Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
COPOLYMER, POLYMER ELECTROLYTE, AND USE THEREOF
TECHNICAL FIELD
The invention relates to a copolymer preferably used for
materials of separating membrane for batteries, particularly
fuel cells, to a polymer electrolyte and use thereof.
BACKGROUND ART
As separating membranesfor electrochemical devices such
as primary batteries, secondary batteries, or solid polymer
fuel cells, polymer electrolytes having proton conductivity are
employed. For example, when polymer electrolytes containing
perfluoroalkane based polymers having perfluoroalkylsulfonic
acid groups as a superacid in the side chains, e.g., Nafion
(registered trade name; from Du Pont (E. I) de Nemours & Co.),
as an effective component are used as materials of separating
membrane for fuel cells, such polymer electrolytes are
excellent in properties of power generation and therefore are
mainly used at the present. However, such problems have been
pointed out that they are very expensive and inferior in heat
resistance and that those membranes has low strength for using
practically unless being somehow reinforced.
At the present situation, developments of polymer
electrolytes economical and excellent in properties and usable
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in place of the above-mentioned polymer electrolytes have been
made actively in recent years.
For example, block copolymers having a segment into which
substantially no sulfonic acid group is introduced and a segment
into which a sulfonic acid group is introduced, wherein the
former segment comprises a polyether sulfone and the latter
segment is a condensate of a diphenylsuifone and a biphenol
having sulfonic acid group are proposed (Japanese Unexamined
Patent Publication No. 2003-031232).
On the other hand, in place of the above-mentioned block
copolymers, so-called random copolymers having an acid group
distributed randomly along polymer chains has been also
investigated and random copolymers of one kind monomer into
which a sulfonic acid group is introduced and a monomer into
which no sulfonic acid group is introduced have been proposed
(see e.g., Japanese Unexamined Patent Publication Nos.
2004-509224 and 2006-523258, U.S. Patent Publication No.
2002/0091225, and Japanese Unexamined Patent Publication No.
2004-149779), or random copolymers obtained by sulfonation of
polyether sulfone copolymers (see e.g., Japanese Unexamined
Patent Publication No. 10-021943) have been proposed.
DISCLOSURE OF THE INVENTION
With respect to the block copolymers disclosed in
Japanese Unexamined Patent Publication No. 2003-031232, it was
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required to previously synthesize either one of the segment into
which substantially no sulfonic acid group is introduced or the
segment into which a sulfonic acid group is introduced and
thereafter carry out copolymerization with a monomer capable
of forming the other segment, or separately synthesize polymers
capable of forming the above-mentioned segments and thereafter
further carry out coupling both polymers.
On the other hand, with respect to the random copolymers
disclosed in Japanese Unexamined Patent Publication Nos.
2004-509224 and 2006-523258, U.S. Patent Publication No.
2002/0091225, Japanese Unexamined Patent Publication No.
2004-149779, and Japanese Unexamined Patent Publication No.
10-021943, as compared with the above-mentioned block
copolymers, their synthesis itself is relatively easy, however,
when it is tried to obtain practically useful proton
conductivity for materials of separating membrane for batteries,
the water absorbability of the random copolymers is increased
and separating membranes to be obtained have problems that their
sizes are significantly changed due to the water produced at
the time of operating fuel cell and consequently mechanical
strength is decreased. Particularly, according to the results
of the investigations the inventors of the present invention
have carried out, polymer electrolytes containing the random
copolymers which have been disclosed previously have
considerably high water absorbability of hot water at about
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100 C and therefore, when they are used for separating membranes
(polymer electrolyte membranes) of fuel cells, the polymer
electrolyte membranes themselves tend to be deformed by water
absorption due to heat generated by power generation.
The inventors of the present invention have investigated
repeatedly to solve the above-mentioned problems and
consequently, they have now completed the present invention.
That is, the invention provides a copolymer obtained by
nucleophilic condensation of a mixture of (A) and (C) with a
mixture of (B) and (D), or of a mixture of (A), (B), (C) and
(D) as follows:
(A) a monomer having two leaving groups and further at least
one acid group in a molecule;
(B) a monomer having two nucleophilic groups and further at
least one acid group in a molecule;
(C) a monomer having two leaving groups and substantially no
acid group in a molecule; and
(D) a monomer having two nucleophilic groups and substantially
no acid group in a molecule.
Herei.n, the nucleophilic groups means groups having
nucleophilicity, causing nucleophilic attack to atoms to which
the leaving groups are bonded and being thus capable of forming
new covalent bonds by condensation reaction which is
accompanied with elimination of the leaving groups. The
nucleophilic groups in the present invention differ from acid
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groups described below and have higher nucleophilicity than
that of the acid groups.
Since monomers having the nucleophilic groups and leaving
groups are different, the monomers having the nucleophilic
groups cause condensation reaction only with the monomers
having the leaving groups and form covalent bonds. In the
copolymers of the present invention, a structural unit (A')
derived from the above-mentioned (A) is adjacent to a structural
unit (B' ) derived from the above-mentioned (B) or a structural
unit ( D' ) derived from the above-mentioned (D): similarly the
structural unit (B') is adjacent to the structural unit (A')
or a structural unit (C' ) derived from the above-mentioned ( C):
also the structural unit (C' ) is adjacent to the structural unit
(B ' ) or the structural unit (D ' ): and the structural unit ( D' )
is adjacent to the structural unit (A') or the structural unit
(C').
Further, the present invention provides a copolymer
represented by the following [2] to [8].
[2] The copolymer according to the above-mentioned [1], in
which the above-mentioned (A) is represented by the following
formula (1):
X'-Ar'~Z1-----Ar2-X' (1)
k
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wherein, k denotes 0, 1, or 2; Arl and Ar2 each independently
denote a divalent aromatic group; when k is 2, two Ar2 groups
may be the same or different with each other and these divalent
aromatic groups may be substituted with an alkyl group having
1 to 10 carbon atoms which may have a substituent, an alkoxy
group having 1 to 10 carbon atoms which may have a substituent,
an aryl group having 6 to 10 carbon atoms which may have a
substituent, an aryloxy group having 6 to 10 carbon atoms which
may have a substituent, a fluoro group, a nitro group, or a
benzoyl group; when k is 0, Arl has at least one acid group,
and when k is 1 or more, at least one of Arl and Ar2 has at least
one acid group; Xl denotes one of a f luoro group, a chloro group,
a nitro group, or a trifluoromethanesulfonyloxy group; two Xl
groups may be the same or different with each other; Z' denotes
a group selected from the following groups; and when k is 2,
two Z' groups may be the same or different with each other:
Q Q Q Q
___5~..,. .__ C..__.. .__...~-c____
~
[3] The copolymer according to the above-mentioned [1] or [2],
wherein the above-mentioned (B) is represented by the following
formula (2):
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Y1-Ar3iQ1__'Ar4~Yj (2)
i
wherein, j denotes 0, 1, or 2; Ar3 and Ar4 each independently
denote a divalent aromatic group; when j is 2, two Ar4 groups
may be the same or different with each other and these divalent
aromatic groups may be substituted with an alkyl group having
1 to 10 carbon atoms which may have a substituent, an alkoxy
group having 1 to 10 carbon atoms which may have a substituent,
an aryl group having 6 to 10 carbon atoms which may have a
substituent, or an aryloxy group having 6 to 10 carbon atoms
which may have a substituent; when j is 0, Ar3 has at least one
acid group, and when j is 1 or more, at least one of Ar3 and
Ar4 has at least one acid group; Y' denotes a hydroxyl group,
a thiol group, or an amino group; two Y1 groups may be the same
or different with each other; Ql denotes a direct bond or a group
selected from the following groups; and when j is 2, two Q1 groups
may be the same or different with each other:
H2 CH3 CF3 Q
-0- -C -C_._. ____S._._.
CH3 CF3
p h -- --~
_..._S-. . _.~ .-.--Q--. 0
d P h -c_... ._._S
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[4] The copolymer according to the above-mentioned [1] to [3],
wherein the above-mentioned (C) is represented by the following
formula (3):
X2 Ar!~+Z2-Ar6--X2 ~3>
m
wherein, m denotes 0, 1, or 2; Ars and Ar6 each independently
denote a divalent aromatic group; when m is 2, two Ar6 groups
may be the same or different with each other and these divalent
aromatic groups may be substituted with an alkyl group having
1 to 10 carbon atoms which may have a substituent, an alkoxy
group having 1 to 10 carbon atoms which may have a substituent,
an aryl group having 6 to 10 carbon atoms which may have a
substituent, an aryloxy group having 6 to 10 carbon atoms which
may have a substituent, a fluoro group, a nitro group, or a
benzoyl group; X2 denotes a fluoro group, a chloro group, a nitro
group, or a trifluoromethanesulfonyloxy group; two X2 groups
may be the same or different with each other; Z2 denotes a group
selected from the following groups; and when m is 2, two Z2 groups
may be the same or different with each other:
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0 Q ~ 0
-s- .--c- --0-c-
tt
0
[5] The copolymer according to the above-mentioned [1] to [4],
wherein the above-mentioned (D) is represented by the following
formula (4):
Y2 A r7JQ2 __'A r8~Y2 (4)
n
wherein, n denotes 0, 1, or 2; Ar7 and Ar 8 each independently
denote a divalent aromatic group; when n is 2, two Ar8 groups
may be the same or different with each other and these divalent
aromatic groups may be substituted with an alkyl group having
1 to 10 carbon atoms which may have a substituent, an alkoxy
group having 1 to 10 carbon atoms which may have a substituent,
an aryl group having 6 to 10 carbon atoms which may have a
substituent, or an aryloxy group having 6 to 10 carbon atoms
which may have a substituent; Y2 denotes a hydroxyl group, a
thiol group, or an amino group; two Y2 groups may be the same
or different with each other; Q2 denotes a direct bond or a group
selected from the following groups; and when n is 2, two Q2 groups
may be the same or different with each other:
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H2 CH3 CF3 0
-0- -C _ ._._c_ _c- ._._S-
,
CH3 CF3
Ph Qo -C~ C~
O ph _..C_.. .._5..~
[6] The copolymer according to the above-mentioned [1] to [5],
wherein the acid group is a strong acid group or a superacid
group.
[7] The copolymer according to the above-mentioned [1] to [6]
having an ion exchange capacity of 0.1 meq/g to 4.0 meq/g.
[8] The copolymer according to the above-mentioned [1] to [7],
wherein the weight composition ratio of the structural unit into
which the acid group is introduced and the structural unit into
which substantially no acid group is introduced, [structural
unit into which the acid group is introduced ]: [structural unit
into which substantially no acid group is introduced], is 3
97 to 70 : 30.
In addition, the invention also provides the following.
[9] A polymer electrolyte containing the copolymer according
to any one of the [1] to [8].
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[10] A polymer electrolyte membrane containing the polymer
electrolyte according to the [9].
[11] A polymer electrolyte composite membrane comprising the
polymer electrolyte according to the[9]and a porous substrate.
[12] A polymer electrolyte composite membrane obtained by
impregnating a porous substrate with the polymer electrolyte
according to the [9], and compositing those.
[13] A catalyst composition comprising the polymer
electrolyte according to the [9] and a catalyt material.
(14] A fuel cell using the polymer electrolyte membrane
according to the [10].
[15] A fuel cell using the polymer electrolyte composite
membrane according to the [11] or (12].
[16] A fuel cell having a catalyst layer comprising the
catalyst composition according to the [13].
Further, the present invention provides
[17] A method of producing a copolymer, wherein a mixture of
(A) and (C) with a mixture of (B) and (D) is condensed, or a
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mixture of (A), (B), (C) and (D) is condensed as follows:
(A) a monomer having two leaving groups and further at least
one acid group in a molecule;
(B) a monomer having two nucleophilic groups and further at
least one acid group in a molecule;
(C) a monomer having two leaving groups and substantially no
acid group in a molecule; and
(D) a monomer having two nucleophilic groups and substantially
no acid group in a molecule.
BEST MODES FOR CARRYING OUT THE INVENTION
Hereinafter, preferable embodiments of the present
invention will be described.
A copolymer of the present invention can be obtained by
mixing and condensing, as indispensable monomers, a mixture of
two kind specified monomers having acid groups (the
above-mentioned (A) and (B)) with a mixture of two kind
specified monomers substantially having no acid group (the
above-mentioned (C) and (D)). One or more kinds of monomers
(A), (B), (C), and (D) may be used respectively.
The above-mentioned (A) is preferably a compound
represented by the above-mentioned formula (1). Herein, the
acid groups are characterized in that when k is 0, Arl has the
acid groups, and when k is 1 or more, at least one of Arl and
Ar2 has the acid groups. Arl and Ar2 denote a divalent aromatic
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group and examples of the divalent aromatic group may be
hydrocarbon based aromatic groups such as a phenylene group,
a naphthylene group, a biphenylylene group, and a fluorenediyl
group and heterocyclic groups such as a pyridinediyl group, a
quinoxalinediyl group and a thiophenediyl group and among them,
divalent hydrocarbon based aromatic groups are preferable and
a phenylene group and a naphthylene group are particularly
preferable. When k is 1, Arl and Ar2 may be the same or different
and when k is 2, Arl and two Ar2 groups may be the same or
different.
Herein, the above-mentioned divalent aromatic groups may
be substituted with an alkyl group having 1 to 10 carbon atoms
which may have a substituent, an alkoxy group having 1 to 10
carbon atoms which may have a substituent, an aryl group having
6 to 10 carbon atoms which may have a substituent, an aryloxy
group having 6 to 10 carbon atoms which may have a substituent,
a nitro group and a benzoyl group and examples of the alkyl group
having 1 to 10 carbon atoms may include such as a methyl group,
an ethyl group, an n-propyl group, an isopropyl group, an allyl
group, an n-butyl group, a sec-butyl group, a tert-butyl group,
an isobutyl group, an n-pentyl group,2,2-dimethylpropyl group,
a cyclopentyl group, an n-hexyl group, a cyclohexyl group,
2-methylpentyl group and 2-ethylhexyl group and these groups
may have halogen atoms such as fluorine atom, chlorine atom,
bromine atom or iodine atom, a hydroxyl group, an amino group,
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a methoxy group, an ethoxy group, an isopropyloxy group, a
phenyl group, a naphthyl group, a phenoxy group, and a
naphthyloxy group as a substituent.
Examples of the alkoxy group having 1 to 10 carbon atoms
may include a methoxy group, an ethoxy group, an n-propyloxy
group, an isopropyloxy group, an n-butyloxy group, a
sec-butyloxy group, a tert-butyloxy group, an isobutyloxy group,
an n-pentyloxy group, 2,2-dimethylpropyloxy group, a
cyclopentyloxy group, an n-hexyloxy group, a cyclohexyloxy
group, 2-methylpentyloxy group and 2-ethylhexyloxy group and
these groups may have substituents selected from a halogen atom,
a hydroxyl group, an amino group, a methoxy group, an ethoxy
group, an isopropyloxy group, a phenyl group, a naphthyl group,
a phenoxy group, and a naphthyloxy group as a substituent.
Examples of the aryl group having 6 to 10 carbon atoms
may include a phenyl group and a naphthyl group and these groups
may have substituents selected from halogen atoms, a hydroxyl
group, an amino group, a methoxy group, an ethoxy group, an
isopropyloxy group, a phenyl group, a naphthyl group, a phenoxy
group, and a naphthyloxy group as a substituent.
Examples of the aryloxy group having 6 to 10 carbon atoms
may include a phenoxy group and a naphthyl oxy group and these
groups may have substituents selected from halogen atoms such
as fluorine atom, chlorine atom, bromine atom or iodine atom,
a hydroxyl group, an amino group, a methoxy group, an ethoxy
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group, an isopropyloxy group, a phenyl group, a naphthyl group,
a phenoxy group, and a naphthyloxy group as a substituent.
Arl and Ar2 in the formula (1) respectively denote a
divalent aromatic group which may have a substituent as
described above, and as Arl and Ar2, particularly an
unsubstituted phenylene group or an unsubstituted naphthylene
group is preferable and 1,3-phenylene group, 1,4-phenylene
group, 1,3-naphthalenediyl group, 1,4-naphthalenediyl group,
1,5-naphthalenediyl group, 1,6-naphthalenediyl group,
1,7-naphthalenediyl group, 2,6-naphthalenediyl group,
2,7-naphthalenediyl group, 3,3'-biphenylylene group,
3,4'-biphenylylene group, and 4,4'-biphenylylene group are
preferable.
Further, k in the formula (1) denotes 0, 1, or 2 and Z'
denotes CO (carbonyl group), or SO2 (sulfonyl group), or COCO
(dicarbonyl group ). When k is 2, two Zl groups may be the same
or different with each other and it is particularly preferable
that Z' groups are the same.
The present invention is characterized in that, among Arl
and Ar2 groups as described above, at least one of Arl and Ar2
has an acid group and when k is 1 or more, all of the groups
represented by Arl and Ar 2 are preferable to have acid groups.
Herein, examples of the acid groups are weak acid groups
such as a carboxyl group (-COOH), a phosphonic acid group
(-P03H2) and a phosphoric acid group (-OP03H2); strong acid
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groups such as a sulfonic acid group (- SO3H ) and a sulfonylimido
group (-SO2NHSO2-R, wherein R denotes an alkyl group having 1
to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms);
and a superacid group such as a perfluoroalkylenesulfonic acid
group, a perfluorophenylenesulfonic acid group, and a
perfluoroalkylenesulfonylimido group. Among them, a strong
acid group or a superacid group whose acid dissociation constant
represented by a pKa value is 2 or lower is preferable, for
example, a sulfonic acid group, a perfluoroalkylenesulfonic
acid group, or a perfluorophenylenesulfonic acid group is
preferable. When these acid groups are protonic acids, they
may form salts with such as alkali metal ions, alkaline earth
metal ions, or ammonium ion and the acid groups forming the salts
can easily be turned back to free acid forms by ion exchange
with acid treatment after formation of the copolymerization of
the present invention.
Preferable examples of the compound represented by the
formula (1) are, for example, the following (1)-1 to (1)-4:
0 O
--i~ ----~~-- -~--
F ~ , S ~ / F (2)-1 cl !s c1 (1) - 3
(SO3M)r 0 (SO3M)s (SO3M)r 1 (S03M)s
_ ~ _ _
F \ / C F (1)-2 C! \ / c \ / a (1)-4
(S03iV{)r (S03M)s (S03M)r (SO3M)s
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wherein, r and s each independently denote 0 or 1 and r + s is
1 or 2; M denotes hydrogen atom, potassium atom, sodium atom,
or lithium atom; and when there are a plurality of M, they may
be same or different.
It is preferable that the above-mentioned (B) should
contain a compound represented by the formula (2).
Herein, the acid groups are characterized in that when
j is 0, Ar3 has the acid groups, and when j is 1 or higher, at
least one of Ar3 and Ar4 have the acid groups. Ar3 and Ar4 denote
a divalent aromatic group and examples of the divalent aromatic
group may be groups same as the above-mentioned groups for Arl
and Ar2 and when j is 2, Ar3 and two Ar4 groups may be the same
or different with each other. In addition, a phenolic hydroxyl
group among the nucleophilic groups represented by Y' is a group
which can be converted into a phenolate group with a proper base
in the condensation reaction process and reacts as a
nucleophilic group and also a group existing in form of an ether
bond in the copolymer of the present invention and is thus not
regarded as an acid group.
These divalent aromatic groups may be substituted with
an alkyl group having 1 to 10 carbon atoms which may have a
substituent, an alkoxy group having 1 to 10 carbon atoms which
may have a substituent, an aryl group having 6 to 10 carbon atoms
which may have a substituent, an aryloxy group having 6 to 10
carbon atoms which may have a substituent, and specif ic examples
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of the alkyl group, the alkoxy group, the aryl group, or the
aryloxy group are those same as the exemplified above.
Ar3 and Ar4 in the formula (2) denote a divalent aromatic
group which may have the above-mentioned substituent group and
as Ar3 and Ar4, particularly an unsubstituted phenylene group,
an unsubstituted biphenylylene group, or an unsubstituted
naphthylene group is preferable and 1,3-phenylene group,
1,4-phenylene group, 1,3-naphthalenediyl group,
1,4-naphthalenediyl group, 1,5-naphthalenediyl group,
1,6-naphthalenediyl group, 1,7-naphthalenediyl group,
2,6-naphthalenediyl group, 2,7-naphthalenediyl group,
3,3'-biphenylylene group, 3,4'-biphenylylene group, or
4,4'-biphenylylene group is preferable.
In addition, j in the formula (2) denotes 0, 1 or 2; Q1
denotes a direct bond or a group selected from the following
groups. When j is 2, two Ql groups may be the same or different
with each other, and two Q1 groups are preferably the same as
each other.
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CH3 ?Fa Q
-0- -C -C- ~G -C- -S-
H2 CH3 CF3
t~ Ph Q .._s- ..~C .~0 o
fl
o Ph c
Preferable examples of the compound represented by the
formula (2) include the following (2)-1 to (2)-12.
HO G 4H !2)-1 HO \ J ~ JOH (2)-4 M038 CF3 S03M
SO"M 1 r(M03S) (503M)g Ha Z~ CF ~ J OH {2}-8
3
~ HO ~ 1 O~, J OH {2}_$ MO3S Me 803M
HO \ ; OH (2)-2 ,(MOaS) (S03M)e l..10 ~ ~ 6 OH {2}-9
SO~M HO ~ ~ OH
Me
~1 ,, 2)-6
HO OH (2)-3 M03S S03M {
J Mo3s ' i~ oH (2)-7 Ha $~ c~ S aH (2)-10
$O~M HO SOSM
HO ''1 OH M03S S03M
MO S SO3M (2)-12 HO C S-O~-OH (2)-11
MO3S O 0 SO3M
Next, monomers having substantially no acid group will
be described. Herein, "having substantially no acid group"
means, similar to the above-mentioned hydroxyl group, a kind
of acid groups which exists in a monomer as a nucleophilic group
and disappears in the process of forming a copolymer is not
regarded as an acid group in the present invention and therefore,
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even such a monomer having an acid group is regarded as monomers
having substantially no acid group in the present invention.
The above-mentioned (C) is preferably a compound
represented by the formula (3).
Ar5 and Ar6 in the formula (3) denote, as a divalent
aromatic, a hydrocarbon based aromatic group such as a phenylene
group, a naphthylene group, a biphenylylene group and a
fluorenediyl group and a heterocyclic group such as a
pyridinediyl group, a quinoxalinediyl group, and a
thiophenediyl and preferably a divalent hydrocarbon based
aromatic group. When m is 1, Ar5 and Ar6 may be the same or
different, and when m is 2, Ar5 and two Ar6 groups may be the
same or different.
These divalent aromatic groups may be substituted with
an alkyl group having 1 to 10 carbon atoms which may have a
substituent, an alkoxy group having 1 to 10 carbon atoms which
may have a substituent, an aryl group having 6 to 10 carbon atoms
which may have a substituent, an aryloxy group having 6 to 10
carbon atoms which may have a substituent, a nitro group, and
a benzoyl group and specific examples of the alkyl group, the
alkoxy group, the aryl group, or the aryloxy group are those
same as exemplified above.
As Ar5 and Ar6, particularly an unsubstituted phenylene
group, or an unsubstituted naphthylene group is preferable and
1, 3-phenylene group, 1, 4-phenylene group, 1,3-naphthalenediyl
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group, 1,4-naphthalenediyl group, 1,5-naphthalenediyl group,
1,6-naphthalenediyl group, 1,7-naphthalenediyl group,
2,6-naphthalenediyl group, 2,7-naphthalenediyl group,
3,3'-biphenylylene group, 3,4'-biphenylylene group, or
4,4'-biphenylylene group is preferable.
In addition, m in the formula (3) denotes 0, 1, or 2 and
ZZ denotes CO, SOZ, or COCO. When m is 2, two Z2 groups may be
the same or different and it is preferable that two Z2 groups
are the same each other.
Preferable examples of the compound represented by the
formula (3) include the following (3)-i to (3)-9.
O
F (3)-1 (3)-6
Q Q
O 0
I1 _ _
C-Q F(3)'2 (3)-7
00
F-acll-cll ~F(3)-3 ~= ~ F (3)-8
2
NO2 NO
F-0 F (3)-4 F F F F (3)-9
F FF F l F F
~ ~ ~ F (3)-5
F FF F
It is preferable that the above-mentioned (D) preferably
contains a compound represented by the formula (4)
Ar' and Ar8 in the formula (4) denote a divalent aromatic
group and examples of the divalent aromatic group may be groups
same as the above-mentioned groups for Ar5 and Ar6 and these
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divalent aromatic groups may be substituted with an alkyl group
having 1 to 10 carbon atoms which may have a substituent, an
alkoxy group having 1 to 10 carbon atoms which may have a
substituent, an aryl group having 6 to 10 carbon atoms which
may have a substituent, an aryloxy group having 6 to 10 carbon
atoms which may have a substituent, and specific examples of
the alkyl group, the alkoxy group, the aryl group, or the aryloxy
group are those same as the exemplified above.
As Ar' and Ar8, particularly an unsubstituted phenylene
group, an unsubstituted biphenylylene group, or an
unsubstituted naphthylene group is preferable and
1, 3-phenylene group, 1, 4-phenylene group, 1, 3-naphthalenediyl
group, 1,4-naphthalenediyl group, 1,5-naphthalenediyl group,
1,6-naphthalenediyl group, 1,7-naphthalenediyl group,
2,6-naphthalenediyl group, 2,7-naphthalenediyl group,
3,3'-biphenylylene group, 3,4'-biphenylylene group, or
4,4'-biphenylylene group is preferable.
In addition, n in the formula (4) denotes 0, 1 or 2; Q2
denotes a direct bond or a group selected from the following
groups. When n is 2, two Q2 groups may be the same as or different
each other, and two Q2 groups are preferably the same each other.
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H2 9H3 CF3 0
-p--- -C -C- ._._.S_._.
CH3 CF3
Ph
0
11 _S_ ~_.. _C_ o
0 Ph c~ S
Preferable examples of the compound represented by the
formula (4) include the following (4)-1 to (4)-26.
HO \ ! O \ / OH (4)-1 HO \ ! C\ / OH (4)-10
Ho \ ! s ~oH (4)-2
Ho ac O oH (4)-3 OCO
H2
HO OH
Me
HO \ / ~ \ ! oH (4)-4 HO ~ ! ~ ! oH (4)-12
l
Me
O HO ~OH (4)-13
HO ~ ! ~s ~oH (4)-5 b
11
0
O
Ho \ / C \ ! oN (4)-6 Ho \ r o \ ! oH (4)-14
CF3 Ho '/ c t/OH (4)-7 ' I
C Me Me
HO OH HO \/ C\! C\/ OH (4)-15
CF3
\ / O \ ! O \ ! (4)-8 Me Me
H0 ! \ O ad \ ! OH (4)-9
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Ho G oH (4)-16 , E H ~ t~ oH (4)-23
. . (4)-20 HO
Ho RoH (4)-17 OH OH (4)-24
HO r~ OH ~4)-21 H~ ~ ~ ~
Ho ~ i oH (4)-18 Ho oH HO ~ i~ oH (4)-25
. .
8~\/I (4)-22 oH
(4)-19 Ho
HO ~ i ~ (4)-26
~ rOH
A copolymer of the present invention can be produced by
either mixing a mixture of the above-mentioned (A), (B), (C),
and (D), or mixing monomers having nucleophilic groups, for
example, (B) and (D) and separately mixing monomers having
leaving groups, f or example,( A) and (C) and further mixing the
respective mixtures, and successively subjecting to
nucleophilic condensation reaction of the monomers having
nucleophilic groups and the monomers having leaving groups.
A preferable copolymer of the present invention can be
obtained using the compounds represented by the above-mentioned
formulas (1) to (4) as monomers and mixing and condensing them.
An example includes a method of carrying out nucleophilic
condensation of the compounds represented by the formulas (1)
to (4) in the presence of a base.
Specifically, the compounds represented by the formulas
(1) to (4) and a basic compound are charged into a reaction
solvent and mixed. The order of mixing is not particularly
limited, however, preferable mixing method is previously
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charging the compound represented by the formula (2), the
compound represented by the formula (4), the basic compound and
the solvent, and then mixing the above-mentioned (1) and (3);
or mixing the compounds represented by the formulas (1) to (4)
and the solvent, and then charging and mixing the basic
compound; or charging and mixing the compounds represented by
the formulas (1) to (4), the basic compound and the solvent.
In the condensation, the reaction temperature is preferably 20
to 300 C and further preferably 50 to 250 C and the reaction
time can be carried out preferably 0.5 to 500 hours and more
preferably 1 to 100 hours. In addition, with respect to the
pressure at the time of the reaction, the pressure may be
pressurized or reduced, and normal pressure (about atmospheric
pressure) is preferable since it is convenient in terms of
facilities. As a reaction solvent, alcohol based solvents such
as methanol, ethanol, isopropanol, and butanol; ether based
solvents such as diethyl ether, dibutyl ether, diphenyl ether,
tetrahydrofuran, dioxane, dioxolane, ethylene glycol
monomethyl ether, ethylene glycol monoethyl ether, propylene
glycol monomethyl ether, and propylene glycol monoethyl ether;
ketone based solvents such as acetone, methyl isobutyl ketone,
methyl ethyl ketone, and benzophenone; halogen based solvents
such as chloroform, dichloromethane, 1,2-dichloroethane,
1,1,2,2-tetrachloroethane, chlorobenzene, and
dichlorobenzene; amide based solvents such as
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N,N-dimethylacetamide (hereinafter, sometimes abbreviated as
DMAc), N-methylacetamide, N,N-dimethylformamide (hereinafter,
sometimes abbreviated as DMF), N-methylformamide, formamide,
and N-methyl-2-pyrrolidone (hereinafter, sometimes
abbreviated as NMP); esters such as methyl formate, methyl
acetate, andy-butyrolactone; nitriles such as acetonitrile and
butyronitrile; sulfoxydimethyl sulfoxide (hereinafter,
sometimes abbreviated as DMSO), diphenylsulfone, sulfolane,
and the like can be used. The reaction solvents may be used
alone, or two or more kinds of the reaction solution may be used
in combination. The used amount of the reaction solvents is
1. 0 to 200. 0 times by weight, preferably 2. 0 to 100. 0 times by
weight, based on the total weight of the used monomers. Here,
it is preferable to remove water of by-product in the initial
period of condensation reaction or during the condensation
reaction. The method of removing the water to be employed may
be the method of removing water in form of an azeotropy by making
toluene and xylene coexist in the reaction system and the method
of dehydrating by making water absorbent such as a molecular
sieve coexist in the reaction system. As the above-mentioned
basic compound, sodium hydroxide, potassium hydroxide, sodium
carbonate, potassium carbonate, sodium hydrogen carbonate, or
potassium hydrogen carbonate may be used, and the mixture of
two or more basic compounds may be used and especially potassium
carbonate, sodium carbonate, or sodium hydroxide is pref erable.
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Here, the used amount of the basic compound may be 0.90 to 10.00
times by mole equivalent, preferably 1.00 to 3.00 times by mole
equivalent based on the total mole equivalent to the
nucleophilic groups in the used monomers in the condensation
reaction.
Another embodiment in a preferable production method of
the copolymer of the present invention may be a method of
previously reacting the compound represented by the formula(2)
and the compound represented by the formula (4) with the basic
compound, and then charging the compounds represented the
formula (1) and the compound represented by the formula (3) and
mixing the compounds, and successively carrying out
condensation. That is, after compound represented by the
formula (2), the compound represented by the formula (4), and
the basic compound are mixed in the reaction solvent and, if
necessary, heating treatment is carried out to react the basic
compound with the compound represented by the formula (2) and
the compound represented by the formula (4), the compounds
represented by the formula (1) and the compound represented by
the formula (3) are added to the mixture and then the
condensation reaction is carried out. The reaction solvent to
be used and used amount thereof and the basic compound to be
used and used amount thereof are the same as described above
and the reaction temperature and the reaction time relevant to
the condensation reaction are in the same ranges as described
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above. Removal of the water of by-product may be carried out
in the same manner as described above or it may be a method of
sufficiently removing water in form of azeotropy by making
toluene and xylene coexist in the reaction system upon mixing
the compound represented by the formula (2), the compound
represented by the formula (4) , and the basic compound with the
reaction solvent, and successively adding the compound
represented by the formula (1) and the compound represented by
the formula (3) to the mixture and carrying out condensation
reaction.
Consequently, the copolymer of the present invention is
obtained. With respect to the copolymer, the weight
composition ratio of the structural unit into which the acid
group is introduced and the structural unit into which
substantially no acid group is introduced is not particularly
limited, however, in general, the ratio of [structural unit
into which the acid group is introduced] :[ structural unit into
which substantially no acid group is introduced] is 3 : 97 to
70 : 30, preferably 5 : 95 to 45 : 55, more preferably 10 : 90
to 40 : 60, and even more preferably 20 : 80 to 35 : 65. The
copolymer having the ratio of the structural unit into which
the acid group is introduced within the above-mentioned range,
becomes a polymer electrolyte membrane having both of proton
conductivity and water-proofness at a high level, when the
copolymer is used for a polymer electrolyte membrane of a
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separating membrane of a fuel cell.
Here, the weight composition ratio of the structural unit
into which the acid group is introduced and the structural unit
into which substantially no acid group is introduced can be
controlled by the used amount of the monomers and, for example,
the weight composition ratio can be properly controlled by
changing the charging (mixing) mole ratio in the initial
reaction stage of the total mole amount of the monomers having
acid groups, containing the compound represented by the formula
(Z) and the compound represented by the formula (2) and the total
mole amount of the monomers having substantially no acid group,
containing the compound represented by the formula (3) and the
compound represented by the formula (4).
On the basis of equivalent amount of the acid group per
1 g of the copolymer, that is, the ion exchange capacity, the
introduction amount of the acid group in the entire copolymer
is preferably 0.1 meq/g to 4.0 meq/g, more preferably 0.5 meq/g
to 2.5 meq/g, and even more preferably 1.3 meq/g to 2.3 meq/g.
The reason for that the ion exchange capacity is preferably in
the above-mentioned range is the same reason for the ratio of
the content weight the structural unit into which the acid group
is introduced in the copolymer and the ion exchange capacity
can also be controlled arbitrarily in the same manner of
changing the charging (mixing) mole ratio of the respective
monomers in the initial reaction stage.
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The average molecular weight of the copolymer of the
present invention is preferably 5000 to 1000000 and especially
further preferably 15000 to 200000 on the basis of the number
average molecular weight converted into polystyrene.
The above-mentioned average molecular weight can be
controlled in accordance with such the ratio of total mole
equivalent amount of the nucleophilic groups of the monomers
to be used and the total mole equivalent of the leaving groups
and the reaction time.
Next, the case of using the copolymer of the present
invention for a separating membrane (polymer electrolyte
membrane) of an electrochemical device such as a fuel cell will
be described.
In this case, the copolymer of the present invention may
be used, in general, in form of a membrane. A method for
converting the copolymer into a membrane is not particularly
limited; however a method of forming a membrane from a solution
(a solution cast method) is preferably employed.
Specifically, the copolymer is dissolved in a suitable
solvent and the obtained solution is applied to a glass plate
and the solvent is removed to form a membrane. The solvent to
be used for membrane formation is not particularly limited if
it is capable of dissolving the copolymer and removing
thereafter and water and non-protonic polar solvents such as
N,N-dimethylformamide, N,N-dimethylacetamide,
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N-methyl-2-pyrrolidone, and dimethyl sulfoxide; chlorinated
solvents such as dichloromethane, chloroform,
1,2-dichioroethane, chlorobenzene, and dichlorobenzene;
alcohols such as methanol, ethanol, and propanol; and alkylene
glycol monoalkyl ethers such as ethylene glycol monomethyl
ether, ethylene glycol monoethyl ether, propylene glycol
monomethyl ether, and propylene glycol monoethyl ether are
preferably used. They may be used alone and if necessary two
or more kinds of solvents may be used in form of a mixture.
Especially, DMSO, DMF, DMAc, and NMP are preferable, having high
solubility of polymers.
The thickness of the membrane is not particularly limited
and preferably 10 to 300 um and particularly preferably 20 to
100 pm. If a film is thinner than 10 pm, the practical strength
is sometimes insufficient and if a film is thicker than 300 }im,
the membrane resistance becomes high and the properties of the
electrochemical device tend to deteriorate. The thickness of
the membrane can be controlled by the concentration of the
solution and the application thickness of the solution to the
substrate.
As a purpose of improving the various kinds of physical
properties of the polymer electrolyte membrane, such as a
plasticizer, a stabilizer, and a release agent to be used for
common polymers may be added to the copolymer of the present
invention. In addition, it is also possible that another
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polymer is composite alloyed with the copolymer of the present
invention by a method for mixing and cocasting the polymer in
the same solvent.
To make water control easy in application to a fuel cell,
it is also known that inorganic or organic fine particles are
added as a water retention agent. Any of these conventionally
known methods can be employed unless it is contradictory for
the purpose of the present invention. Further, in order to
improve the mechanical strength of the polymer electrolyte
membrane comprising the polymer electrolyte containing the
copolymer of the present invention, electron beam and radiation
beam may be radiated to cross-link the polymer electrolyte
composing the polymer electrolyte membrane.
In addition, in order to further improve strength,
flexibility, and durability of the polymer electrolyte membrane,
it is allowed to impregnate a porous substrate with the
copolymer of the present invention to produce a polymer
electrolyte composite membrane. A conventionally known method
can be employed for a compositing method. The porous substrate
is not particularly limited if it can satisfy the
above-mentioned purpose of the use and examples may include,
such as a porous membrane, a woven f abric, a non -woven f abric ,
and fibril and they may be used regardless of the shape and
quality of material thereof.
When the polymer electrolyte composite membrane using the
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copolymer of the present invention is used as a separating
membrane for fuel cells, the thickness of the porous substrate
is 1 to 100 pm, preferably 3 to 30 pm, and more preferably 5
to 20 pm; the pore diameter is 0.01 to 100 pm and preferably
0.02 to 10 pm; and the porosity is 20 to 98% and preferably 40
to 95%. If the thickness of the porous substrate is too thin,
the effect of reinforcing the strength after compositing or the
reinforcing effect of imparting flexibility and durability
becomes insufficient and thus gas leakage (cross leakage) is
caused easily. In addition, if the thickness of the membrane
is too thick, the electric resistance becomes high and the
obtained composite membrane becomes improper as the separating
membrane of a solid polymer fuel cell. If the pore diameter
is too small, it becomes difficult to fill the copolymer of the
present invention and if it is too high, the reinforcing effect
on the solid polymer electrolyte becomes weak. If the porosity
is too low, the resistance of the composite membrane becomes
high and if it is too high, the strength of the porous substrate
itself generally becomes weak and the reinforcing effect is
reduced.
From the viewpoint of the heat resistance and the
reinforcing effect of the physical strength, the
above-mentioned porous substrate is preferably a substrate
comprising an aliphatic based polymer, an aromatic based
polymer, or a fluorine-containing polymer.
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Next, a fuel cell of the present invention will be
described. As the fuel cell using the polymer electrolyte
membrane, while there are, for example a solid polymer fuel cell
using hydrogen gas as fuel and a direct methanol solid polymer
fuel cell to which methanol as fuel is directly supplied, the
copolymer of the present invention may be used preferably for
both.
Examples of the fuel cell obtained according to the
present invention may be those using the copolymer of the
present invention for a polymer electrolyte membrane and/or a
polymer electrolyte composite membrane and those using the
polymer electrolyte of the present invention for a polymer
electrolyte in a catalyst layer.
The fuel cell using the copolymer of the present invention
for a polymer electrolyte membrane or a polymer electrolyte
composite membrane can be produced by conjugating a catalyst
and a gas diffusion layer on both sides of the polymer
electrolyte membrane or the polymer electrolyte composite
membrane. Conventionally known materials can be used for the
gas diffusion layer and a porous carbon woven fabric, carbon
non-woven fabric, or carbon paper is preferable for efficiently
transporting a raw material gas to the catalyst.
Herein, the catalyst is not particularly limited as far
as it can activate redox reaction of hydrogen or oxygen and
conventionally known ones may be used, however, fine particles
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of platinum are preferably used. Fine particles of platinum
are often preferably used with being supported on particulate
or fibrous carbon such as activated carbon and graphite. In
addition, a paste obtained by mixing platinum supported on
carbon with an alcohol solution of a perfluoroalkylsulfonic
acid resin as a polymer electrolyte is applied to a gas diffusion
layer, a polymer electrolyte membrane, or a polymer electrolyte
composite membrane and dried to obtain the catalyst layer.
Specific methods may be conventionally known method such as
those described in, for example, J. Electrochem. Soc.:
Electrochemical Science and Technology, 1988, 135(9), 2209.
Examples of the fuel cell using the copolymer of the
present invention as the polymer electrolyte in the catalyst
layer may include those using the copolymer of the present
invention in place of a perfluoroalkylsulfonic acid resin
composing the above-mentioned catalyst layer. When the
catalyst layer containing the copolymer of the present
invention is used, the polymer electrolyte membrane is not
limited to the membrane using the copolymer of the present
invention and conventionally known polymer electrolyte
membranes may be used.
When the catalyst layer using the copolymer of the present
invention is obtained, a solvent to be used for preparing a
catalyst paste is arbitrary and not particularly limited;
however it is desired that the solvent be capable of dissolving
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components besides the solvents composing the catalyst paste,
or dispersing the components evenly in molecular level, or
forming agglomerates in nano- to micro-level and dispersing the
agglomerates. The solvent may be a single solvent or a mixture
of a plurality of solvents and those exemplified as the solvents
usable when a membrane of the copolymer of the present invention
is formed, may be used.
Other components composing the catalyst paste are
arbitrary and not particularly limited; however the components
may sometimes contain a water-repelling material such as PTFE
to improve the water-repellency of the catalyst layer, a pore
forming material such as calcium carbonate to improve the gas
diffusion property of the catalyst layer, a stabilizer such as
a metal oxide and a polymer having phosphonic acid group to
improve the durability.
The catalyst paste is obtained by mixing the
above-mentioned polymer electrolyte, a catalytic material
and/or a conductive material supporting a catalytic material
on a surface, a solvent, and other components by a
conventionally known method. The mixing method may include an
ultrasonic dispersion apparatus, a homogenizer, a ball mill,
a planetary ball mill, and a sand mill.
A method of directly applying the catalyst paste is not
particularly limited and an already known method such as a die
coater, a screen printing, a spraying method, and an ink jet
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method can be employed; however a spraying method is preferable
since its operation is industrially convenient.
As the spraying method of the catalyst paste, the
apparatus and method disclosed in, for example, Japanese
Unexamined Patent Publication No. 2004-89976 can be
specifically illustrated and the method can be carried out using
them. That is, a polymer electrolyte is set on a stage and a
catalyst ink is directly applied to the polymer electrolyte.
In a spraying method, the catalyst ink is sprayed in particle
state out of a jetting outlet and is adhered on the polymer
electrolyte. It is desired that the stage should be heated to
remove the solvent quickly after application and the
temperature is preferably 50 C to 150 C. If the temperature is
within the above-mentioned range, the solvent of the catalyst
ink is easy to be removed quickly and the tendency of thermal
damages on the polymer electrolyte membrane is small and
therefore, it is preferable. As described, the solvent is
removed by heating the stage successively to the application
by the spraying method to produce the catalyst layer on the
polymer electrolyte membrane. For the purpose of removing the
solvent completely, the membrane on which the catalyst layer
is forrned may be put in such as a heated oven and dried or, if
necessary, drying in a vacuum can be carried out. To remove
the solvent more quickly, a preferable solvent composing the
catalyst paste is a solvent having a boiling point of 150 C or
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lower and water, alcohol based solvents such as methanol and
ethanol, ether based solvents such as diethyl ether and
tetrahydrofuran, and solvent mixture thereof may be used and
the copolymer of the present invention is also excellent in that
it is easy to dissolve in these solvents. The catalyst paste
may be sprayed a plurality of times and respective layers
obtained by spraying may be coated over on the polymer
electrolyte membrane to form a multi-layer coating.
Hereinafter, the invention will be described with
reference to Examples, however it is not intended at all that
the invention be limited to the illustrated Examples.
Measurement of molecular weight:
The number average molecular weight (Mn) based on polystyrene
standard calibration, was measured by gel permeation
chromatography (GPC) in the following conditions.
GPC measurement apparatus: HLC-8220 GPC, manufactured by TOSOH
Co., Ltd.
Column: TSKgel GHMHR-M, manufactured by Showa Denko K.K.
Column temperature: 40 C
mobile phase solvent: DMAc (adding LiBr in a
concentration of 10 mmol/dm3)
solvent flow rate: 0.5 mL/min
Measurement of proton conductivity:
Measured by an AC method at a temperature of 80 C and
relative humidity of 90%.
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Measurement of ion exchange capacity:
Measured by a titration method.
Measurement of water absorption ratio:
After a dried polymer electrolyte membrane was weighed
and immersed in deionized water at 100 C for 2 hours, the water
absorption ratio was calculated from the increase of the
membrane weight amount and the ratio to the above-mentioned
dried membrane was calculated.
Example 1
Production of copolymer A
Polymerization was carried out by charging a 200 mL
separable flask equipped with a Dean-Stark apparatus with 3.50
g (15.33 mmol) of potassium hydroquinonesulfonate, 6.29 g
(33.76 mmol ) of 4,4' -dihydroxybiphenyl, and 7.36 g (53 . 24 mmol)
of potassium carbonate and carrying out azeotropic dehydration
in 121 mL of dimethyl sulfoxide and 70 mL of toluene under argon
atmosphere at bath temperature of 150 C (inner temperature of
130 5 C ) for 1. 5 hours. After 1. 5 hours, toluene was removed
to the outside of the system and the reaction product was
spontaneously cooled to room temperature. Thereafter, 9.03 g
(18.40 mmol) of 3,3'-sulfonylbis(potassium
6-fluorobenzenesulfonate) and 7.80 g (30.69 mmol) of
4,4'-difluorodiphenylsulfone were added to the reaction
product and further reaction was carried out at an inner
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temperature of 150 C for 11 hours. The reaction was traced by
GPC measurement. On completion of the reaction, the reaction
solution was spontaneously cooled to 80 C and dropwise added
to 3 L of an aqueous 2 M hydrochloric acid solution. The
precipitated white polymer was filtered and washed until pH of
the washing filtrate became about 7 and thereafter, a step of
treatment with water at 80 C for 2 hours was repeated twice.
The resulting polymer was dried by an oven (800C) to obtain 20 . 86
g (yield 92%) of the following copolymer A. Thereafter, the
following dried polymer was dissolved in N-methylpyrrolidone
and then filtered to obtain a solvent solution in a
concentration of 18oby weight. Then, the solution was applied
to a glass substrate and N-methylpyrrolidone was removed at 80 C
in a fully evacuated oven for about 5 hours. Thereafter, a step
of treatment with 2N hydrochloric acid for 1 hour was repeated
twice and washed with flowing water (deionized water) for 8
hours to obtain a polymer electrolyte membrane. A thickness
of the membrane was 33 pm.
Copolymer A
The copolymer A was a polymer having the following
structural units.
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0
0 0 (A-a)
~
i&&O~ (A-b)
3 (A-c)
0
HO3S SO3H
' O~ (A-d)
SO3H
The molar ratio of the respective structural units(A-a),(A-b),
(A-c), and (A-d) calculated from the charged amounts to the
total of the above-mentioned structural units: (A-a) : (A-b) (A-c) : (A-d) =
2.00 : 2.20 : 1.20 : 1.00
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 2.30 meq/g
Mn 8.10x104
Actually measured value of ion exchange capacity: 2.10 meq/g
Membrane production: NMP solution cast method: membrane
thickness 33 pm
Proton conductivity: 1.56X10-1 S/cm
Water absorption ratio: 169%
Example 2
Production of copolymer B
Polymerization was carried out by charging a 200 mL
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separable flask equipped with a Dean-Stark apparatus with 3.50
g (15.33 mmol) of potassium hydroquinonesulfonate, 7.87 g
(42. 25 mmol) of 4, 4' -dihydroxybiphenyl, and 8. 65 g (62 . 57 mmol)
of potassium carbonate and carrying out azeotropic dehydration
in 138 mL of dimethyl sulfoxide and 70 mL of toluene under argon
atmosphere at bath temperature of 150 C (inner temperature of
130 5 C ) for 1. 5 hours. After 1. 5 hours, toluene was removed
to the outside of the system and the reaction product was
spontaneously cooled to room temperature. Thereafter, 9.03 g
(18.40 mmol) of 3,3'-sulfonylbis(potassium
6-fluorobenzenesulfonate) and 9.96 g (39.18 mmol) of
4,4'-difluorodiphenylsulfone were added to the reaction
product and further reaction was carried out at an inner
temperature of 150 C for 5 hours. The reaction was traced by
GPC measurement. On completion of the reaction, the reaction
solution was spontaneously cooled to 80 C and dropwise added
to 3 L of an aqueous 2 M hydrochloric acid solution. The
precipitated white polymer was filtered and washed until pH of
the washing filtrate became about 7 and thereafter, a step of
treatment with water at 80 C for 2 hours was repeated twice.
The resulting polymer was dried by an oven (800C) to obtain 23 . 62
g (yield 91%) of the following copolymer B. The membrane
production was carried out according to Example 1.
Copolymer B
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The copolymer B was a polymer having the following
structural units.
!~ ~~ \ S l \ p (S-a)
O
/ \ / \ p (8-b)
s0I \ o~ (B-c)
o ~
Ho~s SoOH
o
(s-d)
H
11\13
The molar ratio of the respective structural units(B-a),(B-b),
(B-c), and (B-d) calculated from the charged amounts to the
total of the above-mentioned structural units: (B-a) : (B-b) (B-c) : (B-d) =
2.56 : 2.76 : 1.20 : 1.00
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 2.00 meq/g
Mn 8.20x104
Actually measured value of ion exchange capacity: 1.80 meq/g
Membrane production: NMP solution cast method: membrane
thickness 26 pm
Proton conductivity: 8.84x10- 2 S/cm
Water absorption ratio: 94%
Comparative Example 1
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Production of copolymer C
Polymerization was carried out by charging a 200 mL
separable flask equipped with a Dean-Stark apparatus with 6.18
g (27.09 mmol) of potassium hydroquinonesulfonate, 10.00 g
(39.33 mmol) of 4,4'-difluorodiphenylsulfone, 2.28 g (12.25
mmol) of 4,4'-dihydroxybiphenyl, and 5.98 g (43.26 mmol) of
potassium carbonate and carrying out azeotropic dehydration in
74 mL of dimethyl sulfoxide and 40 mL of toluene under argon
atmosphere at bath temperature of 150 C (inner temperature of
130 5 C) for 3 hours. After 3 hours, toluene was removed to
the outside of the system and reaction was carried out at an
inner temperature of 150 C for 12 hours. The reaction was
traced by GPC measurement. On completion of the reaction, the
reaction solution was spontaneously cooled to 80 C and dropwise
added to 3 L of an aqueous 2 M hydrochloric acid solution. The
precipitated white polymer was filtered and washed until pH of
the washing filtrate became about 7 and thereafter, a step of
treatment with water at 80 C for 2 hours was repeated twice.
The resulting polymer was dried by an oven (800C) to obtain 14 . 67
g (yield 92%) of the following copolymer C. The membrane
production was carried out according to Example 1.
Copolymer C
The copolymer C was a polymer having the following
structural units.
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0
~ ~ S F ~ O~ (C-a)
O
~0~0~ (C-b)
O-}- (C-d)
///
SO3H
The molar ratio of the respective structural units(C-a),(C-b),
and (C-c) calculated from the charged amounts to the total of
the above-mentioned structural units: (C-a) : (C-b) : (C-c) _
1.45 : 0.45 : 1.00
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 1.71 meq/g
Mn 4.06x104
Actually measured value of ion exchange capacity: 1.56 meq/g
Membrane production: NMP solution cast method: membrane
thickness 54 }im
Proton conductivity: 4.60x10-2 S/cm
Water absorption ratio: 302%
Comparative Example 2
Production of copolymer D
Polymerization was carried out by charging a 500 mL
separable flask equipped with a Dean-Stark apparatus with 12.74
g(50.10mmol)of 4,4'-difluorodiphenylsulfone,18.62g(100.00
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mmol) of 4,4'-dihydroxybiphenyl, and 25.08 g (50.00 mmol) of
3,3' -sulfonyl bis(potassium 6-fluorobenzenesulfonate), 15.20
g (110.00 mmol) of potassium carbonate and carrying out
azeotropic dehydration in 160 mL of N-methyl-2-pyrrolidone and
80 mL of toluene under argon atmosphere at inner temperature
of 140 C for 5 hours. After 3 hours, toluene was removed to
the outside of the system and reaction was carried out at an
inner temperature of 170 C for 8 hours. The reaction was traced
by GPC measurement. On completion of the reaction, the reaction
solution was spontaneously cooled to room temperature and
dropwise added to 500 mL of an aqueous 2 M hydrochloric acid
solution. Afterthe precipitated white polymer was washed with
water, the polymer was pulverized to powder and then was washed
again with water until pH of the washing water became about 7.
Thereafter, a step of treatment with water at 95 C for 2 hours
was repeated twice. The resulting polymer was dried in reduced
pressure by an oven (60 C) to obtain 45.31 g (yield 93%) of the
following polymer. The membrane production was carried out
according to Example 1.
Copolymer D
The copolymer D was a polymer having the following
structural units.
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S 0 (D-a)
HO3S SO3H
(D-b)
(D-c)
O c
The molar ratio of the respective structural units (D-a) ,(D-b),
and (D-c) calculated from the charged amounts to the total of
the above-mentioned structural units: ( D-a ) : ( D-b ) : ( D-c )
1.00 : 2.00 : 1.02
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 2.08 meq/g
Mn 7.70x104
Actually measured value of ion exchange capacity: 1.97 meq/g
Membrane production: NMP solution cast method: membrane
thickness 26 pm
Proton conductivity: 0.97X10-1 S/cm
Water absorption ratio: 460%
Example 3
Production of copolymer E
Polymerization was carried out by charging a 200 mL
separable flask equipped with a Dean-Stark tube with 3.00 g
(13.14 mmol) of potassium hydroquinonesulfonate, 8.31 g (24.57
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mol) of 4,4'-dihydroxy-3,3'-diphenylbiphenyl, and 5.42 g
(39.21 mmol) of potassium carbonate and carrying out azeotropic
dehydration in 105 mL of dimethyl sulfoxide and 60 mL of toluene
under argon atmosphere at bath temperature of 150 C (inner
temperature of 130 5 C ) for 2 hours. After 2 hours, toluene
was removed to the outside of the system and the reaction product
was spontaneously cooled to room temperature. Thereafter,
7.17 g (15.77 mmol) of
4,4'-difluorobenzophenone-3,3'-dipotassium disulfonate and
5. 57 g (21. 90 mmol) of 4, 4' -difluorodiphenylsulfone were added
to the reaction product and further reaction was carried out
at an inner temperature of 150 C for 25 hours. The reaction
was traced by GPC measurement. On completion of the reaction,
the reaction solution was spontaneously cooled to 80 C and
dropwise added to 3 L of an aqueous 2 M hydrochloric acid solution.
The precipitated white polymer was filtered and washed until
pH of the washing filtrate became about 7 and thereafter, a step
of treatment with water at 80 C for 2 hours was repeated twice.
The resulting polymer was dried by an oven (800C) to obtain 18 . 96
g (yield 91%) of the following copolymer E. Thereafter, the
membrane production was carried out according to Example 1.
Copolymer E
The copolymer E was a polymer having the following
structural units.
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/ ~ s 0 UY
(E-a)
O (E-b)
C 0~ (E-c)
HOgS SU3H
(E-d)
SO3H
The molar ratio of the respective structural units(E-a),(E-b),
(E-c), and (E-d) calculated from the charged amounts to the
above-mentioned structural units: (E-a) : (E-b) : (E-c) : (E-d)
= 1.67 : 1.87 : 1.20 : 1.00
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 2.00 meq/g
Mn 6.2x104
Actually measured value of ion exchange capacity: 1.90 meq/g
Membrane production: NMP solution cast method: membrane
thickness 33 um
Proton conductivity: 0.95X10-1 S/cm
Water absorption ratio: 88$
Example 4
Production of copolymer F
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Polymerization was carried out by charging a 200 mL
separable flask equipped with a Dean-Stark apparatus with 3.00
g (13.14 mmol) of potassium hydroquinonesulfonate, 5.79 g
(17.11 mmol) of 4,4'-dihydroxy-3,3'-diphenylbiphenyl, 3.91 g
(17.11 mmol) of 2,2'-bis(4-hydroxyphenyl)propane, 7.74 g
(15.77 mmol) of 3,3'-sulfonyl bis(potassium
6-fluorobenzenesulfonate), 8.04 g (31.60 mmol) of
4,4'-difluorodiphenylsulfone, and 6.87 g (49.74 mmol) of
potassium carbonate and carrying out azeotropic dehydration in
114 mL of dimethyl sulfoxide and 40 mL of toluene under argon
atmosphere at bath temperature of 150 C (inner temperature of
130 5 C ) for 2 hours. After 2 hours, toluene was removed to
the outside of the system and the reaction was further carried
out at 150 C for 3 hours. The reaction was traced by GPC
measurement. On completion of the reaction, the reaction
solution was spontaneously cooled to 80 C and dropwise added
to 1 L of an aqueous 2 M hydrochloric acid solution. The
precipitated polymer was filtered and washed until pH of the
washing filtrate became about 7 and thereafter, a step of
treatment with water at 80 C for 2 hours was repeated twice.
The resulting polymer was dried by an oven (800C) to obtain 23 . 31
g (yield 87%) of the following copolymer F. The membrane
production was carried out according to Example 1.
Copolymer F
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The copolymer F was a polymer having the following
structural units.
r~ / p/
~' (F-a)
-O
ic+0_0 (F b)
0/
(F-c)
\ / / \
~ \ S / \ 0 (F-d)
0
HO3S S03H
0~ (F-e)
SO3H
The molar ratio of the respective structural units(F-a),(F-b),
(F-c), (F-d),and (F-e) calculated from the charged amounts to
the total of the above-mentioned structural units: (F-a) :
(F-b) : (F-c) : (F-d) : (F-e) = 2.40 : 1.30 : 1.30 : 1.20 : 1.00
The ion exchange capacity calculated from the molar ratio of
the above-mentioned structural units: 1.80 meq/g
Mn 3.3x104
Actually measured value of ion exchange capacity: 1.62 meq/g
Membrane production: NMP solution cast method: membrane
thickness 60 pm
Proton conductivity: 0.62X10'1 S/cm
Water absorption ratio: 104%
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Example 5
[Production of catalyst paste]
A uniform copolymer A solution (concentration of
copolymer A: 5% by weight) was produced by mixing 95 g of a
solvent mixture of water : ethanol = 1 : 9 (ratio by weight)
and 5 g of the copolymer A obtained in Example 1. Separately,
0.64 g of platinum-supporting carbon (SA 50 BK, manufactured
by N.E. CHEMCAT CORPORATION; platinum support amount 50% by
weight) was charged to 11 mL of ethanol and further 1.05 g of
the previously prepared copolymer A solution was added to the
mixture. After the obtained mixture was treated for 1 hour by
ultrasonic treatment, it was stirred by a stirrer for 6 hours
to obtain a catalyst ink A.
[Production of polymer electrolyte membrane]
Referring to Japanese Unexamined Patent Publication No.
2005-139432, a polymer electrolyte membrane comprising the
block copolymer type polymer electrolyte represented by the
following formula was obtained. Specifically, a first polymer
compound having ion exchange groups and a second polymer
compound having substantially no ion exchange group were
respectively synthesized as described below and they were
f urther subjected to coupling to synthesize the block copolymer
type polymer electrolyte.
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(Synthesis of first polymer compound)
To a flask provided with an azeotropic distillation
apparatus was added 283.68 g of
4,4'-difluorodiphenylsulfone-3,3'-dipotassium disulfonate,
120.00 g of Potassium 2,5-dihydroxybenzenesulfonate, 1778 g of
DMSO, and 279 g of toluene under argon atmosphere and while they
were being stirred at room temperature, bubbling of argon gas
was carried out for 1 hour.
Thereafter, 76.29 g of potassium carbonate was added to
the obtained mixture and the mixture was heated and stirred at
140 C for azeotropic dehydration. Thereafter, while toluene
was removed by distillation, heating was continued to obtain
a DMSO solution of the first polymer compound. The total
heating time was 16 hours. The obtained solution was
spontaneously cooled at room temperature.
The first polymer compound had Mn of 3.0X104.
(Synthesis of second polymer compound)
To a flask provided with an azeotropic distillation
apparatus was added 247 . 55 g of 4, 4' -difluorodiphenylsulfone,
164.44 g of 2,6-dihydroxynaphthalene, 902 g of DMSO, 902 g of
NMP, and 310 g of toluene under argon atmosphere and while they
were being stirred at room temperature, bubbling of argon gas
was carried out for 1 hour.
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Thereafter, 156.09 g of potassium carbonate was added to
the obtained mixture and the mixture was heated and stirred at
100 C for vacuum azeotropic dehydration. Thereafter, toluene
was removed by distillation after 17 hours and thereafter,
heating was further continued at 100 C . The total heating time
was 19 hours. The obtained solution was spontaneously cooled
at room temperature to obtain a NMP/DMSP mixed solution of the
second polymer compound.
The second polymer compound had Mn of 2.7X104.
(Synthesis of block copolymer)
While the obtained NMP/DMSP mixed solution of the second
polymer compound was being stirred, all of the above-mentioned
DMSO solution of the first polymer compound, 610 g of DMSO, and
1790 g of NMP were added to the mixture solution and block
copolymerization reaction was carried out at 150 C for 39 hours.
The obtained reaction solution was dropwise added to a
large quantity of 2N hydrochloric acid and immersed for 1 hour.
Thereafter, the precipitate produced was separated by
filtration and again immersed in 2N hydrochloric acid for 1 hour.
The obtained precipitate was separated by filtration and washed
with water and then immersed in a large quantity of hot water
at 95 C for 1 hour. After a solid was separated by filtration,
the solid was again immersed in a large quantity of hot water
at 95 C for 1 hour. After the solid was separated by filtration,
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the solid was dried overnight at 80 C to obtain a block
copolymer.
Membrane production was carried out in the same manner
as Example 1.
[Obtained block copolymer type polymer electrolyte]
O Q
S O n1 HO3 Q Q SO3H s03H m1
In the formula, ni and ml denote the average
polymerization degree of the respective blocks of the block
copolymer type polymer electrolyte.
Mn 7.9x104.
Actually measured value of ion exchange capacity: 1.94 meq/g
Membrane production: NMP solution cast method: membrane
thickness: 27 pm
Proton conductivity: 2.37X10-1 S/cm
Water absorption ratio: 115%
Being calculated from charging, nl = 36.2 and ml =10.5.
[MEA]
The polymer electrolyte membrane comprising the block
copolymer type polymer electrolyte obtained in the
above-mentioned manner was cut out in a square shape and set
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on a heating stage and the catalyst ink A was applied to a region
of 5.2 cm square in the center part of the main face of the
membrane by a spraying method. The distance from the outlet
to the membrane was 5 cm and the stage temperature was set at
76 C. After the application, the membrane was left for 3
minutes on the stage to remove the solvent and form a catalyst
layer. The polymer electrolyte membrane provided with the
catalyst layer on one face in the above-mentioned manner was
turned upside down and set on the heating stage and again a
catalyst layer was formed using the catalyst ink A also on the
other face in the same manner as the former catalyst layer to
obtain a membrane-electrode assembly. The platinum amount in
the catalyst layers calculated from the weight composition of
the catalyst layers and the catalyst layer weight was 0. 6 mg/cm2
for each face.
[Cell assembly for fuel cell evaluation]
A fuel cell was produced using a commercially available
JARI standard cell. That is, a carbon cloth as a gas diffusion
layer and a separator made of carbon having a groove formed by
cutting processing for a gas channel were arranged in both
catalyst layers of the membrane-electrode assembly obtained in
the above-mentioned manner and current collectors and end
plates were successively arranged further outside thereof and
the arranged parts were fastened by bolts to assemble a fuel
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cell with an effective membrane surface area of 25 cm2.
[Fuel cell evaluation]
While the obtained fuel cells was kept at 80 C, humidified
hydrogen and humidified air were supplied to an anode and a
cathode, respectively. At that time, the back-pressure at the
gas outlet of the cell was adjusted to be 0.1 MPaG. The
humidification of the respective raw material gases was carried
out by leading the gases to bubblers and the water temperature
of the bubbler for hydrogen was set to be 45 C and the water
temperature of the bubbler for air was set to be 55 C.
Herein, the gas flow rate of hydrogen was set to be 529
mL/min and the gas flow rate of air was set to be 1665 mL/min.
The current density at 0.2 V of the cell potential was 1. 5 A/cm.
The cell potential at 0.5 A/cm of the current density was 0.59
V.
Comparative Example 3
(Synthesis of copolymer G)
A polymer electrolyte membrane comprising a copolymer G
represented by the following formula was obtained in the same
manner as Example 3 of Japanese Unexamined Patent Publication
No. 10-021943.
Herein, nl and ml denote the molar ratio of the respective
structural units of the random copolymer type polymer
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electrolyte.
[Copolymer G]
o
/ \ S / \ p random 0
O n2 ~ ~sO~H so~-~ m2
Mn 4.5xl04.
Actually measured value of ion exchange capacity: 1.11 meq/g
Membrane production: DMAc solution cast method: membrane
thickness: 20 pm
Proton conductivity: 7.81X10-3 S/cm
Water absorption ratio: 41%
m2/(n2 + m2) = 0.14
[Production of catalyst paste]
A uniform copolymer B solution (concentration of
copolymer B: 5% by weight) was produced by mixing 9.5 g of NMP
and 0.5 g of the copolymer G. Separately, 0.64 g of
platinum-supporting carbon (SA 50 BK, manufactured by N.E.
CHEMCAT CORPORATION; platinum support amount 50% by weight) was
charged to 11 mL of ethanol and further 1. 05 g of the previously
prepared copolymer A solution was added to the mixture. After
the obtained mixture was treated for 1 hour by ultrasonic
treatment, it was stirred by a stirrer for 6 hours to obtain
a catalyst ink B.
58
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The polymer electrolyte membrane comprising the block
copolymer type polymer electrolyte used in Example 5 was used.
[MEA]
A carbon cloth to be a gas diffusion layer was cut out
in a square shape and set on a heating stage and the catalyst
ink B was applied to a region of 5.2 cm square in the center
part of the main face of the carbon cloth by a spraying method.
The distance from the outlet to the carbon cloth was 5 cm and
the stage temperature was set at 76 C. After the application,
the cloth was left for 3 minutes on the stage to remove the
solvent and form a catalyst layer. Two sheets of a carbon cloth
on which the catalyst layer was formed in the above-mentioned
manner were produced. The platinum amount in the catalyst
layers calculated from the weight composition of the catalyst
layers and the catalyst layer weight was 0.6 mg/cm2 for each
face. Thereafter, to remove NMP remaining in the carbon cloth,
the resulting carbon cloth sheets were immersed in 1 N
hydrochloric acid and successively washed with water for1hour.
An electrolyte membrane was sandwiched with these two carbon
cloth sheets from which NMP was removed and the product was
pressed at 120 C and 10 kgf/cm2 for 15 minutes to complete a
membrane-electrode assembly.
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[Cell assembly for fuel cell evaluation]
A fuel cell was produced using a commercially available
JARI standard cell. That is, a separator made of carbon having
a groove formed by cutting processing for a gas channel was
arranged in both gas diffusion layers of the membrane-electrode
assembly obtained in the above-mentioned manner and current
collectors and end plates were successively arranged further
outside thereof and the arranged parts were fastened by bolts
to assemble a fuel cell with an effective membrane surface area
of 25 cmz .
[Fuel cell evaluation]
While the obtained fuel cells was kept at 80 C, humidified
hydrogen and humidified air were supplied to an anode and a
cathode, respectively. At that time, the back-pressure at the
gas outlet of the cell was adjusted to be 0.1 MPaG. The
humidification of the respective raw material gases was carried
out by leading the gases to bubblers and the water temperature
of the bubbler for hydrogen was set to be 45 C and the water
temperature of the bubbler for air was set to be 55 C.
Herein, the gas flow rate of hydrogen was set to be 529
mL/min and the gas flow rate of air was set to be 1665 mL/min.
The current density at 0.2 V of the cell potential was 1.1 A/cm.
The cell potential at 0.5 A/cm of the current density was 0.44
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V.
The copolymer of the present invention shows excellent
capabilities for properties such as water-proofness, membrane
formability, and proton conductivity as a polymer electrolyte,
particularly a proton conductive membrane of a fuel cell. It
is particularly excellent in water-proofness.
Further, when the copolymer is used as a proton conductive
membrane for a fuel cell, since it shows high power generation
characteristics, the copolymer of the present invention is
industrially advantageous as a polymer electrolyte.
61
