U.S. patent application number 11/578570 was filed with the patent office on 2007-07-19 for aramid thin sheet material and electrical/electronic parts using the same.
Invention is credited to Kazuo Izaki, Yoshihiro Murai, Shinji Naruse.
Application Number | 20070167101 11/578570 |
Document ID | / |
Family ID | 35150039 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070167101 |
Kind Code |
A1 |
Naruse; Shinji ; et
al. |
July 19, 2007 |
Aramid thin sheet material and electrical/electronic parts using
the same
Abstract
The invention provides an aramid thin sheet material comprising
two components of aramid staple fibers and fibrillated aramid, or
said two components and aramid fibrid, in particular, characterized
by satisfying both of the following expressions (1) and (2):
[internal resistance] (.mu.m).ltoreq.250 (.mu.m) expression (1)
[Oken-type gas permeability] (sec/100 cm.sup.3).gtoreq.0.5 (sec/100
cm.sup.3) expression (2) wherein the [internal resistance] is a
resistance value calculated by the following expression (3): [
internal .times. .times. resistance .times. ] .times. ( .mu.
.times. .times. m ) = [ electrical .times. .times. conductivity
.times. of .times. .times. electrolyic .times. .times. solution ] [
electrical .times. .times. conductivity of .times. .times.
electrolytic solution .times. - .times. injected .times. thin
.times. .times. sheet .times. .times. material ] .times. [
thickness .times. of .times. .times. the .times. .times. thinsheet
.times. material ] .times. ( .mu. .times. .times. m ) . expression
.times. .times. ( 3 ) ##EQU1##
Inventors: |
Naruse; Shinji; (Tokyo,
JP) ; Izaki; Kazuo; (Tokyo, JP) ; Murai;
Yoshihiro; (Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
35150039 |
Appl. No.: |
11/578570 |
Filed: |
October 26, 2004 |
PCT Filed: |
October 26, 2004 |
PCT NO: |
PCT/JP04/16198 |
371 Date: |
December 1, 2006 |
Current U.S.
Class: |
442/414 ;
442/327; 442/415 |
Current CPC
Class: |
H01M 50/44 20210101;
H01M 50/411 20210101; Y10T 442/60 20150401; Y10T 442/697 20150401;
Y10T 442/696 20150401; D21H 13/26 20130101; Y02E 60/10
20130101 |
Class at
Publication: |
442/414 ;
442/327; 442/415 |
International
Class: |
D04H 13/00 20060101
D04H013/00; D04H 1/00 20060101 D04H001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2004 |
JP |
2004-122120 |
Claims
1. An aramid thin sheet material comprising two components of
aramid staple fibers and fibrillated aramid, or said two components
and aramid fibrid.
2. An aramid thin sheet material as set forth in claim 1,
characterized by satisfying both of the following expressions (1)
and (2): [internal resistance] (.mu.m).ltoreq.250 (.mu.m)
expression (1) [Oken-type gas permeability] (sec/100
cm.sup.3).gtoreq.0.5 (sec/100 cm.sup.3) expression (2) wherein the
[internal resistance] is a resistance value calculated by the
following expression (3): [ internal .times. .times. resistance
.times. ] .times. ( .mu. .times. .times. m ) = [ electrical .times.
.times. conductivity .times. of .times. .times. electrolyic .times.
.times. solution ] [ electrical .times. .times. conductivity of
.times. .times. electrolytic solution .times. - .times. injected
.times. thin .times. .times. sheet .times. .times. material ]
.times. [ thickness .times. of .times. .times. the .times. .times.
thinsheet .times. material ] .times. ( .mu. .times. .times. m ) .
expression .times. .times. ( 3 ) ##EQU5## wherein [electrical
conductivity of electrolytic solution-injected thin sheet material]
is the electrical conductivity calculated from an AC impedance
measured by sandwiching the electrolytic solution-injected thin
sheet material between two electrodes.
3. Electrical/electronic parts which are characterized by using the
aramid thin sheet material as set forth in claim 1 or 2 as
separator panels between their electrically conductive members.
Description
TECHNICAL FIELD
[0001] This invention relates to aramid thin sheet material useful
as separators for separating conductive members in
electrical/electronic parts to allow passage of ionic species such
as electrolyte or ion; and also to electrical/electronic parts
using the separators. In particular, the invention relates to
aramid thin sheet material useful for separator panels between
electrodes in condensers, capacitors, batteries and the like which
use lithium ion, sodium ion, ammonium ion, hydrogen ion and the
like as a carrier of electric current.
BACKGROUND ART
[0002] As symbolized by the recent progress in portable
communication devices or high-speed information processors,
reduction in size and weight and advance in technical performance
of electronic instruments are splendid. Above all, more expectation
is placed on small size, light weight, and higher capacity and
performance electric batteries and condensers which can withstand
storage over prolonged period. Their application range is being
broadened and developments of parts for their use are under rapid
progress. Correspondingly, there are growing needs for developing
improved technology and quality for such members as separators
which serve as partition plates between electrodes.
[0003] Among various properties required for separators, the
following three are recognized to be particularly important:
[0004] 1) that they exhibit good electrical conductivity in the
state of holding an electrolyte;
[0005] 2) that they have high inter-electrodes shielding
performance; and
[0006] 3) that they have mechanical strength.
[0007] Conventionally, as separators in electrical/electronic
parts, porous sheeting formed of polyolefin polymer such as
polyethylene or polypropylene (cf. JP Sho63(1988)-273651A);
non-woven fabric in which polyolefin polymer fibers such as of
polyethylene or polypropylene are made into sheet (cf.
JP2001-11761A); non-woven fabric in which nylon fibers are made
into sheet (cf. JP Sho58(1983)-147956A) have been widely used. Such
separators are used in batteries in the form of mono-layer,
multiple layers or wound-up roll.
[0008] Furthermore, micropores are formed on the surfaces of
members used in electrodes by
[0009] 1) etching aluminum foil electrodes for aluminum
electrolytic condensers, or
[0010] 2) using activated carbon as electrodes in electric double
layer capacitors,
to increase their surface areas to impart high capacity
thereto.
DISCLOSURE OF THE INVENTION
[0011] Such micro-porous sheeting and non-woven fabrics possess
favorable physical properties for the separator, but do not
necessarily fully meet recent demands for condensers, capacitors or
batteries of still higher capacity and power output required for
electric cars.
[0012] A separator for use in electrical/electronic parts for
condensers, capacitors, batteries and the like which are required
to have high capacity and large power output must simultaneously
satisfy the following five property requirements:
[0013] 1) good electrical conductivity in the state of holding an
electrolyte,
[0014] 2) high inter-electrodes shielding ability,
[0015] 3) high mechanical strength,
[0016] 4) chemical and electrochemical stability (heat resistance),
and
[0017] 5) capability to withstand high temperature drying (heat
resistance).
[0018] In particular, inter-electrodes shielding ability and heat
resistance are considered to be extremely important, for
[0019] 1) preventing short-circuit between conductive members in
electrical/electronic parts using high-intensity electric current
with high-capacity electrodes filled at high density, such as
condensers, capacitors and batteries as drive power source of, for
example, electric cars, and
[0020] 2) thoroughly drying moisture in micropores in electrodes
such as of aluminum foil or activated carbon, during manufacturing
steps of electrical/electronic parts.
[0021] Under the circumstances, the present inventors have engaged
in concentrative studies with the view to develop a material for
highly heat resistant separators which withstand high-intensity
electric current necessitated for higher capacity and large power
output and also are durable under high-temperature drying during
their manufacturing steps, and now come to complete the present
invention.
[0022] Thus the present invention provides aramid thin sheet
material useful as separation panels between conductive members of
electrical/electronic parts such as condensers, capacitors,
batteries and the like, which is characterized by comprising two
components of aramid staple fibers and fibrillated aramid, or said
two components and aramid fibrid.
[0023] The invention also provides above aramid thin sheet material
which is characterized by satisfying both of the following
expressions (1) and (2): [internal resistance] (.mu.m).ltoreq.250
(.mu.m) expression (1) [Oken-type gas permeability] (sec/100
cm.sup.3).gtoreq.0.5 (sec/100 cm.sup.3) expression (2) [0024]
wherein the [internal resistance] is a resistance value calculated
by the following expression (3): [ internal .times. .times.
resistance .times. ] .times. ( .mu. .times. .times. m ) = [
electrical .times. .times. conductivity .times. of .times. .times.
electrolyic .times. .times. solution ] [ electrical .times. .times.
conductivity of .times. .times. electrolytic solution .times. -
.times. injected .times. thin .times. .times. sheet .times. .times.
material ] .times. [ thickness .times. of .times. .times. the
.times. .times. thinsheet .times. material ] .times. ( .mu. .times.
.times. m ) . expression .times. .times. ( 3 ) ##EQU2## [0025]
wherein [electrical conductivity of electrolytic solution-injected
thin sheet material] is the electrical conductivity calculated from
an AC impedance measured by sandwiching the electrolytic
solution-injected thin sheet material between two electrodes.
[0026] This invention also provides electrical/electronic parts
such as condensers, capacitors, batteries and the like,
characterized by using the aramid thin sheet material of the
present invention as separator panels between their electrically
conductive members.
[0027] Hereinafter the present invention is explained in further
details.
(Aramid)
[0028] In the present invention, "aramid" signifies a linear high
molecular weight compound in which at least 60% of amide linkages
directly bind to aromatic ring. As such aramid, for example,
polymetaphenylene isophthalamide and copolymers thereof,
polyparaphenylene terephthalamide and copolymers thereof,
poly(paraphenylene)-copoly(3,4-diphenylether)terephthalamide and
the like can be named. These aramids are industrially manufactured
by known interfacial polymerization, solution polymerization or the
like using, for example, isophthalic acid chloride and
mataphenylenediamine and are available on the market, but are not
limited thereto. Of these aramids, polymetaphenylene isophthalamide
is used with preference, because of its favorable shaping
processability, heat-adherability, flame resistance and heat
resistance properties.
(Aramid Fibrid)
[0029] In the present invention, "aramid fibrid" signify filmy
aramid particles having paper-forming ability, which are also
referred to as aramid pulp (see: JP Sho 35(1960)-11851B, JP Sho
37(1962)-5752B).
[0030] It is widely known that aramid fibrid is useful as
paper-forming material, after maceration and beating treatment,
similarly to ordinary wood pulp. With the view to maintain the
quality adequate for paper-forming, aramid fibrid can be given a
"beating" treatment. This beating treatment can be worked with disc
refiner, beater, or other paper-forming material processing machine
or instrument which exerts mechanical cutting action. In such
operation, morphological change in the fibrid can be monitored by
freeness test method prescribed by The Japanese Industrial
Standards P8121.
[0031] In the present invention, freeness of the aramid fibrid
after the beating treatment preferably lies within a range of
10-300 cm.sup.3, in particular, 10-80 cm.sup.3 (Canadian freeness).
With fibrid having the freeness more than the specified range, the
aramid thin sheet material formed therefrom is liable to have
reduced strength. On the other hand, attempts to achieve freeness
less than 10 cm.sup.3 reduce utilization efficiency of mechanical
power projected and often decrease processing quantity per unit
time. Furthermore, because such excessively advances pulverization
of the fibrid, it is apt to invite deterioration in "binder"
function. Hence, no substantial merit is found in attempts to
obtain freeness less than 10 cm.sup.3.
[0032] For the utility intended in the present invention, aramid
fibrid preferably has a weight-average fiber length after the
beating treatment, as measured with optical fiber length measuring
apparatus, not more than 1.5 mm, in particular, within a range of
1.2-0.6 mm. As the optical fiber length measuring apparatus, Fiber
Quality Analyzer (Op Test Equipment Co.), KAJAANI Measuring
Equipment (Kajaani Co.) or the like can be used. With such an
equipment, fiber length and form of aramid fibrid passing a certain
light path are observed individually and the measured fiber lengths
are statistically processed. Where the weight-average fiber length
of the aramid fibrid to be used exceeds 1 mm, reduction in
electrolytic solution absorbency, occurrence of localized failure
of impregnation with the electrolyte, and consequential rise in
internal resistance of electrical/electronic parts are liable to
take place.
(Aramid Staple Fiber)
[0033] Aramid staple fiber is provided by cutting fibers of which
starting material is aramid, examples of which include those
available under the tradenames of Teijin CONEX.RTM. (Teijin Ltd.),
TECHNORA.RTM. (Teijin Ltd.), APIER.RTM. (UNITIKA Ltd.) NOMEX.RTM.
and KEVLAR.RTM. (E. I. du Pont de Nemours and Company) and
TWARON.RTM. (Teijin Twaron Co.), but not limited thereto.
[0034] Aramid staple fiber preferably has a fineness within a range
of 0.05 dtex-less than 25 dtex, in particular, 0.1-2 dtex. Here the
fineness is defined as fiber weight (g) per 1000 m. Fibers having a
fineness less than 0.05 dtex are objectionable as they tend to
invite agglomeration during wet process preparation (explained
later), and fibers having a fineness of 25 dtex or more tend to
have excessively large fiber diameter. For example, where the
fibers have a round cross-section and have a density of 1.4
g/cm.sup.3, fibers having a diameter of 45.mu. or more are liable
to cause such defects as decrease in aspect ratio, reduction in
mechanical reinforcing effect, non-uniformity of aramid thin sheet
material or the like. Here non-uniformity of aramid thin sheet
material signifies broadening in void size distribution to cause
non-uniformity in mobility of aforesaid ion species.
[0035] The length of aramid staple fibers can be selected between 1
mm to less than 50 mm, in particular, 2-10 mm. Where the length of
the staple fibers is less than 1 mm, mechanical characteristics of
aramid thin sheet material are deteriorated, and when it is 50 mm
or more, tangle or stuck is apt to take place during preparation of
aramid thin sheet material by later described wet process to induce
further defects.
(Fibrillated Aramid)
[0036] Fibrillated aramid is formed by fibrillating aramid fibers,
aramid fibrid and the like by exertion of shearing force, which
preferably has a freeness within a range of 10-800 cm.sup.3, in
particular, 30-700 cm.sup.3 (Canadian freeness). Fibrillated aramid
having a freeness greater than the above range is liable to provide
insufficient shielding property between electrodes. On the other
hand, attempts to obtain the freeness less than 10 cm.sup.3
excessively advance fineness of fibrillated aramid, which is apt to
invite deterioration in its binder function. Therefore, no
particular merit is found in achieving a freeness less than 10
cm.sup.3.
[0037] Fibrillated aramid preferably has a specific surface area of
at least 5 g/m.sup.2, in particular, 6-20 g/m.sup.2. When it is
less than 5 g/m.sup.2, reduction in binder function is apt to be
invited. Furthermore, its weight-average fiber length can be
selected from a range of 0.01 mm-less than 7 mm, in particular,
0.3-3 mm. Fibrillated aramid having greater weight-average fiber
length than the specified range shows poor dispersibility during
paper-forming operation, which may cause local defect in formed
aramid thin sheet material such as formation of stuck filament. On
the other hand, attempts to obtain weight-average fiber length less
than 0.01 mm promote excessive pulverization of fibrillated aramid
and are liable to invite reduction in its binder function.
[0038] Specific examples of fibrillated aramid are available under
such tradenames as KEVLAR PULP (E. I. du Pont de Nemours and
Company), TWARON PULP (Teijin Twaron Co.) and the like, but are not
limited thereto.
(Aramid Thin Sheet Material)
[0039] The aramid thin sheet material of the present invention is
characterized by being constituted of the two components, i.e.,
above-described aramid staple fibers and fibrillated aramid, or of
the two components plus aramid fibrid, and can have optional aramid
staple fiber content, fibrillated aramid content, aramid fibrid
content, basis weight and density (basis weight/thickness) within
the range satisfying the following two expressions (1) and (2):
[internal resistance] (.mu.m).ltoreq.250 (.mu.m) expression (1)
[Oken-type gas permeability] (sec/100 cm.sup.3).gtoreq.0.5 (sec/100
cm.sup.3) expression (2) preferably [internal resistance]
(.mu.m).ltoreq.230 (.mu.m) expression (1) [Oken-type gas
permeability] (sec/100 cm.sup.3).gtoreq.1 (sec/100 cm.sup.3)
expression (2) [0040] wherein the [internal resistance] (.mu.m) is
a resistance calculated by the following expression (3): [ internal
.times. .times. resistance .times. ] .times. ( .mu. .times. .times.
m ) = [ electrical .times. .times. conductivity .times. of .times.
.times. electrolyic .times. .times. solution ] [ electrical .times.
.times. conductivity of .times. .times. electrolytic solution
.times. - .times. injected .times. thin .times. .times. sheet
.times. .times. material ] .times. [ thickness .times. of .times.
.times. the .times. .times. thinsheet .times. material ] .times. (
.mu. .times. .times. m ) . expression .times. .times. ( 3 )
##EQU3## [0041] said [electrical donductivity of electrolytic
solution-injected thin sheet material] being the electrical
conductivity calculated from AC impedance measured by sandwiching
the electrolytic solution-injected thin sheet material between two
electrodes. Generally preferred aramid staple fiber content is
within a range of 20-80%, in particular, 30-70%. When the thin
sheet material contains more aramid staple fibers than this range,
binder component becomes insufficient and the paper-forming may
become difficult. On the other hand, the aramid staple fiber
content of less than 20% is liable to cause reduction in
electrolytic solution absorbence, local occurrence of areas not
impregnated with the electrolytic solution and furthermore rise in
internal resistance of electrical/electronic parts.
[0042] As to the contents of the components other than aramid
staple fibers, it is generally preferred that the fibrillated
aramid content is more than that of aramid fibrid. Where aramid
fibrid content is increased, the thin sheet material is liable to
show reduction in electrolytic solution absorbence, local
occurrence of areas not impregnated with the electrolytic solution,
and furthermore rise in internal resistance of the
electrical/electronic parts using the thin sheet material as
separators.
[0043] Again, the aramid thin sheet material preferably has a
thickness generally within a range of 5 .mu.m-150 .mu.m, in
particular, 5 .mu.m-60 .mu.m. Where the thickness is less than 5
.mu.m, the thin sheet material shows reduced mechanical properties
and is apt to cause problems in handlability such as retention of
separator shape, transportation in production steps and the like.
On the other hand, the thickness exceeding 150 .mu.m tends to
invite increase in internal resistance and, above all, makes it
difficult to produce small-size high performance
electrical/electronic parts.
[0044] Furthermore, the aramid thin sheet material can generally
have a basis weight within a range of 5-150 g/m.sup.2, in
particular, 5-50 g/m.sup.2. Where the basis weight is less than 5
g/m.sup.2, the thin sheet material shows insufficient mechanical
strength and is apt to cause breakage during the various handling
in the parts-manufacturing steps such as impregnation treatment
with electrolyte, winding-up and the like. On the other hand,
aramid thin sheet material having a basis weight more than 150
g/m.sup.2 has increased thickness and tends to cause insufficient
impregnation with, or infiltration of, electrolyte.
[0045] Density of aramid thin sheet material is calculated from
basis weight/thickness, which may be normally within a range of
0.1-1.2 g/m.sup.3, in particular, 0.1-1.0 g/m.sup.3.
[0046] Aramid thin sheet materials failing to satisfy the
expressions (1) and (2) are liable to cause such troubles as (1)
excessive increase in internal resistance of electrical/electronic
parts to interfere with their normal actions, (2) failure to
maintain shielding performance between electrodes to induce short
circuit, when compressed as being sandwiched between electrodes
filled at high density.
(Production Method of Aramid Thin Sheet Material)
[0047] The aramid thin sheet material of the present invention,
which has the characteristic features as described in the
foregoing, can be generally prepared by mixing above-described
aramid stable fibers with fibrillated aramid, or aramid staple
fibers with fibrillated aramid and aramid fibrid at desired ratios,
and thereafter sheeting the mixture. More specifically, for
example, such a method comprising dry-blending above aramid staple
fibers with fibrillated aramid, or aramid staple fibers with
fibrillated aramid and aramid fibrid, and thereafter forming a
sheet thereof utilizing gaseous current; one comprising dispersing
and mixing aramid staple fibers with fibrillated aramid, or aramid
staple fibers with fibrillated aramid and aramid fibrid, in a
liquid medium, and thereafter discharging the mixture on a
liquid-permeable support, e.g., net or belt for sheeting, whereby
removing the liquid and drying the residue; or the like can be
applied. Of these, one normally referred to as wet paper-forming
method which uses water as the medium is preferred.
[0048] Such a wet paper-forming method is generally practiced by
feeding an aqueous slurry of a two- or three-component mixture
containing at least aramid staple fibers and fibrillated aramid, or
aramid staple fibers, fibrillated aramid and aramid fibrid, to a
paper machine and dispersing the same; de-watering, squeezing,
drying to convert it into a sheet form and taking it up. As the
paper machine, Fourdrinier machine, cylinder paper machine,
inclined paper machine or combination paper machine combining those
can be used. In the preparation using a combination paper machine,
composite sheet composed of plural paper layers can be obtained by
sheet-forming slurries of differing blend ratios and integrating
them. In the occasion of paper-forming, additives such as
dispersibility improving agent, defoaming agent, strength-enhancing
agent and the like may be added, where necessary. Besides such
additives, other fibrous components (e.g., organic fibers such as
polyphenylene sulfide fibers, polyester ether ketone fibers,
cellulose fibers, PVA fibers, polyester fibers, acrylate fibers,
liquid crystalline polyester fibers, polyethylene naphthalate
fibers and the like; inorganic fibers such as glass fibers, rock
wool, asbestos, boron fibers and the like) may also be added. Where
such other fibrous component(s) are added, their preferred blend
ratio is 10% or less, based on the total weight of all of the fiber
components.
[0049] So obtained aramid thin sheet material can be imparted with
increased density and mechanical strength by, for example,
hot-pressing it at high temperature and high pressure as sandwiched
between a pair of flat plates or metal rolls. The hot-pressing
conditions can be, for example, where metallic rolls are used,
100-400.degree. C. in temperature range and 50-400 kg/cm in linear
pressure range, but are not limited thereto. The material may also
be simply pressed at ambient temperature, without the heating
treatment. In the procedure of hot-pressing, plural sheets of the
thin sheet material may be laminated. The hot-press processing may
be repeated optional number of times by an optional order.
[0050] The aramid thin sheet material of the present invention can
be used as laminated with known other separator (e.g., polyolefine
microporous membrane) by per se known means (e.g., above hot-press
processing) for further increasing its strength.
[0051] The aramid thin sheet material of the present invention can
be favorably used as separator panels in electrical/electronic
parts, because of (1) its excellent properties such as heat
resistance and flame resistance; (2) excellent
electrolyte-retaining function attributable to its void structure;
and (3) aramid's light weight as demonstrated by its low specific
density of around 1.4.
[0052] Thus, electrical/electronic parts such as condensers,
capacitors and batteries manufactured with use of the aramid thin
sheet material of the present invention as separator panels between
electrically conductive members show high shielding property
between electrodes and maintain high safety. Also due to the
material's inherently high heat resistance, the
electrical/electronic parts achieve the effect of withstanding the
use under heavy current environment of hybrid cars, electric cars
and the like.
(Internal Resistance)
[0053] The [internal resistance] which characterizes the aramid
thin sheet material of the present invention is the resistance
which is calculated according to the following expression (3): [
internal .times. .times. resistance .times. ] .times. ( .mu.
.times. .times. m ) = [ electrical .times. .times. conductivity
.times. of .times. .times. electrolyic .times. .times. solution ] [
electrical .times. .times. conductivity of .times. .times.
electrolytic solution .times. - .times. injected .times. thin
.times. .times. sheet .times. .times. material ] .times. [
thickness .times. of .times. .times. the .times. .times. thinsheet
.times. material ] .times. ( .mu. .times. .times. m ) . expression
.times. .times. ( 3 ) ##EQU4## [0054] said [electrical donductivity
of electrolytic solution-injected thin sheet material] being the
electrical conductivity calculated from AC impedance measured by
sandwiching the electrolytic solution-injected thin sheet material
between two electrodes.
[0055] Here the "electrolytic solution" signifies a liquid formed
by dissolving an electrolyte in a solvent.
[0056] In the present invention, kinds of solvent and electrolyte
useful for the electrolytic solution and concentration of the
electrolyte are subject to no particular limitation. As examples of
the solvent, ethylene carbonate, propylene carbonate, dimethyl
carbonate, diethyl carbonate, ethylmethyl carbonate, butylene
carbonate, glutaronitrile, adiponitrile, acetonitrile,
methoxyacetonitrile, 3-methoxypropionitrile, .gamma.-butyrolactone,
.gamma.-valerolactone, sulfolane, 3-methylsulfolane, nitroethane,
nitromethane, trimethyl phosphate, N-methyloxazolidinone,
N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide,
N,N'-dimethylimidazolidinone, amidine, water, and mixtures of two
or more of the foregoing can be named.
[0057] Electrolyte includes ionic substances, and as the ionic
components of the substances, for example, following combinations
of cations with anions can be named:
[0058] 1) cation; quaternary ammonium ion, quaternary phosphonium
ion, lithium ion, sodium ion, ammonium ion, hydrogen ion and
mixtures of the foregoing
[0059] 2) anion; perchlorate ion, borofluoride ion,
hexafluorophosphate ion, sulfate ion, hydroxide ion and mixtures of
the foregoing.
[0060] (Electrical conductivity of electrolytic solution-injected
thin sheet material) in the present invention is the electrical
conductivity calculated from AC impedance as measured by
sandwiching the electrolytic solution-injected thin sheet material
between two electrodes. Measuring frequency for the AC impedance is
not critical, but the normally preferred range is 1 kHz-100
kHz.
EXAMPLES
[0061] Hereinafter the present invention is explained more
specifically, referring to working examples. It should be
understood, however, these examples are for illustration only and
are never for restricting the scope of the present invention.
<Measuring Methods>
(1) BW (Basis Weight) and Thickness Measurement of Sheet
[0062] Those methods as prescribed by JIS C2111 were followed.
(2) Measurement of Electrical Conductivity
[0063] A disc of 20 mm in diameter was cut out from a thin sheet
material, which was sandwiched between two sheets of SUS electrodes
and AC impedance at 60 kHz was measured as the basis for the
conductivity calculation. The measuring temperature was 25.degree.
C. For the measurement, 1M lithium borofluoride solution in
ethylene carbonate/propylene carbonate (1:1 by weight) was used as
the electrolytic solution.
(3) Gas Permeability
[0064] Gas permeability was measured with Oken-type gas
permeability meter. As to all of the thin sheet materials measured
in the present invention, the less this time, the more porous the
material.
(Preparation of Starting Materials)
[0065] By the method using a wet precipitation machine composed of
stator/rotor combination as described in JP Sho52(1977)-151624B,
fibrid of polymetaphenylene isophthalamide was prepared, which was
processed with macerator and beater to adjust its weight-average
fiber length to 0.9 mm.
[0066] Separately, metaramid fibers (Teijin CONEX.RTM., Teijin
Ltd.) having a staple fineness of 0.8 denier) were cut into 5 mm in
length. Also TWARON pulp (TWARON.RTM., Teijin Twaron Co.) was
processed to have a specific surface area of 14 m.sup.2/g and a
freeness of 85 mL; and polyester staple fibers (TETORON.RTM.,
Teijin Ltd., staple fineness=0.1 denier) were cut to 5 mm in
length. Those were used as the starting materials for
paper-forming.
Examples 1 and 2
(Preparation of Aramid Thin Sheet Material)
[0067] Each of the aramid fibrid, aramid staple fibers and
fibrillated aramid prepared in the foregoing manner was dispersed
in water to form a slurry. Those slurries were mixed to make the
blend ratios of the aramid fibrid, aramid staple fibers and
fibrillated aramid the values as indicated in Table 1, to form
sheet-formed products with TAPPI sheet machine (cross-sectional
area=325 cm.sup.2). The products were then given a hot-press
processing with metallic calendar rolls at a temperature of
330.degree. C. and linear pressure of 100 kg/cm to provide thin
sheet materials.
[0068] Main parameter values of thus obtained aramid thin sheet
materials were as shown in Table 1. TABLE-US-00001 TABLE 1 Physical
Property Unit Example 1 Example 2 Composition of starting material
wt % Aramid fibrid 0 1 Aramid staple fiber 50 49 Fibrillated aramid
50 50 Basis weight g/m.sup.2 24.5 24.4 Thickness .mu.m 51 47
Density g/cm.sup.3 0.48 0.52 Electrical conductivity mS/cm 1.37
1.04 Internal resistance .mu.m 186 245 Gas permeability sec/100
cm.sup.3 1.8 4.8
[0069] Electrical conductivity of the electrolytic solution was 5.0
(mS/cm).
[0070] The aramid thin sheet materials of those Examples had
sufficiently low internal resistance, exhibited satisfactory ion
species' permeability and gas permeability, and were considered to
be fully capable of maintaining shielding property between
electrodes. Accordingly, the products are useful as separator
panels of electrically conductive members in electrical/electronic
parts such as condensers, capacitors, batteries and the like.
Comparative Example 1
(Preparation of Thin Sheet Material)
[0071] Each of the aramid fibrid, aramid staple fibers and TETORON
staple fibers as prepared in the foregoing manner was dispersed in
water to form a slurry. The slurries were mixed to make the blend
ratio of the fibrid and aramid staple fibers the value as indicated
in Table 2, to form a sheet-formed product by wet paper-forming
method.
[0072] The product was then given a hot-press processing with
metallic calendar rolls at a temperature of 230.degree. C. and
linear pressure of 300 kg/cm to provide a thin sheet material.
[0073] Main parameter values of thus obtained thin sheet material
were as shown in Table 2. TABLE-US-00002 TABLE 2 Comparative
Physical Property Unit Example Composition of starting material wt
% Aramid fibrid 7 Aramid staple fiber 10 Polyester staple fiber 83
Basis weight g/m.sup.2 25 Thickness .mu.m 42 Density g/cm.sup.3 0.6
Electrical conductivity mS/cm 0.60 Internal resistance .mu.m 350
Gas permeability sec/100 cm.sup.3 72
[0074] Electrical conductivity of the electrolytic solution was 5.0
(mS/cm).
[0075] The thin sheet material of Comparative Example had a high
internal resistance and was considered to have insufficient ion
species' permeability. Furthermore, because polyester staple fiber
was used, the product would not withstand high temperature
drying.
Industrial Applicability
[0076] The aramid thin sheet material of the present invention can
fully maintain shielding property between electrodes and exhibit
satisfactory permeability for ion species, and therefore are useful
as separator panels for electrically conductive members in
electrical/electronic parts such as condensers, capacitors,
batteries and the like. Furthermore, the electrical/electronic
parts such as condensers, capacitors, batteries and the like in
which the aramid thin sheet material of the present invention is
used can be dried at high temperatures concurrently with
microporous aluminum foil electrodes, active carbon electrodes and
the like integrated therein during their manufacturing steps,
accomplishing the effect that no deletrious influence of residual
moisture on electrical characteristics of the electrical/electronic
parts is observed.
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