JP2011181278A - Polymer electrolyte, its manufacturing method, and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polymer electrolyte capable of obtaining a polymer electrolyte membrane showing high proton conductivity even under a low-humidity condition. <P>SOLUTION: In the polymer electrolyte which is a block copolymer having a segment with a proton acid group and a segment without a proton acid group, the segment with the proton acid group includes a structure with the proton acid group coupling only with an aromatic ring having an electron donative group coupled, the segment without the proton acid group includes a structure containing the aromatic ring with only the electron donative group coupled as a substituent, and further, the segment with the proton acid group and the segment without the proton acid group are coupled together through a structure derived from a compound selected from a group consisting of decafluorobiphenyl and hexafluorobenzene. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a polymer electrolyte, a production method thereof, a solid polymer fuel cell using the polymer electrolyte, and a constituent material thereof.

Polymer electrolytes containing proton conductive substituents are used as raw materials for electrochemical devices such as fuel cells, humidity sensors, gas sensors, and electrochromic display devices. Among these, fuel cells are expected as one of the pillars of new energy technology. Solid polymer fuel cells that use polymer electrolytes with proton-conducting substituents can be operated at low temperatures and can be reduced in size, weight, mobile vehicles such as automobiles, household cogeneration systems, and civilian use. Application to small portable devices is under consideration. For example, a direct methanol fuel cell that uses methanol directly as a fuel has features such as a simple structure, ease of fuel supply and maintenance, and high energy density. It is expected to be applied to civilian small portable devices such as personal computers. A polymer electrolyte fuel cell (PEFC) is suitable as an electric vehicle or a household power source.

These PEFCs and DMFCs are usually operated at a temperature of 80 ° C. or lower. However, in order to improve performance, the PEFC and DMFC can be operated at 120 ° C. or higher and in a low humidified condition from the viewpoint of catalytic activity, catalyst poisoning, and waste heat utilization. It has been demanded. Therefore, electrolytes used for PEFC and DMFC are required to maintain membrane strength even at high temperatures and to exhibit high proton conductivity even under low humidification conditions. However, the currently mainstream fluorine-based electrolyte membranes (membranes such as Nafion, Aciplex, and Flemion, which are perfluoroalkyl sulfonic acid polymers) have decreased membrane strength at 100 ° C or higher, and proton conduction under low humidification conditions. The degree decreases significantly. Further, the large permeation of fuel and oxidant gas and the high cost are major causes that hinder high performance and low cost of PEFC and DMFC.

In order to solve such a problem, an electrolyte using an aromatic compound has been studied. For example, Patent Document 1 discloses a sulfonic acid group-containing aromatic as a block copolymer type polymer electrolyte having a hydrophilic part having a decafluorobiphenyl group at a terminal and a hydrophobic part having a part that reacts with decafluorobiphenyl. Polyarylene ether compounds are described. This block copolymer exhibits high conductivity and low swelling rate in water, but its production requires introduction of sulfonic acid groups in monomer units, which requires a long number of steps and is complicated in cost. Patent Document 2 describes a sulfonic acid group-containing aromatic polyarylene ether compound. Although this random copolymer is excellent in ionic conductivity under high-temperature industrial humidification conditions, it has a problem of low proton conductivity under low humidification conditions.

JP 2009-104926 A Japanese Patent Laid-Open No. 2003-147074

An object of the present invention has been made in view of the above problems, and is to provide a polymer electrolyte from which a polymer electrolyte membrane exhibiting high proton conductivity even under low humidification conditions can be obtained.

As a result of intensive studies to solve the above problems, the present inventors have found that a hydrophilic segment having a structure in which a protonic acid group is bonded only to an aromatic ring to which an electron donating group is bonded, and a substituent A block copolymer polyelectrolyte in which a hydrophobic segment having a structure containing an aromatic ring to which only an electron-donating group is bonded is bonded via a structure derived from decafluorobiphenyl or hexafluorobenzene By using it as an electrolyte for a fuel cell, it has been found that it has a high ion exchange capacity portion advantageous for conductivity, particularly conductivity in a low water content state, and exhibits excellent proton conductivity, and has led to the completion of the present invention. It was.

That is, the present invention is a block copolymer having a segment having a proton acid group and a segment not having a proton acid group, and the segment having a proton acid group has an electron donating group bonded thereto. The segment having a protonic acid group bonded only to an aromatic ring, and the segment having no protonic acid group has a structure including an aromatic ring having only an electron-donating group bonded as a substituent, A polymer comprising a segment having a protonic acid group and a segment having no protonic acid group bonded via a structure derived from a compound selected from the group consisting of decafluorobiphenyl and hexafluorobenzene It relates to the electrolyte.

In the polymer electrolyte of the present invention, the segment having no proton acid group has an aromatic ring to which only an electron donating group is bonded as a substituent, -S-, -O-, -Ar-, and It is preferably bonded to at least one selected from the group consisting of groups represented by formula (4).

(In the formula, each R ² is independently an alkyl group having 1 to 20 carbon atoms, and when there are a plurality thereof, they may be the same or different. R ³ is an alkylene group having 1 to 10 carbon atoms. .)

In the polymer electrolyte of the present invention, the segment having a proton acid group has a sulfonic acid group of 1.0 to 10.0 meq. / G is preferable.

The present invention also provides block copolymerization of a segment precursor having a proton acid group and a segment precursor having no proton acid group, having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene. The present invention relates to a method for producing a polymer electrolyte.

The method for producing a polymer electrolyte of the present invention has a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene, and the segment having a proton acid group is derived from a compound selected from the decafluorobiphenyl and hexafluorobenzene It is preferably obtained by protonating an oligomer having a terminal group.

The present invention also relates to a polymer electrolyte for fuel cells using the polymer electrolyte of the present invention.

The present invention also relates to a fuel cell catalyst layer using the polymer electrolyte of the present invention.

The present invention also relates to a fuel cell membrane / electrode assembly using the polymer electrolyte of the present invention.

According to the polymer electrolyte of the present invention, it is possible to provide a polymer electrolyte membrane exhibiting excellent proton conductivity particularly in a situation where moisture is low.

An embodiment of the present invention will be described as follows. It should be noted that the present invention is not limited to the following description.

(1. Polymer electrolyte of the present invention)
The polymer electrolyte of the present invention is a block copolymer having a segment having a proton acid group and a segment not having a proton acid group, and the segment having a proton acid group has an electron donating group bonded thereto. The segment having no proton acid group has a structure containing an aromatic ring to which only an electron donating group is bonded as a substituent. The segment having a protonic acid group and the segment having no protonic acid group are bonded via a structure derived from a compound selected from the group consisting of decafluorobiphenyl and hexafluorobenzene. As a result, a polymer electrolyte membrane that exhibits high proton conductivity even under low humidity conditions can be obtained.

The segment having a proton acid group in the polymer electrolyte of the present invention will be described in more detail. In the polymer electrolyte of the present invention, the segment having a proton acid group has a structure in which a proton acid group is bonded only to an aromatic ring to which an electron donating group is bonded. With such a configuration, since the sulfonation is easy, an electrolyte can be obtained with few steps. An aromatic ring to which an electron donating group is bonded has an electron density on the aromatic ring improved by having an electron donating group as a substituent compared to an aromatic ring having only a hydrogen atom as a substituent. Is. Here, the electron donating group may be any substituent that improves the electron density of the bonded aromatic ring, and is not particularly limited, but —O—, —S—, and —Ar— are bonded. It is preferable from the viewpoint of easy proton oxidation. From the viewpoint of high electron density and easy sulfonation, for example, a structure of the following formula (1) is preferable.

(In the formula, X and X ′ are a direct bond, a linking group selected from —O— and —S— or a hydrogen atom, and when there are a plurality of them, they may be the same or different. M is 1. Represents an integer of from 10 to 10. Ar represents an aromatic ring selected from the structural group of the following formula (2).

The segment having a proton acid group in the polymer electrolyte of the present invention may further have the following structure in addition to the aromatic ring to which the electron donating group is bonded.

The segment having a proton acid group in the polymer electrolyte of the present invention has a structure in which a proton acid group is bonded only to an aromatic ring to which an electron donating group is bonded. The proton acid group is a group capable of dissociating protons, and thereby exhibits proton conductivity. Specific examples include sulfonic acid, carboxylic acid, phosphoric acid, and boronic acid.

In the polymer electrolyte of the present invention, the segment having a proton acid group contains 1.0 to 10.0 meq. / G, preferably 1.5 to 8.0 meq. / G is more preferable. 1.0 meq. / G, proton conductivity may be insufficient, and 10.0 meq. If it exceeds / g, swelling may become severe. In addition, content of a protonic acid group here can be measured by the method similar to the measurement of the ion exchange capacity of the protonic acid group containing segment precursor in the below-mentioned Example.

The segment having no proton acid group in the polymer electrolyte of the present invention has a structure including an aromatic ring to which only an electron donating group is bonded as a substituent. By setting it as such a structure, when it is set as a block copolymer, it can become an electrolyte which shows low gas permeability. From the viewpoint of ease of blocking, it contains an aromatic ring to which at least one substituent selected from the group consisting of —S—, —O—, —Ar— and a group represented by the following formula (4) is bonded. It is preferable.

(In the formula, each R ² is independently an alkyl group having 1 to 20 carbon atoms, and when there are a plurality thereof, they may be the same or different. R ³ is an alkylene group having 1 to 10 carbon atoms. .)

For example, the structure of following formula (3) is mentioned.

(In the formula, Z is a direct bond, —O—, —S—, a linking group selected from the group represented by the above formula (4), and when there are a plurality of them, they may be the same or different from each other. R ¹ is independently a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a substituted aryl group having 6 to 20 carbon atoms, and when there are a plurality of R ^{1 s} , they are the same as each other. Or different.)

The formula (3) in the polymer electrolyte of the present invention will be described in more detail. In the formula (3), each Z is a direct bond, —O—, —S—, or a linking group selected from the group represented by the formula (4). May be. R ¹ is independently a hydrogen atom, an alkyl group, an aryl group, or a substituted aryl group, and when there are a plurality of R ^{1 s} , they may be the same or different. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. As the aryl group and substituted aryl group, a phenyl group, a naphthyl group, a 4-phenylphenyl group, a 4-phenoxyphenyl group, and the like can be listed. Is preferred.

The formula (4) in the polymer electrolyte of the present invention will be described in more detail. In Formula (4), R ^{2 s} are each independently an alkyl group having 1 to 20 carbon atoms, and when there are a plurality of R ^{2 s} , they may be the same or different from each other. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group, and an alkyl group having 1 to 3 carbon atoms is preferable from the viewpoint of easy protection and deprotection. R ³ is an alkylene group having 1 to 10 carbon atoms. Specifically, —CH ₂ CH ₂ —, —CH (CH ₃ ) CH ₂ —, —CH (CH ₃ ) CH (CH ₃ ) —, —C (CH ₃ ) ₂ CH ₂ —, —C (CH ₃ ) ₂ CH (CH ₃ ) —, —CH ₂ CH ₂ CH ₂ —, —CH ₂ C (CH ₃ ) ₂ CH ₂ — and the like can be listed.

In the polymer electrolyte of the present invention, the segment having no proton acid group has the following structure in addition to the structure containing an aromatic ring to which only an electron donating group is bonded as the substituent. You may do it.

The polymer electrolyte of the present invention comprises a segment having a protonic acid group and a segment having no protonic acid group bonded via a structure derived from a compound selected from the group consisting of decafluorobiphenyl and hexafluorobenzene. It is a block copolymer. Decafluorobiphenyl and hexafluorobenzene are polyfunctional compounds, and therefore can take the form of a block copolymer having a branched structure as well as a linear block copolymer.

The number average molecular weight of the block copolymer of the present invention is preferably 10,000 to 500,000, more preferably 20,000 to 200,000. If it is less than 10,000, the strength of the film may be insufficient. On the other hand, if it is more than 500,000, the solubility may be lowered and the handling property may be deteriorated.

In the block copolymer of the present invention, each segment preferably has a repeating unit. More specifically, the structure of each segment described above is preferably included as a structure of a repeating unit in each segment. When the segment has a repeating unit, a phase separation structure is easily formed when block copolymerization is performed, and high proton conductivity can be exhibited even under low humidification conditions.

In the block copolymer of the present invention, when the number of repeating units in the segment having a proton acid group is 1, the number of repeating units in the segment having no proton acid group is preferably 1 to 100, more preferably 1 ~ 30. If it is smaller than this, excellent proton conductivity may not be exhibited, and if it is larger than this, the strength of the membrane may be insufficient.
The polymer electrolyte of the present invention has a sulfonic acid group of 0.5 to 3.0 meq. / G is preferably included, and 1.0 to 2.5 meq. / G is more preferable. 0.5 meq. If it is smaller than / g, proton conductivity tends to be insufficient, while 3.0 meq. When it exceeds / g, when it is set as a film | membrane, there exists a tendency for it to become difficult to maintain intensity | strength. Here, the amount of the sulfonic acid group is determined by the ion exchange capacity measurement method described in Examples described later.

(2. Method for producing polymer electrolyte of the present invention)
Next, an example is given and demonstrated about the manufacturing method which concerns on the polymer electrolyte of this invention. In addition, the manufacturing method of the polymer electrolyte of this invention is not limited to the following.

There is no particular limitation on the method of chemically bonding two or more segment precursors to increase the molecular weight, and the method can be appropriately determined depending on the reactivity of the monomer to be polymerized. For the details of the polymerization method, a general method (“Synthesis and Reaction of Polymer (2)”, p.

In order to obtain the polymer electrolyte of the present invention, a segment precursor having a proton acid group having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene, and a segment precursor not having a proton acid group are obtained. A method of condensation (block copolymerization) is preferred. A block copolymer having a straight chain structure and a block copolymer having a branched structure can be made separately by changing the charged composition of a segment having a proton acid group and a segment having no proton acid group. .

In the method for producing a polymer electrolyte of the present invention, an oligomer having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene is protonated to form a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene. It is preferable to include a step of producing a segment having a proton acid group. By making such a production method, not only can the proton acid group introduction step at the monomer stage and the subsequent purification step be omitted, but also a variety of structures can be selected for the segment having no proton acid group. It is preferable because the preparation of the corresponding electrolyte is easy.

The method for introducing a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene of the present invention and the blocking reaction of an oligomer having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene include Although a typical condensation method can be applied, it is preferable to produce in a temperature range of 70 ° C. to 130 ° C. in consideration of high reactivity. When the temperature is lower than 70 ° C, the reaction may not proceed sufficiently. When the temperature is higher than 130 ° C, side reactions such as crosslinking may occur.

Each segment precursor is obtained by condensing a monomer having a nucleophilic substituent such as a hydroxyl group at the terminal with a monomer having a leaving group such as a halogen compound at the terminal, or in a monomer having a leaving group. Examples include a method of adding a catalyst and condensing. When the polyelectrolyte is obtained by a condensation reaction, compounds having a hydroxyl group remaining at the terminal can be bonded to each other, and can be condensed in the same manner by adding a dihalogen compound such as 4,4'-dichlorodiphenylsulfone. On the other hand, when compounds having leaving groups such as halogen groups remaining at the ends are bonded together, condensation is similarly performed by adding a compound having a nucleophilic substituent at the end such as 4,4′-dihydroxydiphenylsulfone. It can also be made. Note that an oligomer having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene before the terminal group is introduced may be produced by the same method.

In the case where the segment having no proton acid group contains a group represented by the above formula (4), a general method for a compound having a —CO— group (“Protective Groups in Organic Synthesis (Third Edition)” p. 293-347, WILEY-INTERSCIENCE) can be obtained by polymerizing, and can be returned to -CO- by deprotection after the polymerization reaction.

Specific examples of the monomer that can be used in the present invention include the following monomers.

When manufacturing the segment which has a repeating unit in this invention, the following monomers are mentioned as a monomer which can be used, for example.

The condensation reaction can be performed in a molten state without using a solvent, but it is preferably performed in a suitable solvent. Examples of the solvent include aromatic hydrocarbon solvents, halogen solvents, ether solvents, ketone solvents, amide solvents, sulfone solvents, sulfoxide solvents, and the like. Among them, N, N-dimethylacetamide, N, A mixed system of an amide solvent such as N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone and a halogen solvent such as dichlorobenzene or trichlorobenzene is preferable. Moreover, these may be used independently or may use 2 or more types together.

What is necessary is just to set the reaction temperature of a polymerization reaction process suitably according to a polymerization reaction. Specifically, it may be set to the optimum use range of 20 ° C to 250 ° C, more preferably 40 ° C to 200 ° C. If the temperature is lower than this range, the reaction is slow, and if the temperature is high, the main chain may be broken.

The protonic acid groups in the polymerization step may be acid type or salt type, and may be the same or different from each other. Specifically, the monovalent cation may be a hydrogen atom, a metal cation, or an ammonium cation. In the case of a metal cation, examples thereof include sodium and potassium. In the case of an ammonium cation, a quaternary ammonium salt may be used, and the substituent on N is a hydrogen atom, an alkyl group, an aryl group having 6 to 30 carbon atoms, or a substituted aryl group. Or different. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. Examples of the aryl group and substituted aryl group include a phenyl group, a naphthyl group, a 4-phenylphenyl group, a 4-phenoxyphenyl group, and a pentafluorophenyl group.

Examples of protonic acid groups include sulfonic acid groups, which can be synthesized by reacting a compound that introduces sulfonic acid groups with a sulfonating agent. As the sulfonating agent, chlorosulfonic acid, sulfuric anhydride, fuming sulfuric acid, sulfuric acid, acetyl sulfuric acid and the like can be used.

Examples of the sulfonating agent in the sulfonation step include sulfuric acid, chlorosulfonic acid, fuming sulfuric acid, and the like. Among them, chlorosulfonic acid is preferable because it has an appropriate reactivity.

The solvent used in the sulfonation reaction may be inert to the sulfonating agent, and examples thereof include hydrocarbon solvents and halogenated hydrocarbons. The hydrocarbon solvent is preferably a saturated aliphatic hydrocarbon, particularly a branched or straight chain hydrocarbon having 5 to 15 carbon atoms, and pentane, hexane, heptane, octane or decane is preferred from the viewpoint of solubility. Examples of halogenated hydrocarbons include halogenated saturated aliphatic hydrocarbons or halogenated aromatic hydrocarbons, such as monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, dichloroethane, trichloroethane, tetrachloroethane, and the like. Among them, dichloromethane is preferable because of easy handling.

What is necessary is just to set the reaction temperature of a sulfonation process suitably according to reaction, Specifically, what is necessary is just to set to -80 to 200 degreeC which is the optimal use range of a sulfonating agent, More preferably, it is -50 to 120 degreeC. ° C, more preferably -20 ° C to 80 ° C. If the temperature is lower than this range, the reaction is slow, and if the temperature is high, a rapid reaction occurs and the intended sulfonation does not proceed to 100%.

The reaction time of the sulfonation step can be appropriately selected depending on the structure of the polymer to be sulfonated, but it may usually be in the range of about 1 minute to 20 hours. If it is shorter than 1 minute, uniform sulfonation may not proceed, and if it is longer than 20 hours, side reaction may occur.

The addition amount of the sulfonating agent in the sulfonation step is preferably 1 equivalent to 50 equivalents when the total amount of the sulfonation sites contained in the polymer compound to be sulfonated is 1. If it is lower than 1 equivalent, the site to be sulfonated may become non-uniform, while if it exceeds 50 equivalent, the main chain of the polymer compound may be cleaved.

The concentration of the presulfonated compound in the sulfonation step is not particularly limited as long as the reaction proceeds uniformly when brought into contact with the sulfonating agent, but the compound does not cause side reactions such as low molecular weight and the amount of solvent is suppressed. From the viewpoint of cost advantage, it is preferably 1 to 30% by weight.

(3. Fuel cell electrolyte membrane of the present invention)
The electrolyte membrane for fuel cells of the present invention is obtained by processing the above-described polymer electrolyte of the present invention into a membrane shape (film shape). By using the polymer electrolyte of the present invention, excellent power generation characteristics suitable for an electrolyte membrane of a solid polymer fuel cell or a direct methanol fuel cell can be exhibited.

The film thickness may be appropriately set in consideration of mechanical strength, handling properties, fuel and oxidant blocking properties, and membrane resistance. Specifically, 5 to 200 μm is preferable, and 20 to 100 μm is more preferable. If it is thinner than this range, the membrane resistance will be small, but the mechanical strength may be insufficient, the handleability may be impaired, and the permeation amount of fuel and oxidant may be excessive. On the other hand, if it is thicker than this range, the membrane resistance increases, and there is a possibility that desired performance as an electrolyte membrane will not be exhibited.

As a film forming method, a known method used in a polymer film or an electrolyte membrane can be applied. Specifically, a solution cast method can be used in the case of solvent solubility, and a melt extrusion method or a hot press process can be used in the case of thermoplasticity, but is not limited thereto. In addition, the fuel cell electrolyte of the present invention can be combined with other binder resin or electrolyte and processed into a form in which it is dispersed in other matrix components as it is.

(4. Catalyst layer for fuel cell of the present invention)
The fuel cell catalyst layer of the present invention is composed of the above-described polymer electrolyte of the present invention, a fuel cell catalyst, and, if necessary, a water repellent and a binder resin. By using the polymer electrolyte of the present invention, excellent power generation characteristics suitable for an anode or cathode catalyst layer of a solid polymer fuel cell or a direct methanol fuel cell can be exhibited. The fuel cell catalyst used in the present invention may be literally a fuel cell catalyst conventionally known to those skilled in the art, and includes a conductive catalyst carrier and a catalytically active substance supported by the conductive catalyst carrier. Any other specific configuration is not particularly limited. Specifically, a catalyst active for the electrode reaction of the fuel cell is used. On the anode side, a catalyst having the ability to oxidize fuel (such as methanol or hydrogen) is used. Specific examples of the conductive catalyst support include carbon supports having a high surface area such as carbon black, ketjen black, activated carbon, carbon nanohorn, and carbon nanotube. The catalyst support ability, electronic conductivity, and electrochemical stability can be exemplified. Therefore, these materials are preferable. Specific examples of the catalytically active substance include platinum, cobalt, ruthenium, and the like, and these may be used alone or as an alloy containing at least one of them, or any mixture. In particular, considering the oxidizing ability of the fuel, the reducing ability of the oxidizing agent, and durability, platinum or an alloy containing platinum is preferable. If necessary, these may be composed of three or more components using iron, tin, rare earth elements or the like for stabilization and long life.

The fuel cell catalyst layer of the present invention is prepared by applying a catalyst ink containing the fuel cell electrolyte of the present invention, the fuel cell catalyst, and a solvent onto a support and removing the solvent. The solvent can be used without any limitation as long as it can dissolve the fuel cell electrolyte and does not poison the fuel cell catalyst. The catalyst ink may contain additives such as a non-electrolyte binder, a water repellent, a dispersant, a thickener, and a pore-forming agent as necessary. In addition, those additives conventionally known to those skilled in the art can be used, and other specific configurations are not particularly limited.

The catalyst ink prepared by the above composition and method can be applied by the following coating method depending on the viscosity and the type of substrate. The method for applying the catalyst ink onto the substrate may be any method known to those skilled in the art, and the other specific configuration is not particularly limited. For example, methods using a knife coater, a bar coater, a spray, a dip coater, a spin coater, a roll coater, a die coater, a curtain coater, screen printing, and the like can be enumerated, but not limited thereto.

In the present invention, when a polymer film is used as the substrate, a fuel cell catalyst layer transfer sheet can be produced, and when a conductive porous sheet is used, a fuel cell gas diffusion electrode can be produced.

(5. Membrane / electrode assembly for fuel cell of the present invention)
The membrane / electrode assembly for a fuel cell of the present invention includes any of the polymer electrolyte of the present invention, the polymer electrolyte membrane for a fuel cell, or the catalyst layer for a fuel cell described above. That is, the polymer electrolyte, the fuel cell electrolyte membrane, and the fuel cell catalyst layer of the present invention are used as at least one of the electrolyte membrane, anode catalyst layer, and cathode catalyst layer, which are constituents of the membrane / electrode assembly. Other specific configurations are not particularly limited. Therefore, in the fuel cell membrane / electrode assembly of the present invention, as the electrolyte membrane, in addition to the fuel cell electrolyte membrane of the present invention, for example, as a perfluorocarbon sulfonic acid polymer electrolyte membrane, manufactured by DuPont Nafion, Flemion manufactured by Asahi Glass Co., Ltd., Aciplex manufactured by Asahi Kasei Co., Ltd., Gore Select manufactured by Gore, etc. may be used. As the non-fluorine polymer electrolyte membrane, those conventionally known to those skilled in the art can be used. For example, as a polymer electrolyte membrane suitable for a membrane electrode assembly for direct methanol fuel cells, a pore filling membrane in which a nonelectrolytic porous support is filled with a polymer electrolyte or a polymer electrolyte and a nonelectrolyte are combined. It is preferable to use a composite electrolyte membrane or the like.

In the production of the membrane / electrode assembly for a fuel cell of the present invention, the conditions for heating and pressure welding are literally those conventionally known to those skilled in the art, and the other specific configurations are not particularly limited. The optimum conditions need to be set as appropriate according to the type of polymer electrolyte contained in each of the electrolyte membrane, the anode side catalyst layer, and the cathode side catalyst layer. Generally, the temperature of the heating and pressure welding is equal to or lower than the thermal deterioration or thermal decomposition temperature of the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer, and the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer. It is preferable to carry out the reaction at a temperature above the glass transition point or softening point of the polymer electrolyte, or at a temperature above the glass transition point or softening point of the polymer electrolyte contained in the polymer electrolyte membrane or the catalyst layer. In addition, the pressurizing condition of the heat pressure contact is generally in the range of 0.1 MPa or more and 20 MPa or less, and the polymer electrolyte membrane and the catalyst layer are in sufficient contact with each other, and there is no deterioration in characteristics due to significant deformation of the material used. preferable.

In the membrane / electrode assembly for a fuel cell of the present invention, the fuel cell catalyst layer obtained by the production method of the present invention is disposed on both sides of the polymer electrolyte membrane, and the polymer electrolyte membrane and the fuel cell catalyst are arranged. After the layers are joined, the polymer film is peeled off to form a three-layer membrane / electrode assembly comprising a polymer electrolyte membrane, an anode-side catalyst layer, and a cathode-side catalyst layer (3-layer MEA: Membrane Electrode Assembly, CCM: Catalyst Coating Membrane) can be manufactured.

Further, when a gas diffusion electrode for a fuel cell obtained by the production method of the present invention is used instead of the catalyst layer for a fuel cell, five layers in which a diffusion layer is formed outside the three-layer membrane / electrode assembly A membrane / electrode assembly (5-layer MEA) can be manufactured.

Furthermore, at least a layer made of a water repellent conductive material composed of conductive carbon particles and a water repellent agent is provided between the diffusion layer and the catalyst layer as needed, and the electrolyte at the periphery of the diffusion layer It is added that a seven-layer membrane electrode assembly formed by arranging a pair of gaskets on the membrane is also within the scope of the present invention.

The polymer electrolyte, the polymer electrolyte membrane for fuel cells, or the catalyst layer for fuel cells of the present invention is suitable for solid polymer fuel cells and / or direct methanol fuel cells. In the polymer electrolyte fuel cell and / or the direct methanol fuel cell, the membrane / electrode assembly described above is inserted between a pair of separators in which a flow path for feeding fuel and an oxidant is formed, and the like. It is obtained. The separator is not particularly limited, and for example, a conductive material such as carbon graphite or stainless steel can be used. In particular, when a metal material such as stainless steel is used, it is preferable to perform a corrosion resistance treatment. Instead of these separators, members having fuel and oxidant supply paths may be substituted.

When supplying hydrogen or hydrogen-rich gas as a fuel to the anode, it is classified into a solid polymer fuel cell, and when supplying methanol and its aqueous solution, it is classified directly into a methanol fuel cell. In either case, the oxidizing agent for the cathode is not particularly limited, but oxygen or air can be used. The oxidant supplied to the cathode may be humidified with water, but the use of a non-humidified oxidant is preferable because the cathode flooding phenomenon can be suppressed.

It should be noted that the polymer electrolyte fuel cells according to the present embodiment can be used alone or in a stacked manner to form a stack, or a fuel cell system incorporating them.

Hereinafter, examples will be shown and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

The ion exchange capacity of the proton acid group-containing segment precursor obtained in Synthesis Example 1 and the number average molecular weight of the polymer electrolytes (block copolymers) obtained in Examples and Comparative Examples were measured by the following methods.

<Method of measuring ion exchange capacity of proton acid group-containing segment precursor>
The obtained proton acid group-containing segment precursor (about 100 mg: sufficiently dried) was immersed in 20 mL of a saturated aqueous solution of sodium chloride at 25 ° C., and subjected to an ion exchange reaction in a water bath at 60 ° C. for 3 hours. The mixture was cooled to 25 ° C. and then thoroughly washed with ion exchange water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this recovered solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate the ion exchange capacity.

<Measurement of number average molecular weight of polymer electrolyte>
The polymer electrolyte was measured by the GPC method, and the number average molecular weight was calculated from the converted value using a standard polystyrene sample.

(Synthesis Example 1: Protic acid group-containing segment precursor)
Bis (4-fluorophenyl) sulfone (2.7 g, 10.5 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) and 9,9 in a three-necked flask equipped with a Liebig condenser, Dean stack trap and mechanical stirrer and purged with nitrogen '-Bis (4-hydroxyphenyl) fluorene (4.0 g, 11.4 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), potassium carbonate (3.2 g, 22.8 mmol, manufactured by Kanto Chemical Co., Inc.) was added, and dehydrated N, N -A mixed solution of dimethylacetamide (DMAc, 20 mL, manufactured by Kanto Chemical Co., Inc.) and dehydrated toluene (10 mL, manufactured by Kanto Chemical Co., Inc.) was stirred for 3 hours under an oil bath heating condition of 140 ° C, and then further 165 ° C. For 2 hours. 9,9′-bis (4-hydroxyphenyl) fluorene (0.4 g, 1.14 mmol) was added thereto, and the mixture was stirred at the same temperature for 1 hour. The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and vacuum dried at 60 ° C. to obtain 6.1 g of the target hydrophilic part oligomer as a white solid.
Next, in a three-necked flask equipped with a Liebig condenser and a magnetic stirrer and purged with nitrogen, the obtained oligomer for hydrophilic part (3 g, 1.15 mmol) and decafluorobiphenyl (1.9 g, 5.75 mmol) , Potassium carbonate (0.32 g, 2.3 mmol) was added. Dehydrated DMAc (30 ml) and dehydrated cyclohexane (5 ml) were added thereto, and the mixed solution was stirred for 12 hours under oil bath heating conditions at 100 ° C. After completion of the reaction, the reaction solution was dropped into pure water, and a white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and dried at 60 ° C. under vacuum to obtain 4.7 g of an oligomer having a terminal group derived from decafluorobiphenyl (ligating agent-containing oligomer) as a white solid. Obtained.
Finally, the obtained ligating agent-containing oligomer (4.7 g) was dissolved in dichloromethane (100 ml) and added dropwise to a dichloromethane (150 ml) solution containing chlorosulfuric acid (1.9 ml, 28 mmol) at room temperature and stirred for 12 hours. did. After completion of the reaction, the reaction mixture was dropped into cold pure water, and then dichloromethane was distilled off under reduced pressure. NaCl was added to the mixed solution, and the resulting solid was collected by filtration. This solid is dissolved again in pure water, an aqueous NaOH solution is added until the pH of the solution becomes neutral, NaCl is added when neutral and stable, the resulting solid is collected by filtration, and then dissolved again in pure water. Dialysis was performed using a dialysis membrane. The dialyzed solution was concentrated, and the resulting white precipitate was vacuum-dried at 120 ° C. for 10 hours to obtain 5.5 g of the target proton acid group-containing segment precursor. In addition, when content of the sulfonic acid group of this proton acid group containing segment precursor was measured, it was 4.3 meq. / G.

(Synthesis Example 2: Segment precursor having no proton acid group)
Bis (4-fluorophenyl) sulfone (4.8 g, 18.8 mmol) and 4,4′-biphenol (5. 4) in a three-necked flask equipped with a Liebig condenser, Dean stack trap, mechanical stirrer and purged with nitrogen. 1 g, 20 mmol), potassium carbonate (5.5 g, 40 mmol), dehydrated DMAc (40 ml) and dehydrated toluene (20 ml) were added. This solution was stirred for 3 hours under an oil bath heating condition of 140 ° C., and further stirred at 165 ° C. for 2 hours. To this was added 4,4′-biphenol (0.37 g, 2 mmol), and the mixture was stirred at the same temperature for 1 hour. The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and vacuum dried at 60 ° C. to obtain 9.1 g of a segment precursor having no target proton acid group as a white solid.

(Synthesis Example 3: Segment precursor having no proton acid group)
Bis (4-fluorophenyl) sulfone (4.9 g, 19.4 mmol) and 4,4′-biphenol (5. 4) in a three-necked flask equipped with a Liebig condenser, Dean stack trap, mechanical stirrer and purged with nitrogen. 1 g, 20 mmol), potassium carbonate (5.5 g, 40 mmol), dehydrated DMAc (40 ml) and dehydrated toluene (20 ml) were added. This solution was stirred for 3 hours under an oil bath heating condition of 140 ° C., and further stirred at 165 ° C. for 2 hours. To this was added 4,4′-biphenol (0.37 g, 2 mmol), and the mixture was stirred at the same temperature for 1 hour. The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and vacuum dried at 60 ° C. to obtain 9.2 g of a segment precursor having no proton acid group as a target product as a white solid.

(Synthesis Example 4: Segment precursor having no proton acid group)
Bis (4-fluorophenyl) sulfone (4.8 g, 18.8 mmol) and 2,7-dihydroxynaphthalene (3. 3) in a three-necked flask equipped with a Liebig condenser, Dean stack trap, mechanical stirrer and purged with nitrogen. 2 g, 20 mmol), potassium carbonate (5.5 g, 40 mmol), dehydrated DMAc (40 ml) and dehydrated toluene (20 ml) were added. This solution was stirred for 3 hours under an oil bath heating condition of 140 ° C., and further stirred at 165 ° C. for 2 hours. 2,7-dihydroxynaphthalene (0.3 g, 2 mmol) was added thereto, and the mixture was stirred at the same temperature for 1 hour. The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and vacuum dried at 60 ° C. to obtain 7.0 g of a segment precursor having no proton acid group as a target product as a white solid.

(Synthesis Example 5: Segment precursor having no proton acid group)
Bis (4-fluorophenyl) sulfone (4.8 g, 18.8 mmol) and hydroquinone (2.2 g, 20 mmol) in a three-neck flask equipped with a Liebig condenser, Dean stack trap, mechanical stirrer and purged with nitrogen, Potassium carbonate (5.5 g, 40 mmol), dehydrated DMAc (40 ml) and dehydrated toluene (20 ml) were added. This solution was stirred for 3 hours under an oil bath heating condition of 140 ° C., and further stirred at 165 ° C. for 2 hours. Hydroquinone (0.2 g, 2 mmol) was added thereto and stirred at the same temperature for 1 hour. The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and methanol, and then collected again by filtration and vacuum dried at 60 ° C. to obtain 6.5 g of a segment precursor having no proton acid group as a target product as a white solid.

Example 1
<Preparation of block copolymer>
Protic acid group-containing segment precursor obtained in Synthesis Example 1 (0.403 g), segment precursor not having a proton acid group obtained in Synthesis Example 2 (0.44 g), potassium carbonate (33 mg, 0.24 mmol), And dehydrated DMAc (5 ml) and cyclohexane (1.5 ml) were added to a container charged with calcium carbonate (237 mg, 2.4 mmol). After this solution was heated at 140 ° C. for 24 hours, the reaction solution was dropped into an aqueous hydrochloric acid solution, and the resulting precipitate was collected by filtration. The solid was treated several times with an aqueous NaCl solution and then dried in a constant temperature bath at 60 ° C. to obtain a block copolymer. (Yield: 0.78 g, number average molecular weight: 95000)

(Example 2)
<Preparation of block copolymer>
Protic acid group-containing segment precursor obtained in Synthesis Example 1 (0.33 g), segment precursor having no proton acid group obtained in Synthesis Example 3 (0.6 g), potassium carbonate (27 mg, 0.2 mmol), And dehydrated DMAc (5 ml) and cyclohexane (1.5 ml) were added to a container charged with calcium carbonate (196 mg, 2.0 mmol). After this solution was heated at 140 ° C. for 24 hours, the reaction solution was dropped into an aqueous hydrochloric acid solution, and the resulting precipitate was collected by filtration. The solid was treated several times with an aqueous NaCl solution and then dried in a constant temperature bath at 60 ° C. to obtain a block copolymer. (Yield: 0.84 g, number average molecular weight: 104000)

(Example 3)
<Preparation of block copolymer>
The proton acid group-containing segment precursor obtained in Synthesis Example 1 (0.4 g), the segment precursor having no proton acid group obtained in Synthesis Example 4 (0.58 g), potassium carbonate (28 mg, 0.2 mmol), And dehydrated DMAc (5 ml) and cyclohexane (1.5 ml) were added to a container charged with calcium carbonate (0.2 g, 2 mmol). After this solution was heated at 140 ° C. for 24 hours, the reaction solution was dropped into an aqueous hydrochloric acid solution, and the resulting precipitate was collected by filtration. The solid was treated several times with an aqueous NaCl solution and then dried in a constant temperature bath at 60 ° C. to obtain a block copolymer. (Yield: 0.91 g, number average molecular weight: 52000)

Example 4
<Preparation of block copolymer>
Protic acid group-containing segment precursor obtained in Synthesis Example 1 (0.4 g), segment precursor having no proton acid group obtained in Synthesis Example 5 (0.5 g), potassium carbonate (28 mg, 0.2 mmol), And dehydrated DMAc (5 ml) and cyclohexane (1.5 ml) were added to a container charged with calcium carbonate (0.2 g, 2 mmol). After this solution was heated at 140 ° C. for 24 hours, the reaction solution was dropped into an aqueous hydrochloric acid solution, and the resulting precipitate was collected by filtration. The solid was treated several times with an aqueous NaCl solution and then dried in a constant temperature bath at 60 ° C. to obtain a block copolymer. (Yield: 0.84 g, number average molecular weight: 80000)

(Comparative Example 1)
A 4,4′-difluoro-3,3′-disulfonic acid sodium diphenylsulfone (0.917 g, 2 mmol) and 9, 9′-bis (4-hydroxyphenyl) fluorene (0.771 g, 2.2 mmol), potassium carbonate (0.69 g, 5 mmol), N-methylpyrrolidone (7 ml) and toluene (2 ml) were added. The mixed solution was stirred for 1 hour under heating at 140 ° C. in an oil bath, and further stirred for 6.5 hours at 165 ° C. Decafluorobiphenyl (0.334 g, 1 mmol) was added thereto, and the mixture was stirred at 120 ° C. for 2 hours. After returning the mixing solution to room temperature, the segment precursor (1.24 g) having no proton acid group obtained in Synthesis Example 2 and N-methylpyrrolidone (10 ml) were added, and the mixture was stirred at 110 ° C. for 6 hours. . The reaction solution was dropped into pure water, and the resulting white precipitate was collected by filtration. The solid was washed with warm water and then collected again by filtration, followed by vacuum drying at 100 ° C. to obtain the target block copolymer as a pink solid. (Yield: 2.4 g, number average molecular weight: 100,000)

<Manufacture of electrolyte membrane>
Film formation was performed by a solution casting method. The block copolymers obtained in Examples 1 to 3 and Comparative Example 1 were dissolved in N, N-dimethylacetamide so as to have a concentration of 10 wt%. This solution was cast on a glass plate. After drying at 45 ° C. for 12 hours under normal pressure, the film was further vacuum-dried at 80 ° C. for 12 hours to obtain a film. This membrane was immersed in a 1N aqueous sulfuric acid solution for 12 hours (acid treatment step). This acid treatment step was repeated two more times. Thereafter, the membrane was washed with pure water at 60 ° C., and dried at room temperature for 48 hours to obtain an electrolyte membrane. This was used as a test sample for each test.

<Measurement method of ion exchange capacity>
Each test sample (about 100 mg: sufficiently dried) was immersed in 20 mL of a saturated aqueous sodium chloride solution at 25 ° C., and subjected to an ion exchange reaction in a water bath at 60 ° C. for 3 hours. After cooling to 25 ° C., the membrane was thoroughly washed with ion exchanged water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this recovered solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate the ion exchange capacity.

<Measurement of proton conductivity>
Each test sample was cut into a size of 1 × 40 mm, and the AC impedance was measured by a four-terminal method. The measurement was allowed to stand at 80 ° C. and 40% RH for 2 hours, the current value was a constant current of 0.005 mA, and the sweep frequency was 10 to 20000 Hz. The proton conductivity was calculated from the obtained impedance, distance between membrane terminals (10 mm), and film thickness (30 μm).

Table 1 shows the ion exchange capacity and proton conductivity (proton conductivity) for each example and comparative example.

Claims (8)

A block copolymer having a segment having a proton acid group and a segment not having a proton acid group,
The segment having a proton acid group has a structure in which a proton acid group is bonded only to an aromatic ring to which an electron donating group is bonded;
The segment having no proton acid group has a structure including an aromatic ring to which only an electron donating group is bonded as a substituent,
The segment having a proton acid group and the segment not having a proton acid group are bonded via a structure derived from a compound selected from the group consisting of decafluorobiphenyl and hexafluorobenzene, Polymer electrolyte. The aromatic ring having only the electron donating group as a substituent, which the segment having no proton acid group has, is represented by -S-, -O-, -Ar-, and the following formula (4). The polymer electrolyte according to claim 1, which is bonded to at least one selected from the group consisting of:

(In the formula, each R ² is independently an alkyl group having 1 to 20 carbon atoms, and when there are a plurality thereof, they may be the same or different. R ³ is an alkylene group having 1 to 10 carbon atoms. .) The segment having a protonic acid group has a sulfonic acid group of 1.0 to 10.0 meq. The polymer electrolyte according to claim 1 or 2, comprising / g. A block precursor comprising a segment precursor having a proton acid group and having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene and a segment precursor having no proton acid group are block copolymerized The manufacturing method of the polymer electrolyte in any one of Claims 1-3. The segment having a proton acid group having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene,
The method for producing a polymer electrolyte according to claim 4, wherein the polymer electrolyte is obtained by protonating an oligomer having a terminal group derived from a compound selected from decafluorobiphenyl and hexafluorobenzene. The polymer electrolyte for fuel cells using the polymer electrolyte in any one of Claims 1-3. A fuel cell catalyst layer using the polymer electrolyte according to claim 1. A membrane / electrode assembly for a fuel cell using the polymer electrolyte according to any one of claims 1 to 3.