each other
by welding.
[2444] Evaluation on this structure was performed in the same
manner as in Example 1, and the results are shown in Table 2.
[2445] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 6 .mu.m.
[2446] A sufficient adhesive force was observed.
[2447] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 4 mm. It was found that
the electrode had a broad elastic deformation region.
[2448] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and, 0.0060 (kPas/m) under the
measurement condition 2.
[2449] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 17
[2450] In Example 17, a titanium foil having a gauge thickness of
20 .mu.m and an opening ratio of 30% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.37 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 16, and the results are
shown in Table 2.
[2451] The thickness of the electrode was 30 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2452] A sufficient adhesive force was observed.
[2453] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 5 mm. It was found that
the electrode had a broad elastic deformation region.
[2454] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
[2455] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 18
[2456] In Example 18, a titanium foil having a gauge thickness of
20 .mu.m and an opening ratio of 42% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.38 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 16, and the results are
shown in Table 2.
[2457] The thickness of the electrode was 32 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 12 .mu.m.
[2458] A sufficient adhesive force was observed.
[2459] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2460] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0022 (kPas/m) under the
measurement condition 2.
[2461] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 19
[2462] In Example 19, a titanium foil having a gauge thickness of
50 .mu.m and an opening ratio of 47% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.40 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 16, and the results are
shown in Table 2.
[2463] The thickness of the electrode was 69 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 19 .mu.m.
[2464] A sufficient adhesive force was observed.
[2465] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 8 mm. It was found that
the electrode had a broad elastic deformation region.
[2466] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0024 (kPas/m) under the
measurement condition 2.
[2467] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 20
[2468] In Example 20, a titanium nonwoven fabric having a gauge
thickness of 100 .mu.m, a titanium fiber diameter of about 20
.mu.m, a basis weight of 100 g/m.sup.2, and an opening ratio of 78%
was used as the substrate for electrode for anode electrolysis.
Except for the above described, evaluation was performed in the
same manner as in Example 16, and the results are shown in Table
2.
[2469] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[2470] A sufficient adhesive force was observed.
[2471] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2 mm. It was found that
the electrode had a broad elastic deformation region.
[2472] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0228 (kPas/m) under the
measurement condition 2.
[2473] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 21
[2474] In Example 21, a 150-mesh titanium wire mesh having a gauge
thickness of 120 .mu.m and a titanium fiber diameter of about 60
.mu.m was used as the substrate for electrode for anode
electrolysis. The opening ratio was 42%. A blast treatment was
performed with alumina of grain-size number 320. It is difficult to
measure the roughness of the surface of the wire mesh. Thus, in
Example 21, a titanium plate having a thickness of 1 mm was
simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the titanium plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.60 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as Example 16, and the results are
shown in Table 2.
[2475] The thickness of the electrode was 140 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 20 .mu.m.
[2476] A sufficient adhesive force was observed.
[2477] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 10 mm. It was found that
the electrode had a broad elastic deformation region.
[2478] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0132 (kPas/m) under the
measurement condition 2.
[2479] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 22
[2480] In Example 22, an anode that was degraded and had an
enhanced electrolytic voltage was used in the same manner as in
Example 16 as the anode feed conductor, and a titanium nonwoven
fabric to that of Example 20 was used as the anode. A cathode that
was degraded and had an enhanced electrolytic voltage was used in
the same manner as in Example 15 as the cathode feed conductor, and
a nickel foil electrode identical to that of Example 3 was used as
the cathode. In the sectional structure of the cell, the collector,
the mattress, the cathode that was degraded and had an enhanced
voltage, the nickel porous foil cathode, the membrane, the titanium
nonwoven fabric anode, and the anode that was degraded and had an
enhanced electrolytic voltage are arranged in the order mentioned
from the cathode chamber side to form a zero-gap structure, and the
cathode and anode degraded and having an enhanced electrolytic
voltage serve as the feed conductor. Except for the above
described, evaluation was performed in the same manner as in
Example 1, and the results are shown in Table 2.
[2481] The thickness of the electrode (anode) was 114 .mu.m, and
the thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness or the electrode (anode), was 14
.mu.m. The thickness of the electrode (cathode) was 38 .mu.m, and
the thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode (cathode), was 8
.mu.m.
[2482] A sufficient adhesive force was observed both in the anode
and the cathode.
[2483] When a deformation test of the electrode (anode) was
performed, the average value of L.sub.1 and L.sub.2 was 2 mm. When
a deformation test of the electrode (cathode) was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm.
[2484] When the ventilation resistance of the electrode (anode) was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0228 (kPas/m) under the
measurement condition 2. When the ventilation resistance of the
electrode (cathode) was measured, the ventilation resistance was
0.07 (kPas/m) or less under the measurement condition 1 and 0.0027
(kPas/m) under the measurement condition 2.
[2485] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0" both in the anode and the cathode.
In Example 22, the cathode and the anodes were combined by
attaching the cathode to one surface of the membrane and the anode
to the other surface and subjected to the membrane damage
evaluation.
Example 23
[2486] In Example 23, a microporous membrane "Zirfon Perl UTP 500"
manufactured by Agfa was used.
[2487] The Zirfon membrane was immersed in pure water for 12 hours
or more and used for the test. Except for the above described, the
above evaluation was performed in the same manner as in Example 3,
and the results are shown in Table 2.
[2488] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2489] Similarly to the case where an ion exchange membrane was
used as the membrane, a sufficient adhesive force was observed. The
microporous membrane was brought into a close contact with the
electrode via the surface tension, and the handling property was
good: "1".
Example 24
[2490] A carbon cloth obtained by weaving a carbon fiber having a
gauge thickness of 566 .mu.m was provided as the substrate for
electrode for cathode electrolysis. A coating liquid for use in
forming an electrode catalyst on this carbon cloth was prepared by
the following procedure. A ruthenium nitrate solution having a
ruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and
cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that
the molar ratio between the ruthenium element and the cerium
element was 1:0.25. This mixed solution was sufficiently stirred
and used as a cathode coating liquid.
[2491] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088 (trade name), thickness 10 mm)) around a
polyvinyl chloride (PVC) cylinder was always in contact with the
above coating liquid. A coating roll around which the same EPDM had
been wound was placed at the upper portion thereof, and a PVC
roller was further placed thereabove. The coating liquid was
applied by allowing the substrate for electrode to pass between the
second coating roll and the PVC roller at the uppermost portion
(roll coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced was 570 .mu.m. The
thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode, was 4 .mu.m. The
thickness of the catalytic layer was the total thickness of
ruthenium oxide and cerium oxide.
[2492] The resulting electrode was subjected to electrolytic
evaluation. The results are shown in Table 2.
[2493] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm.
[2494] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.19 (kPas/m) under the
measurement condition 1 and 0.176 (kPas/m) under the measurement
condition 2.
[2495] The electrode had a handling property of "2" and was
determined to be handleable as a large laminate.
[2496] The voltage was high, the membrane damage was evaluated as
"1", and membrane damage was observed. It was conceived that this
is because NaOH that had been generated in the electrode
accumulated on the interface between the electrode and the membrane
to elevate the concentration thereof, due to the high ventilation
resistance of the electrode of Example 24.
Reference Example 1
[2497] In Reference Example 1, used was a cathode used as the
cathode in a large electrolyzer for eight years, degraded, and
having an enhanced electrolytic voltage. The above cathode was
placed instead of the nickel mesh feed conductor on the mattress of
the cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In Reference Example 1, no
membrane-integrated electrode was used. In the sectional structure
of the cell, the collector, the mattress, the cathode that was
degraded and had an enhanced electrolytic voltage, the ion exchange
membrane A, and the anodes were arranged in the order mentioned
from the cathode chamber side to form a zero-gap structure.
[2498] As a result of the electrolytic evaluation with this
structure, the voltage was 3.04 V, the current efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 20 ppm. Consequently, due to
degradation of the cathode, the voltage was high.
Reference Example 2
[2499] In Reference Example 2, a nickel mesh feed conductor was
used as the cathode. That is, electrolysis was performed on nickel
mesh having no catalyst coating thereon.
[2500] The nickel mesh cathode was placed on the mattress of the
cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In the sectional structure of the
electric cell of Reference Example 2, the collector, the mattress,
the nickel mesh, the ion exchange membrane A, and the anodes were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[2501] As a result of the electrolytic evaluation with this
structure, the voltage was 3.38 V, the current efficiency was
97.7%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was ppm. Consequently, the voltage
was nigh because the cathode catalyst had no coating.
Reference Example 3
[2502] In Reference Example 3, used was an anode used as the anode
in a large electrolyzer for about eight years, degraded, and having
an enhanced electrolytic voltage.
[2503] In the sectional structure of the electrolytic cell of
Reference Example 3, the collector, the mattress, the cathode, the
ion exchange membrane A produced in [Method (i)], and the anode
that was degraded and had an enhanced electrolytic voltage were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[2504] As a result of the electrolytic evaluation with this
structure, the voltage was 3.18 V, the current efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 22 ppm. Consequently, due to
degredation of the anode, the voltage was high.
Comparative Example 1
[2505] In Comparative Example 1, a fully-rolled nickel expanded
metal having a gauge thickness of 100 .mu.m and an opening ratio of
33% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The opening ratio was not changed after the
blast treatment. It is difficult to measure the surface roughness
of the expanded metal. Thus, in Comparative Example 1, a nickel
plate having a thickness of 1 mm was simultaneously subjected to
the blast treatment during the blasting, and the surface roughness
of the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.68 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 1, and the results are shown in Table 2.
[2506] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[2507] The mass per unit area was 67.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.05
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was 64%, and the result of
evaluation of winding around column of 145 mm in diameter (3) was
22%. The portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[2508] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[2509] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Comparative Example 2
[2510] In Comparative Example 2, a fully-rolled nickel expanded
metal having a gauge thickness of 100 .mu.m and an opening ratio of
16% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The opening ratio was not changed after the
blast treatment. It is difficult to measure the surface roughness
of the expanded metal. Thus, in Comparative Example 2, a nickel
plate having a thickness of 1 mm was simultaneously subjected to
the blast treatment during the blasting, and the surface roughness
of the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.64 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 1, and the results are shown in Table 2.
[2511] The thickness of the electrode was 107 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 7 .mu.m.
[2512] The mass per unit area was 78.1 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.04
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was 37%, and the result of
evaluation of winding around column of 145 mm in diameter (3) was
25%. The portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[2513] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 18.5 mm.
[2514] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0176 (kPas/m) under the
measurement condition 2.
Comparative Example 3
[2515] In Comparative Example 3, a fully-rolled nickel expanded
metal having a gauge thickness of 100 .mu.m and an opening ratio of
40% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The opening ratio was not changed after the
blast treatment. It is difficult to measure the surface roughness
of the expanded metal. Thus, in Comparative Example 3, a nickel
plate having a thickness of 1 mm was simultaneously subjected to
the blast treatment during the blasting, and the surface roughness
of the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.70 .mu.m. The
measurement of the surface roughness m performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment.
[2516] Coating of the substrate for electrode for electrolysis was
performed by ion plating in the same manner as in Example 6. Except
for the above described, evaluation was performed in the same
manner as in Example 1, and the results are shown in Table 2.
[2517] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2518] The force applied per unit massunit area (1) was such a
small value as 0.07 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter (2) was 80%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 32%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[2519] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11 mm.
[2520] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
Comparative Example 4
[2521] In Comparative Example 4, a fully-rolled nickel expanded
metal having a gauge thickness of 100 .mu.m and an opening ratio of
58% was used as the substrate for electrode for cathode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The opening ratio was not changed after the
blast treatment. It is difficult to measure the surface roughness
of the expanded metal. Thus, in Comparative Example 4, a nickel
plate having a thickness of 1 mm was simultaneously subjected to
the blast treatment during the blasting, and the surface roughness
of the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.64 .mu.m. The
measurement Of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 1, and the results are shown in Table 2.
[2522] The thickness of the electrode was 109 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 9 .mu.m.
[2523] The force applied per unit massunit area (1) was such a
small value as 0.06 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter (2) was 69%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 39%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[2524] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11.5 mm.
[2525] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
Comparative Example 5
[2526] In Comparative Example 5, a nickel wire mesh having gauge
thickness of 300 .mu.m and an opening ratio of 56% was used as the
substrate for electrode for cathode electrolysis. It is difficult
to measure the surface roughness of the wire mesh. Thus, in
Comparative Example 5, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the last treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire A blast treatment was
performed with alumina of grain-size number 320. The opening ratio
was not changed after the blast treatment. The arithmetic average
roughness Ra was 0.64 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 1, and the results are
shown in Table 2.
[2527] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2528] The mass per unit area was 49.2 (mg/cm.sup.2). Thus, the
result of evaluation of winding around column of 280 mm in diameter
was 88%, and the result of evaluation of winding around column of
145 mm in diameter (3) was 42%. The portions at which the electrode
came off from the membrane increased. This is because the electrode
was likely to come off when the membrane-integrated electrode is
handled and the electrode may come off and fall from the membrane
during handled. There was a problem in the handling property, which
was evaluated as "3". When the large size electrode was actually
operated, it was possible to evaluate the handling property as "3".
The membrane damage was evaluated as "0".
[2529] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[2530] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
Comparative Example 6
[2531] In Comparative Example 6, a nickel wire mesh having a gauge
thickness of 200 .mu.m and an opening ratio of 37% was used as the
substrate for electrode for cathode electrolysis. A blast treatment
was performed with alumina of grain-size number 320. The opening
ratio was not changed after the blast treatment. It is difficult to
measure the surface roughness of the wire mesh. Thus, in
Comparative Example 6, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.65 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation of
electrode electrolysis, measurement results of the adhesive force,
and adhesiveness were performed in the same manner as in Example 1.
The results are shown in Table 2.
[2532] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2533] The mass per unit area was 56.4 mg/cm.sup.2. Thus, the
result of evaluation method of winding around column of 145 mm in
diameter (3) was 63%, and the adhesiveness between the electrode
and the membrane was poor. This is because the electrode was likely
to come off when the membrane-integrated electrode is handled and
the electrode may come off and fall from the membrane during
handled. There was a problem in the handling property, which was
evaluated as "3". The membrane damage was evaluated as "0".
[2534] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 19 mm.
[2535] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0096 (kPas/m) under the
measurement condition 2.
Comparative Example 7
[2536] In Comparative Example 7, a full-rolled titanium expanded
metal having a gauge thickness of 500 .mu.m and an opening ratio of
17% was used as the substrate for electrode for anode electrolysis.
A blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Comparative Example 7, a titanium plate having a
thickness of 1 mm was simultaneously subjected to the blast
treatment during the blasting, and the surface roughness of the
titanium plate was taken as the surface roughness of the wire mesh.
The arithmetic average roughness Ra was 0.60 .mu.m. The measurement
of the surface roughness was performed under the same conditions as
for the surface roughness measurement of the nickel plate subjected
to the blast treatment. Except for the above described, evaluation
was performed in the same manner as in Example 16, and the results
are shown in Table 2.
[2537] The thickness of the electrode was 508 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2538] The mass per unit area was 152.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2539] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2540] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition and 0.0072 (kPas/m) under the
measurement condition 2.
Comparative Example 8
[2541] In Comparative Example 8, a full-rolled titanium expanded
metal having a gauge thickness of 800 .mu.m and an opening ratio of
8% was used as the substrate for electrode for anode electrolysis.
A blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Comparative Example 8, a titanium plate having a
thickness of 1 mm was simultaneously subjected to the blast
treatment during the blasting, and the surface roughness of the
titanium plate was taken as the surface roughness of the wire mesh.
The arithmetic average roughness Ra was 0.61 .mu.m. The measurement
of the surface roughness was performed under the same conditions as
for the surface roughness measurement of the nickel plate subjected
to the blast treatment. Except for the above described, the above
evaluation was performed in the same manner as in Example 16, and
the results are shown in Table 2.
[2542] The thickness of the electrode was 808 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2543] The mass per unit area was 251.3 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2544] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2545] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0172 (kPas/m) under the
measurement condition 2.
Comparative Example 9
[2546] In Comparative Example 9, a full-rolled titanium expanded
metal having a gauge thickness of 1000 .mu.m and an opening ratio
of 46% was used as the substrate for electrode for anode
electrolysis. A blast treatment was performed with alumina of
grain-size number 320. The opening ratio was not changed after the
blast treatment. It is difficult to measure the surface roughness
of the expanded metal. Thus, in Comparative Example 9, a titanium
plate having, a thickness of 1 mm was simultaneously subjected to
the blast treatment during the blasting, and the surface roughness
of the titanium plate was taken as the surface roughness of the
wire mesh. The arithmetic average roughness Ra was 0.59 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, the above evaluation was performed in the same manner as
in Example 16, and the results are shown in Table 2.
[2547] The thickness of the electrode was 1011 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 11 .mu.m.
[2548] The mass per unit area was 245.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2549] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2550] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
Comparative Example 10
[2551] In Comparative Example 10, a membrane electrode assembly was
produced by thermally compressing an electrode onto a membrane with
reference to a prior art document (Examples of Japanese Patent
Laid-Open No. 58-48686).
[2552] A nickel expanded metal having a gauge thickness of 100
.mu.m and an opening ratio or 33% was used as the substrate for
electrode for cathode electrolysis to perform electrode coating in
the same manner as in Example 1. Thereafter, one surface of the
electrode was subjected to an inactivation treatment in the
following procedure. Polyimide adhesive tape (Chukoh Chemical
Industries, Ltd.) was attached to one surface of the electrode. A
PTFE dispersion (Dupont-Mitsui Cluorochemicals Co., Ltd., 31-JR
(trade name)) was applied onto the other surface and dried in a
muffle furnace at 120.degree. C. for 10 minutes. The polyimide tape
was peeled off, and a sintering treatment was performed in a muffle
furnace set at 380.degree. C. for 10 minutes. This operation was
repeated twice to inactivate the one surface of the electrode.
[2553] Produced was a membrane formed by two layers of a
perfluorocarbon polymer of which terminal functional group is
"--COOCH.sub.3" (C polymer) and a perfluorocarbon polymer of which
terminal group is "--SO.sub.2F" (S polymer). The thickness of the C
polymer layer was 3 mils, and the thickness of the S polymer layer
was 4 mils. This two-layer membrane was subjected to a
saponification treatment to thereby introduce ion exchange groups
to the terminals of the polymer by hydrolysis. The C polymer
terminals were hydrolyzed into carboxylic acid groups and the S
polymer terminals into sulfo groups. The ion exchange capacity as
the sulfonic acid group was 1.0 meq/g, and the ion exchange
capacity as the carboxylic acid group was 0.9 meq/g.
[2554] The inactivated electrode surface was oppositely disposed to
and thermally pressed onto the surface having carboxylic acid
groups as the ion exchange groups to integrate the ion exchange
membrane and the electrode. The one surface of the electrode was
exposed even after the thermal compression, and the electrode
passed through no portion of the membrane.
[2555] Thereafter, in order to suppress attachment of bubbles to be
generated during electrolysis to the membrane, a mixture of
zirconium oxide and a perfluorocarbon polymer into which sulfo
groups had been introduced was applied onto both the surfaces.
Thus, the membrane electrode assembly of Comparative Example 10 was
produced.
[2556] When the force applied per unit massunit area (1) was
measured using this membrane electrode assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.50 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The membrane electrode assembly of Comparative Example
10 had a force applied per unit massunit area (1) of at least 1.50
(N/mgcm.sup.2) and was strongly bonded.
[2557] When evaluation of winding around column of 280 mm in
diameter (1) was performed, the area in contact with the plastic
pipe was less than 5%. Meanwhile, when evaluation of winding around
column of 280 mm in diameter (2) was performed, the electrode and
the membrane were 100% bonded to each other, but the membrane was
not wound around the column in the first place. The result of
evaluation of winding around column of 145 mm in diameter (3) was
the same. The result meant that the integrated electrode impaired
the handling property of the membrane to thereby make it difficult
to roll the membrane into a roll and fold the membrane. The
handling property was "3", which was problematic. The membrane
damage was evaluated as "0". Additionally, when electrolytic
evaluation was performed, the voltage was high, the current
efficiency was low, the common salt concentration in caustic soda
(value converted on the basis of 50%) was raised, and the
electrolytic performance deteriorated.
[2558] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 14 .mu.m.
[2559] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[2560] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Comparative Example 11
[2561] In Comparative Example 11, a 40-mesh nickel mesh having a
line diameter of 150 .mu.m, a gauge thickness of 300 .mu.m, and an
opening ratio of 58% was used as the substrate for electrode for
cathode electrolysis. Except for the above described, a membrane
electrode assembly was produced in the same manner as in
Comparative Example 10.
[2562] When the force applied per unit massunit area (1) was
measured using this membrane electrode assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.60 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The membrane electrode assembly of Comparative Example
11 had a force applied per unit massunit area (1) of at least 1.60
(N/mgcm.sup.2) and was strongly bonded.
[2563] When evaluation of winding around column of 280 mm in
diameter (1) was performed using this membrane electrode assembly,
the contact area with the plastic pipe was less than 5%. Meanwhile,
when evaluation. of winding around column of 280 mm in diameter (2)
was performed, the electrode and the membrane were 100% bonded to
each other, but the membrane was not wound around the column in the
first place. The result of evaluation of winding around column of
145 mm in diameter (3) was the same. The result meant that the
integrated electrode impaired the handling property of the membrane
to thereby make it difficult to roll the membrane into a roll and
fold the membrane. The handling property was "3", which was
problematic. Additionally, when electrolytic evaluation was
performed, the voltage was high, the current efficiency was low,
the common salt concentration in caustic soda was raised, and the
electrolytic performance deteriorated.
[2564] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2565] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[2566] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
Comparative Example 12
(Preparation of Catalyst)
[2567] A metal salt aqueous solution was produced by adding 0.728 g
of silver nitrate (Wako Pure Chemical Industries, Ltd.) and 1.86 g
of cerium nitrate hexahydrate (Wako Pure Chemical Industries, Ltd.)
to 150 ml of pure water. An alkali solution was produced by adding
240 g of pure water to 100 g of a 15% tetramethylammonium hydroxide
aqueous solution (Wako Pure Chemical Industries, Ltd.). While the
alkali solution was stirred using a magnetic stirrer, the metal
salt aqueous solution was added thereto dropwise at 5 ml/minute
using a buret. A suspension containing the resulting metal
hydroxide particulates was suction-filtered and then washed with
water to remove the alkali content. Thereafter, the residue was
transferred into 200 ml of 2-propanol (KISHIDA CHEMICAL Co., Ltd.)
and redispersed by an ultrasonic dispersing apparatus (US-600T,
NISSEI Corporation) for 10 minutes to obtain a uniform
suspension.
[2568] A suspension of carbon black was obtained by dispersing 0.36
g of hydrophobic carbon black (DENKA BLACK(R) AB-7 (trade name),
Denka Company Limited) and 0.84 g of hydrophilic carbon black
(Ketjenblack(R) EC-600JD (trade name), Mitsubishi Chemical
Corporation) in 100 ml of 2-propanol and dispersing the mixture by
the ultrasonic dispersing apparatus for 10 minutes. The metal
hydroxide precursor suspension and the carbon black suspension were
mixed and dispersed by the ultrasonic dispersing apparatus for 10
minutes. This suspension was suction-filtered and dried at room
temperature for half a day to obtain carbon black containing the
metal hydroxide precursor dispersed and fixed. Subsequently, an
inert gas baking furnace (VMF165 type, YAMADA DENKI CO., LTD.) was
used to perform baking in a nitrogen atmosphere at 400.degree. C.
for an hour to obtain carbon black A containing an electrode
catalyst dispersed and fixed.
(Production of Powder for Reaction Layer)
[2569] To 1.6 g of the carbon black A containing an electrode
catalyst dispersed and fixed, 0.84 ml of a surfactant Triton(R)
X-100(trade name, ICN Biomedicals) diluted to 20% by weight with
pure water and 15 ml of pure water, and the mixture was dispersed
by an ultrasonic dispersing apparatus for 10 minutes. To this
dispersion, 0.664 g of a polytetrafluoroethylene (PTFE) dispersion
(PTFE30J (trade name), Dupont-Mitsui Fluorochemicals Co., Ltd.) was
added. After the mixture was stirred for five minutes, suction
filtration was performed. Additionally, the residue was dried in a
dryer at 80.degree. C. for an hour, and pulverization was performed
by a mill to obtain a powder for reaction layer A.
(Production of Powder for Gas Diffusion Layer)
[2570] Dispersed were 20 g of hydrophobic carbon black (DENKA
BLACK(R) AB-7 (trade name)), 50 ml of a surfactant Triton(R) X-100
(trade name) diluted to 20% by weight with pure water, and 360 ml
of pure, water by an ultrasonic dispersing apparatus for 10
minutes. To the resulting dispersion, 22.32 g of the PTFE
dispersion was added. The mixture was stirred for 5 minutes, and
then, filtration was performed. Additionally, the residue was dried
in a dryer at 80.degree. C. for an hour, and pulverization was
performed by a mill to obtain a powder for gas diffusion layer
A.
(Production of Gas Diffusion Electrode)
[2571] To 4 g of the powder for gas diffusion layer A, 8.7 ml of
ethanol was added, and the mixture was kneaded into a paste form.
This powder for gas diffusion layer in a paste form was formed into
a sheet form by a roll former. Silver mesh (SW=1, LW=2, and
thickness=0.3 mm) as the collector was embedded into the sheet and
finally formed into a sheet form having a thickness of 1.8 mm. To 1
g of the powder for reaction layer A, 2.2 ml of ethanol was added,
and the mixture was kneaded into a paste form. This powder for
reaction layer in a paste form was formed into a sheet form having
a thickness of 0.2 mm. Additionally, the two sheets, that is, the
sheet obtained by using the powder for gas diffusion layer A
produced and the sheet obtained by using the powder for reaction
layer A were laminated and formed into a sheet form having a
thickness of 1.8 mm by a roll former. This laminated sheet was
dried at room temperature for a whole day and night to remove
ethanol. Further, in order to remove the remaining surfactant, the
sheet was subjected to a pyrolysis treatment in air at 300.degree.
C. for an hour. The sheet was wrapped in an aluminum foil, and
subjected to hot pressing by a hot pressing machine (SA303 (trade
name), TESTER SANGYO CO., LTD.) at 360.degree. C. and 50
kgf/cm.sup.2 for 1 minute to obtain a gas diffusion electrode. The
thickness of the gas diffusion electrode was 412 .mu.m.
[2572] The resulting electrode was used to perform electrolytic
evaluation. In the sectional structure of the electrolytic cell,
the collector, the mattress, the nickel mesh feed conductor, the
electrode, the membrane, and the anode are arranged in the order
mentioned from the cathode chamber side to form a zero-gap
structure. The results are shown in Table 2.
[2573] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 19 mm.
[2574] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 25.88 (kPas/m) under the
measurement condition 1.
[2575] The handling property was "3", which was problematic.
Additionally, when electrolytic evaluation was performed, the
current efficiency was low, the common salt concentration in
caustic soda was raised, and the electrolytic performance markedly
deteriorated. The membrane damage, which was evaluated as "3", also
bad a problem.
[2576] These results have revealed that the gas diffusion electrode
obtained in Comparative Example 12 had markedly poor electrolytic
performance. Additionally, damage was observed on the substantially
entire surface of the ion exchange membrane. It was conceived that
this is because NaOH that had been generated in the electrode
accumulated on the interface between the electrode and the membrane
to elevate the concentration thereof, due to the markedly high
ventilation resistance of the gas diffusion electrode of
Comparative Example 12.
Comparative Example 13
[2577] A nickel line having a gauge thickness of 150 .mu.m was
provided as the substrate for electrode for cathode electrolysis. A
roughening treatment by this line was performed. It is difficult to
measure the surface roughness of the nickel line. Thus, in
Comparative Example 13, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the nickel line. A blast treatment was
performed with alumina of grain-size number 320. The arithmetic
average roughness Ra was 0.64 .mu.m.
[2578] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[2579] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088 (trade name), thickness 10 mm) around a
polyvinyl chloride (PVC) cylinder was always in contact with the
above coating liquid. A coating roll around which the same EPDM had
been wound was placed at the upper portion thereof, and a PVC
roller was further placed thereabove. The coating liquid was
applied by allowing the substrate for electrode to pass between the
second coating roll and the PVC roller at the uppermost portion
(roll coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of one nickel line produced in Comparative Example 13
was 158 .mu.m.
[2580] The nickel line produced by the above method was cut into a
length of 110 mm and a length of 95 mm. As shown in FIG. 16, the
110 mm nickel line and the 95 mm nickel line were placed surface
that the nickel lines vertically overlapped each other at the
center of each of the nickel lines and bonded to each other at the
intersection with an instant adhesive (Aron Alpha(R), TOAGOSEI CO.,
LTD.) to produce an electrode. The electrode was evaluated, and the
results are shown in Table 2.
[2581] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.7%.
[2582] The mass per unit area of the electrode was 0.5
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[2583] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 15 mm.
[2584] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance value was 0.0002 (kPas/m).
[2585] Additionally, the structure shown in FIG. 17 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.16 V.
Comparative Example 14
[2586] In Comparative Example 14, the electrode produced in
Comparative Example 13 was used. As shown in FIG. 18, the 110 mm
nickel line and the 95 mm nickel line were placed such that the
nickel lines vertically overlapped each other at the center of each
of the nickel lines and bonded to each other at the intersection
with an instant adhesive (Aron Alpha(R), TOAGOSEI CO., LTD.) to
produce an electrode. The electrode was evaluated, and the results
are shown in Table 2.
[2587] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.4%.
[2588] The mass per unit area of the electrode was 0.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[2589] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 16 mm.
[2590] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0004 (kPas/m).
[2591] Additionally, the structure shown in FIG. 19 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
Comparative Example 15
[2592] In Comparative Example 15, the electrode produced in
Comparative Example 13 was used. As shown in FIG. 20, the 110 mm
nickel line and the 95 mm nickel line were placed such that the
nickel lines vertically overlapped each other at the center of each
of the nickel lines and bonded to each other at the intersection
with an instant adhesive (Aron Alpha(R), TOAGOSEI CO., LTD.) to
produce an electrode. The electrode was evaluated, and the results
are shown in Table 2.
[2593] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 98.8%.
[2594] The mass per unit area of the electrode was 1.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[2595] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 14 mm.
[2596] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0005 (kPas/m).
[2597] Additionally, the structure shown in FIG. 21 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
TABLE-US-00001 TABLE 1 Substrate for Form of substrate Coating
electrode for electrode method Feed conductor Example 1 Ni Punching
Pyrolysis Ni mesh Example 2 Ni Punching Pyrolysis Ni mesh Example 3
Ni Punching Pyrolysis Ni mesh Example 4 Ni Punching Pyrolysis Ni
mesh Example 5 Ni Punching Pyrolysis Ni mesh Example 6 Ni Punching
Ion plating Ni mesh Example 7 Ni Electroforming Pyrolysis Ni mesh
Example 8 Ni Electroforming Pyrolysis Ni mesh Example 9 Ni Nonwoven
fabric Pyrolysis Ni mesh Example 10 Ni Nonwoven fabric Pyrolysis Ni
mesh Example 11 Ni Foamed Ni Pyrolysis Ni mesh Example 12 Ni Mesh
Pyrolysis Ni mesh Example 13 Ni Mesh Pyrolysis Ni mesh Example 14
Ni Punching (same Pyrolysis Mattress as in Example 3) Example 15 Ni
Punching (same Pyrolysis Cathode having increase in voltage as in
Example 3) Example 16 Ti Punching Pyrolysis Anode having increase
in voltage Example 17 Ti Punching Pyrolysis Anode having increase
in voltage Example 18 Ti Punching Pyrolysis Anode having increase
in voltage Example 19 Ti Punching Pyrolysis Anode having increase
in voltage Example 20 Ti Nonwoven fabric Pyrolysis Anode having
increase in voltage Example 21 Ti Mesh Pyrolysis Anode having
increase in voltage Example 22 Ni/Ti Combination of Pyrolysis
Cathode and anode having increase in voltage Example 3 and Example
20 Example 23 Ni Punching Pyrolysis -- Example 24 Carbon Woven
fabric Pyrolysis Ni mesh Comparative Example 1 Ni Expanded
Pyrolysis Ni mesh Comparative Example 2 Ni Expanded Pyrolysis Ni
mesh Comparative Example 3 Ni Expanded Ion plating Ni mesh
Comparative Example 4 Ni Expanded Pyrolysis Ni mesh Comparative
Example 5 Ni Mesh Pyrolysis Ni mesh Comparative Example 6 Ni Mesh
Pyrolysis Ni mesh Comparative Example 7 Ti Expanded Pyrolysis Anode
having increase in voltage Comparative Example 8 Ti Expanded
Pyrolysis Anode having increase in voltage Comparative Example 9 Ti
Expanded Pyrolysis Anode having increase in voltage Comparative
Example 10 Ni Expanded Pyrolysis Ni mesh Comparative Example 11 Ni
Mesh Pyrolysis Ni mesh Comparative Example 12 Carbon Powder
Pyrolysis Ni mesh Comparative Example 13 Ni Mesh Pyrolysis Ni mesh
Comparative Example 14 Ni Mesh Pyrolysis Ni mesh Comparative
Example 15 Ni Mesh Pyrolysis Ni mesh
TABLE-US-00002 TABLE 2 Thickness of substrate for electrode for
Thickness of Thickness Mass per Force applied per unit electrolysis
electrode of catalytic Opening ratio unit area mass unit area (1)
(.mu.m) (.mu.m) layer (.mu.m) (void ratio) % (mg/cm.sup.2) (N/mg
cm.sup.2-electrode) Example 1 16 24 8 49 5.8 0.90 Example 2 22 29 7
44 9.9 0.61 Example 3 30 38 8 44 11.1 0.43 Example 4 16 24 8 75 3.5
0.28 Example 5 20 30 10 49 6.4 0.59 Example 6 16 26 10 49 6.2 0.81
Example 7 20 37 17 56 8.1 0.79 Example 8 50 60 10 56 18.1 0.13
Example 9 150 165 15 76 31.9 0.22 Example 10 200 215 15 72 46.3
0.12 Example 11 200 210 10 72 36.5 0.13 Example 12 100 110 10 37
27.4 0.18 Example 13 130 133 3 38 36.3 0.15 Example 14 30 38 8 44
11.1 0.43 Example 15 30 38 8 44 11.1 0.43 Example 16 20 26 6 14 8.9
0.16 Example 17 20 30 10 30 8.1 0.26 Example 18 20 32 12 42 6.6
0.24 Example 19 50 69 19 47 12.9 0.12 Example 20 100 114 14 78 11.3
0.59 Example 21 120 140 20 42 14.9 0.47 Example 22 30/100 38/114
8/14 44/78 11.1/11.3 0.43/0.59 Example 23 30 38 8 44 11.1 0.28
Example 24 566 570 4 83 21.8 0.270 Comparative Example 1 100 114 14
33 67.5 0.05 Comparative Example 2 100 107 7 16 78.1 0.04
Comparative Example 3 100 110 10 40 37.8 0.07 Comparative Example 4
100 109 9 58 39.2 0.06 Comparative Example 5 300 308 8 56 49.2 0.18
Comparative Example 6 200 210 10 37 56.4 0.09 Comparative Example 7
500 508 8 17 152.5 0.01 Comparative Example 8 800 808 8 8 251.3
0.01 Comparative Example 9 1000 1011 11 46 245.5 0.01 Comparative
Example 10 100 114 14 33 67.5 1.50 Comparative Example 11 300 308 8
58 49.2 1.80 Comparative Example 12 412 412 -- -- 101 0.005
Comparative Example 13 300 306 6 99.7 0.5 Equal to or less than the
measurement lower limit Comparative Example 14 300 306 6 99.4 0.9
Equal to or less than the measurement lower limit Comparative
Example 15 300 306 6 98.8 1.9 Equal to or less than the measurement
lower limit Method for Method for Method for evaluating evaluating
evaluating winding winding winding around around around column of
column of column of 280 mm in 145 mm in 280 mm in diameter (2)
diameter (3) diameter (1) (membrane (membrane Handing Force applied
per unit (membrane and and property mass unit area (2) and column)
electrode) electrode) (sensory (N/mg cm.sup.2-electrode) (%) (%)
(%) evaluation) Example 1 0.640 100 100 100 1 Example 2 0.235 100
100 100 1 Example 3 0.194 100 100 100 1 Example 4 0.113 100 100 100
1 Example 5 0.386 100 100 100 1 Example 6 0.650 100 100 100 1
Example 7 0.184 100 100 100 1 Example 8 0.088 100 100 100 1 Example
9 0.217 100 100 100 2 Example 10 0.081 100 100 79 2 Example 11
0.162 100 100 100 2 Example 12 0.126 100 100 100 1 Example 13 0.098
100 100 88 2 Example 14 0.194 100 100 100 1 Example 15 0.194 100
100 100 1 Example 16 0.105 100 100 100 1 Example 17 0.132 100 100
100 1 Example 18 0.147 100 100 100 1 Example 19 0.08 100 100 100 1
Example 20 0.378 100 100 100 1 Example 21 0.306 100 100 100 1
Example 22 0.194/0.378 100/100 100/100 100/100 1/1 Example 23 0.194
100 100 100 1 Example 24 0.3 100 100 100 2 Comparative Example 1
0.045 100 64 22 4 Comparative Example 2 0.027 100 37 25 4
Comparative Example 3 0.045 100 80 32 3 Comparative Example 4 0.034
100 69 39 3 Comparative Example 5 0.138 100 88 42 3 Comparative
Example 6 0.060 100 100 63 3 Comparative Example 7 0.005 100 Less
than 5 Less than 5 4 Comparative Example 8 0.006 100 Less than 5
Less than 5 4 Comparative Example 9 0.005 100 Less than 5 Less than
5 4 Comparative Example 10 -- Less than 5 -- -- 3 Comparative
Example 11 -- Less than 5 -- -- 3 Comparative Example 12 0.005 Less
than 5 -- -- 3 Comparative Example 13 Equal to or less than the
Less than 5 -- -- 4 measurement lower limit Comparative Example 14
Equal to or less than the Less than 5 -- -- 4 measurement lower
limit Comparative Example 15 Equal to or less than the Less than 5
-- -- 4 measurement lower limit Elastic deformation test of
electrode Electrolytic evaluation (winding around Common salt vinyl
chloride Ventilation Ventilation concentration pipe of 32 mm in
resistance resistance Current in caustic soda outer diameter) (KPa
s/m) (KPa s/m) Membrane Voltage efficiency (ppm, on the average
value of (measurement (measurement damage (V) (%) basis of 50%)
L.sub.1 and L.sub.2 (mm) condition 1) condition 2) evaluation
Example 1 2.98 97.7 15 0 0.07 or less 0.0028 0 Example 2 2.95 97.2
18 0 0.07 or less 0.0033 0 Example 3 2.96 97.6 19 0 0.07 or less
0.0027 0 Example 4 2.97 97.5 15 0 0.07 or less 0.0023 0 Example 5
2.95 97.1 18 0 0.07 or less 0.0023 0 Example 6 2.96 97.3 14 0 0.07
or less 0.0028 0 Example 7 2.96 97.3 15 0 0.07 or less 0.0032 0
Example 8 2.96 97.7 16 0 0.07 or less 0.0032 0 Example 9 2.97 96.8
23 29 0.07 or less 0.0612 0 Example 10 2.96 96.7 26 40 0.07 or less
0.0164 0 Example 11 3.05 97.4 22 17 0.07 or less 0.0402 0 Example
12 3.11 97.2 23 0.5 0.07 or less 0.0154 0 Example 13 3.09 97.0 25
6.5 0.07 or less 0.0124 0 Example 14 2.97 97.3 18 0 0.07 or less
0.0027 0 Example 15 2.96 97.2 21 0 0.07 or less 0.0027 0 Example 16
3.10 96.8 19 4 0.07 or less 0.0060 0 Example 17 3.07 96.8 26 5 0.07
or less 0.0030 0 Example 18 3.08 97.7 21 2.5 0.07 or less 0.0022 0
Example 19 3.09 97.0 21 8 0.07 or less 0.0024 0 Example 20 2.97
96.8 24 2 0.07 or less 0.0228 0 Example 21 2.99 97.0 18 10 0.07 or
less 0.0132 0 Example 22 3.00 97.2 17 0/2 0.07 or less
0.0027/0.0228 0 Example 23 -- -- -- 0 0.07 or less 0.0027 --
Example 24 3.19 97.0 20 0 0.19 0.176 1 Comparative Example 1 2.98
97.7 19 13 0.07 or less 0.0168 0 Comparative Example 2 2.99 97.8 17
18.5 0.07 or less 0.0176 0 Comparative Example 3 2.96 97.5 18 11
0.07 or less 0.0030 0 Comparative Example 4 2.99 97.6 18 11.5 0.07
or less 0.0028 0 Comparative Example 5 2.95 97.5 24 23 0.07 or less
0.0034 0 Comparative Example 6 2.98 97.3 23 19 0.07 or less 0.0096
0 Comparative Example 7 2.99 96.7 23 Remained 0.07 or less 0.0072 0
Comparative Example 8 3.02 97.0 19 deformed in vinyl 0.07 or less
0.0172 0 Comparative Example 9 3.00 97.2 20 chloride form and 0.07
or less 0.0027 0 did not return Comparative Example 10 3.67 93.8
226 13 0.07 or less 0.0168 0 Comparative Example 11 3.71 94.5 155
23 0.07 or less 0.0034 0 Comparative Example 12 3.65 48.0 680 19
25.88 -- 3 Comparative Example 13 3.16 97.5 21 15 0.07 or less
0.0002 0 Comparative Example 14 3.18 97.4 19 16 0.07 or less 0.0004
0 Comparative Example 15 3.18 97.3 20 14 0.07 or less 0.0005 0
[2598] In Table 2, all the samples were able to stand by themselves
by the surface tension before measurement of "force applied per
unit massunit area (1)" and "force applied per unit a massunit area
(2)" (i.e., did not slip down).
[2599] In Comparative Examples 1, 2, 7 to 9, since the mass per
unit area was large and the force applied per unit massunit area
(1) was small, the adhesiveness to the membrane was poor. Thus,
with a large electrolyzer size (e.g., 1.5 m in length and 3 m in
width), the membrane, which is a polymer membrane, may be
inevitably slacked during handling. In this time, the electrode
comes off and thus, the samples do not withstand practical use.
[2600] In Comparative Examples 3 and 4, since the force applied per
unit massunit area (1) was small, the adhesiveness to the membrane
was poor. Thus, with a large electrolyzer size (e.g., 1.5 m in
length and 3 m in width), the membrane, which is a polymer
membrane, may be inevitably slacked during handling. In this time,
the electrode comes off and, thus, the samples do not withstand,
practical use.
[2601] In Comparative Examples 5 and 6, the mass per unit area is
large, and the adhesiveness to the membrane was poor. Thus, with a
large electrolyzer size (e.g., 1.5 m in length and 3 m in width),
the membrane, which is a polymer membrane, may be inevitably
slacked during handling. In this time, the electrode comes off and
thus, the samples do not withstand practical use.
[2602] In Comparative Examples 10 and 11, since the membrane and
the electrode were tightly bonded by thermal pressing, the
electrode did not come off from the membrane during handling like
Comparative Examples 1, 2, 7 to 9. However, due to the tight
bonding to the electrode, the flexibility of the polymer membrane
was lost. Thus, it is difficult to roll the samples into a roll and
fold the samples. The samples have poor handling property and do
not withstand practical use.
[2603] Furthermore, in Comparative Examples 10 and 11, the
electrolytic performance significantly deteriorated. Conceivably,
the voltage markedly increased because the flow of ions was
inhibited by the fact that the electrode became embedded in the ion
exchange membrane. With respect to the reason of the decrease in
the current efficiency and the degradation of the common salt
concentration in caustic soda, possible factors included high
current efficiency, occurrence of uneven thickness or the
carboxylic acid layer due to embedding the electrode in the
carboxylic acid layer having an effect of exhibiting ion
selectivity, and penetration of the electrode embedded into a port
the carboxylic acid layer.
[2604] Additionally, in Comparative Examples 10 and 11, in the case
where a problem occurred either in the membrane or the electrode
and replacement was required, it was not possible to replace one of
the membrane and the electrode due to the tight bonding, which led
to a higher cost.
[2605] In Comparative Example the electrolytic performance
significantly deteriorated. Conceivably, the voltage mark increased
because a product accumulated on the interface between the membrane
and the electrode.
[2606] In Comparative Examples 1 3 to 15, both the forces applied
per unit mass unit area (1) and (2) were small (equal to or less
than the measurement lower limit), and thus, the adhesiveness to
the membrane was poor. Thus, with a large electrolyzer size (e.g.,
1.5 m in length and 3 m in width), the membrane, which is a polymer
membrane, may be inevitably slacked during handling. In this time,
the electrode comes off and thus, the samples do not withstand
practical use.
[2607] In the present embodiment, the membrane and the electrode
are in close contact with each other on each surface with a
moderate force, and thus, there are no problems such as coming-off
of the electrode during handling. The flow of ions in the membrane
is not inhibited, and thus, good electrolytic performance is
exhibited.
<Verification of Second Embodiment>
[2608] As will be described below, Experiment Examples according to
the second embodiment (in the section of <Verification of second
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the second embodiment (in the
section of <Verification of second embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 31 to 42 as appropriate.
[Evaluation Method]
(1) Opening Ratio
[2609] An electrode was cut into a size of 130 mm.times.100 mm. A
digimatic thickness gauge (manufactured by Mitutoyo Corporation,
minimum scale 0.001 mm) was used to calculate an average value of
10 points obtained by measuring evenly in the plane. The value was
used as the thickness of the electrode (gauge thickness) to
calculate the volume. Thereafter, an electronic balance was used to
measure the mass. From the specific gravity of each metal (specific
gravity of nickel=8.908 g/cm.sup.3, specific gravity of
titanium=4.506 g/cm.sup.3), the opening ratio or void ratio was
calculated.
Opening ratio (Void ratio) (%)=(1-(electrode mass)/(electrode
volume.times.metal specific gravity)).times.100
(2) Mass per Unit Area (mg/cm.sup.2)
[2610] An electrode was cut into a size of 130 mm.times.100 mm, and
the mass thereof was measured by an electronic balance. The value
was divided by the area (130 mm.times.100 mm) to calculate the mass
per unit area.
(3) Force Applied per Unit MassUnit Area (1) (Adhesive Force)
(N/mgcm.sup.2))
[2611] [Method (i)]
[2612] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-6001
type load cell).
[2613] A 200 mm square nickel plate having a thickness of 1.2 mm
was subjected to blast processing with alumina of grain-size number
320. The arithmetic average surface roughness (Ra) of the nickel
plate after the blast treatment was 0.7 .mu.m. For surface
roughness measurement herein, a probe type surface roughness
measurement instrument SJ-310 (Mitutoyo Corporation) was used. A
measurement sample was placed on the surface plate parallel to the
ground surface to measure the arithmetic average roughness Ra under
measurement conditions as described below. The measurement was
repeated 6 times, and the average value was listed.
[2614] <Probe shape> conical taper angle=60.degree., tip
radius=2 .mu.m, static measuring force=0.75 mN
[2615] <Roughness standard> JIS2001
[2616] <Evaluation curve> R
[2617] <Filter> GAUSS
[2618] <Cutoff value .lamda.c> 0.8 mm
[2619] <Cutoff value .lamda.s> 2.5
[2620] <Number of sections> 5
[2621] <Pre-running, post-running> available
[2622] This nickel plate was vertically fixed on the lower chuck of
the tensile and compression testing machine.
[2623] As the membrane, an ion exchange membrane A below was
used.
[2624] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTFE) were used (hereinafter
referred to as PTFE yarns). As sacrifice yarns, yarns obtained by
twisting six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
two sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[2625] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2=CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin B of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[2626] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[2627] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[2628] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour to replace the counterion of
the ion exchange group by Na, and then washed with water. Then, the
membrane was dried at 60.degree. C.
[2629] Further, 20% by mass of zirconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. The average particle size was measured by a
particle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[2630] The ion exchange membrane (membrane) obtained above was
immersed in pure water for 12 hours or more and then used for the
test. The membrane was brought into contact with the above nickel
plate sufficiently moistened with pure water and allowed to adhere
to the plate by the tension of water. At this time, the nickel
plate and the ion exchange membrane were placed so as to align the
upper ends thereof.
[2631] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped by the upper chuck of the
tensile and compression testing machine to hang the electrode. The
load applied on the testing machine at this time was set to 0 N.
The integrated piece of the stainless plates, electrode, and clips
was once removed from the tensile and compression testing machine,
and immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[2632] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the ion exchange membrane
by the surface tension of pure water. The size of the adhesive
surface at this time was 130 mm in width and 110 mm in length. Pure
water in a wash bottle was sprayed to the electrode and the ion
exchange membrane entirely so as to sufficiently moisten the
membrane and the electrode again. Thereafter, a roller formed by
winding a closed-cell type EPDM sponge rubber having a thickness of
5 mm around a vinyl chloride pipe (outer diameter: 38 mm) was
rolled downward from above with lightly pressed over the electrode
to remove excess pure water. The roller was rolled only once.
[2633] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the overlapping
portion of the electrode and the membrane reached 130 mm in width
and 100 mm in length was recorded. This measurement was repeated
three times, and the average value was calculated.
[2634] This average value was divided by the area of the
overlapping portion of the electrode and the ion exchange membrane
and the mass of the electrode of the portion overlapping the ion
exchange membrane to calculate the force applied per unit massunit
area (1). The mass of the electrode of the portion overlapping the
ion exchange membrane was determined through proportional
calculation from the value obtained in (2) Mass per unit area
(mg/cm.sup.2) described above.
[2635] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity was
30.+-.5%.
[2636] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to the ion exchange membrane that
adhered to a vertically fixed nickel plate via the surface
tension.
[2637] A schematic view of a method for evaluating the force
applied is shown in FIG. 31.
[2638] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(4) Force Applied per Unit MassUnit Area (2) (Adhesive Force)
(N/mgcm.sup.2))
[2639] [Method (ii)]
[2640] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-6001
type load cell).
[2641] A nickel plate identical to that in Method (i) was
vertically fixed on the lower chuck of the tensile and compression
testing machine.
[2642] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped by the upper chuck of the
tensile and compression testing machine to hang the electrode. The
load applied on the testing machine at this time was set to 0 N.
The integrated piece of the stainless plates, electrode, and clips
was once removed from the tensile and compression testing machine,
and immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[2643] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the nickel plate via the
surface tension of a solution. The size of the adhesive surface at
this time was 130 mm in width and 110 mm in length. Pure water in a
wash bottle was sprayed to the electrode and the nickel plate
entirely so as to sufficiently moisten the nickel plate and the
electrode again. Thereafter, a roller formed by winding a
closed-cell type EPDM sponge rubber having a thickness of 5 mm
around a vinyl chloride pipe (outer diameter: 38 mm) was rolled
downward from above with lightly pressed over the electrode to
remove excess solution. The roller was rolled only once.
[2644] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the overlapping
portion of the electrode and the nickel plate in the longitudinal
direction reached 100 mm was recorded. This measurement was
repeated three times, and the average value was calculated.
[2645] This average value was divided by the area of the
overlapping portion of the electrode and the nickel plate and the
mass of the electrode of the portion overlapping the nickel plate
to calculate the force applied per unit massunit area (2). The mass
of the electrode of the portion overlapping the membrane was
determined through proportional calculation from the value obtained
in (2) Mass per unit area (mg/cm.sup.2) described above.
[2646] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity was
30.+-.5%.
[2647] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to a vertically-fixed nickel plate via
the surface tension.
[2648] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(5) Method for Evaluating Winding Around Column of 280 mm in
Diameter (1) (%)
(Membrane and Column)
[2649] The evaluation method (1) was conducted by the following
procedure.
[2650] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In Comparative Examples 1 and 2, the electrode had been
integrated with the ion exchange membrane by thermal pressing, and
thus, an integrated piece of an ion exchange membrane and an
electrode was provided (electrode of a 130 mm square). After the
ion exchange membrane was sufficiently immersed in pure water, the
membrane was placed on the curved surface of a plastic
(polyethylene) pipe having an outer diameter of 280 mm. Thereafter,
excess solution was removed with a roller formed by winding a
closed-cell type EPDM sponge rubber having a thickness of 5 mm
around a vinyl chloride pipe (outer diameter: 38 mm). The roller
was rolled over the ion exchange membrane from the left to the
right of the schematic view shown in FIG. 32. The roller was rolled
only once. One minute after, the proportion of a portion at which
the ion exchange membrane was brought into a close contact with the
plastic pipe electrode having an outer diameter of 280 mm was
measured.
(6) Method for Evaluating Winding Around Column of 280 mm in
Diameter (2) (%)
(Membrane and Electrode)
[2651] The evaluation method (2) was conducted by the following
procedure.
[2652] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
130 mm square. The ion exchange membrane was immersed in pure water
for 12 hours or more and then used for the test. The ion exchange
membrane and the electrode were sufficiently immersed in pure water
and then laminated. This laminate was placed on the curved surface
of a plastic (polyethylene) pipe having an outer diameter of 280 mm
such that the electrode was located outside. Thereafter, a roller
formed by winding a closed-cell type EPDM sponge rubber having a
thickness of 5 mm around a vinyl chloride pipe (outer diameter: 38
mm) was rolled from the left to the right of the schematic view
shown in FIG. 33 with lightly pressed over the electrode to remove
excess solution. The roller was rolled only once. One minute after,
the proportion of a portion at which the ion exchange membrane was
brought into a close contact with the electrode was measured.
(7) Method for Evaluating Winding Around Column of 145 mm in
Diameter (3) (%)
(Membrane and Electrode)
[2653] The evaluation method (3) was conducted by the following
procedure.
[2654] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
130 mm square. The ion exchange membrane was immersed in pure water
for 12 hours or more and then used for the test. The ion exchange
membrane and the electrode were sufficiently immersed in pure water
and then laminated. This laminate was placed on the curved surface
of a plastic (polyethylene) pipe having an outer diameter of 145 mm
such that the electrode was located outside. Thereafter, a roller
formed by winding a closed-cell type EPDM sponge rubber having a
thickness of 5 mm around a vinyl chloride pipe (outer diameter: 38
mm) was rolled from the left to the right of the schematic view
shown in FIG. 34 with lightly pressed over the electrode to remove
excess solution. The roller was rolled only once. One minute after,
the proportion of a portion at which the ion exchange membrane was
brought into a close contact with the electrode was measured.
(8) Handling Property (Response Evaluation)
[2655] (A) The ion exchange membrane A (membrane) produced in
[Method (i)] was cut into a 170 mm square, and the electrode was
cut into a size of 95.times.110 mm. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In each Example, the ion exchange membrane and electrode were
sufficiently immersed in three solutions: sodium bicarbonate
aqueous solution, 0.1N NaOH aqueous solution, and pure water, then
laminated, and placed still on a Teflon plate. The interval between
the anode cell and the cathode cell used in the electrolytic
evaluation was set at about 3 cm. The laminate placed was lifted,
and an operation of inserting and holding the laminate therebetween
was conducted. This operation was conducted while the electrode was
checked for dislocation and dropping.
[2656] (B) The ion exchange membrane A (membrane) produced in
[Method (i)] was cut into a 170 mm square, and the electrode was
cut into a size of 95.times.110 mm. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In each Example, the ion exchange membrane and electrode were
sufficiently immersed in three solutions: a sodium bicarbonate
aqueous solution, a 0.1N NaOH aqueous solution, and pure water,
then laminated, and placed still on a Teflon plate. The adjacent
two corners of the membrane portion of the laminate were held by
hands to lift the laminate so as to be vertical. The two corners
held by hands were moved from this state to be close to each other
such that the membrane was protruded or recessed. This move was
repeated again to check the conformability of the electrode to the
membrane. The results were evaluated on a four level scale of 1 to
4 on the basis of the following indices:
[2657] 1: good handling property
[2658] 2: capable of being handled
[2659] 3: difficult to handle
[2660] 4: substantially incapable of being handled
[2661] Here, the sample of Comparative Example 2-5, provided in a
size equivalent to that of a large electrolytic cell including an
electrode in a size of 1.3 m.times.2.5 m and an ion exchange
membrane in a size of 1.5 m.times.2.8 m, was subjected to handling.
The evaluation result of Comparative Example 5 ("3" as described
below) was used as an index to evaluate the difference between the
evaluation of the above (A) and (B) and that of the large-sized
one. That is, in the case where the evaluation result of a small
laminate was "1" or "2", it was judged that there was no problem in
the handling property even if the laminate was provided in a larger
size.
(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%),
Common Salt Concentration in Caustic Soda (ppm, on the Basis of
50%))
[2662] The electrolytic performance was evaluated by the following
electrolytic experiment.
[2663] A titanium anode cell having an anode chamber in which an
anode was provided (anode terminal cell) and a cathode cell having
a nickel cathode chamber in which a cathode was provided (cathode
terminal cell) were oppositely disposed. A pair of gaskets was
arranged between the cells, and a laminate (a laminate of the ion
exchange membrane A and an electrode for electrolysis) was
sandwiched between the gaskets. Then, the anode cell, the gasket,
the laminate, the gasket, and the cathode were brought into close
contact together to obtain an electrolytic cell, and an
electrolyzer including the cell was provided.
[2664] The anode was produced by applying a mixed solution of
ruthenium chloride, iridium chloride, and titanium tetrachloride
onto a titanium substrate subjected to blasting and acid etching
treatment as the pretreatment, followed by drying and baking. The
anode was fixed in the anode chamber by welding. As the cathode,
one described in each of Examples and Comparative Examples was
used. As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. Nickel mesh formed
by plain-weaving nickel wire having a diameter of 150 .mu.m in a
sieve mesh size of 40 was placed thereover, and a string made of
Teflon(R) was used to fix the four corners of the Ni mesh to the
collector. This Ni mesh was used as a feed conductor. This
electrolytic cell has a zero-gap structure by use of the repulsive
force of the mattress as the metal elastic body. As the gaskets,
ethylene propylene diene (EPDM) rubber gaskets were used. As the
membrane, the ion exchange membrane A (160 mm square) produced in
[Method (i)] was used.
[2665] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted so as to allow the temperature in each
electrolytic cell to reach 90.degree. C. Common salt electrolysis
was performed current density of 6 kA/m.sup.2 to measure the
voltage, current efficiency, and common salt concentration in
caustic soda. The current efficiency here is the proportion of the
amount of the produced caustic soda to the passed current and when
impurity ions and hydroxide ions rather than sodium ions move
through the ion exchange membrane due to the passed current, the
current efficiency decreases. The current efficiency was obtained
by dividing the number of moles of caustic soda produced for a
certain time by the number of moles of the electrons of the current
passing during that time. The number of moles of caustic soda was
obtained by recovering caustic soda produced by the electrolysis in
a plastic container and measuring its mass. As the common salt
concentration in caustic soda, value obtained by converting the
caustic soda concentration on the basis of 50% was shown.
[2666] The specification of the electrode and the feed conductor
used in each of Examples and Comparative Examples is shown Table
3.
(11) Measurement Thickness of Catalytic Layer, Substrate for
Electrode for Electrolysis, and Thickness of Electrode
[2667] For the thickness of the substrate for electrode for
electrolysis, a digimatic thickness gauge (manufactured by Mitutoyo
Corporation, minimum scale 0.001 mm) was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane. The value was used as the thickness of the substrate for
electrode for electrolysis (gauge thickness). For the thickness of
the electrode, a digimatic thickness gauge was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane, in the same manner as for the substrate for electrode. The
value was used as the thickness of the electrode (gauge thickness).
The thickness of the catalytic layer was determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
(12) Elastic Deformation Test of Electrode
[2668] The ion exchange membrane A (membrane) and the electrode
produced in [Method (i)] were each cut into a 110 mm square. The
ion exchange membrane was immersed pure water for 12 hours or more
and then used for the test. After the ion exchange membrane and the
electrode were laminated to produce a laminate under conditions of
a temperature: 23.+-.2.degree. C. and a relative humidity: 30+5%,
the laminate was wound around a PVC pipe having an outer diameter
of .PHI.32 mm and a length of 20 cm without any gap, as shown in
FIG. 35. The laminate was fixed using a polyethylene cable tie such
that the laminate wound did not come off from the PVC pipe or
loosen. The laminate was retained in this state for 6 hours.
Thereafter, the cable tie was removed, and the laminate was unwound
from the PVC pipe. Only the electrode was placed on a surface
plate, and the heights L.sub.1 and L.sub.2 of a portion lifted from
the surface plate were measured to determine an average value. This
value was used as the index of the electrode deformation. That is,
a smaller value means that the laminate is unlikely to deform.
[2669] When an expanded metal is used, there are two winding
direction: the SW direction and the LW direction. In this test, the
laminate was wound in the SW direction.
[2670] Deformed electrodes (electrodes that did not return to their
original flat state) were evaluated for softness after plastic
deformation in accordance with a method as shown in FIG. 36. That
is a deformed electrode was placed on a membrane sufficiently
immersed pure water. One end of the electrode was fixed and the
other lifted end was pressed onto the membrane to release a force,
and an evaluation was performed whether the deformed electrode
conformed to the membrane.
(13) Membrane Damage Evaluation
[2671] As the membrane, an ion exchange membrane B below was
used.
[2672] As reinforcement core materials those obtained by twisting
100 denier tape yarns of polytetrafluoroethylene (PTFE) 900 times/m
into a thread form were used (hereinafter referred to as PTFE
yarns). As warp sacrifice yarns, yarns obtained by twist ng eight
35 denier filaments of polyethylene terephthalate (PET) 200 times/m
were used (hereinafter referred to as PET yarns). As weft sacrifice
yarns, yarns obtained by twisting eight 35 denier filaments of
polyethylene terephthalate (PET) 200 times/m were used. First, the
PTFE yarns and the sacrifice yarns were plain-woven with 24 PTFE
yarns/inch so that two sacrifice yarns were arranged between
adjacent PTFE yarns, to obtain a woven fabric having a thickness of
100 .mu.m.
[2673] Next, a polymer (A1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.92 mg equivalent/g and a
polymer (B1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g were provided.
Using these polymers (A1) and (B1), a two-layer film X in which the
thickness of a polymer (A1) layer was 25 .mu.m and the thickness of
a polymer (B1) layer was 89 .mu.m was obtained by a coextrusion T
die method. As the ion exchange capacity of each polymer, shown was
the ion exchange capacity in the case of hydrolyzing the ion
exchange group precursors of each polymer for conversion into ion
exchange groups.
[2674] Separately, a polymer (B2) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g was provided.
This polymer was single-layer extruded to obtain a film Y having a
thickness of 20 .mu.m.
[2675] Subsequently, release paper, the film Y, a reinforcing
material, and the film X were laminated in this order on a hot
plate having a heat source and a vacuum source inside and having
micropores on its surface, heated and depressurized under the
conditions of a hot plate temperature of 225.degree. C. and a
degree of reduced pressure of 0.022 MPa for two minutes, and then
the release paper was removed to obtain a composite membrane. The
resulting composite membrane was immersed in an aqueous solution
comprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH)
for an hour for saponification. Thereafter, the membrane was
immersed in 0.5N NaOH for an hour to replace the ions attached to
the ion exchange groups by Na, and then washed with water. Further,
the membrane was dried at 60.degree. C.
[2676] Additionally, a polymer (B3) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.05 mg equivalent/g were
hydrolyzed and then was turned into an acid type with hydrochloric
acid. Zirconium oxide particles having an average particle size of
primary particles of 0.02 .mu.m were added to a 50/50 (mass ratio)
mixed solution of water and ethanol in which the polymer (B3') of
this acid type was dissolved in a proportion of 5% by mass such
that the mass ratio of the polymer (B3') to the zirconium oxide
particles was 20/80. Thereafter, the polymer (B3') was dispersed in
a suspension of the zirconium oxide particles with a ball mill to
obtain a suspension.
[2677] This suspension was applied by a spray method onto both the
surfaces of the ion exchange membrane and dried to obtain an ion
exchange membrane B having a coating layer containing the polymer
(B3') and the zirconium oxide particles. The coating density of
zirconium oxide measured by fluorescent X-ray measurement was 0.35
mg/cm.sup.2.
[2678] The anode used was the same as in (9) Electrolytic
evaluation.
[2679] The cathode used was one described in each of Examples and
Comparative Examples. The collector, mattress, and feed conductor
of the cathode chamber used were the same as in (9) Electrolytic
evaluation. That is, a zero-gap structure had been provided by use
of Ni mesh as the feed conductor and the repulsive force of the
mattress as the metal elastic body. The gaskets used were the same
as in (9) Electrolytic evaluation. As the membrane, the ion
exchange membrane B produced by the method mentioned above was
used. That is, an electrolyzer equivalent to that in (9) was
provided except that the laminate of the ion exchange membrane B
and the electrode for electrolysis was sandwiched between a pair of
gaskets.
[2680] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted such that the temperature in each
electrolytic cell reached 70.degree. C. Common salt electrolysis
was performed at a current density of 8 kA/m.sup.2. The
electrolysis was stopped 12 hours after the start of the
electrolysis, and the ion exchange membrane B was removed and
observed for its damage condition.
[2681] "0" means no damage "1 to 3" means that damage was present,
and a larger number means a larger degree of damage.
(14) Ventilation Resistance of Electrode
[2682] The ventilation resistance of the electrode was measured
using an air permeability tester KES-F8 (trade name, KATO TECH CO.,
LTD.). The unit for the ventilation resistance value is kPas/m. The
measurement was repeated 5 times, and the average value was listed
in Table 4. The measurement was conducted under the following two
conditions. The temperature of the measuring chamber was 24.degree.
C. and the relative humidity was 32%.
Measurement Condition 1 (Ventilation Resistance 1)
[2683] Piston speed: 0.2 cm/s
[2684] Ventilation volume: 0.4 cc/cm.sup.2/s
[2685] Measurement range: SENSE L (low)
[2686] Sample size: 50 mm.times.50 mm
Measurement Condition 2 (Ventilation Resistance 2)
[2687] Piston speed: 2 cm/s
[2688] Ventilation volume: 4 cc/cm.sup.2/s
[2689] Measurement range: SENSE M (medium) or H (high)
[2690] Sample size: 50 mm.times.50 mm
Example 2-1
[2691] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 16 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.71
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[2692] A porous foil was formed by perforating this nickel foil
with circular holes by punching. The opening ratio was 49%.
[2693] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[2694] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a poly chloride
(PVC) cylinder was always in contact with the coating liquid. A
coating roll around which the same EPDM had been wound was placed
at the upper portion thereof, and a PVC roller was further placed
thereabove. The coating liquid was applied by allowing the
substrate for electrode to pass between the second coating roll and
the PVC roller at the uppermost portion (roll coating method).
Then, after drying at 50.degree. C. for 10 minutes, preliminary
baking at 150.degree. C. for 3 minutes, and baking at 350.degree.
C. for 10 minutes were performed. A series of these coating,
drying, preliminary baking, and baking operations was repeated
until a predetermined amount of coating was achieved. The thickness
of the electrode produced in Example 2-1 was 24 .mu.m. The
thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode, was 8 .mu.m. The
coating was formed also on the surface not roughened. The thickness
was the total thickness of ruthenium oxide and cerium oxide.
[2695] The measurement results of the adhesive force of the
electrode produced by the above method are shown in Table 4. A
sufficient adhesive force was observed.
[2696] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2697] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
[2698] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The roughened surface of the electrode was oppositely
disposed on a substantial center position of the carboxylic acid
layer side of the ion. exchange membrane A (size: 160 mm.times.160
mm), produced in [Method (i)] and equilibrated with a 0.1 N NaOH
aqueous solution, and allowed to adhere thereto via the surface
tension of the aqueous solution.
[2699] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did not come
off or was not displaced.
[2700] The above membrane-integrated electrode was sandwiched
between the anode cell and the cathode cell such that the surface
onto which the electrode was attached was allowed to face the
cathode chamber side. In the sectional structure, the collector,
the mattress, the nickel mesh feed conductor, the electrode, the
membrane, and the anode are arranged in the order mentioned from
the cathode chamber side to form a zero-gap structure.
[2701] The resulting electrode was subjected to electrolytic
evaluation. The results are shown in Table 4.
[2702] The electrode exhibited a low voltage, high current
efficiency, and a low common salt concentration in caustic soda.
The handling property was also good: "1". The membrane damage was
also evaluated as good: "0".
[2703] When the amount of coating after the electrolysis was
measured by fluorescent X-ray analysis (XRF), substantially 100% of
the coating remained on the roughened surface, and the coating on
the surface not roughened was reduced. This indicates that the
surface opposed to the membrane (roughened surface) contributes to
the electrolysis and the other surface not opposed to the membrane
can achieve satisfactory electrolytic performance when the amount
of coating is small or no coating is present.
Example 2-2
[2704] In Example 2-2, an electrolytic nickel foil having a gauge
thickness of 22 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
0.96 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 2-1, and the results are
shown in Table 4.
[2705] The thickness of the electrode was 29 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 7 82 m. The coating was formed also
on the surface not roughened.
[2706] A sufficient adhesive force was observed.
[2707] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2708] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0033 (kPas/m) under the
measurement condition 2.
[2709] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was also evaluated as good: "0".
[2710] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 2-3
[2711] In Example 2-3, an electrolytic nickel foil having a gauge
thickness or 30 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel platinum.
The arithmetic average roughness Ra of the roughened surface was
1.38 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 2-1, and the results are
shown in Table 4.
[2712] The thickness of the electrode was 38 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 8 .mu.m. The coating was formed
also on the surface not roughened.
[2713] A sufficient adhesive force was observed.
[2714] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2715] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2
[2716] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2717] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating small or no
coating is present.
Example 2-4
[2718] In Example 2-4, an electrolytic nickel foil having a gauge
thickness of 16 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to a roughening treatment means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.71
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. The opening ratio
was 75%. Except for the above described, evaluation was performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2719] The thickness of the electrode was 24 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 8 .mu.m.
[2720] A sufficient adhesive force was observed.
[2721] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2722] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[2723] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2724] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 2-5
[2725] In Example 2-5, an electrolytic nickel foil having a gauge
thickness of 20 .mu.m was provided as the substrate for electrode
for cathode electrolysis. Both the surface of this nickel foil was
subjected to a roughening treatment by means of electrolytic nickel
plating. The arithmetic average roughness Ra of the roughened
surface was 0.96 .mu.m. Both the surfaces had the same roughness.
The measurement of the surface roughness was performed under the
same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. The opening ratio
was 49%. Except for the above described, evaluation was performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2726] The thickness of the electrode was 30 .mu.m. The thickness
of the catalyst layer, which was determined by subtract ng the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m. The coating was formed
also on the surface not roughened.
[2727] A sufficient adhesive force was observed.
[2728] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2729] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[2730] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[2731] Additionally, when the amount of coating after the
electrolysis was measured by XRF, substantially 100% of the coating
remained on both the surfaces. In consideration of comparison with
Examples 2-1 to 2-4, this indicates that the other surface not
opposed to the membrane can achieve satisfactory electrolytic
performance when the amount of coating is small or no coating is
present.
Example 2-6
[2732] In Example 2-6, evaluation was performed in the same manner
as in Example 2-1 except that coating of the substrate for
electrode for cathode electrolysis was performed by ion plating,
and the results are shown in Table 4. In the ion plating, film
forming was performed using a heating temperature of 200.degree. C.
and Ru metal target under an argon/oxygen atmosphere at a film
forming pressure of 7.times.10.sup.2 Pa. The coating formed was
ruthenium oxide.
[2733] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2734] A sufficient adhesive force was observed.
[2735] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2736] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
[2737] Additionally, the electrode exhibited a low voltage, high
current efficiency and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-7
[2738] In Example 2-7, the substrate for electrode for cathode
electrolysis was produced by an eletroforming method. The photomask
ad a shape formed by vertically and horizontally arranging 0.485
mm.times.0.485 mm squares at an interval of 0.15 mm. Exposure,
development, and electroplating were sequentially performed to
obtain a nickel porous foil having a gauge thickness of 20 .mu.m
and an opening ratio of 56%. The arithmetic average roughness Ra of
the surface was 0.71 .mu.m. The measurement of the surface
roughness was performed under the same condition as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation was performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2739] The thickness of the electrode was 37 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 17 .mu.m.
[2740] A sufficient adhesive force was observed.
[2741] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2742] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[2743] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-8
[2744] In Example 2-8, the substrate for electrode for cathode
electrolysis was produced by an electroforming method. The
substrate had a gauge thickness of 50 .mu.m and an opening ratio of
56%. The arithmetic average roughness Ra of the surface was 0.73
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 2-1, and the results are shown in Table 4.
[2745] The thickness of the electrode was 60 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2746] A sufficient adhesive force was observed.
[2747] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2748] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[2749] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: The membrane damage was
also evaluated as good: "0".
Example 2-9
[2750] In Example 2-9, a nickel nonwoven fabric having a gauge
thickness of 150 .mu.m and a void ratio of 76% (manufactured NIKKO
TECHNO, Ltd.) was used as the substrate for electrode for cathode
electrolysis. The nonwoven fabric had a nickel fiber diameter of
about 40 .mu.m and a basis weight of 300 g/m.sup.2. Except for the
above described, evaluation was performed in the same manner as in
Example 2-1, and the results are shown in Table 4.
[2751] The thickness of the electrode was 165 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 15 .mu.m.
[2752] A sufficient adhesive force was observed.
[2753] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 29 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[2754] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0612 (kPas/m) under the
measurement condition 2.
[2755] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 2-10
[2756] In Example 2-10, a nickel nonwoven fabric having a gauge
thickness of 200 .mu.m and a void ratio of 72% (manufactured by
NIKKO TECHNO, Ltd.) was used as the substrate for electrode for
cathode electrolysis. The nonwoven fabric had a nickel fiber
diameter of about 40 .mu.m and a basis weight of 500 g/m.sup.2.
Except for the above described, evaluation was performed in the
same manner as in Example 2-1, and the results are shown in Table
4.
[2757] The thickness of the electrode was 215 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 15 .mu.m.
[2758] A sufficient adhesive force was observed.
[2759] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 40 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[2760] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0164 (kPas/m) under the
measurement condition 2
[2761] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 2-11
[2762] In Example 2-11, foamed nickel having a gauge thickness of
200 .mu.m and a void ratio of 72% (manufactured by Mitsubishi
Materials Corporation) was used as the substrate for electrode for
cathode electrolysis. Except for the above described, evaluation
was performed in the same manner as in Example 2-1, and the results
are shown in Table 4.
[2763] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2764] A sufficient adhesive force was observed.
[2765] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 17 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[2766] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0402 (kPas/m) under the
measurement condition 2.
[2767] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 2-12
[2768] In Example 2-12, a 200-mesh nickel mesh having a line
diameter of 50 .mu.m, a gauge thickness of 100 .mu.m, and an
opening ratio of 37% was used as the substrate for electrode for
cathode electrolysis. A blast treatment was performed with alumina
of grain-size number 320. The blast treatment did not change the
opening ratio. It is difficult to measure the roughness of the
surface of the metal net. Thus, in Example 2-12, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra of a wire piece of the
wire mesh was 0.64 .mu.m. The measurement of the surface roughness
was performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation was performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2769] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2770] A sufficient adhesive force was observed.
[2771] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2772] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0154 (kPas/m) under the
measurement condition 2.
[2773] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was evaluated as good: "0".
Example 2-13
[2774] In Example 2-13, a 150-mesh nickel mesh having a line
diameter of 65 .mu.m, a gauge thickness of 130 .mu.m, and an
opening ratio of 38% was used as the substrate for electrode for
cathode electrolysis. A blast treatment was performed with alumina
of grain-size number 320. The blast treatment did not change the
opening ratio. It is difficult to measure the roughness of the
surface of the metal net. Thus, in Example 2-13, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.66 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, the above evaluation was performed in the same manner as
in Example 2-1, and the results are shown in Table 4.
[2775] The thickness of the electrode was 133 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 3 .mu.m.
[2776] A sufficient adhesive force was observed.
[2777] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 6.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2778] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0124 (kPas/m) under the
measurement condition 2.
[2779] Additionally, the electrode exhibited a low voltage, nigh
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was also evaluated as good: "0".
Example 2-14
[2780] In Example 2-14, a substrate identical to that of Example
2-3 (gauge thickness of 30 .mu.m and opening ratio of 44%) was used
as the substrate for electrode for cathode electrolysis.
Electrolytic evaluation was performed with a structure identical to
that of Example 2-1 except that no nickel mesh feed conductor was
included. That is, in the sectional structure of the cell, the
collector, the mattress, the membrane-integrated electrode, and the
anode are arranged in the order mentioned from the cathode chamber
side to form a zero-gap structure, and the mattress serves as the
feed conductor. Except for the above described, evaluation was
performed in the same manner as in Example 2-1, and the results are
shown in Table 4.
[2781] A sufficient adhesive force was observed.
[2782] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2783] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[2784] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-15
[2785] In Example 2-15, a substrate identical to that of Example
2-3 (gauge thickness of 30 .mu.m and opening ratio of 44%) was used
as the substrate for electrode for cathode electrolysis. The
cathode used in Reference Example 1, which was degraded and had an
enhanced electrolytic voltage, was placed instead of the nickel
mesh feed conductor. Except for the above described, electrolytic
evaluation was performed with a structure identical to that of
Example 2-1. That is, in the sectional structure of the cell, the
collector, the mattress, the cathode that was degraded and had an
enhanced electrolytic voltage (serves as the feed conductor), the
electrode for electrolysis (cathode), the membrane, and the anode
are arranged in the order mentioned from the cathode chamber side
to form a zero-gap structure, and the cathode that is degraded and
has an enhanced electrolytic voltage serves as the feed conductor.
Except for the above described, evaluation was performed in the
same manner as in Example 2-1, and the results are shown in Table
4.
[2786] A sufficient adhesive force was observed.
[2787] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2788] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less,
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[2789] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-16
[2790] A titanium foil having a gauge thickness of 20 .mu.m was
provided as the substrate for electrode for anode electrolysis.
Both the surfaces of the titanium foil were subjected to a
roughening treatment. A porous foil was formed by perforating this
titanium toil with circular holes by punching. The hole diameter
was 1 mm, and the opening ratio was 14%. The arithmetic average
roughness Ra of the surface was 0.37 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment.
[2791] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[2792] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPM (INOAC
CORPORATION, E-4088, thickness 10 mm) around a polyvinyl chloride
(PVC) cylinder was always in contact with the coating liquid. A
coating roll around which the same EPDM had been wound was placed
at the upper portion thereof, and a PVC roller was further placed
thereabove. The coating liquid was applied b allowing the substrate
for electrode to pass between the second coating roll and the PVC
roller at the uppermost portion (roll coating method). After the
above coating liquid was applied onto the titanium porous foil,
drying at 60.degree. C. for 10 minutes and baking at 475.degree. C.
for 10 minutes were performed. A series of these coating, drying,
preliminary baking, and baking operations was repeatedly performed,
and then baking at 520.degree. C. was performed for an hour.
[2793] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The cut electrode was allowed to adhere via the surface
tension of the aqueous solution to a substantial center position of
the sulfonic acid layer side of the ion exchange membrane A (size:
160 mm.times.160 mm) produced in [Method (i)] and equilibrated with
a 0.1 N NaOH aqueous solution.
[2794] The cathode was prepared in the following procedure. First,
a 40-mesh nickel wire mesh having a line diameter of 150 .mu.m was
provided as the substrate. After blasted with alumina as
pretreatment, the wire mesh was immersed in 6 N hydrochloric acid
for 5 minutes, sufficiently washed with pure water, and dried.
[2795] Next, a ruthenium chloride solution having a ruthenium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.) and cerium
chloride (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the
molar ratio between the ruthenium element and the cerium element
was 1:0.25. This mixed solution was sufficiently stirred and used
as a cathode coating liquid.
[2796] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 300.degree. C. for 3 minutes, and
baking at 550.degree. C. for 10 minutes were performed. Thereafter,
baking at 550.degree. C. for an hour was performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated.
[2797] As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. The cathode
produced by the above method was placed thereover, and a string
made of Teflon(R) was used to fix the four corners of the mesh to
the collector.
[2798] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the anodes, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did riot come
off or was not displaced.
[2799] The anode used in Reference Example 3, which was degraded
and had an enhanced electrolytic voltage, was fixed to the anode
cell welding, and the above membrane-integrated electrode was
sandwiched between the anode cell and the cathode cell such that
the surface onto which the electrode was attached was allowed to
face the anode chamber side. That is, in the sectional structure of
the cell, the collector, the mattress, the cathode, the membrane,
the electrode for electrolysis (titanium porous foil anode), and
the anode that was degraded and had an enhanced electrolytic
voltage were arranged in the order mentioned from the cathode
chamber side to form a zero-gap structure. The anode that was
degraded and had an enhanced electrolytic voltage served as the
feed conductor. The titanium porous foil anode and the anode that
was degraded and had an enhanced electrolytic voltage were only in
physical contact with each other and were not fixed with each other
by welding.
[2800] Evaluation on this structure was performed in the same
manner as in Example 2-1, and the results are shown in Table 4.
[2801] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 6 .mu.m.
[2802] A sufficient adhesive force was observed.
[2803] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 4 mm. It was found that
the electrode had a broad elastic deformation region.
[2804] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition and 0.0060 (kPas/m) under the
measurement condition 2.
[2805] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-17
[2806] In Example 2-17%, a titanium foil having a gauge thickness
of 20 .mu.m and an opening ratio of 30% was used as the substrate
for electrode for anode electrolysis. The arithmetic average
roughness Ra of the surface was 0.37 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2807] The thickness of the electrode was 30 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2808] A sufficient adhesive force was observed.
[2809] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 5 mm. It was found that
the electrode had a broad elastic deformation region.
[2810] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
[2811] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: The membrane damage was
also evaluated as good: "0".
Example 2-18
[2812] In Example 2-18, a titanium foil having a gauge thickness of
20 .mu.m and an opening ratio of 42% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.38 .mu.m. The measurement of the surface
roughness was per formed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2813] The thickness of the electrode was 32 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 12 .mu.m.
[2814] A sufficient adhesive force was observed.
[2815] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2.5 mm. It was found that
the electrode had a broad elastic deformation region.
[2816] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0022 (kPas/m) under the
measurement condition 2.
[2817] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-19
[2818] In Example 2-19, a titanium foil having a gauge thickness of
50 .mu.m and an opening ratio of 47% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.40 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2819] The thickness of the electrode was 69 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 19 .mu.m.
[2820] A sufficient adhesive force was observed.
[2821] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 8 .mu.m. It was found that
the electrode had a broad elastic deformation region.
[2822] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0024 (kPas/m) under the
measurement condition 2.
[2823] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-20
[2824] In Example 2-20, a titanium nonwoven fabric having a gauge
thickness of 100 .mu.m, a titanium fiber diameter of about 20
.mu.m, a basis weight of 100 g/m.sup.2, and an opening ratio of 78%
was used as the substrate for electrode for anode electrolysis.
Except for the above described, evaluation was performed in the
same manner as in Example 2-16, and the results are shown in Table
4.
[2825] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[2826] A sufficient adhesive force was observed.
[2827] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2 mm. It was found that
the electrode had a broad elastic deformation region.
[2828] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0228 (kPas/m) under the
measurement condition 2.
[2829] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-21
[2830] In Example 2-21, a 150-mesh titanium wire mesh having a
gauge thickness of 120 .mu.m and a titanium fiber diameter of about
60 .mu.m was used as the substrate for electrode for anode
electrolysis. The opening ratio was 42%. A blast treatment was
performed with alumina of grain-size number 320. It is difficult to
measure the roughness of the surface of the metal net. Thus, in
Example 2-21, a titanium plate having a thickness of 1 mm was
simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the titanium plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.60 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2831] The thickness of the electrode was 140 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 20 .mu.m.
[2832] A sufficient adhesive force was observed.
[2833] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 10 mm. It was found that
the electrode had a broad elastic deformation region.
[2834] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0132 (kPas/m) under the
measurement condition 2.
[2835] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 2-22
[2836] In Example 2-22, an anode that was degraded and had an
enhanced electrolytic voltage was used in the same manner as in
Example 2-16 as the anode feed conductor, and a titanium nonwoven
fabric identical to that of Example 2-20 was used as the anode. A
cathode that was degraded and had an enhanced electrolytic voltage
was used in the same manner as in Example 2-15 as the cathode feed
conductor, and a nickel foil electrode identical to that of Example
2-3 was used as the cathode. In the sectional structure of the
cell, the collector, the mattress, the cathode that was degraded
and had an enhanced voltage, the nickel porous foil cathode, the
membrane, the titanium nonwoven fabric anode, and the anode that
was degraded and had an enhanced electrolytic voltage are arranged
in the order mentioned from the cathode chamber side to form a
zero-gap structure, and the cathode and anode degraded and having
an enhanced electrolytic voltage serve as the feed conductor.
Except for the above described, evaluation was performed in the
same manner as in Example 2-1, and the results are shown in Table
4.
[2837] The thickness of the electrode (anode) was 114 .mu.m, and
the thickness the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode (anode), was 14
.mu.m. The thickness of the electrode (cathode) was 38 .mu.m, and
the thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode (cathode), was 8
.mu.m.
[2838] A sufficient adhesive force was observed both in the anode
and the cathode.
[2839] When a deformation test of the electrode (anode) was
performed, the average value of L.sub.1 and L.sub.2 was 2 mm. When
a deformation test of the electrode (cathode) was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm.
[2840] When the ventilation resistance of the electrode (anode) was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition and 0.0228 (kPas/m) under the
measurement condition 2. When the ventilation resistance of the
electrode (cathode) was measured, the ventilation resistance was
0.07 (kPas/m) or less under the measurement condition 1 and 0.0027
(kPas/m) under the measurement condition 2.
[2841] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0" both in the anode and the cathode.
In Example 2-22, the cathode and the anodes were combined by
attaching the cathode to one surface of the membrane and the anode
o the other surface and subjected to the membrane damage
evaluation.
Example 2-23
[2842] In Example 2-23, a microporous membrane "Zirfon Perl UTP
500" manufactured by Agfa was used.
[2843] The Zirfon membrane was immersed in pure water for 12 hours
or more and used for the test. Except for the above described, the
above evaluation was performed in the same manner as in Example
2-3, and the results are shown in Table 4.
[2844] When a deformation test the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[2845] Similarly to the case where an ion exchange membrane was
used as the membrane, a sufficient adhesive force was observed. The
microporous membrane was brought into a close contact with the
electrode via the surface tension, and the handling property was
good: "1".
Example 2-24
[2846] A carbon cloth obtained by weaving a carbon fiber having a
gauge thickness of 566 .mu.m was provided as substrate for
electrode for cathode electrolysis coating liquid for use in
forming an electrode catalyst on this carbon cloth was prepared by
the following procedure. A ruthenium nitrate solution having a
ruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and
cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that
the molar ratio between the ruthenium element and the cerium
element was 1:0.25. This mixed solution was sufficiently stirred
and used as a cathode coating liquid.
[2847] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088 (trade name), thickness 10 mm) around a
chloride (PVC) cylinder was always in contact with the above
coating liquid. A coating roll around which the same EPDM had been
wound was laced at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coatrig, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced was 570 .mu.m. The
thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode, was 4 .mu.m. The
thickness of the catalytic layer was the total thickness of
ruthenium oxide and cerium oxide.
[2848] The resulting electrode was subjected to electrolytic
evaluation. The results are shown in Table 4.
[2849] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm.
[2850] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.19 (kPas/m) under the
measurement condition 1 and 0.176 (kPas/m) under the measurement
condition 2.
[2851] The electrode had a handling property of "2" and was
determined to be handleable as a large laminate.
[2852] The voltage was high, the membrane damage was evaluated as
"1", and membrane damage was observed. It was conceived that this
is because NaOH that had been generated in the electrode
accumulated on the interface between the electrode and the membrane
to elevate the concentration thereof, due to the high ventilation
resistance of the electrode of Example 2-24.
Reference Example 1
[2853] In Reference Example 1, used was a cathode used as the
cathode in a large electrolyzer for eight years, degraded, and
having an enhanced electrolytic voltage. The above cathode was
placed instead of the nickel mesh feed conductor on the mattress of
the cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In Reference Example 1, no
membrane-integrated electrode was used. In the sectional structure
of the cell, the collector, the mattress, the cathode that was
degraded and had an enhanced electrolytic voltage, the ion exchange
membrane A, and the anodes were arranged in the order mentioned
from the cathode chamber side to form a zero-gap structure,
[2854] As a result of the electrolytic evaluation that with this
structure, the voltage was 3.04 V, the current efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 20 ppm. Consequently, due to
degradation of the cathode, the voltage was high.
Reference Example 2
[2855] In Reference Example 2, a nickel mesh feed conductor was
used as the cathode. That electrolysis was performed on nickel mesh
having no catalyst coating thereon.
[2856] The nickel mesh cathode was placed on the mattress of the
cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In the sectional structure of the
electric cell of Reference Example 2, the collector, the mattress,
the nickel mesh, the ion exchange membrane A, and the anodes were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[2857] As a result of the electrolytic evaluation with this
structure, the voltage was 3.38 V, the current efficiency was
97.7%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was ppm. Consequently, the voltage
was high because the cathode catalyst had no coating.
Reference Example 3
[2858] In Reference Example 3, used was an anode used as the anode
in a large electrolyzer for about eight years, degraded, and having
an enhanced electrolytic voltage.
[2859] In the sectional structure of the electrolytic cell of
Reference Example 3, the collector, the mattress, the cathode, the
ion exchange membrane A produced in [Method (i)], and the anode
that was degraded and had an enhanced electrolytic voltage were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[2860] As a result of the electrolytic evaluation with this
structure, the voltage was 3.18 V, the current efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 22 ppm. Consequently, due to
degradation of the anode, the voltage was high.
Example 2-25
[2861] In Example 2-25, a fully-rolled nickel expanding metal
having a gauge thickness of 100 .mu.m and an opening ratio of 33%
was used as the substrate for electrode for cathode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 2-25, a nickel plate having a thickness of
1 mm was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.68 .mu.m. The measurement of the surface
roughness m performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation was performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2862] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[2863] The mass per unit area was 67.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.05
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was 64%, and the result of
evaluation of winding around column of 145 mm in diameter (3) was
22%. The portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[2864] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[2865] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Example 2-26
[2866] In Example 2-26, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 16% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 2-26, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.64 .mu.m. The measurement of the surface
roughness m performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation as performed
in the same manner as in Example 2-1, and the results are shown in
Table 4.
[2867] The thickness of the electrode was 107 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 7 .mu.m.
[2868] The mass per unit area was 78.1 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.04
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was 37%, and the result of
evaluation of winding around column of 145 mm in diameter (3) was
25%. The portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[2869] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 18.5 mm.
[2870] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0176 (kPas/m) under the
measurement condition 2.
Example 2-27
[2871] In Example 2-27, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 40% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not chanced after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 2-27, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.70 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Coating of the substrate for electrode for
electrolysis was performed by ion plating in the same manner as in
Example 2-6. Except for the above described, evaluation was
performed in the same manner as in Example 2-1, and the results are
shown in Table 4.
[2872] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2873] The force applied per unit massunit area (1) was such a
small value as 0.07 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter (2) was 80%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 32%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[2874] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11 mm.
[2875] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
Example 2-28
[2876] In Example 2-28, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 58% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 2-28, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.64 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-1, and the results are
shown in Table 4.
[2877] The thickness of the electrode was 109 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 9 .mu.m.
[2878] The force applied per unit massunit area (1) was such a
small value as 0.06 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter (2) was 69%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 39%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[2879] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11.5 mm.
[2880] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
Example 2-29
[2881] In Example 2-29, a nickel wire mesh having a gauge thickness
of 300 .mu.m and an opening ratio of 56% was used as the substrate
for electrode for cathode electrolysis. It is difficult to measure
the surface roughness of the wire mesh. Thus, in Example 2-29, a
nickel plate having a thickness of 1 mm was simultaneously
subjected to the blast treatment during the blasting, and the
surface roughness of the nickel plate was taken as the surface
roughness of the wire mesh. A blast treatment was performed with
alumina of grain-size number 320. The opening ratio was not changed
after the blast treatment. The arithmetic average roughness Ra was
0.64 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. Except for
the above described, evaluation was performed in the same mariner
as in Example 2-1, and the results are shown in Table 4.
[2882] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2883] The mass per unit area was 49.2 (mg/cm.sup.2). Thus, the
result of evaluation of winding around column of 280 mm in diameter
(2) was 88%, and the result of evaluation of winding around column
of 145 mm in diameter (3) was 42%. The portions at which the
electrode came off from the membrane increased. This is because the
electrode was likely to come off when the membrane-integrated
electrode is handled and the electrode may come off and fall from
the membrane during handled. There was a problem in the handling
property, which was evaluated as "3". When the large size electrode
was actually operated, it was possible to evaluate the handling
property as "3". The membrane damage was evaluated as "0".
[2884] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[2885] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
Example 2-30
[2886] In Example 2-30, a nickel wire mesh having a gauge thickness
of 200 .mu.m and an opening ratio of 37% was used as the substrate
for electrode for cathode electrolysis. A blast treatment was
performed with alumina of grain-size number 320. The opening ratio
was not changed after the blast treatment. It is difficult to
measure the surface roughness of the wire mesh. Thus, in Example
2-30, a nickel plate having a thickness of 1 mm was simultaneously
subjected to the blast treatment during the blasting, and the
surface roughness of the nickel plate was taken as the surface
roughness of the wire mesh. The arithmetic average roughness Ra was
0.65 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. Except for
the above described, evaluation of electrode electrolysis,
measurement results of the adhesive force, and adhesiveness were
performed in the same manner as in Example 2-1. The results are
shown in Table 4.
[2887] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[2888] The mass per unit area was 56.4 mg/cm.sup.2. Thus, the
result of evaluation method of winding around column of 145 mm in
diameter (3) was 63%, and the adhesiveness between the electrode
and the membrane was poor. This is because the electrode was likely
to come off when the membrane-integrated electrode is handled and
the electrode may come off and fall from the membrane during
handled. There was a problem in the hand ting property, which was
evaluated as "3". The membrane damage was evaluated as "0".
[2889] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 19 mm.
[2890] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0096 (kPas/m) under the
measurement condition 2.
Example 2-31
[2891] In Example 2-31, a full-roiled titanium expanded metal
having a gauge thickness of 500 .mu.m and an opening ratio of 17%
was used as the substrate for electrode for anode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 2-31 a titanium plate having a thickness of
1 mm was simultaneously subjected to the blast treatment during the
blast ng, and the surface roughness of the titanium plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.60 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2892] The thickness of the electrode was 508 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2893] The mass per unit area was 152.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 .mu.m in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2894] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2895] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0072 (kPas/m) under the
measurement condition 2.
Example 2-32
[2896] In Example 2-32, a full-rolled titanium expanded metal
having a gauge thickness having 800 .mu.m and an opening, ratio or
8% was used as the substrate for electrode for anode electrolysis.
A blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 2-32, a titanium plate having a thickness
of 1 mm was simultaneously subjected to the blast treatment during
the blasting, and the surface roughness of the titanium plate was
taken as the surface roughness or the wire mesh. The arithmetic
average roughness Ra was 0.61 .mu.m. The measurement of the surface
roughness m performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, the above evaluation was
performed in the same manner as in Example 2-16, and the results
are shown in Table 4.
[2897] The thickness of the electrode was 808 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2898] The mass per unit area was 251.3 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2899] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2900] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0172 (kPas/m) under the
measurement condition 2.
Example 2-33
[2901] In Example 2-33, a full-rolled titanium expanded metal
having a gauge thickness of 1000 .mu.m and an opening ratio of 46%
was used as the substrate for electrode for anode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 2-33, a titanium plate having a thickness
of 1 mm was simultaneously subjected to the blast treatment during
the blasting, and the surface roughness of the titanium plate was
taken as the surface roughness of the wire mesh. The arithmetic
average roughness Ra was 0.59 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, the above
evaluation was performed in the same manner as in Example 2-16, and
the results are shown in Table 4.
[2902] The thickness of the electrode was 1011 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 11 .mu.m.
[2903] The mass per unit area was 245.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[2904] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[2905] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
Example 2-34
[2906] A nickel line having a gauge thickness of 150 .mu.m was
provided as the substrate for electrode for cathode electrolysis. A
roughening treatment by this nickel line was performed. It is
difficult to measure the surface roughness of the nickel line.
Thus, in Example 2-34, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the nickel line. A blast treatment was
performed with alumina of grain-size number 320. The arithmetic
average roughness Ra was 0.64 .mu.m.
[2907] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[2908] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088 (trade name), thickness 10 mm) around a
polyvinyl chloride (PVC) cylinder was always in contact with the
above coating liquid. A coating roll around which the same EPDM had
been wound was placed at the upper portion thereof, and a PVC
roller was further placed thereabove. The coating liquid was
applied by allowing the substrate for electrode to pass between the
second coating roll and the PVC roller at the uppermost portion
(roll coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of one nickel line produced in Example 2-34 was 158
.mu.m.
[2909] The nickel line produced by the above method was cut into a
length of 110 mm and a length of 95 mm. As shown in FIG. 37, the
110 mm nickel line and the 95 mm nickel line were placed such that
the nickel lines vertically overlapped each other at the center of
each of the nickel lines and bonded to each other at the
intersection with an instant adhesive (Aron Alpha(R), TOAGOSEI CO.,
LTD.) to produce an electrode. The electrode was evaluated, and the
results are shown in Table 4.
[2910] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.7%.
[2911] The mass per unit area of the electrode was 0.5 (1). The
forces applied per unit ma unit area (1) and (2) were both equal to
or less than the measurement lower limit of the tensile testing
machine. Thus, the result of evaluation of winding around column of
280 mm in diameter (1) was less than 5%, and the portions at which
the electrode came off from the membrane increased. The handling
property was "4", which was also problematic. The membrane damage
was evaluated as "0".
[2912] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 15 mm.
[2913] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance value was 0.0002 (kPas/m).
[2914] Additionally, the structure shown in FIG. 38 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.16 V.
Example 2-35
[2915] In Example 2-35, the electrode produced in Example 2-34 was
used. As shown in FIG. 39, the 110 mm nickel line and the 95 mm
nickel line were placed such that the nickel lines vertically
overlapped each other at the center of each of the nickel lines and
bonded to each other at the intersection with an instant adhesive
(Aron Alpha(R), TOAGOSEI CO., LTD.) to produce an electrode. The
electrode was evaluated, and the results are shown in Table 4.
[2916] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.4%.
[2917] The mass per unit area of the electrode was 0.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[2918] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 16 mm.
[2919] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0004 (kPas/m).
[2920] Additionally, the structure shown in FIG. 40 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
Example 2-36
[2921] In Example 2-36, the electrode produced in Example 2-34 was
used. As shown in FIG. 41, the 110 mm nickel line and the 95 mm
nickel line were placed such that the nickel lines vertically
overlapped each other at the center of each of the nickel lines and
bonded to each other at the intersection with an instant adhesive
(Aron Alpha(R), TOAGOSEI CO., LTD.) to produce an electrode. The
electrode was evaluated, and the results are shown in Table 4.
[2922] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 98.8%.
[2923] The mass per unit area of the electrode was 1.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[2924] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 14 mm.
[2925] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0005 (kPas/m).
[2926] Additionally, the structure shown in FIG. 42 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
Comparative Example 2-1
[2927] In Comparative Example 2-1, a thermal compressed assembly
was produced by thermally compressing an electrode onto a membrane
with reference to a prior art document (Examples of Japanese Patent
Laid-Open No. 58-48686).
[2928] A nickel expanded metal having a gauge thickness of 100
.mu.m and an opening ratio of 33% was used as the substrate for
electrode for cathode electrolysis to perform electrode coating in
the same manner as in Example 2-1. Thereafter, one surface of the
electrode was subjected to an inactivation treatment in the
following procedure. Polyimide adhesive ape (Chukoh Chemical
Industries, Ltd.) was attached to one surface of the electrode. A
PTFE dispersion (Dupont-Mitsui Fluorochemicals Co., Ltd., 31-JR
(trade name) was applied onto the other surface and dried in a
muffle furnace at 120.degree. C. for 10 minutes. The polyimide tape
was peeled off, and a sintering treatment was performed in a muffle
furnace set at 380.degree. C. for 10 minutes. This operation was
repeated twice to inactivate the one surface of the electrode.
[2929] Produced was a membrane formed by two layers of a
perfluorocarbon polymer of which terminal functional group is
"--COOCH.sub.3" polymer) and a perfluorocarbon polymer of which
terminal functional group is "--SO.sub.2F" (S polymer). The
thickness of the C polymer layer was 3 mils, and the thickness of
the S polymer layer was 4 mils. This two-layer membrane was
subjected to a saponification treatment to thereby introduce ion
exchange groups to the terminals of the polymer by hydrolysis. The
C polymer terminals were hydrolyzed into carboxylic groups and the
S polymer terminals into sulfo groups. The ion exchange capacity as
the sulfonic acid group was 1.0 meq/g, and the ion exchange
capacity as the carboxylic acid group was 0.9 meq/g.
[2930] The inactivated electrode surface was oppositely disposed to
and thermally pressed onto the surface having carboxylic acid
groups as the ion exchange groups to integrate the ion exchange
membrane and the electrode. The one surface of the electrode was
exposed even after the thermal compression, and the electrode
passed through no portion of the membrane.
[2931] Thereafter, in order to suppress attachment of bubbles to be
generated during electrolysis to the membrane, a mixture of
zirconium oxide and a perfluorocarbon polymer into which sulfo
groups had been introduced was applied onto both the surfaces.
Thus, the thermal compressed assembly of Comparative Example 2-1
was produced.
[2932] When the force applied per unit massunit area (1) was
measured using this thermal compressed assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.50 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The thermal compressed assembly of Comparative Example
2-1 had a force applied per unit massunit area (1) of at least 1.50
(N/mgcm.sup.2) and was strongly bonded.
[2933] When evaluation of winding around column of 280 mm in
diameter (1) was performed, the area in contact with the plastic
pipe was less than 5%. Meanwhile, when evaluation of winding around
column of 280 mm in diameter (2) was performed, the electrode and
the membrane were 100% bonded to each other, but the membrane was
not wound around the column in the first place. The result of
evaluation of winding around column of 145 mm in diameter (3) was
the same. The result meant that the integrated electrode impaired
the handling property of the membrane to thereby make it difficult
to roll the membrane into a roll and fold the membrane. The
handling property was "3", which was problematic. The membrane
damage was evaluated as "0". Additionally, when electrolytic
evaluation was performed, the voltage was high, the current
efficiency was low, the common salt concentration in caustic soda
(value converted on the basis of 50%) was raised, and the
electrolytic performance deteriorated.
[2934] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[2935] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[2936] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Comparative Example 2-2
[2937] In Comparative Example 2-2, a 40-mesh nickel mesh having a
line diameter of 150 .mu.m, a gauge thickness of 300 .mu.m, and an
opening ratio of 58% was used as the substrate for electrode for
cathode electrolysis. Except for the above described, a thermal
compressed assembly was produced in the same manner as in
Comparative Example 2-1.
[2938] When the force applied per unit massunit area (1) was
measured using this thermal compressed assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.60 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The thermal compressed assembly of Comparative Example
2-2 had a force applied per unit massunit area (1) of at least 1.60
(N/mgcm.sup.2) and was strongly bonded.
[2939] When evaluation of winding around column of 280 mm in
diameter (1) was performed using this thermal compressed assembly,
the contact area with the plastic pipe was less than 5%. Meanwhile,
when evaluation of pipe was around column of 280 mm in diameter (2)
was performed, the electrode and the membrane were 100% bonded to
each other, but the membrane was not wound around the column in the
first place. The result of evaluation of winding around column of
145 mm (3) was the same. The result meant that the integrated
electrode impaired the handling property of the membrane to thereby
make it difficult to roll the membrane into a roll and fold the
membrane. The handling property was "3", which was problematic.
Additionally, when electrolytic evaluation was performed, the
voltage was high, the current efficiency was low, the common salt
concentration in caustic soda was raised, and the electrolytic
performance deteriorated.
[2940] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[2941] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[2942] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
TABLE-US-00003 TABLE 3 Substrate for Form of substrate Coating
electrode for electrode method Feed conductor Example 2-1 Ni
Punching Pyrolysis Ni mesh Example 2-2 Ni Punching Pyrolysis Ni
mesh Example 2-3 Ni Punching Pyrolysis Ni mesh Example 2-4 Ni
Punching Pyrolysis Ni mesh Example 2-5 Ni Punching Pyrolysis Ni
mesh Example 2-6 Ni Punching Ion plating Ni mesh Example 2-7 Ni
Electroforming Pyrolysis Ni mesh Example 2-8 Ni Electroforming
Pyrolysis Ni mesh Example 2-9 Ni Nonwoven fabric Pyrolysis Ni mesh
Example 2-10 Ni Nonwoven fabric Pyrolysis Ni mesh Example 2-11 Ni
Foamed Ni Pyrolysis Ni mesh Example 2-12 Ni Mesh Pyrolysis Ni mesh
Example 2-13 Ni Mesh Pyrolysis Ni mesh Example 2-14 Ni Punching
(same Pyrolysis Mattress as in Example 2-3) Example 2-15 Ni
Punching (same Pyrolysis Cathode having increase in voltage as in
Example 2-3) Example 2-16 Ti Punching Pyrolysis Anode having
increase in voltage Example 2-17 Ti Punching Pyrolysis Anode having
increase in voltage Example 2-18 Ti Punching Pyrolysis Anode having
increase in voltage Example 2-19 Ti Punching Pyrolysis Anode having
increase in voltage Example 2-20 Ti Nonwoven fabric Pyrolysis Anode
having increase in voltage Example 2-21 Ti Mesh Pyrolysis Anode
having increase in voltage Example 2-22 Ni/Ti Combination of
Pyrolysis Cathode and anode having increase in voltage Example 2-3
and Example 2-20 Example 2-23 Ni Punching Pyrolysis -- Example 2-24
Carbon Woven fabric Pyrolysis Ni mesh Example 2-25 Ni Expanded
Pyrolysis Ni mesh Example 2-26 Ni Expanded Pyrolysis Ni mesh
Example 2-27 Ni Expanded Ion plating Ni mesh Example 2-28 Ni
Expanded Pyrolysis Ni mesh Example 2-29 Ni Mesh Pyrolysis Ni mesh
Example 2-30 Ni Mesh Pyrolysis Ni mesh Example 2-31 Ti Expanded
Pyrolysis Anode having increase in voltage Example 2-32 Ti Expanded
Pyrolysis Anode having increase in voltage Example 2-33 Ti Expanded
Pyrolysis Anode having increase in voltage Example 2-34 Ni Mesh
Pyrolysis Ni mesh Example 2-35 Ni Mesh Pyrolysis Ni mesh Example
2-36 Ni Mesh Pyrolysis Ni mesh Comparative Ni Expanded Pyrolysis Ni
mesh Example 2-1 Comparative Ni Mesh Pyrolysis Ni mesh Example
2-2
TABLE-US-00004 TABLE 4 Thickness of substrate for electrode for
Thickness of Thickness Mass per Force applied per unit electrolysis
electrode of catalytic Opening ratio unit area mass unit area (1)
(.mu.m) (.mu.m) layer (.mu.m) (void ratio) % (mg/cm.sup.2) (N/mg
cm.sup.2-electrode) Example 2-1 16 24 8 49 5.8 0.90 Example 2-2 22
29 7 44 9.9 0.61 Example 2-3 30 38 8 44 11.1 0.43 Example 2-4 16 24
8 75 3.5 0.28 Example 2-5 20 30 10 49 6.4 0.59 Example 2-6 16 26 10
49 6.2 0.81 Example 2-7 20 37 17 56 8.1 0.79 Example 2-8 50 60 10
56 18.1 0.13 Example 2-9 150 165 15 76 31.9 0.22 Example 2-10 200
215 15 72 46.3 0.12 Example 2-11 200 210 10 72 36.5 0.13 Example
2-12 100 110 10 37 27.4 0.18 Example 2-13 130 133 3 38 36.3 0.15
Example 2-14 30 38 8 44 11.1 0.43 Example 2-15 30 38 8 44 11.1 0.43
Example 2-16 20 26 6 14 8.9 0.16 Example 2-17 20 30 10 30 8.1 0.26
Example 2-18 20 32 12 42 6.6 0.24 Example 2-19 50 69 19 47 12.9
0.12 Example 2-20 100 114 14 78 11.3 0.59 Example 2-21 120 140 20
42 14.9 0.47 Example 2-22 30/100 38/114 8/14 44/78 11.1/11.3
0.43/0.59 Example 2-23 30 38 8 44 11.1 0.28 Example 2-24 586 570 4
83 21.8 0.270 Example 2-25 100 114 14 33 67.5 0.05 Example 2-26 100
107 7 16 78.1 0.04 Example 2-27 100 110 10 40 37.8 0.07 Example
2-28 100 109 9 58 39.2 0.06 Example 2-29 300 308 8 56 49.2 0.18
Example 2-30 200 210 10 37 56.4 0.09 Example 2-31 500 508 8 17
152.5 0.01 Example 2-32 800 808 8 8 251.3 0.01 Example 2-33 1000
1011 11 46 245.5 0.01 Example 2-34 300 306 6 99.7 0.5 Equal to or
less than the measurement lower limit Example 2-35 300 306 6 99.4
0.9 Equal to or less than the measurement lower limit Example 2-36
300 306 6 98.8 1.9 Equal to or less than the measurement lower
limit Comparative Example 2-1 100 114 14 33 67.5 1.50 Comparative
Example 2-2 300 308 8 58 49.2 1.60 Method for Method for Method for
evaluating evaluating evaluating winding winding winding around
around around column of column of column of 280 mm in 145 mm in 280
mm in diameter (2) diameter (3) diameter (1) (membrane (membrane
Handing Force applied per unit (membrane and and property mass unit
area (2) and column) electrode) electrode) (sensory (N/mg
cm.sup.2-electrode) (%) (%) (%) evaluation) Example 2-1 0.640 100
100 100 1 Example 2-2 0.235 100 100 100 1 Example 2-3 0.194 100 100
100 1 Example 2-4 0.113 100 100 100 1 Example 2-5 0.386 100 100 100
1 Example 2-6 0.650 100 100 100 1 Example 2-7 0.184 100 100 100 1
Example 2-8 0.088 100 100 100 1 Example 2-9 0.217 100 100 100 2
Example 2-10 0.081 100 100 79 2 Example 2-11 0.162 100 100 100 2
Example 2-12 0.126 100 100 100 1 Example 2-13 0.098 100 100 88 2
Example 2-14 0.194 100 100 100 1 Example 2-15 0.194 100 100 100 1
Example 2-16 0.105 100 100 100 1 Example 2-17 0.132 100 100 100 1
Example 2-18 0.147 100 100 100 1 Example 2-19 0.08 100 100 100 1
Example 2-20 0.378 100 100 100 1 Example 2-21 0.306 100 100 100 1
Example 2-22 0.194/0.378 100/100 100/100 100/100 1/1 Example 2-23
0.194 100 100 100 1 Example 2-24 0.3 100 100 100 2 Example 2-25
0.045 100 64 22 4 Example 2-26 0.027 100 37 25 4 Example 2-27 0.045
100 80 32 3 Example 2-28 0.034 100 69 39 3 Example 2-29 0.138 100
88 42 3 Example 2-30 0.060 100 100 63 3 Example 2-31 0.005 100 Less
than 5 Less than 5 4 Example 2-32 0.006 100 Less than 5 Less than 5
4 Example 2-33 0.005 100 Less than 5 Less than 5 4 Example 2-34
Equal to or less than the Less than 5 -- -- 4 measurement lower
limit Example 2-35 Equal to or less than the Less than 5 -- -- 4
measurement lower limit Example 2-36 Equal to or less than the Less
than 5 -- -- 4 measurement lower limit Comparative Example 2-1 --
Less than 5 -- -- 3 Comparative Example 2-2 -- Less than 5 -- -- 3
Elastic deformation test of electrode Electrolytic evaluation
(winding around Common salt vinyl chloride Ventilation Ventilation
concentration pipe of 32 mm in resistance resistance Current in
caustic soda outer diameter) (KPa s/m) (KPa s/m) Membrane Voltage
efficiency (ppm, on the average value of (measurement (measurement
damage (V) (%) basis of 50%) L.sub.1 and L.sub.2 (mm) condition 1)
condition 2) evaluation Example 2-1 2.98 97.7 15 0 0.07 or less
0.0028 0 Example 2-2 2.95 97.2 18 0 0.07 or less 0.0033 0 Example
2-3 2.96 97.6 19 0 0.07 or less 0.0027 0 Example 2-4 2.97 97.5 15 0
0.07 or less 0.0023 0 Example 2-5 2.95 97.1 18 0 0.07 or less
0.0023 0 Example 2-6 2.96 97.3 14 0 0.07 or less 0.0028 0 Example
2-7 2.96 97.3 15 0 0.07 or less 0.0032 0 Example 2-8 2.96 97.7 16 0
0.07 or less 0.0032 0 Example 2-9 2.97 96.8 23 29 0.07 or less
0.0612 0 Example 2-10 2.96 96.7 26 40 0.07 or less 0.0164 0 Example
2-11 3.05 97.4 22 17 0.07 or less 0.0402 0 Example 2-12 3.11 97.2
23 0.5 0.07 or less 0.0154 0 Example 2-13 3.09 97.0 25 6.5 0.07 or
less 0.0124 0 Example 2-14 2.97 97.3 18 0 0.07 or less 0.0027 0
Example 2-15 2.96 97.2 21 0 0.07 or less 0.0027 0 Example 2-16 3.10
96.8 19 4 0.07 or less 0.0060 0 Example 2-17 3.07 96.8 26 5 0.07 or
less 0.0030 0 Example 2-18 3.08 97.7 21 2.5 0.07 or less 0.0022 0
Example 2-19 3.09 97.0 21 8 0.07 or less 0.0024 0 Example 2-20 2.97
96.8 24 2 0.07 or less 0.0228 0 Example 2-21 2.99 97.0 18 10 0.07
or less 0.0132 0 Example 2-22 3.00 97.2 17 0/2 0.07 or less
0.0027/0.0228 0 Example 2-23 -- -- -- 0 0.07 or less 0.0027 --
Example 2-24 3.19 97.0 20 0 0.19 0.176 1 Example 2-25 2.98 97.7 19
13 0.07 or less 0.0168 0 Example 2-26 2.99 97.8 17 18.5 0.07 or
less 0.0176 0 Example 2-27 2.96 97.5 18 11 0.07 or less 0.0030 0
Example 2-28 2.99 97.6 18 11.5 0.07 or less 0.0028 0 Example 2-29
2.95 97.5 24 23 0.07 or less 0.0034 0 Example 2-30 2.98 97.3 23 19
0.07 or less 0.0096 0 Example 2-31 2.99 96.7 23 Remained 0.07 or
less 0.0072 0 Example 2-32 3.02 97.0 19 deformed in vinyl 0.07 or
less 0.0172 0 Example 2-33 3.00 97.2 20 chloride form and 0.07 or
less 0.0027 0 did not return Example 2-34 3.16 97.5 21 15 0.07 or
less 0.0002 0 Example 2-35 3.18 97.4 19 16 0.07 or less 0.0004 0
Example 2-36 3.18 97.3 20 14 0.07 or less 0.0005 0 Comparative
Example 2-1 3.67 93.8 226 13 0.07 or less 0.0168 0 Comparative
Example 2-2 3.71 94.5 155 23 0.07 or less 0.0034 0
[2943] In Table 4, all the samples were able to stand by themselves
by the surface tension before measurement of "force applied per
unit massunit area (1)" and "force applied per unit massunit area
(2)" (i.e., did not slip down).
<Verification of Third Embodiment>
[2944] As will be described below, Experiment Examples according to
the third embodiment (in the section of <Verification of third
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the third embodiment (in the
section of <Verification of third embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 57 to 62 as appropriate.
(1) Electrolytic Evaluation (Voltage (V), Current Efficiency
(?))
[2945] The electrolytic performance was evaluated by the following
electrolytic experiment.
[2946] A titanium anode cell having an anode chamber in which an
anode was provided (anode terminal cell) and a cathode cell having
a nickel cathode chamber in which a cathode was provided (cathode
terminal cell) were oppositely disposed. A pair of gaskets was
arranged between the cells, and an ion exchange membrane was
sandwiched between the gaskets. Then, the anode cell, the gasket,
the ion exchange membrane, the gasket, and the cathode were brought
into close contact together to obtain an electrolytic cell.
[2947] The anode was produced by applying a mixed solution of
ruthenium chloride, iridium chloride, and titanium tetrachloride
onto a titanium substrate subjected to blasting and acid etching
treatment as the pretreatment, followed by drying and baking. The
anode was fixed in the anode chamber by welding. As the cathode,
one described in each of Examples and Comparative Examples was
used. As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. Nickel mesh formed
by plain-weaving nickel wire having a diameter of 150 .mu.m in a
sieve mesh size of 40 was placed thereover, and a string made of
Teflon(R) was used to fix the four corners of the Ni mesh to the
collector. This Ni mesh was used as a feed conductor. In this
electrolytic cell, the repulsive force of the mattress as the metal
elastic body was used so as to achieve a zero-gap structure. As the
gaskets, ethylene propylene diene (EPDM) rubber gaskets were used.
As the membrane, an ion exchange membrane below was used.
[2948] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluorinethylene (PTEF) were used (hereinafter
referred to as PTFE yarns). As the sacrifice yarns, yarns obtained
by twisting six 3.5 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used. First, in each of the ID and the MD,
the PTFE yarns and the sacrifice yarns re plain-woven with 24 PTFE
yarns/inch so that two sacrifice yarns were arranged between
adjacent PTFE yarns, to obtain a woven fabric. The resulting woven
fabric was pressure-bonded by a roll to obtain a woven fabric
having a thickness of 70 .mu.m.
[2949] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin B of a dry resin that was a copolymer of CF.sub.2.dbd.F.sub.2
and CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)OCF.sub.2CF.sub.2SO.sub.2F
and had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[2950] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[2951] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[2952] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for 1 hour to replace the counterion of the
ion exchange group by Na, and then washed with water. Further, the
membrane was dried at 60.degree. C.
[2953] Further, 20% by mass of zirconium oxide having an average
particle size (primary particle size) of 1 .mu.m was added to a 5%
by mass ethanol solution of the acid-type resin of the resin B and
dispersed to prepare a suspension, and the suspension was sprayed
onto both the surfaces of the above composite membrane by a
suspension spray method to form coatings of zirconium oxide on the
surfaces of the composite membrane to obtain an ion exchange
membrane. The coating density of zirconium oxide measured by
fluorescent X-ray measurement was 0.5 mg/cm.sup.2. The average
particle size was measured by a particle size analyzer (e.g.,
manufactured by SHIMADZU CORPORATION, "SALD(R) 2200").
[2954] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted such that the temperature in each
electrolytic cell reached 90.degree. C. Common salt electrolysis
was performed at a current density of 6 kA/m.sup.2 to measure the
voltage and current density. The current efficiency here is the
proportion of the amount of the produced caustic soda to the passed
current, and when impurity ions and hydroxide ions rather than
sodium ions move through the ion exchange membrane due to the
passed current, the current efficiency decreases. The current
efficiency was obtained by dividing the number of moles of caustic
soda produced for a certain time period by the number of moles of
the electrons of the current passing during that time period. The
number of moles of caustic soda was obtained by recovering caustic
soda produced by the electrolysis in a plastic container and
measuring its mass.
(2) Handling Property (Response Evaluation)
[2955] (A) The ion exchange membrane (membrane) mentioned above was
cut into a 170 mm square, and the electrode obtained each of
Examples and Comparative Examples mentioned below was cut into a
size of 95.times.110 mm. The ion exchange membrane and the
electrode were laminated and placed still on a Teflon plate. The
interval between the anode cell and the cathode cell used in the
electrolytic evaluation was set at about 3 cm. The laminate placed
still was lifted, and an operation of inserting and holding the
laminate therebetween was conducted. This operation was conducted
while the electrode was checked for dislocation and dropping.
[2956] (B) The laminate was placed still on a Teflon plate in the
same manner as in the above (A). The adjacent two corners of the
membrane portion of the laminate were held by hands to lift the
laminate so as to be vertical. The two corners held by hands were
moved from this state to be close to each other such that the
membrane was protruded or recessed. This operation was repeated
again to check the conformability of the electrode to the membrane.
The results were evaluated on a four level scale of 1 to 4 on the
basis of the following indices:
[2957] 1: good handling property
[2958] 2: capable of being handled
[2959] 3: difficult to handle
[2960] 4: substantially incapable of being handled
[2961] Here, with respect to the samples of Examples 3-4 and 3-6,
samples having the same size as that of the large electrolytic cell
were also subjected to handling property evaluation, as mentioned
below. The evaluation results of Example 3-4 and 3-6 were used as
indices to evaluate the difference between the evaluation of the
above (A) and (B) and that of the large-sized ones. That is, in the
case where the evaluation result of a small laminate was "1" or
"2", it was judged that the handling property becomes good even if
the laminate was provided in a larger size.
(3) Proportion of Fixed Region
[2962] The area of the surface opposed to the electrode for
electrolysis in the ion exchange membrane (the total of the portion
corresponding to the conducting surface and the portion
corresponding to non-conducting surface) was calculated as an area
S1. Next, the area of the electrode for electrolysis was calculated
as an area of the conducting surface S2. The areas S1 and S2 were
identified with the area of the laminate of the ion exchange
membrane and electrode for electrolysis when viewed from the side
of the electrode for electrolysis (see FIG. 57). With respect to
the shape of the electrode for electrolysis, even an electrode
having openings had an opening ratio of less than 90%. Thus, the
electrode for electrolysis was considered a flat plate (the opening
portion was to be included in the area).
[2963] The area of the fixed region S3 was also identified as the
area en the laminate was viewed from the top as in FIG. 57 (the
same applies to the area of the portion only corresponding to the
conducting surface S3'). In the case where PTFE tape mentioned
below was fixed as a fixing member, the overlapping portion of the
tape was not to be included in the area. Alternatively, in the case
where PTFE yarns and an adhesive mentioned below were fixed as
fixing members, the area present on the back sides of the electrode
and the membrane was included into the area.
[2964] As described above, 100.times.(S3/S1) was calculated as the
proportion of the area of fixed region .alpha. (%) relative to the
area of the surface opposed to the electrode for electrolysis in
the ion exchange membrane. Additionally, 100.times.S3'/S2 was
calculated as the proportion of the area of the portion only
corresponding to the conducting surface of the fixed region .beta.
relative to the area of the conducting surface.
Example 3-1
[2965] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 22 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.96
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[2966] A porous foil was formed by perforating this nickel foil
with circular holes by punching The opening ratio was 44%.
[2967] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure ruthenium nitrate solution
having a ruthenium concentration of 100 g/L (FURUYA METAL Co.,
Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed
such that the molar ratio between the ruthenium element and the
cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[2968] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced in Example 3-1 was 24
.mu.m. The thickness of the catalytic layer containing ruthenium
oxide and cerium oxide, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m. The coating was formed
also on the surface not roughened.
[2969] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The roughened surface of the electrode was oppositely
disposed on a substantial center position of the carboxylic acid
layer side of the ion exchange membrane (size: 160 mm.times.160 mm)
equilibrated with a 0.1 N NaOH aqueous solution. PTFE tape
(manufactured by NITTO DENKO CORPORATION) was used to fix the four
sides such that the ion exchange membrane and the electrode were
sandwiched as shown in FIG. 57 (note that FIG. 57 illustrates a
schematic view for illustrative purposes only, and the dimensions
are not necessarily accurate. The same applies to the following
figures). In Example 3-1, the PTFE tape was the fixing member, the
proportion .alpha. was 60%, and the proportion .beta. was 1.0%.
[2970] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both ends of one side
were pinched and hung such that the membrane-integrated electrode
was vertical to the ground, the electrode did not come off or was
not displaced.
[2971] The above membrane-integrated electrode was sandwiched
between the anode cell and the cathode cell such that the surface
onto which the electrode was attached was allowed to face the
cathode chamber side. In the sectional structure, the collector,
the mattress, the nickel mesh feed conductor, the electrode, the
membrane, and the anode are arranged in this order from the cathode
chamber side to form a zero-gap structure.
[2972] The resulting electrode was subjected to evaluation. The
results are shown in Table 5.
[2973] The electrode exhibited a low voltage and high current
efficiency. The handling property was also relatively good:
"2".
Example 3-2
[2974] Evaluation was performed in the same manner as in Example
3-1 except for increasing the area at which the PTFE tape
overlapped the electrolytic surface as shown in FIG. 58. That is,
in Example 3-2, the area of the PTFE tape was allowed to increase
in the in-plane direction of the electrode for electrolysis, and
thus, the area of the electrolytic surface in the electrode for
electrolysis decreased than in Example 3-1. In Example 3-2, the
proportion .alpha. was 69%, and the proportion .beta. was 23%. The
evaluation results are shown in Table 5.
[2975] The electrode exhibited a low voltage and high current
efficiency. The handling property was also good: "1".
Example 3-3
[2976] Evaluation was performed in the same manner as in Example
3-1 except for increasing the area at which the PTFE tape
overlapped the electrolytic surface as shown in FIG. 59. That is,
in Example 3-3, the area of the PTFE tape was allowed to increase
in the in-plane direction of the electrode for electrolysis, and
thus, the area of the electrolytic surface in the electrode for
electrolysis decreased than in Example 3-1. In Example the
proportion .alpha. was 87%, and the proportion .beta. was 67%. The
evaluation results are shown in Table 5.
[2977] The electrode exhibited a low voltage and high current
efficiency. The handling property was also good: "1".
Example 3-4
[2978] An electrode identical to that of Example 3-1 was provided
and cut into a size of 95 mm in length and 110 mm in width for
electrolytic evaluation. The roughened surface of the electrode was
oppositely disposed on a substantial center position of the
carboxylic acid layer side of the ion exchange membrane (size: 160
mm.times.160 mm) equilibrated with a 0.1 N NaOH aqueous solution.
PTFE yarn was used to sew the electrode at the lea side thereof in
a vertical direction onto the ion exchange membrane, as shown in
FIG. 60. The PTFE yarn was allowed to pass through a portion at a
vertical distance of 10 mm and a horizontal distance of 10 mm from
a corner of the electrode, from the back side of the sheet of FIG.
60 to the front side thereof, allowed to pass through a portion at
a vertical distance of 35 mm and a horizontal distance of 10 mm,
from the front side of the sheet to the back side, allowed to pass
through a portion at a vertical distance of 60 mm and a horizontal
distance of 10 mm, again from the back side of the sheet to the
front side thereof, and allowed to pass through a portion at a
vertical distance of 85 mm and a horizontal distance of 10 mm, from
the front side of the sheet to the back side thereof. A solution
obtained dispersing an acid-type resin S of a resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.2)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g at a content
of 5% mass in ethanol was applied onto the portions at which the
yarn passed through the ion exchange membrane.
[2979] As described above, in Example the proportion .alpha. was
0.35%, and the proportion .beta. was 0.86%.
[2980] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode face the ground side, the electrode did not
fall off. Even when both the ends of one side were pinched and hung
such that the membrane-integrated electrode was vertical to the
ground, the electrode did not all off.
[2981] The resulting electrode was subjected to evaluation. The
results are shown in Table 5.
[2982] The electrode exhibited a low voltage and high current
efficiency. The handling property was also relatively good:
"2".
[2983] Additionally, an ion exchange membrane and an electrode each
formed in a larger size were provided in Example 3-4. An ion
exchange membrane having a size of 1.5 m in length and 2.5 m in
width and four cathodes having a size of 0.3 m in length and 2.4 m
in width were provided. The cathodes were arranged without any gap
on the carboxylic acid layer side of the ion exchange membrane, and
the cathodes were bonded to the ion exchange membrane by PTFE yarn
to produce a laminate. In this Example, the proportion .alpha. was
0.013%, and the proportion .beta. was 0.017%.
[2984] When an operation of fitting a large electrolyzer with the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, was performed, it was possible to
achieve smooth fitting.
Example 3-5
[2985] An electrode identical to that of Example 3-1 was provided
and cut into a size of 95 mm in length and 110 mm in width for
electrolytic evaluation. The roughened surface of the electrode was
oppositely disposed on a substantial center position of the
carboxylic acid layer side of the ion exchange membrane (size: 160
mm.times.160 mm) equilibrated with a 0.1 N NaOH aqueous solution. A
fixing resin mad of polypropylene shown in FIG. 61 was used to fix
the ion exchange membrane and the electrode. That is, the resin was
placed at two portions in total: a portion at a vertical distance
of 20 mm and a horizontal distance of 20 mm from a corner of the
electrode, and additionally, a portion at a vertical distance of 20
mm and a horizontal distance of 20 mm from the corner located
therebelow. Onto the portions at which the fixing resin passed
through the ion exchange membrane, a solution similar to that of
Example 3-4 was applied.
[2986] As described above, in Example 3-5, the fixing resin and the
resin S served as fixing members, the proportion .alpha. was 0.47%,
and the proportion .beta. was 1.1%.
[2987] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground
allowing the electrode to face the ground side, the electrode did
not fall off. Even when both ends of one side were pinched and hung
such that the membrane-integrated electrode was vertical to the
ground, the electrode did not fall off.
[2988] The resulting electrode was subjected to evaluation. The
results are shown in Table 5.
[2989] The electrode exhibited a low voltage and high current
efficiency. The handling property was also relatively good:
"2".
Example 3-6
[2990] An electrode identical to that of Example 3-1 was provided
and cut into a size of 95 mm in length and 110 mm in width for
electrolytic evaluation. The roughened surface of the electrode was
oppositely disposed on a substantial center position of the
carboxylic acid layer side of the ion exchange membrane (size: 160
mm.times.160 mm) equilibrated with a 0.1 N NaOH aqueous solution.
As shown in FIG. 62, a cyanoacrylate adhesive (trade name: Aron
Alpha, TOAGOSEI CO., LTD.) was used to fix the ion exchange
membrane and the electrode. That is, the membrane and the electrode
were fixed with the adhesive at five points on a vertical side of
the electrode (the points were each equally spaced) and eight
points on a horizontal side of the electrode (the points were each
equally spaced).
[2991] As described above, in Example 3-6, the adhesive served as
fixing members, the proportion .alpha. of 0.78%, and the proportion
.beta. was 1.9%.
[2992] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not fail off. Even when both the ends of one side were pinched and
hung such that the membrane-integrated electrode was vertical to
the ground, the electrode did not fall off.
[2993] The resulting electrode was subjected to evaluation. The
results are shown in Table 5.
[2994] The electrode exhibited a low voltage and high current
efficiency. The handling property was also relatively good:
"1".
[2995] Additionally, an ion exchange membrane and an electrode each
formed in a larger size were provided in Example 3-6. An ion
exchange membrane having a size of 1.5 m in length and 2.5 m in
width and four cathodes having a size of 0.3 m in length and 2.4 m
in width were provided. The edge of one horizontal side of each
four cathodes was connected to each other with the adhesive above
to form one large cathode (1.2 m in length and 2.4 m in width).
This large cathode was bonded to the center portion on the
carboxylic acid layer side of the ion exchange membrane with Aron
Alpha to produce a laminate. That is, the membrane and the
electrode were fixed with the adhesive at five points on a vertical
side of the electrode (the points were each equally spaced) and
eight points on a horizontal side of the electrode (the points were
each equally spaced), in the same manner as in FIG. 62. In this
Example, the proportion .alpha. was 0.019%, and the proportion
.beta. was 0.024%.
[2996] When an operation of fitting a large electrolyzer with the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, was performed, it was possible to
achieve smooth fitting.
Example 3-7
[2997] An electrode identical to that of Example 3-1 was provided
and cut into a size of 95 mm in length and 110 mm in width for
electrolytic evaluation. The roughened surface of the electrode was
oppositely disposed on a substantial center position of the
carboxylic acid layer side of the ion exchange membrane (size: 160
mm.times.160 mm) equilibrated with a 0.1 N NaOH aqueous solution. A
solution similar to that of Example 3-4 was applied to fix the ion
exchange membrane and the electrode. That is, the resin was placed
at two portions in total: a portion at a vertical distance of 20 mm
and a horizontal distance of 20 mm from a corner of the electrode,
and additionally, a portion at a vertical distance of 20 mm and a
horizontal distance of 20 mm from the corner located therebelow
(see FIG. 61).
[2998] As described above, in Example 3-7, the resin S served as
fixing members, the proportion .alpha. was 2.0%, and the proportion
.beta. was 4.8%.
[2999] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not fall off. Even when both the ends of one side were pinched and
hung such that the membrane-integrated electrode was vertical to
the ground, the electrode did not fall off.
[3000] The resulting electrode was subjected to evaluation. The
results are shown in Table 5.
[3001] The electrode exhibited a low voltage and high current
efficiency. The handling property was also relatively good:
"2".
Comparative Example 3-1
[3002] Evaluation was performed in the same manner as in Example
3-1 except for increasing the area at which the PTFE tape
overlapped the electrolytic surface. That is, in Comparative
Example 3-1, the area of the PTFE tape was allowed to increase in
the in-plane direction of the electrode for electrolysis, and thus,
the area of the electrolytic surface in the electrode for
electrolysis decreased than in Example 3-1. In Comparative Example
3-1, the proportion .alpha. is 93%, and the proportion .beta. is
83%. The evaluation results are shown in Table 5.
[3003] The voltage was high, and the current efficiency was also
low. The handling property was good: "1".
Comparative Example 3-2
[3004] Evaluation was performed in the same manner as in Example
3-1 except for increasing the area at which the PTFE tape
overlapped the electrolytic surface. The evaluation results are
shown in Table 5. That is, in Comparative Example 3-2, the area of
the PTFE tape was allowed to increase in the in-plane direction of
the electrode for electrolysis.
[3005] In Comparative Example 3-2, the proportion .alpha. and the
proportion .beta. were 100%, and the entire electrolytic surface
was a fixed region covered with PTFE. Accordingly, it was not
possible to supply an electrolyte solution, and thus, it was not
possible to perform electrolysis. The handling property was good:
"1".
Comparative Example 3-3
[3006] Evaluation was performed in the same manner as in Example
3-1 except no PTFE tape was used, that is, the proportion .alpha.
and the proportion .beta. were 0%. The evaluation results are shown
in Table 5.
[3007] The electrode exhibited a low voltage and high current
efficiency. Meanwhile, since there were no fixed region of the
membrane and the electrode, it was not possible to handle the
membrane and the electrode as a laminate (integrated piece), and
thus, the handling property was "4".
[3008] The evaluation results of Examples 3-1 to 7 and Comparative
Examples 3-1 to 3 were also shown in Table 5 below.
TABLE-US-00005 TABLE 5 Area of Area of fixed region Electrolytic
substrate for Area corresponding Handling evaluation Area of
electrode for of fixed only to Proportion .alpha. Proportion .beta.
property Current membrane electrolysis region conducting surface
100 * S3/S1 100 * S3'/S2 (sensory Voltage efficiency S1 S2 S3 S3'
(%) (%) evaluation) (V) (%) Example 3-1 256 104.5 153 1.0 60 1.0 2
2.98 97.8 Example 3-2 256 104.5 176 24 69 23 1 3.11 97.7 Example
3-3 256 104.5 222 70 87 67 1 3.85 96.1 Example 3-4 256 104.5 0.90
0.90 0.35 0.86 2 2.99 92.2 Example 3-5 256 104.5 1.2 1.2 0.47 1.1 2
3.00 92.5 Example 3-8 256 104.5 2.0 2.0 0.78 1.9 2 2.97 97.5
Example 3-7 256 104.5 5.0 5.0 2.0 4.8 2 2.99 97.0 Comparative
Example 3-1 256 104.5 239 87 93 83 1 5.50 86.8 Comparative Example
3-2 258 104.5 256 104.5 100 100 1 Impossible to electrolyze
Comparative Example 3-3 256 104.5 0 0 0 0 4 2.97 97.5
<Verification of Fourth Embodiment>
[3009] As will be described below, Experiment Examples according to
the fourth embodiment (in the section of <Verification of fourth
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the fourth embodiment (in the
section of <Verification of fourth embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 79 to 90 as appropriate.
[Evaluation Method]
(1) Opening Ratio
[3010] An electrode was cut into a size of 130 mm.times.100 mm. A
digimatic thickness gauge (manufactured by Mitutoyo Corporation,
minimum scale 0.001 mm) was used to calculate an average value of
10 points obtained by measuring evenly in the plane. The value was
used as the thickness of the electrode (gauge thickness) to
calculate the volume. Thereafter, an electronic balance was used to
measure the mass. From the specific gravity of each metal (specific
gravity of nickel=8.908 g/cm.sup.3, specific gravity of
titanium=4.506 g/cm.sup.3), the opening ratio or void ratio was
calculated.
Opening ratio (Void ratio) (%)=(1-(electrode mass)/(electrode
volume.times.metal specific gravity)).times.100
(2) Mass per Unit Area (mg/cm.sup.2)
[3011] An electrode was cut into a size of 130 mm.times.100 mm, and
the mass thereof was measured by an electronic balance. The value
was divided by the area (130 mm.times.100 mm) to calculate the mass
per unit area.
(3) Force Applied per Unit MassUnit Area (1) (Adhesive Force)
(N/mgcm.sup.2))
[3012] [Method (i)]
[3013] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-6001
type load cell).
[3014] A 200 mm square nickel plate having a thickness of 1.2 mm
was subjected to blast processing with alumina of grain-size number
320. The arithmetic average surface roughness (Ra) of the nickel
plate after the blast treatment was 0.7 .mu.m. For surface
roughness measurement herein, a probe type surface roughness
measurement instrument SJ-310 (Mitutoyo Corporation) was used. A
measurement sample was placed on the surface plate parallel to the
ground surface to measure the arithmetic average roughness Ra under
measurement conditions as described below. The measurement was
repeated 6 times, and the average value was listed.
[3015] <Probe shape> conical taper angle=60.degree., tip
radius=2 .mu.m, static measuring force=0.75 mN
[3016] <Roughness standard> JIS2001
[3017] <Evaluation curve> R
[3018] <Filter> GAUSS
[3019] <Cutoff value .lamda.c> 0.8 mm
[3020] <Cutoff value .lamda.s> 2.5 .mu.m
[3021] <Number of sections> 5
[3022] <Pre-running, post-running> available
[3023] This nickel plate was vertically fixed on the lower chuck of
the tensile and compression testing machine.
[3024] As the membrane, an ion exchange membrane A below was
used.
[3025] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTFE) were used (hereinafter
referred to as PTFE yarns). As sacrifice yarns, yarns obtained by
twisting six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
two sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[3026] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin b or a dry resin that was a copolymer or
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[3027] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[3028] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[3029] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% oy mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour replace the counterion of the
ion exchange group by Na, and then washed with water. Then, the
membrane was dried 60.degree. C.
[3030] Further, 20% by mass of rconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. The average particle size was measured by a
partcle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[3031] The ion exchange membrane (membrane) obtained above was
immersed in pure water for 12 hours or more and then used for the
test. The membrane was brought into contact with the above plate
sufficiently moistened with pure water and allowed to adhere to the
plate by the tension of water. At this time, the nickel plate and
the ion exchange membrane were placed so as to align the upper ends
thereof.
[3032] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped by the upper chuck of the
tensile and compression testing machine to hang the electrode. The
load applied on the testing machine at this time was set to 0 N.
The integrated piece of the stainless plates, electrode, and clips
was once removed from the tensile and compression testing machine,
and immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[3033] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the ion exchange membrane
by the surface tension of pure water. The size of the adhesive
surface at this time was 130 mm in width and 110 mm in length. Pure
water in a wash bottle was sprayed to the electrode and the ion
exchange membrane entirely so as to sufficiently moisten the
membrane and the electrode again. Thereafter, a roller formed by
winding a closed-cell type EPDM sponge rubber having a thickness of
5 mm around a vinyl chloride pipe (outer diameter: 38 mm) was
rolled downward from above with lightly pressed over the electrode
to remove excess pure water. The roller was rolled only once.
[3034] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the overlapping
portion of the electrode and the membrane reached 130 mm in width
and 100 mm in length was recorded. The measurement was repeated
three times, and the average value was calculated.
[3035] This average value was divided by the area of the
overlapping portion of the electrode and the ion exchange membrane
and the mass of the electrode of the portion overlapping the ion
exchange membrane to calculate the force applied per unit massunit
area (1). The mass of the electrode of the portion overlapping the
ion exchange membrane was determined through proportional
calculation from the value obtained in (2) Mass per unit area
(mg/cm.sup.2) described above.
[3036] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity
was
[3037] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to the ion exchange membrane that
adhered to a vertically-fixed nickel plate via the surface
tension.
[3038] A schematic view of a method for evaluating the force
applied (1) is shown in. FIG. 79.
[3039] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(4) Force Applied per Unit MassUnit Area (2) (Adhesive Force)
(N/mgcm.sup.2))
[3040] [Method (ii)]
[3041] A tensile and compression testing machine was used for
measurement (Imada-SS Corporation, main testing machine: SDT-52NA
type tensile and compression testing machine, load cell: SL-600
type load cell).
[3042] A nickel plate identical to that in Method (i) was
vertically fixed on the lower chuck of the tensile and compression
testing machine.
[3043] A sample of electrode for electrolysis (electrode) to be
used for measurement was cut into a 130 mm square. The ion exchange
membrane A was cut into a 170 mm square. One side of the electrode
was sandwiched by two stainless plates (thickness: 1 mm, length: 9
mm, width: 170 mm). After positioning so as to align the center of
the stainless plates with the center of the electrode, four clips
were used for uniformly fixing the electrode and plates. The center
of the stainless plates was clamped by the upper chuck of the
tensile and compression testing machine to hang the electrode. The
load applied on the testing machine at this time was set to 0 N.
The integrated piece of the stainless plates, electrode, and claps
was once removed from the tensile and compression testing machine,
and immersed in a vat containing pure water in order to moisten the
electrode sufficiently with pure water. Thereafter, the center of
the stainless plates was clamped again by the upper chuck of the
tensile and compression testing machine to hang the electrode.
[3044] The upper chuck of the tensile and compression testing
machine was lowered, and the sample of electrode for electrolysis
was allowed to adhere to the surface of the nickel plate via the
surface tension of a solution. The size of the adhesive surface at
this time was 130 mm in width and 110 mm in length. Pure water in a
wash bottle was sprayed to the electrode and the nickel plate
entirely so as to sufficiently moisten the nickel plate and the
electrode again. Thereafter, a roller formed by winding a
closed-cell type EPDM sponge rubber having a thickness of 5 mm
around a vinyl chloride pipe (outer diameter: 38 mm) was rolled
downward from above with lightly pressed over the electrode to
remove excess solution. The roller was rolled only once.
[3045] The electrode was raised at a rate of 10 mm/minute to begin
load measurement, and the load when the size of the over portion of
the electrode and the nickel plate in the longitudinal direction
reached 100 mm was recorded. This measurement was repeated three
times, and the average value was calculated.
[3046] This average value was divided by the area of the
overlapping portion or the electrode and the nickel plate and the
mass of the electrode of the portion overlapping the nickel plate
to calculate the force applied per unit massunit area (2). The mass
of the electrode of the portion overlapping the membrane was
determined through proportional calculation from the value obtained
in Mass per unit area (mg/cm.sup.2) described above.
[3047] As for the environment of the measuring chamber, the
temperature was 23.+-.2.degree. C. and the relative humidity
was
[3048] The electrode used in Examples and Comparative Examples was
able to stand by itself and adhere without slipping down or coming
off when allowed to adhere to a vertically-fixed nickel plate via
the surface tension.
[3049] The measurement lower limit of the tensile testing machine
was 0.01 (N).
(5) Method for Evaluating Winding Around Column of 280 mm in
Diameter (1) (%)
(Membrane and Column)
[3050] The evaluation method (1) was conducted by the following
procedure.
[3051] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In Examples 33 and 34, the electrode had been integrated with
the ion exchange membrane by thermal pressing, and thus, an
integrated piece of an ion exchange membrane and an electrode was
provided (electrode of a 130 mm square). After the ion exchange
membrane was sufficiently immersed in pure water, the membrane was
placed on the curved surface of a plastic (polyethylene) pipe
having an outer diameter of 280 mm. Thereafter, excess solution was
removed with a roller formed by winding a closed-cell type EPDM
sponge rubber having a thickness of 5 mm around a vinyl chloride
pipe (outer diameter: 38 mm). The roller was rolled over the ion
exchange membrane from the left to the right of the schematic view
shown in FIG. 80. The roller was rolled only once. One minute
after, the proportion of a portion at which the ion exchange
membrane was brought into a close contact with the plastic pipe
electrode having an outer diameter of 280 mm was measured.
(6) Method for Evaluating Winding Around Column of 280 mm in
Diameter (2) (%)
(Membrane and Electrode)
[3052] The evaluation method (2) was conducted by the following
procedure.
[3053] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 man square, and the electrode was cut into
a 130 mm square. The ion exchange membrane was immersed in pure
water for 12 hours or more and then used for the test. The ion
exchange membrane and the electrode were sufficiently immersed in
pure water and then laminated. This laminate was placed on the
curved surface of a plastic (polyethylene) pipe having an outer
diameter of 280 mm such that the electrode was located outside.
Thereafter, a roller formed by winding a closed-cell type EPDM
sponge rubber having a thickness of 5 mm around a vinyl chloride
pipe (outer diameter: 38 mm) was rolled from the left to the right
of the schematic view shown in FIG. 81 with lightly pressed over
the electrode to remove excess solution. The roller was rolled only
once. One minute after, the proportion of a portion at which the
ion exchange membrane was brought into a close contact with the
electrode was measured.
(7) Method for Evaluating Winding Around Column of 145 mm in
Diameter (3) (%)
(Membrane and Electrode)
[3054] The evaluation method (3) was conducted by the following
procedure.
[3055] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
130 mm square. The ion exchange membrane was immersed in pure water
for 12 hours or more and then used for the test. The ion exchange
membrane and the electrode were sufficiently immersed in pure water
and then laminated. This laminate was placed on the curved surface
of a plastic (polyethylene) pipe having an outer diameter of 145 mm
such that the electrode was located outside. Thereafter, a roller
formed by winding a closed-cell type EPDM sponge rubber having a
thickness of 5 mm around a vinyl chloride pipe (outer diameter: 38
mm) was rolled from the left to the right of the schematic view
shown in FIG. 82 with lightly pressed over the electrode to remove
excess solution. The roller was rolled only once. One minute after,
the proportion of a portion at which the ion exchange membrane was
brought into a close contact with the electrode was measured.
(8) Handling Property (Response Evaluation)
[3056] The ion exchange membrane A (membrane) produced in [Method
(i)] was cut into a 170 mm square, and the electrode was cut into a
size of 95.times.110 mm. The ion exchange membrane was immersed in
pure water for 12 hours or more and then used for the test. In each
Example, the ion exchange membrane and electrode were sufficiently
immersed in three solutions: sodium bicarbonate aqueous solution,
0.1N NaOH aqueous solution, and pure water, then laminated, and
placed still or a Teflon plate. The interval between the anode cell
and the cathode cell used in the electrolytic evaluation was set at
about 3 cm. The laminate placed still was lifted, and an operation
of inserting and holding the laminate therebetween was conducted.
This operation am conducted while the electrode was checked for
dislocation and dropping.
[3057] (B) The ion exchange membrane A (membrane) produced in
[Method (i)] was cut into a 170 mm square, and the electrode was
cut into a size of 95.times.110 mm. The ion exchange membrane was
immersed in pure water for 12 hours or more and then used for the
test. In each Example, the ion exchange membrane and electrode were
sufficiently immersed in three solutions: a sodium bicarbonate
aqueous solution, a 0.1N NaOH aqueous solution, and pure water,
then laminated, and placed still on a Teflon plate. The adjacent
two corners of the membrane portion of the laminate were held by
hands to lift the laminate so as to be vertical. The two corners
held by hands were moved from this state to be close to each other
such that the membrane was protruded or recessed. This move was
repeated again to check the conformability of the electrode to the
membrane. The results were evaluated on a four level scale of 1 to
4 on the basis of the following indices:
[3058] 1: good handling property
[3059] 2: capable of being handled
[3060] 3: difficult to handle
[3061] 4: substantially incapable of being handled
[3062] Here, the sample of Example 4-28, provided in a size
equivalent to that of a large electrolytic cell including an
electrode in a size of 1.3 m.times.2.5 m and an ion exchange
membrane in a size of 1.5 m.times.2.8 m, was, subjected to
handling. The evaluation result of Example ("3" as described below)
was used as an index to evaluate the difference between the
evaluation of the above (A) and (B) and that of the large-sized
one. That is, in the case where the evaluation result of a small
laminate was "1" or "2", it was judged that there was no problem in
the handling property even if the laminate was provided in a larger
size.
(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%),
Common Salt Concentration in Caustic Soda (ppm, on the Basis of
50%))
[3063] The electrolytic performance was evaluated by the following
electrolytic experiment.
[3064] A titanium anode cell having an anode chamber in which an
anode was provided (anode terminal cell) and a cathode cell having
a nickel cathode chamber in which a cathode was provided (cathode
terminal cell) were oppositely disposed. A pair of gaskets was
arranged between the cells, and a laminate (a laminate of the ion
exchange membrane A and an electrode for electrolysis) was
sandwiched between the gaskets. Here, both the ion exchange
membrane A and the electrode for electrolysis were sandwiched
directly between the gaskets. Then, the anode cell, the gasket, the
laminate, the gasket, and the cathode were brought into close
contact together to obtain an electrolytic cell, and an
electrolyzer including the cell was provided.
[3065] The anode was produced by applying a mixed solution of
ruthenium chloride, iridium chloride, and titanium tetrachloride
onto a titanium substrate subjected to blasting and acid etching
treatment as the pretreatment, followed by drying and baking. The
anode was fixed in the anode chamber by welding. As the cathode,
one described in each of Examples and Comparative Examples was
used. As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. Nickel mesh formed
by plain-weaving, nickel wire having a diameter of 150 .mu.m in a
sieve mesh size of 40 was placed thereover, and a string made of
Teflon(R) was used to fix the four corners of the Ni mesh to the
collector. This Ni mesh was used as a feed conductor. This
electrolytic cell has a zero-gap structure by use of the repulsive
force of the mattress as the metal elastic body. As the gaskets,
ethylene propylene diene (EPDM) rubber gaskets were used. As the
membrane, the ion exchange membrane A (160 mm square) produced in
[Method (i)] was used.
[3066] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted so as to allow the temperature in each
electrolytic cell to reach 90.degree. C. Common salt electrolysis
was performed at a current density of 6 kA/m.sup.2 to measure the
voltage, current efficiency, and common salt concentration in
caustic soda. The current efficiency here is the proportion of the
amount of the produced caustic soda to the passed current, and when
impurity ions and hydroxide ions rather than sodium ions move
through the on exchange membrane due to the passed current, the
current efficiency decreases. The current efficiency was obtained
by dividing the number of moles of caustic soda produced for a
certain time by the number of moles of the electrons of the current
passing during that time. The number of moles of caustic soda was
obtained by recovering caustic soda produced by the electrolysis in
a plastic container and measuring its mass. As the common salt
concentration in caustic soda, a value obtained by converting the
caustic soda concentration on the basis of 50% was shown.
[3067] The specification of the electrode and the feed conductor
used in each of Examples and Comparative Examples is shown in Table
6.
(11) Measurement of Thickness of Catalytic Layer, Substrate for
Electrode for Electrolysis, and Thickness of Electrode
[3068] For the thickness of the substrate for electrode for
electrolysis, a digimatic thickness gauge (manufactured Mitutoyo
Corporation, minimum scale 0.001 mm) was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane. The value was used as the thickness of the substrate for
electrode for electrolysis (gauge thickness). For the thickness of
the electrode, a digimatic thickness gauge was used to calculate an
average value of 10 points obtained by measuring evenly in the
plane, in the same manner as for the substrate for electrode. The
value was used as the thickness of the electrode (gauge thickness).
The thickness of the catalytic layer was determined by subtracting
the thickness of the substrate for electrode for electrolysis from
the thickness of the electrode.
(12) Elastic Deformation Test of Electrode
[3069] The ion exchange membrane A (membrane) and the electrode
produced in [Method (i)] were each cut into a 110 mm square. The
ion exchange membrane was immersed in pure water for 12 hours or
more and then used for the test. After the ion exchange membrane
and the electrode were laminated to produce a laminate under
conditions of a temperature: 23.+-.2.degree. C. and a relative
humidity: 30.+-.5%, the laminate was wound around a PVC pipe having
an outer diameter of .PHI.32 mm and a length of 20 cm without any
gap, as shown in FIG. 83. The laminate was fixed using a
polyethylene cable tie such that the laminate wound did not come
off from the PVC pipe or loosen. The laminate was retained in this
state for 6 hours. Thereafter, the cable tie was removed, and the
laminate was unwound from the PVC pipe. Only the electrode was
placed on a surface plate, and the heights L.sub.1 and L.sub.2 of a
portion lifted from the surface plate were measured to determine an
average value. This value was used as the index of the electrode
deformation. That is, a smaller value means that the laminate is
unlikely to deform.
[3070] When an expanded metal is used, there are two winding
direction: the SW direction and the LW direction. In this test, the
laminate was wound in the SW direction.
[3071] Deformed electrodes (electrodes that did not return to their
original flat state) were evaluated for softness after plastic
deformation in accordance with a method as shown in FIG. 84. That
is, a deformed electrode was placed on a membrane sufficiently
immersed in pure water. One end of the electrode was fixed, and the
other lifted end was pressed onto the membrane to release a force,
and an evaluation was performed whether the deformed electrode
conformed to the membrane.
(13) Membrane Damage Evaluation
[3072] As the membrane, an ion exchange membrane B below was
used.
[3073] As reinforcement core material those obtained by twisting
100 denier tape yarns of polytetrafluoroethylene (PTFE) 900 times/m
into a thread form were used (hereinafter referred to as PTFE
yarns). As warp sacrifice yarns, yarns obtained by twisting eight
35 denier filaments of polyethylene terephthalate (PET) 200 times/m
were used. (hereinafter referred to as PET yarns). As weft
sacrifice yarns, yarns obtained by twisting eight 35 denier
filaments of poly-ethylene terephthalate (PET) 200 times/m were
used. First, the PTFE yarns and the sacrifice yarns were
plain-woven with 24 PTFE yarns/inch so that two sacrifice yarns
were arranged between adjacent PTFE yarns, to obtain a woven fabric
having a thickness of 100 .mu.m.
[3074] Next, a polymer (A1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.92 mg equivalent/g and a
polymer (B1) of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g were provided.
Using these polymers (A1) and (B1), a two-layer film X in which the
thickness of a polymer (A1) layer was 25 .mu.m and the thickness of
a polymer (31) layer was 89 .mu.m was obtained by a coextrusion T
die method. As the ion exchange capacity of each polymer, shown was
the ion exchange capacity in the case of hydrolyzing the ion
exchange group precursors of each polymer for conversion into ion
exchange groups.
[3075] Separately, a polymer (B2) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.10 mg equivalent/g was provided.
This polymer was single-layer extruded to obtain a film Y having a
thickness of 20 .mu.m.
[3076] Subsequently, release paper, the film Y, a reinforcing
material, and the film X were laminated in this order on a hot
plate having a heat source and a vacuum source inside and having
micropores on its surface, heated and depressurized under the
conditions of a hot plate temperature of 225.degree. C. and a
degree of reduced pressure of 0.022 MPa for two minutes, and then
the release paper was removed to obtain a composite membrane. The
resulting composite membrane was immersed in an aqueous solution
comprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH)
for an hour for saponification. Thereafter, the membrane was
immersed in 0.5N NaOH for an hour to replace the ions attached to
the ion exchange groups by Na, and then washed with water. Further,
the membrane was dried at 60.degree. C.
[3077] Additionally, a polymer (B3) of a dry resin that was a
copolymer of CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.05 mg equivalent/g were
hydrolyzed and then was turned into an acid type with hydrochloric
acid. Zirconium oxide particles having an average particle size of
primary particles of 0.02 .mu.m were added to a 50/50 (mass ratio)
mixed solution of water and ethanol in which the polymer (B3') of
this acid type was dissolved in a proportion of 5% by mass such
that the mass ratio of the polymer (B3') to the zirconium oxide
particles was 20/80. Thereafter, the polymer (B3') was dispersed in
a suspension of the zirconium oxide particles with a ball mill to
obtain a suspension.
[3078] This suspension was applied by a spray method onto both the
surfaces of the ion exchange membrane and dried to obtain an ion
exchange membrane B having a coating layer containing the polymer
(B3') and the zirconium oxide particles. The coating density of
zirconium oxide measured by fluorescent X-ray measurement was 0.35
mg/cm.sup.2.
[3079] The anode used was the same as in (9) Electrolytic
evaluation.
[3080] The cathode used was one described in each of Examples and
Comparative Examples. The collector, mattress, and feed conductor
of the cathode chamber used were the same as in (9) Electrolytic
evaluation. That is, a zero-gap structure had been provided by use
of Ni mesh as the feed conductor and the repulsive force of the
mattress as the metal elastic body. The gaskets used were the same
as in (9) Electrolytic evaluation. As the membrane, the ion
exchange membrane B produced by the method mentioned above was
used. That is, an electrolyzer equivalent to that in (9) was
provided except that the laminate of the ion exchange membrane B
and the electrode for electrolysis was sandwiched between a pair of
gaskets.
[3081] The above electrolytic cell was used to perform electrolysis
of common salt. The brine concentration (sodium chloride
concentration) in the anode chamber was adjusted to 205 g/L. The
sodium hydroxide concentration in the cathode chamber was adjusted
to 32% by mass. The temperature each in the anode chamber and the
cathode chamber was adjusted such that the temperature in each
electrolytic cell reached 70.degree. C. Common salt electrolysis
was performed at a current density of 8 kA/m.sup.2. The
electrolysis was stopped 12 hours after the start of the
electrolysis, and the ion exchange membrane B was removed and
observed for its damage condition.
[3082] ".largecircle." means no damage. ".times." means that damage
was present on the substantially entire surface of the ion exchange
membrane.
(14) Ventilation Resistance of Electrode
[3083] The ventilation resistance of the electrode was measured
using an air permeability tester KES-F8 (trade name, KATO TECH CO.,
LTD.). The unit for the ventilation resistance value is kPas/m. The
measurement was repeated 5 times, and the average value was listed
in Table 7. The measurement was conducted under the following two
conditions. The temperature of the measuring chamber was 24.degree.
C. and the relative humidity was 32%.
Measurement Condition 1 (Ventilation Resistance 1)
[3084] Piston speed: 0.2 cm/s
[3085] Ventilation volume: 0.4 cc/cm.sup.2/s
[3086] Measurement range: SENSE L (low)
[3087] Sample size: 50 mm.times.50 mm
Measurement Condition 2 (Ventilation Resistance 2)
[3088] Piston speed: 2 cm/s
[3089] Ventilation volume: 4 cc/cm.sup.2/s
[3090] Measurement range: SENSE M (medium) or H (high)
[3091] Sample size: 50 mm.times.50 mm
Example 4-1
[3092] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 16 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.71
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[3093] A porous foil was formed by perforating this nickel foil
with circular holes by poaching. The opening ratio was 49%.
[3094] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[3095] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced in Example 4-1 was 24
.mu.m. The thickness of the catalytic layer, which was determined
by subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode, was 8 .mu.m. The
coating was formed also on the surface not roughened. The thickness
was the total thickness of ruthenium oxide and cerium oxide.
[3096] The measurement results of the adhesive force of the
electrode produced by the above method are shown in Table 7. A
sufficient adhesive force was observed.
[3097] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3098] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
[3099] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The roughened surface of the electrode was oppositely
disposed on a substantial center position of the carboxylic acid
layer side of the ion exchange membrane A (size: 160 mm.times.160
mm), produced in [Method (i)] and equilibrated with a 0.1 N NaOH
aqueous solution, and allowed to adhere thereto via the surface
tension of the aqueous solution.
[3100] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the electrode, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did not come
off or was not displaced.
[3101] The above membrane-integrated electrode was sandwiched
between the anode cell and the cathode cell such that the surface
onto which the electrode was attached was allowed to face the
cathode chamber side. In the sectional structure, the collector,
the mattress, the nickel mesh feed conductor, the electrode, the
membrane, and the anode are arranged in the order mentioned from
the cathode chamber side to form a zero-gap structure.
[3102] The resulting electrode was subjected to electrolytic
evaluation. The results are shown in Table 7.
[3103] The electrode exhibited a low voltage, nigh current
efficiency, and a low common salt concentration in caustic soda.
The handling property was also good: "1". The membrane damage was
also evaluated as good: "0".
[3104] When the amount of coating after the electrolysis was
measured by fluorescent X-ray analysis (XRF), substantially 100% of
the coating remained on the roughened surface, and the coating on
the surface not roughened was reduced. This indicates that the
surface opposed to the membrane (roughened surface) contributes to
the electrolysis and the other surface not opposed to the membrane
can achieve satisfactory electrolytic performance when the amount
of coating is small or no coating is present.
Example 4-2
[3105] In Example 4-2, an electrolytic nickel foil having a gauge
thickness of 22 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
0.96 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3106] The thickness of the electrode was 29 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 7 .mu.m. The coating was formed
also on the surface not roughened.
[3107] A sufficient adhesive force was observed.
[3108] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3109] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0033 (kPas/m) under the
measurement condition 2.
[3110] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was also evaluated as good: "0".
[3111] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 4-3
[3112] In Example 4-3, an electrolytic nickel foil having a gauge
thickness of 30 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
1.38 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 44%. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3113] The thickness of the electrode was 38 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m. The coating was formed
also on the surface not roughened.
[3114] A sufficient adhesive force was observed.
[3115] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3116] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[3117] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[3118] When the amount of coating after the electrolysis was
measured by XRF, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 4-4
[3119] In Example 4-4, an electrolytic nickel foil having a gauge
thickness of 16 .mu.m was used as the substrate for electrode for
cathode electrolysis. One surface of this nickel foil was subjected
to a roughening treatment by means of electrolytic nickel plating.
The arithmetic average roughness Ra of the roughened surface was
0.71 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. The opening
ratio was 75%. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3120] The thickness of the electrode was 24 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[3121] A sufficient adhesive force was observed.
[3122] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3123] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[3124] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[3125] When the amount of coating after the electrolysis was
measured by XRT, substantially 100% of the coating remained on the
roughened surface, and the coating on the surface not roughened was
reduced. This indicates that the surface opposed to the membrane
(roughened surface) contributes to the electrolysis and the other
surface not opposed to the membrane can achieve satisfactory
electrolytic performance when the amount of coating is small or no
coating is present.
Example 4-5
[3126] In Example 4-5, an electrolytic nickel foil having a gauge
thickness of 20 .mu.m was provided as the substrate for electrode
for cathode electrolysis. Both the surface of this nickel foil was
subjected to a roughening treatment by means of electrolytic nickel
plating. The arithmetic average roughness Ra of the roughened
surface was 0.96 .mu.m. Both the surfaces had the same roughness.
The measurement of the surface roughness was performed under the
same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. The opening ratio
was 49%. Except for the above described, evaluation was performed
in the same manner as in Example 4-1, and the results are shown in
Table 7.
[3127] The thickness of the electrode was 30 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m. The coating was formed
also on the surface not roughened.
[3128] A sufficient adhesive force was observed.
[3129] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3130] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0023 (kPas/m) under the
measurement condition 2.
[3131] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
[3132] Additionally, when the amount of coating after the
electrolysis was measured by XRF, substantially 100% of the coating
remained on both the surface. In consideration of comparison with
Examples 4-1 to 4-4, this indicates that the other surface not
opposed to the membrane can achieve satisfactory electrolytic
performance when the amount of coating is small or no coating is
present.
Example 4-6
[3133] In Example 4-6, evaluation was performed in the same manner
as in Example 4-1 except that coating of the substrate for
electrode for cathode electrolysis was performed by ion plating,
and the results are shown in Table 7. In the ion plating, film
forming was performed using a heating temperature of 200.degree. C.
and Ru metal target under an argon/oxygen atmosphere at a film
forming pressure of 7.times.10.sup.-2 Pa. The coatrig formed was
ruthenium oxide.
[3134] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[3135] A sufficient adhesive force was observed.
[3136] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3137] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
[3138] Additionally, the electrode exhibited a low voltage, high
current efficiency and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-7
[3139] In Example 4-7, the substrate for electrode for cathode
electrolysis was produced by an electroforming method. The
photomask had a shape formed by vertically and horizontally
arranging 0.485 mm.times.0.485 mm squares at an interval of 0.15
mm. Exposure, development, and electroplating were sequentially
performed to obtain a nickel porous foil having a gauge thickness
of 20 .mu.m and an opening ratio of 56%. The arithmetic average
roughness Ra of the surface was 0.71 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3140] The thickness of the electrode was 37 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 17 .mu.m.
[3141] A sufficient adhesive force was observed.
[3142] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3143] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[3144] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-8
[3145] In Example 4-8, the substrate for electrode for cathode
electrolysis was produced by an electroforming method. The
substrate had a gauge thickness of 50 .mu.m and an opening ratio of
56%. The arithmetic average roughness Ra of the surface was 0.73
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment. Except for the above
described, evaluation was performed in the same manner as in
Example 4-1, and the results are shown in Table 7.
[3146] The thickness of the electrode was 60 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[3147] A sufficient adhesive force was observed.
[3148] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3149] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0032 (kPas/m) under the
measurement condition 2.
[3150] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-9
[3151] In Example 4-9, a nickel nonwoven fabric having a gauge
thickness of 150 .mu.m and a void ratio of 76% (manufactured by
NIKKO TECHNO, Ltd.) was used as the substrate for electrode for
cathode electrolysis. The nonwoven fabric had a nickel fiber
diameter of about 40 .mu.m and a basis weight of 300 g/m.sup.2.
Except for the above described, evaluation was performed in the
same manner as in Example 4-1, and the results are shown in Table
7.
[3152] The thickness of the electrode was 165 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 15 .mu.m.
[3153] A sufficient adhesive force was observed.
[3154] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 29 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[3155] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
lender the measurement condition 1 and 0.0612 (kPas/m) under the
measurement condition 2.
[3156] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 4-10
[3157] In Example 4-10, a nickel nonwoven fabric having a gauge
thickness of 200 .mu.m and a void ratio of 72% (manufactured by
NIKKO TECHNO, Ltd.) was used as the substrate for electrode for
cathode electrolysis. The nonwoven fabric had a nickel fiber
diameter of about 40 .mu.m and a basis weight of 500 g/m.sup.2.
Except for the above described, evaluation was performed in the
same manner as in Example 4-1, and the results are shown in Table
7.
[3158] The thickness of the electrode was 215 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 15 .mu.m.
[3159] A sufficient adhesive force was observed.
[3160] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 40 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[3161] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0164 (kPas/m) under the
measurement condition 2.
[3162] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 4-11
[3163] In Example 4-11, foamed nickel having a gauge thickness of
200 .mu.m and a void ratio of 72% (manufactured by Mitsubishi
Materials Corporation) was used as the substrate for electrode for
cathode electrolysis. Except for the above described, evaluation
was performed in the same manner as in Example 4-1, and the results
are shown in Table 7.
[3164] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 10 .mu.m.
[3165] A sufficient adhesive force was observed.
[3166] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 17 mm, and the electrode
did not return to the original flat state. Then, when softness
after plastic deformation was evaluated, the electrode conformed to
the membrane due to the surface tension. Thus, it was observed that
the electrode was able to be brought into contact with the membrane
by a small force even if the electrode was plastically deformed and
this electrode had a satisfactory handling property.
[3167] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0402 (kPas/m) under the
measurement condition 2.
[3168] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was evaluated as good: "0".
Example 4-12
[3169] In Example 4-12, a 200-mesh nickel mesh having a line
diameter of 50 .mu.m, a gauge thickness of 100 .mu.m, and an
opening ratio of 37% was used as the substrate for electrode for
cathode electrolysis. A blast treatment was performed with alumina
of grain-size number 320. The blast treatment did not change the
opening ratio. It is difficult to measure the roughness of the
surface of the metal net. Thus, in Example 4-12, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra of a wire piece of the
ire mesh was 0.64 .mu.m. The measurement of the surface roughness
was performed under the same conditions as for the surface
roughness measurement of the nickel plate subjected to the blast
treatment. Except for the above described, evaluation was performed
in the same manner as in Example 4-1, and the results are shown in
Table 7.
[3170] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[3171] A sufficient adhesive force was observed.
[3172] When a deformation test of the electrode was performed, the
average value of L1 and P2. was 0.5 mm. It was found that the
electrode had a broad elastic deformation region.
[3173] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0154 (kPas/m) under the
measurement condition 2.
[3174] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also as good as "1". The membrane
damage was also evaluated as good: "0".
Example 4-13
[3175] In Example 4-13, a 150-mesh nickel mesh having a line
diameter of 65 .mu.m, a gauge thickness of 130 .mu.m, and an
opening ratio of 38% was used as the substrate for electrode for
cathode electrolysis. A blast treatment was performed with alumina
of grain-size number 320. The blast treatment did hot change the
opening ratio. It is difficult to measure the roughness of the
surface of the metal net. Thus, in Example 4-13, a nickel plate
having a thickness of 1 mm was simultaneously subjected to the
blast treatment during the blasting, and the surface roughness of
the nickel plate was taken as the surface roughness of the wire
mesh. The arithmetic average roughness Ra was 0.66 .mu.m. The
measurement of the surface roughness was performed under the same
conditions as for the surface roughness measurement of the nickel
plate subjected to the blast treatment. Except for the above
described, the above evaluation was performed in the same manner as
in Example 4-1, and the results are shown in Table 7.
[3176] The thickness of the electrode was 133 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 3 .mu.m.
[3177] A sufficient adhesive force was observed.
[3178] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 6.5 mm. It was found that
the electrode had a broad elastic deformation region.
[3179] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0124 (kPas/m) under the
measurement condition 2.
[3180] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The electrode had a handling property of "2" and was
determined to be handleable as a large laminate. The membrane
damage was also evaluated as good: "0".
Example 4-14
[3181] In Example 4-14, a substrate identical to that of Example
4-3 (gauge thickness of 30 .mu.m and opening ratio of 44%) was used
as the substrate for electrode for cathode electrolysis.
Electrolytic evaluation was performed with a structure identical to
that of Example 4-1 except that no nickel mesh feed conductor was
included. That is, in the sectional structure of the cell, the
collector, the mattress, the membrane-integrated electrode, and the
anode are arranged in the order mentioned from the cathode chamber
side to form a zero-gap structure, and the mattress serves as the
feed conductor. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3182] A sufficient adhesive force was observed.
[3183] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3184] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[3185] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-15
[3186] In Example 4-15, a substrate identical to that of Example
4-3 (gauge thickness of 30 .mu.m and opening ratio of 44%) was used
as the substrate for electrode for cathode electrolysis. The
cathode used in Reference Example 1, which was degraded and had an
enhanced electrolytic voltage, was placed instead of the nickel
mesh feed conductor. Except for the above described, electrolytic
evaluation was performed with a structure identical to that of
Example 4-1. That is, in the sectional structure of the cell, the
collector, the mattress, the cathode that was degraded and had an
enhanced electro tic voltage (serves as the feed conductor), the
cathode, the membrane, and the anode are arranged in the order
mentioned from the cathode chamber side to form a zero-gap
structure, and the cathode that is degraded and has an enhanced
electrolytic voltage serves as the feed conductor. Except for the
above described, evaluation was performed in the same manner as in
Example 4-1, and the results are shown in Table 7.
[3187] A sufficient adhesive force was observed.
[3188] When a deformation test of the electrode was performed, the
average value of L1 and L.sub.2 was 0 mm. It was found that the
electrode had a broad elastic deformation region.
[3189] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
[3190] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-16
[3191] A titanium foil having a gauge thickness of 20 .mu.m was
provided as the substrate for electrode for anode electrolysis.
Both the surfaces of the titanium foil were subjected to a
roughening treatment. A porous foil was formed by perforating this
titanium foil with circular holes by punching. The hole diameter
was 1 mm, and the opening ratio was 14%. The arithmetic average
roughness Ra of the surface was 0.37 .mu.m. The measurement of the
surface roughness was performed under the same conditions as for
the surface roughness measurement of the nickel plate subjected to
the blast treatment.
[3192] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among, the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[3193] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). After the above coating liquid was applied onto
the titanium porous foil, drying at 60.degree. C. for 10 minutes
and baking at 475.degree. C. for 10 minutes were performed. A
series of these coating, drying, preliminary baking, and baking
operations was repeatedly performed, and then baking at 520.degree.
C. was performed for an hour.
[3194] The electrode produced by the above method was cut into a
size of 95 mm in length and 110 mm in width for electrolytic
evaluation. The cut electrode was allowed to adhere via the surface
tension of the aqueous solution to a substantial center position of
the sulfonic acid layer side of the ion exchange membrane A (size:
160 mm.times.160 mm) produced in [Method (i)] and equilibrated with
a 0.1 N NaOH aqueous solution.
[3195] The cathode was prepared in the following procedure. First,
a 40-mesh nickel wire mesh having a line diameter of 150 .mu.m was
provided as the substrate. After blasted with alumina as
pretreatment, the wire mesh was immersed in 6 N hydrochloric acid
for 5 minutes, sufficiently washed with pure water, and dried.
[3196] Next, a ruthenium chloride solution having a ruthenium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.) and cerium
chloride (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the
molar ratio between the ruthenium element and the cerium element
was 1:0.25. This mixed solution was sufficiently stirred and used
as a cathode coating liquid.
[3197] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 300.degree. C. for 3 minutes, and
baking at 550.degree. C. for 10 minutes were performed. Thereafter,
baking at 550.degree. C. for an hour was performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated.
[3198] As the collector of the cathode chamber, a nickel expanded
metal was used. The collector had a size of 95 mm in
length.times.110 mm in width. As a metal elastic body, a mattress
formed by knitting nickel fine wire was used. The mattress as the
metal elastic body was placed on the collector. The cathode
produced by the above method was placed thereover, and a string
made of Teflon(R) was used to fix the four corners of the mesh to
the collector.
[3199] Even when the four corners of the membrane portion of the
membrane-integrated electrode, which was formed by integrating the
membrane with the anodes, were pinched and hung such that the
membrane-integrated electrode was in parallel with the ground by
allowing the electrode to face the ground side, the electrode did
not come off or was not displaced. Also when both the ends of one
side were pinched and hung such that the membrane-integrated
electrode was vertical to the ground, the electrode did not come
off or was not displaced.
[3200] The anode used in Reference Example 3, which was degraded
and had an enhanced electrolytic voltage, was fixed to the anode
cell by welding, and the above membrane-integrated electrode was
sandwiched between the anode cell and the cathode cell such that
the surface onto which the electrode was attached was allowed to
face the anode chamber side. That is, in the sectional structure of
the cell, the collector, the mattress, the cathode, the membrane,
the titanium porous foil anode, and the anode that was degraded and
had an enhanced electrolytic voltage were arranged in the order
mentioned from the cathode chamber side to form. a zero-gap
structure. The anode that was degraded and had an enhanced
electrolytic voltage served as the feed conductor. The titanium
porous foil anode and the anode that was degraded and had an
enhanced electrolytic voltage were only in physical contact with
each other and were not fixed with each other by welding.
[3201] Evacuation on this structure was performed in the same
manner as in Example 4-1, and the results are shown in Table 7.
[3202] The thickness of the electrode was 26 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 6 .mu.m.
[3203] A sufficient adhesive force was observed.
[3204] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 4 mm. It was found that
the electrode had a broad elastic deformation region.
[3205] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0060 (kPas/m) under the
measurement condition 2.
[3206] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-17
[3207] In Example 4-17, a titanium foil having a gauge thickness of
20 .mu.m and an opening ratio of 30% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.37 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-16, and the results
are shown in Table 7.
[3208] The thickness of the electrode was 30 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[3209] A sufficient adhesive force was observed.
[3210] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 5 mm. It was found that
the electrode had a broad elastic deformation region.
[3211] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
[3212] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-18
[3213] In Example 4-18, a titanium foil having a gauge thickness of
20 .mu.m and an opening ratio of 42% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.38 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-16, and the results
are shown in Table 7.
[3214] The thickness of the electrode was 32 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 12 .mu.m.
[3215] A sufficient adhesive force was observed.
[3216] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2.5 mm. It was found that
the electrode had a broad elastic deformation region.
[3217] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0022 (kPas/m) under the
measurement condition 2.
[3218] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-19
[3219] In Example 4-19, a titanium foil having a gauge thickness of
50 .mu.m, and an opening ratio of 47% was used as the substrate for
electrode for anode electrolysis. The arithmetic average roughness
Ra of the surface was 0.40 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-16, and the results
are shown in Table 7.
[3220] The thickness of the electrode was 69 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 19 .mu.m.
[3221] A sufficient adhesive force was observed.
[3222] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 8 mm. It was found that
the electrode had a broad elastic deformation region.
[3223] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0024 (kPas/m) under the
measurement condition 2.
[3224] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-20
[3225] In Example 4-20, a titanium nonwoven fabric having a gauge
thickness of 100 .mu.m, a titanium fiber diameter of about 20
.mu.m, a basis weight of 100 g/m.sup.2, and an opening ratio of 78%
was used as the substrate for electrode for anode electrolysis.
Except for the above described, evaluation was performed in the
same manner as in Example 4-16, and the results are shown in Table
7.
[3226] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[3227] A sufficient adhesive force was observed.
[3228] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 2 mm. It was found that
the electrode had a broad elastic deformation region.
[3229] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0228 (kPas/m) under the
measurement condition 2.
[3230] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-21
[3231] In Example 4-21, a 150-mesh titanium wire mesh having a
gauge thickness of 120 .mu.m and a titanium fiber diameter of about
60 .mu.m was used as the substrate for electrode for anode
electrolysis. The opening ratio was 42%. A blast treatment was
performed with alumina of grain-size number 320. It is difficult to
measure the roughness of the surface of the metal net. Thus, in
Example 4-21, a titanium plate having a thickness of 1 mm was
simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the titanium plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.60 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment Except for the above described, evaluation was
performed in the same manner as in Example 4-16, and the results
are shown in Table 7.
[3232] The thickness of the electrode was 140 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 20 .mu.m.
[3233] A sufficient adhesive force was observed.
[3234] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 10 mm. It was found that
the electrode had a broad elastic deformation region.
[3235] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0132 (kPas/m) under the
measurement condition 2.
[3236] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0".
Example 4-22
[3237] In Example 4-22, an anode that was degraded and had an
enhanced electrolytic voltage was used in the same manner as in
Example 4-16 as the anode feed conductor, and a titanium nonwoven
fabric identical to that of Example 4-20 was used as the anode. A
cathode that was degraded and had an enhanced electrolytic voltage
was used in the same manner as in Example 4-15 as the cathode feed
conductor, and a nickel foil electrode identical to that of Example
4-3 was used as the cathode. In the sectional structure of the
cell, the collector, the mattress, the cathode that was degraded
and had an enhanced voltage, the nickel porous foil cathode, the
membrane, the titanium nonwoven, fabric anode, and the anode that
was degraded and had an enhanced electrolytic voltage are arranged
in the order mentioned from the cathode chamber side to form a
zero-gap structure, and the cathode and anode degraded and having
an enhanced electrolytic voltage serve as the feed conductor.
Except for the above described, evaluation was performed in the
same manner as in Example 4-1, and the results are shown in Table
7.
[3238] The thickness of the electrode (anode) was 114 .mu.m, and
the thickness the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electrode (anode), was 14
.mu.m. The thickness of the electrode (cathode) was 38 .mu.m, and
the thickness of the catalytic layer, which was determined by
subtracting the thickness of the substrate for electrode for
electrolysis from the thickness of the electro P (cathode), was 8
.mu.m.
[3239] A sufficient adhesive force was observed both in the anode
and the cathode.
[3240] When a deformation test of the electrode (anode) was
performed, the average value of L.sub.1 and L.sub.2 was 2 mm. When
a deformation test of the electrode (cathode) was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm.
[3241] When the ventilation resistance of the electrode (anode) was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition and 0.0228 (kPas/m) under the
measurement condition 2. When the ventilation resistance of the
electrode (cathode) was measured, the ventilation resistance was
0.07 (kPas/m) or less under the measurement condition 1 and 0.0027
(kPas/m) under the measurement condition 2.
[3242] Additionally, the electrode exhibited a low voltage, high
current efficiency, and a low common salt concentration in caustic
soda. The handling property was also good: "1". The membrane damage
was also evaluated as good: "0" both in the anode and the cathode.
In Example 4-22, the cathode and the anodes were combined by
attaching the cathode to one surface of the membrane and the anode
to the other surface and subjected to the membrane damage
evaluation.
Example 4-23
[3243] In Example 4-23, a microporous membrane "Zirfon Perl UTP
500" manufactured by Agfa was used.
[3244] The Zirfon membrane was immersed in pure water for 12 hours
or more and used for the test. Except for the above described, the
above evaluation was performed in the same manner as in Example
4-3, and the results are shown in Table 7.
[3245] When a deformation test the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 0 mm. It was found that
the electrode had a broad elastic deformation region.
[3246] Similarly to the case where an ion exchange membrane was
used as the membrane, a sufficient adhesive force was observed. The
microporous membrane was brought into a close contact with the
electrode via the surface tension, and the handling property was
good: "1".
Reference Example 1
[3247] In Reference Example 1, used was a cathode used as the
cathode in a large electrolyzer for eight years, degraded, and
having an enhanced electrolytic voltage. The above cathode was
placed instead of the nickel mesh feed conductor on the mattress of
the cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In Reference Example 1, no
membrane-integrated electrode was used. In the sectional structure
of the cell, the collector, the mattress, the cathode that was
degraded and had an enhanced electrolytic voltage, the ion exchange
membrane A, and the anodes were arranged in the order mentioned
from the cathode chamber side to form a zero-gap structure.
[3248] As a result of the electrolytic evaluation with this
structure, the voltage was 3.04 V, the current efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 20 ppm. Consequently, due to
degradation of the cathode, the voltage was high.
Reference Example 2
[3249] In Reference Example 2, a nickel mesh feed conductor was
used as the cathode. That is, electrolysis was performed on nickel
mesh having no catalyst coating thereon.
[3250] The nickel mesh cathode was placed on the mattress of the
cathode chamber, and the ion exchange membrane A produced in
[Method (i)] was sandwiched therebetween. Then, electrolytic
evaluation was performed. In the sectional structure of the
electric cell of Reference Example 2, the collector, the mattress,
the nickel mesh, the ion exchange membrane A, and the anodes were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[3251] As a result of the electrolytic evaluation with this
structure, the voltage was 3.38 V, the current efficiency was
97.7%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 24 ppm. Consequently, the
voltage was high because the cathode catalyst had no coating.
Reference Example 3
[3252] In Reference Example 3, used was an anode used as the anode
in a large electrolyzer for about eight years, degraded, and having
an enhanced electrolytic voltage.
[3253] In the sectional structure of the electrolytic cell of
Reference Example 3, the collector, the mattress, the cathode, the
ion exchange membrane A produced in [Method (i)], and the anode
that was degraded and had an enhanced electrolytic voltage were
arranged in the order mentioned from the cathode chamber side to
form a zero-gap structure.
[3254] As a result of the electrolytic evaluation with this
structure, the voltage was 3.18 V, the correct efficiency was
97.0%, the common salt concentration in caustic soda (value
converted on the basis of 50%) was 22 ppm. Consequently, due to
degradation of the anode, the voltage was high.
Example 4-24
[3255] In Example 4-24, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 33% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of drain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 4-24, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.68 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3256] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 14 .mu.m.
[3257] The mass per unit area was 67.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.05
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter was 64%, and the result of evaluation
of winding around column of 145 mm in diameter (3) was 22%. The
portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[3258] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[3259] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Example 4-25
[3260] In Example 4-25, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 16% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 4-25, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.64 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3261] The thickness of the electrode was 107 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 7 .mu.m.
[3262] The mass per unit area was 78.1 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.04
(N/mgcm2). Thus, the result of evaluation of winding around column
of 280 mm in diameter (2) was 37%, and the result of evaluaton of
winding around column of 145 mm in diameter (3) was 25%. The
portions at which the electrode came off from the membrane
increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "4",
which was also problematic. The membrane damage was evaluated as
"0".
[3263] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 18.5 mm.
[3264] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition and 0.0176 (kPas/m) under the
measurement condition 2.
Example 4-26
[3265] In Example 4-26, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 40% was used
as the substrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 4-26, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.70 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Coating of the substrate for electrode for
electrolysis was performed by ion plating in the same manner as in
Example 4-6. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3266] The thickness of the electrode was 110 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 10 .mu.m.
[3267] The force applied per unit massunit area (1) was such a
small value as 0.07 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter (2) was 80%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 32%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[3268] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11 mm.
[3269] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0030 (kPas/m) under the
measurement condition 2.
Example 4-27
[3270] In Example 4-27, a fully-rolled nickel expanded metal having
a gauge thickness of 100 .mu.m and an opening ratio of 58% was used
as the slibstrate for electrode for cathode electrolysis. A blast
treatment was performed with alumina of grain-size number 320. The
opening ratio was not changed after the blast treatment. It is
difficult to measure the surface roughness of the expanded metal.
Thus, in Example 4-27, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the wire mesh. The arithmetic average
roughness Ra was 0.64 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-1, and the results are
shown in Table 7.
[3271] The thickness of the electrode was 109 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 9 .mu.m.
[3272] The force applied per unit massunit area (1) was such a
small value as 0.06 (N/mgcm.sup.2). Thus, the result of evaluation
of winding around column of 280 mm in diameter was 69%, and the
result of evaluation of winding around column of 145 mm in diameter
(3) was 39%. The portions at which the electrode came off from the
membrane increased. This is because there were problems in that the
electrode was likely to come off when the membrane-integrated
electrode was handled and in that the electrode came off and fell
from the membrane during handled. The handling property was "3",
which was also problematic. The membrane damage was evaluated as
"0".
[3273] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 11.5 mm.
[3274] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0028 (kPas/m) under the
measurement condition 2.
Example 4-28
[3275] In Example 4-28, a nickel wire mesh having a gauge thickness
of 300 .mu.m and an opening ratio of 56% was used as the substrate
for electrode for cathode electrolysis. It is difficult to measure
the surface roughness of the wire mesh. Thus, in Example 4-28, a
nickel plate having a thickness of 1 mm was simultaneously
subjected to the blast treatment during the blasting, and the
surface roughness of the nickel plate was taken as the surface
roughness of the wire mesh. A blast treatment was performed with
alumina of grain-size number 320. The opening ratio was not changed
after the blast treatment. The arithmetic average roughness Ra was
0.64 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. Except for
the above described, evaluation was performed in the same manner as
in Example 4-1, and the results are shown in Table 7.
[3276] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[3277] The mass per unit area was 49.2 (mg/cm.sup.2). Thus, the
result of evaluation of winding around column of 280 mm in diameter
(2) was 88%, and the result of evaluation of winding around column
of 145 mm in diameter (3) was 42%. The portions at which the
electrode came off from the membrane increased. This is because the
electrode was likely to come off when the membrane-integrated
electrode is handled and the electrode may come off and fall from
the membrane during handled. There was a problem in the handling
property, which was evaluated as "3". When the large size electrode
was actually operated, it was possible to evaluate the handling
property as "3". The membrane damage was evaluated as "0".
[3278] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[3279] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
Example 4-29
[3280] In Example 4-29, a nickel wire mesh having a gauge thickness
of 200 .mu.m and an opening ratio of 37% was used as the substrate
for electrode for cathode electrolysis. A blast treatment was
performed with alumina of grain-size number 320. The opening ratio
was not changed after the blast treatment. It is difficult to
measure the surface roughness of the wire mesh. Thus, in Example
4-29, a nickel plate having a thickness of 1 mm was simultaneously
subjected to the blast treatment during the blasting, and the
surface roughness of the nickel plate was taken as the surface
roughness of the wire mesh. The arithmetic average roughness Ra was
0.65 .mu.m. The measurement of the surface roughness was performed
under the same conditions as for the surface roughness measurement
of the nickel plate subjected to the blast treatment. Except for
the above described, evaluation of electrode electrolysis,
measurement results of the adhesive force, and adhesiveness were
performed in the same manner as in Example 4-1. The results are
shown in Table 7.
[3281] The thickness of the electrode was 210 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness or the electrode, was 10 .mu.m.
[3282] The mass per unit area was 56.4 (mg/cm.sup.2). Thus, the
result of evaluation method of winding around column of 145 mm in
diameter (3) was 63%, and the adhesiveness between the electrode
and the membrane was poor. This is because the electrode was likely
to come off when the membrane-integrated electrode is handled and
the electrode may come off and fall from the membrane during
handled. There was a problem in the handling property, which was
evaluated as "3". The membrane damage was evaluated as "0".
[3283] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 19 mm.
[3284] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0096 (kPas/m) under the
measurement condition 2.
Example 4-30
[3285] In Example 4-30, a full-rolled titanium expanded metal
having a gauge thickness of 500 .mu.m and an opening ratio of 17%
was used as the substrate for electrode for anode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 4-30, a titanium plate having a thickness
of 1 mm was simultaneously subjected to the blast treatment during
the blasting, and the surface roughness of the titanium plate was
taken as the surface roughness of the wire mesh. The arithmetic
average roughness Ra was 0.60 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, evaluation was
performed in the same manner as in Example 4-16, and the results
are shown in Table 7.
[3286] The thickness of the electrode was 508 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[3287] The mass per unit area was 152.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of windng around column of 145 mm in diameter (3) was
less than 5%. The portions at which the electrode came off from the
membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during: handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[3288] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[3289] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0072 (kPas/m) under the
measurement condition 2.
Example 4-31
[3290] In Example 4-31, a full-rolled titanium expanded metal
having a gauge thickness of 800 .mu.m and an opening ratio of 8%
was used as the substrate for electrode for anode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 4-31, a titanium plate having a thickness
of 1 mm was simultaneously subjected to the blast treatment during
the blasting, and the surface roughness of the titanium plate was
taken as the surface roughness of the wire mesh. The arithmetic
average roughness Ra was 0.61 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, the above
evaluation was performed in the same manner as in Example 4-16, and
the results are shown in Table 7.
[3291] The thickness of the electrode was 808 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[3292] The mass per unit area was 251.3 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[3293] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[3294] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0172 (kPas/m) under the
measurement condition 2.
Example 4-32
[3295] In Example 4-32, a full-rolled titanium expanded metal
having a gauge thickness of 1000 .mu.m and an opening ratio of 46%
was used as the substrate for electrode for anode electrolysis. A
blast treatment was performed with alumina of grain-size number
320. The opening ratio was not changed after the blast treatment.
It is difficult to measure the surface roughness of the expanded
metal. Thus, in Example 4-32, a titanium plate having a thickness
of 1 mm was simultaneously subjected to the blast treatment during
the blasting, and the surface roughness of the titanium plate was
taken as the surface roughness of the wire mesh. The arithmetic
average roughness Ra was 0.59 .mu.m. The measurement of the surface
roughness was performed under the same conditions as for the
surface roughness measurement of the nickel plate subjected to the
blast treatment. Except for the above described, the above
evaluation was performed in the same manner as in Example 4-16, and
the results are shown in Table 7.
[3296] The thickness of the electrode was 1011 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 11 .mu.m.
[3297] The mass per unit area was 245.5 (mg/cm.sup.2). The force
applied per unit massunit area (1) was such a small value as 0.01
(N/mgcm.sup.2). Thus, the result of evaluation of winding around
column of 280 mm in diameter (2) was less than 5%, and the result
of evaluation of winding around column of 145 mm in diameter (3)
was less than 5%. The portions at which the electrode came off from
the membrane increased. This is because the electrode was likely to
come off when the membrane-integrated electrode was handled, the
electrode came off and fell from the membrane during handled, and
so on. The handling property was "4", which was also problematic.
The membrane damage was evaluated as "0".
[3298] When a deformation test of the electrode was performed, the
electrode did not recover and remained rolled up in the PVC pipe
form. Thus, it was not possible to measure the values of L.sub.1
and L.sub.2.
[3299] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0027 (kPas/m) under the
measurement condition 2.
Example 4-33
[3300] In Example 4-33, a membrane electrode assembly was produced
by thermally compressing an electrode onto a membrane with
reference to a prior art document (Examples of Japanese Patent
Laid-Open No. 58-48686).
[3301] A nickel expanded metal having a gauge thickness of 100
.mu.m and an opening ratio or 33% was used as the substrate for
electrode for cathode electrolysis to Perform electrode coating in
the same manner as in Example 4-1. Thereafter, one surface of the
electrode was subjected to an inactivation treatment in the
following procedure. Polyimide adhesive tape (Chukoh Chemical
Industries, Ltd.) was attached to one surface of the electrode. A
PTFE dispersion (Dupont-Mitsui Fluorochemicals Co., Ltd., 31-JR
(trade name)) was applied onto the other surface and dried in a
muffle furnace at 120.degree. C. for 10 minutes. The polymide tape
was peeled off, and a sintering treatment was performed in a muffle
furnace set at 380.degree. C. for 10 minutes. This operation was
repeated twice to inactivate the one surface of the electrode.
[3302] Produced was a membrane formed by two layers of a
perfluorocarbon polymer of which terminal functional group is
"--COOCH.sub.3" (C polymer) and a perfluorocarbon polymer of which
terminal functional group is "--SO.sub.2F" (S polymer). The
thickness of the C polymer layer was 3 mils, and the thickness of
the S polymer layer was 4 mils. This two-layer membrane was
subjected to a saponification treatment to thereby introduce ion
exchange groups to the terminals of the polymer by hydrolysis. The
C polymer terminals were hydrolyzed into carboxylic acid groups and
the S polymer terminals into sulfo groups. The ion exchange
capacity as the sulfonic acid group was 1.0 meq/g, and the ion
exchange capacity as the carboxylic acid group was 0.9 meq/g.
[3303] The inactivated electrode surface was oppositely disposed to
and thermally pressed onto the surface having carboxylic acid
groups as the ion exchange groups to integrate the ion exchange
membrane and the electrode. The one surface of the electrode was
exposed even after the thermal compression, and the electrode
passed through no portion of the membrane.
[3304] Thereafter, in order to suppress attachment of bubbles to be
generated during electrolysis to the membrane, a mixture of
zirconium oxide and a perfluorocarbon polymer into which sulfo
groups had been introduced was applied onto both the surfaces.
Thus, the membrane electrode assembly of Example 4-33 was
produced.
[3305] When the force applied per unit massunit area (1) was
measured using this membrane electrode assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.50 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The membrane electrode assembly of Example 4-33 had a
force applied per unit massunit area (1) of at least 1.50
(N/mgcm.sup.2) and was strongly bonded.
[3306] When evaluation of winding around column of 280 mm in
diameter (1) was performed, the area in contact with the plastic
pipe was less than 5%. Meanwhile, when evaluation of winding around
column of 280 mm in diameter (2) was performed, the electrode and
the membrane were 100% bonded to each other, but the membrane was
not wound around the column in the first place. The result of
evaluation of winding around column of 145 mm (3) was the same. The
result meant that the integrated electrode impaired the handling
property of the membrane to thereby make it difficult to roll the
membrane into a roil and fold the membrane. The handling property
was "3", which was problematic. The membrane damage was evaluated
as "0". Additionally, when electrolytic evaluation was performed,
the voltage was high, the current efficiency was low, the common
salt concentration in caustic soda (value converted on the basis of
50%) was raised, and the electrolytic performance deteriorated.
[3307] The thickness of the electrode was 114 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 14 .mu.m.
[3308] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 13 mm.
[3309] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0168 (kPas/m) under the
measurement condition 2.
Example 4-34
[3310] In Example 4-34, a 40-mesh nickel mesh having a line
diameter of 150 .mu.m, a gauge thickness of 300 .mu.m, and an
opening ratio of 58% was used as the substrate for electrode for
cathode electrolysis. Except for the above described, a membrane
electrode assembly was produced in the same manner as in Example
4-33.
[3311] When the force applied per unit messunit area (1) was
measured using this membrane electrode assembly, the electrode did
not move upward because the electrode and the membrane were tightly
bonded to each other via thermal compression. Then, the ion
exchange membrane and nickel plate were fixed so as not to move,
and the electrode was pulled upward by a stronger force. When a
force of 1.60 (N/mgcm.sup.2) was applied, a portion of the membrane
was broken. The membrane electrode assembly of Example 4-34 had a
force applied per unit massunit area (1) of at least 1.60
(N/mgcm.sup.2) and was strongly bonded.
[3312] When evaluation of winding around column of 280 mm in
diameter (1) was performed using this membrane electrode assembly,
the contact area with the plastic pipe was less than 5%. Meanwhile,
when evaluation of winding around column of 280 mm in diameter (2)
was performed, the electrode and the membrane were 100% bonded to
each other, but the membrane was not wound around the column in the
first place. The result of evaluation of winding around column of
145 mm (3) was the same. The result meant that the integrated
electrode impaired the handling property of the membrane to thereby
make it difficult to roll the membrane into a roll and fold the
membrane. The handling property was "3", which was problematic.
Additionally, when electrolytic evaluation was performed, the
voltage was high, the current efficiency was low, the common salt
concentration in caustic soda was raised, and the electrolytic
performance deteriorated.
[3313] The thickness of the electrode was 308 .mu.m. The thickness
of the catalytic layer, which was determined by subtracting the
thickness of the substrate for electrode for electrolysis from the
thickness of the electrode, was 8 .mu.m.
[3314] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 23 mm.
[3315] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.07 (kPas/m) or less
under the measurement condition 1 and 0.0034 (kPas/m) under the
measurement condition 2.
Example 4-35
[3316] A nickel line having a gauge thickness of 150 .mu.m was
provided as the substrate for electrode for cathode electrolysis. A
roughening treatment by this nickel line was performed. It is
difficult to measure the surface roughness of the nickel line.
Thus, in Example 4-35, a nickel plate having a thickness of 1 mm
was simultaneously subjected to the blast treatment during the
blasting, and the surface roughness of the nickel plate was taken
as the surface roughness of the nickel line. A blast treatment was
performed with alumina of grain-size number 320. The arithmetic
average roughness Ra was 0.64 .mu.m.
[3317] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure ruthenium nitrate solution
having a ruthenium concentration of 100 g/L (FURUYA METAL Co.,
Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed
such that the molar ratio between the ruthenium element and the
cerium element t was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[3318] A vat containing, the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088 (trade name), thickness 10 mm) around a
chloride (PVC) cylinder was always in contact with the above
coating liquid. A coating roil around which the same EPDM had been
wound was laced at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of one nickel line produced in Example 4-35 was 158
.mu.m.
[3319] The nickel line produced h the above method was cut into a
length of 110 mm and a length of 95 mm. As shown in FIG. 85, the
110 mm nickel line and the 95 mm nickel line were placed such that
the nickel lines vertically overlapped each other at the center of
each of the nickel lines and bonded to each other at the
intersection with. Aron Alpha to produce an electrode. The
electrode was evaluated, and the results are shown in Table 7.
[3320] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.7%.
[3321] The mass per unit area of the electrode was 0.5
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[3322] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 15 mm.
[3323] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance value was 0.0002 (kPas/m).
[3324] Additionally, the structure shown in FIG. 86 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.16 V.
Example 4-36
[3325] In Example 4-36, the electrode produced in Example 4-35 was
used. As shown in FIG. 87, the 110 mm nickel line and the 95 mm
nickel line were placed such that the nickel lines vertically
overlapped each other at the center of each of the nickel lines and
bonded to each other at the intersection with Aron Alpha to produce
an electrode. The electrode was evaluated, and the results are
shown in Table 7.
[3326] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 99.4%.
[3327] The mass per unit area of the electrode was 0.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[3328] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 16 mm.
[3329] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0004 (kPas/m).
[3330] Additionally, the structure shown in FIG. 88 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
Example 4-37
[3331] In Example 4-37, the electrode produced in Example 4-35 was
used. As shown in FIG. 89, the 110 mm nickel line and the 95 mm
nickel line were placed such that the nickel lines vertically
overlapped each other at the center of each of the nickel lines and
bonded to each other at the intersection with Aron Alpha to produce
an electrode. The electrode was evaluated, and the results are
shown in Table 7.
[3332] The portion of the electrode at which the nickel lines
overlapped had the largest thickness, and the thickness of the
electrode was 306 .mu.m. The thickness of the catalytic layer was 6
.mu.m. The opening ratio was 98.8%.
[3333] The mass per unit area of the electrode was 1.9
(mg/cm.sup.2). The forces applied per unit massunit area (1) and
(2) were both equal to or less than the measurement lower limit of
the tensile testing machine. Thus, the result of evaluation of
winding around column of 280 mm in diameter (1) was less than 5%,
and the portions at which the electrode came off from the membrane
increased. The handling property was "4", which was also
problematic. The membrane damage was evaluated as "0".
[3334] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 14 mm.
[3335] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 0.001 (kPas/m) or less
under the measurement condition 2. When measured under the
measurement condition 2 with SENSE (measurement range) set at H
(high) of the ventilation resistance measurement apparatus, the
ventilation resistance was 0.0005 (kPas/m).
[3336] Additionally, the structure shown in FIG. 90 was used to
place the electrode (cathode) on the Ni mesh feed conductor, and
electrolytic evaluation of the electrode was performed by the
method described in (9) Electrolytic evaluation. As a result, the
voltage was as high as 3.18 V.
Comparative Example 4-1
(Preparation of Catalyst)
[3337] A metal salt aqueous solution was produced by adding 0.728 g
of silver nitrate (Wako Pure Chemical Industries, Ltd.) and 1.86 g
of cerium nitrate hexahydrate (Wako Pure Chemical Industries, Ltd.)
to 150 ml of pure water. An alkali solution was produced by adding
240 g of pure water to 100 g of a 15% tetramethylammonium hydroxide
aqueous solution (Wako Pure Chemical Industries, Ltd.). While the
alkali solution was stirred using a magnetic stirrer, the metal
salt aqueous solution was added thereto dropwise at 5 ml/minute
using a buret. A suspension containing the resulting metal
hydroxide particulates was suction-filtered and then washed with
water to remove the alkali content. Thereafter, the residue was
transferred into 200 ml of 2-propanol (KISHIDA CHEMICAL Co., Ltd.)
and redispersed by an ultrasonic dispersing apparatus (US-600T,
NISSEI Corporation) for 10 minutes to obtain a uniform
suspension.
[3338] A suspension of carbon black was obtained by dispersing 0.36
g of hydrophobic carbon black (DENKA BLACK(R) AB-7 (trade name),
Denka Company Limited) and 0.84 g of hydrophilic carbon black
(Ketjenblack(R) EC-600JD (trade name), Mitsubishi Chemical
Corporation) in 100 ml of 2-propanol and dispersing the mixture by
the ultrasonic dispersing apparatus for 10 minutes. The metal
hydroxide precursor suspension and the carbon black suspension were
mixed and dispersed by the ultrasonic dispersing apparatus for 10
minutes. This suspension was such and dried at room temperature for
half a day to obtain carbon black containing the metal hydroxide
precursor dispersed and fixed. Subsequently, an inert gas baking
furnace (VMF165 type, YAMADA DENKI CO., LTD.) was used to perform
baking in a nitrogen atmosphere at 400.degree. C. for an hour to
obtain carbon black A containing an electrode catalyst dispersed
and fixed.
(Production of Powder for Reaction Layer)
[3339] In 1.6 g of the carbon black A containing an electrode
catalyst dispersed and fixed, 0.84 ml of a surfactant Triton(R)
X-100(trade name, ICN Biomedicals) diluted to 20% by weight with
pure water and 15 ml of pure water, and the mixture was dispersed
by an ultrasonic dispersing apparatus for 10 minutes. To this
dispersion, 0.664 g of a polytetrafluoroethylene (PTFE) dispersion
(PTFE30J (trade name), Dupont-Mitsui Fluorochemicals Co., Ltd.) was
added. After the mixture was stirred for five minutes, suction
filtration was performed. Additionally, the residue was dried in a
dryer at 80.degree. C. for an hour, and pulverization was performed
by a mill to obtain a powder for reaction layer A.
(Production of Powder for Gas Diffusion Layer)
[3340] Dispersed were 20 g of hydrophobic carbon black (DENKA
BLACK(R) AB-7 (trade name)), 50 ml of a surfactant. Triton(R)
X-100(trade name) diluted to 20% by weight with pure water, and 360
ml of pure water by an ultrasonic dispersing apparatus for 10
minutes. To the resulting dispersion, 22.32 g of the PTFE
dispersion was added. The mixture was stirred for 5 minutes, and
then, filtration was performed. Additionally, the residue was dried
in a dryer at 80.degree. C. for an hour, and pulverization was
performed by a mill to obtain a powder for gas diffusion layer
A.
(Production of Gas Diffusion Electrode)
[3341] To 4 g of the powder for gas diffusion layer A, 8.7 ml of
ethanol was added, and the mixture was kneaded into a paste form.
This powder for gas diffusion layer in a paste form was formed into
a sheet form by a roll former. Silver mesh (SW=1, LW=2, and
thickness=0.3 mm) as the collector was embedded into the sheet and
finally formed into a sheet form having a thickness of 1.8 mm. To 1
g of the powder for reaction layer A, 2.2 ml of ethanol was added,
and the mixture was kneaded into a paste form. This powder for
reaction layer in a paste form was formed into a sheet form having
a thickness of 0.2 mm by a roll former. Additionally, the two
sheets, that is, the sheet obtained by using the powder for gas
diffusion layer A produced and the sheet obtained by using the
powder for reaction layer A were laminated and formed into a sheet
form having a thickness of 1.8 mm by a roll former. This laminated
sheet was dried at room temperature for a whole day and right to
remove ethanol. Further, in order to remove the remaining
surfactant, the sheet was subjected to a pyrolysis treatment in air
at 300.degree. C. for an hour. The sheet was wrapped in an aluminum
foil, and subjected to hot pressing by a hot pressing machine
(SA303 (trade name), TESTER SANGYO CO., LTD.) at 360.degree. C. and
50 kgf/cm.sup.2 for 1 minute to obtain a gas diffusion electrode.
The thickness of the gas diffusion electrode was 412 .mu.m.
[3342] The resulting electrode was used to perform electrolytic
evaluation. In the sectional structure of the electrolytic cell,
the collector, the mattress, the nickel mesh feed conductor, the
electrode, the membrane, and the anode are arranged in the order
mentioned from the cathode chamber side to form a zero-gap
structure. The results are shown in Table 7.
[3343] When a deformation test of the electrode was performed, the
average value of L.sub.1 and L.sub.2 was 19 mm.
[3344] When the ventilation resistance of the electrode was
measured, the ventilation resistance was 25.88 (kPas/m) under the
measurement condition 1.
[3345] The handling property was "3", which was problematic.
Additionally, when electrolytic evaluation was performed, the
current efficiency was low, the common salt concentration in
caustic soda was raised and the electrolytic performance markedly
deteriorated. The membrane damage, which was evaluated as "3", also
had a problem.
[3346] These results have revealed that the gas diffusion electrode
obtained in Comparative Example 4-1 had markedly poor electrolytic
performance. Additionally, damage was observed on the substantially
entire surface of the ion exchange membrane. It was conceived that
this is because NaOH that had been generated in the electrode
accumulated on the interface between the electrode and the membrane
to elevate the concentration thereof, due to the markedly high
ventilation resistance of the gas diffusion electrode of
Comparative Example 4-1.
TABLE-US-00006 TABLE 6 Substrate for Form of substrate Coating
electrode for electrode method Feed conductor Example 4-1 Ni
Punching Pyrolysis Ni mesh Example 4-2 Ni Punching Pyrolysis Ni
mesh Example 4-3 Ni Punching Pyrolysis Ni mesh Example 4-4 Ni
Punching Pyrolysis Ni mesh Example 4-5 Ni Punching Pyrolysis Ni
mesh Example 4-6 Ni Punching Ion plating Ni mesh Example 4-7 Ni
Electroforming Pyrolysis Ni mesh Example 4-8 Ni Electroforming
Pyrolysis Ni mesh Example 4-9 Ni Nonwoven fabric Pyrolysis Ni mesh
Example 4-10 Ni Nonwoven fabric Pyrolysis Ni mesh Example 4-11 Ni
Foamed Ni Pyrolysis Ni mesh Example 4-12 Ni Mesh Pyrolysis Ni mesh
Example 4-13 Ni Mesh Pyrolysis Ni mesh Example 4-14 Ni Punching
(same Pyrolysis Mattress as in Example 4-3) Example 4-15 Ni
Punching (same Pyrolysis Cathode having increase in voltage as in
Example 4-3) Example 4-16 Ti Punching Pyrolysis Anode having
increase in voltage Example 4-17 Ti Punching Pyrolysis Anode having
increase in voltage Example 4-18 Ti Punching Pyrolysis Anode having
increase in voltage Example 4-19 Ti Punching Pyrolysis Anode having
increase in voltage Example 4-20 Ti Nonwoven fabric Pyrolysis Anode
having increase in voltage Example 4-21 Ti Mesh Pyrolysis Anode
having increase in voltage Example 4-22 Ni/Ti Combination of
Pyrolysis Cathode and anode having increase in voltage Example 4-3
and Example 4-20 Example 4-23 Ni Punching Pyrolysis -- Example 4-24
Ni Expanded Pyrolysis Ni mesh Example 4-25 Ni Expanded Pyrolysis Ni
mesh Example 4-26 Ni Expanded Ion plating Ni mesh Example 4-27 Ni
Expanded Pyrolysis Ni mesh Example 4-28 Ni Mesh Pyrolysis Ni mesh
Example 4-29 Ni Mesh Pyrolysis Ni mesh Example 4-30 Ti Expanded
Pyrolysis Anode having increase in voltage Example 4-31 Ti Expanded
Pyrolysis Anode having increase in voltage Example 4-32 Ti Expanded
Pyrolysis Anode having increase in voltage Example 4-33 Ni Expanded
Pyrolysis Ni mesh Example 4-34 Ni Mesh Pyrolysis Ni mesh Example
4-35 Ni Mesh Pyrolysis Ni mesh Example 4-36 Ni Mesh Pyrolysis Ni
mesh Example 4-37 Ni Mesh Pyrolysis Ni mesh Comparative Carbon
Powder Pyrolysis Ni mesh Example 4-1
TABLE-US-00007 TABLE 7 Thickness of substrate for electrode for
Thickness of Thickness Mass per Force applied per unit electrolysis
electrode of catalytic Opening ratio unit area mass unit area (1)
(.mu.m) (.mu.m) layer (.mu.m) (void ratio) % (mg/cm.sup.2) (N/mg
cm.sup.2-electrode) Example 4-1 16 24 8 49 5.8 0.90 Example 4-2 22
29 7 44 9.9 0.61 Example 4-3 30 38 8 44 11.1 0.43 Example 4-4 16 24
8 75 3.5 0.28 Example 4-5 20 30 10 49 6.4 0.59 Example 4-6 16 26 10
49 6.2 0.81 Example 4-7 20 37 17 56 8.1 0.79 Example 4-8 50 60 10
56 18.1 0.13 Example 4-9 150 165 15 76 31.9 0.22 Example 4-10 200
215 15 72 46.3 0.12 Example 4-11 200 210 10 72 36.5 0.13 Example
4-12 100 110 10 37 27.4 0.18 Example 4-13 130 133 3 38 36.3 0.15
Example 4-14 30 38 8 44 11.1 0.43 Example 4-15 30 38 8 44 11.1 0.43
Example 4-16 20 26 5 14 8.9 0.16 Example 4-17 20 30 10 30 8.1 0.26
Example 4-18 20 32 12 42 6.6 0.24 Example 4-19 50 69 19 47 12.9
0.12 Example 4-20 100 114 14 78 11.3 0.59 Example 4-21 120 140 20
42 14.9 0.47 Example 4-22 30/100 38/114 8/14 44/78 11.1/11.3
0.43/0.59 Example 4-23 30 38 8 44 11.1 0.28 Example 4-24 100 114 14
33 67.5 0.05 Example 4-25 100 107 7 16 78.1 0.04 Example 4-26 100
110 10 40 37.8 0.07 Example 4-27 100 109 9 58 39.2 0.06 Example
4-28 300 308 8 56 49.2 0.18 Example 4-29 200 210 10 37 56.4 0.09
Example 4-30 500 508 8 17 152.5 0.01 Example 4-31 800 808 8 8 251.3
0.01 Example 4-32 1000 1011 11 46 245.5 0.01 Example 4-33 100 114
14 33 67.5 1.50 Example 4-34 300 308 8 58 49.2 1.80 Example 4-35
300 306 6 99 0.5 Equal to or less than the measurement lower limit
Example 4-36 300 306 10 99 0.9 Equal to or less than the
measurement lower limit Example 4-37 300 306 15 99 1.9 Equal to or
less than the measurement lower limit Comparative Example 4-1 412
412 -- -- 101 0.005 Method for Method for Method for evaluating
evaluating evaluating winding winding winding around around around
column of column of column of 280 mm in 145 mm in 280 mm in
diameter (2) diameter (3) diameter (1) (membrane (membrane Handing
Force applied per unit (membrane and and property mass unit area
(2) and column) electrode) electrode) (sensory (N/mg
cm.sup.2-electrode) (%) (%) (%) evaluation) Example 4-1 0.640 100
100 100 1 Example 4-2 0.235 100 100 100 1 Example 4-3 0.194 100 100
100 1 Example 4-4 0.113 100 100 100 1 Example 4-5 0.386 100 100 100
1 Example 4-6 0.650 100 100 100 1 Example 4-7 0.184 100 100 100 1
Example 4-8 0.088 100 100 100 1 Example 4-9 0.217 100 100 100 2
Example 4-10 0.081 100 100 79 2 Example 4-11 0.162 100 100 100 2
Example 4-12 0.126 100 100 100 1 Example 4-13 0.098 100 100 88 2
Example 4-14 0.194 100 100 100 1 Example 4-15 0.194 100 100 100 1
Example 4-16 0.105 100 100 100 1 Example 4-17 0.132 100 100 100 1
Example 4-18 0.147 100 100 100 1 Example 4-19 0.08 100 100 100 1
Example 4-20 0.378 100 100 100 1 Example 4-21 0.308 100 100 100 1
Example 4-22 0.194/0.378 100/100 100/100 100/100 1/1 Example 4-23
0.194 100 100 100 1 Example 4-24 0.045 100 64 22 4 Example 4-25
0.027 100 37 25 4 Example 4-26 0.045 100 80 32 3 Example 4-27 0.034
100 69 39 3 Example 4-28 0.138 100 88 42 3 Example 4-29 0.060 100
100 63 3 Example 4-30 0.005 100 Less than 5 Less than 5 4 Example
4-31 0.006 100 Less than 5 Less than 5 4 Example 4-32 0.005 100
Less than 5 Less than 5 4 Example 4-33 -- Less than 5 -- -- 3
Example 4-34 -- Less than 5 -- -- 3 Example 4-35 Equal to or less
than the Less than 5 -- -- 4 measurement lower limit Example 4-36
Equal to or less than the Less than 5 -- -- 4 measurement lower
limit Example 4-37 Equal to or less than the Less than 5 -- -- 4
measurement lower limit Comparative Example 4-1 0.005 Less than 5
-- -- 3 Elastic deformation test of electrode Electrolytic
evaluation (winding around Common salt vinyl chloride Ventilation
Ventilation concentration pipe of 32 mm in resistance resistance
Current in caustic soda outer diameter) (KPa s/m) (KPa s/m)
Membrane Voltage efficiency (ppm, on the average value of
(measurement (measurement damage (V) (%) basis of 50%) L.sub.1 and
L.sub.2 (mm) condition 1) condition 2) evaluation Example 4-1 2.98
97.7 15 0 0.07 or less 0.0028 .smallcircle. Example 4-2 2.95 97.2
18 0 0.07 or less 0.0033 .smallcircle. Example 4-3 2.96 97.6 19 0
0.07 or less 0.0027 .smallcircle. Example 4-4 2.97 97.5 15 0 0.07
or less 0.0023 .smallcircle. Example 4-5 2.95 97.1 18 0 0.07 or
less 0.0023 .smallcircle. Example 4-6 2.96 97.3 14 0 0.07 or less
0.0028 .smallcircle. Example 4-7 2.96 97.3 15 0 0.07 or less 0.0032
.smallcircle. Example 4-8 2.96 97.7 16 0 0.07 or less 0.0032
.smallcircle. Example 4-9 2.97 96.8 23 29 0.07 or less 0.0612
.smallcircle. Example 4-10 2.96 96.7 26 40 0.07 or less 0.0154
.smallcircle. Example 4-11 3.05 97.4 22 17 0.07 or less 0.0402
.smallcircle. Example 4-12 3.11 97.2 23 0.5 0.07 or less 0.0154
.smallcircle. Example 4-13 3.09 97.0 25 5.5 0.07 or less 0.0124
.smallcircle. Example 4-14 2.97 97.3 18 0 0.07 or less 0.0027
.smallcircle. Example 4-15 2.96 97.2 21 0 0.07 or less 0.0027
.smallcircle. Example 4-16 3.10 96.8 19 4 0.07 or less 0.0060
.smallcircle. Example 4-17 3.07 96.8 26 5 0.07 or less 0.0030
.smallcircle. Example 4-18 3.08 97.7 21 2.5 0.07 or less 0.0022
.smallcircle. Example 4-19 3.09 97.0 21 8 0.07 or less 0.0024
.smallcircle. Example 4-20 2.97 96.8 24 2 0.07 or less 0.0228
.smallcircle. Example 4-21 2.99 97.0 18 10 0.07 or less 0.0132
.smallcircle. Example 4-22 3.00 97.2 17 0/2 0.07 or less
0.0027/0.0228 .smallcircle. Example 4-23 -- -- -- 0 0.07 or less
0.0027 .smallcircle. Example 4-24 2.98 97.7 19 13 0.07 or less
0.0168 .smallcircle. Example 4-25 2.99 97.8 17 18.5 0.07 or less
0.0176 .smallcircle. Example 4-26 2.96 97.5 18 11 0.07 or less
0.0030 .smallcircle. Example 4-27 2.99 97.6 18 11.5 0.07 or less
0.0028 .smallcircle. Example 4-28 2.95 97.5 24 23 0.07 or less
0.0034 .smallcircle. Example 4-29 2.98 97.3 23 19 0.07 or less
0.0096 .smallcircle. Example 4-30 2.99 96.7 23 Remained 0.07 or
less 0.0072 .smallcircle. Example 4-31 3.02 97.0 19 deformed in
0.07 or less 0.0172 .smallcircle. Example 4-32 3.00 97.2 20 vinyl
chloride 0.07 or less 0.0027 .smallcircle. form and did not return
Example 4-33 3.67 93.8 226 13 0.07 or less 0.0168 .smallcircle.
Example 4-34 3.71 94.5 155 23 0.07 or less 0.0034 .smallcircle.
Example 4-35 3.16 97.5 21 15 0.07 or less 0.0002 .smallcircle.
Example 4-36 3.18 97.4 19 16 0.07 or less 0.0004 .smallcircle.
Example 4-37 3.18 97.3 20 14 0.07 or less 0.0005 .smallcircle.
Comparative Example 4-1 3.65 48.0 680 19 25.88 -- x
[3347] In Table 7, all the samples were able to stand by themselves
by the surface tension before measurement of "force applied per
unit massunit area (1)" and "force applied per unit massunit area
(2)" (i.e., did not slip down).
<Verification of Fifth Embodiment>
[3348] As will be described below, Experiment Examples according to
the fifth embodiment (in the section of <Verification of fifth
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the fifth embodiment (in the
section of <Verification of fifth embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 93 to 94 and 100 to 102 as appropriate.
[3349] As the membrane, an ion exchange membrane A produced as
described below was used.
[3350] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTFE) were used (hereinafter
referred to as PTFE yarns). As the sacrifice yarns, yarns obtained
by twisting, six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[3351] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin B of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[3352] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[3353] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for minutes, and then the release paper was
removed to obtain a composite membrane.
[3354] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour to replace the counterion of
the ion exchange group by Na, and then washed with water. Then, the
membrane was dried at 60.degree. C.
[3355] Further, 20% by mass of zirconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. Here, the average particle size was measured by a
particle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[3356] As the electrode, a cathode and an anode below were
used.
[3357] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 22 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.95
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[3358] A porous foil was formed by perforating this nickel foil
with circular holes by punching. The opening ratio was 44%.
[3359] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA. METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[3360] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced was 9 .mu.m. The thickness
of the catalytic layer containing ruthenium oxide and cerium oxide,
which was determined by subtracting the thickness of the substrate
for electrode for electrolysis from the thickness of the electrode,
was 7 .mu.m. The coating was formed also on the surface not
roughened.
[3361] A titanium nonwoven fabric having a gauge thickness of 100
.mu.m, a titanium fiber diameter of about 20 .mu.m, a basis weight
of 100 g/m.sup.2, and an opening ratio of 78% was used as the
substrate for electrode for anode electrolysis.
[3362] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[3363] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (E=1)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a chloride
(PVC) cylinder was always in contact with the coating liquid. A
coating roll around which the same EPDM had been wound was placed
at the upper portion thereof, and PVC roller was further placed
thereabove. The coating liquid was applied by allowing the
substrate for electrode to pass between the second coating roll and
the PVC roller at the uppermost portion (roll coating method).
After the above coating liquid was applied onto the titanium porous
foil, drying at 60.degree. C. for 10 minutes, and baking at
475.degree. C. for 10 minutes were performed. A series of these
coating, drying, preliminary baking, and baking operations was
repeatedly performed, and then baking at 520.degree. C. was
performed for an hour.
Example 5-1
(Example of Use of Cathode-Membrane Laminate)
[3364] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1.5 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four cathodes having a size of 0.3 m in length and
2.4 m in width were provided in accordance with the method
mentioned above.
[3365] After the ion exchange membrane was immersed in a 2% sodium
bicarbonate solution for a whole day and night, the cathodes were
arranged without any gap on the carboxylic acid layer side of the
ion exchange membrane to produce a laminate of the cathodes and the
ion exchange membrane (see FIG. 100). When the cathodes were placed
on the membrane, the contact with the sodium bicarbonate aqueous
solution caused surface tension to function, and the cathodes and
the membrane were integrated as if they stick together. No pressure
was applied for such integration. The temperature at the
integration was 23.degree. C. The resulting laminate was wound
around a polyvinyl chloride (PVC) pipe having an outer diameter of
76 mm and a length of 1.7 m as shown in FIG. 101 to produce a wound
body. The wound body was in a cylindrical form having an outer
diameter of 84 mm and a length of 1.7 m, and it was possible to
downsize the laminate.
[3366] Next, in an existing large electrolyzer (electrolyzer having
a structure similar to those shown in FIGS. 93 and 94), a fixed
state of the adjacent electrolytic cells and the ion exchange
membrane by means of a press device was released, and the existing
membrane was removed out to provide a gap between the electrolytic
cells. Thereafter, the wound body was conveyed onto the large
electrolyzer. On the large electrolyzer, while the PVC pipe was
upright, the wound state was released so as to pull out the wound
laminate. At this time, the laminate was maintained substantially
vertically to the ground, but the cathode did not come off. Then,
after the laminate was inserted between the electrolytic cells, the
electrolytic cells were moved to sandwich the laminate
therebetween.
[3367] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell when a laminate wound body is
provided in advance during the electrolytic operation.
Example 5-2
(Example of Use of Anode-Membrane Laminate)
[3368] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1.5 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four anodes having a size of 0.3 m in length and 2.4
m in width were provided in accordance with the method mentioned
above.
[3369] After the ion exchange membrane was immersed in a 2% sodium
bicarbonate solution for a whole day and night, the anodes were
arranged without any gap on the sulfonic acid layer side in the
same manner as in Example 5-1 to produce a laminate of the anodes
and the ion exchange membrane. When the anodes were placed on the
membrane, the contact with the sodium bicarbonate aqueous solution
caused surface tension to function, and the anodes and the membrane
were integrated as if they stick together. No pressure was applied
for such integration. The temperature at the integration was
23.degree. C. The resulting laminate was wound around a polyvinyl
chloride (PVC) pipe having an outer diameter of 76 .mu.m and a
length of 1.7 m to produce a wound body in the same manner as in
Example 5-1. The wound body was in a cylindrical form having an
outer diameter of 86 mm and a length of 1.7 m, and it was possible
to downsize the laminate.
[3370] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 5-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound laminate. At this time,
the laminate was maintained substantially vertically to the ground,
but the anode did not come off. Then, after the laminate was
inserted between the electrolytic cells, the electrolytic cells
were moved to sandwich the laminate therebetween.
[3371] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell when a laminate wound body is
provided in advance during the electrolytic operation.
Example 5-3
(Example of Use of Anode/Cathode-Membrane Laminate)
[3372] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1.5 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four anodes and four cathodes each having a size of
0.3 m in length and 2.4 m in width were provided in accordance with
the method mentioned above.
[3373] After the ion exchange membrane was immersed in a 2% sodium
bicarbonate solution for a whole day and night, the cathodes were
arranged on the carboxylic acid layer side and the anodes were
arranged on the sulfonic acid layer side without any gap in the
same manner as in Example 5-1 to produce a laminate of the
cathodes, the anodes, and the ion exchange membrane. When the
cathodes and the anodes were placed on the membrane, the contact
with the sodium bicarbonate aqueous solution caused surface tension
to function, and the cathodes, the anodes, and the membrane were
integrated as if they stick together. No pressure was applied for
such integration. The temperature at the integration was 23.degree.
C. The resulting laminate was wound around a polyvinyl chloride
(PVC) pipe having an outer diameter of 76 mm and a length of 1.7 m
to produce a wound body in the same manner as in Example 5-1. The
wound body was in a cylindrical form having an outer diameter of 88
mm and a length of 1.7 m, and it was possible to downsize the
laminate.
[3374] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 5-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was, upright, the wound
state was released so as to pull out the wound laminate. At this
time, the laminate was maintained substantially vertically to the
ground, but the anode lid not come off. Then, after the laminate
was inserted between the electrolytic cells, the electrolytic cells
were moved to sandwich the laminate therebetween.
[3375] It was possible to replace the electrode and the membrane
easer than in conventional ones. It was judged that renewing of the
electrode and replace of the membrane can be completed in several
tens of minutes per one cell when a laminate wound body is provided
in advance during the electrolytic operation.
Example 5-4
(Example of Use of Cathodes)
[3376] A wound body was prod iced in advance as follows. First,
four cathodes having a size of 0.3 m in length and 2.4 m in width
were provided in accordance with the method mentioned above. The
four cathodes were arranged without any gap so as to achieve a size
of 1.2 m in length and 2.4 in width. Adjacent cathodes were tied
together and fixed such that the cathodes were not separated by
threading a PTFE string through openings of each cathode (not
shown) as shown in FIG. 102. In the operation, no pressure was
applied, and the temperature was 23.degree. C. These cathodes were
wound around a polyvinyl chloride (PVC) pipe having an outer
diameter of 76 mm and a length of 1.7 m to produce a wound body in
the same manner as in Example 5-1. The wound body was in a
cylindrical form having an outer diameter of 78 mm and a length of
1.7 m, and it was possible to downsize the laminate.
[3377] Next in an existing large electrolyzer (electrolyzer similar
to that in Example 5-1), a fixed state of the adjacent electrolytic
cells and the ion exchange membrane by means of a press device was
released, and the existing membrane was removed out to provide a
gap between the electrolytic cells. Thereafter, the wound body was
conveyed onto the large electrolyzer. On the large electrolyzer,
while the PVC pipe was upright, the wound state was released so as
to pull out the wound cathodes. At this time, the cathodes were
maintained substantially vertically to the ground, but the cathodes
did not come off. Then, after the cathodes were inserted between
the electrolytic cells, the electrolytic cells were moved to
sandwich the laminate therebetween.
[3378] It was possible to replace cathodes easier than in
conventional ones. It was judged that renewing of the cathodes can
be completed in several tens of minutes per one cell when a cathode
wound body is provided in advance during the electrolytic
operation.
Example 5-5
(Example of Use of Anodes)
[3379] A wound body was produced in advance as follows.
[3380] First, four anodes having a size of 0.3 m in length and 2.4
m in width were provided in accordance with the method mentioned
above. The four anodes were arranged without any gap so as to
achieve a size of 1.2 m in length and 2.4 in width. Adjacent anodes
were tied together with a PTFE string and fixed such that the
anodes were not separated, in the same manner as in Example 5-4. In
the operation, no pressure was applied, and the temperature was
23.degree. C. These anodes were wound around a polyvinyl chloride
(PVC) pipe having an outer diameter of 76 mm and a length of 1.7 m
to produce a wound body in the same manner as in Example 5-1. The
wound body was in a cylindrical form having an outer diameter of 81
mm and a length of 1.7 m, and it was possible to downsize the
laminate.
[3381] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 5-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound anodes. At this time, the
anodes were maintained substantially vertically to the ground, but
the anodes did not come off. Then, after the anodes were inserted
between the electrolytic cells, the electrolytic cells were moved
to sandwich the laminate therebetween.
[3382] It was possible to replace anodes easier than in
conventional ones. It was judged that renewing of the anodes can be
completed, in several tens of minutes per one cell when an anode
wound body is provided in advance during the electrolytic
operation.
Comparative Example 5-1
(Conventional Renewing of Electrode)
[3383] In an existing large electrolyzer (electrolyzer similar to
that in Example 5-1), a fixed state of the adjacent electrolytic
cells and the ion exchange membrane by means of a press device was
released, and the existing membrane was removed out to provide a
gap between the electrolytic cells. Thereafter, the electrolytic
cells were hoisted out from the large electrolyzer with a hoist.
The electrolytic cells removed were conveyed to a plant where
welding was available.
[3384] After the anode fixed by welding on the rib of the
electrolytic cell was stripped off, burrs or the like at the
portion from which the anode was stripped off with a grinder and so
on to smooth the portion. The cathode was stripped off by removing
the portion fixed by folding the portion into the collector.
[3385] Thereafter, a new anode was placed on the rib of the anode
chamber, and the new anode was fixed to the electrolytic cell by
spot welding. Similarly in the case of the cathode, a new cathode
was placed on the cathode side and fixed by folding the cathode
into the collector.
[3386] The renewed electrolytic cell was conveyed to the position
of the large electrolyzer, and the electrolytic cell was returned
is the electrolyzer using a hoist.
[3387] The period required from the release of the fixed state of
the electrolytic cell and the ion exchange membrane to the refixing
of the electrolytic cell was one day or more.
<Verification of Sixth Embodiment>
[3388] As will be described below, Experiment Examples according to
the sixth embodiment (in the section of <Verification of sixth
embodiment> hereinbelow, simply referred to as "Examples") and
Experiment Examples not according to the sixth embodiment (in the
section of <Verification of sixth embodiment> hereinbelow,
simply referred to as "Comparative Examples") were provided, and
evaluated by the following method. The details will be described
with reference to FIGS. 105 and 106 as appropriate.
[3389] As the membrane, an ion exchange membrane b produced as
described below was used.
[3390] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTE were used (hereinafter
referred to as PTFE yarns). As the sacrifice yarns, yarns obtained
by twisting six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
two sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[3391] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/g, and a
resin B of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[3392] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[3393] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[3394] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour to replace the counterion of
the ion exchange group by Na, and then washed with water. Then, the
membrane was dried at 60.degree. C.
[3395] Further, 20% by mass of zirconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. Here, the average particle size was measured by a
particle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[3396] As the electrode, a cathode and an anode below were
used.
[3397] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 22 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.95
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[3398] A porous foil was formed by perforating this nickel foil
with circular holes by punching. The opening ratio was 44%.
[3399] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium nitrate
solution having a ruthenium concentration of 100 g/L (FURUYA METAL
Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were
mixed such that the molar ratio between the ruthenium element and
the cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[3400] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). Then, after drying at 50.degree. C. for 10
minutes, preliminary baking at 150.degree. C. for 3 minutes, and
baking at 350.degree. C. for 10 minutes were performed. A series of
these coating, drying, preliminary baking, and baking operations
was repeated until a predetermined amount of coating was achieved.
The thickness of the electrode produced was 29 .mu.m. The thickness
of the catalytic layer containing ruthenium oxide and cerium oxide,
which was determined by subtracting the thickness of the substrate
for electrode for electrolysis from the thickness or the electrode,
was 7 .mu.m. The coating was formed also on the surface not
roughened.
[3401] A titanium nonwoven fabric having a gauge thickness of 100
.mu.m, a titanium fiber diameter of about 20 .mu.m, a basis weight
of 100 .mu.m.sup.2, and an opening ratio of 78% was used as the
substrate for electrode for anode electrolysis.
[3402] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[3403] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roil formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). After the above coating liquid was applied onto
the titanium porous foil, drying at 60.degree. C. for 10 minutes,
and baking at 475.degree. C. for 10 minutes were performed. A
series of these coating, drying, preliminary baking, and baking
operations was repeatedly performed, and then baking at 520.degree.
C. was performed for an hour.
Example 6-1
(Example of Use of Cathode-Membrane Laminate)
[3404] A wound body was produced in advance as follows. First, an
ion exchange membrane b having a size of 1.5 m in length and 2.5 m
in width was provided in accordance with the method mentioned
above. Additionally, four cathodes having a size of 0.3 m in length
and 2.4 m in width were provided in accordance with the method
mentioned above.
[3405] After the ion exchange membrane b was immersed in a 2%
sodium bicarbonate solution for a whole day and night, the cathodes
were arranged without any gap on the carboxylic acid layer side of
the ion exchange membrane to produce a laminate of the cathodes and
the ion exchange membrane b. When the cathodes were placed on the
membrane, the contact with the sodium bicarbonate aqueous solution
caused surface tension to function, and the cathodes and the
membrane were integrated as if they stick together. No pressure was
applied for such integration. The temperature at the integration
was 23.degree. C. This laminate was wound around a polyvinyl
chloride (PVC) pipe having an outer diameter of 76 mm and a length
of 1.7 m to produce a wound body. In order to melt the ion exchange
membrane b, a temperature of 200.degree. C. or more is required. In
the present example, the ion exchange membrane did not melt during
integration.
[3406] Next, in an existing large electrolyzer (electrolyzer having
a structure similar to those shown in FIGS. 105 and 106), a fixed
state of the adjacent electrolytic cells and the ion exchange
membrane by means of a press device was released, and the existing
membrane was removed out to provide a gap between the electrolytic
cells. Thereafter, the wound body was conveyed onto the large
electrolyzer. On the large electrolyzer, while the PVC pipe was
upright, the wound state was released so as to pull out the wound
laminate. At this time, the laminate was maintained substantially
vertically to the ground, but the cathode did not come off. Then,
after the laminate was inserted between the electrolytic cells, the
electrolytic cells were moved to sandwich the laminate
therebetween.
[3407] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell.
Example 6-2
(Example of Use of Anode-Membrane Laminate)
[3408] A wound body was produced in advance as follows. First, an
ion exchange membrane b having a size of 1.5 m in length and 2.5 m
in width was provided in accordance with the method mentioned
above. Additionally, four anodes having a size of 0.3 m in length
and 2.4 m in width were provided in accordance with the method
mentioned above.
[3409] After the ion exchange membrane b was immersed in a 2%
sodium bicarbonate solution for a whole day and night, the anodes
were arranged without any gap on the sulfonic acid layer side of
the ion exchange membrane to produce a laminate of the anodes and
the ion exchange membrane. When the anodes were placed on the
membrane, the contact with the sodium bicarbonate aqueous solution
caused surface tension to function, and the anodes and the membrane
were integrated as if they stick together. No pressure was applied
for such integration. The temperature at the integration was
23.degree. C. This laminate was wound around a polyvinyl chloride
(PVC) pipe having an outer diameter of 76 mm and a length of 1.7 m
to produce a wound body.
[3410] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 6-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound laminate. At this time,
the laminate was maintained substantially vertically to the ground,
but the anode did not come off. Then, after the laminate was
inserted between the electrolytic cells, the electrolytic cells
were moved to sandwich the laminate therebetween.
[3411] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell.
Example 6-3
(Example of Use of Anode/Cathode-Membrane Laminate)
[3412] A wound body was produced in advance as follows. First, an
ion exchange membrane b having a size of 1.5 m in length and 2.5 m
in width was provided in accordance with the method mentioned
above. Additionally, four anodes and four cathodes each having a
size of 0.3 m in length and 2.4 m in width were provided in
accordance with the method mentioned above.
[3413] After the ion exchange membrane b was immersed in a 2%
sodium bicarbonate solution for a whole day and night, the cathodes
were arranged on the carboxylic acid layer side of the ion exchange
membrane and the anodes were arranged on the sulfonic acid layer
side of the ion exchange membrane without any gap to produce a
laminate of the cathodes, the anodes, and the ion exchange membrane
b. When the cathodes and the anodes were placed on the membrane,
the contact with the sodium bicarbonate aqueous solution caused
surface tension to function, and the cathodes, the anodes, and the
membrane were integrated as if they stick together. No pressure was
applied for such integration. The temperature at the integration
was 23.degree. C. This laminate was wound around a polyvinyl
chloride (PVC) pipe having an outer diameter of 76 mm and a length
of 1.7 m to produce a wound body.
[3414] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 6-1) a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound laminate. At this time,
the laminate was maintained substantially vertically to the ground,
but the anode did not come off. Then, after the laminate was
inserted between the electrolytic cells, the electrolytic cells
were moved to sandwich the laminate therebetween.
[3415] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell.
Comparative Example 6-1
[3416] A membrane electrode laminate was produced by thermally
compressing an electrode onto a membrane as follows, with reference
to Examples of Japanese Patent Laid-Open No. 58-48686.
[3417] A nickel expanded metal having a gauge thickness of 100
.mu.m and an opening ratio of 33% was used as the substrate for
electrode for cathode electrolysis to perform electrode coating in
the same manner as in Example 6-1. The electrode had a size of 200
mm.times.200 mm, and the number of the electrodes was 72.
Thereafter, one surface of each electrode was subjected to an
inactivation treatment in the following procedure. Polyimide
adhesive tape (Chukoh Chemical Industries, Ltd.) was attached to
one surface of the electrodes. A PTFE dispersion (Dupont-Mitsui
Fluorochemicals Co., Ltd., 31-JR (trade name)) was applied onto the
other surface and dried in a muffle furnace at 120.degree. C. for
10 minutes. The polyimide tape was peeled off, and a sintering
treatment was performed in a muffle furnace set at 380.degree. C.
for 10 minutes. This operation was repeated twice to inactivate the
one surface of the electrodes.
[3418] Produced was a membrane formed by two layers of a
perfluorocarbon polymer of which terminal functional group is
"--COOCH.sub.3" (C polymer) and a perfluorocarbon polymer of which
terminal group is "--SO.sub.2F" (S polymer). The thickness of the C
polymer layer was 3 mils, and the thickness of the S polymer layer
was 4 mils. This two-layer membrane was subjected to a
saponification treatment to thereby introduce ion exchange groups
to the terminals of the polymer by hydrolysis. The C polymer
terminals were hydrolyzed into carboxylic acid groups and the S
polymer terminals into sulfo groups. The ion exchange capacity as
the sulfonic acid group was 1.0 meq/g, and the ion exchange
capacity as the carboxylic acid group was 0.9 meg/g. The size of
the resulting ion exchange membrane was similar to that in Example
6-1.
[3419] The inactivated electrode surface of the above electrode was
oppositely disposed to and thermally pressed (thermally compressed)
onto the surface having carboxylic acid groups as the ion exchange
groups to integrate the ion exchange membrane and the electrodes.
That is, under a temperature at which the ion exchange membrane
melted, the 12 electrodes of 200 mm square were integrated onto one
ion exchange membrane having a size of 1500 mm in length and 2500
mm in width. The one surface of each electrode was exposed even
after the thermal compression, and the electrodes passed through no
portion of the membrane.
[3420] For the large size of 1500 mm.times.2500 mm, a period of one
day or more was required for the process of integrating the ion
exchange membrane and the electrodes via thermal compression. That
is, it was judged that Comparative Example 6-1 required a longer
period for renewing of the electrode and replacement of the
membrane than in Examples.
<Verification of Seventh Embodiment>
[3421] As will be described below, Experiment Examples according to
the seventh embodiment (in the section of <Verification of
seventh embodiment> hereinbelow, simply referred to as
"Examples") and Experiment Examples not according to the seventh
embodiment (in the section of <Verification of seventh
embodiment> hereinbelow, simply referred to as "Comparative
Examples") were provided, and evaluated by the following method.
The details will be described with reference to FIGS. 114 and 115
as appropriate.
[3422] As the membrane, an ion exchange membrane produced as
described below was used.
[3423] As reinforcement core materials, 90 denier monofilaments
made of polytetrafluoroethylene (PTFE) were used (hereinafter
referred to as PTFE yarns). As the sacrifice yarns, yarns obtained
by twisting six 35 denier filaments of polyethylene terephthalate
(PET) 200 times/m were used (hereinafter referred to as PET yarns).
First, in each of the TD and the MD, the PTFE yarns and the
sacrifice yarns were plain-woven with 24 PTFE yarns/inch so that
two sacrifice yarns were arranged between adjacent PTFE yarns, to
obtain a woven fabric. The resulting woven fabric was
pressure-bonded by a roll to obtain a woven fabric having a
thickness of 70 .mu.m.
[3424] Next, a resin A of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2COOCH.sub.3
and had an ion exchange capacity of 0.85 mg equivalent/q, and a
resin B of a dry resin that was a copolymer of
CF.sub.2.dbd.CF.sub.2 and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
had an ion exchange capacity of 1.03 mg equivalent/g were
provided.
[3425] Using these resins A and B, a two-layer film X in which the
thickness of a resin A layer was 15 .mu.m and the thickness of a
resin B layer was 104 .mu.m was obtained by a coextrusion T die
method.
[3426] Subsequently, release paper (embossed in a conical shape
having a height of 50 .mu.m), a reinforcing material, and the film
X were laminated in this order on a hot plate having a heat source
and a vacuum source inside and having micropores on its surface,
heated and depressurized under the conditions of a hot plate
surface temperature of 223.degree. C. and a degree of reduced
pressure of 0.067 MPa for 2 minutes, and then the release paper was
removed to obtain a composite membrane.
[3427] The resulting composite membrane was immersed in an aqueous
solution at 80.degree. C. comprising 30% by mass of dimethyl
sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for
20 minutes for saponification. Then, the composite membrane was
immersed in an aqueous solution at 50.degree. C. comprising 0.5 N
sodium hydroxide (NaOH) for an hour to replace the counterion of
the ion exchange group by Na, and then washed with water. Then, the
membrane was dried at 60.degree. C.
[3428] Further, 20% by mass of zirconium oxide having a primary
particle size of 1 .mu.m was added to a 5% by mass ethanol solution
of the acid-type resin of the resin B and dispersed to prepare a
suspension, and the suspension was sprayed onto both the surfaces
of the above composite membrane by a suspension spray method to
form coatings of zirconium oxide on the surfaces of the composite
membrane to obtain an ion exchange membrane A. The coating density
of zirconium oxide measured by fluorescent X-ray measurement was
0.5 mg/cm.sup.2. Here, the average particle size was measured by a
particle size analyzer (manufactured by SHIMADZU CORPORATION,
"SALD(R) 2200").
[3429] As the electrode, a cathode and an anode below were
used.
[3430] As a substrate for electrode for cathode electrolysis, an
electrolytic nickel foil having a gauge thickness of 22 .mu.m was
provided. One surface of this nickel foil was subjected to a
roughening treatment by means of electrolytic nickel plating. The
arithmetic average roughness Ra of the roughened surface was 0.95
.mu.m. The measurement of the surface roughness was performed under
the same conditions as for the surface roughness measurement of the
nickel plate subjected to the blast treatment.
[3431] A porous foil was formed by perforating this nickel foil
with circular holes by punching. The opening ratio was 44%.
[3432] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure ruthenium nitrate solution
having a ruthenium concentration of 100 g/L (FURUYA METAL Co.,
Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed
such that the molar ratio between the ruthenium element and the
cerium element was 1:0.25. This mixed solution was sufficiently
stirred and used as a cathode coating liquid.
[3433] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roll around which the same EPDM had been wound
was placed at the upper portion thereof, and PVC roller was further
placed thereabove. The coating liquid was applied by allowing the
substrate for electrode to pass between the second coating roll and
the PVC roller at the uppermost portion (roll coating method).
Then, after drying at 50.degree. C. for 10 minutes, preliminary
baking at 150.degree. C. for 3 minutes, and baking at 350.degree.
C. for 10 minutes were performed. A series of these coating,
drying, preliminary baking, and baking operations was repeated
until a predetermined amount of coating was achieved. The thickness
of the electrode produced was 29 .mu.m. The thickness of the
catalytic layer containing ruthenium oxide and cerium oxide, which
was determined by subtracting the thickness of the substrate for
electrode for electrolysis from the thickness of the electrode, was
7 .mu.m. The coating was formed also on the surface not
roughened.
[3434] A titanium nonwoven fabric having a gauge thickness of 100
.mu.m, a titanium fiber diameter of about 20 .mu.m, a basis weight
of 100 g/m.sup.2, and an opening ratio of 78% was used as the
substrate for electrode for anode electrolysis.
[3435] A coating liquid for use in forming an electrode catalyst
was prepared by the following procedure. A ruthenium chloride
solution having a ruthenium concentration of 100 g/L (Tanaka
Kikinzoku Kogyo K.K.), iridium chloride having an iridium
concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.), and
titanium tetrachloride (Wako Pure Chemical Industries, Ltd.) were
mixed such that the molar ratio among the ruthenium element, the
iridium element, and the titanium element was 0.25:0.25:0.5. This
mixed solution was sufficiently stirred and used as an anode
coating liquid.
[3436] A vat containing the above coating liquid was placed at the
lowermost portion of a roll coating apparatus. The vat was placed
such that a coating roll formed by winding rubber made of
closed-cell type foamed ethylene-propylene-diene rubber (EPDM)
(INOAC CORPORATION, E-4088, thickness 10 mm) around a polyvinyl
chloride (PVC) cylinder was always in contact with the coating
liquid. A coating roil around which the same EPDM had been wound
was placed at the upper portion thereof, and a PVC roller was
further placed thereabove. The coating liquid was applied by
allowing the substrate for electrode to pass between the second
coating roll and the PVC roller at the uppermost portion (roll
coating method). After the above coating liquid was applied onto
the titanium porous foil, drying at 60.degree. C. for 10 minutes,
and baking at 475.degree. C. for 10 minutes were performed. A
series of these coating, drying, preliminary baking, and baking
operations was repeatedly performed, and then baking at 520.degree.
C. was performed for an hour.
Example 7-1
(Example of Use of Cathode-Membrane Laminate)
[3437] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1.5 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four cathodes having a size of 0.3 m in length and
2.4 m in width were provided in accordance with the method
mentioned above.
[3438] After the ion exchange membrane was immersed in a 2% sodium
bicarbonate solution for a whole day and night, the cathodes were
arranged without any gap on the carboxylic acid layer side of the
ion exchange membrane to produce a laminate of the cathodes and the
ion exchange membrane. When the cathodes were placed on the
membrane, the contact with the sodium bicarbonate aqueous solution
caused surface tension to function, and the cathodes and the
membrane were integrated as if they stick together. No pressure was
applied for such integration. The temperature at the integration
was 23.degree. C. This laminate was wound around a polyvinyl
chloride (PVC) pipe having an outer diameter of 76 mm and a length
of 1.7 m to produce a wound body.
[3439] Next, in an existing large electrolyzer (electrolyzer having
a structure similar to those shown in FIGS. 114 and 115), a fixed
state of the adjacent electrolytic cells and the ion exchange
membrane by means of a press device was released, and the existing
membrane was removed out to provide a gap between the electrolytic
cells. Thereafter, the wound body was conveyed onto the large
electrolyzer. On the large electrolyzer, while the PVC pipe was
upright, the wound state was released so as to pull out the wound
laminate. At this time, the laminate was maintained substantially
vertically to the ground, but the cathode did not come off. Then,
after the laminate was inserted between the electrolytic cell the
electrolytic cells were moved to sandwich the laminate
therebetween.
[3440] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell when a laminate wound body is
provided in advance during the electrolytic operation.
Example 7-2
(Example of Use of Anode-Membrane Laminate)
[3441] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four anodes having a size of 0.3 m in length and 2.4
m in width were provided in accordance with the method mentioned
above.
[3442] After the ion exchange membrane was immersed In a 2% sodium
bicarbonate solution for a whole day and night, the anodes were
arranged without any gap on the sulfonic acid layer side of the ion
exchange membrane to produce a laminate of the anodes and the ion
exchange membrane. When the anodes were placed on the membrane, the
contact with the sodium bicarbonate aqueous solution caused surface
tension to function, and the anodes and the membrane were
integrated as if they stick together. No pressure was applied for
such integration. The temperature at the integration was 23.degree.
C. This laminate was wound around a polyvinyl chloride (PVC) pipe
having an outer diameter of 76 mm and a length of 1.7 m to produce
a wound body.
[3443] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 7-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a cap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound laminate. At this time,
the laminate was maintained substantially vertically to the ground,
but the anode did not come off. Then, after the laminate was
inserted between the electrolytic cells, the electrolytic cells
were moved to sandwich the laminate therebetween.
[3444] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell when a laminate wound body is
provided in advance during the electrolytic operation.
Example 7-3
(Example of Use of Anode/Cathode-Membrane Laminate)
[3445] A wound body was produced in advance as follows. First, an
ion exchange membrane having a size of 1.5 m in length and 2.5 m in
width was provided in accordance with the method mentioned above.
Additionally, four anodes and four cathodes each having a size of
0.3 m in length and 2.4 m in width were provided in accordance with
the method mentioned above.
[3446] After the ion exchange membrane was immersed in a 2% sodium
bicarbonate solution for a whole day and night, the cathodes were
arranged on the carboxylic acid layer side of the ion exchange
membrane and the anodes were arranged on the sulfonic acid layer
side of the ion exchange membrane without any gap to produce a
laminate of the cathodes, the anodes, and the ion exchange
membrane. When the cathodes and the anodes were placed on the
membrane, the contact with the sodium bicarbonate aqueous solution
caused surface tension to function, and the cathodes, the anodes,
and the membrane were integrated as if they stick together. No
pressure was applied for such integration. The temperature at the
integration was 23.degree. C. This laminate was wound around a
polyvinyl chloride (PVC) pipe having an outer diameter of 76 mm and
a length of 1.7 m to produce a wound body.
[3447] Next in an existing large electrolyzer (electrolyzer similar
to that in Example 7-1), a fixed state of the adjacent electrolytic
cells and the ion exchange membrane by means of a press device was
released, and the existing membrane was removed out to provide a
gap between the electrolytic cells. Thereafter, the wound body was
conveyed onto the large electrolyzer. On the large electrolyzer,
while the PVC pipe was upright, the wound state was released so as
to pull out the wound laminate. At this time, the laminate was
maintained substantially vertically to the ground, but the anode
did not come off. Then, after the laminate was inserted between the
electrolytic cells, the electrolytic cells were moved to sandwich
the laminate therebetween.
[3448] It was possible to replace the electrode and the membrane
easier than in conventional ones. It was judged that renewing of
the electrode and replace of the membrane can be completed in
several tens of minutes per one cell when a laminate wound body is
provided in advance during the electrolytic operation.
Example 7-4
(Example of Use of Cathodes)
[3449] A wound body was produced in advance as follows. First, four
cathodes having a size of 0.3 m in length and 2.4 m in width were
provided in accordance with the method mentioned above. The four
cathodes were arranged without any gap so as to achieve a size of
1.2 m in length and 2.4 m in width. Adjacent cathodes were tied
together with a PTFE string and fixed such that the cathodes were
not separated. In the operation, no pressure was applied, and the
temperature was 23.degree. C. These cathodes were wound around a
polyvinyl chloride (PVC) pipe having an outer diameter having an of
76 mm and a length of 1.7 m to produce a wound body.
[3450] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 7-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound cathodes. At this time,
the cathodes were maintained substantially vertically to the
ground, but the cathodes did not come off. Then, after the cathodes
were inserted between the electrolytic cells, the electrolytic
cells were moved to sandwich the cathodes therebetween.
[3451] It was possible to replace cathodes easier than in
conventional ones. It was judged that renewing of the cathodes can
be completed in several tens of minutes per one cell when a cathode
wound body is provided in advance during the electrolytic
operation.
Example 7-5
(Example of Use of Anodes)
[3452] A wound body was produced in advance as follows. First, four
anodes having a size of 0.3 m in length and 2.4 m in width were
provided in accordance with the method mentioned above. The four
anodes were arranged without any gap so as to achieve a size of 1.2
m in length and 2.4 m in width. Adjacent anodes were tied together
with a PTFE string and fixed such that the anodes were not
separated. In the operation, no pressure was applied, and the
temperature was 23.degree. C. These anodes were wound around a
polyvinyl chloride (PVC) pipe having an outer diameter of 76 mm and
a length of 1.7 m to produce a wound body.
[3453] Next, in an existing large electrolyzer (electrolyzer
similar to that in Example 7-1), a fixed state of the adjacent
electrolytic cells and the ion exchange membrane by means of a
press device was released, and the existing membrane was removed
out to provide a gap between the electrolytic cells. Thereafter,
the wound body was conveyed onto the large electrolyzer. On the
large electrolyzer, while the PVC pipe was upright, the wound state
was released so as to pull out the wound anodes. At this time, the
anodes were maintained substantially vertically to the ground, but
the anodes did not come off. Then, after the anodes were inserted
between the electrolytic cells, the electrolytic cells were moved
to sandwich the anodes therebetween.
[3454] It was possible to replace anodes easier than in
conventional ones. It was judged that renewing of the anodes can be
completed in several tens of minutes per one cell when an anode
wound body is provided in advance during the electrolytic
operation.
Comparative Example 7-1
(Conventional Renewing of Electrode)
[3455] In an existing large electrolyzer (electrolyzer similar to
that in Example 7-1), a fixed state of the adjacent electrolytic
cells and the ion exchange membrane by means of a press device was
released, and the existing membrane was removed out to provide a
gap between the electrolytic cells. Thereafter, the electrolytic
cells were hoisted out from the large electrolyzer with a hoist.
The electrolytic cells removed were conveyed to a plant where
welding was available.
[3456] After the anode fixed by welding on the rib of the
electrolytic cell was stripped off, burrs or the like at the
portion from which the anode was stripped off with a grinder to
smooth the portion. The cathode was stripped off by removing the
portion fixed by folding the portion into the collector.
[3457] Thereafter, a new anode was placed on the rib of the anode
chamber, and the new anode was fixed to the electrolytic cell by
spot welding. Similarly in the case of the cathode, a new cathode
was placed on the cathode side and fixed by folding the cathode
into the collector.
[3458] The renewed electrolytic cell was conveyed to the position
of the large electrolyzer, and the electrolytic cell was returned
in the electrolyzer using a hoist.
[3459] The period required from the release of the fixed state of
the electrolytic cell and the ion exchange membrane to the refixing
of the electrolytic cell was one day or more.
[3460] The present application is based on Japanese Patent
Applications filed on Mar. 22, 2017 (Japanese Patent Applications
No. 2017-056524 and No. 2017-056525) and Japanese Patent
Applications filed on Mar. 20, 2018 (Japanese Patent Applications
No. 2018-053217, No. 2018-053146, No. 2018-053144, No. 2018-053231,
No. 2018-053145, No. 2018-053149, and No. 2018-053139), the
contents of which are herein incorporated by reference.
REFERENCE SIGNS LIST
<Figures for First Embodiment>
Reference Signs List for FIG. 1
[3461] 10 . . . substrate for electrode for electrolysis
[3462] 20 . . . first layer
[3463] 30 . . . second layer
[3464] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 2 to 4
[3465] 1 . . . ion exchange membrane
[3466] 2 . . . carboxylic acid layer
[3467] 3 . . . sulfonic acid layer
[3468] 4 . . . reinforcement core material
[3469] 10 . . . membrane body
[3470] 11a, 11b . . . coating layer
[3471] 21, 22 . . . reinforcement core material
[3472] 100 . . . electrolyzer
[3473] 200 . . . anode
[3474] 300 . . . cathode
[3475] 52 . . . reinforcement yarn
[3476] 504a . . . sacrifice yarn
[3477] 504 . . . continuous hole
Reference Signs List for FIGS. 5 to 9
[3478] 1 . . . electrolytic cell
[3479] 2 . . . ion exchange membrane
[3480] 4 . . . electrolyzer
[3481] 5 . . . press device
[3482] 6 . . . cathode terminal
[3483] 7 . . . anode terminal
[3484] 10 . . . anode chamber
[3485] 11 . . . anode
[3486] 12 . . . anode gasket
[3487] 13 . . . cathode gasket
[3488] 18 . . . reverse current absorber
[3489] 18a . . . substrate
[3490] 18b . . . reverse current absorbing layer
[3491] 19 . . . bottom of anode chamber
[3492] 20 . . . cathode chamber
[3493] 21 . . . cathode
[3494] 22 . . . metal elastic body
[3495] 23 . . . collector
[3496] 24 . . . support
[3497] 30 . . . partition wail
[3498] 40 . . . cathode structure for electrolysis
Reference Signs List for FIG. 10
[3499] 1 . . . pinch jig (SUS)
[3500] 2 . . . electrode
[3501] 3 . . . membrane
[3502] 4 . . . nickel plate (blasted with alumina of grain-size
number 320)
[3503] 100 . . . front face
[3504] 200 . . . side face
Reference Signs List for FIGS. 11 to 13
[3505] 1 . . . membrane
[3506] 2a . . . polyethylene pipe having an outer diameter of 280
mm
[3507] 2b . . . polyethylene pipe having an outer diameter of 145
mm
[3508] 3 . . . delaminated portion
[3509] 4 . . . close contact portion
[3510] 5 . . . electrode
Reference Signs List for FIG. 14
[3511] 1 . . . polyvinyl chloride (PVC) pipe
[3512] 2 . . . ion exchange membrane
[3513] 3 . . . electrode
[3514] 4 . . . surface plate
Reference Signs List for FIG. 15
[3515] 1 . . . surface plate
[3516] 2 . . . deformed electrode
[3517] 10 . . . jig for fixing electrode
[3518] 20 . . . direction in which a force is applied
Reference Signs List for FIGS. 16 to 21
[3519] 1 . . . 110 mm nickel line
[3520] 2 . . . 950 mm nickel line
[3521] 3 . . . frame
<Figures for Second Embodiment>
Reference Signs List for FIG. 22
[3522] 10 . . . substrate for electrode for electrolysis
[3523] 20 . . . first layer
[3524] 30 . . . second layer
[3525] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 23 to 25
[3526] 1 . . . ion exchange membrane
[3527] 2 . . . carboxylic acid layer
[3528] 3 . . . sulfonic acid layer
[3529] 4 . . . reinforcement core material
[3530] 10 . . . membrane body
[3531] 11a, 11b . . . coating layer
[3532] 21, 22 . . . reinforcement core material
[3533] 100 . . . electrolyzer
[3534] 200 . . . anode
[3535] 300 . . . cathode
[3536] 52 . . . reinforcement yarn
[3537] 504a . . . sacrifice yarn
[3538] 504 . . . continuous hole
Reference Signs List for FIGS. 26 to 30
[3539] 1 . . . electrolytic cell
[3540] 2 . . . ion exchange membrane
[3541] 4 . . . electrolyzer
[3542] 5 . . . press device
[3543] 6 . . . cathode terminal
[3544] 7 . . . anode terminal
[3545] 10 . . . anode chamber
[3546] 11 . . . anode
[3547] 12 . . . anode gasket
[3548] 13 . . . cathode gasket
[3549] 18 . . . reverse current absorber
[3550] 18a . . . substrate
[3551] 18b . . . reverse current absorbing layer
[3552] 19 . . . bottom of anode chamber
[3553] 20 . . . cathode chamber
[3554] 21 . . . cathode
[3555] 22 . . . metal elastic body
[3556] 23 . . . collector
[3557] 24 . . . support
[3558] 30 . . . partition wall
[3559] 40 . . . cathode structure for electrolysis
Reference Signs List for FIG. 31
[3560] 1 . . . pinch jig (SUS)
[3561] 2 . . . electrode
[3562] 3 . . . membrane
[3563] 4 . . . nickel plate (blasted with alumina of grain-size
number 320)
[3564] 100 . . . front face
[3565] 200 . . . side face
Reference Signs List for FIGS. 32 to 34
[3566] 1 . . . membrane
[3567] 2a . . . polyethylene pipe having an outer diameter of 280
mm
[3568] 2b . . . polyethylene pipe having an outer diameter of 145
mm
[3569] 3 . . . delaminated portion
[3570] 4 . . . close contact portion
[3571] 5 . . . electrode
Reference Signs List for FIG. 35
[3572] 1 . . . polyvinyl chloride (PVC) pipe
[3573] 2 . . . ion exchange membrane
[3574] 3 . . . electrode
[3575] 4 . . . surface plate
Reference Signs List for FIG. 36
[3576] 1 . . . surface plate
[3577] 2 . . . deformed electrode
[3578] 10 . . . jig for fixing electrode
[3579] 20 . . . direction in which a force is applied
Reference Signs List for FIGS. 37 to 42
[3580] 1 . . . 110 mm nickel line
[3581] 2 . . . 950 mm nickel line
[3582] 3 . . . frame
<Figures for Third Embodiment>
Reference Signs List for FIG. 43
[3583] 10 . . . substrate for electrode for electrolysis
[3584] 20 . . . first layer
[3585] 30 . . . second layer
[3586] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 44 to 46
[3587] 1 . . . ion exchange membrane
[3588] 2 . . . carboxylic acid layer
[3589] 3 . . . sulfonic acid layer
[3590] 4 . . . reinforcement core material
[3591] 10 . . . membrane body
[3592] 11a, 11b . . . coating layer
[3593] 21, 22 . . . reinforcement core material
[3594] 100 . . . electrolyzer
[3595] 200 . . . anode
[3596] 300 . . . cathode
[3597] 52 . . . reinforcement yarn
[3598] 504a . . . sacrifice yarn
[3599] 504 . . . continuous hole 504
Reference Signs List for FIGS. 47 to 51
[3600] 1 . . . laminate
[3601] 2 . . . electrode for electrolysis
[3602] 2a . . . inner surface of electrode for electrolysis
[3603] 2b . . . outer surface of electrode for electrolysis
[3604] 3 . . . membrane
[3605] 3a . . . inner surface of membrane
[3606] 3b . . . outer surface of membrane
[3607] 7 . . . fixing member
Reference Signs List for FIGS. 52 to 56
[3608] 1 . . . electrolytic cell
[3609] 2 . . . ion exchange membrane
[3610] 4 . . . electrolyzer
[3611] 5 . . . press device
[3612] 6 . . . cathode terminal
[3613] 7 . . . anode terminal
[3614] 10 . . . anode chamber
[3615] 11 . . . anode
[3616] 12 . . . anode gasket
[3617] 13 . . . cathode gasket
[3618] 18 . . . reverse current absorber
[3619] 18a . . . substrate
[3620] 18b . . . reverse current absorbing layer
[3621] 19 . . . bottom of anode chamber
[3622] 20 . . . cathode chamber
[3623] 21 . . . cathode
[3624] 22 . . . metal elastic body
[3625] 23 . . . collector
[3626] 24 . . . support
[3627] 30 . . . partition wail
[3628] 40 . . . cathode structure for electrolysis
<Figures for Fourth Embodiment>
Reference Signs List for FIGS. 63 to 67
[3629] 1 . . . electrolytic cell
[3630] 2 . . . ion exchange membrane
[3631] 4 . . . electrolyzer
[3632] 5 . . . press device
[3633] 6 . . . cathode terminal
[3634] 7 . . . anode terminal
[3635] 10 . . . anode chamber
[3636] 11 . . . anode
[3637] 12 . . . anode gasket
[3638] 13 . . . cathode gasket
[3639] 18 . . . reverse current absorber
[3640] 18a . . . substrate
[3641] 18b . . . reverse current absorbing layer
[3642] 19 . . . bottom of anode chamber
[3643] 20 . . . cathode chamber
[3644] 21 . . . cathode
[3645] 22 . . . metal elastic body
[3646] 23 . . . collector
[3647] 24 . . . support
[3648] 30 . . . partition wall
[3649] 40 . . . cathode structure for electrolysis
Reference Signs List for FIG. 68
[3650] 10 . . . substrate for electrode for electrolysis
[3651] 20 . . . first layer
[3652] 30 . . . second layer
[3653] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 69 to 71
[3654] 1 . . . ion exchange membrane
[3655] 2 . . . carboxylic acid layer
[3656] 3 . . . sulfonic acid layer
[3657] 4 . . . reinforcement core material
[3658] 10 . . . membrane body
[3659] 11a, 11b . . . coating layer
[3660] 21, 22 . . . reinforcement core material
[3661] 100 . . . electrolyzer
[3662] 200 . . . anode
[3663] 300 . . . cathode
[3664] 52 . . . reinforcement yarn
[3665] 504a . . . sacrifice yarn
[3666] 504 . . . continuous hole
Reference Signs List for FIGS. 72 to 78
[3667] 1 . . . laminate
[3668] 2 . . . electrode for electrolysis
[3669] 2a . . . inner surface of electrode for electrolysis
[3670] 2b . . . outer surface of electrode for electrolysis
[3671] 3 . . . membrane
[3672] 3a . . . inner surface of membrane
[3673] 3b . . . outer surface of membrane
[3674] 7 . . . fixing member
[3675] A . . . gasket
[3676] B . . . membrane
[3677] C . . . electrode for electrolysis
[3678] A1 . . . outermost perimeter of gasket
[3679] B1 . . . outermost perimeter of membrane
[3680] C1 . . . outermost perimeter of electrode for
electrolysis
Reference Signs List for FIG. 79
[3681] 1 . . . pinch jig (SUS)
[3682] 2 . . . electrode
[3683] 3 . . . membrane
[3684] 4 . . . nickel plate (blasted with alumina of grain-size
number 320)
[3685] 100 . . . front face
[3686] 200 . . . side face
Reference Signs List for FIGS. 80 to 82
[3687] 1 . . . membrane
[3688] 2a . . . polyethylene pipe having an outer diameter of 280
mm
[3689] 2b . . . polyethylene pipe having an outer diameter of 145
mm
[3690] 3 . . . delaminated portion
[3691] 4 . . . close contact portion
[3692] 5 . . . electrode
Reference Signs List for FIG. 84
[3693] 1 . . . surface plate
[3694] 2 . . . deformed electrode
[3695] 10 . . . jig for fixing electrode
[3696] 20 . . . direction in which a force is applied
Reference Signs List for FIGS. 85 to 90
[3697] 1 . . . 110 mm nickel line
[3698] 2 . . . 950 mm nickel line
[3699] 3 . . . frame
<Figures for Fifth Embodiment>
Reference Signs List for FIGS. 91 to 95
[3700] 1 . . . electrolytic cell
[3701] 2 . . . ion exchange membrane
[3702] 4 . . . electrolyzer
[3703] 5 . . . press device
[3704] 6 . . . cathode terminal
[3705] 7 . . . anode terminal
[3706] 10 . . . anode chamber
[3707] 11 . . . anode
[3708] 12 . . . anode gasket
[3709] 13 . . . cathode gasket
[3710] 18 . . . reverse current absorber
[3711] 18a . . . substrate
[3712] 18b . . . reverse current absorbing layer
[3713] 19 . . . bottom of anode chamber
[3714] 20 . . . cathode chamber
[3715] 21 . . . cathode
[3716] 22 . . . metal elastic body
[3717] 23 . . . collector
[3718] 24 . . . support
[3719] 30 . . . partition wall
[3720] 40 . . . cathode structure for electrolysis
Reference Signs List for FIG. 96
[3721] 10 . . . substrate for electrode for electrolysis
[3722] 20 . . . first layer
[3723] 30 . . . second layer
[3724] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 97 to 99
[3725] 1 . . . ion exchange membrane
[3726] 2 . . . carboxylic acid layer
[3727] 3 . . . sulfonic acid layer
[3728] 4 . . . reinforcement core material
[3729] 10 . . . membrane body
[3730] 11a, 11b . . . coating layer
[3731] 21, 22 . . . reinforcement core material
[3732] 100 . . . electrolyzer
[3733] 200 . . . anode
[3734] 300 . . . cathode
[3735] 52 . . . reinforcement yarn
[3736] 504a . . . sacrifice yarn
[3737] 504 . . . continuous hole
<Figures for Sixth Embodiment>
Reference Signs List for FIGS. 103 to 107
[3738] 1 . . . electrolytic cell
[3739] 2 . . . ion exchange membrane
[3740] 4 . . . electrolyzer
[3741] 5 . . . press device
[3742] 6 . . . cathode terminal
[3743] 7 . . . anode terminal
[3744] 10 . . . anode chamber
[3745] 11 . . . anode
[3746] 12 . . . anode gasket
[3747] 13 . . . cathode gasket
[3748] 18 . . . reverse current absorber
[3749] 18a . . . substrate
[3750] 18b . . . reverse current absorbing layer
[3751] 19 . . . bottom of anode chamber
[3752] 20 . . . cathode chamber
[3753] 21 . . . cathode
[3754] 22 . . . metal elastic body
[3755] 23 . . . collector
[3756] 24 . . . support
[3757] 30 . . . partition wall
[3758] 40 . . . cathode structure for electrolysis
Reference Signs List for FIG. 108
[3759] 10 . . . substrate for electrode for electrolysis
[3760] 20 . . . first layer
[3761] 30 . . . second layer
[3762] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 109 to 111
[3763] 1 . . . ion exchange membrane
[3764] 2 . . . carboxylic acid layer
[3765] 3 . . . sulfonic acid layer
[3766] 4 . . . reinforcement core material
[3767] 10 . . . membrane body
[3768] 11a, 11b . . . coating layer
[3769] 21, 22 . . . reinforcement core material
[3770] 100 . . . electrolyzer
[3771] 200 . . . anode
[3772] 300 . . . cathode
[3773] 52 . . . reinforcement yarn
[3774] 504a . . . sacrifice yarn
[3775] 504 . . . continuous hole
<Figures for Seventh Embodiment>
Reference Signs List for FIGS. 112 to 118
[3776] 1 . . . electrolytic cell
[3777] 2 . . . ion exchange membrane
[3778] 2a . . . new ion exchange membrane
[3779] 4 . . . electrolyzer
[3780] 5 . . . press device
[3781] 6 . . . cathode terminal
[3782] 7 . . . anode terminal
[3783] 8 . . . electrolyzer frame
[3784] 9 . . . laminate
[3785] 10 . . . anode chamber
[3786] 11 . . . anode
[3787] 12 . . . anode gasket
[3788] 13 . . . cathode gasket
[3789] 18 . . . reverse current absorber
[3790] 18a . . . substrate
[3791] 18b . . . reverse current absorbing layer
[3792] 19 . . . bottom of anode chamber
[3793] 20 . . . cathode chamber
[3794] 21 . . . cathode
[3795] 22 . . . metal elastic body
[3796] 23 . . . collector
[3797] 24 . . . support
[3798] 30 . . . partition wail
[3799] 40 . . . cathode structure for electrolysis
[3800] 100 . . . electrode for electrolysis
Reference Signs List for FIG. 119
[3801] 10 . . . substrate for electrode for electrolysis
[3802] 20 . . . first layer
[3803] 30 . . . second layer
[3804] 100 . . . electrode for electrolysis
Reference Signs List for FIGS. 120 to 122
[3805] 1 . . . ion exchange membrane
[3806] 2 . . . carboxylic acid layer
[3807] 3 . . . sulfonic acid layer
[3808] 4 . . . reinforcement core material
[3809] 10 . . . membrane body
[3810] 11a, 11b . . . coating layer
[3811] 21, 22 . . . reinforcement core material
[3812] 100 . . . electrolyzer
[3813] 200 . . . anode
[3814] 300 . . . cathode
[3815] 52 . . . reinforcement yarn
[3816] 504a . . . sacrifice yarn
[3817] 504 . . . continuous hole
* * * * *