JP4841194B2 - Polymer electrolyte membrane for fuel cells - Google Patents

Description

  The present invention relates to a fuel cell using a polymer electrolyte, and more particularly to an electrolyte membrane for a direct methanol fuel cell.

Materials used as fuel cell electrolytes include inorganic materials with high ion conductivity and polymer materials that are easy to mold, but the current mainstream is perfluorocarbon sulfone with high ion conductivity among polymer materials. It is an acid polymer. The amount of ion exchange groups (sulfonic acid groups in the case of perfluorocarbon sulfonic acid) in the polymer is an important factor that determines ion conductivity, and this is equivalent to the ion exchange group equivalent (ion exchange groups per gram of polymer weight). Equivalent) is often shown. The larger the ion exchange group equivalent, the greater the amount of ion exchange groups, and the ionic conductivity can be improved. However, it becomes easier to dissolve in the water generated by the electrode reaction, and the membrane tends to deteriorate. On the other hand, when the ion exchange group equivalent is small, the water resistance is improved, but the ionic conductivity is lowered and cannot be used as an electrolyte membrane.
In order to overcome such problems, Patent Document 1 proposes an electrolyte in which membranes having different ion exchange group equivalents are joined. However, perfluorocarbon sulfonic acid has the disadvantage of being inferior in heat resistance under the operating conditions of the fuel cell. Furthermore, although the fuel cell is shifting directly from the hydrogen gas type (PEMFC) to the methanol type, perfluorocarbon sulfonic acid has a drawback that it easily permeates methanol.

  On the other hand, the development of aromatic main chain polymer electrolytes that have overcome heat resistance has become active. This is a polymer electrolyte in which an acid group such as a sulfonic acid group is introduced into a heat-resistant polymer such as polyamide, polyimide, polyphenylene oxide, polyphenylene sulfide, or polybenzimidazole. The heat resistance is considerably improved with respect to perfluorocarbon sulfonic acid, and the methanol permeability is relatively good. Patent Document 2 discloses an electrolyte membrane using a polybenzimidazole laminated film using the same technique as Patent Document 1. However, in the conventional aromatic main chain polymer electrolysis, the aromatic ring of the main chain is oxidized by radicals generated under the operating conditions of the fuel cell, so that the durability in long-time operation is not sufficient.

JP-T-2001-507166 JP 2001-167775 A

  An object of the present invention is to provide a novel membrane having important performance as an electrolyte membrane for a fuel cell, particularly an electrolyte membrane for a direct methanol fuel cell, such as ion conductivity, oxidation resistance, and methanol permeability. And

The present inventors disclose the following means as a solution to the above problem.
1. At least the following general formula (1) a film containing a polymer electrolyte having a repeating unit (A) represented by the sulfonic acid group equivalent of membrane interior region adjacent to the membrane both surfaces, adjoining said region fuel cell electrolyte membrane, wherein less than sulfonic acid group equivalent of membrane surface to.

(Y represents a (k + 2) -valent aromatic residue, and P represents —CO—, —O—, —S—, —SO—, —SO ₂ —, —CONH—, —C (CF ₃ ) ₂ —. , A linking group selected from single bonds, k is an integer of 1 to 2 , and the side chain moiety Z in the formula is represented by the following general formula (2).
^{Z = - (X 1 Ar 1} (B 1)) - (X 2 Ar 2 (B 2)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar ⁿ ) (2)
B ^{1 to} B ^n-1 in the general formula (2) mean a branched chain in the side chain portion Z, and are represented by the following formula.
B ¹ = - ^{[(X 2 Ar 2 (B 2} )) - (X 3 Ar 3 (B 3)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X ⁿ Ar ⁿ )] _f
B ² = - ^{[(X 3 Ar 3 (B 3} )) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar n) ] _f
・
・
・
B ^n-1 = − [X ⁿ Ar ⁿ ] _f
In said general formula (2), n is an integer of 2-5 each independently,
f is each independently an integer of 0 to 2 , at least one f is 1 or 2 ,
Ar ^{1 to} Ar ⁿ are each independently an aromatic residue,
X ^{1 to} X ⁿ are each independently —CO—, —CONH—, — (CF ₂ ) _p — (p is an integer of 1 to 10), —C (CF ₃ ) ₂ —, —COO—, —SO—. , —SO ₂ —. Z has a number exceeding 1.0 of the —SO ₃ H group. )

2. 2. The fuel cell electrolyte membrane according to item 1, wherein f is 0 or 1, and at least one f is 1.
3 . And both surfaces of the film, towards the inside from each of the both surfaces sandwiched 5μm containing surface, in the region of the width 5μm from both surfaces, there is an interface that sulfonic acid group equivalent is reduced discontinuously, by the interface and divided into a surface layer and an inner layer, a sulfonic acid group equivalent of the inner layer, is 80% or less of the sulfonic acid group equivalent of adjacent membrane surface layer, the item 1 or 2 for a fuel cell electrolyte according to film.
4 . Sulfonic acid group equivalent sites entering the 5 [mu] m inside the thickness direction from both surfaces of the film becomes 80% or less of the sulfonic acid group equivalent surface region of the film from the site at the position of 5 [mu] m, the item 1 Or an electrolyte membrane for a fuel cell as described in 2 ;
5 . Electrolyte sulfonic acid group equivalent of the entire film is 0.3 meq / g or more, the item 1 electrolyte membrane according to any one of the 4.
6 . From both the membrane surface, sulfonic acid group equivalent of the polymer electrolyte in the region of up to 1μm towards the inside is less than 5 meq / g, a fuel cell electrolyte membrane according to any one of items 1-5.

  The electrolyte membrane of the present invention has high ion conductivity, and has all of heat resistance, oxidation resistance, and electrode durability in a fuel cell use environment.

The present invention will be specifically described below.
<Polymer electrolyte>
The polymer electrolyte used for the electrolyte membrane of the present invention has a repeating unit (A) represented by the following general formula (1).

In the general formula (1), k is usually an integer of 1 to 4, and preferably 1 or 2. In the general formula (1), Y is a (k + 2) -valent aromatic residue, for example, a trivalent aromatic residue represented by the following formula (3), a tetravalent aromatic represented by the following formula (4) Group residues, pentavalent aromatic residues represented by the following formula (5), and the like. The hydrogen atom of these aromatic residues is an alkyl group, a halogen atom, a halogenated alkyl group, an aryl group, a halogenated aryl group, —CN, —NO ₂ , —COR, —COOR (where R is a hydrogen atom, an alkyl group, a halogen atom, alkyl group, selected from aryl group), -. CONRR '(R ' is the same as _{R), -. SO 3 R} , -SOR, may be substituted by -SO ₂ R, F, par It is preferable that an electron withdrawing group such as fluoroalkyl, —CN, —NO ₂ , —COR, —COOR, —CONRR ′, —SO ₃ R, —SOR, and —SO ₂ R is substituted.

The divalent group Q in the general formulas (3) to (5) is —CO—, —COO—, —O—, —S—, —SO—, —SO ₂ —, —CCR ¹ ₂ — (R ¹ Is selected from a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, and an aryl group) and a single bond, and preferably selected from —CO—, —O—, —S—, and —SO ₂ —.
In the general formula (1), P is a linkage selected from —CO—, —O—, —S—, —SO—, —SO ₂ —, —CONH—, —C (CF ₃ ) ₂ —, and a single bond. A linking group selected from —CO—, —O—, —S—, —SO ₂ —, —C (CF ₃ ) ₂ —, and more preferably —CO—, —O—. , —S—, —SO ₂ —.
The side chain portion Z in the general formula (1) is represented by the general formula (2).
^{Z = - (X 1 Ar 1} (B 1)) - (X 2 Ar 2 (B 2)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar ⁿ ) (2)
^{B 1 ~B n-1} in the general formula (2) in means a branched chain in the side chain moiety Z, is expressed by the following equation.
B ¹ = - ^{[(X 2 Ar 2 (B 2} )) - (X 3 Ar 3 (B 3)) - ··· - (X n-1 A rn-1 (B n-1)) - (X ⁿ Ar ⁿ )] _f
B ² = - ^{[(X 3 Ar 3 (B 3} )) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar n) ] _f
・
・
・
B ⁿ⁻¹ = − [X ⁿ Ar ⁿ ] _f
In the general formula (2), each n independently represents an integer selected from 2 to 5, preferably selected from 2 to 4, and more preferably selected from 2 to 3. f represents an integer independently selected from 0 to 5, preferably from 0 to 2, and at least one f is 1 or 2, more preferably from 0 to 1, and at least One f is 1.
In the general formula (2), when f is 1 or more, the side chain represented by the general formula (2) has a branched structure in the aromatic residues Ar ^{1 to} Ar ^n-1 . Each branched chain may have a different chain length and branched structure. That is, the side chain represented by the general formula (2) of the present invention can have a structure represented by the following formula (6), for example.

Ar ^{1 to} Ar ^n-1 in the general formula (2) represent an (f + 2) -valent aromatic residue, for example, a divalent aromatic residue represented by the following formula (7), A trivalent aromatic residue, a tetravalent aromatic residue represented by the general formula (4), a pentavalent aromatic residue represented by the general formula (5), and the like. The hydrogen atom of these aromatic residues is an alkyl group, a halogen atom, a halogenated alkyl group, an aryl group, a halogenated aryl group, —CN, —NO ₂ , —COR, —COOR (where R is a hydrogen atom, an alkyl group, a halogen atom, alkyl group, selected from aryl group), -. CONRR '(R ' is the same as _{R), -. SO 3 R} , -SOR, may be substituted by -SO ₂ R, F, par It is preferable that an electron withdrawing group such as fluoroalkyl, —CN, —NO ₂ , —COR, —COOR, —CONRR ′, —SO ₃ R, —SOR, and —SO ₂ R is substituted. Ar ^{1 to} Ar ^n-1 may be the same as or different from each other.

Further, Ar ⁿ in the general formula (1) represents an aryl group at the end of the side chain, and examples thereof include an aryl group represented by the following formula (8), and the hydrogen atom of the aryl group is an alkyl group, a halogen atom, or a halogenated group. An alkyl group, an aryl group, a halogenated aryl group, —CN, —NO ₂ , —COR, —COOR (R is selected from a hydrogen atom, an alkyl group, a halogenated alkyl group, and an aryl group), —CONRR ′ (R 'Is the same as R.), -SO ₃ R, -SOR, or -SO ₂ R may be substituted, and Ar ⁿ may be the same or different from each other.

The ^X 1 to X ⁿ in the general formula (2) represents a divalent electron withdrawing group, for example, -CO -, - CONH -, - (CF 2) p - ( wherein, p is from 1 to 10 is an _{integer), - C (CF 3)} 2 -, - COO -, - SO -, - SO 2 - is like, preferably _{-CO -, - C (CF 3} ) 2 -, - SO-, -SO ₂ - and more preferably -CO -, - SO -, - SO 2 - and the like are used. X ^{1 to} X ⁿ may be the same as or different from each other. In the general formula (2) of the present invention, specific examples of the side chain represented by Z include a group of the following formula (9).

（上記式中、スルホン酸基は記載していない。）

(In the above formula, sulfonic acid groups are not described.)

In the present invention, a side chain selected from an unbranched side chain and a branched side chain is usually used, and a branched side chain is preferably used. The branched side chain (i) has a large number of terminal aromatic rings that can be easily sulfonated, and multiple sulfonic acid groups having the same distance to the polymer (main chain) can be introduced into the same side chain. It is considered that an ion cluster structure necessary for proton conductivity is easily formed, and therefore proton conductivity is high. Further, (ii) since the shape of the side chain becomes bulky, it is presumed that the side chains between different polymer chains are entangled with each other, and as a result, the strength of the electrolyte membrane is high and the dimensional stability is also considered high.

In the general formula (2), when f is 1 or more, the side chain represented by the general formula (2) has a branched structure in the aromatic residues Ar ^{1 to} Ar ^n-1 . Each branched chain may have a different chain length and branched structure. That is, the side chain represented by the general formula (2) of the present invention can have, for example, the structure represented by the above formula (6).
The polymer electrolyte of the present invention has at least the repeating unit (A) represented by the general formula (1). As the polymer electrolyte of the present invention, the repeating unit (A) represented by the general formula (1) is usually 1 to 100 mol%, preferably 5 to 95 mol%, more preferably 10 to 80 mol%, Particularly preferred is a polymer containing 15 to 75 mol% and having a weight average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 1,000,000, more preferably 20,000 to 800,000, particularly preferably 30,000 to 400,000. A polymer electrolyte is mentioned.

The polymer electrolyte of the present invention is superior to conventional polymer electrolytes in that (1) high oxidation resistance, (2) desulfonation hardly occurs even at high temperatures, and (3) high proton conductivity. The reason for combining performance is not yet clear, but is estimated as follows.
(1) Reason for high oxidation resistance: It is known that oxidizing substances such as hydrogen peroxide and .OOH radicals are generated during fuel cell operation. Therefore, chemically stable polymer perfluorosulfonic acid has been used as the polymer electrolyte. The conventional hydrocarbon polymer sulfonic acid has insufficient oxidation resistance. For example, in JP-A-2003-201352 and JP-A-2003-20143, an aromatic main chain type polymer electrolyte is used. On the other hand, it is clear from the fact that an antioxidant is used in combination to supplement the oxidation resistance. In addition, the aromatic main chain type polymer electrolyte disclosed in these publications has a side chain having a structure in which an aromatic ring substituted with a sulfonic acid is linked by an electron donating linking group (—O—). Oxidizing substances such as .OOH radicals attack the aromatic ring in an electrophilic manner. Therefore, it is presumed that an aromatic ring having a higher electron density is more likely to be attacked and has a lower oxidation resistance. On the other hand, the electrolyte of the present invention has a side chain having a specific structure in which an aromatic ring substituted with a sulfonic acid is linked by an electron-withdrawing linking group. That is, in the method of the present invention, the electron density of the aromatic ring is decreased by using an electron-withdrawing linking group, and therefore, it is considered that the oxidizing substance hardly reacts and has high oxidation resistance.

(2) Reason why desulfonation is difficult to occur: On the other hand, aromatic sulfonic acid is known to proceed with desulfonation at higher temperatures, and there is no desulfonation near 100 ° C., which is the fuel cell operating temperature. Improvement of this point was one of the problems of the polymer sulfonic acid electrolyte. The desulfonation reaction is considered to be initiated by proton attack on the aromatic sulfonic acid, and therefore, it is presumed that an aromatic ring having a higher electron density is more easily desulfonated. As described above, the electrolyte of the present invention substituted with an electron-withdrawing linking group is presumed to be difficult to desulfonate because the electron density of the aromatic ring is low.
(3) Reason for high proton conductivity: The electrolyte of the present invention substituted with an electron-withdrawing linking group has a low electron density of the aromatic ring. Therefore, it is presumed that the acid dissociation constant is high in order to stabilize the dissociated sulfonate anion, and therefore the proton conductivity is high.

The polymer electrolyte of the present invention is not conventionally known. Because there was an inevitable reason. That is, a conventionally known polymer electrolyte having a side chain sulfonic acid (for example, a polymer electrolyte disclosed in JP-A-2003-201352 synthesized in the synthesis of an actual polymer described later) The aromatic ring substituted with sulfonic acid has a structure in which the electron donating linking group is connected. Usually, when an aromatic ring is sulfonated, if the electron-withdrawing group is substituted, the reactivity of the aromatic ring is significantly reduced, and as a result, it becomes difficult to proceed with sulfonation. Therefore, in the conventional method, the electron donating group had to be replaced in order to activate the aromatic ring and facilitate the progress of sulfonation. As a result, it was difficult to synthesize a polymer electrolyte having a side chain electron-withdrawing linking group as in the present invention. On the other hand, in the present invention, by using an electron donating linking group precursor that can be converted into an electron withdrawing linking group, (1) promotion of sulfonation reactivity and (2) use of an electron withdrawing linking group, It is possible for the first time to satisfy both of the requirements, and as a result, the excellent effects of the present invention can be found.

The method for producing the polymer electrolyte of the present invention is not particularly limited. For example,
(M1) Method of introducing a side chain by reacting a polymer with a side chain introducing agent -Y-P- (Y is a divalent fragrance corresponding to the structure in which Z is not substituted in the general formula (1)) Z may be introduced by reacting a side chain introducing agent with a polymer having a group residue, P as described above as a repeating unit, or -Y (M)-in which a reactive substituent is introduced in advance. Z may be introduced by reacting P- (Y is a trivalent aromatic residue, M is a reactive group, and P is as described above) with a side chain introducing agent that reacts with M.
(M2) A method for polymerizing a monomer having at least a side chain

  It can also be obtained by polymerizing the monomer corresponding to the repeating structural unit (A) and the monomer corresponding to the other repeating unit, and the oligomer corresponding to the repeating unit (A) and the monomer corresponding to the other repeating unit are first oligomers. And then reacting the oligomers with each other or with the oligomer and monomers. In addition, a monomer corresponding to a structure in which the repeating unit (A) and one or a plurality of other repeating units are linked is synthesized in advance, and homopolymerization of this monomer or polymerization of this with a monomer corresponding to another repeating structure. Can also be synthesized.

Specific examples of the method (M1) that are usually used are as follows. That is, by reacting a polymer having a repeating unit represented by the following general formula (10) with a side chain introducing agent represented by the following general formula (11), the polymer represented by the above general formula (1). An electrolyte can be manufactured. In this case, X in the general formula (2) is selected from —CO— and —SO ₂ —.

In the general formula (10), Y and P are the same as those described in the general formula (1), U is a reactive group selected from a hydrogen atom, —COX, and —SO ₂ X, and X is It is selected from a halogen atom, OR (R is a hydrogen atom, an alkyl group or an aryl group), and a hydroxyl group.
Z'-V (11)
When U in the general formula (10) is a hydrogen atom, V is a reactive group selected from —COX and —SO ₂ X, and U is a reactive group selected from —COX and —SO ₂ X In the formula, V is a hydrogen atom, and Z ′ is represented by the following general formula (12).
^{Z '= - (Ar 1 (} B 1)) - (X 2 Ar 2 (B 2)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar n (12)
(In the general formula (12), Ar, B and n are the same as those described in the general formula (2), and X is selected from the linking group and the linking group precursor described in the general formula (2). )
A linking group precursor refers to a group that can be converted to a linking group. As a method for converting the linking group precursor into a linking group, a known method can be used. Table 1 shows an example.

The linking group precursor may be converted to the linking group at any point, but the following method is preferably used. That is, when the polymer having the repeating unit represented by the general formula (10) and the side chain introducing agent represented by the general formula (11) are reacted,
(I) The side chain introducing agent does not have a sulfonic acid group or a precursor thereof, and X of the side chain introducing agent is an electron donating linking group precursor, and is sulfonated after reacting with a polymer. Followed by converting the linking group precursor to an electron-withdrawing linking group, or
(Ii) when the side chain introducing agent has a sulfonic acid group or a precursor thereof, and X of the side chain introducing agent is (ii-1) an electron donating linking group precursor, By converting the linking group precursor into an electron-withdrawing linking group, (ii-2) when it is an electron-withdrawing linking group, the repeating unit represented by the general formula (1) in that state It is a method of obtaining the polymer electrolyte for fuel cells which has this.

Examples of the polymer having a repeating unit represented by the general formula (10) used in the present invention are shown below.
U is a hydrogen atom: a divalent aromatic residue selected from the residues represented by the general formula (7), -CO-, -O-, -S-, -SO-, -SO _2- , A polymer comprising a combination of —CONH—, —C (CF ₃ ) ₂ — and a linking group P selected from a single bond is usually used, and preferably a divalent aromatic residue selected from phenylene, naphthylene and biphenylene A combination of linking groups P selected from —CO—, —O—, —S—, —SO ₂ — is used, more preferably polyether ketone, polyether sulfone, polythioether ketone, polythioether sulfone, polyether ether. Sulfone and polyetheretherketone are used, and more preferably, a polymer represented by the following formula having Z as a hydrogen atom is used.

When U is —COX or —SO ₂ X: a divalent aromatic residue selected from the residues represented by the general formula (7), —CO—, —O—, —S—, —SO—, A polymer in which —COX or —SO ₂ X is introduced into a polymer composed of a combination of —SO ₂ —, —CONH—, —C (CF ₃ ) ₂ —, and a linking group P selected from a single bond is usually used. Is a polymer of a combination of a divalent aromatic residue selected from phenylene, naphthylene, and biphenylene and a linking group P selected from —CO—, —O—, —S—, and —SO ₂ —. which was introduced _{2 X} is used, more preferably polyether ketone, polyether sulfone, polythioether ketone, polythioether sulfone, polyether ether sulfone, polyether ether ketone - Which was introduced OX or -SO ₂ X is used, or more preferably, those wherein Z in the polymer represented by the above formula was introduced -COX or -SO ₂ X is used. (A known introduction method can be used to introduce —COX or —SO ₂ X). When U in the general formula (10) is COX or SO ₂ X, X is usually selected from a halogen atom, OR (where R is a hydrogen atom, an alkyl group, or an aryl group), and a hydroxyl group. Selected from atoms and hydroxyl groups. Examples of the side chain introducing agent represented by the general formula (7) are shown below.

Reactivity in which the side chain introducing agent has a sulfonic acid group or a precursor thereof, X in the side chain introducing agent is an electron-withdrawing linking group, and V is selected from —COX and —SO ₂ X Examples of preferred Z′-V in the case of a group are shown in the following general formula (12) and the following general formula (13). Further preferred Z′-V is a branched structure represented by the following general formula (13). (In the formula, —SO ₃ R represents a sulfonic acid group or a precursor thereof, and R is selected from a hydroxyl group, an alkyl group, an alkali metal, and an alkaline earth metal.)

The side chain introducing agent does not have a sulfonic acid group or a precursor thereof, X of the side chain introducing agent is an electron donating linking group precursor, and V is from —COX and —SO ₂ X Examples of preferred Z′-V in the case of the selected reactive group are shown in the following general formula (14) and the following general formula (15). Further preferred Z ′ is a branched structure represented by the following general formula (15). Examples of preferred Z′-V when V is a hydrogen atom are shown in the following general formula (16) and the following general formula (17).

X in V in the general formula (11) is usually selected from a halogen atom, OR (R is a hydrogen atom, an alkyl group, or an aryl group), and a hydroxyl group, and preferably selected from a halogen atom and a hydroxyl group.
The type of reaction when the side chain introduction agent is reacted with the polymer is not particularly limited. A preferable method for reacting the polymer represented by the general formula (10) with the side chain introducing agent represented by the general formula (11) includes the following method.
(I) U in the general formula (10) is a hydrogen atom, V in the general formula (11) is —COX (X is a halogen atom or a hydroxyl group), or U in the general formula (10) is When -COX (X is a halogen atom) and V in the general formula (11) is a hydrogen atom: Friedel-Crafts-acylation reaction can be used.
(Ii) U in the general formula (10) is a hydrogen atom, V in the general formula (11) is —SO ₂ X (X is a halogen atom or a hydroxyl group), or in the general formula (10) When U is —SO ₂ X (X is a halogen atom) and V in the general formula (11) is a hydrogen atom: Friedel-Crafts type sulfonylation reaction can be used.
(Iii) U in the general formula (10) is a hydrogen atom, V in the general formula (11) is —COOH or —SO ₃ H, or U in the general formula (10) is —COOH or When —SO ₃ H and V in the general formula (11) are a hydrogen atom: a dehydration condensation reaction can be used.

A specific example of the method (M2) is shown below. That is, the polymer electrolyte represented by the general formula (1) can be produced by polymerizing at least the monomer represented by the general formula (16).
The linking group precursor may be converted to the linking group at any point, but the following method is preferably used. That is, at least when the monomer represented by the following general formula (18) is polymerized,
(I) Z ″ does not have a sulfonic acid group or a precursor thereof, and X of Z ″ is an electron donating linking group precursor, which is subjected to sulfonation after polymerization, followed by a linking group precursor. By converting the body into an electron-withdrawing linking group, or
(Ii) when Z ″ has a sulfonic acid group or a precursor thereof, and X in Z ″ is (ii-1) an electron-donating linking group precursor, then the linking group precursor Is converted into an electron-withdrawing linking group, so that (ii-2) a fuel cell having a repeating unit represented by the general formula (1) in that state when it is an electron-withdrawing linking group This is a method for obtaining a polymer electrolyte for use.

(Wherein k and Y are the same as those in the general formula (1), W and W ′ are a hydrogen atom, halogen, —COX (X is a halogen or OR (R is a hydrogen atom, an alkyl group, or an aryl group)) ), —OH, —SH, —SO ₂ X (X is as defined above), which may be the same or different, and Z ″ is selected from the linking group and the linking group precursor described above. And is the same as Z in the general formula (1) except that Ar may have a sulfonic acid group.
In the polymer of the present invention, any other repeating unit other than the repeating unit (A) can be used as long as it can be polymerized. The repeating unit represented by the following general formula (19) (B ) Is preferably used.
-Y ² -P ² - (19)
(In the formula, Y ² is selected from the same divalent aromatic residues as those shown in the general formula (7), and the hydrogen atom of the aromatic residue is an alkyl group, a halogen atom, or a halogenated alkyl group. , Or an aryl group, and P ² may be —CO—, —O—, —S—, —SO—, —SO ₂ —, —COO—, —SO ₃ —, —CONH—, Selected from the bond, preferably selected from —CO—, —O—, —S—, —SO ₂ —).

In the preferred polymer of the present invention, the repeating unit (A) and the other repeating unit (hereinafter, the Y side chain group Z is abbreviated in this paragraph for the sake of simplicity), for example, —Y—P—Y ² —P ² —. Like Y—P—, Y or Y ² may be bonded to Y or Y ² via P or P ² , and an arbitrary repeating order can be taken. For ^{_{example, - (Y-P) m}} - (Y 2 -P 2) n - (m, n is a positive integer) may be a block polymer such as, or may be random polymers. The ratio of the repeating unit (A) to other repeating units is 5 to 95 mol%, preferably 10 to 80 mol%, more preferably 15 to 75 mol%, and 95 to 5 other repeating units. It is mol%, preferably 90 to 20 mol%, more preferably 85 to 25 mol%. When another repeating unit other than the repeating unit (A) is composed of the repeating unit (B), the same type of repeating unit (B) may be used, or a plurality of types of repeating units (B) may be used. Also good.

Hereinafter, an example of a synthesis method usually used as the method (M2) will be described.
[Synthesis Method-1] In the present invention, a coupling reaction between aromatic halides using a transition catalyst is preferably used as a reaction for producing a polymer in which the linking group P is a single bond. . For example, the methods described in US Pat. No. 5,403,675 and JP-A-2003-201352 can be used.
[Synthesis Method-2] In the present invention, aromatic compounds of aromatic hydroxy compounds and aromatic halides are preferably used as a reaction when producing a polymer in which the linking group P and / or P ² is —O—. This is a synthesis reaction of an aromatic polyether by a group nucleophilic substitution reaction.
For example, “High Performance Aromatic Polymer Material” edited by Polymer Society of Japan (Maruzen Co., Ltd. March 30, 1990) p. The method described in 128-132 can be used. As another method, a reaction in which aromatic halides are reacted with each other in the presence of a carbonate and a catalyst to synthesize an aromatic polyether can be used. For example, Macromolecules, 1991, Vol. 24, p. The method described in 3838 (Fukawa et al.) Can be used.

In Synthesis process -3 present invention, as preferably used reaction in the linking group P and / or P ² to produce a polymer which is -S-, an aromatic hydroxy compound in the synthesis method -2 Instead, an aromatic polysulfide is synthesized using an aromatic thiol compound. As another method, a reaction of synthesizing an aromatic polysulfide from aromatic dichloride and sodium sulfide can be used. For example, p. Of “High Performance Aromatic Polymer Materials” (Maruzen Co., Ltd., March 30, 1990) edited by the Society of Polymer Science. The method described in 133-134 can be used.
In Synthesis method -4] The present invention, linking groups P and / or P ² is -SO 2 _- to be preferably used as a reaction in the production of a is polymer, aromatic produced by the above synthesis method -3 In this method, sulfides are oxidized using an oxidizing agent such as hydrogen peroxide.
As another method, an aromatic compound having an aromatic ring having a hydrogen atom in an aromatic ring can be used by forming an aromatic sulfone bond by subjecting an aromatic sulfonic acid halide to an electrophilic substitution reaction. For example, p. Of “High Performance Aromatic Polymer Materials” (Maruzen Co., Ltd., March 30, 1990) edited by the Society of Polymer Science. The method described in 132-133 can be used.
In Synthesis method -5 present invention, as preferably used reaction in the linking group P and / or P ² to produce a polymer which is -CO-, Friedel-Crafts - acylation reaction. For example, p. Of “High Performance Aromatic Polymer Materials” (Maruzen Co., Ltd., March 30, 1990) edited by the Society of Polymer Science. The method described in 132-133 can be used.

Next, an example of a preferred synthesis method according to the method (M2) will be described. [Example of polymer-1] The polymer is composed of a repeating unit (A) and a repeating unit (B), and the linking groups P and P ² are either In the case of -O-: For example, the reaction of the repeating unit (A) monomer represented by the following general formula (20) with the repeating unit (B) monomer represented by the following general formula (21), or the following general formula (22) Reaction of the repeating unit (A) monomer shown in FIG. 5 with the repeating unit (B) monomer shown in the following general formula (23), or the repeating unit (A) monomer shown in the following general formula (24) and the following general formula ( A polymer represented by the following general formula (26) comprising the repeating unit (A) and the repeating unit (B) can be obtained by reaction with the repeating unit (B) monomer shown in 25).

（式中、Ｘはハロゲン原子を表し、Ｙ 、Ｙ^２ 、Ｚ”は前記のとおりである。）

(In the formula, X represents a halogen atom, and Y 1, Y ² , and Z ″ are as described above.)

The above general formula (21), (22), (24), (25) of oxygen atoms in the use of raw material with sulfur atom instead, linking groups P and ^{P 2} are both a -S- A polymer can be obtained.
Specific examples of the repeating unit (A) monomer represented by the general formula (20) include 2,5-dichloro-4 ′-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone, 2,5- Dibromo-4 '-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone, 2,5-diiodo-4'-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone; 2,5-dichloro -4 '-(4-thiophenoxy) thiophenoxybenzophenone, 2,5-dibromo-4'-(4-thiophenoxy) thiophenoxybenzophenone, 2,5-diiodo-4 '-(4-thiophenoxy) thiophenoxy Benzophenone; 2,5-dichloro-4'-thiophenoxybenzophenone, 2,5-dibromo-4'-thiophene Xylbenzophenone, 2,5-diiodo-4′-thiophenoxybenzophenone; 2,5-dichloro-1- (4-thiophenoxy) thiophenoxybenzene, 2,5-dibromo-1- (4-thiophenoxy) thiophenoxy Benzene, 2,5-diiodo-1- (4-thiophenoxy) thiophenoxybenzene; 2,5-dichloro-1- (4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene, 2,5-dibromo-1 -(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene, 2,5-diiodo-1- (4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene; 2,5-dichloro-4 '-(4 -Benzoyl) benzoylbenzophenone, 2,5-dibromo-4 '-(4-benzoyl) benzoylbenzof Enone, 2,5-diiodo-4 ′-(4-benzoyl) benzoylbenzophenone; 2,5-dichloro-4′-benzoylbenzophenone, 2,5-dibromo-4′-benzoylbenzophenone, 2,5-diiodo-4 Examples include '-benzoylbenzophenone and regioisomers thereof.

  Specific examples of the repeating unit (A) monomer represented by the general formula (22) include 2,5-dihydroxy-4 ′-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone; Dihydroxy-4 ′-(4-thiophenoxy) thiophenoxybenzophenone; 2,5-dihydroxy-4′-thiophenoxybenzophenone; 2,5-dihydroxy-1- (4-thiophenoxy) thiophenoxybenzene; Dihydroxy-1- (4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene; 2,5-dihydroxy-4 ′-(4-benzoyl) benzoylbenzophenone; 2,5-dihydroxy-4′-benzoylbenzophenone and their And positional isomers.

Specific examples of the repeating unit (A) monomer represented by the general formula (24) include 2-chloro-5-hydroxy-4 ′-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone, 2- Bromo-5-hydroxy-4 ′-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone, 2-iodo-5-hydroxy-4 ′-(4-thiophenoxy-4-thiophenoxy) thiophenoxybenzophenone, 2-chloro-5-hydroxy-4 ′-(4-thiophenoxy) thiophenoxybenzophenone, 2-bromo-5-hydroxy-4 ′-(4-thiophenoxy) thiophenoxybenzophenone, 2-iodo-5-hydroxy -4 '-(4-thiophenoxy) thiophenoxybenzophenone; 2-chloro-5-hydroxy -4'-thiophenoxybenzophenone, 2-bromo-5-hydroxy-4'-thiophenoxybenzophenone, 2-iodo-5-hydroxy-4'-thiophenoxybenzophenone; 2-chloro-5-hydroxy-1- (4 -Thiophenoxy) thiophenoxybenzene, 2-bromo-5-hydroxy-1- (4-thiophenoxy) thiophenoxybenzene, 2-iodo-5-hydroxy-1- (4-thiophenoxy) thiophenoxybenzene; Chloro-5-hydroxy-1- (4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene, 2,5-dibromo-1- (
4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene, 2-iodo-5-hydroxy-1- (4-thiophenoxy-4-thiophenoxy) thiophenoxybenzene; 2-chloro-5-hydroxy-4′- (4-benzoyl) benzoylbenzophenone, 2-bromo-5-hydroxy-4 ′-(4-benzoyl) benzoylbenzophenone, 2-iodo-5-hydroxy-4 ′-(4-benzoyl) benzoylbenzophenone; 2-chloro- Examples include 5-hydroxy-4′-benzoylbenzophenone, 2-bromo-5-hydroxy-4′-benzoylbenzophenone, 2-iodo-5-hydroxy-4′-benzoylbenzophenone, and positional isomers thereof.

  Specific examples of the repeating unit (B) monomer represented by the general formula (21) include 4,4′-dihydroxybenzophenone, 2,4′-dihydroxybenzophenone, 3,3′-dihydroxybenzophenone; -Dihydroxydiphenyl ether, 2,4'-dihydroxydiphenyl ether, 3,3'-dihydroxydiphenyl ether; 4,4'-dihydroxydiphenyl thioether, 2,4'-dihydroxydiphenyl thioether, 3,3'-dihydroxydiphenyl thioether; 2,2 -Bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-hydroxyphenyl) hexafluoropropane; bis (hydroxyphenyl) difluoromethane; 4-hydroxybenzoic acid-4-hydroxyphenyl, -Hydroxybenzoic acid-3-hydroxyphenyl, 3-hydroxybenzoic acid-3-hydroxyphenyl, 3-hydroxybenzoic acid-4-hydroxyphenyl; bis (4-hydroxyphenyl) sulfoxide, bis (3-hydroxyphenyl) sulfoxide; Bis (4-hydroxyphenyl) sulfone, bis (3-hydroxyphenyl) sulfone; 2,5-dihydroxy4'-phenoxybenzophenone, p-dihydroxybenzene, 2,5-dihydroxytoluene, 2,5-dihydroxyp-xylene, 2,4-dihydroxybenzotrifluoride, 1,4-dihydroxy 2,3,5,6-tetrafluorobenzene; 4,4'-dihydroxybiphenyl; m-dihydroxybenzene, 2,4-dihydroxytoluene, 3,5- Dihydroxy Toluene, 2,6-dihydroxy-toluene and the like.

Specific examples of the repeating unit (B) monomer represented by the general formula (23) include 4,4'-dichlorobenzophenone, 2,4'-dichlorobenzophenone, 3,3'-dichlorobenzophenone, 4,4 ' -Dibromobenzophenone, 2,4'-dibromobenzophenone, 3,3'-dibromobenzophenone, 4,4'-diiodobenzophenone, 2,4'-diiodobenzophenone, 3,3'-diiodobenzophenone; 4,4 '-Dichlorodiphenyl ether, 2,4'-dichlorodiphenyl ether, 3,3'-dichlorodiphenyl ether, 4,4'-dibromodiphenyl ether, 2,4'-dibromodiphenyl ether, 3,3'-, dibromodiphenyl ether, 4,4' -Diiododiphenyl ether, 2,4'-diiododi Phenyl ether, 3,3′-diiododiphenyl ether; 4,4′-dichlorodiphenyl thioether, 2,4′-dichlorodiphenyl thioether, 3,3′-dichlorodiphenyl thioether, 4,4′-dibromodiphenyl thioether, 2, 4'-dibromodiphenyl thioether, 3,3'-, dibromodiphenyl thioether, 4,4'-diiododiphenyl thioether, 2,4'-diiododiphenyl thioether, 3,3'-diiododiphenyl thioether:
2,2-bis (4-chlorophenyl) hexafluoropropane, 2,2-bis (3-chlorophenyl) hexafluoropropane, 2,2-bis (4-bromophenyl) hexafluoropropane, 2,2-bis (3 -Bromophenyl) hexafluoropropane, 2,2-bis (4-iodophenyl) hexafluoropropane, 2,2-bis (3-iodophenyl) hexafluoropropane; bis (chlorophenyl) difluoromethane, bis (bromophenyl) Difluoromethane, bis (iodophenyl) difluoromethane; 4-chlorobenzoic acid-4-chlorophenyl, 4-chlorobenzoic acid-3-chlorophenyl, 3-chlorobenzoic acid-3-chlorophenyl, 3-chlorobenzoic acid-4-chlorophenyl 4-bromobenzoic acid-4-bromophenyl 4-bromobenzoic acid-3-bromophenyl, 3-bromobenzoic acid-3-bromophenyl, 3-bromobenzoic acid-4-bromophenyl; bis (4-chlorophenyl) sulfoxide, bis (3-chlorophenyl) sulfoxide, bis (4-bromophenyl) sulfoxide, bis (3-bromophenyl) sulfoxide, bis (4-iodophenyl) sulfoxide, bis (3-iodophenyl) sulfoxide;
Bis (4-chlorophenyl) sulfone, bis (3-chlorophenyl) sulfone, bis (4-bromophenyl) sulfone, bis (3-bromophenyl) sulfone, bis (4-iodophenyl) sulfone, bis (3-iodophenyl) Sulfone; 2,5-dichloro-4'-phenoxybenzophenone, p-dichlorobenzene, p-dibromobenzene, p-diiodobenzene, 2,5-dichlorotoluene, 2,5-dibromotoluene, 2,5-diiodo Toluene, 2,5-dichloro-p-xylene, 2,5-dibromo-p-xylene, 2,5-diiodo-p-xylene, 2,5-dichlorobenzotrifluoride, 2,5-dibromobenzotrifluoride, 2,5-diiodobenzotrifluoride, 1,4-dichloro-2,3,5,6-tetra Fluorobenzene, 1,4-dibromo-2,3,5,6-tetrafluorobenzene, 1,4-diiodo-2,3,5,6-tetrafluorobenzene; 4,4'-dichlorobiphenyl, 4,4 ' -Dibromobiphenyl, 4,4'-diiodobiphenyl, 4,4'-dibromooctafluorobiphenyl; m-dichlorobenzene, m-dibromobenzene, m-diiodobenzene, 2,4-dichlorotoluene, 2,4- Dibromotoluene, 2,4-diiodotoluene, 3,5-dichlorotoluene, 3,5-dibromotoluene, 3,5-diiodotoluene, 2,6-dichlorotoluene, 2,6-dibromotoluene, 2,6 -Diiodotoluene, 1,3-dibromo-2,4,5,6-tetrafluorobenzene and the like. In addition, in the said specific example, what substituted one of two X in General formula (13) by the fluorine atom can be used preferably.

As a specific example of the repeating unit (B) monomer represented by the general formula (26), one of non-fluorine halogen atoms in the specific example of the repeating unit (B) monomer represented by the general formula (15). And a positional isomer thereof.
Specific examples of synthesis in the case where the polymer is composed of the repeating unit (A) and the repeating unit (B) and the linking groups P and P ² are both —O— are shown below. 2,5-Dichloro-4 ′-(4-thiophenoxy) thiophenoxybenzophenone is used as the monomer of the repeating unit (A), and p, p′-dihydroxybenzophenone is used as the monomer of the repeating unit (B). Both are copolymerized in the presence of potassium carbonate, then sulfonated using a sulfonated agent, and then oxidized to a sulfone by oxidizing the sulfide bond using an oxidant to form a linking group P = O, A polymer (Q = —CO—) sulfone oxide represented by the following general formula (27) where P ² ═O is obtained as a polymer electrolyte.

（式中、Ｚ”は側鎖基を示す。）

(In the formula, Z ″ represents a side chain group.)

Similarly, Q is —O—, —S—, —SO ₂ —, —CR ¹ ₂ — (R ¹ is selected from a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, and an aryl group) or a single atom. A polymer that is a bond can be synthesized.
Consists [Examples of polymers -2 polymer repeating unit (A) and the repeating unit (B), in the case where the linking group P and P ² is either a single bond: represented by the following general formula (28), the repeating unit (A)
By reacting the monomer with the repeating unit (B) monomer represented by the following general formula (29), a polymer represented by the following general formula (30) comprising the repeating unit (A) and the repeating unit (B) is obtained. be able to. Specific examples of the repeating unit (A) monomer represented by the following general formula (28) include compounds similar to the specific examples for the general formula (20). Specific examples of the repeating unit (B) monomer represented by the following general formula (29) include the same compounds as the specific examples for the general formula (23).

（式中、Ｘ、Ｘ’は互いに同一であっても異なっていても良いハロゲン原子を表し、Ｙ 、Ｙ^２ 、Ｚは前記のとおりである。）

(In the formula, X and X ′ represent the same or different halogen atoms, and Y 1, Y ² and Z are as defined above.)

Specific examples of the case where the polymer is composed of the repeating unit (A) and the repeating unit (B) and the linking groups P and P ² are both single bonds are shown below. 2,5-Dichloro-4′-thiophenoxybenzophenone is used as the monomer of the repeating unit (A), and p, p′-dichlorodiphenylsulfone is used as the monomer of the repeating unit (B). Both are copolymerized in the presence of a catalyst containing a transition metal compound, then sulfonated using a sulfonated agent, and then oxidized by using an oxidant to convert the sulfide bond to a sulfone. A polymer (Q = —SO ₂ —) sulfone oxide represented by the following formula (31) in which the group P = single bond and P ² = single bond is obtained as a polymer electrolyte.

（式中、Ｚ”は側鎖基を示す。）

(In the formula, Z ″ represents a side chain group.)

Consists Polymerization of Example -3] polymer repeat units (A) and the repeating unit (B), in the case where the both linking groups P and ^{P 2} -CO-: for example represented by the following general formula (32), Reaction of repeating unit (A) monomer with repeating unit (B) monomer shown in the following general formula (33), or repeating unit (A) monomer shown in the following general formula (34) and the following general formula ( A polymer represented by the following general formula (36) comprising the repeating unit (A) and the repeating unit (B) can be obtained by the reaction with the repeating unit (B) monomer shown in 35). In addition, by using a raw material using SO ₂ instead of CO in the following general formulas (33) and (34), a polymer in which the linking groups P and P ² are both —SO ₂ — is obtained. (In the formula, X represents a halogen atom, and Y, Y ² and Z are as defined above.)

As a specific example of the repeating unit (A) monomer represented by the general formula (32), -X in the specific example of the repeating unit (A) monomer represented by the general formula (20) is substituted with a hydrogen atom. And the positional isomers thereof.
Specific examples of the repeating unit (A) monomer represented by the general formula (34) include -X in the specific example of the repeating unit (A) monomer represented by the general formula (20) -COX (X Represents a halogen atom) and the positional isomers thereof.
Specific examples of the repeating unit (B) monomer represented by the general formula (33) include -X in the specific example of the repeating unit (B) monomer represented by the general formula (23) -COX (X Represents a halogen atom) and the positional isomers thereof.
As a specific example of the repeating unit (B) monomer represented by the general formula (35), X in the specific example of the repeating unit (B) monomer represented by the general formula (23) was substituted with a hydrogen atom. Examples include structures.

Specific examples of synthesis in the case where the polymer is composed of the repeating unit (A) and the repeating unit (B) and the linking groups P and P ² are both —CO— are shown below. 2- [4- (4-thiophenoxy) thiophenoxybenzoyl] terephthal chloride is used as the monomer of the repeating unit (A), and diphenyl ether is used as the monomer of the repeating unit (B). Both are copolymerized in the presence of a Friedel-Crafts catalyst such as aluminum chloride, then sulfonated with a sulfonated agent, and then oxidized with an oxidant to convert the sulfide bond to sulfone, A polymer (Q = -O-) sulfone oxide represented by the following general formula (37) having a linking group P = CO and P ² = CO is obtained as a polymer electrolyte.

（式中、Ｚ”は側鎖基を示す。）

(In the formula, Z ″ represents a side chain group.)

Similarly, Q is —CO—, —S—, —SO ₂ —, —CR ¹ ₂ — (R ¹ is selected from a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, and an aryl group) or a single atom. A polymer that is a bond can be synthesized.
[Examples of polymers -4] polymer repeat units (A) and a plurality of repeating units (B), the linking group P is a single bond, if the linking group P ² is -O-: following general formula ( 38) and the repeating unit (A) monomer and the repeating unit (B) monomer represented by the following general formula (39) and the following general formula (40) are reacted with the repeating unit (A) and two kinds of repeating units. A polymer represented by the following general formula (41) consisting of the unit (B) can be obtained.

（式中、Ｘ、Ｘ’、Ｘ’’はハロゲン原子を表し互いに異なっていても同一でも良く、Ｙ^２’はＹ^２と同様の基であり、Ｙ 、Ｙ^２、Ｚは前記のとおりである。）

(Wherein, X, X ', X'' may be the same or different from one another represent a halogen atom, Y ^2' is the same group as ^{Y 2, Y, Y 2,} Z is as defined above is there.)

Specific examples of the repeating unit (A) monomer represented by the general formula (38) include compounds similar to the specific examples for the general formula (20). Specific examples of the repeating unit (B) monomer represented by the general formula (39) include compounds similar to the specific examples for the general formula (23). Specific examples of the repeating unit (B) monomer represented by the general formula (40) include compounds similar to the specific examples for the general formula (21).
Specific examples of the case where the polymer is composed of the repeating unit (A) and the repeating unit (B), the linking group P is a single bond, and the linking group P ² is —O— are shown below. 2,5-Dichloro-4′-thiophenoxybenzophenone is used as the monomer of the repeating unit (A), and 4-chlorofluorobenzene and 4,4′-dihydroxybenzophenone are used as the monomer of the repeating unit (B). First, bis [4- (4-chlorophenoxy) phenyl] sulfone is synthesized by reacting 4-chlorofluorobenzene and bis (4-hydroxyphenyl) sulfone in the presence of potassium carbonate. Next, this and 2,5-dichloro-4'-thiophenoxybenzophenone are copolymerized in the presence of a catalyst containing a transition metal compound, and then sulfonated with a sulfonated agent, and then a sulfide bond is formed. Oxidation using an oxidizing agent and conversion to sulfone allows the polymer (Q = —SO ₂ —) sulfone represented by the following general formula (42) with a linking group P = single bond and P ² = —O— bond. An oxide is obtained as a polymer electrolyte. In the polymer of the present invention, the proportion of the repeating unit (B) in the other repeating units is 10 to 100 mol%, preferably 20 to 100 mol%.

（式中、Ｚ”は側鎖基を示す。）

(In the formula, Z ″ represents a side chain group.)

The aromatic residue contained in the main chain of the polymer electrolyte of the present invention preferably has at least one electron withdrawing group bonded thereto. The electron withdrawing group in this case is, for example, —CO—, —CONH—, — (CF ₂ ) _p — (wherein p is an integer of 1 to 10), —C (CF ₃ ) ₂ —, — Divalent groups such as COO—, —SO—, —SO ₂ —; F, perfluoroalkyl, —CN, —NO ₂ , —COR, —COOR (where R is hydrogen, alkyl group, halogenated alkyl group, aryl) And a monovalent group such as —CONR ′ (wherein R ′ is the same group as R), —SO ₃ R, —SOR, —SO ₂ R, and the like. .

Examples of the structure of the polymer electrolyte of the present invention are shown below (wherein Z represents a side chain represented by the general formula (1)).

  In the polymer electrolyte of the present invention, a sulfonic acid group is present in the side chain Z. And at least n ≧ 2, and the number of sulfonic acid groups exceeding 1.0 is introduced. In addition, when Z is linear, the sulfonic acid group may be introduce | transduced into several Ar group of the same side chain. Furthermore, the main chain may be further substituted with a sulfonic acid group. In the production method of the present invention, the method for introducing a sulfonic acid group is not limited. For example, (1) the polymer may be introduced by sulfonating, or (2) a monomer containing a sulfonic acid group is polymerized. Alternatively, (3) a sulfonic acid group can be introduced by polymerizing a monomer containing a group selected from a sulfonic acid group derivative and a sulfonic acid group precursor and then converting the group into a sulfonic acid group.

In the method for producing a polymer electrolyte of the present invention, as a method for introducing a sulfonic acid group, when introducing a polymer not containing a sulfone group by sulfonating, a conventional sulfonation with a sulfonating agent is used. be able to. As a method for introducing a sulfonic acid group, for example, the above-described polymer having no sulfonic acid group is known by using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid, sodium bisulfite, (In the present invention, sulfonation refers to a reaction in which a hydrogen atom of a group —H is substituted with SO ₃ H).

As the reaction conditions for the sulfonation, the polymer having no sulfonic acid group is reacted with the sulfonated agent in the absence of a solvent or in the presence of a solvent. Examples of the solvent include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide, and dimethylsulfoxide, tetrachloroethane, dichloroethane, chloroform, And halogenated hydrocarbons such as methylene chloride. The reaction temperature is not particularly limited, but is usually −50 to 200 ° C., preferably −10 to 100 ° C. Moreover, reaction time is 0.5 to 1,000 hours normally, Preferably it is 1 to 200 hours.

  The molecular weight of the polymer electrolyte of the present invention thus obtained before sulfonation or the precursor of sulfonic acid is a polystyrene-converted weight average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 1,000,000. More preferably, it is 20,000 to 800,000, and particularly preferably 30,000 to 400,000. If it is less than 1000, the molded film is liable to break, and there is also a problem in strength properties. On the other hand, if it exceeds 1,000,000, there are problems such as insufficient solubility, high solution viscosity, and poor processability.

<Structure of electrolyte membrane>
The electrolyte of the present invention is characterized in that the sulfonated equivalent of the membrane inner region adjacent to both membrane surfaces is lower than the sulfonated equivalent of the membrane surface adjacent to the inner region. This state has the following two types.
(1) Membrane in which sulfonated equivalent weight is discontinuous and forming a layer structure In both regions of the membrane and a region of 5 μm wide from both surfaces sandwiched between the surfaces entering 5 μm from both surfaces toward the inside, There is an interface where the sulfonating equivalent is reduced discontinuously, and the interface is divided into a surface layer and an inner layer. The sulfonated equivalent of the inner layer is 80% or less with respect to the sulfonated equivalent of the adjacent membrane surface. Preferably it is 70% or less, More preferably, it is 60% or less.

Specifically, for example, if there are a first layer, a second layer, and a third layer from the surface, the first layer and the third layer are surface layers, and the second layer is an internal layer. . Therefore, the layer adjacent to the surface is the second layer. The value of the sulfonated equivalent weight is lowest in the second layer, and higher in the first layer and the third layer. The numerical values of the sulfonated equivalents of the first layer and the third layer may be the same or different.
Also, if there are first, second, third, fourth, and fifth layers, the first layer is the surface layer and the layer adjacent to it is the second layer. The fifth layer is also a surface layer, and the layer adjacent to it is the fourth layer. The sulfonation oxidation equivalent is lower in the second layer than in the first layer and lower in the fourth layer than in the fifth layer. The sulfonation equivalent of the third layer does not depend on these layers and may be high or low. If it is high, the ion conductivity is good, and if it is low, the membrane is reinforced at the center, so that the membrane strength and durability are improved, and it functions as a layer for suppressing methanol permeation. This is the same even in the case of having more layers. If the relationship between both surfaces and the adjacent layers satisfies the above conditions, the sulfonated equivalents of the other layers depend on the target membrane performance. Select as appropriate. Moreover, in the inside other than the double-sided layer and its adjacent layer, a structure in which the sulfonic acid equivalent is continuously changed may be taken.

(2) Unlike the membrane (1) in which the sulfonated equivalent is continuously changed, there is no interface, but the sulfonated equivalent in the region up to 5 μm in the thickness direction from both surfaces of the membrane to the inside. Take a continuously reduced structure. The sulfonated equivalent at a position of 5 μm from the membrane surface is 80% or less with respect to the sulfonated equivalent of the membrane surface (that is, the nearer surface) existing 5 μm from the position. Preferably it is 70% or less, More preferably, it is 60% or less.
This state will be specifically described. As shown in (1), there is no interface where the sulfonated equivalent changes discontinuously at least in the region of 5 μm from the surface layer toward the inside. That is, it means that the layer structure is not taken in the thickness range of 5 μm from both surfaces. The inside may have a layer separated by an interface where the sulfonic acid group equivalent becomes discontinuous, or may have a structure in which the sulfonic acid group equivalent continuously changes.

In the region from the surface to the inside up to 5 μm in the thickness direction, the sulfonic acid group equivalent is reduced to 80% or less of the sulfonic acid group equivalent on the outermost surface. The sulfonic acid group may be further decreased or increased toward the inside. That is, it means that a region where the sulfonic acid group equivalent decreases to 80% or less from the surface to the inside exists within a range of 5 μm from the surface. Preferably it is 70% or less, More preferably, it is 60%.
In both cases (1) and (2), a portion having a high sulfonic acid group equivalent contributes to ionic conductivity, and a low portion contributes to membrane strength and durability.

If the sulfonic acid group equivalent on the surface of the electrolyte membrane is set high relative to the adjacent interior, the sulfonic acid groups present on the outermost surface will increase and the hydrophilicity will increase, and it will have appropriate swelling and stretching properties. Adhesiveness with the electrode catalyst layer is improved. On the other hand, the site | part with low internal ion conductivity functions as a layer which improves the dimensional stability of a film | membrane and suppresses methanol permeation | transmission. However, if the ion conductivity itself becomes too low as a whole, the function as an electrolyte membrane cannot be exhibited. Therefore, the sulfonated equivalent of the entire membrane is preferably at least 0.3 milligram equivalent / g. More preferably, it is 0.5 milligram equivalent / g.
Moreover, about both surfaces, when ion conductivity is too high, since a polymer will become water-soluble, it will become easy to produce peeling of an electrode and an electrolyte membrane. Therefore, it is preferable that the sulfonated equivalent of the polymer electrolyte in the region from both membrane surfaces to 1 μm toward the inside is 5 milligram equivalent / g or less. More preferably, it is 4 milligram equivalent / g or less, More preferably, it is 3 milligram equivalent / g or less.

A method for measuring the ratio of the sulfonated equivalent of the surface of the molded membrane to the inside is described below. (1) Infrared absorption measurement of sulfonic acid group With respect to the cross section in the thickness direction of the electrolyte membrane, infrared absorption was measured for the outermost surface portion and the inner portion of 5 μm therefrom. The absorbance of the peak at 1180 to 1240 cm ⁻¹ derived from O stretching vibration is compared.
When microscopic IR is used, the film cross section is measured. When using ATR, the surface of the part to be measured is measured. For the inside of the film, the surface is polished or cut by a plane parallel to the film surface, and the measurement / surface is exposed.
The measurement position is preferably performed at the following location. Intersection of (n + 1) equally divided line so that the electrolyte membrane has a width equal to n, and (m + 1) equally divided line so as to have a width of m equally (m ≧ 2) in the direction perpendicular to it Measure at the position. In this case, the number of measurement locations is (m × n), and a minimum of 4 locations.

(2) EDX (energy dispersive X-ray fluorescence) analysis for metal-substituted sulfonic acid groups Abundance of sulfonic acid groups by binding metal to sulfonic acid groups by an acid-base reaction and measuring the concentration of the metal Ask for. The base is preferably one having high solubility in water, high reactivity, easy handling, and inexpensive compounds. Specifically, it is a metal hydroxide or ammonium salt having a valence of 1, and Li, Na, and K are preferred as the metal species.
First, an aqueous metal solution is prepared. The concentration is 1 mol / l or more. Next, the film to be measured is cut to expose the cross section. The number of cuts conforms to the measurement position in (1). And a test piece is immersed in the said metal compound aqueous solution, and the sulfonic acid group which exists in the exposed site | part is made to react with a metal. The reaction is carried out at room temperature for at least 3 hours. Further, the immersion is performed so that the cut surface is sufficiently immersed in the aqueous solution. When the reaction is completed, the cut piece is taken out, washed with water, and vacuum-dried. And the EDX profile of the metal seed | species exchanged with the proton of the sulfonic acid group is measured with respect to the thickness direction of a cross section. The measurement position and measurement location conform to the measurement position of (1). Since this profile is continuously measured with respect to the cross section of the film, it becomes clear whether the film has a layered structure or a continuously changed structure. From the measured numerical value of this profile, the ratio of the sulfonic acid group in the part of the membrane surface and the part inside from 5 μm is obtained.

The method for measuring the sulfonated equivalent of the entire membrane is to dissolve the electrolyte membrane itself or the entire electrolyte membrane taken out from the electrode, or to make it uniform as a powder, and titrate the sulfonic acid groups on this material.
By measuring the infrared absorption spectrum of the entire membrane, a calibration curve for the sulfonated equivalent weight of the same membrane material and the absorbance of the sulfonic acid group peak can be created. From the absorbance, it is possible to calculate the sulfonated equivalent of the site. The same applies to the analysis by EDX.
The infrared absorption spectrum of the entire film is measured by dissolving the entire film and drying it, or using a uniformed powder.

<Materials included in electrolyte membrane>
The polymer electrolyte membrane of the present invention has regions having different sulfonate oxidation equivalents, and the materials used in each region include the following combinations.
(1) A combination of polymer electrolytes having the structure of the present invention, which differ only in the sulfonic oxidation equivalent.
(2) A combination of a polymer electrolyte having the structure of the present invention and a polymer having a different structure.

In the case of (1), it is a polymer electrolyte obtained by changing the introduction amount when introducing a sulfonic acid group into the polymer having the structure of the above general formula (1) of the present invention. The amount introduced is adjusted by changing the reaction conditions and the amount of the sulfonic acid oxidation.
In the case of (2), the polymer having the structure of the above general formula (1) of the present invention is necessarily included in any part of the membrane, and has a structure in which other types of polymers coexist. Yes. The polymer that can be used is one that can form a film and has water resistance. Specifically, polyolefin, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyacrylic acid, polyacrylamide, polyamide, polyimide, polybenzimidazole, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether (ether) ketone, polyarylene Ethers and the like.

  By directly introducing sulfonic acid groups into these polymers, they can have ion exchange properties, or these polymers can be used as a support as a porous membrane, woven fabric, or unemployed fabric, and their pores. In addition, there is a method of forming a membrane having ion exchange properties by filling a polymer having a sulfonic acid group. A microporous membrane of polyolefin or polytetrafluoroethylene is suitable for use as a support from the viewpoint of heat resistance and chemical stability. A polymer in which a sulfonic acid group is introduced into polystyrene or polyacrylamide is suitable for use as an ion-exchangeable polymer that fills the pores.

<Method for producing membrane>
There are the following methods for producing the film of the present invention.
(1) A coating solution in which a polymer electrolyte is dissolved in an organic solvent is prepared. A polymer electrolyte solution to be the outermost surface is applied on the electrode surface or the release film, and a polymer electrolyte solution to be an adjacent layer is applied thereon to form a required number of layers. When the next layer is applied after the solvent is dried after coating, a film having a layer of sulfonated equivalents can be formed by laminating without drying.
(2) Polymer electrolyte membranes having different sulfonate oxidation equivalents are prepared in advance. The preparation method may be a method of casting a polymer electrolyte solution into which a sulfonic acid group is introduced as in (1), or a sulfonic acid group with respect to a polymer film having no sulfonic acid group introduced A group may be introduced to form an electrolyte membrane. These films are laminated and bonded by hot pressing.

  (3) A polymer having a high sulfonic acid equivalent is filled into pores of a polymer microporous membrane, woven fabric, or nonwoven fabric having no sulfonic acid group introduced or having a low sulfonic acid equivalent. A polymer solution having a high sulfonation equivalent used for filling is applied to both surfaces of the porous membrane to form a laminate in which the filled microporous membrane forms the central layer. In a similar manner, a polymer fiber having no sulfonic acid group introduced or having a low sulfonated equivalent is dispersed in a polymer having a high sulfonated equivalent to form a membrane, and the fiber is in the center. There is also a method in which a polymer layer having a high sulfonation equivalent is present on both sides. Furthermore, these films may be stacked.

<Method for producing electrode>
The fuel cell has a structure in which a proton conductive membrane as an electrolyte is sandwiched between two electrodes (an oxygen electrode and a fuel electrode). Each electrode has a catalyst layer formed on the surface in contact with the proton conductive membrane, and a diffusion layer and then a separator are laminated on the catalyst layer.
As the catalyst, catalyst particles in which platinum is supported on carbon black at a predetermined weight ratio are generally used. The carbon black is ketjen black, acetylene black or the like, and 10 to 30% by weight of platinum is supported on the carbon black. In order to form a catalyst layer, catalyst particles are dispersed in an ion conductive polymer to form a slurry, which is formed by applying and drying on a base layer. It is preferable that the amount of platinum contained is 0.5 to 0.8 mg / cm ² .

The diffusion layer is usually composed of carbon paper and an underlayer. For example, a slurry in which carbon black mixed with a predetermined weight ratio and polytetrafluoroethylene (PTFE) are uniformly dispersed in an organic solvent such as ethylene glycol is applied to one or both sides of the carbon paper and dried. It is formed by doing.
In order to create a membrane-electrode assembly (MEA) for a fuel cell, a polymer electrolyte membrane solution and a slurry of electrode material are sequentially applied and laminated, or a membrane is formed in advance, There are methods such as superposition and heat and pressure bonding. These methods may be combined.

The present invention will be described based on examples. The numerical value of each measurement item was obtained in the following manner.
Number average, weight average molecular weight: The number average molecular weight and the weight average molecular weight of the precursor polymer before sulfonation were determined using polystyrene (THF) as a solvent and the molecular weight in terms of polystyrene by gel permeation chromatography (GPC). .
Sulfonation equivalent: Thoroughly wash the resulting polymer with water until it becomes neutral, and after drying, weigh a predetermined amount, dissolve in a THF / water mixed solvent, use phenolphthalein as an indicator, and use NaOH. The sulfonated equivalent was determined from the neutralization point.
Proton conductivity: A film sample having a thickness of 40 to 60 μm placed under 100% relative humidity was sandwiched between platinum electrodes, and complex impedance measurement was performed to calculate proton conductivity.

Fenton test: A Fenton reagent was prepared so that the hydrogen peroxide concentration was 3% by weight and the ferric sulfate heptahydrate concentration was 20 ppm. 200 g of Fenton reagent was collected in a 250 cc polyethylene container, a polymer electrolyte membrane cut to 3 cm × 4 cm and a film thickness of 40 to 60 μm was added, sealed, and then immersed in a constant temperature water bath at 50 ° C. for 6 hours. A test was conducted. After the Fenton test, the film was taken out, washed with ion-exchanged water, kept at 25 ° C. and 50% RH for 24 hours to adjust the humidity, and weighed. The weight retention rate in the Fenton test was calculated by the following mathematical formula.
Weight retention in Fenton test (%) = (film weight after Fenton test / film weight before Fenton test) × 100

Methanol permeability test: A polymer electrolyte film was prepared, and the film was attached to the mouth of a cup in which calcium chloride was placed in an opening area of 50 mmφ, and 10 ml of methanol was dropped on the film, and a constant temperature and humidity chamber ( (25 ° C., 50% relative humidity) for 60 minutes. Thereafter, the weight increase amount of calcium chloride in the cup was measured, and the methanol permeation amount per 1 m ² of the membrane area was calculated as the methanol amount permeated therethrough.
First, a method for synthesizing the polymer electrolyte used in the examples will be described.

<Synthesis Method of Polymer Electrolyte 1>
(1) Synthesis of 2,5-dichloro-4 ′-(4-thiophenoxy) thiophenoxybenzophenone [Formula (43)] 2,5-dichloro-4′-fluorobenzophenone 10.8 g (40 mmol), 4-phenyl 8.7 g (40 mmol) of sulfanylthiophenol and 8.29 g (60 mmol) of potassium carbonate were placed in a three-necked flask equipped with a Dean-Stark tube, a condenser tube, and a thermometer, and a mixed solvent of 50 g of dimethylacetamide and 50 g of toluene was poured and stirred. Next, the temperature was raised to 130 ° C., and water produced was removed while heating under reflux. Furthermore, it was made to react at 150 degreeC for 4 hours, removing toluene out of the system. After confirming the completion of the reaction by TLC, the contents were cooled to room temperature, poured into water and stirred for 1 hour. The organic matter was separated from the mixture solution, and extracted with ethyl acetate. The extract layer was washed with water and brine, and then dried over anhydrous magnesium sulfate. After the inorganic salt was filtered off, the solvent was distilled off to obtain a crude product. Recrystallization was performed with a mixed solvent of ethyl acetate: n-hexane = 1: 5 (volume ratio) to obtain the desired product in a yield of 85% (15.8 g).

(2) Synthesis of bis [4- [4- (4-chlorophenylsulfonyl) phenoxy] phenyl] sulfone (2-1) Synthesis of 4-chlorophenyl-4′-fluorophenylsulfone 192 g (2.0 mol) of fluorobenzene and chloride 69.5 g (520 mmol) of aluminum was placed in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and the atmosphere was replaced with nitrogen. The mixture was stirred with a mechanical stirrer while being cooled to 10 ° C. with ice water. 4-Chlorobenzenesulfonyl chloride (84.4 g, 400 mmol) was added dropwise using a dropping funnel over 30 minutes, and the mixture was stirred at room temperature for 4 hours. The reaction mixture was poured into an aqueous solution of concentrated hydrochloric acid: ice = 1: 10 and stirred for 1 hour. The mixture was extracted with ethyl acetate, and the organic layer was washed with 5% aqueous sodium hydrogen carbonate solution, water and saturated brine. The organic layer was dried over anhydrous magnesium sulfate, then ethyl acetate was distilled off under reduced pressure, and recrystallized with a mixed solvent of hexane: ethyl acetate. The formation of the target product was confirmed by NMR and IR spectra. Yield 85% (92.0 g).
(2-2) Synthesis of bis [4- [4- (4-chlorophenylsulfonyl) phenoxy] phenyl] sulfone [Formula (44)]

Bis (4-hydroxyphenyl) sulfone (bisphenol S) 25.0 g (100 mmol), potassium carbonate 30.4 g (220 mmol), dimethylacetamide 100 ml, toluene 50 ml, thermometer, Dean-Stark tube, reflux tube, three-way cock The flask was placed in a three-necked flask and purged with nitrogen. Stirring while raising the temperature to 130 ° C. in an oil bath, water and toluene produced by the reaction were azeotroped and removed with a Dean-Stark tube. When no more water was observed, the temperature was raised to 150 ° C. and toluene was distilled off. After the reaction solution was cooled to 80 ° C., 67.6 g (250 mmol) of 4-chlorophenyl-4′-fluorophenylsulfone was added and stirred at 110 ° C. for 7 hours. After the inorganic salt as a by-product was removed by filtration, the filtrate was put into 500 ml of methanol, and the precipitate was filtered and recrystallized from toluene. The formation of the target product was confirmed by NMR and IR spectra. Yield 71% (51.0 g).

(3) Synthesis of polymer electrolyte (3-1) Polymerization 25.17 g (35.0 mmol) of bis [4- [4- (4-chlorophenylsulfonyl) phenoxy] phenyl] sulfone obtained above, 2,5- Dichloro-4 '-(4-thiophenoxy) thiophenoxybenzophenone 16.3 g (35.0 mmol), bis (triphenylphosphine) nickel dichloride 1.43 g (2.2 mmol), sodium iodide 1.37 g (9. 14 mmol), 7.73 g (29.5 mmol) of triphenylphosphine and 11.3 g (172 mmol) of zinc powder were placed in a reaction vessel, and the inside of the system was replaced with dry nitrogen. Polymerization was carried out by adding 0.2 liter of N-methyl-2-pyrrolidone (NMP), heating to 80 ° C., and stirring for 4 hours. After the polymerization, the reaction solution is diluted with tetrahydrofuran (THF), and a polymer is recovered by adding a mixture of hydrochloric acid and methanol. Then, washing with methanol is repeated four times, and the polymer dissolved in THF is re-recovered with methanol. The polymer purified by precipitation and filtered off was vacuum dried to give 34.7 g (95%) of the desired polymer. The number average molecular weight in terms of polystyrene determined by GPC (THF) was 40,000, and the weight average molecular weight was 145,000.

(3-2) Sulfonation of polymer 20.0 g of the polymer obtained above was put into a 0.5 liter reaction solution, 0.25 liter of 96% sulfuric acid was added, and stirring was continued at room temperature under nitrogen for 2 days. It was. The resulting solution was poured into 5 liters of ion exchange water to precipitate the polymer. The polymer was repeatedly washed with water until the pH of the cleaning solution reached 5. Drying gave 23.7 g (95%) of a sulfonated polymer.
(3-3) Oxidation of sulfonated polymer 20.0 g of the sulfonated polymer obtained above was placed in a 2 liter glass reaction vessel, 0.8 liter of acetic acid and 200 g of 34% aqueous hydrogen peroxide were added, The temperature was gradually raised while stirring, and the reaction was continued at 90 ° C. for 6 hours. After the reaction, the mixture was allowed to cool, and the polymer was filtered off, washed with water, and dried in vacuo to obtain 19.6 g (92%) of the desired polymer electrolyte [sulfone oxide of formula (45)]. By structural analysis, it was confirmed that a plurality of sulfonic acid groups were introduced into the side chain per side chain. This is referred to as polymer electrolyte 1.

<Synthesis Method of Polymer Electrolyte 2>
(1) Synthesis of 2,5-dichloro-4′-thiophenoxybenzophenone [Formula (46)] A polymer electrolyte was used except that 4.4 g (40 mmol) of thiophenol was used instead of 4-phenylsulfanylthiophenol. Using the same method as the synthesis of 2,5-dichloro-4 ′-(4-thiophenoxy) thiophenoxybenzophenone described in the synthesis method 1, the target product was obtained in a yield of 83% (11.9 g). .

(2) Synthesis of 4,4′-bis [4- (4-chlorobenzoyl) phenoxy] benzophenone (2-1) Synthesis of 4-chloro-4′-fluorobenzophenone 4-chlorobenzene instead of 4-chlorobenzenesulfonyl chloride A desired compound was obtained using the same method as the synthesis of polymer electrolyte 1 except that 70.0 g (400 mmol) of benzoyl chloride was used. The structure was confirmed by NMR and IR spectra. Yield 79% (74.1 g).
(2-2) Synthesis of 4,4′-bis [4- (4-chlorobenzoyl) phenoxy] benzophenone [Formula (47)] 4-Chloro-4′-fluoro instead of bis (4-hydroxyphenyl) sulfone A desired compound was obtained using the same method as the synthesis of polymer electrolyte 1 except that 58.6 g (250 mmol) of benzophenone was used. The structure was confirmed by NMR and IR spectra. Yield 75% (48.2 g).

(3) Synthesis of polyelectrolyte (3-1) Polymerization Instead of bis [4- [4- (4-chlorophenylsulfonyl) phenoxy] phenyl] sulfone, 4,4′-bis [4- (4-Chlorobenzoyl) phenoxy] benzophenone 22.5 g (35.0 mmol) was used instead of 2,5-dichloro-4 ′-(4-thiophenoxy) thiophenoxybenzophenone. 30.6 g (94%) of the desired polymer was obtained using the same method as in the polymer electrolyte 1 except that 12.6 g (35.0 mmol) of thiophenoxybenzophenone was used. The number average molecular weight was 44,000, and the weight average molecular weight was 150,000.

(3-2) Sulfonation of Polymer A sulfonated polymer was obtained using the same method as the synthesis of polymer electrolyte 1 except that the polymer obtained above was used (yield 96%).
(3-3) Oxidation of Sulfonated Polymer Using the same method as the synthesis of polymer electrolyte 1 except that the sulfonated polymer obtained above was used, the desired polymer electrolyte [sulfon oxidation of formula (48) Product] (92%). Structural analysis confirmed that 2.6 sulfonic acid groups were introduced per side chain. This is referred to as polymer electrolyte 2.

<Synthesis Method of Polymer Electrolyte 3>
(1) Synthesis of 2,5-dichlorophenyl-4′-thiophenylbenzene sulfide [Formula (49)] Quinoline (0.5 liter) stirred under nitrogen and 1,2,4-trichlorobenzene 36 g (0 0.1 mol) of sodium 4-phenylsulfanylthiophenolate (120 g, 0.5 mol) was added. The temperature was raised with stirring, and the mixture was stirred at a reaction temperature of 160 ° C. for 3 hours. The reaction mixture was poured into water, extracted with diisopropyl ether, and then the solvent was removed to obtain the desired product. Yield 90% (65.3 g).

(2) Synthesis of polymer electrolyte (2-1) Polymerization 25.0 g (100 mmol) of bis (4-hydroxyphenyl) sulfone, 30.4 g (220 mmol) of potassium carbonate, 0.1 liter of dimethylacetamide and 0.05 liter of toluene Was placed in a three-necked flask equipped with a thermometer, Dean-Stark tube, reflux tube, and three-way cock, and purged with nitrogen. Stirring while heating in an oil bath at 130 ° C., water produced by the reaction was azeotroped with toluene and separated from the reaction system with a Dean-Stark tube. When water no longer formed, the oil bath temperature was set to 150 ° C. and toluene was distilled off. After cooling the reaction solution to 80 ° C., 36.3 g (100 mmol) of 2,5-dichlorophenyl-4′-thiophenylbenzene sulfide was added and stirred at an oil bath temperature of 150 ° C. for 20 hours. The inorganic salt as a by-product was separated by filtration, the filtrate was poured into 2 liters of methanol, the precipitate was filtered, washed with methanol, and vacuum dried to obtain the desired polymer (yield 87%). . The number average molecular weight was 48,000, and the weight average molecular weight was 150,000.

(2-2) Sulfonation of polymer A sulfonated polymer was obtained using the same method as the synthesis of polymer electrolyte 1 except that the polymer obtained above was used (yield 95%).
(3-3) Oxidation of Sulfonated Polymer Using the same method as the synthesis of polymer electrolyte 1 except that the sulfonated polymer obtained above was used, the desired polymer electrolyte [sulfon oxidation of formula (50) Product] (94%). Structural analysis confirmed that 2.1 sulfonic acid groups per side chain were introduced into the side chain. This is referred to as polymer electrolyte 3.

<Synthesis Method of Polymer Electrolyte 4>
(1) Synthesis of polyelectrolyte (1-1) Polymerization 4,4′-Dihydroxybenzophenone was used instead of bis (4-hydroxyphenyl) sulfone, and 2,5-dichlorophenyl-4′-thiophenylbenzene sulfide was used. Instead of 2,5-dichloro-4 ′-(4-thiophenoxy) thiophenoxybenzophenone, the target polymer was obtained in the same manner as the polymerization in the polymer electrolyte 3 synthesis method (yield 92 %). The number average molecular weight was 51,000 and the weight average molecular weight was 160,000.

(1-2) Sulfonation of polymer A sulfonated polymer was obtained using the same method as the synthesis of polymer electrolyte 1 except that the polymer obtained above was used (yield 95%).
(1-3) Oxidation of Sulfonated Polymer Using the same method as the synthesis of polymer electrolyte 1 except that the sulfonated polymer obtained above was used, the desired polymer electrolyte [sulfon oxidation of formula (51) Product] (92%). By structural analysis, it was confirmed that 1.9 sulfonic acid groups per side chain were introduced into the side chain. This is referred to as polymer electrolyte 4.

<Synthesis Method of Polymer Electrolyte 5>
(1) Synthesis of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [Formula (52)]

In a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, 20.0 g (108 mmol) of diphenyl sulfide and 35 ml of chloroform were placed, and the inside of the system was replaced with dry nitrogen. This solution was cooled to 5 ° C. with ice water, and 25.1 g (215 mmol) of chlorosulfuric acid was slowly added dropwise. When the reaction solution was stirred at 5 ° C. for 3 hours, a white solid was precipitated. After confirming that all of the diphenyl sulfide had reacted by thin layer chromatography, 25.6 g (215 mmol) of thionyl chloride was slowly added dropwise. After refluxing for 90 minutes, the solvent chloroform was distilled off and vacuum dried. Yield: 96% (37.8 g)
(2) Synthesis of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [Formula (52)] into polyethersulfone [Synthesis of the following Formula (53)]

  Polyethersulfone (manufactured by Solvay Advanced Polymers, Radel A-200) 2.0 g and nitrobenzene 30 ml were placed in a reaction vessel, and the system was replaced with dry nitrogen while heating and dissolving at 60 ° C. To this polymer solution, 6.28 g (17.24 mmol) of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [Formula (52)] was added and dissolved. To this solution, 2.54 g (18.80 mmol) of aluminum chloride was added little by little and stirred at 80 ° C. for 20 hours. The reaction solution was added to 500 ml of a mixed solution of methanol: hydrochloric acid = 10: 1, and the precipitated solid was stirred while being pulverized. The solid was filtered, washed several times with methanol, and dried in vacuo at 80 ° C. The yield was 2.22g.

(3) Sulfonation was performed by the same method as the synthesis method of the polymer electrolyte 1 except that the solid obtained above (formula (53)) was used.
(4) Oxidation reaction [synthesis of formula (54)]
Into a two-necked flask equipped with a thermometer, 1.0 g of the polymer described in the formula (53) subjected to side chain introduction reaction and 20 ml of acetic acid were added. To this mixture, 1000 mg (9.0 mmol) of 30% aqueous hydrogen peroxide was added and refluxed for 3 hours. The solid in the system was suction filtered, washed with water, and vacuum dried at 100 ° C. From NMR and IR, it was confirmed that the side chain sulfide was converted to sulfone. It was also confirmed that a plurality of sulfonic acid groups per side chain were introduced into the side chain. Yield was 880 mg. This is referred to as polymer electrolyte 5.

<Synthesis Method of Polymer Electrolyte 6>
(1) Introduction reaction of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [formula (52)] to polyethersulfone (2)
The polymer was synthesized by the same method as described in (2) of the method for synthesizing polymer electrolyte 1 except that the stirring temperature was 90 ° C. and the stirring time was 40 hours.
(2) Oxidation reaction An oxidation reaction was performed in the same manner as described in (3) of the synthesis method of the polymer electrolyte 1. This is referred to as a polymer electrolyte 6.

<Synthesis Method of Polymer Electrolyte 7>
(1) Synthesis of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [formula (52)] into polyetherethersulfone [Synthesis of the following formula (55)] Polyetherethersulfone (manufactured by Aldrich) 3. 0 g and 60 ml of nitrobenzene were placed in a reaction vessel, and the inside of the system was replaced with dry nitrogen while heating and dissolving at 60 ° C. In this polymer solution, 3.50 g (37 mmol) of 4- (4′-sulfonylphenylthio) benzenesulfonyl chloride [Formula (52)] was added and dissolved. To this reaction solution, 5.44 g (40.8 mmol) of aluminum chloride was added little by little and stirred at 90 ° C. for 40 hours. The reaction solution was added to 500 ml of a mixed solution of methanol: hydrochloric acid = 10: 1, and the precipitated solid was stirred while being pulverized. The solid was filtered, washed several times with methanol, and vacuum dried at 80 ° C. to obtain a polymer (formula (55)) with a yield of 4.36 g.

(2) Sulfonation was performed using the same method as the synthesis of polymer electrolyte 1 except that the polymer obtained above (formula (55)) was used.
(3) Oxidation reaction [synthesis of formula (56)]

The oxidation reaction was performed by the same method as (3) of the method of synthesizing the polymer electrolyte 1. It was confirmed that 1.6 sulfonic acid groups were introduced into the side chain per side chain. This is referred to as polymer electrolyte 7.
<Synthesis Method of Polymer Electrolyte 8>
Introduction of branched side chains into polyethersulfone (1) Synthesis of bis (thiophenoxy) benzenesulfonyl chloride (formula (57)) 1,4-dibromobenzene in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock 50 g (212 mmol) and 16 ml of chloroform were added, and the inside of the system was replaced with dry nitrogen. To this was slowly added dropwise 27.2 g (233 mmol) of chlorosulfuric acid dissolved in 100 ml of chloroform at room temperature. A reaction tube was attached for 4 hours at room temperature, and a reaction was performed for 10 hours under reflux of chloroform. After confirming that all 1,4-dibromobenzene had reacted by thin layer chromatography, chloroform and chlorosulfuric acid were distilled off under reduced pressure for purification to obtain 56.9 g (180 mmol) of dibromobenzenesulfonic acid ( Yield 85%). Next, 3.5 g (79 mmol) of thiophenol was put into a three-necked flask equipped with a Dean-Stark tube, a condenser tube, and a thermometer, and 4.5 g of potassium hydroxide, 25 ml of N, N-dimethylacetamide and 25 ml of toluene were added and stirred with a stirrer. did. The temperature was raised to 150 ° C., and water produced was removed while heating under reflux. To this, 7.1 g (23 mmol) of dibromobenzenesulfonic acid was added and reacted at 160 ° C. for 4 hours. After confirming the completion of the reaction by thin layer chromatography, the organic substance was separated from the mixture solution and purified by recrystallization to obtain 7.2 g of bis (thiophenoxy) benzenesulfonic acid (yield 84%). ). This is put into a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and 100 ml of chloroform is added and dissolved. 5. Thionyl chloride (2.1 g, 21.2 mmol) was slowly added dropwise with a dropping funnel and refluxed for 90 minutes, after which chloroform was distilled off and dried under vacuum to give bis (thiophenoxy) benzenesulfonyl chloride (formula (57)). 4 g was obtained (yield 85%).

(2) Synthesis reaction of introduction of bis (thiophenoxy) benzenesulfonyl chloride (formula (57)) into polyethersulfone (formula (58) below) Polyethersulfone (Solvay Advanced Polymers, Radel A-200) 2 0.0 g and 30 ml of nitrobenzene were placed in a reaction vessel, and the system was replaced with dry nitrogen while heating and dissolving at 60 ° C. To this polymer solution, 6.70 g (17.08 mmol) of bis (thiophenoxy) benzenesulfonyl chloride (formula (57)) was added and dissolved. To this solution, 2.54 g (18.96 mmol) of aluminum chloride was added little by little and stirred at 80 ° C. for 20 hours. The reaction solution was added to 500 ml of a mixed solution of methanol: hydrochloric acid = 10: 1, and the precipitated solid was stirred while being pulverized. The solid was filtered, washed several times with methanol, and vacuum dried at 80 ° C. to obtain polyethersulfone (formula (58)) into which side chains were introduced. The yield was 2.31 g.

(3) Sulfonation thermometer of side chain group, dripping funnel, three-necked flask equipped with a three-way cock, 2.00 g of the polymer of formula (58) and 16 ml of chloroform introduced into the side chain, and the system was replaced with dry nitrogen did. To this, 4.0 g (40 mmol) of chlorosulfuric acid dissolved in 100 ml of chloroform at room temperature was slowly added dropwise. A reaction tube was attached for 4 hours at room temperature, and the reaction was carried out for 10 hours under reflux of chloroform. After confirming that all starting polymers reacted by thin layer chromatography, chloroform and chlorosulfuric acid were distilled off under reduced pressure and purified to effect side chain introduction sulfonated product (formula (59)) 2.03 g was obtained.

(4) Oxidation reaction A two-necked flask equipped with a thermometer was charged with 1.0 g of a polymer described in Formula (59) and 20 ml of acetic acid obtained by introducing a side chain and sulfonated. To this mixture, 1000 mg (9 mmol) of 30% aqueous hydrogen peroxide was added and refluxed for 3 hours. The solid in the system was suction filtered, washed with water, and vacuum dried at 100 ° C. to obtain the final target electrolyte polymer (formula (60)). From NMR and IR, it was confirmed that the side chain sulfide was converted to sulfone. The yield was 0.87g. It was confirmed that a plurality of sulfonic acid groups were introduced per side chain. This is referred to as polymer electrolyte 8.

<Synthesis Method of Polymer Electrolyte 9>
Introduction of long branched side chain into polyether sulfone (1) Synthesis thermometer of 4-thiophenoxybenzene sulfide, dripping funnel, 3-bromo-1-fluorobenzene 50.0 g (286 mmol) in a three-necked flask equipped with a three-way cock , 300 ml of N, N-dimethylformamide was added, and 22.0 g (314 mmol) of sodium thiomethylate dissolved in 100 ml of N, N-dimethylformamide was slowly dropped with a dropping funnel and stirred at 20 ° C. for 100 hours to react. I let you. After confirming that all of the 3-bromo-1-fluorobenzene had reacted by thin layer chromatography, the organic substance was separated from the mixture solution and purified by recrystallization to give 4-bromophenylmethyl sulfide 49. 3 g (243 mmol) were obtained. Next, 45.0 g (222 mmol) of 4-bromophenyl methyl sulfide, 15.5 g of copper oxide and 240 ml of pyridine 60 ml of quinoline were placed in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and 26.8 g (244 mmol) of thiophenol. Was dissolved and dispersed in 20 ml of pyridine in 80 ml of quinoline and added with a dropping funnel, and the mixture was reacted at 150 ° C. for 40 hours. After confirming the completion of the reaction by thin layer chromatography, the organic substance was separated from the mixture solution and purified by recrystallization to obtain 43.8 g (189 mmol) of 4-thiophenoxyphenyl methyl sulfide. Subsequently, 40.0 g (172 mmol) of 4-thiophenoxyphenyl methyl sulfide obtained and 300 ml of N, N-dimethylformamide were placed in a three-necked flask equipped with a thermometer and a condenser tube, and 21.3 g (190 mmol) of sodium thio t-butylate was added. ) Was dissolved in 300 ml of N, N-dimethylformamide and added with a dropping funnel, and the mixture was reacted at 150 ° C. for 4 hours. After confirming the completion of the reaction by thin layer chromatography, organic substances were separated from the mixture solution and purified by recrystallization to obtain 32.2 g (148 mmol) of 4-thiophenoxybenzene sulfide (yield 86). %).

(2) Synthesis of long-branched sulfide In the same manner as in (1), except that 30.0 g (138 mmol) of 4-thiophenoxybenzene sulfide obtained in (1) was used instead of thiophenol, a long-branched sulfide (formula (61)) 31.0 g was obtained (yield 83%).

(3) Sulfonation reaction thermometer, dripping funnel, three-necked flask with a three-way cock were charged with 31.0 g (57.2 mmol) of long-branched sulfide (formula (61)) and 200 ml of chloroform, and the system was replaced with dry nitrogen. did. To this was slowly added dropwise 7.34 g (63.0 mmol) of chlorosulfuric acid dissolved in 100 ml of chloroform at room temperature. A reaction tube was attached for 4 hours at room temperature, and the reaction was carried out for 10 hours under reflux of chloroform. After confirming that all the starting polymers had reacted by thin layer chromatography, chloroform and chlorosulfuric acid were distilled off under reduced pressure for purification to obtain 36.1 g of a sulfonated product of long branched sulfide (formula (62)). (Yield 90%).

(4) Oxidation reaction A two-necked flask equipped with a thermometer was charged with 36.0 g (51.3 mmol) of a sulfonated product of a long-branched sulfide and 200 ml of acetic acid. To this mixture, 116 g (1.03 mmol) of 30% aqueous hydrogen peroxide was added and refluxed for 3 hours. The solid in the system was suction filtered, washed with water, and vacuum dried at 100 ° C. to obtain 42.8 g of a sulfonated product of long branched sulfone (formula (63)) (yield 95%).

(5) Chlorination 30.0 g (34.2 mmol) of a sulfonated product of long-branched sulfone (formula (63)) is placed in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and 100 ml of chloroform is added and dissolved. . 3.74 g (37.6 mmol) of thionyl chloride was slowly added dropwise with a dropping funnel, refluxed for 90 minutes, chloroform was distilled off and vacuum-dried, and 27.0 g of sulfonyl chloride of a long-branched sulfone (formula (64)). (Yield 88%).

(6) Reaction of introduction of sulfonyl chloride of long-branched sulfone into polyethersulfone The sulfonyl chloride of long-branched sulfone is used in place of the bis (thiophenoxy) benzenesulfonyl chloride of (2) in the synthesis method of the polymer electrolyte 8. In the same manner as above, polyethersulfone (formula (65)) having a long-branched sulfone side chain was obtained. The yield was 2.05g. This is referred to as polymer electrolyte 9.

<Synthesis Method of Polymer Electrolyte 10>
Introduction of multi-branched side chains into polyethersulfone (1) Synthesis of bis (3,5-thiophenoxy) benzene sulfide 3,5-dibromo-1-fluoro in a three-necked flask equipped with a thermometer, dripping funnel and three-way cock Benzene (50.0 g, 197 mmol) and N, N-dimethylformamide (300 ml) were added, sodium thiomethylate (15.2 g, 217 mmol) dissolved in N, N-dimethylformamide (100 ml) was slowly added dropwise with a dropping funnel at 20 ° C. For 4.5 days with stirring. After confirming that all 3,5-dibromo-1-fluorobenzene had reacted by thin layer chromatography, the organic substance was separated from the mixture solution, purified by recrystallization, and 3,5-dibromophenyl 48.3 g (171 mol) of methyl sulfide was obtained (yield 87%). Next, 45 g (160 mmol) of 3,5-dibromophenylmethyl sulfide, 22.4 g of copper oxide, and 240 ml of quinoline 240 ml of pyridine were put into a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and 38.7 g (352 mmol) of thiophenol. Was dissolved and dispersed in 20 ml of pyridine in 80 ml of quinoline and added with a dropping funnel, and the mixture was reacted at 150 ° C. for 40 hours. After confirming the completion of the reaction by thin layer chromatography, the organic substance was separated from the mixture solution and purified by recrystallization to obtain 45.7 g (134 mmol) of bis (3,5-thiophenoxy) phenyl methyl sulfide. Obtained. Subsequently, 40.0 g (118 mmol) of the obtained bis (3,5-thiophenoxy) phenylmethyl sulfide was placed in a three-necked flask equipped with a thermometer and a condenser, and 14.5 g (129 mmol) of sodium thio t-butylate was added to N , N-dimethylformamide dissolved in 300 ml was added with a dropping funnel and reacted at 150 ° C. for 4 hours. After confirming the completion of the reaction by thin layer chromatography, the organic substance was separated from the mixture solution and purified by recrystallization to obtain 33.1 g (101 mmol) of bis (3,5-thiophenoxy) benzene sulfide. (Yield 86%).

(2) Synthesis of multi-branched sulfide (formula (66)) In the synthesis (1), 30.0 g (92.0 mmol) of bis (3,5-thiophenoxy) benzene sulfide obtained in (1) instead of thiophenol 31.4 g of hyperbranched sulfide (Formula (66)) was obtained in the same manner except that it was used. (Yield 90%)

(3) 30.0 g (39.6 mmol) of a multi-branched sulfide (formula (66)) and 200 ml of chloroform are put into a three-necked flask equipped with a sulfonation reaction thermometer, a dropping funnel and a three-way cock, and the system is filled with dry nitrogen. Replaced. To this, 5.07 g (43.5 mmol) of chlorosulfuric acid dissolved in 100 ml of chloroform at room temperature was slowly added dropwise. A reaction tube was attached for 4 hours at room temperature, and a reaction was performed for 10 hours under reflux of chloroform. After confirming that all the raw material sulfides reacted by thin layer chromatography, chloroform and chlorosulfuric acid were distilled off under reduced pressure for purification to obtain 36.3 g of a sulfonated product of multi-branched sulfide (formula (67)). (Yield 85%).

(4) Oxidation reaction A two-necked flask equipped with a thermometer was charged with 36.0 g (33.4 mmol) of a sulfonated product of multi-branched sulfide and 200 ml of acetic acid. To this mixture, 114 g (1.00 mol) of 30% aqueous hydrogen peroxide was added and refluxed for 3 hours. The solid in the system was suction filtered, washed with water, and vacuum dried at 100 ° C. to obtain 39.6 g of a sulfonated product of multi-branched sulfone (formula (68)) (yield 90%).

(5) Chlorination 30.0 g (22.8 mol) of a sulfonated product of a multi-branched sulfone (formula (68)) is placed in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock, and 100 ml of chloroform is added and dissolved. . 2.49 g (25.0 mmol) of thionyl chloride was slowly added dropwise with a dropping funnel and refluxed for 90 minutes, after which chloroform was distilled off and dried under vacuum to obtain 27.1 g of a sulfonyl chloride of a multi-branched sulfone (formula (69)). (Yield 89%).

(6) Introduction reaction of sulfonyl chloride of multi-branched sulfone into polyether sulfone In the synthesis method (2) of polymer electrolyte 8, sulfonyl chloride of multi-branched sulfone is used instead of bis (thiophenoxy) benzenesulfonyl chloride In the same manner as above, polyethersulfone (formula (70)) having a side chain of a multi-branched sulfone was obtained. The yield was 2.10g. This is referred to as a polymer electrolyte 10.

[ Reference Example 1]
For the polymer electrolyte 1, a polymer having no sulfonic acid group was prepared except for the step of introducing a sulfonic acid group. This and the polymer electrolyte 1 were mixed at a ratio of polymer electrolyte 1: polymer without sulfonic acid = 2/1 (w / w) to prepare a polymer electrolyte 1 ′. The sulfonating equivalent of the polymer electrolyte 1 ′ is 66.7% with respect to the polymer electrolyte 1, and conversely, the sulfonating equivalent of the polymer electrolyte 1 is 150% with respect to the polymer electrolyte 1 ′.
Polymer electrolytes 1 and 1 ′ were dissolved in N-methyl-2-pyrrolidone (hereinafter referred to as NMP) so as to form a 30 wt% solution. The liquid was heated to 80 ° C. and completely dissolved.
On the glass substrate, the polymer electrolyte 1 ′ solution was applied so as to have a thickness of 5 μm after drying, and then dried in an 80 ° C. environment for 0.5 hours using a vacuum dryer.

Next, the polymer electrolyte 1 solution was applied onto the polymer electrolyte membrane 1 ′ so as to have a thickness of 5 μm after drying, and was dried in an 80 ° C. environment for 0.5 hours by a vacuum dryer. . After peeling off this membrane, the polymer electrolyte 1 solution was further applied to the back surface of the polymer electrolyte membrane 1 ′ so as to have a thickness of 5 μm after drying. .5 hours of drying Next, in the same manner as in the previous step, the polymer electrolyte 1 ′ solution was further laminated on the layer of the polymer electrolyte 1 so as to have a thickness of 5 μm after drying. Further, the polymer electrolyte 1 solution was further laminated so as to have a thickness of 5 μm after drying, and then vacuum dried at 100 ° C. for 3 hours to prepare an electrolyte membrane. As a result, five layers of electrolyte membranes each having a thickness of 5 μm (total thickness of 25 μm) were formed. The ratio of the sulfonated equivalent weight of the adjacent layer to the outermost surface is 150%. Further, a layer having the same sulfonic oxidation equivalent as the outermost surface is present in the central portion. Table 2 shows the results of the sulfonated equivalent of the membrane surface, the sulfonated equivalent of the entire membrane, proton conductivity, Fenton test weight retention, and methanol permeation amount of this polymer electrolyte membrane.

[ Reference Examples 2-7, Examples 8-10 ]
Using the polymer electrolytes 2 to 10, five-layer polymer electrolytes having the same polymer skeleton and different sulfonated equivalents were prepared in the same manner as in Reference Example 1. Table 2 shows the results of the sulfonated equivalent weight, proton conductivity, Fenton test weight retention rate, and methanol permeation amount of these polymer electrolyte membranes.
[Comparative Example 1]
Polyetheretherketone (ICI) and sulfonated polyetheretherketone [S-PEEK, formula (71)] obtained by sulfonating the same by the same method as the synthesis method of polymer electrolyte 1 were used. In accordance with the method of Reference Example 1, a three-layer electrolyte membrane was prepared. Table 2 also shows the results of the sulfonated equivalent weight, proton conductivity, Fenton test weight retention rate, and methanol permeation amount of this polymer electrolyte membrane.

[Comparative Example 2]
Obtained by sulfonating a polymer represented by the following formula (72) obtained by the method described in Reference Example 2 of JP-A-2003-20143 and the same method as the synthesis method of polymer electrolyte 1 The sulfonated oxide (wherein j / k = 6.9 and n is 5.5) was also evaluated as a membrane using the method of Reference Example 1. As above, the numerical values of the evaluation items are also shown in Table 2.
In both Comparative Examples 1 and 2, the Fenton test weight retention is low and the methanol permeation amount is not particularly good.

[Example 11]
The polymer electrolyte 11 was synthesized by the following method.
(1) Synthesis thermometer of TTBS3, dripping funnel, three-necked flask equipped with a three-way cock, 50.0 g (124 mmol) of 1,3,5-tris (phenylthio) -benzene (TTB) and 120 ml of sulfolane were placed in dry nitrogen. The system was replaced. The liquid temperature was kept at 70 ° C., 47.5 g (409 mmol) of chlorosulfuric acid was slowly added dropwise, and then the mixture was stirred for 1.5 hours. The reaction was confirmed by liquid chromatography [Agilent 100 series, column: GL Science, Inertsil ODS-3, mobile phase: 10 M ammonium formate / acetonitrile, UV detection wavelength: 254 nm]. A mixture containing 53 g of TTB trisulfonate [TTBS3, formula (73)] was obtained (yield 67%).

(2) Synthesis of TTBS3C The above mixture containing TTBS3 was placed in a three-necked flask equipped with a thermometer, a dropping funnel and a three-way cock. The liquid temperature was kept at 70 ° C., and 12.4 g (124 mmol) of thionyl chloride was slowly dropped from the dropping funnel, followed by stirring for 2 hours. The reaction was confirmed by liquid chromatography. A mixture containing 18.5 g of sulfonyl chloride [TTBS3C, formula (74)] of TTB trisulfonate was obtained (yield 34%).

(3) Side chain introduction reaction to polyethersulfone In the synthesis method (2) of polymer electrolyte 8, instead of bis (thiophenoxy) benzenesulfonyl chloride, TTBS3C [Formula (75)] 11.3 g (17. A side chain sulfonic acid polyethersulfone [Formula (75)] was obtained in the same manner except that a mixture containing 1 mmol) was used. The yield was 2.30 g.

Using this polymer electrolyte 11 (Formula 75), a polymer electrolyte having a five-layer structure was prepared in the same manner as in Reference Example 1 but with the same polymer skeleton and different sulfonated equivalents. Table 2 shows the results of the sulfonated equivalent weight, proton conductivity, Fenton test weight retention rate, and methanol permeation amount of these polymer electrolyte membranes.

  The polymer electrolyte membrane of the present invention is suitably used for fuel cell applications, particularly for direct methanol fuel cell applications.

Claims (6)

At least the following general formula (1) a film containing a polymer electrolyte having a repeating unit (A) represented by the sulfonic acid group equivalent of membrane interior region adjacent to the membrane both surfaces, adjoining said region fuel cell electrolyte membrane, wherein less than sulfonic acid group equivalent of membrane surface to.

(Y represents a (k + 2) -valent aromatic residue, and P represents —CO—, —O—, —S—, —SO—, —SO ₂ —, —CONH—, —C (CF ₃ ) ₂ —. , A linking group selected from single bonds, k is an integer of 1 to 2 , and the side chain moiety Z in the formula is represented by the following general formula (2).
^{Z = - (X 1 Ar 1} (B 1)) - (X 2 Ar 2 (B 2)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar ⁿ ) (2)
B ^{1 to} B ^n-1 in the general formula (2) mean a branched chain in the side chain portion Z, and are represented by the following formula.
B ¹ = - ^{[(X 2 Ar 2 (B 2} )) - (X 3 Ar 3 (B 3)) - ··· - (X n-1 Ar n-1 (B n-1)) - (X ⁿ Ar ⁿ )] _f
B ² = - ^{[(X 3 Ar 3 (B 3} )) - ··· - (X n-1 Ar n-1 (B n-1)) - (X n Ar n) ] _f
・
・
・
B ^n-1 = − [X ⁿ Ar ⁿ ] _f
In said general formula (2), n is an integer of 2-5 each independently,
f is each independently an integer of 0 to 2 , at least one f is 1 or 2 ,
Ar ^{1 to} Ar ⁿ are each independently an aromatic residue,
X ^{1 to} X ⁿ are each independently —CO—, —CONH—, — (CF ₂ ) _p — (p is an integer of 1 to 10), —C (CF ₃ ) ₂ —, —COO—, —SO—. , —SO ₂ —. Z has a number exceeding 1.0 of the —SO ₃ H group. ) 2. The electrolyte membrane for fuel cells according to claim 1, wherein f is 0 or 1, and at least one f is 1. And both surfaces of the film, towards the inside from each of the both surfaces sandwiched 5μm containing surface, in the region of the width 5μm from both surfaces, there is an interface that sulfonic acid group equivalent is reduced discontinuously, by the interface and divided into a surface layer and an inner layer, a sulfonic acid group equivalent of the inner layer, is 80% or less of the sulfonic acid group equivalent of adjacent membrane surface layer, an electrolyte for a fuel cell according to claim 1 or 2 film. Sulfonic acid group equivalent sites entering the 5 [mu] m inside the thickness direction from both surfaces of the film becomes 80% or less of the sulfonic acid group equivalent surface region of the film from the site at the position of 5 [mu] m, according to claim 1 Or an electrolyte membrane for a fuel cell as described in 2 ; Electrolyte sulfonic acid group equivalent of the entire film is 0.3 meq / g or more, a fuel cell electrolyte membrane according to any one of claims 1-4. From both the membrane surface, sulfonic acid group equivalent of the polymer electrolyte in the region of up to 1μm towards the inside is less than 5 meq / g, a fuel cell electrolyte membrane according to any one of claims 1 to 5.