JP2015122308A - High polymer electrolyte, film electrode assembly and solid polymer-type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high polymer electrolyte having sufficient proton conductivity and ion-exchange capacity with suppressed swelling, and also a film electrode assembly using the high polymer electrolyte, and a solid polymer-type fuel cell using the high polymer electrolyte.SOLUTION: A high polymer electrolyte includes a block-copolymer having a segment including a specific ion-exchange group and a segment not including a specific ion-exchange group. A weight-average molecular weight of the segment not including an ion-exchange group is limited within a certain range. Thus, a solid polymer-type fuel cell can possess sufficient proton conductivity and ion-exchange capacity and suppress swelling.

Description

  The present invention relates to a polymer electrolyte, a membrane electrode assembly using the polymer electrolyte, and a solid polymer fuel cell using the polymer electrolyte.

  Polymer electrolytes are widely used for various applications as electrolytes used in electrochemical devices. For example, it is used as an electrolyte for a polymer electrolyte fuel cell, a lithium ion secondary battery, an electric double layer capacitor, an actuator, and the like.

  In recent years, fuel cells have attracted attention as an effective power source for solving environmental problems and energy problems. A fuel cell is a cell in which fuel such as hydrogen is oxidized by an oxidant such as oxygen, and chemical energy generated at this time is converted into electric energy. In particular, solid polymer fuel cells among fuel cells are expected to be used for in-vehicle power sources and household stationary power sources because the battery body is small.

  Therefore, in order to improve the high temperature durability, aromatic hydrocarbon polymer electrolytes have been developed as polymer electrolytes for solid polymer fuel cells. Aromatic hydrocarbon-based polymer electrolytes are easier to synthesize than Nafion and can reduce manufacturing costs.

  For example, sulfonated polyether ether ketone is known as an aromatic hydrocarbon polymer electrolyte (see Patent Document 1).

  For example, sulfonated polyethersulfone is known as an aromatic hydrocarbon polymer electrolyte (see Patent Document 2).

  Patent Document 3 discloses a diphenylsulfone compound for polymer electrolyte that can suppress swelling.

JP-A-6-93114 JP-A-9-245818 JP2013-203999A

  However, in the aromatic hydrocarbon polymer electrolyte, when the hydrophilic group in the polymer is increased in order to increase proton conductivity and ion exchange capacity, the polymer electrolyte easily swells with moisture. For this reason, aromatic hydrocarbon polymer electrolytes are desired to maintain the performance of having sufficient proton conductivity and ion exchange capacity, and to suppress swelling and improve strength.

  Therefore, an object of the present invention is to provide a polymer electrolyte that has sufficient proton conductivity and ion exchange capacity and is suppressed from swelling.

  As a result of intensive investigations, the present inventors have found that in a polymer electrolyte comprising a block copolymer having a segment containing a specific ion exchange group and a segment not containing a specific ion exchange group, It was found that the weight average molecular weight in the precursor of the segment not included is within a certain range, so that sufficient proton conductivity and ion exchange capacity can be obtained and swelling can be suppressed, and the present invention has been completed. .

［Ｒ_１及びＲ_２は、それぞれ独立に、−（ＣＨ_２）ａ−、−Ｏ−（ＣＨ_２）ａ−、−Ｓ−（ＣＨ_２）ａ−、−ＮＨ−（ＣＨ_２）ａ−、−（ＣＦ_２）ａ−、−Ｏ−（ＣＦ_２）ａ−、−Ｓ−（ＣＦ_２）ａ−、−ＮＨ−（ＣＦ_２）ａ−、からなる群から選択された連結基（ａは２以上の整数）であり、
Ｙ_１及びＹ_２は、それぞれ独立に、第１族元素及び第２族元素からなる群から選択される原子である。］

［Ａｒ^１、Ａｒ^２、Ａｒ^３、Ａｒ^４は、それぞれ独立に２価の芳香族基である。
Ｂ_１及びＢ_２は、それぞれ独立に２価の連結基、もしくは、それぞれが独立に存在せず、２価の芳香族基がＢ_１またはＢ_２を介さずに直接結合していることを示す。
Ｃ_１及びＣ_２は、それぞれ独立に酸素原子または硫黄原子である。
ｂ、ｃ、ｄ、ｅ、はそれぞれ独立に０または１である。
ｎは、５以上の整数である。］
［２］また、前記イオン交換基を含むセグメントは、下記一般式（３）で表されることが好ましい。

［Ｒ_１及びＲ_２は、それぞれ独立に、−（ＣＨ_２）ａ−、−Ｏ−（ＣＨ_２）ａ−、−Ｓ−（ＣＨ_２）ａ−、−ＮＨ−（ＣＨ_２）ａ−、−（ＣＦ_２）ａ−、−Ｏ−（ＣＦ_２）ａ−、−Ｓ−（ＣＦ_２）ａ−、−ＮＨ−（ＣＦ_２）ａ−、からなる群から選択された連結基（ａは２以上の整数）であり、
Ｙ１及びＹ２は、それぞれ独立に、第１族元素及び第２族元素からなる群から選択される原子である。］
［３］また、上述の高分子電解質のイオン交換容量は、０．５ミリ当量／ｇ以上４．０ミリ当量／ｇ以下の範囲内にあることが好ましい。
［４］また、プロトン酸基以外の部位が架橋剤で架橋され、架橋構造を有することが好ましい。
［５］本発明の一実施形態は、電極触媒層と、電極触媒層に接合される固体高分子電解質膜と、を備え、固体高分子電解質膜は、上述に記載の高分子電解質を含むことを特徴とする膜電極接合体である。
［６］本発明の一実施形態は、上述に記載の膜電極接合体を備えることを特徴とする固体高分子形燃料電池である。 [1] One embodiment of the present invention is a polymer electrolyte comprising a block copolymer having a segment containing an ion exchange group and a segment not containing an ion exchange group, the segment containing the ion exchange group Is represented by the following general formula (1), the segment not containing the ion exchange group is represented by the following general formula (2), the weight average molecular weight in terms of polystyrene in the precursor of the segment not containing the ion exchange group, It is a polymer electrolyte characterized by being in the range of 30,000 to 300,000.

_{[R 1} and _{R 2} are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a-, _{- (CF 2) a -,} - O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of the linking groups (a is An integer greater than or equal to 2),
Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]

[Ar ¹ , Ar ² , Ar ³ , Ar ⁴ are each independently a divalent aromatic group.
B ₁ and B ₂ are each independently a divalent linking group, or each of them is not independently present, indicating that a divalent aromatic group is directly bonded without passing through B ₁ or B _2. .
C ₁ and C ₂ are each independently an oxygen atom or a sulfur atom.
b, c, d, and e are each independently 0 or 1.
n is an integer of 5 or more. ]
[2] Moreover, it is preferable that the segment containing the said ion exchange group is represented by following General formula (3).

_{[R 1} and _{R 2} are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a-, _{- (CF 2) a -,} - O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of the linking groups (a is An integer greater than or equal to 2),
Y1 and Y2 are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]
[3] The ion exchange capacity of the polymer electrolyte is preferably in the range of 0.5 meq / g or more and 4.0 meq / g or less.
[4] Moreover, it is preferable that parts other than the protonic acid group are crosslinked with a crosslinking agent to have a crosslinked structure.
[5] One embodiment of the present invention includes an electrode catalyst layer and a solid polymer electrolyte membrane bonded to the electrode catalyst layer, and the solid polymer electrolyte membrane includes the polymer electrolyte described above. Is a membrane electrode assembly.
[6] One embodiment of the present invention is a polymer electrolyte fuel cell comprising the membrane electrode assembly described above.

  The polymer electrolyte of the present invention is a polymer electrolyte comprising a block copolymer having a segment containing a specific ion exchange group and a segment not containing a specific ion exchange group, and the ion exchange group The weight average molecular weight of the segment that does not contain is within a certain range. Thereby, the polymer electrolyte fuel cell has sufficient proton conductivity and ion exchange capacity, and can suppress swelling.

It is the schematic which concerns on the polymer electrolyte fuel cell of this invention.

  The polymer electrolyte of the present invention comprises a block copolymer having a segment containing an ion exchange group and a segment not containing an ion exchange group.

<Segment including ion exchange groups>
In the polymer electrolyte of the present invention, the segment containing an ion exchange group has a structure in which a —SO ₃ Y group which is an ion exchange group is introduced into a diphenylsulfone skeleton via R which is a linking group. The general formula (1) showing <segment containing ion exchange group> is shown below.

［Ｒ_１及びＲ_２は、それぞれ独立に、−（ＣＨ_２）ａ−、−Ｏ−（ＣＨ_２）ａ−、−Ｓ−（ＣＨ_２）ａ−、−ＮＨ−（ＣＨ_２）ａ−、−（ＣＦ_２）ａ−、−Ｏ−（ＣＦ_２）ａ−、−Ｓ−（ＣＦ_２）ａ−、−ＮＨ−（ＣＦ_２）ａ−、からなる群から選択された連結基（ａは２以上の整数）であり、
Ｙ_１及びＹ_２は、それぞれ独立に、第１族元素及び第２族元素からなる群から選択される原子である。］

_{[R 1} and _{R 2} are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a-, _{- (CF 2) a -,} - O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of the linking groups (a is An integer greater than or equal to 2),
Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]

  A conventional aromatic hydrocarbon polymer electrolyte has a structure in which an ion exchange group is directly bonded to an aromatic ring. For this reason, the steric hindrance of the ion exchange group inhibits the stack in the aromatic ring part of the main chain. On the other hand, the main chain having an aromatic ring has hydrophilicity. Therefore, when the stack of the main chain is inhibited and the degree of freedom of the main chain is high, the presence of water molecules around the main chain is stabilized. That is, the conventional aromatic hydrocarbon polymer electrolyte is likely to swell because water molecules exist stably around the main chain. Here, the term “stack” means that polymer main chains are physically connected by weak interactions such as van der Waals force and π-π interaction.

The polymer electrolyte of the present invention has a structure in which —SO ₃ Y group which is an ion exchange group is introduced through R which is a linking group, and thereby the ion exchange group is arranged away from the aromatic ring part of the main chain. I can do it. Thereby, since the steric hindrance of the ion exchange group is reduced, the aromatic ring portion of the main chain is easily stacked. Therefore, the polymer electrolyte of the present invention can suppress swelling because water molecules cannot exist stably around the main chain due to the stack of the main chain. Further, since the ion exchange group is easily moved by the mobility of the linking group, proton conductivity is also improved.

  An ion exchange group is a group contributing to ion conduction when used as a polymer electrolyte. In particular, when used as an electrolyte for a polymer electrolyte fuel cell, ion exchange groups contribute to putron conduction. -SO3-Y + group Y + is a group 1 element ion such as hydrogen ion, lithium ion, sodium ion, potassium ion or rubidium ion, and a group 2 element such as magnesium ion, calcium ion, strontium ion or barium ion Any ion selected from the group consisting of ions. Y1 and Y2 may be different ions, but if they are the same ion, synthesis of the diphenylsulfone monomer is facilitated. In order to facilitate the production of the polymer, Y is preferably a group 1 element ion, and most preferably a sodium ion.

A linking group _{R is, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a -, - (CF 2) _{a -, - O- (CF 2} ) a -, - S- (CF 2) a-, and is any one selected from -NH- _(CF 2) group consisting of a-. A represents an integer of 2 or more. In order to facilitate the synthesis of the diphenylsulfone monomer, R is preferably —O— (CH ₂ ) a—, and a is preferably 3 or 4. R1 and R2 may be different linking groups, but if they are the same linking group, synthesis of the diphenylsulfone monomer is facilitated.

  Moreover, it is preferable that especially the segment containing an ion exchange group is a structure represented by following General formula (3). As shown in the following general formula (3), the main chain is preferably bonded to the meta position with respect to the sulfonyl group. Further, R as a linking group is preferably bonded to the para position with respect to the sulfonyl group. Since the steric hindrance of the ion exchange group can be suppressed by the structure represented by the following general formula (3), the main chains are easily stacked. Therefore, swelling can be further suppressed.

［Ｒ１及びＲ２は、それぞれ独立に、−（ＣＨ_２）ａ−、−Ｏ−（ＣＨ_２）ａ−、−Ｓ−（ＣＨ_２）ａ−、−ＮＨ−（ＣＨ_２）ａ−、−（ＣＦ_２）ａ−、−Ｏ−（ＣＦ_２）ａ−、−Ｓ−（ＣＦ_２）ａ−、−ＮＨ−（ＣＦ_２）ａ−、からなる群から選択された連結基（ａは２以上の整数）であり、
Ｙ１及びＹ２は、それぞれ独立に、第１族元素及び第２族元素からなる群から選択される原子である。］

[R1 and R2, _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a -, - ( _{CF 2) a -, - O-} (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of is linking group (a 2 or more Integer), and
Y1 and Y2 are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]

<Segment not containing ion exchange groups>
In the polymer electrolyte of the present invention, the segment containing no ion exchange group has a structural unit represented by the following general formula (2).

［Ａｒ^１、Ａｒ^２、Ａｒ^３、Ａｒ^４は、それぞれ独立に２価の芳香族基である。
Ｂ１及びＢ２は、それぞれ独立に２価の連結基、もしくは、それぞれが独立に存在せず、２価の芳香族基がＢ１またはＢ２を介さずに直接結合していることを示す。
Ｃ_１及びＣ_２は、それぞれ独立に酸素原子または硫黄原子である。
ｂ、ｃ、ｄ、ｅ、はそれぞれ独立に０または１である。
ｎは、５以上の整数である。］

[Ar ¹ , Ar ² , Ar ³ , Ar ⁴ are each independently a divalent aromatic group.
B1 and B2 each independently represent a divalent linking group, or each independently represents a divalent aromatic group bonded directly without B1 or B2.
C ₁ and C ₂ are each independently an oxygen atom or a sulfur atom.
b, c, d, and e are each independently 0 or 1.
n is an integer of 5 or more. ]

In the general formula (2), the divalent aromatic group that is any one of Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ is a fluorine atom, an alkyl group having 1 to 20 carbon atoms, and 1 to 20 carbon atoms. May be substituted with an alkoxy group or a nitrile group. In addition, these alkyl groups and alkoxy groups may have a substituent.

In the above general formula (2), when B ₁ or B ₂ is a divalent linking group, B ₁ and B ₂ are carbonyl group, sulfonyl group, 2,2-isopropylidene group, 2,2-hexafluoro. A linking group based on an isopropylidene group or a 9,9-2 substituted fluorene is preferred.

  In the general formula (2), n represents an integer of 5 or more, preferably 5 or more and 200 or less, and more preferably 10 or more. When n is 5 or more, when the polymer electrolyte is used as an electrolyte membrane of a polymer electrolyte fuel cell, the film formability, mechanical strength, and durability can be sufficiently obtained.

  More specific examples of the segments represented by the general formula (2) that do not contain an ion exchange group are listed below by chemical formulas.

<Polymer electrolyte made of block copolymer>
The polymer electrolyte of the present invention comprises a block copolymer having a segment containing an ion exchange group and a segment not containing an ion exchange group. In the block copolymer, segments containing ion exchange groups and segments not containing ion exchange properties are aggregated to cause phase separation. Therefore, when the electrolyte membrane is used, a path through which protons are conducted by the phase having ion exchange properties is formed. As a result, proton conductivity is improved.

  The amount of ion exchange groups introduced into the polymer electrolyte of the present invention is preferably 0.5 meq / g or more and 4.0 meq / g or less, expressed as ion exchange capacity, and 1.0 meq / g or more. More preferably, it is 3.0 meq / g or less. When the ion exchange capacity is 0.5 meq / g or more, when used as an electrolyte membrane of a polymer electrolyte fuel cell, proton conductivity is improved, so that the power generation performance of the fuel cell is enhanced. Further, when the ion exchange capacity is 4.0 meq / g or less, water resistance and mechanical strength as an electrolyte membrane of the polymer electrolyte fuel cell are enhanced.

In addition, the polymer electrolyte may include a crosslinked structure in which a portion other than the protonic acid group is crosslinked through the crosslinking agent by adding a crosslinking agent. The cross-linking agent is a cross-linking agent that can cause the cross-linking reaction to proceed at a portion other than the proton acid group without using a proton acid group, and does not significantly change the proton conductivity of the proton conductive material before and after the cross-linking reaction. I just need it. In particular, a crosslinking agent having a structure in which a methylol group represented by —CH 2 OH is bonded to an aromatic ring is preferable because a crosslinking reaction easily proceeds by heating. As such a crosslinking agent having a methylol group, a compound having at least two aromatic rings having a methylol group in the molecule is preferable. If the compound has at least two methylol group-containing aromatic rings in the molecule, the reaction proceeds without going through the protonic acid group contained in the proton-conducting polymer, so that the proton conductivity is reduced by the crosslinking reaction. This can be suppressed. Examples of the structure of the crosslinking agent include the structures shown below.

  As a reaction method of the crosslinking reaction, a light irradiation method, a heating method, a pH adjustment method, or the like can be used. In particular, when a heating method is used, the apparatus and process are simplified, so that the crosslinking reaction can be performed easily and economically. The heating temperature in the heating method may be in a range where a crosslinking reaction occurs. When a compound having at least two aromatic rings having a methylol group in the molecule is used as the cross-linking agent, it is preferably between 60 ° C. and 250 ° C. If it is 60 degreeC or more, a crosslinking reaction can be advanced. Moreover, if it is 250 degrees C or less, the detachment | desorption and decomposition reaction of the proton acid group from a proton conductive polymer or a crosslinking agent will not occur easily. Moreover, since the reaction of such a crosslinking agent is a dehydration condensation reaction, the crosslinking reaction can be promoted by drying under reduced pressure.

  In addition, when a cross-linking agent is added to the polymer electrolyte, another polymer may be added to improve mechanical strength and water resistance. At this time, examples of the polymer to be added include aromatic polyether, aromatic polyether ketone, aromatic polyether ether ketone, aromatic polyether sulfone, aromatic polysulfone, aromatic polyether nitrile, and aromatic polyether. Examples include pyridine, aromatic polyimide, aromatic polyamide, aromatic polyamideimide, aromatic polyazole, aromatic polyester, and aromatic polycarbonate. These polymers may be sulfonated or may not be sulfonated.

<Polymer electrolyte synthesis method>
The polymer electrolyte of the present invention comprises a block copolymer. Here, the block copolymer includes (1) a precursor of a segment containing an ion exchange group (hereinafter referred to as a diphenylsulfone monomer) and (2) a precursor of a segment not containing an ion exchange group (hereinafter referred to as a macro). Can be synthesized by (3) polycondensation. Hereinafter, the method for synthesizing the polymer electrolyte of the present invention will be described with specific examples.

[(1) Diphenylsulfone monomer]
In the synthesis of the polymer electrolyte of the present invention, the diphenylsulfone monomer may be a diphenylsulfone in which an ion exchange group via a linking group and a leaving group used for a condensation reaction are introduced. Here, any leaving group may be used as long as it is known as a leaving group used in the condensation reaction. For example, as a leaving group, a halogen group such as a chlorine atom, a bromine atom and an iodine atom, a p-toluenesulfonyloxy group (CH3C6H4-p-SO3-), a methanesulfonyloxy group (CH3SO3-), a trifluoromethanesulfonyloxy group ( CF3SO3-), etc. may be used.

  In addition, in the diphenylsulfone monomer, when the halogen group is bonded to the meta position and the linking group is bonded to the para position with respect to the sulfonyl group, the synthesis of the precursor of the segment including the ion exchange group is facilitated. The yield is also high, which is preferable. As a preferred example of the diphenylsulfone monomer, the following general formula (4) is shown.

［Ｒ_１及びＲ_２は、それぞれ独立に−（ＣＨ_２）ａ−、−Ｏ−（ＣＨ_２）ａ−、−Ｓ−（ＣＨ_２）ａ−、−ＮＨ−（ＣＨ_２）ａ−、−（ＣＦ_２）ａ−、−Ｏ−（ＣＦ_２）ａ−、−Ｓ−（ＣＦ_２）ａ−、−ＮＨ−（ＣＦ_２）ａ−、からなる群から選択される連結基（ａは２以上の整数）であり、
Ｘ_１及びＸ_２は、それぞれ独立に、ハロゲン原子であり、
Ｙ_１及びＹ_２は、それぞれ独立に第１族元素及び第２族元素である。］

[R ₁ and R ₂ are each independently-(CH ₂ ) a-, -O- (CH ₂ ) a-, -S- (CH ₂ ) a-, -NH- (CH ₂ ) a-,- _{(CF 2) a -, -} O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, the linking group (a selected from the group consisting of 2 An integer greater than or equal to
X ₁ and X ₂ are each independently a halogen atom,
Y ₁ and Y ₂ are each independently a Group 1 element and a Group 2 element. ]

  As the diphenylsulfone monomer represented by the general formula (4), examples of the compounds are more specifically listed below by chemical formulas.

The method for synthesizing the diphenylsulfone monomer represented by the general formula (4) will be described with a specific example. In this example, in the diphenylsulfone monomer represented by the general formula (4), R ₁ and R ₂ are —O— (CH ₂ ) a— groups, X ₁ and X ₂ are bromine, and Y ₁ and Y ₂ are group 1. The case where it is an atom is illustrated. Even if R ₁ , R ₂ , X ₁ , X ₂ , Y ₁ , Y ₂ are different from the examples, those skilled in the art can obtain the desired diphenylsulfone monomer by a method according to the following synthesis route. Can be synthesized.

  First, 4,4'-dihydroxydiphenylsulfone is treated with an inorganic base and reacted with a monohaloalkane. Thereby, a hydroxy group is alkoxylated and the compound shown by following General formula (5) is obtained. In the following general formula (5), Alkyl represents an alkyl group. By protecting the hydroxy group with an alkyl group by alkoxylation of the hydroxy group, the regioselectivity of the bromination reaction in the next step can be improved.

        As the inorganic base, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like are preferable. The amount of the inorganic base is preferably 200 mol% or more and 400 mol% or less, and more preferably 200 mol% or more and 300 mol% or less with respect to 100 mol% of 4,4'-dihydroxydiphenylsulfone.

  As the monohaloalkane, those in which an alkyl group is linear and a halogen atom is bonded to the terminal of the alkyl group are preferable. For example, chloromethane, chloroethane, 1-chloropropane, 1-chlorobutane, 1-chloropentane, 1-chlorohexane, bromomethane, bromoethane, 1-bromopropane, 1-bromobutane, 1-bromopentane, 1-bromohexane, iodomethane, Examples include iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane and the like. In order to increase the reactivity, those having 4 or more carbon atoms and a halogen atom being bromine or iodine are preferable.

  The amount of the monohaloalkane is preferably 200 mol% or more and 400 mol% or less, more preferably 200 mol% or more and 300 mol% or less, with respect to 100 mol% of 4,4'-dihydroxydiphenylsulfone.

  As reaction conditions for the reaction with the monohaloalkane, the reaction temperature is preferably 25 ° C. or more and 100 ° C. or less, and the reaction time is preferably 10 hours or more and 48 hours or less. This reaction may be performed in an air atmosphere or a nitrogen atmosphere. The reaction solvent may be a good solvent, and a polar solvent is preferable. For example, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, ethanol, and the like can be suitably used.

  Next, the compound represented by the general formula (5) is treated with bromine. As a result, a dibrominated compound represented by the following general formula (6) is obtained.

  The amount of bromine is preferably 20 mol% or more and 300 mol% or less and more preferably 200 mol% or more and 250 mol% or less with respect to 100 mol% of the compound represented by the general formula (6). preferable.

  As reaction conditions for the bromine treatment, the reaction temperature is preferably 80 ° C. or higher and 150 ° C. or lower, and the reaction time is preferably 10 hours or longer and 48 hours or shorter. This reaction may be performed in an air atmosphere or a nitrogen atmosphere. As the reaction solvent, hydrobromic acid is preferable.

  Next, the compound represented by the general formula (6) is treated with a Lewis acid. Thereby, an alkoxy group is converted into a hydroxy group, and a compound represented by the following general formula (7) is obtained.

  The amount of the Lewis acid is preferably 200 mol% or more and 400 mol% or less, and 200 mol% or more and 300 mol% or less with respect to 100 mol% of the compound represented by the general formula (7). More preferred. As the Lewis acid, a halide of a group 13 element is preferable, and aluminum chloride is more preferable.

  As reaction conditions for the Lewis acid treatment, the reaction temperature is preferably 0 ° C. or higher and 100 ° C. or lower, and more preferably 25 ° C. or higher and 40 ° C. or lower. The reaction time is preferably 0.5 hours or more and 5 hours or less. This reaction is preferably performed in an air atmosphere. The reaction solvent is preferably a good solvent, and polar solvents such as chloroform, dichloromethane, N, N-dimethylformamide, and nitrobenzene are preferred.

  Next, the compound represented by the general formula (7) is treated with an inorganic base and reacted with sultone, which is a ring-opening compound. Thereby, the diphenyl sulfone monomer shown by following General formula (8) is obtained.

［Ｙ_１及びＹ_２は、それぞれ独立に、第１族元素及び第２族元素からなる群から選択される原子である。］

[Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]

  As the inorganic base, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like are preferably used. The amount of the base is preferably 200 mol% or more and 400 mol% or less, more preferably 200 mol% or more and 300 mol% or less with respect to 100 mol% of the compound represented by the general formula (8). .

  Examples of sultone include 1,3-propane sultone, 1,4-butane sultone, 1,5-pentane sultone, 1,6-hexane sultone, 1,7-heptane sultone, 1,8-octane sultone, and the like. Among these, 1,3-propane sultone and 1,4-butane sultone are preferable. Moreover, you may use what substituted all the hydrogen atoms in the said sultone by the fluorine atom.

  As reaction conditions for reacting with sultone, the reaction temperature is preferably 25 ° C. or more and 100 ° C. or less, and the reaction time is preferably 10 hours or more and 48 hours or less. This reaction may be performed in an air atmosphere or a nitrogen atmosphere. The reaction solvent is preferably a good solvent, and more preferably a polar solvent. For example, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and ethanol are preferable.

[(2) Macromonomer]
In the synthesis of the polymer electrolyte of the present invention, a compound represented by the following general formula (9) can be used as the macromonomer.

［Ａｒ^１、Ａｒ^２、Ａｒ^３、Ａｒ^４は、それぞれ独立に２価の芳香族基である。
Ｂ_１及びＢ_２は、それぞれ独立に２価の連結基、もしくは、それぞれが独立に存在せず、２価の芳香族基がＢ_１またはＢ_２を介さずに直接結合していることを示す。
Ｃ_１及びＣ_２は、それぞれ独立に酸素原子または硫黄原子である。
ｂ、ｃ、ｄ、ｅ、はそれぞれ独立に０または１である。
ｎは、５以上の整数である。
Ｚは、縮合反応における脱離基であり、それぞれ同じであってもよく、異なっていてもよい。］

[Ar ¹ , Ar ² , Ar ³ , Ar ⁴ are each independently a divalent aromatic group.
B ₁ and B ₂ are each independently a divalent linking group, or each of them is not independently present, indicating that a divalent aromatic group is directly bonded without passing through B ₁ or B _2. .
C ₁ and C ₂ are each independently an oxygen atom or a sulfur atom.
b, c, d, and e are each independently 0 or 1.
n is an integer of 5 or more.
Z is a leaving group in the condensation reaction, and may be the same or different. ]

In the macromonomer represented by the general formula (9), Z is a leaving group in the condensation reaction, and one known as a leaving group used in the condensation reaction may be appropriately selected and used. For example, as a leaving group, a halogen group such as a chlorine atom, a bromine atom, or an iodine atom, a p-toluenesulfonyloxy group (CH ₃ C ₆ H ₄ -p-SO ₃ —), a methanesulfonyloxy group (CH ₃ SO _3). -), a trifluoromethanesulfonyloxy group _(CF 3 _SO 3 -), may be used like.

  Specific examples of the macromonomer represented by the general formula (9) are listed below by chemical formula. Those skilled in the art can appropriately synthesize the structure represented by the following chemical formula using a known synthesis route.

  As a specific example of the synthesis route of the macromonomer represented by the general formula (9), a reaction formula is given. The following example illustrates the case where Z is a chlorine atom in the macromonomer represented by the general formula (9). In any case, a macromonomer having both ends of a chlorine atom can be synthesized by adding a dichloro compound as a starting material at the end of the polymerization reaction.

（マクロモノマーの合成経路：例１）

(Macromonomer synthesis route: Example 1)

（マクロモノマーの合成経路：例２）

(Macromonomer synthesis route: Example 2)

（マクロモノマーの合成経路：例３）

(Macromonomer synthesis route: Example 3)

In the polymer electrolyte of the present invention, the molecular weight of the segment precursor (macromonomer) that does not contain an ion exchange group is in the range of about 30,000 to 300,000, expressed in terms of polystyrene-equivalent number weight average molecular weight. is there. In particular, it is preferably in the range of about 30,000 to 200,000, more preferably in the range of about 30,000 to 100,000. When the molecular weight of the precursor (macromonomer) is 30,000 or more, the chain length of the segment containing no ion exchange group of the block copolymer is long, and the water resistance is improved. Moreover, manufacture becomes more convenient because molecular weight is 300,000 or less. When the molecular weight is larger than 300,000, it is difficult to obtain by a general polymerization reaction, and it is not practical as an industrial member.
Furthermore, the appropriate upper limit of the hot water swelling rate of the polymer electrolyte of the present invention is desirably 10% or less.

[(3) condensation polymerization reaction]
The diphenylsulfone monomer and the macromonomer are subjected to condensation polymerization to obtain a block polymer. In the condensation polymerization reaction between the diphenylsulfone monomer and the macromonomer, a condensation polymerization reaction using a transition metal complex can be used. In the condensation polymerization reaction, a polymer obtained by polymerizing diphenylsulfone monomers to some extent may be used instead of the diphenylsulfone monomer.

  The transition metal complex is one in which a ligand forms a coordinate bond with a transition metal. Examples of the transition metal complex include a nickel complex, a palladium complex, a platinum complex, a copper complex, a rhodium complex, a zirconium complex, and an iron complex. Among these, when a nickel complex or a palladium complex is used, the reaction efficiency can be increased and the reaction can be performed under mild conditions.

  As ligands of transition metal complexes, 2,2′-bipyridyl, 1,10-phenanthroline, N, N, N ′, N′-tetramethylethylenediamine, acetylacetonate, triphenylphosphine, tolylphosphine, tributyl Phosphine, 1,2-bis (diphenylphosphino) ethane, 1,3-bis (diphenylphosphino) propane, 1,4-bis (diphenylphosphino) butane, and 1,1′-bis (diphenylphosphino) It is preferable to have at least one of ferrocene. The transition metal complex may have one kind of these ligands, or may have two or more kinds in combination.

  In the condensation polymerization reaction for synthesizing the block copolymer, a zero-valent transition metal complex such as a zero-valent nickel complex or a zero-valent palladium complex is preferably used as the transition metal complex. In particular, it is preferable to use a zerovalent nickel complex.

  Examples of the zerovalent nickel complex include bis (1,5-cyclooctadiene) nickel (0), (ethylene) bis (triphenylphosphine) nickel (0), tetrakis (triphenylphosphine) nickel (0), and the like. Can be mentioned. In particular, bis (1,5-cyclooctadiene) nickel (0) is suitable for use in the synthesis of polymer electrolytes because it is readily available.

  As the zero-valent transition metal complex, an off-the-shelf product or a separately synthesized product may be used. As a method for synthesizing a zero-valent transition metal complex, a known method such as a method of reducing a transition metal compound to a zero valence by using a reducing agent can be used. The synthesized zero-valent transition metal complex may be taken out from the reaction system, or may be used as it is in the reaction system without being taken out.

  Examples of the reducing agent for obtaining a zero-valent transition metal complex include iron, zinc, manganese, aluminum, magnesium, sodium, and calcium. Of these, zinc, magnesium and manganese are preferred. These reducing agents can be used after being more activated by bringing them into contact with an acid such as an organic acid. If necessary, sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide and sodium sulfate; potassium compounds such as potassium fluoride, potassium chloride, potassium bromide, potassium iodide and potassium sulfate An ammonium compound such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate may be used in combination.

  In synthesizing a zero-valent transition metal complex, a divalent transition metal compound is usually used, but a zero-valent transition metal compound may be used. As the divalent transition metal compound, it is preferable to use a divalent nickel compound or a divalent palladium compound. Examples of the divalent nickel compound include nickel chloride, nickel bromide, nickel iodide, nickel acetate, nickel acetylacetonate, nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide. And bis (triphenylphosphine). Examples of the divalent palladium compound include palladium chloride, palladium bromide, palladium iodide, palladium chloride bis (triphenylphosphine), palladium bromide bis (triphenylphosphine), and palladium iodide bis (triphenylphosphine). Can be mentioned.

  When the condensation reaction is performed using the transition metal complex, it is preferable to add a compound that can be a ligand of the transition metal complex used. Thereby, the reactivity of a polymerization reaction is improved and the yield of a block copolymer and a polymerization degree are raised. The compound to be added may be the same as or different from the ligand of the transition metal complex used. For example, triphenylphosphine and 2,2'-bipyridyl are preferable because they are versatile and inexpensive. In particular, when 2,2'-bipyridyl is used in combination with bis (1,5-cyclooctadiene) nickel (0), it becomes possible to increase the yield and molecular weight of the block copolymer.

  The addition amount of the ligand is preferably 10 mol% or more and 1000 mol% or less, and more preferably 100 mol% or more and 500 mol% or less with respect to 100 mol% of the zero-valent transition metal complex.

  The amount of the zero-valent transition metal complex used is preferably 10 mol% or more with respect to 100 mol% of the diphenylsulfone monomer. In particular, 100 mol% or more is preferable and 200 mol% or more is more preferable. It can suppress that a yield and a polymerization degree fall that the usage-amount is 10 mol% or more. Although there is no restriction | limiting in particular about the upper limit of usage-amount, The process at the time of post-processing of superposition | polymerization will become easy as it is 500 mol% or less.

  As conditions for the condensation polymerization reaction, the reaction temperature is preferably 0 ° C. or higher and 200 ° C. or lower, and more preferably 50 ° C. or higher and 100 ° C. or lower. The reaction time is preferably 0.5 hours or more and 100 hours or less, and more preferably 1 hour or more and 40 hours or less. The condensation polymerization reaction is preferably performed in an inert gas atmosphere such as nitrogen or argon. According to such conditions, the yield and degree of polymerization of the condensation polymerization reaction are increased.

  Examples of the condensation polymerization reaction solvent include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, toluene, xylene, and mesitylene. , Aromatic hydrocarbon solvents such as benzene and butylbenzene, ether solvents such as tetrahydrofuran, 1,4-dioxane, dibutyl ether and tert-butyl methyl ether, and ester solvents such as ethyl acetate, butyl acetate and methyl benzoate And alkyl halide solvents such as chloroform and dichloroethane. These polymerization solvents are preferably used after sufficiently dehydrated.

  In order to increase the yield and degree of polymerization of the condensation polymerization reaction, it is desirable that the diphenylsulfone monomer and the macromonomer are sufficiently dissolved in a solvent. Therefore, tetrahydrofuran, 1,4-dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, which are good solvents for the diphenylsulfone monomer and the macromonomer, It is preferable to use sulfolane, toluene or the like. In particular, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, and a mixture of two or more of these are preferably used.

  The concentration of the total amount of the upper diphenylsulfone monomer in the polymerization solvent is preferably 1% by weight or more and 90% by weight or less. Moreover, it is preferable that the density | concentration of the total amount of the macromonomer in a polymerization solvent is 5 to 40 weight%. If the lower limit of the concentration is such a value, the produced polymer compound can be easily recovered. Further, when the upper limit of the concentration is such a value, stirring during the reaction becomes easy.

  From the above, a block copolymer is synthesized. When taking out the produced block copolymer from a reaction mixture, a conventional method can be applied. For example, the polymer can be precipitated by adding a poor solvent to the reaction mixture, and the target product can be obtained by filtration or the like. Moreover, it can refine | purify by normal purification methods, such as reprecipitation using water washing and a good solvent and a poor solvent, as needed.

  Moreover, when the sulfonic acid group in the produced block copolymer is in the form of a salt such as sodium salt, it is preferable to convert the sulfonic acid group into a free acid form. By using a free acid, it can be used as an electrolyte membrane of a polymer electrolyte fuel cell. Conversion to the free acid is usually performed by washing with an acidic solvent. Examples of the acid used include hydrochloric acid, sulfuric acid, nitric acid and the like, and hydrochloric acid is particularly preferable.

<Solid polymer electrolyte membrane>
The solid polymer electrolyte membrane using the polymer electrolyte of the present invention can be expected to be used in a wide range of applications as a proton conductive membrane for electrochemical devices. Hereinafter, a method for producing a solid polymer electrolyte membrane using a polymer electrolyte will be described.

  The membrane formation of the polymer electrolyte may be appropriately selected from known film formation methods. For example, a method such as (1) a casting method or (2) a composite electrolyte membrane impregnated in a porous substrate may be used.

[Casting method]
The casting method is a method of preparing a film on a film by adjusting a coating liquid by dispersing a polymer electrolyte in a solvent, coating the coating liquid on a substrate, and peeling the coating film from the substrate. It is.

  In the casting method, the substrate to be used may be appropriately selected from the substrates used in the usual solution casting method. For example, a substrate made of glass, plastic, metal or the like is used. In particular, a substrate made of a thermoplastic resin such as a polyethylene terephthalate (PET) film is preferably used.

  In the casting method, the solvent used for dispersing the polymer electrolyte may be any solvent that can dissolve the polymer electrolyte and can be removed thereafter. For example, aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, or dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene Chlorinated solvents such as dichlorobenzene or alcohols such as methanol, ethanol and propanol are preferably used. These solvents may be used alone, or two or more kinds of solvents may be mixed and used as necessary. Among them, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane and the like are preferable because of high polymer solubility.

  The concentration of the solution in which the polymer electrolyte is dissolved is preferably 5% by weight or more and 40% by weight or less, and more preferably 7% by weight or more and 25% by weight or less. When the concentration is 5% by weight or more, it is easy to increase the film thickness, and the generation of pinholes can be suppressed. On the other hand, when the concentration is 40% by weight or less, the solution viscosity is maintained to the extent that film formation can be easily performed, and the surface smoothness is improved.

  Further, for the purpose of improving various physical properties of the membrane, additives such as a plasticizer, a stabilizer, a release material, and a water retention agent may be added to the solution in which the polymer electrolyte is dissolved. In particular, when inorganic or organic fine particles are added as a water retention agent, the moisture in the membrane can be controlled, and therefore, it can be suitably used as an electrolyte membrane for a polymer electrolyte fuel cell.

  Further, another type of polymer may be mixed in the solution in which the polymer electrolyte is dissolved. By mixing other types of polymers in the same solvent and co-casting, a composite polymerized solid polymer electrolyte membrane can be obtained. For this reason, it can adjust to the desired physical property according to a use.

  Further, for the purpose of improving the mechanical strength of the film, it may be crosslinked by irradiating an electron beam, radiation or the like after the film formation.

[Composite electrolyte membrane impregnated in porous substrate]
A solid polymer electrolyte membrane may be produced by impregnating a porous substrate with a solution in which the polymer electrolyte of the present invention is dissolved. Here, the porous substrate may be appropriately selected from known porous substrates depending on the application. For example, a porous film, a nonwoven fabric, a fibril, etc. may be used. In addition, it is preferable to use an aliphatic, aromatic polymer, fluorine-based polymer, or the like as the porous substrate. Heat resistance is improved and physical strength is increased.

<Solid polymer fuel cell>
A solid polymer fuel cell will be described as an example of the use of the solid polymer electrolyte membrane using the polymer electrolyte of the present invention. In the polymer electrolyte fuel cell, the polymer electrolyte membrane can be used as a member in the membrane electrode assembly. The polymer electrolyte fuel cell has a structure in which a membrane electrode assembly is disposed at a portion sandwiched between separators.

  The separator may be appropriately selected from those used in known fuel cells. For example, a carbon type separator, a metal type separator, or the like may be used.

  In the polymer electrolyte fuel cell, the membrane electrode assembly is a member that is bonded and integrated in the order of fuel electrode (negative electrode) / solid polymer electrolyte membrane / air electrode (positive electrode). A membrane electrode assembly is obtained by laminating an electrode catalyst layer and a gas diffusion layer on a solid polymer electrolyte membrane.

  The gas diffusion layer is provided in order to efficiently transport the raw material gas to the catalyst. For example, carbon woven fabric, carbon non-woven fabric, carbon cloth, carbon paper, porous carbon material, etc. may be used. The gas diffusion layer preferably uses a conductive material. By using a conductive material, it can be used as a current collector.

  The electrode catalyst layer is a layer that holds a catalyst for promoting the electrode reaction. As the catalyst used for the electrode catalyst layer, a known material can be used as long as it can activate a redox reaction with hydrogen or oxygen. In particular, it is preferable to use fine particles of platinum or a platinum-based alloy. As the fine particles of platinum or platinum-based alloy, particulate particles such as activated carbon and graphite and those supported on fibrous carbon are preferably used.

  Hereinafter, the formation of the electrode catalyst layer will be described. The electrode catalyst layer can be formed by adjusting the electrode catalyst ink and applying the electrode catalyst ink.

  The electrode catalyst ink is obtained by dispersing a catalyst in a dispersion medium. In addition, the electrode catalyst ink may contain (1) a polymer electrolyte, (2) a polymer electrolyte in which organic substances are mixed and removed by acid treatment, and the like.

  The solvent used as a dispersion medium for the electrode catalyst ink is a solution in which the polymer electrolyte is dissolved in a highly fluid state without eroding the polymer electrolyte mixed with the catalyst particles, the polymer electrolyte, or the organic matter and removed by the acid treatment. What is necessary is just to be disperse | distributed as a fine gel. In particular, at least a volatile liquid organic solvent is desirably contained. Methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl Alcohols such as alcohol and pentaanol, acetone-based solvents such as methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, diisobutyl ketone, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxy Ether solvents such as toluene and dibutyl ether, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethyleneglycol Le, diacetone alcohol, 1-methoxy-2-propanol polar solvents such as is preferred. Moreover, you may use what mixed 2 or more types of these solvents. Further, when a lower alcohol is used as a solvent, the possibility of ignition can be suppressed by using a mixed solvent with water. The amount of water added is not limited as long as the polymer electrolyte is separated to cause white turbidity or gelation.

  The solid content in the electrode catalyst ink is preferably 1% by mass or more and 50% by mass or less. If the solid content is 1% by mass or more, the viscosity of the electrode catalyst ink does not become too high, and cracks are unlikely to occur on the surface of the electrode catalyst layer. In addition, when the solid content is 50% by mass or less, the film formation rate is appropriately maintained, so that productivity is improved.

  The method for applying the electrode catalyst ink may be appropriately selected from known application methods. For example, a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spray method, or the like may be used.

  The target to which the electrode catalyst ink is applied may be any of a gas diffusion layer, a solid polymer electrolyte membrane, and a transfer sheet. When the transfer sheet is used, a membrane electrode assembly having electrode catalyst layers on both sides of the solid polymer electrolyte membrane is obtained by peeling the transfer sheet after bonding the electrode catalyst layer to the solid polymer electrolyte membrane. The transfer sheet may be any material that has good transferability.

  The removal of the organic substance by acid treatment washing may be performed after the polymer electrolyte membrane and the electrode catalyst layer containing the organic substance are produced and the membrane / electrode assembly is produced.

  FIG. 1 schematically shows an example of a polymer electrolyte fuel cell of the present invention. In the polymer electrolyte fuel cell 10 shown in FIG. 1, the membrane electrode assembly 3 is disposed at a portion sandwiched between the separator 7a and the separator 7b. The membrane electrode assembly 3 has a structure in which an air electrode 5 / solid polymer electrolyte membrane 1 / fuel electrode 6 are arranged in this order. Electrode catalyst layer 2a and electrode catalyst layer 2b are disposed on the front and back of solid polymer electrolyte membrane 1, respectively. The air electrode 5 has a structure in which the gas diffusion layer 4a is disposed on the electrode catalyst layer 2a, and serves as a cathode of the polymer electrolyte fuel cell. The fuel electrode 6 has a structure in which the gas diffusion layer 4b is disposed in the electrode catalyst layer 2b, and serves as an anode of the polymer electrolyte fuel cell. A gas flow path 8a is provided on the gas diffusion layer 4a side of the separator 7a, and a cooling water flow path 9a is provided on the opposite side of the gas flow path 8a. A gas flow path 8b is provided on the gas diffusion layer 4b side of the separator 7b, and a cooling water flow path 9b is provided on the opposite side of the gas flow path 8b.

  In the polymer electrolyte fuel cell 10 shown in FIG. 1, an oxidant gas is caused to flow through the air electrode 5 through the gas passage 8 a and a fuel gas is caused to flow through the gas passage 8 b facing the fuel electrode 6. An electrode reaction involving proton conduction in the membrane 1 proceeds. As a result, an electromotive force is generated between the air electrode 5 and the fuel electrode 6. Further, cooling water flows through each of the cooling water passage 9a and the cooling water passage 9b provided in the separator 7a and the separator 7b. Here, as the oxidant gas, for example, a gas containing oxygen is used. Here, for example, hydrogen gas is used as the fuel gas. The polymer electrolyte fuel cell 10 shown in FIG. 1 is a polymer electrolyte fuel cell having a single cell structure. A plurality of cells may be stacked through a separator and connected in series to be used as one fuel cell.

  The polymer electrolyte fuel cell using the polymer electrolyte membrane using the polymer electrolyte of the present invention as a membrane electrode assembly has improved water resistance and durability, and therefore has a long life with excellent power generation performance. It becomes a fuel cell.

<Example 1>
(Synthesis of diphenylsulfone monomer)
6.38 g (20.0 mmol) of bis (4-hydroxy-3-chlorophenyl) sulfone was placed in a 500 mL eggplant flask and dissolved in 70 mL of ethanol. 1.68 g (42.0 mmol) of sodium hydroxide was added and stirred at 70 ° C. for 30 minutes. Next, 4.94 g (40.5 mmol) of 1,3-propane sultone was added, and the mixture was heated to reflux for 20 hours. The precipitated white solid was collected by filtration. The collected solid was washed with a water / ethanol solution and then filtered again. The filtrate was collected and dried under reduced pressure to obtain 7.84 g (white solid, yield 65%) of the desired product. From the above, the disodium salt of bis (4- (3′-sulfopropoxy) -3-chlorophenyl) sulfone, which is the target diphenylsulfone monomer M1, could be synthesized.

(Synthesis of macromonomer)
Into a three-necked flask, put 7.40 g (25.7 mmol) of 4,4′-dichlorodiphenylsulfone, 5.83 g (23.3 mmol) of bis (4-hydroxyphenyl) sulfone, and 4.20 g (30.3 mmol) of potassium carbonate. Then, nitrogen substitution, 150 mL of N, N dimethylacetamide (DMAc) and 20 mL of toluene were added, and the mixture was heated to reflux, and reacted while removing water in the system. After the reaction, 1.00 g (3.48 mmol) of 4,4′-dichlorophenylsulfone was added and further reacted at 180 ° C. for 4 hours. The solution after the reaction was poured into methanol for reprecipitation. The precipitate was collected by filtration, washed with water, and dried under reduced pressure at 105 ° C. for 2 hours. The collected solid was dissolved again in chloroform and poured into methanol for reprecipitation. The precipitate was collected by filtration and then dried under reduced pressure at 105 ° C. for 3 hours to obtain a macromonomer (white solid).

In Example 1, the obtained macromonomer had a polystyrene-equivalent weight average molecular weight of 5.3 × 10 ⁴ . The measurement conditions for the weight average molecular weight are shown below.

(Molecular weight)
Measured by gel permeation chromatography (GPC).
・ GPC device: HLC-8120GPC (manufactured by Tosoh Corporation)
Column: TSKgel SuperAWM-H (6.0 mm ID × 15 cm) connected in series. Detector: Differential refractometer (RI detector), Polarity = (+)
・ Eluent: N, N-dimethylformamide + LiBr + phosphoric acid ・ Flow rate: 0.6 mL / min
-Column temperature: 40 ° C
Sample concentration: 1 mg / mL
Sample injection volume: 20 μL

(Condensation polymerization reaction)
A polycondensation reaction between the diphenylsulfone monomer M1 and the macromonomer was performed. 0.50 g (0.823 mmol) of M1 was placed in a 50 mL Schlenk tube and dried under reduced pressure in an oil bath at 120 ° C. After drying, the Schlenk tube was purged with nitrogen, 200 mg of macromonomer, 359 mg of 2,2′-bipyridyl (2.30 mmol) and 4 mL of dehydrated dimethyl sulfoxide were added and dissolved at 120 ° C. After confirming that all were dissolved, the temperature was lowered to 80 ° C., and 0.63 g (2.29 mmol) of bis (1,5-cyclooctadiene) nickel (0) (Ni (cod) 2) was added to the mixture at 80 ° C. For 24 hours. After the reaction, the solution was added dropwise to methanol to precipitate a polymer, which was collected by filtration. The recovered polymer was washed with methanol again and protonated by stirring in 3N hydrochloric acid. The polymer was collected again by filtration, washed with water, and then dried under reduced pressure at 80 ° C. for 2 hours to obtain a polymer electrolyte P1. From the above, the polymer electrolyte of the present invention could be produced.

<Example 2>
In the same manner as in Example 1, a polymer electrolyte of the present invention was produced. However, in the synthesis of the macromonomer, the polymerization conditions were adjusted, and the weight average molecular weight of the macromonomer in terms of polystyrene was 7.0 × 10 ⁴ .

<Example 3>
Furthermore, the polymer electrolyte of the present invention was produced in the same manner as in Example 1. However, in the synthesis of the macromonomer, the polymerization conditions were adjusted, and the weight average molecular weight of the macromonomer in terms of polystyrene was 3.5 × 10 ⁴ .

<Comparative Example 1>
A polymer electrolyte was produced in the same manner as in Example 1. However, in the synthesis of the macromonomer, the polymerization conditions were adjusted so that the weight average molecular weight of the macromonomer in terms of polystyrene was 1.7 × 10 ⁴ .

<Comparative Example 2>
A polymer electrolyte was produced in the same manner as in Example 1. However, in the synthesis of the macromonomer, the polymerization conditions were adjusted, and the weight average molecular weight of the macromonomer in terms of polystyrene was 2.8 × 10 ⁴ .
<Measurement / Evaluation>
About Examples 1-3 and Comparative Examples 1-2, the measurement evaluation of the physical property was performed. The measurement items and evaluation results are shown below.

(Ion exchange capacity)
A polymer electrolyte in which the sulfonic acid group is in a free acid state was dried, weighed in a predetermined amount, stirred in a 2M aqueous sodium chloride solution overnight, and filtered. The filtrate was titrated with NaOH standard solution using phenolphthalein as an indicator, and the ion exchange capacity was determined from the neutralization point.

(Hot water swelling rate)
A polymer electrolyte is formed into a film thickness of 30 μm by a casting method, and the obtained solid polymer electrolyte membrane is cut into a 2 cm × 2 cm square, immersed in hot water at 80 ° C. for 30 minutes, and the length of one side Was measured, and the swelling ratio was measured.

(Proton conductivity)
A polymer electrolyte is deposited to a thickness of 30 μm by a casting method, and a platinum wire (φ = 0.5 mm) is pressed against the surface of the obtained solid polymer electrolyte membrane to hold the sample in a constant temperature and humidity device And obtained from an AC impedance measurement between platinum wires. That is, the impedance in alternating current was measured at 80 ° C. under a predetermined humidity environment. As a resistance measuring device, 5800 Frequency Response Analyzer manufactured by NF Circuit Design Block Co., Ltd. or 1260 type-1287 type manufactured by Solartron were used. A small environmental tester SH-221 or SH-241 manufactured by Espec Co., Ltd. was used as the constant temperature and humidity device. Four platinum wires were pressed at intervals of 5 mm, the distance between the wires was changed to 5 to 15 mm, and the AC resistance was measured. Membrane resistance was calculated from the distance between lines and the resistance value, and proton conductivity was calculated from this value.

(Evaluation results)
-Ion exchange capacity Example 1: 1.5 meq / g
Example 2: 1.0 meq / g
Example 3: 0.2 meq / g
Comparative Example 1: 1.7 meq / g
Comparative Example 2: 0.5 meq / g
Hot water swelling rate Example 1: 5%
Example 2: 4%
Example 3: 0%
Comparative Example 1: 25%
Comparative Example 2: 1%
Proton conductivity Example 1: 0.18 S / cm (80 ° C. relative humidity 95%)
Example 2: 0.18 S / cm (80 ° C., relative humidity 95%)
Example 3: Unmeasurable Comparative Example 1: 0.40 S / cm (80 ° C., relative humidity 95%)
Comparative Example 2: 0.01 S / cm (80 ° C. relative humidity 95%)

  As shown in Examples 1 and 2, the ion exchange capacity of the polymer electrolyte of the present invention is in the range of 0.5 meq / g or more and 4.0 meq / g or less, and is a solid polymer fuel It was confirmed to have an ion exchange capacity suitable for battery applications. Moreover, compared with the comparative example 1, in the Example, swelling was suppressed and the outstanding proton conductivity was shown.

  From the above, “the polystyrene-converted weight average molecular weight in the segment precursor that does not contain an ion exchange group is in the range of 30,000 to 300,000”. It was confirmed that the polymer electrolyte fuel cell has sufficient proton conductivity and ion exchange capacity, and that swelling is suppressed.

  The polymer electrolyte of the present invention can be widely used for various applications requiring proton conductivity as an electrolyte used in an electrochemical device. For example, it is expected to be used as an electrolyte for a polymer electrolyte fuel cell, a lithium ion secondary battery, an electric double layer capacitor, an actuator, and the like. In particular, it is expected to be suitably used as a member of a membrane electrode assembly in a polymer electrolyte fuel cell for in-vehicle power supply. However, the polymer electrolyte of the present invention is not limited to these uses.

DESCRIPTION OF SYMBOLS 1 ... Solid polymer electrolyte membrane 2a, 2b ... Electrode catalyst layer 3 ... Membrane electrode assembly 4a, 4b ... Gas diffusion layer 5 ... Air electrode 6 ... Fuel electrode 7a, 7b ... Separator 8a, 8b ...... Gas channel 9a, 9b ... Cooling water channel 10 ... Polymer fuel cell

Claims (7)

A polymer electrolyte comprising a block copolymer having an ion exchange group-containing segment and an ion exchange group-free segment,
The segment containing the ion exchange group is represented by the following general formula (1):
The segment not containing the ion exchange group is represented by the following general formula (2):
A polymer electrolyte, wherein a polystyrene-equivalent weight average molecular weight of a precursor of a segment not containing an ion exchange group is in a range of 30,000 to 300,000.

_{[R 1} and _{R 2} are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a-, _{- (CF 2) a -,} - O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of the linking groups (a is An integer greater than or equal to 2),
Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]

[Ar ¹ , Ar ² , Ar ³ , Ar ⁴ are each independently a divalent aromatic group.
B ₁ and B ₂ are each independently a divalent linking group, or each of them is not independently present, indicating that a divalent aromatic group is directly bonded without passing through B ₁ or B _2. .
C ₁ and C ₂ are each independently an oxygen atom or a sulfur atom.
b, c, d, and e are each independently 0 or 1.
n is an integer of 5 or more. ] The polymer electrolyte according to claim 1, wherein the segment including the ion exchange group is represented by the following general formula (3).

_{[R 1} and _{R 2} are each _{independently, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a-, _{- (CF 2) a -,} - O- (CF 2) a -, - S- (CF 2) a -, - NH- (CF 2) a-, selected from the group consisting of the linking groups (a is An integer greater than or equal to 2),
Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements. ]   3. The polymer electrolyte according to claim 1, wherein the ion exchange capacity of the polymer electrolyte is in the range of 0.5 meq / g or more and 4.0 meq / g or less.   The polymer electrolyte according to any one of claims 1 to 3, wherein a site other than the protonic acid group is crosslinked with a crosslinking agent to have a crosslinked structure. An electrode catalyst layer;
A solid polymer electrolyte membrane joined to the electrode catalyst layer,
The said polymer electrolyte membrane contains the polymer electrolyte as described in any one of Claims 1-4, The membrane electrode assembly characterized by the above-mentioned.   6. The polymer electrolyte membrane electrode assembly according to claim 5, wherein the solid polymer electrolyte membrane has a hot water expansion coefficient of 10% or less.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 5.

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