U.S. patent application number 16/090654 was filed with the patent office on 2019-04-18 for aqueous sealant composition for nonaqueous electrolyte battery.
This patent application is currently assigned to ZEON CORPORATION. The applicant listed for this patent is ZEON CORPORATION. Invention is credited to Kouichirou MAEDA.
Application Number | 20190115569 16/090654 |
Document ID | / |
Family ID | 60041841 |
Filed Date | 2019-04-18 |
United States Patent
Application |
20190115569 |
Kind Code |
A1 |
MAEDA; Kouichirou |
April 18, 2019 |
AQUEOUS SEALANT COMPOSITION FOR NONAQUEOUS ELECTROLYTE BATTERY
Abstract
Disclosed is an aqueous sealant composition for a nonaqueous
electrolyte battery by which a sealant layer having excellent
properties can be obtained. An aqueous sealant composition for a
nonaqueous electrolyte battery of the present disclosure comprises
an aqueous dispersion in an amount of 70 mass % or more and 97 mass
% or less by mass of solid content, wherein the aqueous dispersion
comprises an olefinic polymer as a main component.
Inventors: |
MAEDA; Kouichirou;
(Chiyoda-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZEON CORPORATION |
Chiyoda-ku Tokyo |
|
JP |
|
|
Assignee: |
ZEON CORPORATION
Chiyoda-ku Tokyo
JP
|
Family ID: |
60041841 |
Appl. No.: |
16/090654 |
Filed: |
April 14, 2017 |
PCT Filed: |
April 14, 2017 |
PCT NO: |
PCT/JP2017/015379 |
371 Date: |
October 2, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/0525 20130101;
H01M 2/08 20130101; C09D 5/022 20130101; C09D 123/06 20130101; C08L
29/04 20130101; C08L 2201/54 20130101; C09J 123/0876 20130101; C09J
123/0876 20130101; C09D 123/12 20130101 |
International
Class: |
H01M 2/08 20060101
H01M002/08; H01M 10/0525 20060101 H01M010/0525; C09D 123/06
20060101 C09D123/06; C09D 123/12 20060101 C09D123/12; C09D 5/02
20060101 C09D005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2016 |
JP |
2016-081721 |
Claims
1. An aqueous sealant composition for a nonaqueous electrolyte
battery, comprising an aqueous dispersion in an amount of 70 mass %
or more and 97 mass % or less by mass of solid content, wherein the
aqueous dispersion comprises an olefinic polymer as a main
component.
2. The aqueous sealant composition for a nonaqueous electrolyte
battery according to claim 1, further comprising: a water-soluble
polymer in an amount of 3 mass % or more and 30 mass % or less by
mass of solid content; and a total solid content concentration of 5
mass % or more and 70 mass % or less.
3. The aqueous sealant composition for a nonaqueous electrolyte
battery according to claim 2, wherein the water-soluble polymer has
a 4 mass % aqueous solution viscosity of 4 mPa.times.s or more and
500 mPa.times.s or less.
4. The aqueous sealant composition for a nonaqueous electrolyte
battery according to claim 1, wherein the aqueous dispersion is a
dispersion of polyethylene or polypropylene in water, or a
self-emulsified modified olefinic polymer.
5. The aqueous sealant composition for a nonaqueous electrolyte
battery according to claim 2, wherein the aqueous dispersion is a
dispersion of polyethylene or polypropylene in water, or a
self-emulsified modified olefinic polymer.
6. The aqueous sealant composition for a nonaqueous electrolyte
battery according to claim 3, wherein the aqueous dispersion is a
dispersion of polyethylene or polypropylene in water, or a
self-emulsified modified olefinic polymer.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an aqueous sealant
composition used for a nonaqueous electrolyte battery.
BACKGROUND
[0002] Lithium ion secondary batteries are widely used as power
sources for small electronic devices such as notebook computers,
mobile phones, PDAs, and the like. Further, in recent years,
lithium ion secondary batteries are also used for automotive
applications. As the usage range of lithium ion secondary batteries
expands, demands for the performance and safety of lithium ion
secondary batteries (hereinafter sometimes simply referred to as
"batteries") are increasing. These batteries are usually repeatedly
used by virtue of charge and discharge operations. However, due to
repeated charge and discharge, sometimes volume fluctuation and
heat generation occur in the electrodes, and the pressure inside
the battery rises, such that the electrolytic solution leaks to the
outside. In this case, not only the battery characteristics
deteriorate but also problems such as heat generation due to the
reduction of the electrolytic solution and corrosion of the device
due to the leaked electrolytic solution occur. For example, when an
electrolytic solution is used for a lithium ion secondary battery,
since the electrolytic solution is organic and is extremely apt to
be damaged by moisture, such a lithium ion secondary battery is
required to have a high sealability to completely prevent moisture
from entering the inside of the battery and completely prevent
leakage of the electrolytic solution.
[0003] For example, a lithium ion secondary battery is housed in a
metal container to seal its power generating element, and in order
to prevent a short circuit between the positive electrode and the
negative electrode, it is necessary to insulate the positive
electrode terminal from the negative electrode terminal. Generally,
a gasket made of an insulating material is used in the opening of
the metal container containing the power generating element for
insulation and sealing between the positive electrode and the
negative electrode. As the insulating material, it is well known to
use a resin insulating gasket (for example, refer to PTL 1).
[0004] In order to further strengthen sealing with such an
insulating gasket, it is also proposed to use an insulating gasket
and a sealant in combination (for example, refer to PTL 2 to 4). In
this technique, the sealability between the insulating gasket and
the metal container is enhanced by applying a sealant to the
insulating gasket or the metal container and then attaching the
insulating gasket to the metal container.
[0005] Examples of such a sealant include pitch-based materials
such as coal tar, asphalt and the like, and materials obtained by
adding a polymer as a modifier to a pitch-based material (for
example, refer to PTL 5). In addition to pitch-based materials, a
butyl rubber (for example, refer to PTL 6), a diene rubber having a
predetermined weight-average molecular weight (for example, refer
to PTL 7), and a block polymer containing a diene monomer (for
example, refer to PTL 8) are also proposed.
[0006] Incidentally, in recent years, the influence of volatile
organic compounds (VOC) on the environment has become a problem.
The aforementioned sealants are used as a sealant composition
dissolved or dispersed in an organic solvent, which is a VOC.
Therefore, a sealant composition not using VOC is required.
[0007] PTL 9 proposes an aqueous sealant composition, however, the
performance thereof required for a sealant is insufficient. For
example, the strength of the sealant layer formed by the aqueous
sealant composition is insufficient compared with a sealant layer
obtained by a sealant composition using an organic solvent. In
addition, PTL 10 proposes an aqueous sealant composition not using
VOC, however, it is intended for a battery using an aqueous
electrolyte solution, and no consideration has been given to a
nonaqueous electrolyte battery.
CITATION LIST
Patent Literature
[0008] PTL 1: JPS 53-84122 A
[0009] PTL 2: JPS 55-30148 A
[0010] PTL 3: JPS 55-16352 A
[0011] PTL 4: JPS 59-112565 A
[0012] PTL 5: JPH 06-96750 A
[0013] PTL 6: WO 2014/054406 A1
[0014] PTL 7: JP 3574276 B2
[0015] PTL 8: JP 3956523 B2
[0016] PTL 9: JPS 63-1706 B2
[0017] PTL 10: JP 2006-107935 A
SUMMARY
Technical Problem
[0018] An objective of the present disclosure is to provide an
aqueous sealant composition for a nonaqueous electrolyte battery by
which a sealant layer having excellent properties can be
obtained.
Solution to Problem
[0019] The inventor conducted a diligent investigation, and through
this investigation, the inventor discovered that the objective set
forth above can be achieved through use of an aqueous dispersion at
a predetermined ratio, wherein the aqueous dispersion comprises an
olefinic polymer as a main component, and thereby completed the
present disclosure.
[0020] Specifically, the present disclosure provides the
following.
[0021] (1) An aqueous sealant composition for a nonaqueous
electrolyte battery, comprising an aqueous dispersion in an amount
of 70 mass % or more and 97 mass % or less by mass of solid
content, wherein the aqueous dispersion comprises an olefinic
polymer as a main component.
[0022] (2) The aqueous sealant composition for a nonaqueous
electrolyte battery according to (1), further comprising: a
water-soluble polymer in an amount of 3 mass % or more and 30 mass
% or less by mass of solid content; and a total solid content
concentration of 5 mass % or more and 70 mass % or less.
[0023] (3) The aqueous sealant composition for a nonaqueous
electrolyte battery according to (2), wherein the water-soluble
polymer has a 4 mass % aqueous solution viscosity of 4 mPa.times.s
or more and 500 mPa.times.s or less.
[0024] (4) The aqueous sealant composition for a nonaqueous
electrolyte battery according to any one of (1) to (3), wherein the
aqueous dispersion is a dispersion of polyethylene or polypropylene
in water, or a self-emulsified modified olefinic polymer.
Advantageous Effect
[0025] According to the presently disclosed aqueous sealant
composition for a nonaqueous electrolyte battery, a sealant layer
having excellent properties can be obtained.
DETAILED DESCRIPTION
[0026] The following describes an aqueous sealant composition for a
nonaqueous electrolyte battery according to the present disclosure.
The presently disclosed aqueous sealant composition for a
nonaqueous electrolyte battery (hereinafter referred to also as
"aqueous sealant composition") comprises an aqueous dispersion in
an amount of 70 mass % or more and 97 mass % or less by mass of
solid content, wherein the aqueous dispersion comprises an olefinic
polymer as a main component.
[0027] (Aqueous Dispersion Comprising Olefinic Polymer as Main
Component)
[0028] The olefinic polymer comprised as a main component in the
aqueous dispersion is not particularly limited as long as it is a
polymer comprising an olefinic monomer unit obtained by
polymerizing an olefinic monomer such as ethylene, propylene or the
like. Here, the olefinic polymer is preferably comprised in the
aqueous dispersion in an amount of 20 mass % or more and 100 mass %
or less, and more preferably in an amount of 30 mass % or more and
100 mass % or less by mass of solid content (in terms of solid
content).
[0029] Further, the solid content concentration of the aqueous
dispersion comprising the olefinic polymer as a main component is
preferably 20 mass % or more, more preferably 30 mass % or more,
and preferably 70 mass % or less, more preferably 65 mass % or
less.
[0030] The olefinic polymer may be a homopolymer of an olefinic
monomer, a copolymer of an olefinic monomer, or a copolymer of an
olefinic monomer and a monomer other than an olefinic monomer.
[0031] Here, the monomer other than an olefinic monomer is not
particularly limited as long as it is copolymerizable with an
olefinic monomer, and examples thereof include cyano
group-containing vinyl monomers, amino group-containing vinyl
monomers, pyridyl group-containing vinyl monomers, alkoxyl
group-containing vinyl monomers, aromatic vinyl monomers, and the
like. Of these examples, cyano group-containing vinyl monomers and
aromatic vinyl monomers are preferable, and aromatic vinyl monomers
are more preferable. These monomers copolymerizable with an
olefinic monomer can be used alone or in combination of two or more
thereof.
[0032] Examples of aromatic vinyl monomers include styrene,
.alpha.-methyl styrene, 2-methyl styrene, 3-methyl styrene,
4-methyl styrene, 2,4-diisopropyl styrene, 2,4-dimethyl styrene,
4-t-butyl styrene, 5-t-butyl-2-methyl styrene,
N,N-dimethylaminoethyl styrene, N,N-diethylaminoethylstyrene, and
the like.
[0033] These aromatic vinyl monomers can be used alone or in
combination of two or more thereof.
[0034] Examples of the olefinic polymer include polyethylene,
polypropylene (PP), polybutene, polybutadiene, butadiene-isoprene
copolymers, polyisoprene, ethylene-vinyl acetate copolymers (EVA),
ethylene-ethyl acrylate copolymers, ethylene-propylene polymers
(EPR), ethylene-propylene-diene terpolymers (EPDM),
styrene-butadiene block copolymer hydrides (SEB, SEBS) and the
like, which can be used alone or in combination of two or more
thereof.
[0035] Of these examples, polyethylene or polypropylene is
preferable as the olefinic polymer. As the aqueous dispersion, it
is preferable to use polyethylene or polypropylene dispersed in
water.
[0036] The olefinic polymer is produced, for example, by
polymerizing a monomer composition containing an aforementioned
monomer in an aqueous solvent.
[0037] The aqueous solvent is not particularly limited as long as
the olefinic polymer can be dispersed, and is selected from aqueous
solvents having a boiling point at normal pressure of preferably
80.degree. C. or more and 350.degree. C. or less, more preferably
100.degree. C. or more and 300.degree. C. or less.
[0038] More particularly, water is preferable as the aqueous
solvent from the viewpoint that it is incombustible and a
dispersion of an olefinic polymer can be easily obtained. Further,
it is also considerable to use water as a main solvent and mix an
aqueous solvent other than water therewith, as long as the effect
of the present disclosure is not impaired and the dispersion state
of the olefinic polymer is secured.
[0039] The polymerization method of the olefinic polymer is not
particularly limited, and for example, any of solution
polymerization, suspension polymerization, bulk polymerization, and
emulsion polymerization may be used. Alternatively, the
polymerization method may be any of the methods including ionic
polymerization, radical polymerization, and living radical
polymerization. The emulsion polymerization method is particularly
preferable from the viewpoint of production efficiency. According
to the emulsion polymerization method, for example, it is easy to
obtain a high molecular weight substance, and since the olefinic
polymer can be obtained in a latex state in which it is dispersed
in water as it is, a redispersion process becomes unnecessary, and
the latex can be used as it is as an aqueous dispersion comprising
an olefinic polymer as a main component for preparing a presently
disclosed aqueous sealant composition. The emulsion polymerization
can be carried out by a standard method. In the emulsion
polymerization, commonly used polymerization auxiliary materials
such as an emulsifier, a polymerization initiator, a molecular
weight modifier, a chain transfer agent and the like can be
used.
[0040] Further, in the present disclosure, as the olefinic polymer,
it is preferable to use a modified olefinic polymer which is a
partial copolymer of an olefinic polymer and a polymerizable
unsaturated organic acid. Examples of polymerizable unsaturated
organic acids include maleic anhydride, acrylic acid, methacrylic
acid, and esters thereof. These polymerizable unsaturated organic
acids can be used alone or as a combination of two or more
thereof.
[0041] A modified olefinic polymer can be obtained by polymerizing
a polymerizable unsaturated organic acid and a polyolefin using a
polymerization method such as random copolymerization, block
copolymerization, graft copolymerization, or the like.
[0042] As the modified olefinic polymer, commercially available
olefinic polymers may be used. Specific examples of commercially
available products include Zaikthene-A-GH, Zaikthene-AC,
Zaikthene-NC, Zaikthene-N, Zaikthene-L (that are manufactured by
Sumitomo Seika Chemicals Company, Limited), Arrow base SA-1200,
Arrow base SB-1200, Arrow base SE-1200, Arrow base SB-1010 (that
are manufactured by Unitika Ltd.), High-tech S-3121, High-tech
S-3123, High-tech S-3127 (that are manufactured by TOHO Chemical
Industry Co., Ltd.), and the like.
[0043] It is preferable to use a self-emulsified modified olefinic
polymer.
[0044] (Aqueous Sealant Composition)
[0045] The presently disclosed aqueous sealant composition
comprises an aqueous dispersion comprising the olefinic polymer as
a main component, in an amount of 70 mass % or more, preferably 80
mass % or more, further preferably 85 mass % or more, and 97 mass %
or less, preferably 95 mass % or less, further preferably 93 mass %
or less by mass of solid content (in terms of solid content). When
the content percentage of the aqueous dispersion in the aqueous
sealant composition is excessively high, it is difficult to obtain
a uniform film (sealant layer). On the other hand, when the content
percentage of the aqueous dispersion in the aqueous sealant
composition is excessively low, the flexibility of the sealant
layer obtained using the aqueous sealant composition decreases.
That is, the sealing performance deteriorates.
[0046] Further, the viscosity of the aqueous sealant composition is
preferably 10 mPa.times.s or more, more preferably 100 mPa.times.s
or more, and preferably 10,000 mPa.times.s or less, more preferably
1,000 mPa.times.s or less. When the viscosity of the aqueous
sealant composition is within such a range, it is possible to
suppress a phenomenon that the viscosity is excessively high,
making it difficult to coat. It is also possible to suppress a
phenomenon that the viscosity is excessively low, making it
difficult to form a uniform film. Note that the viscosity is a
viscosity value measured at a liquid temperature of 20.degree. C.,
using a Brookfield viscometer (B type viscometer).
[0047] It is preferable that the presently disclosed aqueous
sealant composition comprises a water-soluble polymer other than
the aqueous dispersion comprising the olefinic polymer as a main
component. Examples of water-soluble polymers include polyvinyl
alcohol, polyacrylic acid, polystyrene sulfonic acid, and the like.
Of these examples, polyvinyl alcohol is preferable, and polyvinyl
alcohol having a saponification rate of 98 mol % or more, which is
said to be fully saponified type, is particularly preferable.
[0048] The aforementioned water-soluble polymers may be used alone
or in combination of two or more thereof in any proportion.
[0049] The water-soluble polymer preferably has a 4 mass % aqueous
solution viscosity of 4 mPa.times.s or more and 500 mPa.times.s or
less. Note that the viscosity is a viscosity value measured at a
liquid temperature of 20.degree. C., using a Brookfield viscometer
(B type viscometer).
[0050] Further, the content percentage of the water-soluble polymer
in the aqueous sealant composition is preferably 3 mass % or more,
more preferably 5 mass % or more, further preferably 7 mass % or
more, and preferably 30 mass % or less, more preferably 20 mass %
or less, further preferably 15 mass % or less, by mass of solid
content (in terms of solid content). When the content percentage of
the water-soluble polymer is within such a range, it is possible to
suppress a phenomenon that the content percentage of the
water-soluble polymer is excessively high, such that the
flexibility of the obtained sealant layer decreases, that is, the
sealing performance deteriorates, and it is also possible to
suppress a phenomenon that the content percentage of the
water-soluble polymer is excessively low, making it difficult to
obtain a uniform film (sealant layer).
[0051] Furthermore, the solid content concentration of the
presently disclosed aqueous sealant composition is preferably 5
mass % or more, more preferably 20 mass % or more, further
preferably 30 mass % or more, particularly 35 mass % or more, and
preferably 70 mass % or less, more preferably 60 mass % or less,
further preferably 50 mass % or less, particularly 43 mass % or
less. When the total solid content concentration is within such a
range, it is possible to suppress a phenomenon that the total solid
content concentration is excessively high, making it difficult to
obtain a sealant layer having a desired film thickness. It is also
possible to suppress a phenomenon that the total solid content
concentration is excessively low, such that a longer drying time is
required at the time of formation of a sealant layer. The total
solid content concentration of the aqueous sealant composition can
be adjusted by a known method such as concentration using a rotary
evaporator.
[0052] Moreover, if necessary, additives such as colorants and the
like may be added to the presently disclosed aqueous sealant
composition. A colorant that can be added is preferably one that
does not react with an electrolyte solution and does not dissolve
in an electrolyte solution, and examples thereof include various
organic and inorganic pigments. Of these examples, carbon black,
particularly carbon black having a particle diameter of 0.1 .mu.m
or less such as furnace black, channel black and the like is
preferable. When adding such a colorant, it is necessary to
dissolve or disperse it sufficiently uniformly in the composition,
and when using a granulated colorant or a colorant having an
aggregated structure, it is better to disperse it with a ball mill,
a sand mill, ultrasonic waves, or the like. The amount of such
additives such as colorants to be added may be an arbitrary amount
as necessary, and is usually 0.01 mass % or more and 20 mass % or
less, preferably 0.01 mass % or more and 5 mass % or less, and more
preferably 0.02 mass % or more and 3 mass % or less, with respect
to the amount of the olefinic polymer (100 mass %). When the amount
of additives is within such a range, it is possible to suppress a
phenomenon that the addition amount of additives is excessively
large, such that the flexibility of the sealant layer decreases,
resulting in cracking.
[0053] The producing method for the presently disclosed aqueous
sealant composition is not particularly limited, and for example, a
method of adding other components such as a water-soluble polymer
and additives to an aqueous dispersion comprising an olefinic
polymer as a main component; a method of mixing an aqueous
dispersion comprising an olefinic polymer as a main component and
an aqueous solution of a water-soluble polymer that were
respectively prepared, and then adding other components such as
additives thereto; and the like.
[0054] (Nonaqueous Electrolyte Battery)
[0055] A nonaqueous electrolyte battery using the presently
disclosed aqueous sealant composition is such that, a sealant layer
formed from the aforementioned aqueous sealant composition is
provided between an insulating gasket attached to the opening of a
metal container housing the power generating element and the metal
container, and/or between the insulating gasket and a sealing body.
The material of the metal container, the power generating element,
and the insulating gasket used for the nonaqueous electrolyte
battery may be ones commonly used. That is, the nonaqueous
electrolyte battery has its power generating element housed in a
metal container and sealed.
[0056] The power generating element may be an electrolyte, active
materials for positive electrode and negative electrode, a
separator, or the like. As the electrolyte, an electrolyte solution
comprising a supporting electrolyte and an organic electrolytic
solution solvent is used.
[0057] In the nonaqueous electrolyte battery, as the supporting
electrolyte which constitutes the electrolytic solution, for
example, a compound which is easily hydrolyzed through reaction
with water, such as lithium compounds such as LiPF.sub.6,
LiBF.sub.4, LiClO.sub.4 and the like, is used. As the nonaqueous
electrolyte solvent, for example, a combustible organic compound
such as propylene carbonate (PC), ethylene carbonate (EC), diethyl
carbonate (DEC) or the like is used. As the insulating gasket, it
is preferable to use a material made of a polyolefin resin such as
polyethylene, polypropylene, ethylene copolymerized polypropylene
or the like, which is generally said to have a high electrolytic
solution resistance. Further, as the polyolefin resin, it is better
to use one having a heat distortion temperature measured by JIS
K7207 of preferably 90.degree. C. or more and 200.degree. C. or
less, more preferably 90.degree. C. or more and 150.degree. C. or
less, and further preferably 95.degree. C. or more and 130.degree.
C. or less. When the heat distortion temperature of the polyolefin
resin is within such a range, it is possible to suppress a
phenomenon that the heat distortion temperature is excessively
high, such that the bending elastic modulus at normal temperature
is too high, causing deformation when attaching the insulating
gasket, and thus resulting in cracking. It is also possible to
suppress a phenomenon that the heat distortion temperature is
excessively low, such that the resistance of the insulating gasket
at high temperature is poor and the sealability deteriorates.
[0058] A sealant layer of the nonaqueous electrolyte battery can be
formed, for example, by the following procedure. Initially, a
predetermined amount of the aqueous sealant composition is fed to
and applied to the surface of the metal container and/or the
surface of the insulating gasket with a metering pump such as an
air-driven metering dispenser, a roller pump, a gear pump or the
like. After coating, natural drying is carried out while
maintaining the horizontally so as to prevent the aqueous sealant
composition from biasing, and thereafter the aqueous solvent is
removed to form a thin layer.
[0059] The coating method is not limited to the method using a
metering pump, and may be manually performed using a brush if the
amount of work is small. In addition, for drying, forced drying
using a heating device may be performed instead of natural drying,
and in this case, drying in a short time becomes possible, enabling
an industrially more suitable process.
[0060] The thickness of the sealant layer formed by the above
method may be freely selected according to the sizes of the metal
container and the insulating gasket, and is usually 0.1 .mu.m or
more and 1000 .mu.m or less. When the thickness of the sealant
layer is within such a range, it is possible to suppress a
phenomenon that the layer thickness is excessively insufficient,
such that problems such as electrolyte solution leakage and
moisture intrusion may occur and the layer may be cut. It is also
possible to suppress a phenomenon that the thickness of the sealant
layer is excessively thick, making it difficult to form a
layer.
[0061] Note that as the nonaqueous electrolyte battery in which the
presently disclosed aqueous sealant composition is used, a lithium
ion secondary battery is preferable.
[0062] The following describes the present disclosure through
examples. However, the present disclosure is not limited to these
examples. Note that "parts" and "%" in the present examples are by
mass unless otherwise specified. In the examples and comparative
examples, evaluation of wettability, evaluation of film strength,
measurement of viscosity, evaluation of flexibility and evaluation
of sealability were carried out as follows.
[0063] (Wettability (Coating Film Appearance))
[0064] The appearance of the surface of the sealant layer of each
test piece obtained in the examples and comparative examples was
visually observed. A case in which no defect such as a crack, a
pinhole or the like was observed on the surface of the sealant
layer was given an evaluation of "good", and a case in which a
defect such as a crack, a pinhole or the like, or unevenness was
observed on the surface of the sealant layer was given an
evaluation of "poor". The results are listed in Table 1.
[0065] (Film Strength (Peel Strength))
[0066] The peel strength of each test piece having a sealant layer
formed on an aluminum foil obtained in the examples and comparative
examples was measured by a 180.degree. peeling method in accordance
with JIS Z0237. More particularly, an aluminum tape with an
adhesive was laminated to each test piece cut into a ribbon-like
shape having a width of 20 mm, and the peel strength was measured
at a tensile rate of 200 mm/min at 23.degree. C. using a tensile
tester. The results are listed in Table 1. Note that the greater
the peel strength, the better the film strength (strength of the
sealant layer).
[0067] (Viscosity)
[0068] In the examples and comparative examples, the viscosity of
each aqueous sealant composition was measured at a liquid
temperature of 20.degree. C. using a B type viscometer (Brookfield
viscometer, type BL, manufactured by TOKYO KEIKI INC.). The results
are listed in Table 1.
[0069] (Flexibility (Bending Tolerance))
[0070] Each test piece having a sealant layer formed on an aluminum
foil obtained in the examples and comparative examples was immersed
in methanol at -30.degree. C. for 1 hour and was folded with the
sealant layer on the outside immediately after being taken out. The
bent portion was observed as to whether cracking, peeling or the
like is present. A case in which no cracking, peeling and the like
was observed was given an evaluation of "good", and a case in which
cracking, peeling or the like was observed was given an evaluation
of "poor". The results are listed in Table 1.
[0071] (Sealability)
[0072] A film having a size of 1 cm.times.1 cm was produced from
each aqueous sealant composition obtained in the examples and
comparative examples, and the mass M.sub.0 was measured. Then, each
film was immersed in a simulated electrolytic solution (a mixed
solution of ethylene carbonate (EC) and diethyl carbonate (DEC)
(EC/DEC=1/2: volume ratio) in which 1.0 mol/L of LiPF.sub.6 was
dissolved) at 60.degree. C. for 72 hours, and the mass M.sub.1 was
measured. The degree of swelling was calculated in accordance with
(M.sub.1-M.sub.0)/M.sub.0.times.100(%). Note that the smaller the
degree of swelling, the better the sealability. The results are
listed in Table 1.
EXAMPLES
Example 1
[0073] (Aqueous Sealant Composition)
[0074] To 95 parts by mass of solid content of Zaikthene NC as a
aqueous dispersion comprising an olefinic polymer as a main
component (manufactured by Sumitomo Seika Chemicals Company,
Limited, content of olefinic polymer (in terms of solid content):
100 mass %), 5 parts by mass of solid content of a 10 mass %
aqueous solution of polyvinyl alcohol (polyvinyl alcohol JF17
manufactured by JAPAN VAM & POVAL CO., LTD., viscosity of a 4
mass % aqueous solution: 4.5 mPa.times.s, saponification rate: 98
mol %) was added as a water-soluble polymer to obtain an aqueous
sealant composition. The total solid content concentration of the
obtained aqueous sealant composition was 45 mass %.
[0075] (Test Piece)
[0076] The obtained aqueous sealant composition was cast on an
aluminum foil (thickness: 20 .mu.m) with a doctor blade having a
gap of 200 .mu.m and was then subjected to heat drying at
80.degree. C. for 20 minutes to form a film-like sealant layer to
obtain a test piece.
Example 2
[0077] An aqueous sealant composition was produced in the same
manner as in Example 1 except that the amount of Zaikthene NC was
changed to 90 parts by mass of solid content and the amount of
polyvinyl alcohol was changed to 10 parts by mass of solid content.
The total solid content concentration of the obtained aqueous
sealant composition was 42 mass %.
[0078] A test piece was produced in the same manner as in Example 1
except that the above aqueous sealant composition was used.
Example 3
[0079] An aqueous sealant composition was produced in the same
manner as in Example 1 except that as the aqueous dispersion
comprising an olefinic polymer as a main component, 90 parts by
mass of solid content of Arrow Base SB-1010 (manufactured by
Unitika Ltd., content of olefinic polymer (in terms of solid
content): 100 mass %) was used instead of Zaikthene NC, and the
amount of polyvinyl alcohol was changed to 10 parts by mass of
solid content. The total solid content concentration of the
obtained aqueous sealant composition was 35 mass %.
[0080] A test piece was produced in the same manner as in Example 1
except that the above aqueous sealant composition was used.
Comparative Example 1
[0081] An aqueous sealant composition was produced in the same
manner as in Example 1 except that the amount of Zaikthene NC was
changed to 50 parts by mass of solid content and the amount of
polyvinyl alcohol was changed to 50 parts by mass of solid content.
The total solid content concentration of the obtained aqueous
sealant composition was 20 mass %.
[0082] A test piece was produced in the same manner as in Example 1
except that the above aqueous sealant composition was used.
Comparative Example 2
[0083] An aqueous sealant composition was produced in the same
manner as in Example 1 except that as the aqueous dispersion
comprising an olefinic polymer as a main component, 100 parts by
mass of solid content of Arrow Base SB-1010 was used instead of
Zaikthene NC, and no polyvinyl alcohol was used. The total solid
content concentration of the obtained aqueous sealant composition
was 50 mass %.
[0084] A test piece was produced in the same manner as in Example 1
except that the above aqueous sealant composition was used.
TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2
Example 3 example 1 example 2 Aqueous sealant Solid Zaikthene NC
(mass %) 95 90 -- 50 -- composition composition Arrow Base SB-1010
-- -- 90 -- 100 (mass %) Polyvinyl alcohol (mass %) 5 10 10 50 --
Total solid content concentration (mass %) 45 42 35 20 50
Evaluation items Wettability (coating film appearance) Good Good
Good Poor Poor (cracking) (unevenness) Film strength (peel
strength) (N/20 mm) 15 18 25 5 20 Viscosity (mPa .times. s) 180 250
220 5300 80 Flexibility (bending tolerance) Good Good Good Poor
Poor Sealability 1 mass %> 1 mass %> 1 mass %> 5 mass % 7
mass %
[0085] As can be seen from Table 1, it was possible to form a
sealant layer that is excellent in wettability (coating film
appearance), film strength (peel strength), flexibility (bending
tolerance) and sealability, by using an aqueous sealant composition
for a nonaqueous electrolyte battery comprising an aqueous
dispersion in an amount of 70 mass % or more and 97 mass % or less
by mass of solid content, wherein the aqueous dispersion comprises
an olefinic polymer as a main component.
* * * * *