JP6108587B2 - POLYMER ELECTROLYTE, MEMBRANE ELECTRODE ASSEMBLY, SOLID POLYMER FUEL CELL, AND METHOD FOR PRODUCING POLYMER ELECTROLYTE - Google Patents

Description

The techniques of this disclosure, high-molecular electrolyte, membrane electrode assembly, a polymer electrolyte fuel cell, and a method of manufacturing a polyelectrolyte.

  In recent years, fuel cells have attracted attention as an effective power source for solving environmental problems and energy problems. In a fuel cell, fuel such as hydrogen is oxidized by an oxidant such as oxygen, and chemical energy generated at this time is converted into electric energy. Among the fuel cells, since the polymer main body of the polymer electrolyte fuel cell is small, the polymer electrolyte fuel cell is particularly expected as an in-vehicle power source or a home stationary power source.

  In a polymer electrolyte fuel cell, an electrode reaction proceeds by proton conduction in an electrolyte. As electrolytes for polymer electrolyte fuel cells, many perfluoro-based electrolytes represented by Nafion (DuPont: registered trademark) have been proposed so far. However, while perfluoro-based electrolytes exhibit high proton conductivity, they require complex synthetic routes for their production. Therefore, the cost of the polymer electrolyte fuel cell must be increased. In addition, since the glass transition temperature is lower than the endurance temperature required for in-vehicle power supplies, there is a problem that durability under high temperature and low humidity is low.

  Therefore, development of hydrocarbon polymer electrolytes has been promoted for the electrolytes of the above-described polymer electrolyte fuel cells. Examples of the hydrocarbon polymer electrolyte include aromatic hydrocarbons obtained by sulfonating engineering plastics such as sulfonated polyetheretherketone (see Patent Document 1) and sulfonated polyethersulfone (see Patent Document 2). Molecular electrolytes have been proposed. Since these aromatic hydrocarbon polymer electrolytes are easier to manufacture than Nafion, the manufacturing costs can be reduced.

JP-A-6-93114 JP-A-9-245818

  However, in the above-described aromatic hydrocarbon polymer electrolyte, when the hydrophilic group in the polymer is increased in order to increase proton conductivity and ion exchange capacity, the electrolyte easily swells with moisture. Therefore, in the above-described aromatic hydrocarbon polymer electrolyte, it is desired to suppress swelling in order to increase proton conductivity and ion exchange capacity.

The techniques of this disclosure has been made in view of such circumstances, and its object is that of possible high molecular electrolyte to suppress swelling, membrane electrode assembly, a polymer electrolyte fuel cell and, a polymer The object is to provide a method for producing an electrolyte.

  One aspect of the diphenylsulfone compound for polymer electrolytes in the present disclosure is represented by the following general formula (1).

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 -, and, -NH- _{(CF 2) a} - linking group selected from the group consisting of (a 2 It is an integer above. X ₁ and X ₂ each independently represent a halogen atom, and Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements.

  According to one embodiment of the diphenylsulfone compound for polymer electrolyte in the present disclosure, the ion exchange group is kept away from the benzene ring by providing a linking group. Therefore, swelling of the electrolyte can be suppressed by forming the polymer electrolyte in which the diphenylsulfone group is a repeating unit from the group based on the diphenylsulfone compound.

  One aspect of the diphenylsulfone compound for polymer electrolyte in the present disclosure is represented by the following general formula (2).

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 -, and, -NH- _{(CF 2) a} - linking group selected from the group consisting of (a 2 It is an integer above. X ₁ and X ₂ are each independently a halogen atom, and Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements.

According to one embodiment of the diphenylsulfone compound for polymer electrolyte in the present disclosure, the production is easy and the yield is increased.
The gist of one aspect of the polymer electrolyte in the present disclosure is that the main chain contains a repeating unit 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 -, and, -NH- _{(CF 2) a} - linking group selected from the group consisting of (a 2 It is an integer above. Y ₁ and Y ₂ are each independently an atom selected from the group consisting of Group 1 elements and Group 2 elements.

  According to one aspect of the polymer electrolyte in the present disclosure, the benzene ring constituting the main chain and the ion exchange group are kept away by providing the linking group. Therefore, since the hydrophilic group is moved away from the main chain, the hydrophilicity of the main chain is lowered, so that swelling as a polymer electrolyte can be suppressed.

  One aspect of the polymer electrolyte in the present disclosure is a block copolymer in which the polymer electrolyte includes a block containing a repeating unit represented by the general formula (3) and a block containing no ion exchange group in the main chain. It is a summary.

According to one aspect of the polymer electrolyte in the present disclosure, a phase having ion exchange properties and a phase having no ion exchange properties are separated, and thus proton conductivity is improved.
One aspect of the polymer electrolyte in the present disclosure is that the block not including the ion exchange group is represented by the following general formula (4).

Ar ¹ , Ar ² , Ar ³ , and 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.

  According to one aspect of the polymer electrolyte in the present disclosure, the above-described phase having no ion exchange properties is constituted by a polymer having high mechanical strength, and thus the mechanical strength as an electrolyte can be increased.

One aspect of the polymer electrolyte in the present disclosure is that the ion exchange capacity is 0.5 meq / g or more and 4.0 meq / g or less.
According to one aspect of the polymer electrolyte in the present disclosure, when the ion exchange capacity is in the above range, proton conductivity is improved, and water resistance and mechanical strength are increased.

The gist of one aspect of the polymer electrolyte in the present disclosure is that it includes a crosslinked structure in which a portion other than the protonic acid group of the polymer electrolyte is crosslinked with a crosslinking agent.
According to one aspect of the polymer electrolyte in the present disclosure, since a crosslinked structure is formed in the polymer, the mechanical strength as the electrolyte can be increased.

  One aspect of the method for producing a polymer electrolyte in the present disclosure is that a polymer contained in an electrolyte is produced by polymerizing a diphenylsulfone compound represented by the following general formula (5) in the presence of a metal complex. To do.

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 -, and, -NH- _{(CF 2) a} - linking group selected from the group consisting of (a 2 X ₁ and X ₂ are each independently a halogen atom, and Y ₁ and Y ₂ are each independently an atom selected from the group consisting of a Group 1 element and a Group 2 element. is there.

According to one aspect of the method for producing a polymer electrolyte in the present disclosure, a polymer electrolyte with suppressed swelling can be obtained.
One aspect of the method for producing a polymer electrolyte in the present disclosure is that the metal complex is a nickel complex or a palladium complex.

According to one aspect of the method for producing a polymer electrolyte in the present disclosure, the reaction efficiency of the polymerization reaction can be increased and the reaction can be performed under mild conditions.
In one embodiment of the method for producing a polymer electrolyte in the present disclosure, the metal complex is a nickel complex, and the nickel complex is obtained from bis (cyclooctadiene) nickel (0) and 2,2′-bipyridyl. It is a summary.

  According to one aspect of the method for producing a polymer electrolyte in the present disclosure, the polymer electrolyte can be produced from a readily available material. In particular, when synthesizing a block copolymer, the reaction efficiency of the polymerization reaction can be increased.

  One aspect of the membrane electrode assembly in the present disclosure is a membrane electrode assembly including an electrode catalyst layer and a solid polymer electrolyte membrane bonded to the electrode catalyst layer, wherein the solid polymer electrolyte membrane is the above It is summarized that the polymer electrolyte is included.

According to one aspect of the membrane electrode assembly in the present disclosure, the reliability as a membrane electrode assembly can be increased by using a polymer electrolyte with suppressed swelling.
The gist of one aspect of the polymer electrolyte fuel cell according to the present disclosure includes the membrane electrode assembly.

  According to one aspect of the solid polymer fuel cell in the present disclosure, the use of a polymer electrolyte with suppressed swelling can improve the power generation performance as a fuel cell and extend the life.

  According to the technique of the present disclosure, it is possible to suppress swelling of the polymer electrolyte.

It is a disassembled perspective view which decomposes | disassembles and shows the perspective structure about one Embodiment of the membrane electrode assembly in this indication, and a polymer electrolyte fuel cell. It is a ¹ H-NMR spectrum (solvent is deuterated chloroform) of white solid m1 obtained in Example 1 (1). It is IR spectrum of white solid m1 obtained in Example 1 (1). It is a ¹ H-NMR spectrum (a solvent is deuterated chloroform) of white solid m2 obtained in Example 1 (2). It is IR spectrum of white solid m2 obtained in Example 1 (2). It is a ¹ H-NMR spectrum (solvent is deuterated dimethyl sulfoxide) of white solid m3 obtained in Example 1 (3). It is IR spectrum of white solid m3 obtained in Example 1 (3). It is a ¹ H-NMR spectrum (solvent is heavy water) of the white solid M1 obtained in Example 1 (4). It is IR spectrum of white solid M1 obtained in Example 1 (4). ^{1 is} a ¹ H-NMR spectrum (solvent is heavy water) of white solid M2 obtained in Example 2. 3 is an IR spectrum of white solid M2 obtained in Example 2. It is a ¹ H-NMR spectrum (solvent is heavy water) of dark brown solid P1 obtained in Example 3. 4 is an IR spectrum of dark brown solid P1 obtained in Example 3. It is a ¹ H-NMR spectrum (solvent is heavy water) of the brown solid P2 obtained in Example 4. 4 is an IR spectrum of brown solid P2 obtained in Example 4. ^{1 is} a ¹ H-NMR spectrum (solvent is deuterated dimethyl sulfoxide) of brown solid P4 obtained in Example 6. It is IR spectrum of the brown solid P4 obtained in Example 6.

  Hereinafter, an embodiment of a diphenylsulfone compound for a polymer electrolyte, a polymer electrolyte, a membrane electrode assembly, a solid polymer fuel cell, and a method for producing a polymer electrolyte of the present disclosure will be described.

[Monomer of diphenylsulfone compound]
First, a diphenylsulfone monomer that is a diphenylsulfone compound for a polymer electrolyte will be described.

The diphenylsulfone monomer is represented by the following general formula (6). The diphenylsulfone monomer includes —SO ₃ Y group that is an ion exchange group and —X that is a halogen group.

An ion exchange group is a group that contributes to ionic conduction when a diphenylsulfone compound in a polymer is used as a polymer electrolyte. In particular, when used as an electrolyte of a polymer electrolyte fuel cell, the ion exchange group contributes to the ptron conduction. -SO ₃ ^- Y ⁺ groups Y ⁺ is hydrogen ion, lithium ion, sodium ion, potassium ion, alkali metal ions of rubidium ions, and magnesium ions, calcium ions, strontium ions, and barium ions the Any one selected from the group consisting of group 2 element ions. Y ₁ and Y ₂ 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.

The halogen group is a group composed of halogen atoms such as fluorine, chlorine, bromine and iodine. X ₁ and X ₂ may be different atoms, but if they are the same atom, synthesis of the diphenylsulfone monomer is facilitated. In order to facilitate the production of the polymer, the halogen group is preferably chlorine or bromine. Whether the halogen group is chlorine or bromine is selected according to the polymerization method.

The diphenylsulfone monomer has R as a linking group between the —SO ₃ Y group and the benzene ring. R _{is, - (CH 2) a -} , - O- (CH 2) a -, - S- (CH 2) a -, - NH- (CH 2) a -, - (CF 2) a -, - It is any one selected from the group consisting of O— (CF ₂ ) _a —, —S— (CF ₂ ) _a —, and —NH— (CF ₂ ) _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. R ₁ and R ₂ may be different linking groups, but if they are the same linking group, synthesis of the diphenylsulfone monomer is facilitated.

  As shown in the following general formula (7), the halogen group is preferably bonded to the meta position with respect to the sulfonyl group. The linking group is preferably bonded to the para position with respect to the sulfonyl group. 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 diphenylsulfone monomer is facilitated and the yield is also increased.

  Specific examples of the diphenylsulfone monomer represented by the general formula (7) include compounds represented by the following general formula. The following compounds can be synthesized relatively easily among the diphenylsulfone monomers represented by the general formula (7).

  Generally, a polyarylene type polymer electrolyte whose main chain is composed of an aromatic ring has an ion exchange group directly bonded to the aromatic ring. In such a structure, since the main chain itself has hydrophilicity and the stack of polymer main chains is inhibited, the presence of water molecules around the main chain is stabilized, resulting in swelling of the polymer electrolyte. The term “stack” means that polymer main chains are physically connected by weak interaction such as van der Waals force.

  In contrast, in the diphenylsulfone compound of the present embodiment, the ion exchange group and the benzene ring are kept away by providing a linking group. Therefore, in the polymer electrolyte using this diphenylsulfone compound, the decrease in water resistance is suppressed, and swelling hardly occurs. Furthermore, since the ion exchange group easily moves due to the mobility of the linking group, proton conductivity is also improved.

[Monomer production method]
Next, the manufacturing method of the above-mentioned diphenyl sulfone monomer is demonstrated. Here, among the diphenylsulfone monomers represented by the general formula (7), R ₁ and R ₂ are —O— (CH ₂ ) _a — groups, X ₁ and X ₂ are bromine, Y ₁ and Y A production method when ₂ is a group 1 atom will be described.

  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 (8) is obtained. In the following general formula (8), 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 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.

According to such materials and reaction conditions, the compound represented by the general formula (8) can be obtained with high yield.
Next, the compound represented by the general formula (8) is treated with bromine. As a result, a dibrominated compound represented by the following general formula (9) is obtained.

  The amount of bromine is preferably 20 mol% or more and 300 mol% or less, more preferably 200 mol% or more and 250 mol% or less, relative to 100 mol% of the compound represented by the general formula (8). 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.

According to such materials and reaction conditions, the compound represented by the general formula (9) can be obtained with high yield.
Next, the compound represented by the general formula (9) 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 (10) is obtained.

  The amount of the Lewis acid is preferably 200 mol% or more and 400 mol% or less, and preferably 200 mol% or more and 300 mol% or less with respect to 100 mol% of the compound represented by the general formula (9). 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.

According to such materials and reaction conditions, the compound represented by the general formula (10) can be obtained with high yield.
Next, the compound represented by the general formula (10) is treated with an inorganic base and reacted with sultone, which is a ring-opening compound. Thereby, the diphenyl sulfone monomer shown by the following general formula (11) is obtained.

  As the base, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like are preferable. 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 (10). .

  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.

According to such materials and reaction conditions, the diphenylsulfone monomer represented by the general formula (11) can be obtained with high yield.
Even if the diphenylsulfone monomer represented by the general formula (11) is different from R ₁ , R ₂ , X ₁ , X ₂ , Y ₁ , Y ₂ , the method according to the above production method is used. Thus, a diphenylsulfone monomer can be obtained.

[Polymer electrolyte]
Next, the polymer electrolyte will be described. The polymer electrolyte has a structural unit represented by the following general formula (12) in the main chain.

In the general formula (12), R ₁ and R ₂ each independently represent — (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, -NH- _{(CF 2) a} - from the group consisting of The linking group selected. A is an integer of 2 or more. Y ₁ and Y ₂ are any atoms selected from the group consisting of Group 1 elements and Group 2 elements. When this polymer electrolyte is used as an electrolyte membrane of a polymer electrolyte fuel cell, it is preferable that Y ₁ and Y ₂ are all hydrogen atoms because protons can be released.

  The polymer electrolyte may be a homopolymer or a copolymer as long as it has the structural unit of the general formula (12). The mode of copolymerization is selected from random copolymerization, alternating copolymerization, block copolymerization, and graft copolymerization. When the polymer electrolyte is used as an electrolyte membrane of a polymer electrolyte fuel cell, there are a block having an ion exchange group composed of the structural unit represented by the general formula (12) and a block having no ion exchange group. A block copolymer which is directly bonded to form a main chain is preferable.

  In the block copolymer, a portion having ion exchange properties and a portion having no 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 block having no ion exchange group is one having an average number of ion exchange groups of 0.1 or less per repeating unit. In order to increase proton conductivity as an electrolyte membrane of a polymer electrolyte fuel cell, it is preferable that the number of ion exchange groups per repeating unit is 0, that is, no ion exchange groups are contained.

  In particular, the block having no ion exchange group is preferably a block containing a structural unit represented by the following general formula (13).

In the general formula (13), Ar ¹ , Ar ² , Ar ³ and Ar ⁴ each independently represent a divalent aromatic group. B ₁ , B ₂ , C ₁ , C ₂ , b, c, d, and e are the same as those in the general formula (4). The divalent aromatic group may be substituted with a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a nitrile group, or the like. In addition, these alkyl groups and alkoxy groups may have a substituent.

In addition, B ₁ and B ₂ are each independently a divalent linking group, or each of them is not present independently, and a divalent aromatic group is directly bonded without passing through B ₁ or B ₂ . Indicates. In particular, a group based on a carbonyl group, a sulfonyl group, a 2,2-isopropylidene group, a 2,2-hexafluoroisopropylidene group, or a 9,9-2 substituted fluorene is preferable.

C ₁ and C ₂ each independently represent an oxygen atom or a sulfur atom.
B, c, d, and e each independently represent 0 or 1. 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.

  The following structure is mentioned as a structural unit of the block which does not have an ion exchange group shown by the said General formula (13). In addition, n is defined similarly to the said General formula (13). The following structure allows the polymer to be synthesized relatively easily among the structures represented by the general formula (13).

  The amount of ion exchange groups introduced into the polymer electrolyte is preferably 0.5 meq / g or more and 4.0 meq / g or less, expressed as ion exchange capacity, and is 1.0 meq / g or more and 3.0 or less. It is more preferable that it is milliequivalent / 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 has a molecular weight expressed as a polystyrene-equivalent number average molecular weight, and is preferably 5,000 to 1,000,000, and more preferably 10,000 to 500,000. When the molecular weight is 5000 or more, when used as an electrolyte membrane of a polymer electrolyte fuel cell, the film formability and mechanical strength of the membrane are improved. Moreover, since the molecular weight is 1000000 or less, the production of the film becomes easier.

  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. At this time, another polymer may be added to improve mechanical strength and water resistance.

  Other polymers added include aromatic polyether, aromatic polyether ketone, aromatic polyether ether ketone, aromatic polyether sulfone, aromatic polysulfone, aromatic polyether nitrile, aromatic polyether pyridine, Aromatic polyimide, aromatic polyamide, aromatic polyamideimide, aromatic polyazole, aromatic polyester, aromatic polycarbonate and the like can be mentioned. These polymers may be sulfonated or may not be sulfonated.

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.

[Production method of polymer electrolyte]
Next, a method for producing a polymer electrolyte will be described.
The polymer electrolyte can be synthesized by homopolymerizing or copolymerizing the diphenylsulfone monomer represented by the following general formula (14) described above by a condensation reaction using a transition metal complex. In the following general formula (14), R ₁ , R ₂ , X ₁ , X ₂ , Y ₁ and Y ₂ are defined in the same manner as in the general formula (7).

  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. The transition metal complex may be a commercially available product or may be synthesized separately. Examples of the method for synthesizing the transition metal complex include a method in which a transition metal halide or transition metal oxide is reacted with a ligand to synthesize the transition metal complex. The synthesized transition metal complex may be taken out from the reaction system and used, or may be used in situ without being taken out.

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

Below, the manufacturing method of the polymer electrolyte which consists of a block copolymer is demonstrated.
When synthesizing the block copolymer, it is preferable to use a zero-valent transition metal complex such as a zero-valent nickel complex or a zero-valent palladium complex as the transition metal complex, and it is particularly preferable to use a zero-valent 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, a commercially available product may be used as described above, or a separately synthesized product may be used. As a method for synthesizing the zero-valent transition metal complex, a known method such as a method of reducing the transition metal compound to a zero valence by using a reducing agent such as zinc or magnesium can be used. The synthesized zero-valent transition metal complex may be used after being taken out from the reaction system, or may be used in situ without being taken out.

  Examples of the reducing agent 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.

The block copolymer is a divalent sulfone monomer represented by the above general formula (14) and a block precursor (macromonomer) having no ion exchange group represented by the following general formula (15). It is synthesized by condensation polymerization in the presence of a metal complex. In the following general formula (15), Ar ¹ , Ar ² , Ar ³ , Ar ⁴ , B ₁ , B ₂ , C ₁ , C ₂ , b, c, d, e, and n are represented by the general formula (13). ). Z represents a leaving group in the condensation reaction, and may be the same or different.

Examples of the leaving group, for example, a chlorine atom, a bromine atom, a halogen atom such as iodine atom, p- toluenesulfonyloxy group _{(CH 3 C 6 H 4 -p} -SO 3 -), methanesulfonyloxy group (CH ₃ SO ₃ —), trifluoromethanesulfonyloxy group (CF ₃ SO ₃ —) and the like.

  Examples of the macromonomer represented by the general formula (15) include compounds having the following structure. These macromonomers are easily available from the market, or can be produced by a known method using raw materials that are easily available from the market. Z is defined as in the general formula (15).

  The compound represented by the above general formula (16), in which Z is a chlorine atom, can be synthesized as shown in the following reaction formula (18) or reaction formula (19) based on a known method. A compound represented by the above general formula (17), in which Z is a chlorine atom, can be synthesized as shown in the following reaction formula (20) based on a known method. In addition, n is defined similarly to the said General formula (13). By adding a dichloro compound as a starting material just before the end of the polymerization reaction, it is possible to synthesize the macromonomer whose both ends are chlorine atoms.

  When the diphenylsulfone monomer represented by the general formula (14) and the macromonomer represented by the general formula (15) are subjected to a condensation reaction using the transition metal complex, the transition metal complex used It is preferable to add a compound that can be a ligand. 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 10 mol% or more with respect to 100 mol% of the diphenylsulfone monomer represented by the general formula (14). 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 polymer is sufficiently dissolved in the solvent. Therefore, tetrahydrofuran, 1,4-dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, toluene and the like, which are good solvents for the polymer, are used. It is preferable. 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 total concentration of the diphenylsulfone monomer represented by the general formula (14) 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 shown by the said General formula (15) 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.

  A block copolymer is synthesized by such a method. 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.

  When used as an electrolyte membrane of a polymer electrolyte fuel cell, when the sulfonic acid group in the produced block copolymer is in the form of a salt such as sodium salt, the sulfonic acid group is converted into a free acid form. It is preferable to convert. 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.

It should be noted that polymers other than the block copolymer can also be produced according to the above production method using a known method.
[Method of manufacturing electrolyte membrane]
The polymer electrolyte obtained by the above-described production method can be used as a proton conductive membrane for electrochemical devices such as fuel cells. A method for manufacturing such an electrolyte membrane will be described.

  As a method for converting into a film, for example, a method (such as a casting method) in which a polymer electrolyte in a solution state is coated on a substrate and formed into a film is preferably used. As a base material, what is necessary is just a base material used for the normal solution casting method, for example, glass, plastics, metal, etc. are used. In particular, a substrate made of a thermoplastic resin such as a polyethylene terephthalate (PET) film is preferably used.

  The solvent used for film formation is not particularly limited as long as the polymer electrolyte can be dissolved 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.

  The thickness of the film is preferably 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 80 μm or less. When the film thickness is 5 μm or more, the strength is increased to a practical size. Moreover, since film resistance becomes it small that a film thickness is 300 micrometers or less, the characteristic of an electrochemical device improves more. The film thickness can be controlled by the concentration of the solution and the coating thickness on the substrate.

  In addition, for the purpose of improving various physical properties of the film, it is possible to add plasticizers, stabilizers, mold release materials and the like used in ordinary polymers. It is also possible to composite-alloy other polymers with the polymer electrolyte of the present embodiment by a method such as mixing and co-casting in the same solvent.

  Further, when used as an electrolyte membrane of a polymer electrolyte fuel cell, inorganic or organic fine particles may be added as a water retention agent in order to facilitate water management. Further, for the purpose of improving the mechanical strength of the film, it may be crosslinked by irradiating with an electron beam, radiation or the like.

  Further, in order to improve the strength, flexibility and durability of the membrane, it is possible to produce a composite electrolyte membrane in which the polymer electrolyte of the present embodiment is used as an active ingredient and this is impregnated into a porous substrate. A known method can be used as the compounding method.

  The porous substrate is selected according to the above-mentioned purpose. For example, porous membranes, nonwoven fabrics, fibrils and the like can be used regardless of their shapes and materials. When an aliphatic, aromatic polymer, or fluorine polymer is used as the material for the porous substrate, the heat resistance is improved and the physical strength is increased.

  The polymer electrolyte of the present embodiment can be used as an electrolyte for electrochemical devices such as lithium ion secondary batteries, electric double layer capacitors, and actuators in addition to the above-described solid polymer fuel cells.

[Polymer fuel cell]
Next, the polymer electrolyte fuel cell will be described. First, the structure of the polymer electrolyte fuel cell will be described with reference to FIG.

  As shown in FIG. 1, a solid polymer fuel cell 10 is configured as a laminate centering on a solid polymer electrolyte membrane 1 made of the above-described polymer electrolyte. The solid polymer electrolyte membrane 1 is provided with a pair of electrode catalyst layers 2a and 2b facing each other with the solid polymer electrolyte membrane 1 interposed therebetween. A membrane / electrode assembly 3 is constituted by the solid polymer electrolyte membrane 1 and the electrode catalyst layers 2a and 2b.

  Each of the electrode catalyst layers 2a and 2b is covered with a solid polymer electrolyte membrane 1 and a pair of gas diffusion layers 4a and 4b facing each other with the electrode catalyst layers 2a and 2b interposed therebetween. Among these, the electrode catalyst layer 2a and the gas diffusion layer 4a on one side of the solid polymer electrolyte membrane 1 serve as an air electrode (cathode) 5, and the electrode catalyst layer 2b and the gas diffusion layer 4b on the other side serve as a fuel electrode (anode). ) 6.

  Further, the membrane electrode assembly 3 and the gas diffusion layers 4a and 4b are sandwiched between a pair of separators 7a and 7b facing each other. Separator 7a, 7b is formed from an electroconductive and impermeable material. In each of the separators 7a and 7b, gas flow paths 8a and 8b are recessed on the side surfaces facing the gas diffusion layers 4a and 4b, and cooling is provided on the side surface opposite to the gas diffusion layers 4a and 4b. Water flow paths 9a and 9b are recessed.

  In the polymer electrolyte fuel cell 10 configured as described above, a gas containing oxygen, for example, flows as an oxidant gas in the gas flow path 8 a of the separator 7 a facing the air electrode 5, and faces the fuel electrode 6. For example, hydrogen gas is allowed to flow as a fuel gas through the gas flow path 8b of the separator 7b. Further, cooling water flows through each of the cooling water flow paths 9a and 9b of the separators 7a and 7b. Then, by supplying gas from the gas flow paths 8a and 8b to the air electrode 5 and the fuel electrode 6, an electrode reaction accompanied by proton conduction in the solid polymer electrolyte membrane 1 proceeds, whereby the air electrode 5 An electromotive force is generated between the fuel electrode 6 and the fuel electrode 6.

  In the solid polymer fuel cell 10 shown in FIG. 1, the solid polymer electrolyte membrane 1, the electrode catalyst layers 2a and 2b, and the gas diffusion layers 4a and 4b are sandwiched between a pair of separators 7a and 7b. The polymer electrolyte fuel cell having a cell structure may be used as a single fuel cell by stacking a plurality of cells via separators 7a and 7b and connecting them in series.

Subsequently, materials and manufacturing methods of respective parts constituting the polymer electrolyte fuel cell will be described.
(Electrode catalyst layer)
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.

  The electrode catalyst layer is formed by embedding the catalyst-supporting carbon particles in the polymer electrolyte of the present embodiment or the polymer electrolyte of the present embodiment in which organic substances are mixed and removed by acid treatment. The electrode catalyst layer is obtained by applying an electrode catalyst ink in which the catalyst-supporting carbon particles and the polymer electrolyte are dispersed in a solvent to a substrate and drying the substrate.

  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.

  As the substrate on which the electrode catalyst ink is applied, a gas diffusion layer sandwiching the electrode catalyst tank, a solid polymer electrolyte membrane sandwiched between the electrode catalyst layers, or a transfer sheet can be used. The transfer sheet may be any material that has good transferability. As a method for applying the electrode catalyst ink, a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spray method, or the like can be used.

(Solid polymer electrolyte membrane)
The solid polymer electrolyte membrane is manufactured by the above-described method for manufacturing an electrolyte membrane using the polymer electrolyte of the present embodiment.

(Membrane electrode assembly)
The membrane / electrode assembly is obtained by bonding an electrode catalyst layer and a conductive material as a current collector to a solid polymer electrolyte membrane. A known material can be used as the conductive material as the current collector. In particular, porous carbon woven fabric, carbon nonwoven fabric and carbon paper are preferably used. Since these materials can efficiently transport the source gas to the catalyst, they can be used as a gas diffusion layer.

  When a transfer sheet is used as the substrate for forming the electrode catalyst layer, the electrode catalyst layer is formed on both sides of the solid polymer electrolyte membrane by peeling the transfer sheet after bonding the electrode catalyst layer to the solid polymer electrolyte membrane. A membrane electrode assembly is provided.

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.
(Gas diffusion layer and separator)
As the gas diffusion layer and the separator, those used in known fuel cells can be used. The gas diffusion layer may be made of a material having gas diffusibility and conductivity, and for example, a porous carbon material such as carbon cloth, carbon paper, and non-woven fabric can be used. As the separator, a carbon type or metal type can be used.

  A polymer electrolyte fuel cell is manufactured by assembling the above-described components and accompanying devices such as a gas supply device and a cooling device. Since the solid polymer electrolyte membrane comprising the polymer electrolyte of the present embodiment has improved water resistance and durability, the solid polymer fuel cell equipped with such a solid polymer electrolyte membrane has excellent power generation performance. It becomes a long-life fuel cell.

  The above-described diphenylsulfone compound for polymer electrolyte, polymer electrolyte, membrane electrode assembly, solid polymer fuel cell, and method for producing the polymer electrolyte will be described below with specific examples. In Examples, the ion exchange capacity, proton conductivity, hot water swelling ratio, tensile breaking strength, and molecular weight were determined as follows.

(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.

(Proton conductivity)
The AC resistance was obtained from the measurement of AC impedance between platinum wires by pressing a platinum wire (φ = 0.5 mm) against the surface of the strip-shaped polymer electrolyte membrane and holding the sample in a constant temperature and humidity device. 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 SI1260 manufactured by Solartron was 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.

(Hot water swelling rate)
The electrolyte membrane was cut into a 2 cm × 2 cm square, immersed in hot water at 80 ° C. for 30 minutes, the length of one side was measured, and the swelling rate was measured.

(Tensile strength at break)
A universal testing machine (Type 4443) manufactured by Instron was used, and the conditions were a film width of 1 cm, a distance between chucks of 1 cm, and a tensile speed of 1 cm / min.

(Molecular weight)
Measured by gel permeation chromatography (GPC).
・ GPC device: HLC-8220GPC (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 Flow rate: 0.6 mL / min
-Column temperature: 40 ° C
Sample concentration: 1 mg / mL
Sample injection volume: 20 μL
Proton NMR was measured by using JEOL JNM-LA300 spectrometer and deuterated chloroform, deuterated dimethyl sulfoxide or deuterated water as heavy solvent. IR was measured by the KBr pellet method using JASCO FT / IR-460plus.

(Synthesis of diphenylsulfone monomer)
[Example 1]
<Synthesis of disodium salt of bis (4- (3′-sulfopropoxy) -3-bromophenyl) sulfone>
(1) Synthesis of bis (4-dodecyloxyphenyl) sulfone (m1)

  50.0 g (0.20 mol) of 4,4′-dihydroxydiphenylsulfone was placed in a 1 L eggplant flask, and 400 mL of DMF was added and dissolved. Subsequently, 69.1 g (0.50 mol) of potassium carbonate 124.9 g (0.50 mol) of 1-bromododecane was added and stirred at 80 ° C. for 12 hours. After the reaction, water was added and the precipitate was filtered. The filter residue was dissolved in chloroform and reprecipitated twice with methanol. The obtained solid was dried under reduced pressure to obtain 114.75 g of bis (4-dodecyloxyphenyl) sulfone (yield 98%, white solid).

The ¹ H-NMR spectrum of the obtained white solid is shown in FIG. In addition, deuterated chloroform was used as the heavy solvent. Moreover, IR spectrum of the obtained white solid is shown in FIG.
(2) Synthesis of bis (4-dodecyloxy-3-bromophenyl) sulfone (m2)

  Bis (4-dodecyloxyphenyl) sulfone (50.2 g, 85.5 mmol) was placed in a 500 mL eggplant flask, suspended in hydrobromic acid (80 mL), and bromine (11 mL, 213 mmol) was added. After stirring this at 80 ° C. for 12 hours, an aqueous sodium hydrogen sulfite solution was added, and after confirming that the color of bromine had disappeared, chloroform was added to carry out a liquid separation operation. The chloroform solution was washed with a sodium hydrogen carbonate solution, dried over magnesium sulfate, concentrated, and reprecipitated in methanol. The precipitated solid was collected by filtration and dried under reduced pressure to obtain 56.4 g (yield 88%, white solid) of bis (4-dodecyloxy-3-bromophenyl) sulfone.

FIG. 4 shows the ¹ H-NMR spectrum of the obtained white solid. In addition, deuterated chloroform was used as the heavy solvent. Moreover, IR spectrum of the obtained white solid is shown in FIG.
(3) Synthesis of bis (4-hydroxyl-3-bromophenyl) sulfone (m3)

  Bis (4-dodecyloxy-3-bromophenyl) sulfone (30.4 g, 40.8 mmol) was placed in a 500 mL eggplant flask and dissolved in chloroform (200 mL). The flask was cooled in an ice bath, and 17.0 g (127.5 mmol) of aluminum chloride was added and stirred for 2 hours. Thereafter, the mixture was gradually returned to room temperature and further stirred for 2 hours. After the reaction, the solution was put into ice water and stirring was continued for 30 minutes. The precipitate was collected by filtration, the filtrate was dissolved again in ethanol, chloroform, hexane and water were added, the separated oil layer was removed, and the precipitate was collected. This operation was repeated twice. The resulting solid was placed in 1N hydrochloric acid and stirred overnight. The solid was filtered, washed with distilled water, and dried under reduced pressure to obtain 15.7 g (white solid, 94% yield) of bis (4-hydroxyl-3-bromophenyl) sulfone.

FIG. 6 shows the ¹ H-NMR spectrum of the obtained white solid. Heavy dimethyl sulfoxide was used as the heavy solvent. The IR spectrum of the obtained white solid is shown in FIG.
(4) Synthesis of disodium salt of bis (4- (3′-sulfopropoxy) -3-bromophenyl) sulfone (M1)

  Bis (4-hydroxyl-3-bromophenyl) sulfone 4.5 g (11.0 mmol) was placed in a 200 mL flask and dissolved in 80 mL ethanol. 0.96 g (24.0 mmol) of sodium hydroxide was added and stirred at 80 ° C. for 30 minutes. 2.86 g (23.4 mmol) of 1,3-propane sultone was added and stirred at 80 ° C. for 20 hours. After the reaction, the precipitate 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, and then 6.59 g of M1, which is the diphenylsulfone compound of Example 1, (white solid, yield 86%) Obtained.

The ¹ H-NMR spectrum of the obtained white solid is shown in FIG. Heavy water was used as the heavy solvent. Moreover, IR spectrum of the obtained white solid is shown in FIG.
[Example 2]
<Synthesis of disodium salt of bis (4- (3′-sulfopropoxy) -3-chlorophenyl) sulfone (M2)>

  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, 1.94 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. Then, 7.84 g of M2, which is the diphenylsulfone compound of Example 2, (white solid, yield 65%) Obtained.

A ¹ H-NMR spectrum of the obtained white solid is shown in FIG. Heavy water was used as the heavy solvent. Moreover, IR spectrum of the obtained white solid is shown in FIG.
(Synthesis of homopolymer)
[Example 3]
<Synthesis of Diphenylsulfone Compound Homopolymer (P1)>

  A 50 mL Schlenk tube was charged with 1.0 g (1.64 mmol) of M2 and 0.06 g (0.16 mmol) of hexadecyltrimethylammonium bromide, and the Schlenk tube was purged with nitrogen to give 718 mg (4.60 mmol) of 2,2′-bipyridyl. 8 mL of dehydrated dimethyl sulfoxide was added and dissolved at 80 ° C. After confirming that all were dissolved, 1.26 g (4.58 mmol) of bis (cyclooctadiene) nickel (0) was added and stirred 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 again with methanol, dissolved in 1N hydrochloric acid, and dialyzed while exchanging water for 2 days using a dialysis membrane. The polymer after dialysis was distilled off the solvent under reduced pressure and dried under reduced pressure at 80 ° C. for 2 hours to obtain P1 (113 mg, dark brown powder) which is the polymer electrolyte of Example 3.

FIG. 12 shows the ¹ H-NMR spectrum of the obtained dark brown solid. Heavy water was used as the heavy solvent. Further, FIG. 13 shows an IR spectrum of the obtained dark brown solid.
(Synthesis of alternating copolymer)
[Example 4]
<Synthesis of Alternate Copolymer (P2) of Diphenylsulfone Compound>

In a 50 mL Schlenk tube, 5.14 g (7.38 mmol) of M1, 1.22 g (7.36 mmol) of 1,4-phenylenediboronic acid, and 3.12 g (22.6 mmol) of potassium carbonate were substituted with nitrogen. . Further, 80 mL of N, N-dimethylformamide, 50 mL of water, and 20.0 mg (0.0173 mmol) of tetrakis (triphenylphosphine) palladium (0) were added and stirred at 80 ° C. for 3 days. After the reaction, the solvent was distilled off, water was added again, and dialysis was performed using a cellophane tube. Thereafter, protonation (conversion of SO ₃ Na group to SO ₃ H group) was performed twice using an ion exchange resin (Amberlite IR-120, manufactured by Aldrich). After concentrating this solution and drying under reduced pressure, 3.35 g (yield 80%, brown solid) of P2 which is the polymer electrolyte of Example 4 was obtained. P2 was soluble in water.

FIG. 14 shows the ¹ H-NMR spectrum of the obtained brown solid. Heavy water was used as the heavy solvent. Moreover, IR spectrum of the obtained brown solid is shown in FIG.
20% by weight of p-xylylene glycol with respect to P2 was added to the obtained 10% by weight γ-butyrolactone solution of P2. The prepared solution was cast on a PET substrate and dried by heating. At this time, a dehydration reaction occurs between the —CH ₂ OH group of p-xylylene glycol and the C—H group in P2, and P2 is considered to be crosslinked by p-xylylene glycol. In fact, P2 became insoluble in water after this heat treatment. After this heat-drying, it was washed with 2M hydrochloric acid and pure water and again heat-dried to obtain a polymer electrolyte membrane having a thickness of 60 μm.

The measurement results of ion exchange capacity, proton conductivity, hot water swelling ratio, and tensile strength at break were as follows.
-Ion exchange capacity: 3.0 meq / g
Proton conductivity: 0.26 S / cm (80 ° C. relative humidity 95%)
-Hot water swelling rate: 40%
-Tensile strength at break: 13 MPa
(Synthesis of block copolymer)
[Example 5]
<Synthesis of diphenylsulfone compound block copolymer (P3)>

A 50 mL Schlenk tube was charged with 0.50 g (0.823 mmol) of M2, and dried under reduced pressure in an oil bath at 120 ° C. After drying, the Schlenk tube is replaced with nitrogen, and polyether sulfone (produced from bis (4-chlorophenyl) sulfone and bis (4-hydroxyphenyl) sulfone by a known method by using bis (4-chlorophenyl) sulfone in excess. Weight average molecular weight Mw = 5.3 × 10 ⁴ ) 200 mg, 2,2′-bipyridyl 359 mg (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., 0.63 g (2.29 mmol) of bis (1,5-cyclooctadiene) nickel (0) (Ni (cod) ₂ ) was added, and 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 dried under reduced pressure at 80 ° C. for 2 hours to obtain P3 (314 mg, brown solid) as the polymer electrolyte of Example 5.

  A 10% by weight dimethyl sulfoxide solution of the obtained polymer was cast on a PET substrate to form a film. After drying by heating, it was washed with 2M hydrochloric acid and pure water, and again dried by heating to obtain a polymer electrolyte membrane having a thickness of 30 μm.

The measurement results of ion exchange capacity, proton conductivity, hot water swelling ratio, and tensile strength at break were as follows.
・ Ion exchange capacity: 1.4 meq / g
Proton conductivity: 0.17 S / cm (80 ° C. relative humidity 95%)
-Hot water swelling rate: 20%
-Tensile strength at break: 59 MPa
[Example 6]
<Synthesis of diphenylsulfone compound block copolymer (P4: polymer obtained by separately synthesizing a polymer having the same structure as P3)>

A 200 mL Schlenk tube was charged with 3.97 g (6.53 mmol) of M2, and dried under reduced pressure in an oil bath at 120 ° C. After drying, the Schlenk tube is replaced with nitrogen, and polyether sulfone (produced from bis (4-chlorophenyl) sulfone and bis (4-hydroxyphenyl) sulfone by a known method by using bis (4-chlorophenyl) sulfone in excess. (Weight average molecular weight Mw = 5.3 × 10 ⁴ ) 1.59 g, 2.85 g (18.2 mmol) of 2,2′-bipyridyl and 32 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 5.0 g (18.2 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 recovered again by filtration, washed with water, and then dried under reduced pressure at 80 ° C. for 2 hours to obtain P4 (3.29 g, brown solid) as the polymer electrolyte of Example 6.

FIG. 16 shows the ¹ H-NMR spectrum of the obtained brown solid. Heavy dimethyl sulfoxide was used as the heavy solvent. Moreover, IR spectrum of the obtained brown solid P4 is shown in FIG.

  A 10% by weight dimethyl sulfoxide solution of the obtained polymer was cast on a PET substrate to form a film. After drying by heating, it was washed with 2M hydrochloric acid and pure water, and again dried by heating to obtain a polymer electrolyte membrane having a thickness of 30 μm.

The measurement results of ion exchange capacity and proton conductivity were as follows.
-Ion exchange capacity: 1.51 meq / g
Proton conductivity: 0.27 S / cm (80 ° C. relative humidity 95%)
(Production of fuel cell)
[Example 7]
<Creation of membrane electrode assembly>
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum-supported amount of 50% by mass and a 20% by mass polymer electrolyte dispersion solution (Nafion: registered trademark, manufactured by DuPont) are mixed in a solvent. The dispersion treatment was performed with a planetary ball mill (trade name: Pulverisette 7, manufactured by Fritsch). Ball mill pots and balls made of zirconia were used. The electrocatalyst ink was prepared by setting the composition ratio of the starting material to 2: 1 by mass ratio of the platinum-supported carbon particles and Nafion.

  The electrode catalyst layer ink was applied onto an ETFE (ethylene / tetrafluoroethylene copolymer) substrate and coated with an applicator. The coated electrode catalyst layer was produced by drying at 60 ° C. for 10 minutes.

The thickness of the electrode catalyst layer was adjusted so that the amount of platinum supported was about 0.3 mg / cm ^2, and the electrode area of the electrode catalyst layer was cut so as to be a square of 5 cm ² . A transfer sheet is placed so that the electrode catalyst layer cut into a square of 5 cm ² faces both surfaces of the electrolyte membrane obtained from the polymer P3 of Example 5, and the membrane is hot-pressed at 130 ° C. for 15 minutes. An electrode assembly was produced.
<Fabrication of fuel cell>
A standard cell made by a commercially available NF circuit design block was used. A fuel cell having an effective membrane area of 5 cm ² by disposing a carbon separator having gas passage grooves cut on both outer sides of the membrane electrode assembly, and further arranging a current collector and an end plate on the outer side and tightening them with bolts. The cell was assembled to obtain a fuel cell of Example 7.
<Evaluation of power generation performance of fuel cells>
The fuel cell of Example 7 was kept at 80 ° C., and humidified hydrogen was supplied to the anode and humidified air was supplied to the cathode. Humidification was performed by passing gas through a bubbler. The water temperature of the bubbler for hydrogen was 80 ° C, and the water temperature of the bubbler for air was 80 ° C. The hydrogen gas flow rate was 500 mL / min, and the air gas flow rate was 1000 mL / min. The voltage when the current density was 1.0 A / cm ² was measured and found to be 0.6V.

[Example 8]
<OCV durability test evaluation>
A fuel cell produced in the same manner as in Example 7 was kept at 100 ° C., and humidified oxygen was supplied to the anode instead of humidified hydrogen and humidified air to the cathode. Humidification was performed by passing a gas through a bubbler. The water temperature of the hydrogen bubbler was 65 ° C., and the water temperature of the oxygen bubbler was 65 ° C. The hydrogen gas flow rate was 200 mL / min, and the oxygen gas flow rate was 400 mL / min. The voltage value was monitored for a predetermined time in an open circuit state of the cell (OCV durability test). The fuel cell of Example 8 maintained 90% or more of the initial voltage value even after 140 hours. After the test, the cell was opened and the electrolyte membrane was observed, but no particularly noticeable signs of deterioration were observed.

[Comparative Example 1]
A fuel cell of Comparative Example 1 was produced in the same manner as in Example 7 using a commercially available Nafion 211 membrane instead of the electrolyte membrane in Example 5, and the OCV durability test was conducted in the same manner as in Example 8. In about 20 hours, the voltage value decreased to 50% or less. When the cell was opened after the test and the electrolyte membrane was observed, it deteriorated and a plurality of holes were formed.

  As described above, it was confirmed that the polymer electrolytes of Examples 4 and 5 had a hot water swelling rate of 40% or less. On the other hand, the hot water swelling rate of conventional aromatic hydrocarbon polymer electrolytes such as sulfonated polyetherketone and sulfonated polyethersulfone is estimated to be 50% or more. That is, it is suggested that the polymer electrolyte of this embodiment has suppressed swelling. As described above, this is because the ion exchange group and the benzene ring are separated by the linking group.

  Moreover, it was recognized that the tensile break strength becomes higher in Example 5 which is a block copolymer than in Example 4 which is an alternating copolymer. That is, it is suggested that the mechanical strength of the block copolymer is higher than that of the alternating copolymer. The tensile strength at break of the Nafion 211 film used in Comparative Example 1 was 25 MPa. Therefore, it is suggested that the polymer electrolyte of Example 5 has higher mechanical strength than Nafion.

  Moreover, it was recognized that the fuel cell of Example 7 has higher durability under high temperature and low humidity than the fuel cell of Comparative Example 1. That is, it is suggested that the polymer electrolyte of the present embodiment has higher durability under high temperature and low humidity than Nafion.

  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 flow path, 9a, 9b ... cooling water flow path, 10 ... solid polymer fuel cell.

Claims (8)

And Lube locked represented by the following general formula (3), a block copolymer comprising a main chain and a block not containing an ion exchange group, the block which does not contain the ion-exchange groups, represented by the following general formula (4) A polymer electrolyte characterized by being represented by:

In the 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 -, and, -NH- _{(CF 2) a} - selected from the group consisting of A linking group (a is an integer of 2 or more),
Y ₁ and Y _2, each independently, Ri Ah with atoms selected from the group consisting of alkali metal and a Group 2 element,
m is an integer of 2 or more .
In the general formula (4), Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ are each independently a divalent aromatic group,
B ₁ and B ₂ each independently represent a divalent linking group, or each independently represents a divalent aromatic group bonded directly without 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 ,
An ion exchange capacity is 0.5 meq / g or more and 4.0 meq / g or less. The polymer electrolyte according to claim 1 or 2 ,
A polymer electrolyte comprising a crosslinked structure in which a portion other than the protonic acid group of the polymer electrolyte is crosslinked with a crosslinking agent. A method for producing a polymer electrolyte, comprising:
By the diphenyl sulfone compound is polymerized in the presence of a metal complex represented by the following general formula (5-1), comprising a structure represented by the following general formula (5-2) as the polymer contained in the electrolyte in the main chain A method for producing a polymer electrolyte, comprising producing a polymer.

In the general formula (5-1) and the general formula (5-2), 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 -, and, -NH- (CF ₂ ) _a linking group selected from the group consisting of _a- (a is an integer of 2 or more),
X ₁ and X ₂ are each independently a halogen atom,
Y ₁ and Y _2, Ri Ah each independently alkali metal and the atomic selected from the group consisting of a Group 2 element,
m is an integer of 2 or more . The method for producing a polymer electrolyte according to claim 4 , wherein the metal complex is a nickel complex or a palladium complex. 6. The method for producing a polymer electrolyte according to claim 5 , wherein the metal complex is a nickel complex, and the nickel complex is a complex obtained from bis (cyclooctadiene) nickel (0) and 2,2′-bipyridyl. . An electrode catalyst layer;
A solid polymer electrolyte membrane bonded to the electrode catalyst layer;
A membrane electrode assembly comprising:
The said solid polymer electrolyte membrane contains the polymer electrolyte as described in any one of Claims 1-3 , The membrane electrode assembly characterized by the above-mentioned. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 7 .

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