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SPECIFICATION
ASK-8704
POLYMER ELECTROLYTE COMPOSITION CONTAINING AROMATIC
HYDROCARBON-BASED RESIN
TECHNICAL FIELD
The present invention relates to a polymer
electrolyte composition and a proton exchange membrane
comprising the composition, which is used for solid
polymer electrolyte fuel cells.
BACKGROUND OF THE INVENTION
A fuel cell is a cell in which hydrogen, methanol or
the like is electrochemically oxidized and thereby the
chemical energy of fuel is directly converted into an
electric energy and taken out, and this is attracting
attention as a clean electric energy supply source. In
particular, a solid polymer electrolyte fuel cell works
at a low temperature as compared with others and is
expected to be an automobile alternative power source, a
domestic cogeneration system, a portable generator or the
like.
The solid polymer electrolyte fuel cell comprises at
least a membrane electrode assembly in which a gas
diffusion electrode obtained by stacking an electrode
catalyst layer and a gas diffusion layer is joined on
each of both surfaces of a proton exchange membrane. The
proton exchange membrane as used herein means a material
having a strongly acidic group such as sulfonic acid
group and carboxylic acid group in the polymer chain and
having a property of selectively passing a proton. The
proton exchange membrane which is suitably used is a
perfluoro-based proton exchange membrane as represented
by Nafion (registered trademark, produced by du Pont)
having high chemical stability.
During the operation of a fuel cell, a fuel (e. g.,
hydrogen) is supplied to the gas diffusion electrode on
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the anode side, an oxidizing agent (e.g., oxygen, air) is
supplied to the gas diffusion electrode on the cathode
side, and both electrodes are connected through an
external circuit, thereby actuating the fuel cell. More
specifically, when the fuel is hydrogen, the hydrogen is
oxidized on an anode catalyst to produce a proton, and
this proton passes through a proton conductive polymer in
the anode catalyst layer, then moves in the proton
exchange membrane and passes through a proton conductive
polymer in the cathode catalyst layer to reach on the
cathode catalyst. On the other hand, an electron
produced simultaneously with the proton by the oxidation
of hydrogen passes through the external circuit to reach
the gas diffusion electrode on the cathode side and
reacts with the proton and oxygen in the oxidizing agent
to produce water, and an electric energy can be taken out
at this time.
In this case, the proton exchange membrane must act
also as a gas barrier and if the gas permeability of the
proton exchange membrane is high, the hydrogen on the
anode side leaks toward the cathode side and the oxygen
on the cathode side leaks toward the anode side, that is,
a cross leakage is generated, as a result, a so-called
chemical short state is produced and a good voltage
cannot be taken out.
The solid polymer electrolyte fuel cell is usually
operated at around 80°C in order to bring out high output
properties, but in usage for automobiles, assuming travel
of an automobile in the summer season, the fuel cell is
required to be operable even under high-temperature low-
humidification conditions (an operation temperature in
the vicinity of 100°C with 50°C humidification
(corresponding to a humidity of 12 RHo)). However, when
a fuel cell using a conventional perfluoro-based proton
exchange membrane is operated for a long time under high-
temperature low-humidification conditions, this causes a
problem in that pinholes are generated in the proton
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exchange membrane and cross-leakage is brought about, and
sufficiently high durability is not obtained.
With respect to the method for enhancing the
durability of the perfluoro-based proton exchange
membrane, studies have been reported to enhance the
durability by the reinforcement using a fibrillated
polytetrafluoroethylene (PTFE) (see, Japanese Unexamined
Patent Publication (Kokai) No. 53-149881 and Japanese
Examined Patent Publication (Kokoku) No. 63-61337), the
reinforcement using a stretched PTFE porous film (see,
Kokai No. 8-162132), the reinforcement of adding
inorganic particles (see, Kokai Nos. 6-111827 and 9-
219206 and U.S. Patent No. 5,523,181), or the
reinforcement using a porous body comprising an aromatic
ring-containing resin (see, Kokai Nos. 2001-514431 and
2003-297393). However, in these methods, durability
sufficiently high to solve the above-described problems
cannot be achieved.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a
polymer electrolyte composition ensuring high durability
even under high-temperature low-humidification conditions
(for example, an operation temperature of 100°C with 50°C
humidification (corresponding to a humidity of 12 RHo)),
and a proton exchange membrane comprising the polymer
electrolyte composition.
As a result of intensive investigations to attain
the above-described object, the present inventors have
found that a polymer electrolyte composition comprising
(A) a polymer compound having an ion exchange group, (B)
a polyphenylene sulfide resin, and at least one resin
selected from (C) a polyphenylene ether resin and (D) a
polysulfone resin exhibits high oxidization stability,
and a proton exchange membrane comprising this polymer
electrolyte composition has excellent durability even at
a high temperature with low humidification.
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That is, the present invention is as follows.
[1] A polymer electrolyte composition comprising
(A) a polymer compound having an ion exchange group, (B)
a polyphenylene sulfide resin, and at least one resin
selected from (C) a polyphenylene ether resin and (D) a
polysulfone resin.
[2] A polymer electrolyte composition as described
in [1] above, wherein the polyphenylene ether resin (C)
is an epoxy-modified polyphenylene ether (E).
[3] A polymer electrolyte composition as described
in [1] or [2] above, which comprises (A) a polymer
compound having an ion exchange group, (B) a
polyphenylene sulfide resin, (C) a polyphenylene ether
resin and (F) an epoxy group-containing compound.
[4] A polymer electrolyte composition as described
in [3] above, wherein the epoxy group-containing compound
(F) is a homopolymer or copolymer of an unsaturated
monomer having an epoxy group (G).
[5] A polymer electrolyte composition as described
in [4] above, wherein the epoxy group-containing compound
(F) is a copolymer comprising an unsaturated monomer
having an epoxy group and a styrene monomer (G).
[6] A polymer electrolyte composition as described
in [3] above, wherein the epoxy group-containing compound
(F) is an epoxy resin (H).
[7] A polymer electrolyte composition as described
in [6] above, which comprises (E) an epoxy-modified
polyphenylene ether resulting from a reaction at least
partially proceeding between the polyphenylene ether
resin (C) and the epoxy resin (H) in the polymer
electrolyte composition.
[8] A polymer electrolyte composition as described
in any one of [1] to [7] above, wherein the polymer
compound having an ion exchange group (A) is a
perfluorocarbon polymer compound having an ion exchange
group.
[9] A polymer electrolyte composition as described
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in [8] above, wherein the perfluorocarbon polymer
compound having an ion exchange group has a structural
unit represented by the following formula (1):
- [CFZCX1X2] a- [CFz-CF (-O- (CFz-CF (CFZX3) ) b-0~- (CFR1) a-
(CFR2)e-(CF2)f-X4) ]g- (1)
wherein X1, X2 and X3 each is independently a halogen atom
or a perfluoroalkyl group having from 1 to 3 carbon
atoms, a and g are 0Sa<l, 0<g<_1 and a+g=l, b is an integer
of 0 to 8, c is 0 or l, d, a and f each is independently
an integer of 0 to 6 (with the proviso that d+e+f is not
0), R1 and Rz each is independently a halogen element or a
perfluoroalkyl or fluorochloroalkyl group having from 1
to 10 carbon atoms, and X4 is COOZ, S03Z, P03Z2 or P03HZ
(wherein Z is a hydrogen atom, an alkali metal atom, an
alkaline earth metal atom or an amine (e. g., NHq, NH3R1,
NHZR1R2, NHR1RZR3, NRIRzR3R4 ) , and Rl, R2, R3 and RQ each is
an alkyl group or an arene group).
[10] A polymer electrolyte composition as described
in any one of [1] to [9] above, wherein particles
comprising one or more resin selected from the
polyphenylene sulfide resin (B), the polyphenylene ether
resin (C) and the polysulfone resin (D) are dispersed in
the polymer compound having an ion exchange group (A),
and the equivalent-circle average particle diameter of
the particles is 1 ~m or less.
[11] A polymer electrolyte composition as described
in any one of [3] to [9] above, wherein particles
comprising one or more resin selected from the
polyphenylene sulfide resin (B), the polyphenylene ether
resin (C) and the epoxy group-containing compound (F) are
dispersed in the polymer compound having an ion exchange
group (A), and the equivalent-circle average particle
diameter of the particles is 1 ~m or less.
[12] A polymer electrolyte composition as described
in [10] or [11], wherein the region allowing for
dispersion of particles occupies from 50 to 1000 in the
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entire region of the polymer electrolyte composition.
[13] A proton exchange membrane comprising the
polymer electrolyte composition described in any one of
[1] to [12] above.
[14] A proton exchange membrane as described in [13]
above, wherein the membrane has a thickness of 5 to 200
Vim; the polymer compound having an ion exchange group (A)
is a perfluorocarbon polymer compound having an ion
exchange group; and the polyphenylene sulfide resin (B)
and at least one resin selected from the polyphenylene
ether resin (C) and the polysulfone resin (D) are melt-
mixed under heating with a precursor of the
perfluorocarbon polymer compound having an ion exchange
group and then extrusion-molded, and the obtained film is
saponified with an alkali and then acid-treated, thereby
producing the proton exchange membrane.
[15] A proton exchange membrane as described in [13]
above, wherein the membrane has a thickness of 5 to 200
Vim; the polymer compound having an ion exchange group (A)
is a perfluorocarbon polymer compound having an ion
exchange group; and the polyphenylene sulfide resin (B),
the polyphenylene ether resin (C) and the epoxy group-
containing compound (F) are melt-mixed under heating with
a precursor of the perfluorocarbon polymer compound
having an ion exchange group and then extrusion-molded,
and the obtained film is saponified with an alkali and
then acid-treated, thereby producing the proton exchange
membrane.
[16] A proton exchange membrane as described in [14]
or [15] above, wherein the extrusion molding is inflation
molding.
[17] A proton exchange membrane as described in any
one of [13] to [16] above, which is stretched at a draw
ratio of 1.1 to 6.0 times in the transverse direction
(TD), at a draw ratio of 1.0 to 6.0 times in the machine
direction (MD) and at an area draw ratio of 1.1 to 36
times.
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[18] A proton exchange membrane as described in any
one of [13] to [17] above, wherein at least two proton
exchange membranes differing in the compositional ratio
of the polymer electrolyte composition are stacked.
[19] A proton exchange membrane as described in [18]
above, wherein the polymer electrolyte composition
comprises (A) the polymer compound having an ion exchange
group, (B) the polyphenylene sulfide resin, (C) the
polyphenylene ether resin and (F) the epoxy group-
containing compound.
[20] A proton exchange membrane as described in [18]
or [19], wherein a proton exchange membrane comprising at
least two polymer electrolyte compositions differing in
the content of the polymer compound having an ion
exchange group (A) is stacked at least in three layers,
and the inner layer smaller in the A content than at
least either one surface layer occupies from 5 to 90% of
the entire layer thickness.
[21] A proton exchange membrane as described in [18]
or [19], wherein a proton exchange membrane comprising at
least two polymer electrolyte compositions differing in
the content of the polymer compound having an ion
exchange group (A) is stacked at least in three layers,
the surface layer is lower in the A content than in the
inner layer, and the thickness of the surface layer
occupies from 5 to 500 of the entire layer thickness.
[22] A proton exchange membrane as described in any
one of [13] to [21], which comprises a reinforcing
material comprising an inorganic or organic material.
[23] A proton exchange membrane as described in [22]
above, wherein the reinforcing material is a staple fiber
substance.
[24] A proton exchange membrane as described in [22]
above, wherein the reinforcing material is a continuous
support.
[25] A membrane electrode assembly comprising the
proton exchange membrane described in any one of [13] to
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[24] above.
[26] A solid polymer electrolyte fuel cell
comprising the membrane electrode assembly described in
[25] above.
The proton exchange membrane comprising the polymer
electrolyte composition of the present invention is free
from generation of cross-leakage and exhibits excellent
durability even when a fuel cell is operated for a long
time at an operation temperature of 100°C with 50°C
humidification (corresponding to a humidity of 12 RHo),
so that a proton exchange membrane ensuring high
durability even under high-temperature low-humidification
conditions (for example, an operation temperature of 100°C
with 50°C humidification (corresponding to a humidity of
12 RHo)) can be obtained.
The proton exchange membrane obtained according to
the present invention is usable also for various fuel
cells including a direct methanol-type fuel cell as well
as for water electrolysis, hydrogen halide acid
electrolysis, sodium chloride electrolysis, oxygen
concentrator, moisture sensor, gas sensor and the like.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The polymer compound having an ion exchange group
(A) for use in the present invention is preferably, for
example, a perfluorocarbon polymer compound having an ion
exchange group, or a hydrocarbon-based polymer compound
having an aromatic ring within the molecule, in which an
ion exchange group is introduced. Specific examples of
the hydrocarbon-based polymer having an aromatic ring
within the molecule include polyphenylene sulfide,
polyphenylene ether, polysulfone, polyethersulfone,
polyether ether sulfone, polyether ketone, polyether
ether ketone, polythioether ether sulfone, polythioether
ketone, polythioether ether ketone, polybenzimidazole,
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polybenzoxazole, polyoxadiazole, polybenzoxadinone,
polyxylylene, polyphenylene, polythiophene, polypyrrole,
polyaniline, polyacene, polycyanogen, polynaphthylidine,
polyphenylene sulfide sulfone, polyphenylenesulfone,
polyimide, polyetherimide, polyesterimide,
polyamidoimide, polyarylate, aromatic polyamide,
polystyrene, polyester and polycarbonate. Among these,
in view of resistance against heat, oxidation and
hydrolysis, preferred are polyphenylene sulfide,
polyphenylene ether, polysulfone, polyethersulfone,
polyether ether sulfone, polyether ketone, polyether
ether ketone, polythioether ether sulfone, polythioether
ketone, polythioether ether ketone, polybenzimidazole,
polybenzoxazole, polyoxadiazole, polybenzoxadinone,
polyxylylene, polyphenylene, polythiophene, polypyrrole,
polyaniline, polyacene, polycyanogen, polynaphthylidine,
polyphenylene sulfide sulfone, polyphenylenesulfone,
polyimide and polyetherimide. The ion exchange group
introduced into these compounds is, for example,
preferably a sulfonic acid group, a sulfonamide group, a
sulfonamide group, a carboxylic acid group or a
phosphoric acid group, more preferably a sulfonic acid
group.
In particular, the polymer compound having an ion
exchange group (A) for use in the present invention is
preferably a perfluorocarbon polymer compound having an
ion exchange group.
Suitable examples of the perfluorocarbon polymer
compound having an ion exchange group include sulfonic
acid polymer, carboxylic acid polymer, sulfonamide
polymer, sulfonamide polymer and phosphoric acid polymer
of perfluorocarbon, and amine salts and metal salts
thereof. Specific examples thereof include a polymer
represented by the following formula (1):
- [CF2CX1X2] a- [CFZ-CF (-0- (CF2-CF (CFZX3) ) b-0~- (CFR1) d-
( CFR2 ) e- ( CFz ) f-X9 ) l g- ( 1 )
wherein X1, X2 and X3 each is independently a halogen atom
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or a perfluoroalkyl group having from 1 to 3 carbon
atoms, a and g are 0_<a<l, 0<g<_1 and a+g=I, b is an integer
of 0 to 8, c is 0 or l, d, a and f each is independently
an integer of 0 to 6 (with the proviso that d+e+f is not
0), R1 and R2 each is independently a halogen element or a
perfluoroalkyl or fluorochloroalkyl group having from I
to 10 carbon atoms, and X~ is COOZ, S03Z, P03Zz or P03HZ
(wherein Z is a hydrogen atom, an alkali metal atom, an
alkaline earth metal atom or an amine (e. g., NH4, NH3R1,
NHZR1R2, NHR1R2R3, NR1R2R3R9 ) , and R1, R2, R3 and R9 each is
an alkyl group or an arene group).
In particular, a perfluorocarbonsulfonic acid
polymer represented by the following formula (2) or (3)
or a metal salt thereof is preferred:
- [CF2CF2] a- [CFz-CF (-0-CF2-CF (CF3) ) b-O- (CF2) ~-S03X] ] d-
(2)
wherein a and d are 0<_a<l, 0<_d<1 and a+d=I, b is an
integer of I to 8, c is an integer of 0 to 10, and X is a
hydrogen atom or an alkali metal atom;
- [CF2CF2] e- [CF2-CF (-O- (CFz) f-S03Y) ] g- (3)
wherein a and g are OSe<1, 0<_g<1 and a+g=l, f is an
integer of 0 to 10, and Y is a hydrogen atom or an alkali
metal atom.
The perfluorocarbon polymer compound having an ion
exchange group for use in the present invention can be
produced, for example, by polymerizing a precursor
polymer represented by the following formula (4) and then
subjecting the polymer to alkali hydrolysis, acid
treatment and the like:
- [CFZCX1X2] a- [CF2-CF (-0- (CF2-CF (CFzX3) ) b-O~- (CFR1) d-
( C FRZ ) e- ( C F2 ) f-XS ) ] g- ( 4 )
wherein X1, XZ and X3 each independently represents a
halogen atom or a perfluoroalkyl group having from 1 to 3
carbon atoms, a and g are 05a<1, 0<g<1 and a+g=1, b is an
integer of 0 to 8, c is 0 or 1, d, a and f each is
independently an integer of 0 to 6 (with the proviso that
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d+e+f is not 0), R1 and R2 each is independently a halogen
atom or a perfluoroalkyl or fluorochloroalkyl group
having from 1 to 10 carbon atoms, and XS is COORS, CORq or
S02R4 (wherein R3 is a hydrocarbon-based alkyl group
having from 1 to 3 carbon atoms and R9 is a halogen
element).
The precursor polymer which can be used in the
present invention is produced by copolymerizing a
fluorinated olefin compound and a vinyl fluoride
compound.
Specific examples of the fluorinated olefin compound
include CFZ=CF2, CF2=CFCl and CFZ=CC12.
Specific examples of the vinyl fluoride compound
include CFZ=CFO (CF2) z-SOZF, CF2=CFOCF2CF (CF3) 0 (CFz) z-S02F,
CF2=CF (CFZ) z-S02F, CF2=CF (OCF2CF (CF3) ) z- (CFZ) z-1-S02F,
CFZ=CFO (CF2) z-C02R, CFZ=CFOCF2CF (CF3) 0 (CFZ) z-C02R,
CF2=CF (CFZ) z-C02R and CF2=CF (OCF2CF (CF3) ) z- (CF2) 2-CO2R
(wherein Z represents an integer of 1 to 8, and R
represents a hydrocarbon-based alkyl group having from 1
to 3 carbon atoms).
Examples of the polymerization method for the
precursor polymer include general polymerization methods
such as a solution polymerization method of dissolving a
vinyl fluoride compound in a solvent (e. g.,
fluorocarbon), and reacting the solution with a
fluorinated olefin compound gas, thereby effecting the
polymerization; a bulk polymerization method of
polymerizing these compounds without use of a solvent
(e. g., fluorocarbon); and an emulsion polymerization
method of charging a vinyl fluoride compound together
with a surfactant into water and, after emulsifying it,
reacting it with a fluorinated olefin compound gas,
thereby effecting the polymerization.
Incidentally, the precursor polymer for use in the
present invention may be a copolymer containing a third
component in addition to a vinyl fluoride compound and a
fluorinated olefin compound, for example, containing a
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perfluoroolefin such as hexafluoropropylene and
chlorotrifluoroethylene, or a perfluoroalkylvinyl ether.
The precursor polymer usable in the present
invention preferably has a melt index MI (g/10 min) of
0.001 to 1,000, more preferably from 0.01 to 100, and
most preferably from 0.1 to 10, as measured according to
JIS K-7210 at 270°C under a load of 21.2N with an orifice
inner diameter of 2.09 mm.
The precursor polymer usable in the present
invention is then subjected to an alkali hydrolysis
treatment of dipping it in a basic reactive liquid. The
reactive liquid is preferably an aqueous solution of a
hydroxide of an alkali metal or an alkaline earth metal,
such as potassium hydroxide and sodium hydroxide. The
content of the hydroxide of an alkali metal or an
alkaline earth metal is preferably from 10 to 30 masso.
The reactive liquid preferably contains a swelling
organic compound such as dimethylsulfoxide and methanol.
The content of the swelling organic compound is
preferably from 1 to 30 masso.
After the alkali hydrolysis treatment, the precursor
polymer is, if desired, further treated with an acid such
as hydrochloric acid, whereby a perfluorocarbon polymer
compound having an ion exchange group is produced.
The polyphenylene sulfide resin (B) (hereinafter
sometimes simply referred to as "PPS") for use in the
present invention is not particularly limited, as long as
it is a so-called polyphenylene sulfide resin, but is
preferably a polyphenylene sulfide resin in which the
paraphenylene sulfide skeleton occupies 70 molo or more,
more preferably 90 molo or more.
The PPS is not particularly limited in its
production method, but examples of the production method
usually employed include a method of polymerizing a
halogen-substituted aromatic compound (e.g., p-
dichlorobenzene) in the presence of sulfur and sodium
carbonate, a method of polymerizing p-dichlorobenzene
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with sodium sulfide or sodium hydrogensulfide in a polar
solvent in the presence of sodium hydroxide, a method of
polymerizing p-dichlorobenzene with hydrogen sulfide in a
polar solvent in the presence of sodium hydroxide or
sodium aminoalkanoate, and a self-condensation of p-
chlorothiophenol. Among these, preferred is a method of
reacting sodium sulfide with p-dichlorobenzene in an
amide-based solvent such as N-methylpyrrolidone and
dimethylacetamide, or a sulfone-based solvent such as
sulfolane. Specific examples thereof include the methods
described in U.S. Patent No. 2,513,188, Japanese Examined
Patent Publication (Kokoku) Nos. 44-27671, 45-3368 and
52-12240, Japanese Unexamined Patent Publication (Kokai)
No. 61-225217, U.S. Patent No. 3,274,165, British Patent
No. 1,160,660, Kokoku No. 46-27255, Belgian Patent No.
29437 and Kokai No. 5-222196, and the methods described
in prior arts cited in these patent publications.
The polyphenylene sulfide resin (B) for use in the
present invention is preferably a polyphenylene sulfide
resin in which the amount of oligomer extracted with
methylene chloride is from 0.001 to 0.9 wto and the -SX
group (wherein S is a sulfur atom and X is an alkali
metal or a hydrogen atom) concentration is from 10 to
10,000 ~mol/g.
The amount of oligomer extracted with methylene
chloride is preferably from 0.001 to 0.8 wto, more
preferably from 0.001 to 0.7 wto. When the amount of
oligomer extracted with methylene chloride is in such a
range, this means that the amount of oligomer (from about
10- to 30-mer) in PPS is small. If the amount of
oligomer extracted exceeds the above-described range,
bleed-out is readily generated at the film formation and
this is not preferred.
The amount of oligomer extracted with methylene
chloride can be measured by the following method. That
is, 5 g of PPS powder is added to 80 ml of methylene
chloride, subjected to Soxhlet extraction for 4 hours and
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then cooled to room temperature, and the methylene
chloride solution after extraction is transferred to a
weighing bottle. The vessel used for the extraction is
washed in three parts with 60 ml in total of methylene
chloride, and the washing solution is recovered in the
weighing bottle. Thereafter, methylene chloride in the
weighing bottle is evaporated and thereby removed under
heating at about 80°C, and the residue is weighed. From
the amount of residue, the ratio of the amount of
oligomer present in PPS can be determined.
The content of the -SX group is more preferably from
to 10,000 ~mol/g, most preferably from 20 to 10,000
~mol/g. When the -SX group concentration is in such a
range, this means that the polyphenylene sulfide resin
15 has a large number of reaction active sites. Use of a
polyphenylene sulfide resin having an -SX group
concentration satisfying the above-described range is
considered to have the effect of enhancing the
miscibility of the polymer compound having an ion
exchange group (A) with the polyphenylene sulfide resin
(B) in the polymer electrolyte composition of the present
invention and in turn, enhancing the dispersibility of
the polyphenylene sulfide resin (B) in the polymer
compound having an ion exchange group (A).
The content of the -SX group can be determined by
the following method. That is, PPS powder is previously
dried at 120°C for 4 hours, and 20 g of the dried PPS
powder is added to 150 g of N-methyl-2-pyrrolidone and
mixed with vigorous stirring at room temperature for 30
minutes to eliminate powder aggregates and produce a
slurry state. The obtained slurry is filtered and
repeatedly washed 7 times by using 1 liter of warm water
at about 80°C every each washing. The obtained filter
cake is again formed into a slurry in 200 g of pure
water, and the slurry is adjusted to a pH of 4.5 by
adding 1N hydrochloric acid, then stirred at 25°C for 30
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minutes, filtered and repeatedly washed 6 times by using
1 liter of warm water at about 80°C. The obtained filter
cake is again formed into a slurry in 200 g of pure water
and by performing titration with 1N sodium hydroxide, the
amount of the -SX group present in PPS is determined from
the amount of sodium hydroxide consumed.
Specific examples of the production method for PPS
in which the amount of oligomer extracted with methylene
oxide is from 0.001 to 0.9 wto and the -SX group
concentration is from 10 to 10,000 ~mol/g include the
production method described in Examples 1 and 2
(paragraphs 0041 to 0044) of Japanese Unexamined Patent
Publication (Kokai) No. 8-253587 and the production
method described in Synthesis Examples 1 and 2
(paragraphs 0046 to 0048) of Kokai No. 11-106656.
The PPS for use in the present invention preferably
has a melt viscosity (a value measured by using a flow
tester and keeping the PPS at 300°C under a load of 196N
with L/D (L: orifice length, D: orifice inner diameter)
10/1 for 6 minutes) at 320°C of 1 to 10,000 poise, more
preferably from 100 to 10,000 poise.
In the present invention, a polyphenylene sulfide
resin having introduced thereinto an acidic functional
group or a reactive functional group can also be suitably
used as the polyphenylene sulfide resin (B).
Introduction of such a functional group is considered to
give an effect of enhancing the miscibility of the
polymer compound having an ion exchange group (A) with
the polyphenylene sulfide resin (B) in the polymer
electrolyte composition of the present invention and in
turn, enhancing the dispersibility of the polyphenylene
sulfide resin (B) in the polymer compound having an ion
exchange group (A). In particular, when an acidic
functional group is introduced, this means that the
number of functional groups participating in the proton
conductivity in the proton exchange membrane comprising
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the polymer electrolyte of the present invention is
increased, and high proton conductivity can be
advantageously expressed. Preferred examples of the
acidic functional group introduced include a sulfonic
acid group, a phosphoric acid group, a sulfonamide group,
a carboxylic acid group, a malefic acid group, a malefic
anhydride group, a fumaric acid group, an itaconic acid
group, an acrylic acid group and a methacrylic acid
group. Among these, more preferred are a sulfonic acid
group and a phosphoric acid group, which are a strong
acid group, and most preferred is a sulfonic acid group.
Preferred examples of the reactive functional group
introduced include an epoxy group, an oxazonyl group, an
amino group, an isocyanate group and a carbodiimide
group. Among these, an epoxy group is more preferred.
Also, two or more of these various functional groups may
be introduced.
The method for introducing the acidic functional
group or reactive functional group is not particularly
limited and such a functional group can be introduced by
a general method. For example, a sulfonic acid group can
be introduced by using a sulfonating agent such as
sulfuric anhydride and fuming sulfuric acid, under known
conditions such as conditions described in K. Hu, T. Xu,
W. Yang and Y. Fu, Journal of Applied Polymer Science,
Vol. 91, and E. Montoneri, Journal of Polymer Science:
Part A: Polymer Chemistry, Vol. 27, 3043-3051 (1989).
Furthermore, a polyphenylene sulfide resin where the
acidic functional group introduced is replaced with a
metal salt or an amine salt is also preferably used. The
metal salt is preferably an alkali metal salt such as
sodium salt and potassium salt, or an alkaline earth
metal salt such as calcium salt.
The polyphenylene ether resin (hereinafter sometimes
simply referred to as "PPE") (C) for use in the present
invention is not particularly limited as long as it is a
so-called polyphenylene ether resin, but this resin is
CA 02563788 2006-10-20
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preferably a phenol homopolymer or copolymer containing a
structural unit represented by the following formula (5)
in a proportion of 70 molo or more, preferably 90 molo or
more:
R1 R2
(5)
wherein Rl, R2, R3 and R4 may be the same or different
and each is a substituent selected from the group
consisting of hydrogen, a halogen, a linear or branched
lower alkyl group having from 1 to 7 carbon atoms, a
phenyl group, a haloalkyl group, an aminoalkyl group, an
oxy-hydrocarbon group and an oxy-halohydrocarbon group
with at least two carbon atoms separating a halogen atom
from an oxygen atom.
Specific examples of the PPE include poly(2,6-
dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-
phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene
ether) and poly(2,6-dichloro-1,4-phenylene ether), and
further include a copolymer of 2,6-dimethylphenol with
other monovalent phenols (e.g., 2,3,6-trimethylphenol, 2-
methyl-6-butylphenol), and a copolymer of 2,6-
dimethylphenol with divalent phenols (e. g., 3,3',5,5'-
tetramethyl bisphenol A). Among these, preferred are
poly(2,6-dimethyl-1,4-phenylene ether), a copolymer of
2,6-dimethylphenol and 2,3,6-trimethylphenol, and a
copolymer of 2,6-dimethylphenol and 3,3',5,5'-tetramethyl
bisphenol A.
The polyphenylene ether resin (C) for use in the
present invention preferably has a phenolic hydroxyl
group at the molecular chain end, and the position
thereof may be either one end or both ends.
The reduced viscosity (measured with 0.5 g/dl of
chloroform solution at 30°C) of the polyphenylene ether
CA 02563788 2006-10-20
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resin (C) for use in the present invention is preferably
from 0.05 to 2.0 dl/g, more preferably from 0.10 to 0.8
dl/g.
The polyphenylene ether resin (C) for use in the
present invention is not particularly limited in its
production method and can be easily produced, for
example, by a method described in U.S. Patent No.
3,306,874 where, for example, 2,6-dimethylphenol is
oxidation-polymerized by using a complex of cuprous salt
and amine as a catalyst. In addition, the polyphenylene
ether resin can be easily prepared by the methods
described in U.S. Patent Nos. 3,306,875, 3,257,357 and
3,257,358, Japanese Examined Patent Publication (Kokoku)
No. 52-17880, and Japanese Unexamined Patent Publication
(Kokai) Nos. 50-51197 and 63-152628.
In the present invention, a polyphenylene ether
resin having introduced thereinto an acidic functional
group or a reactive functional group can also be suitably
used as the polyphenylene ether resin (C). Introduction
of such a functional group is considered to give an
effect of enhancing the miscibility of the polymer
compound having an ion exchange group (A) with the
polyphenylene ether resin (C) in the polymer electrolyte
composition of the present invention and in turn,
enhancing the dispersibility of the polyphenylene ether
resin (C) in the polymer compound having an ion exchange
group (A). In particular, when an acidic functional
group is introduced, this means that the number of
functional groups participating in the proton
conductivity in the proton exchange membrane comprising
the polymer electrolyte of the present invention is
increased, and high proton conductivity can be
advantageously expressed. Preferred examples of the
acidic functional group introduced include a sulfonic
acid group, a phosphoric acid group, a sulfonimide group,
a carboxylic acid group, a malefic acid group, a malefic
anhydride group, a fumaric acid group, an itaconic acid
CA 02563788 2006-10-20
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group, an acrylic acid group and a methacrylic acid
group. Among these, more preferred are a sulfonic acid
group and a phosphoric acid group, which are a strong
acid group, and most preferred is a sulfonic acid group.
Preferred examples of the reactive functional group
introduced include an epoxy group, an oxazonyl group, an
amino group, an isocyanate group and a carbodiimide
group. Among these, an epoxy group is more preferred.
Also, two or more of these various functional groups may
be introduced.
The method for introducing the acidic functional
group or reactive functional group is not particularly
limited and such a functional group can be introduced by
a general method. For example, a sulfonic acid group can
be introduced by using a sulfonating agent such as
sulfuric anhydride and fuming sulfuric acid, under known
conditions such as conditions described C. Wang, Y. Huang
and G. Cong, Polymer Journal, Vol. 27, No. 2, 173-178
(1995), and J. Schauer, W. Albrecht and T. Weigel,
Journal of Applied Polymer Science, Vol. 73, 161-167
(1999) .
Furthermore, a polyphenylene ether resin where the
acidic functional group introduced is replaced with a
metal salt or an amine salt is also preferably used. The
metal salt is preferably an alkali metal salt such as
sodium salt and potassium salt, or an alkaline earth
metal salt such as calcium salt.
The polysulfone resin (D) for use in the present
invention is not particularly limited as long as it is a
so-called polysulfone resin, but this resin is preferably
a polysulfone resin containing a structure represented by
the following formula (6) in a proportion of 80 molo or
more, preferably 90 mol% or more.
CH3 O
O-
~ II
~H3 (6)
CA 02563788 2006-10-20
- 20 -
The polysulfone resin (D) for use in the present
invention is not particularly limited in its production
method and can be easily produced, for example, by
reacting a sodium salt of bisphenol A with 4,4'-
dichlorodiphenylsulfone.
In the present invention, a polysulfone resin having
introduced thereinto an acidic functional group or a
reactive functional group can also be suitably used as
the polysulfone resin (D). Introduction of such a
functional group is considered to give an effect of
enhancing the miscibility of the polymer compound having
an ion exchange group (A) with the polysulfone resin (D)
in the polymer electrolyte composition of the present
invention and in turn, enhancing the dispersibility of
the polysulfone resin (D) in the polymer compound having
an ion exchange group (A). In particular, when an acidic
functional group is introduced, this means that the
number of functional groups participating in the proton
conductivity in the proton exchange membrane comprising
the polymer electrolyte of the present invention is
increased, and high proton conductivity can be
advantageously expressed. Preferred examples of the
acidic functional group introduced include a sulfonic
acid group, a phosphoric acid group, a sulfonamide group,
a carboxylic acid group, a malefic acid group, a malefic
anhydride group, a fumaric acid group, an itaconic acid
group, an acrylic acid group and a methacrylic acid
group. Among these, more preferred are a sulfonic acid
group and a phosphoric acid group, which are a strong
acid group, and most preferred is a sulfonic acid group.
Preferred examples of the reactive functional group
introduced include an epoxy group, an oxazonyl group, an
amino group, an isocyanate group and a carbodiimide
group. Among these, an epoxy group is more preferred.
Also, two or more of these various functional groups may
be introduced.
The method for introducing the acidic functional
CA 02563788 2006-10-20
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group or reactive functional group is not particularly
limited and such a functional group can be introduced by
a general method. For example, a sulfonic acid group can
be introduced by using a sulfonating agent such as
sulfuric anhydride and fuming sulfuric acid, under known
conditions.
Furthermore, a polysulfone resin where the acidic
functional group introduced is replaced with a metal salt
or an amine salt is also preferably used. The metal salt
is preferably an alkali metal salt such as sodium salt
and potassium salt, or an alkaline earth metal salt such
as calcium salt.
The polymer electrolyte composition of the present
invention is a composition comprising these (A) polymer
compound having an ion exchange group, (B) polyphenylene
sulfide resin and at least one resin selected from (C)
polyphenylene ether resin and (D) polysulfone resin.
Such a polymer electrolyte composition of the present
invention and a proton exchange membrane comprising this
composition are remarkably enhanced in the durability as
compared with the case of using solely the polymer
compound having an ion exchange group (A) or as compared
with the case of introducing solely the polyphenylene
sulfide resin (B), the polyphenylene ether resin (C) or
the polysulfone resin (D) into the polymer compound
having an ion exchange group (A). Furthermore,
surprisingly, the polymer electrolyte composition of the
present invention is remarkably enhanced in durability
even when compared with the case of incorporating many
resins including the resins used in the present invention
in various combinations, except for the combination of
the present invention, into the polymer compound having
an ion exchange group (A).
The compositional ratio of the polymer compound
having an ion exchange group (A), the polyphenylene
sulfide resin (B), the polyphenylene ether resin (C) and
the polysulfone resin (D) in the polymer electrolyte
CA 02563788 2006-10-20
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composition of the present invention is described below.
In the polymer electrolyte composition of the
present invention, the mass ratio of the polyphenylene
sulfide resin (B) to the polyphenylene ether resin (C)
and/or the polysulfone resin (D) is preferably
B/(C+D)=1/99 to 99/1, more preferably B/(C+D)=20/80 to
95/5, and most preferably B/(C+D)=30/70 to 90/10.
The mass ratio ((B+C+D)/A) of the polyphenylene
sulfide resin (B), polyphenylene ether resin (C) and
polysulfone resin (D) to the polymer compound having an
ion exchange group (A) is preferably from 99/1 to
0.01/99.99. In view of the balance between proton
conductivity and durability, (B+C+D)/A is more preferably
from 90/10 to 0.05/99.95, still more preferably from
70/30 to 0.1/99.9, yet still more preferably from 50/50
to 1/99, and most preferably from 30/70 to 5/95.
In the case where the polymer electrolyte
composition of the present invention contains the
polyphenylene ether resin (C), the composition preferably
contains an epoxy group-containing compound (F). When
the polymer electrolyte composition comprising at least
the polymer compound having an ion exchange group (A),
the polyphenylene sulfide resin (B) and the polyphenylene
ether resin (C) contains an epoxy group-containing
compound (F), the particle dispersibility in the polymer
electrolyte composition is enhanced and in turn, the
polymer electrolyte composition and a proton exchange
membrane comprising this composition are more enhanced in
the durability.
The epoxy group-containing compound (F) for use in
the present invention is not particularly limited as long
as it is a compound having an epoxy group, and examples
thereof include a low molecular compound containing an
epoxy group, (G) a homopolymer or copolymer of an
unsaturated monomer having an epoxy group, and (H) an
epoxy resin. Among these, (G) a homopolymer or copolymer
of an unsaturated monomer having an epoxy group, and (H)
CA 02563788 2006-10-20
- 23 -
an epoxy resin are preferred, because a polymer compound
is easier to handle at high temperatures.
The low molecular compound having an epoxy group is
preferably a solid or a liquid at 200°C, and specific
examples thereof include 1,2-epoxy-3-phenoxypropane, N-
(2,3-epoxypropyl)phthalimide, 3,4-
epoxytetrahydrothiophene-1,1-dioxide, glycidyl 4-
nonylphenyl ether, glycidyl tosylate and glycidyl trityl
ether.
The content of the epoxy group-containing compound
(F) is, based on the total mass of the polyphenylene
sulfide resin (B) and the polyphenylene ether resin (C),
preferably F/(B+C)=1/100 to 200/100, more preferably
F/(B+C)=2/100 to 100/100, still more preferably
F/(B+C)=3/100 to 50/100.
In the homopolymer or copolymer of an unsaturated
monomer having an epoxy group (G) for use in the present
invention, the unsaturated monomer having an epoxy group
constituting the homopolymer or copolymer is not
particularly limited, as long as it is an unsaturated
monomer having an epoxy group, and examples thereof
include glycidyl methacrylate, glycidyl acrylate, vinyl
glycidyl ether, glycidyl ether of hydroxyalkyl
(meth)acrylate, glycidyl ether of polyalkylene glycol
(meth)acrylate, and glycidyl itaconate. Among these,
glycidyl methacrylate is preferred.
In the case of the copolymer of an unsaturated
monomer having an epoxy group, preferred examples of the
other unsaturated monomer copolymerized with the
unsaturated monomer having an epoxy group include vinyl
aromatic compounds (e. g., styrene), vinyl cyanide
monomers (e.g., acrylonitrile), vinyl acetate and
(meth)acrylic acid esters. Examples of the copolymer
obtained by the copolymerization with such a
copolymerizable unsaturated monomer include a styrene-
glycidyl methacrylate copolymer, a styrene-glycidyl
methacrylate-methyl methacrylate copolymer, and a
CA 02563788 2006-10-20
- 24 -
styrene-glycidyl methacrylate-acrylonitrile copolymer.
Among these copolymers, a copolymer containing an
unsaturated monomer having an epoxy group and a styrene
monomer is preferred, because this copolymer has
excellent affinity particularly for the polyphenylene
ether resin (C) and the dispersibility of particularly
the polyphenylene ether resin (C) is enhanced. From the
standpoint of enhancing the dispersibility, the copolymer
preferably contains a styrene monomer in a proportion of
at least 65 masso. Also, the copolymer preferably
contains the unsaturated monomer having an epoxy group,
in a proportion of 0.3 to 20 masso, more preferably from
1 to 15 masso, still more preferably from 3 to 10 masso.
Examples of the epoxy resin (H) for use in the
present invention include cresol novolak-type epoxy
resin, bisphenol A-type epoxy resin, bisphenol F-type
epoxy resin, bisphenol S-type epoxy resin, hydantoin-type
epoxy resin, biphenyl-type epoxy resin, alicyclic epoxy
resin, triphenylmethane-type epoxy resin and phenol
novolak-type epoxy resin. One resin selected from these
may be used or a mixture of two or more thereof may be
used. Among these resins, a cresol novolak-type epoxy
resin and a bisphenol A-type epoxy resin are preferred,
and a cresol novolak-type epoxy resin is more preferred.
In the present invention, the polyphenylene ether
resin (C) and the epoxy resin (H) may be added after
previously mixing and reacting these resins. That is, an
epoxy-modified polyphenylene ether resin (E) obtained by
reacting a polyphenylene ether resin and an epoxy resin
can be used as the polyphenylene ether resin (C). Of
course, after mixing the polyphenylene ether resin (C)
and the epoxy resin (H) together with the components (A)
and (B) to prepare the composition of the present
invention, the polyphenylene ether resin (C) and the
epoxy resin (H) may be reacted under the conditions
described later.
When the epoxy-modified polyphenylene ether resin
CA 02563788 2006-10-20
- 25 -
(E) is used as the polyphenylene ether resin (C), the
dispersibility of the obtained polymer electrolyte
composition is enhanced and in turn, the polymer
electrolyte composition and a proton exchange membrane
comprising this composition are more enhanced in the
durability.
As for the production method of the epoxy-modified
polyphenylene ether resin (E), the reaction temperature
is preferably from 100 to 250°C, more preferably from 120
to 195°C, still more preferably from 140 to 190°C, and the
reaction time is preferably less than 3 hours, more
preferably 2 hours or less, still more preferably 40
minutes or less.
The reactor used for the production of the epoxy-
modified polyphenylene ether resin (E) is preferably a
reactor where a polyphenylene ether resin and an epoxy
resin can be uniformly mixed, stirred or kneaded. In the
case where the viscosity is high, a kneading machine such
as twin screw extruder and kneader may be used. The
production method may employ any process form of a
continuous reaction process, a batch reaction process and
a semi-batch reaction process.
In the production method of the epoxy-modified
polyphenylene ether resin (E), a basic compound may be
added to the reaction system from the standpoint of
increasing the reaction rate, preventing the side
reaction or controlling the structure of product
composition E. Specific examples of the basic compound
include lithium, sodium, potassium, sodium methylate,
sodium ethylate, tertiary amine (e. g., triethylamine,
tributylamine), imidazole, sodium phenoxide, lithium
hydroxide, sodium hydroxide, potassium hydroxide,
potassium carbonate and sodium carbonate. Among these,
preferred are sodium methylate, triethylamine,
tributylamine and sodium hydroxide. Other than these
basic compounds, a quaternary ammonium salt can also be
used as the catalyst.
CA 02563788 2006-10-20
- 26 -
In the present invention, the components (A) to (H)
each may comprise two or more compounds. For example, a
mixture of poly(2,6-dimethyl-1,4-phenylene ether) and
poly(2-methyl-6-ethyl-1,4-phenylene ether) or a mixture
of poly(2,6-dimethyl-1,4-phenylene ether) and poly(2,6-
dimethyl-1,4-phenylene ether) having introduced thereinto
a sulfonic acid group may be used as the polyphenylene
ether resin (C), and a mixture of polyphenylene sulfide
and sulfonated polyphenylene sulfide may be used as the
polyphenylene sulfide resin (B).
In the polymer electrolyte composition of the
present invention, various additives such as antioxidant,
age resistor, heavy metal inactivating agent and flame
retardant may be added, if desired. The weight ratio
(electrolyte composition/additive) of the polymer
electrolyte composition of the present invention to the
additive is preferably from 80/20 to 99.999/0.001, more
preferably from 90/10 to 99.99/0.01, still more
preferably from 95/5 to 99.9/0.1.
The method for manufacturing the polymer electrolyte
composition of the present invention is described below.
The polymer electrolyte composition of the present
invention is obtained by mixing the components selected
from the components (A) to (H), but the method therefor
is not particularly limited and a general mixing method
for polymer compositions can be suitably applied.
For example, a method of heat-melting the polymer
compound having an ion exchange group (A) or a precursor
polymer thereof and the components selected from the
components (B) to (H), and kneading the melt by a
kneading-extruder, Labo Plastomill, a kneading roll, a
Banbury mixer or the like may be used. Alternatively,
after the components selected from the components (B) to
(H) are heat-melted and kneaded by a kneading-extruder,
Labo Plastomill, a kneading roll, a Banbury mixer or the
like to obtain a mixture, the obtained mixture may be
similarly kneaded with the polymer compound having an ion
' ~ CA 02563788 2006-10-20
- 27 -
exchange group (A) or a precursor polymer thereof to
obtain a final polymer electrolyte composition. The
combination and order of kneading operations can be
freely selected. Incidentally, in the case of using a
precursor polymer in place of the polymer compound having
an ion exchange group (A), the polymer electrolyte
composition of the present invention can be obtained by
performing an alkali hydrolysis treatment and an acid
treatment after kneading to convert the composition into
a form having an ion exchange group.
The kneading at this time can be achieved by using a
conventionally known technique such as Brabender,
kneader, Banbury mixer and extruder. In particular, when
an extruder is used, fine dispersion of other components
in the polymer compound having an ion exchange group (A)
can be easily effected in the obtained polymer
electrolyte composition and this is preferred.
In a most preferred embodiment of the method for
easily obtaining the polymer electrolyte composition of
the present invention in industry, the extruder for melt-
kneading the above-described components is a twin- or
more mufti-screw extruder allowing for incorporation of
kneading blocks into arbitrary positions of a screw, all
kneading block portions of the screw used are
incorporated substantially at (L/D)>_1.5, more preferably
(L/D)>_5 (wherein L indicates the total length of the
kneading blocks and D indicates the maximum outer
diameter of the kneading blocks), and (~~D~N/h)>_50 is
satisfied [where ~=3.14, D: outer diameter of screw
corresponding to metering zone, N: screw rotation number
(revolutions/sec), and h: depth of the channel of the
metering zone]. The extruder has a first raw material
supply port on the upstream side with respect to the flow
direction of the raw material, and a second raw material
supply port downstream the first raw material supply
port, and if desired, one or more raw material supply
CA 02563788 2006-10-20
- 28 -
port may be further provided downstream the second raw
material supply port. Furthermore, if desired, a vacuum
vent port may be provided between these raw material
supply ports.
In addition, a method of mixing a solution of the
polymer compound having an ion exchange group (A) or a
precursor polymer thereof with respective solutions of
the components (B) to (H) to prepare a solution and then
removing the solvent may be used. Also in this case,
when a precursor polymer solution is used in place of a
solution of the polymer compound having an ion exchange
group (A), the polymer electrolyte composition of the
present invention can be obtained by performing an alkali
hydrolysis treatment and an acid treatment after kneading
to convert the composition into a form having an ion
exchange group.
The polymer electrolyte composition of the present
invention can be obtained by such a method, but in the
present invention, when the composition has at least a
structure that other components are finely dispersed in
the polymer compound having an ion exchange group (A),
the effect of the present invention, such as prolongation
of life, can be obtained. More specifically, the
composition suitably has a structure such that the
particles comprising other components are dispersed in
the polymer compound having an ion exchange group (A), to
have an equivalent-circle average particle diameter of
0.0001 to 1 Vim, preferably from 0.0001 to 0.8 Vim, more
preferably from 0.0001 to 0.5 Vim, still more preferably
from 0.0001 to 0.3 ~,m. This particle diameter range need
not be satisfied in all regions of the composition and it
is sufficient if from 50 to 1000 of the entire region of
the composition satisfies the above-described range.
The composition may also have a structure that the
component (A) is intruding inside of dispersed particles
comprising other components. However, in this case also,
CA 02563788 2006-10-20
- 29 -
it is preferred in view of prolongation of life that the
particle diameter of dispersed particles is, in terms of
the equivalent-circle average particle diameter, from
0.0001 to 1 ~tm, preferably from 0.0001 to 0.8 Vim, more
preferably from 0.0001 to 0.5 Vim, still more preferably
from 0.0001 to 0.3 ~tm.
The proton exchange membrane which is described
later also preferably has at least the above-described
fine dispersion structure.
Such a fine dispersion structure can be controlled,
for example, by the composition of the material or
various conditions at the processing. More specifically,
as for the composition of the material, the fine
dispersion structure can be controlled by the combination
or quantitative ratio of respective components, the use
of a compatibilizing agent, the kind of solvent when a
solvent is used, and the like. Also, various conditions
at the processing include the temperature condition and
the stirring and kneading condition. In particular, at
the extrusion processing, the design and rotation number
of screw have a large effect.
The equivalent-circle average particle diameter as
used in the present invention is defined as follows. A
slice is produced from the polymer electrolyte
composition or proton exchange membrane of the present
invention, dyed with a dying agent such as ruthenium
tetroxide in a usual manner and observed by a
transmission-type electron microscope, the average
particle diameter in the dyed phase is determined, and
this value is defined as the particle diameter. At this
time, an arbitrary visual field of 20x20 ~m of the slice
is printed to a photograph directly or from a negative
and read into an image analyzer, and the number average
of equivalent-circle diameters (diameter of a circle
having the same area) calculated of individual particles
is defined as the average particle diameter. However,
CA 02563788 2006-10-20
- 30 -
when the dyed boundary is indistinct at the time of
inputting the data into the image analyzer from the
photograph, the photograph is traced and by using the
figure traced, the data are input into the image
analyzer.
The method for manufacturing a proton exchange
membrane comprising the polymer electrolyte composition
of the present invention is described below. The polymer
electrolyte composition of the present invention can be
film-formed and used as a proton exchange membrane. The
film-forming means is not particularly limited and a
general film-forming method for polymer compositions can
be suitably applied. Examples thereof include known
film-forming methods such as calender molding, press
molding, T-die molding and inflation molding. Among
these, T-die molding and inflation molding are preferred
as the method for easily obtaining a proton exchange
membrane from the polymer electrolyte composition of the
present invention in industry. In particular, inflation
molding is preferred also in view of obtaining a film
with small anisotropy.
Alternatively, after a precursor of the polymer
electrolyte composition of the present invention, for
example, a polymer composition comprising a precursor
polymer of the polymer compound having an ion exchange
group (A) and the components selected from the components
(B) to (H), is film-formed by the above-described film-
forming method, the film may be converted into a form
having an ion exchange group by performing an appropriate
after-treatment such as alkali hydrolysis treatment and
acid treatment to obtain a proton exchange membrane
comprising the polymer electrolyte composition of the
present invention.
Furthermore, a proton exchange membrane can also be
obtained by mixing respective solutions of the components
(A) to (H) to prepare a solution, casting the solution
and then removing the solvent. As for the casting
CA 02563788 2006-10-20
- 31 -
method, a method of pouring the solution in a Petri dish
and producing a film, and known coating methods such as
gravure roll coater, natural roll coater, reverse roll
coater, knife coater and dip coater can be used.
Examples of the substrate which can be used for the
casting method include substrates such as general polymer
film, metal foil, alumina and silicon, a porous film
obtained by stretching a PTFE film described in Japanese
Unexamined Patent Publication (Kokai) No. 8-162132, and a
fibrillated fiber described in Kokai No. 53-149881 and
Japanese Examined Patent Publication (Kokoku) No. 63-
61337. For the removal of the solvent, a method such as
heat treatment at a temperature from room temperature to
200°C or treatment under reduced pressure may be used. In
the case of performing a heat treatment, it is also
possible to stepwise elevate the temperature and thereby
remove the solvent.
In addition, a proton exchange membrane comprising
the polymer electrolyte composition of the present
invention can also be obtained by using a solution of a
precursor polymer in place of a solution of the polymer
compound having an ion exchange group (A), mixing the
solution with respective solutions of the components (B)
to (H) to prepare a solution, casting this solution,
removing the solvent, and performing an appropriate
after-treatment such as alkali hydrolysis treatment and
acid treatment to convert the film into a form having an
ion exchange group.
In the production of the proton exchange membrane of
the present invention, when transverse uniaxial
stretching, simultaneous biaxial stretching or successive
biaxial stretching is performed in combination with the
above-described production method, stretching orientation
can be imparted. Such a stretching treatment is
preferred because the mechanical properties of the proton
exchange membrane of the present invention can be
enhanced. This stretching treatment may be performed in
CA 02563788 2006-10-20
- 32 -
the state of a proton exchange membrane or in the state
in which the proton exchange group is replaced with a
metal salt such as sodium salt, potassium salt and
calcium salt, an ammonium salt or the like. Also, in the
case of film-forming a polymer composition comprising a
precursor polymer of the polymer compound having an ion
exchange group (A) and the components selected from the
components (B) to (H), the stretching treatment may be
performed in the state immediately after the film
formation or may be performed after converting the film
into a form having an ion exchange group by performing an
appropriate after-treatment such as alkali hydrolysis
treatment and acid treatment.
The stretching treatment is preferably performed at
a draw ratio of 1.1 to 6.0 times in the transverse
direction (TD) and at a draw ratio of 1.0 to 6.0 times in
the machine direction (MD), more preferably at a draw
ratio of 1.1 to 3.0 times in the transverse direction and
at a ratio of 1.0 to 3.0 times in the machine direction,
still more preferably at a draw ratio of 1.1 to 2.0 times
in the transverse direction and at a draw ratio of 1.0 to
2.0 times in the machine direction. The area draw ratio
is preferably from 1.1 to 36 times.
The proton exchange membrane of the present
invention may have a structure where at least two proton
exchange membranes differing in the compositional ratio
are stacked. In the proton exchange membrane comprising
the polymer electrolyte composition of the present
invention, as the content of the resin except for the
polymer compound having an ion exchange group (A) is
higher, the membrane is more excellent in mechanical
strength and the dry and wet dimensional stability, and
as the content of the polymer compound having an ion
exchange group (A) is higher, the membrane is more
excellent in electrical properties such as proton
conductivity. When two or more proton exchange membranes
differing in compositional ratio are designed by making
CA 02563788 2006-10-20
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use of these characteristic properties and these
membranes in combination are stacked, a proton exchange
membrane excellent in all of mechanical strength, dry and
wet dimensional stability and electrical property can be
more easily realized than in the case of a single layer
membrane.
The number of layers stacked is not limited, but as
the number of layers becomes larger, the production cost
is higher. Therefore, the number of layers stacked is
preferably on the order of 2 to 10, more preferably from
2 to 7, still more preferably from 3 to 5. In each
layer, the compositional ratio of the polymer compound
having an ion exchange group (A), the polyphenylene
sulfide resin (B), the polyphenylene ether resin (C), the
polysulfone resin (D) and the epoxy group-containing
compound (F) can be arbitrarily changed within the above-
described range. Also, the thickness of each layer can
be arbitrarily changed, taking account of the
characteristic properties.
For example, in the case of a multilayer structure
comprising three or more layers, when the content of the
polymer compound having an ion exchange group (A) in the
inner layer is made to be smaller than that of at least
one surface layer so as to prevent the dry and wet
dimensional change of the inner layer, the thickness of
the inner layer is preferably from 5 to 900, more
preferably from 7 to 800, still more preferably from 10
to 500, of the entire thickness. Also, when the content
of the polymer compound having an ion exchange group (A)
in the surface layers is made smaller than that of the
inner layer so as to prevent the dry and wet dimensional
change of the surface layers, the total thickness of the
surface layers is preferably from 5 to 500, more
preferably from 7 to 450, still more preferably from 10
to 400, of the entire thickness.
In the production of the proton exchange membrane of
the present invention, reinforcement, for example, by the
CA 02563788 2006-10-20
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addition of a reinforcing material comprising an
inorganic or organic material or an organic-inorganic
hybrid material or by the crosslinking may be applied in
combination with the above-described production method.
The reinforcing material may be a staple fiber substance,
a particulate substance, a flaked substance or a
continuous support such as porous film, mesh and non-
woven fabric. By virtue of the reinforcement by the
addition of a reinforcing material, the proton exchange
membrane of the present invention can be easily enhanced
in the mechanical strength and the dry and wet
dimensional stability. In particular, when a staple
fiber substance or a continuous support is used as the
reinforcing material, a high reinforcement effect is
obtained.
The reinforcing material may be added and mixed
simultaneously with the melt-kneading or may be laminated
on a film after the film formation.
The inorganic material used as the reinforcing
material is not particularly limited as long as it has a
reinforcement effect, and examples thereof include glass
fiber, carbon fiber, cellulose fiber, kaolin clay,
kaolinite, halloysite, pyrophyllite, talc,
montmorillonite, sericite, mica, amesite, bentonite,
asbestos, zeolite, calcium carbonate, calcium silicate,
diatomaceous earth, silica sand, ferrous ferrite,
aluminum hydroxide, aluminum oxide, magnesium oxide,
titanium oxide, zirconium oxide, graphite, fullerene,
carbon nanotube and carbon nanohorn. The organic
material as the reinforcing material is also not
particularly limited, as long as it has a reinforcement
effect, and examples thereof include polyphenylene
sulfide, polyphenylene ether, polysulfone,
polyethersulfone, polyether ether sulfone, polyether
ketone, polyether ether ketone, polythioethersulfone,
polythioether ether sulfone, polythioether ketone,
polythioether ether ketone, polybenzimidazole,
CA 02563788 2006-10-20
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polybenzoxazole, polyoxadiazole, polybenzoxadinone,
polyxylylene, polyphenylene, polythiophene, polypyrrole,
polyaniline, polyacene, polycyanogen, polynaphthylidine,
polyphenylene sulfide sulfone, polyphenylenesulfone,
polyimide, polyetherimide, polyesterimide,
polyamidoimide, polyamide, aromatic polyamide,
polystyrene, acrylonitrile-styrene resin, polystyrene-
hydrogenated polybutadiene-polystyrene block copolymer,
acrylonitrile-butadiene-styrene resin, polyester,
polyarylate, liquid crystal polyester, polycarbonate,
polytetrafluoroethylene, polyvinylidene fluoride,
polyvinyl chloride, polyvinylidene chloride, methacrylic
resin, epoxy resin, phenol resin, melamine resin,
urethane resin, cellulose, polyketone, polyacetal,
polypropylene and polyethylene. An organic-inorganic
hybrid material can also be used as the reinforcing
material and examples thereof include organic silicon
polymer compounds having a silsesquioxane structure or a
siloxane structure, such as POSS (polyhedral oligomeric
silsesquioxanes) and silicone rubber.
Also, by heat-treating the polymer electrolyte
composition of the present invention, for example, at
160°C or more in air or in an oxygen atmosphere, the
mechanical property can be enhanced.
The equivalent weight EW of the proton exchange
membrane (the gram number of dry mass of the proton
exchange membrane per equivalent of the proton exchange
group) produced in the present invention is preferably
from 250 to 2,000, more preferably from 400 to 1,500, and
most preferably from 500 to 1,200. By using a lower EW,
that is, using a proton conductive polymer having a large
proton exchange capacity, excellent proton conductivity
is exhibited even under high-temperature low-
humidification conditions and when used for a fuel cell,
high output can be obtained at the operation.
The thickness of the proton exchange membrane
produced in the present invention is preferably from 1 to
CA 02563788 2006-10-20
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500 Vim, more preferably from 2 to 100 Vim, and most
preferably from 5 to 50 Etm.
The dry and wet dimensional change of the proton
exchange membrane produced in the present invention is
preferably from 0 to 100%, more preferably from 0 to 50%,
and most preferably from 0 to 100. The dry and wet
dimensional change as used herein means a ratio of change
in the dimension after standing for 1 hour in water at
80°C based on the dimension after standing for 1 hour at
25°C-20 RHo. The dimension means a length in the machine
or transverse direction of the proton exchange membrane
and both lengths preferably satisfy the above-described
range.
A fuel cell is fabricated as follows by using the
proton exchange membrane of the present invention, and
the durability is evaluated.
(Membrane Electrode Assembly)
In the case of use for a solid polymer electrolyte
fuel cell, the proton exchange membrane obtained in the
present invention is used as a membrane electrode
assembly (hereinafter simply referred to as "MEA") where
two electrode catalyst layers of anode and cathode are
joined on both surfaces of the membrane. In some cases,
an assembly where a pair of gas diffusion layers are
joined to oppose each other on the further outer side of
the electrode catalyst layer is called MEA.
The electrode catalyst layer comprises a fine
particulate catalyst metal and an electrically conducting
agent having supported thereon the catalyst metal, and if
desired, contains a water repellent. The catalyst used
for the electrode may be sufficient if it is a metal of
accelerating an oxidation reaction of hydrogen and a
reduction reaction by oxygen, and examples thereof
include platinum, gold, silver, palladium, iridium,
rhodium, ruthenium, iron, cobalt, nickel, chromium,
tungsten, manganese, vanadium and alloys thereof. Among
CA 02563788 2006-10-20
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these, platinum is predominantly used.
As for the production method of MEA, for example,
the following method is used. An ion exchange resin is
dissolved in a mixed solution of alcohol and water, and a
platinum-supported carbon working out to an electrode
substance is dispersed therein to produce a paste state.
This paste in a predetermined amount is coated on a PTFE
sheet and dried. Then, coated surfaces of PTFE sheets
are opposed to each other and after interposing the
proton exchange membrane of the present invention
therebetween, these are transferred and joined by hot
pressing at 100 to 200°C, whereby MEA can be obtained.
(Fuel Cell)
The MEA obtained above or a structure that a pair of
gas diffusion electrodes are facing each other with the
MEA between is further combined with a component used for
general solid polymer electrolyte fuel cells, such as
bipolar plate and backing plate, thereby fabricating a
solid polymer electrolyte fuel cell.
The bipolar plate is, for example, a plate made of a
graphite-resin composite material or a metal, in which
channels for passing a gas such as fuel or oxidizing
agent are formed on the surface, and this plate has not
only a function of transmitting electrons to an exterior
load circuit but also a function as a flow path for
supplying a fuel or an oxidizing agent to the vicinity of
the electrode catalyst. MEA is inserted between bipolar
plates and a plurality of such combinations are stacked,
whereby a fuel cell is produced.
The present invention is described in greater detail
below by referring to Examples, but the present invention
should not be construed as being limited to these
Examples.
The evaluation methods and measurement methods used
in the present invention are as follows.
(Measurement of Proton Conductivity)
A membrane sample in a wet state is cut out and the
CA 02563788 2006-10-20
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thickness T is measured. The sample is loaded on a two-
terminal conductivity measuring cell for measuring the
conductivity in the length direction of a film having a
width of 1 cm and a length of 5 cm. This cell is placed
in ion exchanged water at 80°C, the resistance value R of
real number component at a frequency of 10 kHz is
measured by an AC impedance method, and the proton
conductivity a is determined according to the following
formula:
a=L/(RxTxW)
a: proton conductivity (S/cm),
T: thickness (cm),
R: resistance (S2) ,
L (=5): film length (cm), and
W (=1): film width (cm).
(Evaluation of Fuel Cell)
(1) Production of Fuel Cell
A proton exchange membrane is interposed between two
gas diffusion electrodes each coated on a mount and hot-
pressed at 180°C under a pressure of 10 MPa to transfer
and join the gas diffusion electrodes to the proton
exchange membrane, whereby MEA is produced.
The gas diffusion electrode used here is prepared as
follows. A solution obtained by concentrating a
perfluorosulfonic acid polymer solution SS-700x/05
(produced by Asahi Kasei Corporation, EW: 720, solvent
composition: ethanol/water=50/50 (by mass)) to 12 wto and
ethanol are added to a platinum-supported catalyst
TEC10E40E (loading percentage of platinum: 40 wto)
produced by Tanaka Kikinzoku Kogyo K.K., these are mixed
and stirred to produce an ink state, and the ink is
coated on a PTFE sheet and dried and solidified at 150°C
in an air atmosphere. In this gas diffusion electrode,
the amount of platinum supported is 0.4 mg/cm2 and the
amount of polymer supported is 0.5 mg/cm2.
A water repellent-treated carbon paper or carbon
CA 02563788 2006-10-20
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cloth is disposed on both sides of MEA prepared above and
the MEA is integrated into an evaluation cell and set in
an evaluation apparatus. Using hydrogen gas as the fuel
and air gas as the oxidizing agent, a single cell
characteristic test is performed at a cell temperature of
100°C under 0.1 MPa. For the gas humidification, a water
bubbling system is employed and both the hydrogen gas and
the air gas are supplied to the cell after being
humidified at 50°C.
(2) Measurement of Fluoride Release Rate
Waste waters discharged together with the anode
exhaust gas and cathode exhaust gas during the single
cell characteristic test each is trapped and recovered
for a predetermined time and then weighed. After fixing
a fluoride electrode 9609BNionplus manufactured by
Meditrial K.K. to a bench-top pH ion meter 920Aplus
manufactured by the same company, the fluoride ion
concentrations in the anode waste water and in the
cathode waste water are measured and the fluoride release
rate G is determined according to the following formula:
G=(WaxFa+WcxFc)/(TxA)
G: fluoride release rate (~g/Hr/cm2),
Wa: weight (g) of anode waste water trapped and
recovered,
Fa: fluoride ion concentration (ppm) in anode waste
water,
Wc: weight of cathode waste water trapped and
recovered,
Fc: fluoride ion concentration (ppm) in cathode
waste water,
T: time period (Hr) used for trapping and recovery
of waste water, and
A: electrode area (cm2) of MEA.
(3) Measurement of Cross-Leakage Amount
The cathode exhaust gas discharged during the single
cell characteristic test is partially introduced into a
CA 02563788 2006-10-20
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micro-gas chromatograph Micro GC CP-4900 manufactured by
GL Science, the hydrogen gas concentration in the cathode
exhaust gas is measured, and the hydrogen gas
permeability is determined according to the following
formula:
L=(XxVxT)x(5-U/100)/(3xAxP)x10-8
L: hydrogen gas permeability (mlxcm/cmz/sec/Pa),
X: hydrogen gas concentration (ppm) in cathode
exhaust gas,
V: cathode gas flow rate (ml/min),
T: thickness of proton exchange membrane (cm),
U: cathode gas utilization ratio (o),
A: hydrogen permeation area (cmz) of proton exchange
membrane, and
P: hydrogen partial pressure difference (Pa) between
cathode and anode.
The point of time when the hydrogen gas permeability
during the single cell characteristic test becomes 1.1x10-
11 (mlxcm/cm2/sec/Pa) or more is regarded as the cell
life, and the test is terminated at this point of time.
[Example 1]
Using a biaxial extruder (ZSK-40, manufactured by
WERNER & PFLEIDERER, Germany) set at a temperature of 280
to 310°C and a screw rotation number of 200 rpm, 99 parts
by weight of a precursor polymer (MI: 3.0, Ew after
alkali hydrolysis and acid treatment: 730) obtained from
tetrafluoroethylene and CF2=CFO(CF2)2-SO2F, 0.5 parts by
weight of polyphenylene sulfide (produced by Sigma-
Aldrich Japan K.K., melt viscosity at 310°C: 275 poise),
and 0.5 parts by weight of polyphenylene ether (obtained
by oxidative polymerization of 2,6-xylenol, reduced
viscosity: 0.51, glass transition temperature (Tg): 209°C)
were supplied from a first raw material supply port of
the extruder and melt-kneaded. Thereafter, the kneaded
material was melt-extruded by using a T-die extruder to
form a 50 ~m-thick film. This film was contacted with an
CA 02563788 2006-10-20
- 41 -
aqueous solution having dissolved therein potassium
hydroxide (15 masso) and dimethylsulfoxide (30 masso) at
60°C for 4 hours, thereby effecting an alkali hydrolysis
treatment, subsequently dipped in water at 60°C for 4
hours and then in an aqueous 2N hydrochloric acid
solution at 60°C for 3 hours, washed with ion exchanged
water and dried to obtain a proton exchange membrane (Ew:
736) .
The proton conductivity of the obtained proton
exchange membrane was as high as 0.23 (S/cm). This
proton exchange membrane was subjected to the evaluation
of fuel cell, as a result, the average fluoride release
rate in the waste water from the initiation until passage
of 200 hours showed a very low value of 0.038 (~g/Hr/cm2).
The cell life reached 750 hours, revealing that the
proton exchange membrane exhibits excellent durability.
[Example 2]
A proton exchange membrane (Ew: 737) was obtained in
the same manner as in Example 1 except for using
polysulfone (produced by Sigma-Aldrich Japan K.K., number
average molecular weight: 26,000) in place of
polyphenylene ether.
The proton conductivity of the obtained proton
exchange membrane was as high as 0.23 (S/cm). This
proton exchange membrane was subjected to the evaluation
of fuel cell, as a result, the average fluoride release
rate in the waste water from the initiation until passage
of 200 hours showed a very low value of 0.049 (~g/Hr/cm2).
The cell life reached 660 hours, revealing that the
proton exchange membrane exhibits excellent durability.
[Comparative Example 1]
A proton exchange membrane (EW: 730, MI: 3.0) was
obtained in the same manner as in Example l, except that
the precursor polymer (MI: 3.0, Ew after alkali
hydrolysis and acid treatment: 730) obtained from
tetrafluoroethylene and CFZ=CFO(CF2)2-SOzF was used alone.
CA 02563788 2006-10-20
- 42 -
The proton conductivity of the obtained proton
exchange membrane was as high as 0.23 (S/cm). This
proton exchange membrane was subjected to the evaluation
of a fuel cell, and as a result, the average fluoride
release rate in the waste water from the initiation until
the cell life showed a very high value of 0.506
(~g/Hr/cm2) and moreover, the cell life was less than 200
hours, failing to obtain a sufficiently high durability.
[Comparative Examples 2 to 35]
Using a biaxial extruder (ZSK-40, manufactured by
WERNER & PFLEIDERER, Germany) set at a temperature of 280
to 310°C and a screw rotation number of 200 rpm, 99 parts
by weight of a precursor polymer (MI: 3.0, Ew after
alkali hydrolysis and acid treatment: 730) obtained from
tetrafluoroethylene and CFZ=CFO(CFZ)z-S02F, 0.5 parts by
weight of Resin X, and 0.5 parts by weight of Resin Y
were supplied from a first raw material supply port of
the extruder and melt-kneaded. Thereafter, the kneaded
material was melt-extruded by using a T-die extruder to
form a 50 ~m-thick film. As for Resin X and Resin Y, the
following resins were used in various combinations. The
correspondence between the combination and Example or
Comparative Example No. is shown in Table 1.
Polyphenylene sulfide (in Table, denoted as PPS):
produced by Sigma-Aldrich Japan K.K., melt viscosity at
310°C: 275 poise
Polyphenylene ether (in Table, PPE): obtained by
oxidative polymerization of 2,6-xylenol, reduced
viscosity: 0.51, glass transition temperature (Tg): 209°C
~ Polysulfone (in Table, PSF): produced by Sigma-
Aldrich Japan K.K., number average molecular weight:
26, 000
'Polystyrene (in Table, PS): produced by Sigma
Aldrich Japan K.K., weight average molecular weight:
230,000
Epoxy resin (in Table, Epoxy): produced by Dai-
CA 02563788 2006-10-20
- 43 -
Nippon Ink & Chemicals, Inc., cresol novolak-type epoxy
resin N-660
Polyethersulfone (in Table, PES), produced by
AKROS Limited
~ Polyether ether sulfone (in Table, PEES): produced
by Sigma-Aldrich Japan K.K.
Polytetrafluoroethylene (in Table, PTFE): produced
by Daikin Kogyo Co., Ltd., FA-500
CA 02563788 2006-10-20
- 44 -
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CA 02563788 2006-10-20
- 45 -
These films were each contacted with an aqueous
solution having dissolved therein potassium hydroxide (15
masso) and dimethylsulfoxide (30 masso) at 60°C for 4
hours, thereby effecting an alkali hydrolysis treatment,
subsequently dipped in water at 60°C for 4 hours and then
in an aqueous 2N hydrochloric acid solution at 60°C for 3
hours, washed with ion exchanged water and dried to
obtain a proton exchange membrane.
Various proton exchange membranes each using a
combination of resins in Table 1 were subjected to the
evaluation of fuel cell, and the average fluoride release
rate in the waste water from the initiation until passage
of 200 hours (provided that when the cell life was less
than 200 hours, from the initiation until the cell life)
was determined. The results are shown in Table 2. It is
seen from comparison with Examples 1 and 2 that in all
fuel cells, the average fluorine dissolving-out rate was
at least 2 times larger and good durability was not
obtained.
TABLE 2
X/Y PPS PPE PSF PS Epoxy PES PEES PTFE
PPS 0.100 0.038 0.049 0.213 0.222 0.189 0.155 0.172
PPE - 0.784 0.362 0.953 0.845 0.665 0.536 0.683
PSF - - 0.152 0.736 0.557 0.273 0.202 0.279
PS - - - 1.061 1.022 0.802 0.654 0.897
Epoxy - - - - 0.973 0.679 0.514 0.748
PES - - - - - 0.450 0.428 0.430
PEES - - - - - - 0.382 0.401
PTFE - - - - - - - 0.425
unit: ~g/Hr/cm2
[Examples 3 to 12]
Proton exchange membranes were obtained in the same
manner as in Examples 1 and 2, except for changing the
compositional ratio or the like of Examples 1 and 2, and
subjected to the evaluation of fuel cell. The results
are shown in Table 3. In all fuel cells, not only the
average fluoride release rate in waste water from the
initiation until passage of 200 hours, but also the
fluoride release rate after about 500 hours were very
CA 02563788 2006-10-20
- 46 -
low. Moreover, the cell life exceeded 1,000 hours in all
samples and it was revealed that very excellent
durability is exhibited.
The change in each Example from Examples 1 and 2 is
described below.
[Example 3)
The compositional ratio of Example 1 was changed to
95 parts by weight of the precursor polymer obtained from
tetrafluoroethylene and CF2=CFO (CF2) 2-SOZF, 3 parts by
weight of polyphenylene sulfide and 2 parts by weight of
polyphenylene ether.
[Example 4]
The compositional ratio of Example 1 was changed to
95 parts by weight of the precursor polymer obtained from
tetrafluoroethylene and CFZ=CFO (CF2) 2-SOzF, 1 part by
weight of polyphenylene sulfide and 3 parts by weight of
polyphenylene ether.
[Example 5]
Polyphenylene sulfide (melt viscosity (a value
measured by using a flow tester after keeping at 300°C
under a load of 20 Kgf/cm2 with L/D (L: orifice length, D:
orifice inner diameter) - 10/1 for 6 minutes): 50 Pas,
amount extracted with methylene chloride: 0.7 wto, amount
of -SX group: 25 ~mol/g) was used, and the compositional
ratio of Example 1 was changed to 90 parts by weight of
the precursor polymer obtained from tetrafluoroethylene
and CFZ=CFO(CFZ)2-SOZF, 6 parts by weight of polyphenylene
sulfide and 2.5 parts by weight of polyphenylene ether.
[Example 6]
Polyphenylene sulfide (melt viscosity (a value
measured by using a flow tester after keeping at 300°C
under a load of 20 Kgf/cm2 with L/D (L: orifice length, D:
orifice inner diameter) - 10/1 for 6 minutes): 50 Pas,
amount extracted with methylene chloride: 0.7 wto, amount
of -SX group: 25 ~mol/g) was used, and the compositional
ratio of Example 2 was changed to 80 parts by weight of
CA 02563788 2006-10-20
- 47 -
the precursor polymer obtained from tetrafluoroethylene
and CF2=CFO (CF2) 2-S02F, 15 parts by weight of polyphenylene
sulfide and 5 parts by weight of polysulfone.
[Example 7]
Polyphenylene ether (obtained by oxidative
polymerization of 2,6-xylenol and 3,3',5,5'-tetramethyl
bisphenol A, reduced viscosity: 0.105, glass transition
temperature: 165°C) was used, and the compositional ratio
of Example 5 was changed to 70 parts by weight of the
precursor polymer obtained from tetrafluoroethylene and
CF2=CFO(CF2)z-SOZF, 25 parts by weight of polyphenylene
sulfide and 5 parts by weight of polyphenylene ether.
[Example 8]
To the components of Example 5, 0.3 parts by weight
of a styrene-glycidyl methacrylate copolymer (weight
average molecular weight: 110,000) containing 5 wto of
glycidyl methacrylate was further added.
[Example 9]
To the components of Example 8, 1.5 parts by weight
of a hydrogenated block copolymer having a polystyrene-
hydrogenated polybutadiene-polystyrene structure, in
which the amount of bonded styrene was 35 wto, the number
average molecular weight was 178,000, and the amount of
1,2-vinyl bond in the polybutadiene moiety before
hydrogenation was 480, was further added.
[Example 10]
An epoxy resin (produced by Dai-Nippon Ink &
Chemicals, Inc., cresol novolak-type epoxy resin N-660)
was further added to the components of Example 5, and the
compositional ratio was changed to 90 parts by weight of
the precursor polymer obtained from tetrafluoroethylene
and CFz=CFO (CFz) 2-S02F, 7 parts by weight of polyphenylene
sulfide, 1 part by weight of polyphenylene ether and 2
parts by weight of epoxy resin.
[Example 11]
In Example 5, an epoxy-modified polyphenylene ether
(prepared by previously mixing and reacting a
CA 02563788 2006-10-20
- 48 -
polyphenylene ether (obtained by oxidative polymerization
of 2,6-xylenol and 3,3',5,5'-tetramethyl bisphenol A,
reduced viscosity: 0.105, glass transition temperature:
165°C) and an epoxy resin (produced by Dai-Nippon Ink &
Chemicals, Inc., cresol novolak-type epoxy resin N-660))
was used in place of polyphenylene ether, and the
compositional ratio was changed to 90 parts by weight of
the precursor polymer obtained from tetrafluoroethylene
and CF2=CFO(CF2)2-SOZF, 7 parts by weight of polyphenylene
sulfide and 3 parts by weight of epoxy-modified
polyphenylene ether.
[Example 12]
A proton exchange membrane was obtained in the same
manner as in Example 4, except for changing the screw
rotation number of the twin screw extruder to 500 rpm.
The equivalent-circle average particle diameter of
dispersed particles in this proton exchange membrane was
0.9 ~m and small as compared with the equivalent-circle
average particle diameter (2.0 Vim) of the dispersed
particles in the proton exchange membrane of Example 4
having the same composition. This proton exchange
membrane was subjected to the evaluation of a fuel cell,
and as a result, the fluorine dissolving-out rate was
smaller than that of the proton exchange membrane of
Example 4, revealing that this proton exchange membrane
exhibits more excellent durability.
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TABLE 3
Proton Cross-Leakage Cell F Release
EquivalentConduc-Amount before Rate
Weight, tivity Operation Life (~g/Hr/cm')
Ew (Hr)
(S/cm) (ml~cm/cmz/sec/Pa) 200 500
Hr Hr
Example 736 0.23 5.6x10-13 750 0.038 0.083
1
Example 737 0.23 5.9x10-13 660 0.049 0.115
2
Example 767 0.24 5.9x10-1j >10000.016 0.025
3
Example 768 0.24 6.3x10-'3 >10000.034 0.056
4
Example 795 0.23 5.8x10-13 >10000.017 0.020
Example 903 0.21 5.4x10-13 >10000.021 0.022
6
Example 1032 0.18 5.1x10-13 >10000.016 0.017
7
Example 796 0.23 6.0x10-13 >10000.012 0.019
8
Example 799 0.24 5.8x10-13 >10000.009 0.013
9
Example 802 0.24 5,7x10-13 >10000.010 0.011
Example 798 0.23 5.5x10-13 >10000.009 0.010
11
Example 768 0.24 5,gx10-13 >10000.020 0.032
12
Comparative730 0.23 6.0x10-13 <200 0.506 -
Example
1
Comparative739 0.23 6.5x10-13 200 0.100 -
Example
2
Comparative1153 0.18 3.3x10-I3 360 0.035 -
Example
36
Comparative1225 0.17 2.5x10-14 410 0.029 -
Example
37
Comparative1010 0.18 1.1x10-13 370 0.043 -
Example
38
Comparative1189 0.15 4.0x10-13 340 0.033 -
Example
39
Comparative1110 0.20 7.2x10-13 300 0.632 -
Example
40
[Example 13]
In Example 11, the kneaded material was melt-
s extruded by using an annular die in place of a T-die
extruder and then inflation-molded to form a 50 ~m-thick
film. At this time, the diameter of the annular die was
50 mm, the slit opening was 500 Vim, the resin temperature
was 250°C, the longitudinal draw ratio was 3.3 times, and
10 the transverse blow-up ratio was 3.0 times. This film
was cut into a 7 cm square and freely shrunk in the plane
direction at 230°C for 10 minutes, as a result, almost the
same shrinkage was observed in both the machine direction
and the transverse direction. Although the film of
Example 11 obtained by using a T-die extruder exhibited a
behavior wherein large shrinkage occurred only in the
CA 02563788 2006-10-20
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machine direction and the transverse direction was rather
swelled, the film obtained in this example was confirmed
to exhibit a high-temperature dimensional change behavior
greatly different from this behavior. Furthermore, in
this film, the orientation balance was good, the
longitudinal and transverse anisotropy was small, and the
strength and reinforcement effect were changed for the
better.
This film was subjected to alkali hydrolysis
treatment, acid treatment, water washing and drying in
the same manner as in Example 11 to obtain a 50 ~m-thick
proton exchange membrane (Ew: 798).
The difference in the dry and wet dimensional change
between the machine direction and the transverse
direction of this proton exchange membrane was less than
2o and it was confirmed that the anisotropy of the film
was remarkably reduced as compared with the proton
exchange membrane of Example 11, where the difference in
the dry and wet dimensional change between the machine
direction and the transverse direction was about 200.
The proton conductivity of this proton exchange membrane
was as high as 0.25 (S/cm). When this proton exchange
membrane was subjected to the evaluation of fuel cell,
the average fluoride release rate in the waste water from
the initiation until passage of 200 hours showed a very
low value of 0.010 (~g/Hr/cm2), similarly to the proton
exchange membrane of Example 11, revealing that this
proton exchange membrane exhibits excellent durability.
[Example 14]
In Example 11, the kneaded material was melt-
extruded by using a T-die extruder to form a 200 ~m-thick
film, and this film was stretched at 120°C by a
simultaneous biaxial stretching apparatus (manufactured
by Toyo Seiki Seisaku-Sho, Ltd.) at a draw ratio of 2.0
times in the machine direction, at a draw ratio of 2.0
times in the transverse direction and at an area draw
CA 02563788 2006-10-20
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ratio of 4 times, and then subjected to alkali hydrolysis
treatment, acid treatment, water washing and drying in
the same manner as in Example 11 to obtain a 50 ~m-thick
proton exchange membrane (Ew: 798).
The piercing strength of this proton exchange
membrane was measured by using a handy compression tester
(manufactured by Kato Tech Co., Ltd.) (radius of probe:
0.5 mm, piercing rate: 2 mm/s, performed in air at 25°C)
and found to be about 2 times larger than that of the
proton exchange membrane of Example 11. Thus,
enhancement of the film strength was confirmed. The
proton conductivity of this proton exchange membrane was
as high as 0.26 (S/cm). When this proton exchange
membrane was subjected to the evaluation of fuel cell,
the average fluoride release rate in the waste water from
the initiation until passage of 200 hours showed a very
low value of 0.009 (~m/Hr/cm2), similarly to the proton
exchange membrane of Example 11, revealing that this
proton exchange membrane exhibits excellent durability.
[Example 15]
In Example 5, the kneaded material was melt-extruded
by using a T-die extruder to form a 40 ~m-thick film, and
this film was designated as Film A. Separately, the
compositional ratio of Example 5 was changed to 60 parts
by weight of the precursor polymer obtained from
tetrafluoroethylene and CF2=CFO (CF2) z-SOZF, 30 parts by
weight of polyphenylene sulfide and 10 parts by weight of
polyphenylene ether, and the kneaded material was melt-
extruded by using a T-die extruder to form a S ~m-thick
film, which was designated as Film B.
Film A was interposed between two sheets of Film B
and then press-bonded under heat at 290°C and 10 MPa to
form a film having a thickness of about 50 ~,m, and this
film was subjected to alkali hydrolysis treatment, acid
treatment, water washing and drying in the same manner as
in Example 5 to obtain a proton exchange membrane (Ew:
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861) .
The dry and wet dimensional change of this proton
exchange membrane was decreased to about 500 of that of
the proton exchange membrane of Example 5, and it was
confirmed that the dry and wet dimensional stability was
enhanced. The proton conductivity of this proton
exchange membrane was as high as 0.15 (S/cm). When this
proton exchange membrane was subjected to the evaluation
of fuel cell, the average fluoride release rate in the
waste water from the initiation until passage of 200
hours showed a very low value of 0.009 (~g/Hr/cm2),
similarly to the proton exchange membrane of Example 5,
revealing that this proton exchange membrane exhibited
excellent durability.
[Example 16J
In Example 11, the kneaded material was melt-
extruded by using a T-die extruder to form a 25 ~tm-thick
film, and this film was designated as Film A.
Separately, the compositional ratio of Example 5 was
changed to 50 parts by weight of the precursor polymer
obtained from tetrafluoroethylene and CFZ=CFO(CFZ)2-SOZF,
35 parts by weight of polyphenylene sulfide and 15 parts
by weight of polyphenylene ether, and the kneaded
material was melt-extruded by using a T-die extruder to
form a 5 ~m-thick film, which was designated as Film B.
Film B was interposed between two sheets of Film A
and then press-bonded under heat at 290°C and 10 MPa to
form a film having a thickness of about 55 Vim, and this
film was subjected to alkali hydrolysis treatment, acid
treatment, water washing and drying in the same manner as
in Example 11 to obtain a proton exchange membrane (Ew:
847).
The swelling percentage in the length direction of
this proton exchange membrane in water at 25°C was
decreased to about 450 of that of the proton exchange
membrane of Example 11, and it was confirmed that the
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dimensional stability under dry and wet conditions was
enhanced. The proton conductivity of this proton
exchange membrane was as high as 0.20 (S/cm). When this
proton exchange membrane was subjected to the evaluation
of fuel cell, the average fluoride release rate in the
waste water from the initiation until passage of 200
hours showed a very low value of 0.009 (~tg/Hr/cm2),
similarly to the proton exchange membrane of Example 11,
revealing that this proton exchange membrane exhibited
excellent durability.
[Example 17]
In Example 5, the kneaded material was melt-extruded
by using a T-die extruder to form a 25 ~m-thick film, and
this film was designated as Film A.
A 10 ~m-thick polyphenylene sulfide film (produced
by Toray Industries, Inc.) porosified to a porosity of
70o was interposed between two sheets of Film A and then
press-bonded under heat at 290°C and 10 MPa to form a film
having a thickness of about 50 Vim, and this film was
subjected to alkali hydrolysis treatment, acid treatment,
water washing and drying in the same manner as in Example
5 to obtain a proton exchange membrane (Ew: 853).
The dry and wet dimensional change of this proton
exchange membrane was decreased to about 300 of that of
the proton exchange membrane of Example 5, and it was
confirmed that the dry and wet dimensional stability was
enhanced. The proton conductivity of this proton
exchange membrane was as high as 0.17 (S/cm). When this
proton exchange membrane was subjected to the evaluation
of fuel cell, the average fluoride release rate in the
waste water from the initiation until passage of 200
hours showed a very low value of 0.009 (~g/Hr/cm2),
similarly to the proton exchange membrane of Example 5,
revealing that this proton exchange membrane exhibited
excellent durability.
[Example 18]
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In Example 5, the kneaded material was melt-extruded
by using a T-die extruder to form a 20 ~m-thick film, and
this film was designated as Film A.
Separately, in Example 5, a polyphenylene sulfide
containing 300 of glass fiber (produced by Dai-Nippon Ink
& Chemicals, Inc.) was used in place of the polyphenylene
sulfide, the compositional ratio was changed to 50 parts
by weight of the precursor polymer obtained from
tetrafluoroethylene and CFZ=CFO (CF2) 2-S02F, 45 parts by
weight of polyphenylene sulfide and 5 parts by weight of
polyphenylene ether, and the kneaded material was melt-
extruded by using a T-die extruder to form a 10 ~m-thick
film, which was designated as Film B.
Film B was interposed between two sheets of Film A
and then press-bonded under heat at 290°C and 10 MPa to
form a film having a thickness of about 50 Vim, and this
film was subjected to alkali hydrolysis treatment, acid
treatment, water washing and drying in the same manner as
in Example 5 to obtain a proton exchange membrane (Ew:
921) .
The dry and wet dimensional change of this proton
exchange membrane was decreased to about 30% of that of
the proton exchange membrane of Example 5, and it was
confirmed that the dry and wet dimensional stability was
enhanced. The proton conductivity of this proton
exchange membrane was as high as 0.17 (S/cm). When this
proton exchange membrane was subjected to the evaluation
of fuel cell, the average fluoride release rate in the
waste water from the initiation until passage of 200
hours showed a very low value of 0.009 (~g/Hr/cm2),
similarly to the proton exchange membrane of Example 5,
revealing that this proton exchange membrane exhibited
excellent durability.
[Comparative Examples 36 to 40]
Proton exchange membranes obtained by impregnating
various porous substrates with a perfluorocarbon sulfonic
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acid polymer were subjected to the evaluation of fuel
cell. The results are shown together in Table 3. In
some samples, the fluoride release rate was decreased
because of decrease in the ratio of perfluorocarbon
sulfonic acid polymer contained, but the cell life was
about 400 hours at longest and it was found that good
durability was not obtained in all samples.
The preparation method of the proton exchange
membrane in each Comparative Example is briefly described
below.
[Comparative Example 36]
A precursor polymer (MI: 3.0, Ew after alkali
hydrolysis and acid treatment: 730) obtained from
tetrafluoroethylene and CF2=CFO(CF2)2-SOZF was contacted
with an aqueous solution having dissolved therein
potassium hydroxide (15 masso) and dimethylsulfoxide (30
masso) at 60°C for 4 hours, thereby effecting an alkali
hydrolysis treatment, and after dipped in water at 60°C
for 4 hours, then dipped in an aqueous 2N hydrochloric
acid solution at 60°C for 3 hours, washed with ion
exchanged water and dried to obtain a perfluorocarbon
sulfonic acid polymer (Ew: 730). The obtained
perfluorocarbon sulfonic acid polymer was placed in an
autoclave together with an aqueous ethanol solution
(water:ethanol = 50.0:50.0 (by weight)), and the
autoclave was hermetically closed and after elevating the
temperature to 180°C, kept for 5 hours. Thereafter, the
autoclave was naturally cooled and Polymer Solution C
having a composition of perfluorocarbon sulfonic acid
polymer:water:ethanol = 5.0:47.5:47.5 (by weight) was
obtained.
A porosified polyphenylene sulfide film (obtained by
porosifying a 50 ~m-thick polyphenylene sulfide film
(produced by Toray Industries, Inc.) to a porosity of
600) was thoroughly impregnated with Polymer Solution C,
then placed in an oven, dried at 80°C for 1 hour and after
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elevating the temperature to 160°C, heat-treated for
another 1 hour to obtain a proton exchange membrane (Ew:
l, 153) .
[Comparative Example 37]
A proton exchange membrane (Ew: 1,225) was obtained
in the same manner as in Comparative Example 36, except
for using a polyimide porous substrate (produced by Ube
Industries, Ltd.) in place of the porosified
polyphenylene sulfide film.
[Comparative Example 38]
Polysulfone (produced by Sigma-Aldrich Japan K.K.,
number average molecular weight: 26,000) was added to
dimethylformamide and stirred at 80°C for 24 hours to
obtain a polysulfone solution. This solution was cast on
a glass plate by using a bar coater to a thickness of
about 50 ~m and then immediately dipped in water as a
poor solvent for 30 minutes to precipitate the
polysulfone, thereby effecting the porosification. The
obtained porous body was fixed at four sides, placed in
an oven and dried at 120°C for 24 hours to obtain a
porosified polysulfone film.
A proton exchange membrane (Ew: 1,010) was obtained
in the same manner as in Comparative Example 36, except
for using the porosified polysulfone film prepared above
in place of the porosified polyphenylene sulfide film.
[Comparative Example 39]
A porosified polyether sulfone film was obtained in
the same manner as in Comparative Example 38, except for
using a polyethersulfone (produced by Akros Limited) in
place of the polysulfone. A proton exchange membrane
(Ew: 1,189) was obtained in the same manner as in
Comparative Example 36, except for using the film
prepared above in place of the porosified polyphenylene
sulfide film.
[Comparative Example 40]
A proton exchange membrane (Ew: 1,110) was obtained
CA 02563788 2006-10-20
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in the same manner as in Comparative Example 36 except
for using a polytetraethylene porous substrate (WP500-
100, produced by Sumitomo Electric Industries, Ltd.) in
place of the porosified polyphenylene sulfide film.
As described in detail in the foregoing pages, the
proton exchange membrane obtained from the polymer
electrolyte composition of the present invention is a
proton exchange membrane ensuring high durability even
under high temperature and is suitably used in the fields
of ion exchange membrane and fuel cell. The proton
exchange membrane obtained according to the present
invention is usable for various fuel cells including
direct methanol-type fuel cell as well as for water
electrolysis, hydrogen halide acid electrolysis, sodium
chloride electrolysis, oxygen concentrator, moisture
sensor, gas sensor and the like.
