JP2008234844A - Polymer electrolyte membrane, its use, and forming method of polymer electrolyte membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane capable of suppressing methanol permeability without substantially deteriorating proton conductivity. <P>SOLUTION: In this polymer electrolyte membrane, a proton conductive polymer (a) having an acidic group and having a proton conductivity of 1 mS/cm or higher in water at 25°C is used as a matrix, and an organic compound (b) having a proton conductivity of 0.1 mS/cm or lower in water at 25°C is phase-separated and dispersed in a form of a particle having an average particle diameter of 0.1-10 μm. In the forming method of the polymer electrolyte membrane, a solution composition containing a polymer (c) in which an acidic group of the proton conductive polymer (a) forms a cation and a salt, the organic compound (c), and a solvent the boiling point of which is 300°C or lower, as an indispensable component is flow-casted on a substrate, the solvent is evaporated by heating until an amount of the solvent becomes 40% or smaller by weight to its solid content to make a self-supportive film in which at least a part of the organic compound (b) is phase-separated and dispersed in a film, and after that, it is treated by an acid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte membrane, and more particularly to a polymer electrolyte membrane suitable for a fuel cell having low methanol permeability and excellent proton conductivity.

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. Above all, polymer electrolyte fuel cells using polymer electrolyte membranes have high energy density, and because they have features such as being easy to start and stop because of lower operating temperatures than other types of fuel cells. Developments as power supply devices for electric vehicles and distributed power generation are advancing. Among these, those using liquid fuels such as methanol are excellent in portability, can be downsized, and can be manufactured relatively easily. Therefore, power supplies for portable electronic devices such as mobile phones, computers, digital cameras, video cameras, etc. Development as a power source for outdoor use has been conducted.

  However, generally used polymer electrolyte membranes exhibit proton permeability and methanol permeability. In order for the polymer electrolyte membrane to exhibit proton conductivity, it is usually necessary for water to exist. However, methanol has a high affinity with water, and thus easily permeates the polymer electrolyte membrane. When methanol permeates the polymer electrolyte membrane and moves from the fuel electrode to the air electrode, it is directly oxidized at the air electrode, resulting in a decrease in catalyst efficiency and output, and fuel consumption increases and power generation capacity decreases. Cause problems. A membrane containing a perfluorocarbon sulfonic acid polymer widely used as a polymer electrolyte membrane for fuel cells has high methanol permeability. For this reason, there may be a problem that the concentration of the aqueous methanol solution in the fuel cannot be increased and the power generation efficiency cannot be increased.

  On the other hand, so-called hydrocarbon polymer electrolyte membranes that use polymers with ionic groups such as sulfonic acid groups introduced into heat-resistant polymers such as polyimide and polysulfone are compared to perfluorocarbon sulfonic acid polymer polymer electrolyte membranes. Because of its low methanol permeability, it is expected to be used for methanol fuel cells (see, for example, Patent Document 1).

  However, even in a hydrocarbon polymer electrolyte membrane, methanol permeability increases as proton conductivity increases. In order to reduce methanol permeability while maintaining proton conductivity, water swelling has been reduced by improving the polymer structure (see, for example, Patent Document 2). In addition, in order to suppress swelling of the proton conductive polymer, a polymer electrolyte membrane combined with another crosslinkable polymer has also been proposed (see, for example, Patent Document 3). However, in such a configuration, it is difficult to control the reaction of the crosslinkable polymer, which may cause problems in the properties and uniformity of shape and reproducibility of the polymer electrolyte membrane.

  There has also been proposed a technique for suppressing methanol permeation by adding a compound having a hydroxyl group to the polymer electrolyte membrane and forming a bond between the acidic group (for example, sulfonic acid group) of the proton conductive polymer and the hydroxyl group ( For example, see Patent Document 4). However, cross-linking the acidic group of the polymer electrolyte membrane significantly impairs proton conductivity, and thus has a problem that the performance as the polymer electrolyte membrane is lowered.

  In addition, it is already known to add a compound containing a hydroxyl group to the polymer electrolyte membrane. Examples thereof include a polymer electrolyte membrane containing polyvinyl alcohol (see Patent Document 5) and a polymer electrolyte membrane containing a compound having a phenolic hydroxyl group (see Patent Document 6 or 7). Patent Document 2 also describes that a phenol resin can be blended with the proton conductive polymer. However, in these documents, there is no description about the effect of suppressing methanol permeability, and no consideration is given to the morphology in the membrane, and the methanol permeability inhibitory property is only insufficient.

JP-T-2004-509224 Japanese Patent Application Laid-Open No. 2004-149779 JP 2006-059694 A JP 2006-031970 A JP 2003-020415 A JP 2003-201403 A JP 2001-118591 A

  The present invention has been made against the background of the problems of the prior art, and is intended to suppress methanol permeability without significantly lowering proton conductivity, and has low methanol permeability and high proton conductivity. A molecular electrolyte membrane is to be provided.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polymer electrolyte membrane in which a proton-conductive polymer is used as a matrix and a non-proton conductive component is present in the form of particles has excellent methanol permeability. I found out. Furthermore, it has been found that it is better if the aprotic conductive component is insoluble in methanol, a compound containing a phenolic hydroxyl group, or the particle diameter is in a specific range. It has also been found that it is preferable that a part of the non-proton conductive compound component is mixed with the proton conductive polymer to form a matrix, and the rest are phase-separated and exist in the form of particles. In particular, it has been found that the non-proton conductive compound is preferably a polymer having a wide molecular weight distribution, more preferably a compound having a phenolic hydroxyl group, and still more preferably a resin having a specific structure. Such a polymer electrolyte membrane is made into a solution with a non-proton conductive compound in a state in which the acidic group of the proton conductive polymer is made into a salt, and after removing the solvent to form a self-supporting membrane, it is treated with an acid. In this case, it was found that it is more preferable to use a polymer having a wide molecular weight distribution as the aprotic conductive compound. Based on the findings found above, the present invention has finally been completed. That is, the present invention

(1)
An organic compound having an acidic group and a proton conductive polymer (a) having a proton conductivity in water at 25 ° C. of 1 mS / cm or more and having a proton conductivity in water of 25 ° C. of 0.1 mS / cm or less. A polymer electrolyte membrane, wherein the compound (b) is phase-separated and dispersed in the form of particles having an average particle size of 0.01 to 10 μm.

(2)
The polymer according to (1), wherein the organic compound (b) has a solubility in methanol at 25 ° C. of 1% by weight or less and a solubility in N-methyl-2-pyrrolidone at 25 ° C. of 1% by weight or more. Electrolyte membrane.

(3)
The polymer electrolyte membrane according to either (1) or (2), wherein the organic compound (b) is a compound having a molecular weight of 300 or more.

(4)
The polymer electrolyte membrane according to any one of (1) to (3), wherein the content of the organic compound (b) in the polymer electrolyte membrane is 2 to 50% by weight.

(5)
The organic compound (b) is a polymer comprising at least one compound having at least one polar group selected from the group consisting of a hydroxyl group, an alkoxy group, a cyano group and an amide group as a constituent component (1) to ( 4) The polymer electrolyte membrane according to any one of the above.

(6)
The polymer electrolyte membrane according to any one of (1) to (5), wherein the polar group is a phenolic hydroxyl group.

(7)
The high organic compound (b) according to any one of (1) to (6), wherein the organic compound (b) is at least one resin selected from the group consisting of a phenol resin, an alkylphenol resin, a phenol aralkyl resin, and a phenol cycloalkyl resin. Molecular electrolyte membrane.

(8)
In the composition ratio of the organic compound (b) to the proton conductive polymer (a) in the polymer electrolyte membrane, the value of the membrane surface with respect to the value at the center of the membrane is in the range of 80 to 120% (1) to ( 7) The polymer electrolyte membrane according to any one of the above.

(9)
A part of the organic compound (b) is dissolved or reacted in a matrix composed of the proton conductive polymer (a), and the remainder is phase-separated and dispersed. Polymer electrolyte membrane.

(10)
The polymer electrolyte membrane according to any one of (1) to (9), wherein the organic compound (b) is a compound having a molecular weight distribution in which the ratio of the weight average molecular weight to the number average molecular weight is between 10 and 100.

(11)
The organic compound (b) obtained by dissolving or reacting in the matrix composed of the proton conductive polymer (a) is a low molecular weight component having a ratio of the weight average molecular weight to the number average molecular weight of 10 to 100. The polymer electrolyte membrane according to any one of (1) to (10).

(12)
The glass transition temperature measured by the dynamic viscoelasticity method of the polymer electrolyte membrane is 5 ° C. or more lower than the glass transition temperature measured by the dynamic viscoelasticity method of the polymer electrolyte membrane consisting only of the proton conductive polymer (a). The polymer electrolyte membrane according to any one of (1) to (9).

(13)
A membrane / electrode assembly using the polymer electrolyte membrane according to any one of (1) to (12).

(14)
A fuel cell using the membrane / electrode assembly according to any one of (1) to (13).

(15)
Polymer (c) in which the acidic group of the proton conductive polymer (a) having a proton conductivity in water at 25 ° C. of 1 mS / cm or more forms a salt with a cation, and the proton conductivity in water at 25 ° C. is 0.1 mS A solution composition containing an organic compound (b) having a boiling point of not more than / cm and a solvent having a boiling point of not more than 300 ° C. as an essential constituent is cast on a substrate, and the amount of solvent is reduced relative to the solid content by heating. The solvent is evaporated to 40 wt% or less to form a self-supporting membrane in which at least a part of the organic compound (b) is phase-separated and dispersed in the membrane, and then treated with an acid ( A method for producing a polymer electrolyte membrane according to any one of 1) to (12).

(16)
The method for producing a polymer electrolyte membrane according to (15), wherein the organic compound (b) is a polymer having a ratio of a weight average molecular weight to a number average molecular weight of 10 to 100.

The polymer electrolyte membrane according to the present invention can greatly suppress methanol permeability while minimizing a decrease in proton conductivity. In particular, a remarkable effect is exhibited when the proton conductive polymer is a hydrocarbon proton conductive polymer.
Therefore, since the polymer electrolyte membrane according to the present invention is excellent in proton conductivity and can suppress methanol permeability, when used in a fuel cell using methanol as a fuel, the output can be improved or a high-concentration methanol solution can be used. Is used as a fuel to increase the energy density and improve the power generation capacity. Further, since the bondability with the electrode at the time of manufacturing the membrane / electrode assembly is improved, the resistance is reduced and the output can be improved.

  Hereinafter, the present invention will be described in detail. In addition, the weight in this invention means mass and mS is 0.001S (Siemens).

In the present invention, a proton conductive polymer (a) having an acidic group and having a proton conductivity of 1 mS / cm or more in water at 25 ° C. is used as a matrix, and the proton conductivity in water at 25 ° C. is 0.1 mS / cm. The polymer electrolyte membrane is characterized in that the following organic compound (b) is present by being phase-separated and dispersed in a granular form having an average particle size of 0.01 to 10 μm.
The proton conductive polymer (a) means a polymer having an acidic group in the molecule and showing proton conductivity of 1 mS / cm or more in water at 25 ° C., for example, sulfonic acid group, phosphonic acid group, phosphorus A polymer having an acidic group such as an acid group, a bissulfonylimide group, or a biscarbonylimide group can be used. For example, perfluoroalkyl carbon sulfonic acid polymers represented by Nafion (registered trademark), fluorine-based proton conductive polymers such as partially fluorinated sulfonated polystyrene, and hydrocarbon-based proton conductive polymers can be mentioned as examples. . There is no particular upper limit for the proton conductivity of the proton conducting polymer (a) in water at 25 ° C., but 500 mS / cm or less is suitable in terms of the balance between ease of production and other physical properties.

  The proton conductive polymer (a) in the present invention preferably has an ion exchange capacity of 0.1 to 5.0 meq / g, and more preferably has an ion exchange capacity of 0.5 to 2.5 meq / g. . Furthermore, it is more preferable to have an ion exchange capacity of 0.5 to 1.5 meq / g, and it is more preferable to have an ion exchange capacity of 0.7 to 1.3 meq / g. Proton conducting polymers with smaller ion exchange capacity have lower methanol permeability. The proton conductive polymer having a larger ion exchange capacity has a higher proton conductivity.

  The proton conductive polymer (a) in the polymer electrolyte membrane of the present invention is preferably a hydrocarbon proton conductive polymer. This is because the hydrocarbon-based polymer electrolyte membrane has advantages such as being free of halogen, having less harmful emissions, and being able to reduce costs, as compared with the fluorine-based polymer electrolyte membrane. A hydrocarbon-based polymer electrolyte membrane can overcome the above-mentioned drawbacks by compounding with a titanate fiber. The hydrocarbon-based proton-conducting polymer is mainly composed of a hydrocarbon-based polymer whose main structure may contain a hetero atom such as an oxygen atom, a sulfur atom, or a nitrogen atom. A group having an acidic ionic group such as a group, a sulfonimide group, a phosphoric acid group or a carboxyl group. As the ionic group, a strong acid group such as a sulfonic acid group or a sulfonimide group is preferable because proton conductivity increases, and a phosphonic acid group or a phosphoric acid group exhibits proton conductivity even under high temperature and low humidity conditions. preferable. The hydrocarbon polymer may partially contain other elements such as halogen elements such as fluorine and bromine and phosphorus.

  Specific examples of the polymer constituting the hydrocarbon proton conductive polymer of the present invention include polyarylene, polyarylene ether, polyarylene sulfide, polyarylene ether sulfide, polyarylene ether nitrile, polyarylene ether nitrile sulfide, polysulfone. , Heat-resistant polymers such as polyethersulfone, polyphenylsulfone, polyetherketone, polyetheretherketone, polyimide, polybenzazole, polyetherimide, polyamide, and polyamideimide, but are not limited thereto. is not.

  Among them, polyarylene ether, polyarylene sulfide, polyarylene ether sulfide, polyarylene ether nitrile, polyarylene ether nitrile sulfide, polysulfone, polyethersulfone, polyphenylsulfone, polyetherketone, polyetheretherketone are more preferable examples. It can be mentioned, but is not limited to these.

  The hydrocarbon proton conductive polymer in the present invention is preferably mainly composed of an aromatic polymer, but may partially have an aliphatic group. For example, at least part of the side chain or main chain may be composed of an aliphatic group.

  The hydrocarbon proton conductive polymer in the present invention contains a sulfonic acid group, and includes at least one of polymers such as polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone. It is preferable that any one of a polyarylene ether compound, a polyarylene sulfide compound, and a polyarylene compound is used as a constituent component. This is because these polymers are easy to synthesize, have good solubility in solvents, and are excellent in heat resistance and mechanical properties.

  The hydrocarbon-based proton conductive polymer in the present invention preferably has an ion exchange capacity of 0.5 to 3.0 meq / g, more preferably 0.5 to 2.5 meq / g. It is more preferable to have an ion exchange capacity of 0.5 to 1.5 meq / g, and it is more preferable to have an ion exchange capacity of 0.7 to 1.3 meq / g.

  A preferred embodiment of the hydrocarbon proton conductive polymer in the present invention is selected from one or more structures selected from the structure represented by the following general formula (1) and a structure represented by the following general formula (2). It is a hydrocarbon-based proton conductive polymer composed of one or more polymers selected from the group consisting of polymers having one or more structures.

[In General Formulas (1) and (2), X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and R ¹ represents the number of carbon atoms. Any one of 1 to 10 alkylene groups, oxyalkylene groups, aryl groups and direct bonds (of the —SO ₃ Y group), R ² and R ³ each independently include a sulfur atom or an oxygen atom. One or more groups selected from the group consisting of an alkylene group, an aralkyl group, and an aromatic group, which may have 2 to 20 carbon atoms, Ar ¹ is a divalent aromatic group having an electron-withdrawing group Z or Z ′ represents either an oxygen atom or a sulfur atom, and m1 and m2 each represents an integer of 1 to 1000 in terms of the number of moles of each structural unit in the polymer molecule. ]

  The hydrocarbon proton conductive polymer in the present invention may contain a plurality of structural units within the range of the structural unit represented by the general formula (1) or (2). Moreover, the coupling | bonding mode of the structural unit represented by General formula (1) and the structural unit represented by General formula (2) is not specifically limited, You may couple | bond together at random. A block structure in which any one of the structural units represented by formula (1) and general formula (2) is continuous, or a block in which the structural unit represented by general formula (1) is continuous and general formula (2) The structural unit represented by general formula (1) and the structural unit represented by general formula (2) may be combined alternately. It may be.

X in the general formula (1) is preferably an —S (═O) ₂ — group because solubility in a solvent is improved. It is preferable that X is a —C (═O) — group because the softening temperature of the polymer can be lowered to enhance the bonding property with the electrode, or the photocrosslinking property can be imparted to the electrolyte membrane. When used as a polymer electrolyte membrane, Y is preferably an H atom. However, if Y is an H atom, it is easily decomposed by heat or the like. Therefore, during processing such as manufacturing of an electrolyte membrane, Y is set as an alkali metal salt such as Na or K, and Y is converted to H atom by acid treatment after processing. A polymer electrolyte membrane can also be obtained by conversion. Z is preferably O because it has advantages such as little polymer coloring and easy availability of raw materials. Z is preferably S because oxidation resistance is improved.

R ¹ in the general formula (1) represents an alkylene group having 1 to 10 carbon atoms, an oxyalkylene group, an aryl group, or a direct bond. An alkylene group is preferable because proton conductivity is improved. In addition, a direct bond in which a sulfonic acid group and a benzene ring are directly bonded is more preferable because stability of the sulfonic acid group with respect to heat, radicals, and the like is increased and proton conductivity is excellent. The alkylene group is preferably a straight chain rather than a branched one. As for carbon number of an alkylene group, 1-5 are more preferable, and 3-4 are more preferable. Specifically, an n-propylene group and an n-butylene group are preferable. 1-5 are more preferable and, as for carbon number of an oxyalkylene group, 3-4 are more preferable. Specifically, an oxy-n-propylene group and an oxy-n-butylene group are preferable. Examples of the aryl group include an oxyphenylene group and a phenylene group.

  In the general formula (1), the following general formula (3);

  Specific examples of the partial structure represented by formula (1) are shown below, but are not limited thereto, and include those in which a part and all of the sulfonic acid groups form a monovalent cation. Of the following partial structures, Chemical Formulas 3A, 3B, 3C, and 3D are more preferable, and Chemical Formulas 3A and 3B are more preferable.

R ² and R ³ in the general formulas (1) and (2) are each independently an alkylene group, an aralkyl group or an aromatic group having 2 to 20 carbon atoms which may contain a sulfur atom or an oxygen atom. One or more groups selected from the group consisting of groups. Examples of R ² and R ³ include aromatic rings such as a benzene ring and a pyridine ring, condensed polycyclic aromatic groups such as a naphthalene ring and an anthracene ring, and an aromatic group having a direct bond, an aliphatic group, a sulfone group, Examples include, but are not limited to, a group connected by an aliphatic group including an ether group, a sulfide group, a perfluoroalkyl group and an aromatic group, an aliphatic group, and an aliphatic group including an aromatic group. It is not something. R ² and R ³ in the general formulas (1) and (2) may have a plurality of structures.

Examples of R ¹ and R ² in the general formulas (1) and (2) are shown below, but are not limited thereto.

Among the structures described as examples of R ² and R ³ in the general formulas (1) and (2), the structural units represented by the chemical formulas 4E and 4AV are preferable because they suppress swelling of the polymer electrolyte membrane. In addition, the structures of chemical formulas 4F, 4G, 4N, 4O, 4U, 4Y, etc. are preferable because the softening temperature of the polymer electrolyte membrane is lowered to improve the bondability with the electrode catalyst layer. The structures represented by the chemical formulas 4AX and 4AY are also preferable because the softening temperature of the polymer electrolyte membrane is lowered, so that the bonding property with the electrode catalyst layer is improved. Furthermore, the structure represented by the chemical formulas 4AY to 4BN is preferable because the bondability with the electrode catalyst layer is improved and the durability is improved, and the structure represented by the chemical formulas 4AO, 4AI, 4AN, 4AQ, and 4X is This is preferable because methanol permeability is suppressed. Further, the structures represented by the chemical formulas 4I, 4J, and 4K are preferable because they suppress flooding in the fuel cell. The structure represented by the chemical formula 4BO is preferable because it improves the durability of the polymer electrolyte membrane. ^In the case of the ^{structure R 20} and ^{R 21} is represented by the chemical formula 4AY～4BN, it is preferred formula (9) and (10) Z and Z 'in is a sulfur atom. O in Chemical Formula 4N represents an integer of 2 to 10.

R ² and R ³ in the general formulas (1) and (2) may be composed of a plurality of groups. As a preferable combination, a structure represented by the chemical formula 4E and a chemical formula 4F, 4G, 4N, 4O In combination with one or more structures selected from the group consisting of structures represented by 4U, 4Y, 4AX, 4AY, 4AY-4BN, from structures represented by chemical formulas 4F, 4G, 4N, 4O, 4U, 4Y A combination of one or more structures selected from the group consisting of and one or more structures selected from the group consisting of structures represented by 4AY to 4BN, a structure represented by the chemical formulas 4AO, 4AI, 4AN, 4AQ, 4X A combination of at least one structure selected from the group consisting of and one or more structures selected from the group from the structures represented by 4AY to 4BN is preferable. Further, the above-mentioned preferred structure and the preferred combination of the structures are combined with chemical formulas 4I, 4J, and 4K to obtain a flooding suppression effect, and further combined with the structure represented by chemical formula 4BO to obtain a durability improvement effect. be able to.

Ar ¹ in the general formula (2) is preferably a divalent aromatic group having an electron-withdrawing group. Examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid amide group, a sulfonic acid imide group, a carboxyl group, a carbonyl group, a carboxylic acid ester group, a cyano group, a halogen group, Although a trifluoromethyl group, a nitro group, etc. can be mentioned, it is not limited to these, What is necessary is just a well-known arbitrary electron withdrawing group.

It shows an example of the structure of Ar ¹ in the general formula (2) below, but is not limited thereto.

A preferred structure of Ar ¹ in the general formula (2) is a structure represented by the chemical formulas 5A to 5D, among which the structures represented by the chemical formulas 5C and 5D are more preferable, and the structure represented by the chemical formula 5D is more preferable. The structure of Chemical Formula 5A is preferable because it can increase the solubility of the polymer. The structure of the chemical formula 5B is preferable because it lowers the softening temperature of the polymer to enhance the bonding property with the electrode or impart photocrosslinkability. The structure of Chemical Formula 5C or 5D is preferable because the swelling of the polymer can be reduced, and the structure of Chemical Formula 5D is more preferable. Ar ² in the general formula (10) may be composed of a plurality of structures, and when composed of a plurality of structures, two or more structures selected from the group consisting of chemical formulas 5A to 5D, or a chemical formula 5A A combination of at least one structure selected from the group consisting of -5D and at least one structure selected from the group consisting of chemical formulas 5E-5P is preferred.

  Examples of the polymer constituting the proton conductive polymer (a) in the present invention include two or more compounds selected from the group consisting of aromatic dihalogen compounds and aromatic dinitro compounds activated with an electron-withdrawing group, and bisphenol. One or more compounds selected from the group consisting of a compound, a bisthiophenol compound, and an alkyldithiol compound can be polymerized by an aromatic nucleophilic substitution reaction by heating in the presence of a basic compound.

  Among aromatic dihalogen compounds activated with an electron-withdrawing group, those having an ionic group include 3,3′-disulfo-4,4′-dichlorodiphenylsulfone, 3,3′-disulfo-4, 4'-difluorodiphenyl sulfone, 3,3'-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl sulfone, and their sulfonic acid groups are monovalent cations Examples include salts with seeds. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone. 3,3′-sodium disulfonate-4,4′-dichlorodiphenyl ketone, 3,3′-sodium disulfonate-4,4′-difluorodiphenylsulfone, 3,3′-sodium disulfonate-4,4 ′ -Difluorodiphenyl ketone, potassium 3,3'-disulfonate 4,4'-dichlorodiphenyl sulfone, potassium 3,3'-disulfonate 4,4'-difluorodiphenyl sulfone, potassium 3,3'-disulfonate 4,4 '-Dichlorodiphenyl ketone, potassium 3,3'-disulfonate 4,4'-difluorodi Phenylsulfone, potassium 3,3′-disulfonate 4,4′-difluorodiphenyl ketone, sodium 3,3′-bis (butylsulfonate) -4,4′-dichlorodiphenylsulfone, 3,3′-bis (butyl) Sulfonic acid) sodium-4,4′-difluorodiphenylsulfone, 3,3′-bis (butylsulfonic acid) sodium-4,4′-dichlorodiphenylketone, 3,3′-bis (butylsulfonic acid) sodium-4 , 4′-difluorodiphenylsulfone, 3,3′-bis (butylsulfonic acid) sodium-4,4′-difluorodiphenylketone, 3,3′-bis (butylsulfonic acid) potassium 4,4′-dichlorodiphenylsulfone 3,3′-bis (butylsulfonic acid) potassium 4,4′-difluorodiphenylsulfone 3,3′-bis (butylsulfonic acid) potassium 4,4′-dichlorodiphenyl ketone, 3,3′-bis (butylsulfonic acid) potassium 4,4′-difluorodiphenylsulfone, 3,3′-bis ( Butylsulfonic acid) potassium 4,4′-difluorodiphenyl ketone, 3,3′-bis (phenylsulfonic acid) sodium-4,4′-dichlorodiphenylsulfone, 3,3′-bis (phenylsulfonic acid) sodium-4 , 4′-difluorodiphenylsulfone, 3,3′-bis (phenylsulfonic acid) sodium-4,4′-dichlorodiphenylketone, 3,3′-bis (phenylsulfonic acid) sodium-4,4′-difluorodiphenyl Sulfone, 3,3′-bis (phenylsulfonic acid) sodium-4,4′-difluorodiphenyl Ketone, 3,3′-bis (phenylsulfonic acid) potassium 4,4′-dichlorodiphenylsulfone, 3,3′-bis (phenylsulfonic acid) potassium 4,4′-difluorodiphenylsulfone, 3,3′-bis (Phenylsulfonic acid) potassium 4,4′-dichlorodiphenyl ketone, 3,3′-bis (phenylsulfonic acid) potassium 4,4′-difluorodiphenylsulfone, 3,3′-bis (phenylsulfonic acid) potassium 4, 4'-difluorodiphenyl ketone, and the like, such as sodium 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone, sodium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone, 3 , 3′-diketonate sodium-4,4′-dichlorodiphenyl ketone, 3,3′- Sodium ketonate-4,4′-difluorodiphenyl ketone is preferred, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone Is more preferable.

  The activated aromatic dihalogen compound containing no ionic group includes 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4, 4'-dichlorodiphenyl sulfone, 4,4'-difluorodiphenyl sulfone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, decafluorobiphenyl, 3,3'-bis (trifluoromethyl) -4, 4'-dichlorobiphenyl, 3,3'-bis (trifluoromethyl) -p-terphenyl, and the like, but not limited thereto, other aromatics active in aromatic nucleophilic substitution reaction Dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like can also be used. Among these, 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,6-dichlorobenzonitrile, 2,6 are preferable. -Difluorobenzonitrile is more preferred.

  Examples of the bisphenol compound or bisthiophenol compound include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 4,4′-biphenol, 4 , 4'-dimercaptobiphenyl, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) Methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, bis (4 -Hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) Methane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4-hexyl resorcinol, 2,2-bis (4-hydroxyphenyl) Hexafluoropropane, hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 4,4′-thiodiphenol, 4,4′-oxydiphenol, 1,3-bis (4-hydroxyphenyl) adamantane, 2, 2-bis (4-hydroxyphenyl) adamantane, 4,4′-thiobisbenzenethiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 10- (2,5-dihydroxyphenyl) -9,10- Dihydro-9-oxa-10-phosphaphenant -10-oxide, 4,4′-biphenol, 9,9-bis (4-hydroxyphenyl) fluorene, 1,3-bis (4-hydroxyphenyl) adamantane, 4,4′-thiodiphenol, 4, 4′-oxydiphenol, 4,4′-thiobisbenzenethiol, 4-ethylresorcinol, 4-hexylresorcinol, 2-hexylhydroquinone, 2-octylhydroquinone, 2-octadecylhydroquinone, 2-tertiarybutylhydroquinone, 2,5-ditertiary butyl hydroquinone, 2,5-ditertiary amyl hydroquinone, 2,2′-dihexyl-4,4′-dihydroxybiphenyl, 1-octyl-2,6-dihydroxynaphthalene, 2-hexyl-1, 5-dihydroxynaphthalene, etc. However, the present invention is not limited thereto, and any compound that can react with the aromatic dihalogen compound or aromatic dinitro compound activated with the electron-withdrawing group can be used.

  Examples of alkyldithiol compounds include 1,2-ethanedithiol, 1,3-propanedithiol, 1,2-propanedithiol, 1,4-butanedithiol, 2,3-dihydroxy-1,4-butanedithiol, , 5-pentanedithiol, 1,6-hexanedithiol, 1,7-heptanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,11-undecanedithiol, 1, 12-dodecanedithiol, 1,13-tridecanedithiol, 1,14-tetradecanedithiol, 1,15-pentadecanedithiol, 1,16-hexadecanedithiol, 1,17-heptadecanedithiol, 1,18-octadecanedithiol, 1 , 19-nonadecanedithiol, 1,20- Cosanedithiol, 3,6-dioxa-1,8-octanedithiol, 3,7-dithia-1,9-nonanedithiol, 3-thia-1,5-pentanedithiol, 2,3-dihydroxy-1,4- Examples include butanedithiol, 1,4-bis (mercaptomethyl) benzene, 1,3-bis (mercaptomethyl) benzene, 1,2-bis (mercaptomethyl) benzene, and the like. Any compound that can react with an aromatic dihalogen compound or an aromatic dinitro compound activated with an electron-withdrawing group can be used.

  When the proton conductive polymer (a) used in the present invention is polymerized by aromatic nucleophilic substitution reaction, two or more compounds selected from the group consisting of activated aromatic dihalogen compounds and activated dinitroaromatic compounds, and bisphenol A polymer can be obtained by adding one or more compounds selected from the group consisting of a compound, a bisthiophenol compound and an alkyldithiol compound, and heating and reacting in the presence of a basic compound. By setting the molar ratio of the reactive halogen group or nitro group to the reactive hydroxy group or mercapto group in the monomer to an arbitrary molar ratio, the degree of polymerization of the resulting polymer can be adjusted. Is 0.8 to 1.2, more preferably 0.9 to 1.1, more preferably 0.95 to 1.05, and 1 to obtain a polymer with the highest degree of polymerization. Can do.

  The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more.

  In the above polymerization reaction, a bisphenol compound, a bisthiophenol compound, and an alkyldithiol compound are reacted with an isocyanate compound such as phenyl isocyanate without using a basic compound, and an activated dihalogen aromatic. A compound or a dinitroaromatic compound can also be directly reacted.

  Examples of basic compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc., but those capable of converting aromatic diols and aromatic dimercapto compounds into active phenoxide structures If it is, it can be used without being limited to these. The basic compound can be polymerized satisfactorily by using an amount of 100 mol% or more as an alkali metal with respect to the hydroxyl group and mercapto group of the bisphenol compound, bisthiophenol compound and alkyldithiol compound, preferably bisphenol It is the range of 105-125 mol% as an alkali metal with respect to a hydroxyl group and a mercapto group of a compound, a bisthiophenol compound, and an alkyldithiol compound. An excessive amount of the basic compound is not preferable because it causes side reactions such as decomposition.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration. In addition, a polymer solution can be obtained by removing by-product salts by filtration.

  Further, the proton conductive polymer (a) used in the polymer electrolyte membrane of the present invention preferably has a logarithmic viscosity of 0.1 dL / g or more measured by a method described later. When the logarithmic viscosity is less than 0.1 dL / g, the membrane tends to become brittle when molded as a polymer electrolyte membrane. The logarithmic viscosity is more preferably 0.3 dL / g or more. On the other hand, when the logarithmic viscosity exceeds 5 dL / g, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  In the present invention, when the polymer constituting the proton conductive polymer (a) has a phenylene group in which one or more atoms selected from the group consisting of an oxygen atom and a sulfur atom are bonded to both ends, This is preferable because the miscibility with the polymer having a hydroxyl group is improved. Such a structure includes 4,4′-dihydroxydiphenyl ether, 4,4′-thiobisbenzenethiol, 4,4′-thiobisphenol, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dichloro as raw materials. It can introduce | transduce into a polymer by using compounds, such as a diphenyl ether, 4,4'- dichloro diphenyl sulfide, 4,4'- diamino diphenyl ether, and 4,4'- diamino diphenyl sulfide.

The organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C. is preferably a compound having substantially no proton conductivity. The proton conductivity can be measured by any known method, but it is preferably measured by the AC impedance method as described later. The proton conductivity of the organic compound (b) can be measured by a film-shaped product or a pellet-shaped product. There is no particular lower limit for the proton conductivity in water at 25 ° C. of the organic compound (b) whose proton conductivity in water at 25 ° C. is 0.1 mS / cm or less, but there is a balance between ease of production and other physical properties. To 0.000001 mS / cm or more is suitable.
The organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C. has a solubility in methanol of 1% by weight or less at 25 ° C., and with respect to N-methyl-2-pyrrolidone at 25 ° C. The solubility is preferably 1% by weight or more. This is because if the solubility in methanol is large, swelling of the polymer electrolyte membrane due to methanol increases and methanol permeation increases. The solubility in methanol is more preferably 0.5% by weight or less, further preferably 0.1% by weight or less, and most preferably substantially insoluble. The organic compound (b) having a proton conductivity of 0.1 mS / cm or less is preferably not dissolved in water that is a product of a power generation reaction in the fuel cell.

  In addition, the organic compound (b) having a proton conductivity of 0.1 mS / cm or less is phase-separated and dispersed in the form of particles in a matrix mainly composed of the proton conductive polymer (a) which is a polar compound. It is preferable that the organic compound (b) having a proton conductivity of 0.1 mS / cm or less has a moderate affinity with the proton conductivity. In that respect, any compound having a solubility of 1% by weight or more with respect to N-methyl-2-pyrrolidone capable of dissolving much of the proton conductive polymer, for example, the proton conductive polymer (a) and A solution in which the organic compound (b) having a proton conductivity of 0.1 mS / cm or less is dissolved in N-methyl-2-pyrrolidone can be obtained. This is preferable because it becomes easy to obtain a polymer electrolyte membrane in which the organic compound (b) having a conductivity of 0.1 mS / cm or less is dispersed in the form of micro particles. The solubility in N-methy-2-pyrrolidone is more preferably 5% by weight or more, still more preferably 20% by weight or more, and further preferably 50% by weight or more.

  The molecular weight of the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C. is preferably 300 or more. If it is smaller than 300, the particulate structure cannot be formed well in the matrix, or even if it can, the mechanical strength of the polymer electrolyte membrane may decrease. More preferably, it has a molecular weight of 1000 or more.

  In the polymer electrolyte membrane of the present invention, the content of the organic compound (b) whose proton conductivity in water at 25 ° C. is 0.1 mS / cm or less is preferably 2 to 50% by weight. This is because if it is less than 2% by weight, a sufficient methanol permeation suppressing effect may not be obtained. Moreover, it is because the mechanical strength of a polymer electrolyte membrane may fall that it is 50 weight% or more. More preferably, it is in the range of 3 to 30% by weight.

  In the polymer electrolyte membrane of the present invention, the phase composed of the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C. existing in the form of particles has an average particle size of 0. It is preferably in the range of 0.01 to 10 μm. This is because if the average particle size is less than 0.01 μm, the methanol permeation suppression effect may be small. Further, if the average particle size is 10 μm or more, the mechanical strength of the polymer electrolyte membrane may be reduced, or the proton conductivity of the polymer electrolyte membrane may be uneven, which is not preferable. A more preferable range is 0.1 to 5 μm. The average particle diameter can be determined by any known method. For example, the cross section of the polymer electrolyte membrane is treated with a metal compound or metal ion to stain the proton conductive polymer, and then observed with a transmission electron microscope. Thus, it can be obtained from the image.

  The organic compound (b) whose proton conductivity in water at 25 ° C. is 0.1 mS / cm or less is a compound having one or more polar groups selected from the group consisting of a hydroxyl group, an alkoxy group, a cyano group, and an amide group. It is preferable that the polymer be at least one component. This is because when the compound having the polar group as described above is contained, the affinity with the proton conductive polymer is improved. Among polar groups, a hydroxyl group, an alkoxy group, and a cyano group are preferable, a hydroxyl group and an alkoxy group are more preferable, and a hydroxyl group is still more preferable. Furthermore, the hydroxyl group is preferably bonded to an aromatic group, more preferably a phenolic hydroxyl group. This is because a compound having a phenolic hydroxyl group has an appropriate polarity, so that it can be easily mixed with the proton-conductive polymer and a mixed polymer electrolyte membrane can be easily produced.

  Examples of the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C. include phenol resin, alkylphenol resin, phenol aralkyl resin, phenol cycloalkyl resin, and poly (ethylene / vinyl alcohol). Polymer, polyacrylamide copolymer, polycyanoacrylate copolymer, poly (4-cyanostyrene) Kyoto polymer, alkoxylated phenol resin, alkoxylated alkylphenol resin, alkoxylated phenol aralkyl resin, alkoxylated phenol cycloalkyl resin, etc. However, it is not limited to these. Among them, a phenol resin, an alkylphenol resin, a phenol aralkyl resin, and a phenol cycloalkyl resin are preferable in terms of excellent methanol permeation suppression, and an alkylphenol resin and a phenol aralkyl resin are more preferable.

  In the polymer electrolyte membrane of the present invention, the proton conductivity in water at 25 ° C. is 0.1 mS / cm or less with respect to the proton conductive polymer (a) whose proton conductivity in water at 25 ° C. is 1 mS / cm or more. The composition ratio of the organic compound (b) is preferably such that the value on the film surface is in the range of 80 to 120% relative to the value at the center of the film. A large difference in composition ratio between the surface and the inside of the membrane is not preferable because it causes deformation of the polymer electrolyte membrane and deterioration of properties. The composition ratio can be analyzed by an arbitrary method, and can be measured using, for example, a total reflection infrared spectroscopic analyzer. In that case, the inside of the membrane can be measured by measuring the fractured surface after cleaving the polymer electrolyte membrane in the membrane surface direction with a razor or the like.

  Further, when the matrix made of the proton conductive polymer (a) contains an organic compound (b) having a proton conductivity of 0.1 mS / cm or less in water at 25 ° C., the methanol permeation suppression property is enhanced. To preferred. Whether the matrix contains the organic compound (b) having proton conductivity of 0.1 mS / cm or less is determined by any known method such as composition analysis, X-ray analysis, microscopic IR, DSC, thermomechanical analysis, etc. Can be judged by. For example, when the melting point or glass transition temperature of the organic compound (b) having proton conductivity of 0.1 mS / cm or less is lower than that of proton conductivity, the softening temperature or glass transition temperature of the polymer electrolyte membrane When the temperature is lower than the softening temperature or the glass transition temperature of the polymer electrolyte membrane made of only the proton conductive polymer, it can be determined that it is also contained in the matrix. The softening temperature and glass transition temperature of the polymer electrolyte membrane can be measured by any known method. For example, the elastic modulus is measured by changing the temperature by the dynamic viscoelasticity method, and the loss elasticity relative to the storage elastic modulus is measured. The peak temperature of the ratio of ratios (tan δ) can be determined as the glass transition temperature, and the inflection point in the vicinity where the storage elastic modulus starts to greatly decrease can be determined as the softening temperature.

  The organic compound (b) having a proton conductivity of 0.1 mS / cm or less is a compound having a molecular weight distribution, and the ratio of the weight average molecular weight to the number average molecular weight is preferably between 10 and 100. Furthermore, it is preferable that a component having a low molecular weight is contained in a matrix made of a proton conductive polymer, and it is more preferable that a component having a high molecular weight forms a particulate phase. When the organic compound (b) having a proton conductivity of 0.1 mS / cm or less has a molecular weight distribution, the number average molecular weight is in the range of 300 to 10,000, and the weight average molecular weight is in the range of 3000 to 1000000. preferable.

  A method for producing a polymer electrolyte membrane having a structure defined in the present invention will be described below. The polymer electrolyte membrane of the present invention is obtained by casting a solution obtained by dissolving a proton conductive polymer (a) and an organic compound (b) having a proton conductivity of 0.1 mS / cm or less onto a substrate, Can be obtained by removing. At that time, it is preferable that both the proton conductive polymer (a) and the organic compound (b) having a proton conductivity of 0.1 mS / cm or less can be dissolved as a solvent. This is because if the solvent cannot dissolve any of the components, a uniform solution cannot be obtained, which hinders molding. The boiling point of the solvent is preferably less than 300 ° C. This is because if the solvent has a boiling point of 300 ° C. or lower, it can be removed by heating, for example, and the removal becomes easy. In order to remove a solvent having no boiling point or a remarkably high solvent, the proton conductive polymer (a) and the organic compound (b) having a proton conductivity of 0.1 mS / cm or less are insoluble. This is because a treatment such as immersing in another solvent that can be mixed is required, and the polymer electrolyte membrane becomes porous, so that a preferable polymer electrolyte membrane cannot be obtained.

  The method for removing the solvent is preferably heating, and the heating means can be performed by any known method such as far infrared heater, infrared heater, microwave heater, hot air, substrate heating, etc. Removal with hot air is preferred because it is simple and efficient. After casting the solution, the solvent is preferably removed by heating until the film is self-supporting. If the amount of solvent in the polymer electrolyte membrane is 40% by weight or less, a self-supporting membrane can be obtained. The amount of solvent at this time is more preferably 10 to 30% by weight. It is because peeling from a base material will become difficult that it is 10 weight% or less, manufacture may become difficult, or a quality may fall. Further, the proton conductive polymer preferably has an acidic group forming a salt with a cation. This is because the organic compound (b) having a proton conductivity of 0.1 mS / cm or less is formed into particles and the organic compound (b) having a proton conductivity of 0.1 mS / cm or less is formed by an acidic group. This is to prevent side reactions. When the acidic group of the proton conductive polymer forms a salt with a cation, the polarity increases, and with the removal of the solvent, an appropriate phase separation proceeds and a higher order structure as in the present invention can be obtained. . As the cation, alkali metal ions such as Na, K, and Li are preferable. The proton-conductive acidic group can be converted into an acidic group by forming a self-supporting membrane and then removing the excess solvent and treating with an acid. In order to remove the solvent from the membrane, heating may be performed. However, since the removal rate decreases when the residual amount is small, the proton conductive polymer such as water and the organic compound having a concentration of 0.1 mS / cm or less are insoluble. And extraction with a substance miscible with the solvent is preferred. As the acid used for the acid treatment, a strong acid such as sulfuric acid, hydrochloric acid, perchloric acid, methanesulfonic acid, trifluoroacetic acid and the like can be used, and sulfuric acid and hydrochloric acid are preferable. Moreover, it is preferable to use an acid as aqueous solution, and it is preferable that the density | concentration is 0.1-5 mol / L. After the acid treatment, in order to remove excess acid, it is preferable to wash thoroughly with water or the like, or to heat when using a volatile acid such as hydrochloric acid.

  In the method for producing a polymer electrolyte membrane of the present invention, the organic compound (b) having a proton conductivity of 0.1 mS / cm or less has a molecular weight distribution, and the ratio of the weight average molecular weight to the number average molecular weight is 10. It is more preferable that the polymer is between ˜100 because a polymer electrolyte membrane containing a part of the organic compound in the matrix can be obtained.

  One preferred embodiment of the organic compound (b) having a solubility in methanol at 25 ° C. of 1% by weight or less in the present invention is one or more compounds selected from the group consisting of phenolic hydroxyl group-containing resins. Can do. The phenolic hydroxyl group-containing resin is a polymer having a phenolic hydroxyl group-containing compound as a constituent component, and a phenolic hydroxyl group, that is, a compound residue having a hydroxyl group directly bonded to an aromatic ring is directly or by another group. A polymer having a linked structure can be shown as an example, but is not limited thereto.

  Examples of the group linking a compound residue having a hydroxyl group include a methylene group, an ethylene group, an alkylene group having 3 or more carbon atoms, an alkenylene group, an aralkylene group, a sulfide group, an ether group, a carbonyl group, a sulfonyl group, and a sulfone group. However, it is not limited to these. When the phenolic hydroxyl group-containing compounds are linked to each other, the number of atoms substantially contributing to the linkage is preferably 1 (for example, methylene group, 1,1-ethylene group, 2,2-propylene). Group, sulfide group, ether group, carbonyl group, sulfonyl group, sulfone group, etc.). When the phenolic hydroxyl group-containing compound is linked with an ethylene group, the phenolic hydroxyl group-containing compound is preferably bonded to the same carbon atom. When the linking group is an alkylene group having 3 or more carbon atoms, the alkyl group preferably has a cyclic structure. In addition, the phenolic hydroxyl group-containing compound is preferably bonded with a cyclic alkylene group or an aralkylene group. Alternatively, a structure in which a phenolic hydroxyl group-containing compound and an aromatic compound are linked by a methylene group, 1,1-ethylene group, 2,2-propylene group, sulfide group, ether group, carbonyl group, sulfonyl group, sulfone group, etc. Even preferred. When the linking group is an aralkylene group, it is preferably bonded to the phenolic hydroxyl group-containing compound by a methylene group bonded to an aromatic group or a methylene group substituted with an alkyl group. When the phenolic hydroxyl group-containing compound is bonded with a 1,2-ethylene group (for example, poly (4-hydroxystyrene)), the solubility in methanol increases, and the polymer electrolyte membrane In some cases, it is impossible to achieve the problem of suppressing methanol permeability.

  Examples of the phenolic hydroxyl group-containing resin include a phenol aralkyl resin, a phenol cycloalkyl resin, an alkyl phenol resin, a phenol terpene resin, an aralkyl group-substituted phenol resin, a phenyl group-substituted phenol resin, and a phenoxy group-substituted phenol resin. Among them, a phenol aralkyl resin is one of preferable resins because of its excellent solubility and mixing properties. When these resins are used, there is also a secondary effect that the softening temperature of the proton conductive polymer is lowered and the workability is improved, such as bonding with an electrode by hot pressing.

  The phenolic hydroxyl group-containing resin preferably has a solubility in N-methyl-2-pyrrolidone at 25 ° C. of 1% by weight or more. The solubility in N-methyl-2-pyrrolidone is preferably 10% by weight or more, and more preferably 20% by weight. The phenolic hydroxyl group content of the phenolic hydroxyl group-containing resin is preferably in the range of 0.001 to 0.01 mol / g, and more preferably in the range of 0.005 to 0.01 mol / g. The molecular weight of the phenolic hydroxyl group-containing resin is preferably in the range of 100 to 1000000. The lower the molecular weight, the better the miscibility with the polymer electrolyte membrane, which is preferable. However, there are cases where the detachability increases and the mechanical properties of the polymer electrolyte membrane may decrease. As the molecular weight increases, the mechanical properties of the polymer electrolyte membrane improve, but the affinity with the polymer electrolyte membrane may decrease. The amount of the polymer of the phenolic hydroxyl group-containing compound relative to the proton conductive polymer (a) is preferably in the range of 2 to 50% by weight, and in the range of 3 to 20% by weight of the proton conductive polymer. Further preferred. The proton conductive polymer is not particularly limited, but a hydrocarbon proton conductive polymer is preferable because of its large methanol permeation suppressing effect, and an aromatic hydrocarbon proton conductive polymer is effective for suppressing methanol permeation. It is more preferable because it is larger.

  In the polymer electrolyte membrane according to the present invention, a polymer (resin) having the phenolic hydroxyl group-containing compound as a constituent component as an organic compound (b) having a proton conductivity of 0.1 mS / cm or less is a proton conductive polymer (a It is not clear how the polymer electrolyte membrane existing in the form of a matrix in the matrix is excellent in methanol permeability inhibition, but the polymer has low solubility (preferably not soluble) in methanol. It is assumed that the particulate matter in the membrane suppresses methanol permeation. In addition, since the phenolic hydroxyl group-containing compound has a molecular weight distribution, it exhibits a better methanol blocking property. Therefore, the phenolic compound present in a microparticulate form with appropriate mixing with a low molecular component matrix. It is presumed that the hydroxyl group-containing compound acts synergistically to show an excellent effect. Moreover, it is guessed that the phenolic hydroxyl group contributes to affinity with a proton conductive polymer (a). That is, since the proton conductive polymer having an acidic group such as a sulfonic acid group or a phosphonic acid group or a polar group such as a basic group is easily mixed with a highly polar substance, the polymer having a polar phenolic hydroxyl group is used. Is presumed to be effective by mixing appropriately with a proton-conductive polymer. Even if the compound is poorly soluble in methanol, if the affinity for the proton conducting polymer (a) is low, it becomes difficult to uniformly disperse in the polymer electrolyte membrane, and the methanol permeation inhibiting effect Is not only obtained, but also very likely to hinder the formation of the film. Further, in the present invention, a polymer having another polar group, for example, a carboxyl group, a sulfonic acid group, a phosphonic acid group, an imino group, etc., instead of the phenolic hydroxyl group, having a solubility in methanol within the above range. Like the polymer, there is a possibility of exhibiting methanol permeation suppression in the polymer electrolyte membrane.

  The phenol aralkyl resin that can be suitably used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in the present invention is a group having a phenolic hydroxyl group, that is, a hydroxyl group bonded to an aromatic group. A resin in which a group and an aralkyl group, that is, a group composed of an aromatic group and a non-aromatic hydrocarbon group, are combined to form a main structural unit. The group having a phenolic hydroxyl group is not limited to phenol, phenol derivatives such as cresol, ethylphenol, propylphenol, butylphenol, bisphenol A, bisphenol S, bisphenol B, bisphenol H, biphenol, and their Groups derived from polyphenol compounds such as derivatives and naphthol compounds such as naphthol and naphthdiol are also included. The aralkyl group represents a group having two methylene groups which may have a substituent with respect to the aromatic group, and a xylidene group, α, α′-dimethylxylidene group, a naphthalene derivative having a methylene group, Examples thereof include, but are not limited to, biphenyl derivatives having a methylene group.

  The phenol aralkyl resin can be obtained by subjecting the compound having a phenolic hydroxyl group and an aralkyl group compound to a condensation reaction. For example, with respect to a compound having a phenolic hydroxyl group, an aromatic divinyl compound, an aromatic compound having a vinyl group and a halomethyl group, a bis (halomethyl) aromatic compound, a bis (methoxymethyl) aromatic compound, (Hydroxymethyl) aromatic compounds such as toluenesulfonic acid, hydrochloric acid, sulfuric acid, oxalic acid, phosphoric acid, maleic acid, etc., aluminum chloride, stannous chloride, zinc chloride, boron trifluoride etherate, It can be obtained by reacting in the presence of a Friedel-Crafts catalyst such as dimethyl sulfate. The reaction temperature can be appropriately selected between 30 and 150 ° C. according to the type of raw material and the degree of polymerization. The amount of the catalyst can be appropriately selected between 0.001 to 5% by weight, depending on the type of catalyst, the reaction temperature, and the raw material. The raw material may be reacted in a molten state, or may be carried out in a solvent such as diethyl ketone, methyl ethyl ketone, N, N-dimethylacetamide, N-methyl-2-pyrrolidone.

  For a compound having a phenolic hydroxyl group, the vinyl group undergoes addition polymerization at the α-position with respect to the benzene ring of the compound having a phenolic hydroxyl group. Further, halomethyl groups such as chloromethyl groups are polymerized by eliminating HCl, methoxymethyl groups methanol, and hydroxymethyl groups water. Examples of the method for producing such a phenol aralkyl resin include, for example, Japanese Patent Publication No. 47-6510, Japanese Patent Publication No. 48-10960, Japanese Patent Publication No. 61-212284, Japanese Patent Publication No. 61-296024, Japanese Patent Publication No. 63-238129, JP-A-5-78457, and JP-A-2000-53740. The resin composition after the reaction may be used as it is, or may be used after removing unreacted substances, oligomers, modified monomers, etc. by distillation under reduced pressure or reprecipitation, or diethyl ketone, methyl ethyl ketone, N, N -You may melt | dissolve and use in suitable solvents, such as a dimethylacetamide and N-methyl-2- pyrrolidone.

  The phenol cycloalkyl resin which can be suitably used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in the present invention is a group having a phenolic hydroxyl group, that is, a hydroxyl group bonded to an aromatic group. And a cycloalkyl group bonded to each other to form a main structural unit. The group having a phenolic hydroxyl group is not limited to phenol, phenol derivatives such as cresol, ethylphenol, propylphenol, butylphenol, bisphenol A, bisphenol S, bisphenol B, bisphenol H, biphenol, and their Groups derived from polyphenol compounds such as derivatives and naphthol compounds such as naphthol and naphthdiol are also included. Examples of the cycloalkyl group include a cyclobutane group, a cyclopentyl group, a cyclohexyl group, a dicycloheptane group, a dicyclononane group, and a tricyclodecyl group.

  The phenol cycloalkyl resin can be obtained by subjecting the compound having a phenolic hydroxyl group and a cycloalkyl group compound to a condensation reaction. For example, for a compound having a phenolic hydroxyl group, dicyclopentadiene, cycloterpene, pinene, cyclobutadiene, cyclopentadiene, cyclohexadiene, dicycloheptadiene, dicyclononadiene, divinyl cycloalkyl compound, vinyl group and A cycloalkyl compound having a halomethyl group, a bis (halomethyl) cycloalkyl compound, a bis (methoxymethyl) cycloalkyl compound, a bis (hydroxymethyl) cycloalkyl compound, etc., are added with toluenesulfonic acid, hydrochloric acid, sulfuric acid, oxalic acid, It can be obtained by reacting in the presence of an acidic substance such as phosphoric acid or maleic acid, or a Friedel-Crafts catalyst such as aluminum chloride, stannous chloride, zinc chloride, boron trifluoride etherate or dimethyl sulfate. The reaction temperature can be appropriately selected between 30 and 150 ° C. according to the type of raw material and the degree of polymerization. The amount of the catalyst can be appropriately selected between 0.001 to 5% by weight, depending on the type of catalyst, the reaction temperature, and the raw material. The raw material may be reacted in a molten state, or may be carried out in a solvent such as diethyl ketone, methyl ethyl ketone, N, N-dimethylacetamide, N-methyl-2-pyrrolidone. For a compound having a phenolic hydroxyl group, the vinyl group undergoes addition polymerization at the α-position with respect to the benzene ring of the compound having a phenolic hydroxyl group. Further, halomethyl groups such as chloromethyl groups are polymerized by eliminating HCl, methoxymethyl groups methanol, and hydroxymethyl groups water. A method for producing such a phenol aralkyl resin is described in, for example, US Pat. No. 3,536,734. The resin composition after the reaction may be used as it is, or may be used after removing unreacted substances, oligomers, modified monomers, etc. by distillation under reduced pressure or reprecipitation, or diethyl ketone, methyl ethyl ketone, N, N -You may melt | dissolve and use in suitable solvents, such as a dimethylacetamide and N-methyl-2- pyrrolidone.

  The phenol aralkyl resin and the phenol cycloalkyl resin preferably have a molecular weight of 100 to 1,000,000. More preferably, it is between 200 and 500,000. The ratio of the weight average molecular weight to the number average molecular weight is more preferably between 10 and 100. The resin is preferably a substantially linear polymer. If the resin has a large number of branched structures or a network structure, the miscibility with the proton conductive polymer (a) may be lowered. The resin is dissolved in a solvent capable of dissolving a general proton conductive polymer such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and diphenyl sulfone. It is preferable to be able to do so because it can be mixed in a solution. When the proton conductive polymer (a) and the resin are not mixed in the same solvent, they can be mixed in a molten state.

  The phenol aralkyl resin and the phenol cycloalkyl resin preferably have a solubility in methanol at 25 ° C. of 10% by weight or less, and more preferably 1% by weight or less. If the solubility in methanol is large, the methanol permeation suppression performance may be reduced. The amount of the resin relative to the polymer electrolyte membrane is preferably 2 to 50% by weight, and more preferably 2 to 20% by weight. If the amount of the resin is less than 2% by weight based on the proton conductive polymer, the effect of suppressing methanol permeation may not be obtained sufficiently, which is not preferable. On the other hand, if it exceeds 100% by weight, the mechanical properties of the polymer electrolyte membrane may deteriorate, which is not preferable. The content of the resin can be analyzed by an extraction method, an NMR method, or the like.

  The phenol aralkyl resin and the phenol cycloalkyl resin preferably have a phenolic hydroxyl group content in the range of 1 to 10 mmol / g, more preferably 1 to 7.5 mmol / g, still more preferably 2 to 6 mmol / g, particularly Preferably, it is the range of 2.5-5 mmol / g. When the amount of the phenolic hydroxyl group is less than 1 mmol / g, the mixing property with the proton conductive polymer is lowered, and there may be a problem in uniformity as a polymer electrolyte membrane. When the amount of the phenolic hydroxyl group exceeds 7.5 mmol / g, the methanol permeation suppressing effect may not be sufficiently obtained, which is not preferable. The amount of the phenolic hydroxyl group can be quantified by an arbitrary method such as an NMR method, a hydroxyl group quantification method using an acid anhydride, or an oxidation-reduction titration method. The polymer electrolyte membrane can be analyzed as it is or after the resin is extracted.

  A polymer (phenolic hydroxyl group-containing resin) containing a phenolic hydroxyl group-containing compound, such as a phenol aralkyl resin, a phenol cycloalkyl resin, and an alkylphenol resin, has a phenolic hydroxyl group substantially different from an acidic group of a proton conductive polymer. It is preferable that no bond is formed. Whether or not a bond is formed can be determined by performing IR measurement or NMR measurement on the polymer electrolyte membrane and confirming the presence or absence of a free hydroxyl group. If the peak or signal derived from OH detected by the resin alone is also detected for the polymer electrolyte membrane, it indicates that no bond is formed. In addition, the ion exchange capacity of the polymer electrolyte membrane is measured, and it can be determined whether there is a difference between the theoretical amount (the amount of proton conductive polymer contained in the polymer electrolyte membrane) and the actual measurement value. If the theoretical amount and the actually measured value are equivalent, it can be determined that there is no coupling. It can also be judged by observing whether or not the polymer electrolyte membrane is dissolved in a solvent capable of dissolving the proton conductive polymer (a). If the polymer electrolyte membrane dissolves satisfactorily, it can be determined that there is no bond. If the polymer electrolyte membrane does not dissolve and only swells or remains partially gelled, it can be determined that there is a bond. it can. Such a polymer electrolyte membrane can be obtained by using the above-described method for producing a polymer electrolyte membrane of the present invention.

  As the organic compound (b) having a proton conductivity of 0.1 mS / cm or less according to the present invention, the phenol aralkyl resin can have higher methanol permeability suppression performance than the phenol cycloalkyl resin. This is preferable. In the present invention, the mechanism by which the phenol aralkyl resin, phenol cycloalkyl resin and alkyl phenol resin suppress the methanol permeability of the polymer electrolyte membrane is not clear, but it is simply a compound having a phenolic hydroxyl group (for example, poly (4-hydroxylstyrene). ) And phenolic antioxidants), such as a phenol aralkyl resin, an alkylphenol resin, or a phenolcycloalkyl resin, since there is no significant permeation suppression effect, a hydrophobic alkyl group, an aralkyl group, or Since the cycloalkyl group suppresses methanol permeation and the phenolic hydroxyl group, which is a polar group, increases the mixing property with the proton conductive polymer, the mixing property between the proton conductive polymer (a) and the resin is ensured. It is guessed that it is for this purpose. Furthermore, it is surmised that the particulate phase separation structure contributes to methanol permeation suppression.

  Among the raw materials for producing the phenol aralkyl resin and phenol cycloalkyl resin used as the organic compound (b) having proton conductivity of 0.1 mS / cm or less in the present invention, examples of the compound having a phenolic hydroxyl group are as follows: Although the following compounds can be exemplified, the present invention is not limited to these compounds, and any compound can be used as long as it can synthesize a phenol aralkyl resin and a phenol cycloalkyl resin that meet the above conditions.

  For example, phenol, p-cresol, o-cresol, p-ethylphenol, p-tertiary butylphenol, 2,4-dimethylphenol, 4-phenoxyphenol, 4-phenylphenol, 4,4-biphenol, 3,3 ′ -Dimethyl-4,4-biphenol, 3,3 ', 5,5'-tetramethyl-4,4-biphenol, 4,4'-oxydiphenol, 4,4'-thiobisphenol, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis ( 4-hydroxyphenyl) hexafluoropropane, bis (4-hydroxyphenyl) methane, 9,9-bis (4-hydro) Ciphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4 -Hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) ketone, 1,3-bis (4-hydroxyphenyl) ) Adamantane, 2,2-bis (4-hydroxyphenyl) adamantane 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,2′-dihexyl-4,4′-dihydroxybiphenyl, naphthol, naphtho Examples include diols.

  In order to produce a phenol aralkyl resin used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in the present invention, the following compound is used as a compound to be reacted with a compound having a phenolic hydroxyl group. Although not limited thereto, any compound can be used as long as it can synthesize a phenol aralkyl resin that meets the above conditions.

  For example, p-divinylbenzene, o-divinylbenzene, a mixture of p-divinylbenzene and o-divinylbenzene, divinylnaphthalene, divinylbiphenol, divinylanthracene, 1,4-bis (methoxymethyl) benzene, 1,3-bis ( Methoxymethyl) benzene, bis (methoxymethyl) naphthalene, 4,4′-bis (methoxymethyl) biphenyl, bis (methoxymethyl) anthracene, 1,4-bis (chloromethyl) benzene, 1,4-bis (bromomethyl) Benzene, 1,4-bis (fluoromethyl) benzene, 1,4-bis (iodomethyl) benzene, 1,3-bis (chloromethyl) benzene, 1,3-bis (bromomethyl) benzene, 1,3-bis ( Fluoromethyl) benzene, 1,3-bis (iodomethyl) benze Bis (chloromethyl) naphthalene, bis (bromomethyl) naphthalene, bis (fluoromethyl) naphthalene, bis (iodomethyl) naphthalene, bis (chloromethyl) anthracene, bis (bromomethyl) anthracene, bis (fluoromethyl) anthracene, bis (iodomethyl) ) Anthracene, bis (chloromethyl) tetraphenylmethane, bis (bromomethyl) tetraphenylmethane, bis (fluoromethyl) tetraphenylmethane, bis (iodomethyl) tetraphenylmethane, 4,4 ′-(chloromethyl) biphenyl, 4, 4 '-(bromomethyl) biphenyl, 4,4'-(fluoromethyl) biphenyl, 4,4 '-(iodomethyl) biphenyl, 1,4-bis (hydroxymethyl) benzene, 1,3-bis (hydroxymethyl) ) Benzene, bis (hydroxymethyl) naphthalene, bis (hydroxymethyl) anthracene, 4,4-bis (hydroxymethyl) biphenyl, bis (hydroxymethyl) tetraphenylmethane, 4-fluoromethylstyrene, 4-chloromethylstyrene, 4 -Bromomethylstyrene, 4-iodomethylstyrene, 3-fluoromethylstyrene, 3-chloromethylstyrene, 3-bromomethylstyrene, 4-hydroxymethylstyrene, 3-hydroxymethylstyrene and the like can be mentioned.

  In order to produce the phenol cycloalkyl resin used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in the present invention, the following compound is used as the compound to be reacted with the compound having a phenolic hydroxyl group. However, the present invention is not limited thereto, and any compound can be used as long as it can synthesize a phenol cycloalkyl resin that meets the above conditions.

  For example, 2,4-dimethyl-1,4-cyclobutadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene, dicyclopentadiene, cycloterpene, pinene, dicycloheptadiene, dicyclononadiene, bis ( Chloromethyl) cyclohexane, bis (hydroxymethyl) cyclohexane, and divinylcyclohexane.

  Examples of the alkylphenol resin used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less in the present invention include o- or p-cresol novolak resin, dimethylphenol novolak resin, tertiary butylphenol novolak resin, Examples thereof include cresol resol resins. The cresol novolac resin can be obtained, for example, by dehydrating condensation by heating o- or p-cresol and formaldehyde in the presence of an acidic catalyst. The alkylphenol resin can be obtained by reacting a phenol derivative having an alkyl group as a substituent with a condensing agent such as formaldehyde. In addition, a basic catalyst such as sodium hydroxide can be used for the reaction with the condensing agent, but if the reaction proceeds too much, the crosslinking reaction proceeds and it may become difficult to handle such as insolubilization in a solvent. It is not preferable. It is preferably a substantially linear polymer using an acidic catalyst. As alkyl-substituted phenols for obtaining alkylphenol resins, o-cresol, p-cresol, m-cresol, dimethylphenol, trimethylphenol, ethylphenol, diethylphenol, triethylphenol, propylphenol, isopropylphenol, butylphenol, tertiary Examples include but are not limited to butylphenol. Examples of the condensing agent to be reacted with the alkyl-substituted phenol include, but are not limited to, formaldehyde and hexamethylenetetramine. Examples of the acidic compound used for the catalyst include strong acids such as hydrochloric acid, sulfuric acid, toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, phosphoric acid, alkylphosphonic acid, and vinylphosphonic acid. The alkyl-substituted phenol, the condensing agent, and the catalyst can be reacted by heating under reflux conditions in the presence or absence of a solvent such as methyl ethyl ketone, cyclohexanone, diethyl ketone, tetrahydrofuran, or dioxane. Unreacted compounds and solvents can be removed by reprecipitation, dialysis, distillation, vacuum distillation or the like. It is preferable to remove unreacted compounds as much as possible.

  In the present invention, as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less, a substituted phenol resin such as an aralkyl group-substituted phenol resin, a phenyl group-substituted phenol resin, or a phenoxy group-substituted phenol resin is used as an aralkyl group. It can be obtained by reacting a substituted phenol such as a substituted phenol, a phenyl group-substituted phenol, or a phenoxy group-substituted phenol with a condensing agent such as formaldehyde. These resins can be synthesized in the same manner as the above alkyl-substituted phenol resins. Examples of the phenol compound that can be used as a raw material include 2- (4-hydroxyphenyl) -2-phenylpropane, methylphenylphenol, phenylphenol (hydroxybiphenyl), and phenoxyphenol (hydroxydiphenyl ether). It is not limited to.

  In the present invention, the phenol aralkyl resin and phenol cycloalkyl resin used as the organic compound (b) having a proton conductivity of 0.1 mS / cm or less are reacted with an excess of a compound having a phenolic hydroxyl group, and the terminal is phenolic. An oligomer which is a compound having a hydroxyl group can also be produced by dehydration condensation with a dialdehyde compound such as formaldehyde.

  The polymer electrolyte membrane of the present invention preferably has an ion exchange capacity of 0.1 to 3.0 meq / g, and more preferably has an ion exchange capacity of 0.5 to 2.0 meq / g. Furthermore, it is more preferable to have an ion exchange capacity of 0.5 to 1.5 meq / g, and it is more preferable to have an ion exchange capacity of 0.7 to 1.3 meq / g.

  The polymer electrolyte membrane of the present invention can have any thickness, but if it is less than 10 μm, it may be difficult to satisfy predetermined characteristics, and therefore it is preferably 10 μm or more, and preferably 20 μm or more. Is more preferable. Moreover, since manufacture may become difficult when it exceeds 300 micrometers, it is preferable that it is 300 micrometers or less.

  The polymer electrolyte membrane of the present invention is a polyester such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, nylon 6, nylon 66, nylon 610, nylon 12 and the like, as long as the specified higher order structure is not hindered. Polyamides, polymethyl methacrylate, polymethacrylic acid esters, polymethyl acrylates, polyacrylic acid esters and other acrylate resins, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, polystyrene and diene polymers Including various polyolefins, polyurethane resins, cellulose resins such as cellulose acetate and ethyl cellulose, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene Includes aromatic polymers such as side, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, benzoxazine resin, etc. May be. In addition, an organic or inorganic compound having a flat plate shape or a fiber shape may be included as long as the higher order structure can be maintained. A porous membrane may be used as a reinforcing material.

  In order to produce the polymer electrolyte membrane of the present invention, as described above, a solution composition comprising a proton conductive polymer (a) and an organic compound (b) having a proton conductivity of 0.1 mS / cm or less is used. It is preferable to use it. Solvents that can be used in the solution composition include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphonamide, N- Examples include, but are not limited to, aprotic organic polar solvents such as morpholine oxide. Among these, N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone are preferable, and N-methyl-2-pyrrolidone is more preferable.

  The concentration of the proton conductive polymer in the solution composition is preferably in the range of 0.1 to 50% by weight, more preferably in the range of 5 to 50% by weight, and still more preferably in the range of 10 to 40% by weight.

  The thickness of the solution composition at the time of casting is not particularly limited, but is preferably 10 to 2000 μm. More preferably, it is 50-1500 micrometers. When the thickness of the solution composition is less than 10 μm, the form as a polymer electrolyte membrane tends not to be maintained, and when it is more than 2000 μm, a non-uniform film tends to be easily formed. A known method can be used as a method for controlling the cast thickness of the solution composition. For example, the thickness can be controlled by the amount and concentration of the solution by making the thickness constant using an applicator, a doctor blade or the like, or making the cast area constant using a glass petri dish or the like. The cast solution composition can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, the evaporation rate can be reduced by lowering the temperature in the first stage.

Furthermore, the method for producing the polymer electrolyte membrane of the present invention is preferably the following method. That is, the proton conductive polymer (a) having a proton conductivity in water at 25 ° C. of 1 mS / cm or more forms a salt with a cation, and the proton conductivity in water at 25 ° C. is 0. A solution composition containing an organic compound (b) of 1 mS / cm or less and a solvent having a boiling point of 300 ° C. or less as essential components is cast on a substrate, and the amount of solvent is changed to a solid content by heating. The solvent is evaporated to 40% by weight or less to form a self-supporting film in which at least a part of the organic compound (b) is phase-separated and dispersed in the film, and then treated with an acid. This is a method for producing a polymer electrolyte membrane. The organic compound (b) is preferably a polymer having a ratio of the weight average molecular weight to the number average molecular weight of 10 to 100.
According to these production methods, the higher order structure of the membrane can be appropriately adjusted to a desired phase separation structure, and a membrane having a small compositional difference or structural difference between the membrane surface and the inner layer can be produced. Methanol permeability of the membrane can be suppressed.

  The membrane / electrode assembly of the present invention can be obtained by bonding the polymer electrolyte membrane of the present invention to an electrode catalyst layer. As a manufacturing method of this joined body, it can be performed using a conventionally known method, for example, a method of applying an adhesive on the electrode surface and bonding the polymer electrolyte membrane and the electrode, a polymer electrolyte membrane, A method of heating and pressing an electrode catalyst layer prepared by applying a paste containing a catalyst to an electrode in advance, a method of attaching an electrode after transferring a catalyst layer prepared on another sheet to a polymer electrolyte membrane, There are methods such as, but not limited to, a method in which the surface of the molecular electrolyte membrane is coated with a dispersion containing a catalyst and conductive particles by spraying, printing, or the like, and then the electrodes are joined. As the adhesive, a known one such as a Nafion (registered trademark) solution may be used, or an adhesive composed mainly of the same polymer composition as the polymer constituting the proton conductive polymer (a) in the present invention is used. Alternatively, those containing other hydrocarbon proton conductive polymers as main components may be used. A catalyst such as platinum or platinum-ruthenium alloy necessary for the electrode reaction can be obtained by dispersing the catalyst supported on conductive particles such as carbon in the adhesive. .

  The fuel cell of the present invention can be produced using the polymer electrolyte membrane or the membrane / electrode assembly of the present invention. The fuel cell of the present invention includes, for example, an oxygen electrode, a fuel electrode, a polymer electrolyte membrane sandwiched between the electrodes, an oxidant flow path provided on the oxygen electrode side, and a fuel electrode side. The fuel flow path is provided. A fuel cell stack can be obtained by connecting such unit cells with a conductive separator.

  The polymer electrolyte membrane of the present invention is suitable for a polymer electrolyte fuel cell. The polymer electrolyte membrane of the present invention is particularly suitable for direct methanol fuel cells, dimethyl ether fuel cells, formic acid fuel cells, direct ethanol fuel cells and the like because of its low permeability for liquid fuels such as methanol. Since the permeability of the fuel is small, a high output can be obtained with little voltage drop due to the permeated fuel, and a high concentration fuel solution can be used. In addition, the amount of fuel that is wasted is reduced due to the permeation, so that the capacity can be improved and the energy efficiency can be increased.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

<Observation of higher-order structures in the film>
The polymer electrolyte membrane was cut into small pieces and embedded with an epoxy resin to prepare ultrathin sections. This was scraped onto a TEM observation mesh, dyed with ruthenium oxide, and then subjected to carbon vapor deposition to obtain an observation sample. Bright field observation was performed with a JEM2010 transmission electron microscope manufactured by JEOL Ltd., and the higher order structure in the film was observed. In the obtained image, the portion that appears dark is the proton conductive polymer (because the affinity between the acidic group and ruthenium oxide in the proton conductive polymer is high). Read from the image. The average particle diameter of the particles was obtained by subjecting the image to an image analysis apparatus to obtain the number average particle diameter. When the particles were elliptical, the average particle size was determined using the average value of the short and long axes as the particle size.

<Composition distribution in the film>
Measurement apparatus: Fourier transform infrared spectrophotometer FT-IR FTS7000e / UMA600 (manufactured by Varian Technologies Japan Limited) was used, and an infrared absorption spectrum method by a microscopic ATR method was adopted. The crystal was a Ge crystal, and the measurement was performed at an incident angle of 30 °. Both background measurement and sample measurement were performed after the sample chamber was sufficiently purged with nitrogen.
-Preparation of measurement sample: About the film | membrane surface, it measured on both surfaces as it was. About the inside, it cut | disconnected in the film surface direction in the center of the thickness direction using the razor, the inner surface was exposed, and it measured with respect to the surface. Measurements were made on a surface about 20 μm square.
Composition ratio of proton conductive polymer (a) and organic compound (b) having proton conductivity of 0.1 mS or less: characteristic absorption of proton conductive polymer (a) (chemical formulas (6A), (8A), (8B ) And (8C) in the polymer having the structure represented by (889), the absorption at 1489 cm ⁻¹ ) of the organic compound (b) having a proton conductivity of 0.1 mS / cm or less (chemical formula (7A), (7B) In the compound represented by the formula, the absorbance ratio at 1511 cm ⁻¹ ) was obtained.
-Display of composition distribution: The ratio of the composition ratio of the film surface (average value on both surfaces) to the composition ratio inside the film determined above was calculated and used as an index of the composition distribution state.

<Measurement of softening temperature of polymer electrolyte membrane>
Using a Rheogel-E4000 manufactured by UBM, a storage electrolyte modulus (E ′) and a loss modulus (E) in a tensile mode of a polymer electrolyte membrane having a width of 5 mm while being heated from room temperature to 250 ° C. at 2 ° C./min. ”) Was measured. Tan δ was determined as the ratio of the loss elastic modulus (E ″) to the storage elastic modulus (E ′). The softening temperature was determined as the temperature at the intersection of tangents before and after the inflection point where the storage elastic modulus was large and the value decreased.

<Logarithmic viscosity>
The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dL, the viscosity was measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / c was evaluated. (Ta is the drop time of the sample solution, tb is the drop time of the solvent only, and c is the polymer concentration).

<Proton conductivity>
A platinum wire (diameter: 0.2 mm) is pressed against the surface of the strip-shaped membrane sample on a probe for self-made measurement (made of tetrafluoroethylene resin), and the sample with a width of 1 cm is held in pure water at 25 ° C. The impedance between them was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. Conductivity in which the contact resistance between the film and the platinum wire was canceled by the following formula from the gradient in which the distance between the electrodes was changed at intervals of 0.5 cm and the measured resistance value estimated from the distance between the electrodes and the CC plot was plotted. The rate was calculated.
Conductivity [S / cm] = 1 / film width [cm] × film thickness [cm] × resistance interelectrode gradient [Ω / cm]

<Power generation evaluation of direct methanol fuel cell (DMFC)>
After adding a small amount of ultrapure water and isopropyl alcohol to Pt / Ru catalyst-supporting carbon (TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and moistening, a 20% Nafion (registered trademark) solution (product number: SE-20192) manufactured by DuPont The Pt / Ru catalyst-carrying carbon and Nafion were added at a weight ratio of 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. The catalyst paste is applied and dried by screen printing on carbon paper TGPH-060 manufactured by Toray Industries, Inc. as a gas diffusion layer so that the amount of platinum deposited is 2 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for the anode. did. Further, after adding a small amount of ultrapure water and isopropyl alcohol to a Pt catalyst-supporting carbon (TEC10V40E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) Then, the Pt catalyst-carrying carbon and Nafion were added in a weight ratio of 2.5: 1 and stirred to prepare a cathode catalyst paste. The catalyst paste was applied and dried on carbon paper TGPH-060 manufactured by Toray Industries, Ltd., which had been subjected to water repellent treatment, so that the amount of platinum deposited was 1 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for cathode. . By sandwiching the membrane sample between the two types of carbon paper with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, by applying pressure and heating at 165 ° C. and 8 MPa for 3 minutes by a hot press method, A membrane-electrode assembly was obtained. This joined body was incorporated into an evaluation fuel cell FC25-02SP manufactured by Electrochem, and a power generation test was performed using a fuel cell power generation tester (manufactured by Toyo Corporation). Power generation is performed at a cell temperature of 40 ° C., a 5 mol / L methanol aqueous solution (1.5 mL / min) adjusted to 40 ° C. at the anode, and high-purity air gas (80 mL / min) adjusted to 40 ° C. at the cathode, respectively. The output voltage at a current density of 0.05 A / cm ² was measured.

<Ion exchange capacity>
A sample dried at 110 ° C. for 1 hour and allowed to stand overnight at room temperature in a nitrogen atmosphere was weighed, stirred with an aqueous sodium hydroxide solution, and then ion exchange capacity was determined by back titration with an aqueous hydrochloric acid solution.

<Measurement of solubility in N-methyl-2-pyrrolidone>
2 g of the target compound was mixed with 8 g of N-methyl-2-pyrrolidone and stirred at 25 ° C. for 3 hours using a magnetic stirrer. When dissolved, the solubility was judged to be 20% by weight or more. When an undissolved substance was present, the solution was suction filtered with a G3 glass filter, the weight of the solid content separated by filtration was measured, the weight of the dissolved solid content was determined, and the solubility was calculated.

<Measurement of solubility in methanol>
1 g of the target compound was mixed with 99 g of N-methyl-2-pyrrolidone, and stirred at 25 ° C. for 3 hours using a magnetic stirrer. When dissolved, the solubility was judged to be 1% by weight or more. When an undissolved substance was present, the solution was suction filtered with a G3 glass filter, the weight of the solid content separated by filtration was measured, the weight of the dissolved solid content was determined, and the solubility was calculated.

<Methanol permeation rate>
The liquid fuel permeation rate of the polymer electrolyte membrane was measured as the methanol permeation rate by the following method. A polymer electrolyte membrane immersed in a 5M (mol / liter) aqueous methanol solution adjusted to 20 ° C. for 24 hours is sandwiched between H-type cells, 100 ml of 5M aqueous methanol solution is placed on one side of the cell, and 100 ml of ultrapure water is placed on the other cell. (18 MΩ · cm) was injected, and the amount of methanol diffusing into the ultrapure water through the polymer electrolyte membrane was calculated by gas chromatography while stirring the cells on both sides at 20 ° C. ( The area of the polymer electrolyte membrane is 2.0 cm ² ).

<Methanol permeability coefficient>
It calculated | required by the following formula | equation from the methanol permeation rate and film thickness which were measured by said method.
Methanol permeability coefficient [μmol · m ⁻¹ · sec ⁻¹ ]
= Methanol permeation rate [mmol · m ⁻² · sec ⁻¹ ] × film thickness [μm] × 1000

<Example 1>
9 g of a polymer having a structure represented by the following general formula (6A) (logarithmic viscosity: 1.13 dL / g), represented by the following general formula (7A) as an organic compound (b) having a proton conductivity of 0.1 mS / cm or less 1 g of a compound to be obtained (polystyrene-equivalent number average molecular weight determined by GPC method is 800, weight average molecular weight is 25000) and N-methyl-2-pyrrolidone 30 g are put into a 100 mL glass flask, and 50% in a nitrogen atmosphere. Stir at 6 ° C. for 6 hours. The compound represented by the following general formula (7A) was insoluble in methanol, and the solubility in N-methyl-2-pyrrolidone was 1% by weight or more. The resulting solution was cast on a glass plate to a thickness of about 400 μm and heated in a hot air oven at 80 ° C. for 0.5 hours, 110 ° C. for 0.5 hours, and 130 ° C. for 0.5 hours to remove the solvent. After cooling, the film was peeled off to obtain a self-supporting film. The residual amount of N-methyl-2-pyrrolidone in the obtained film was 25% by weight based on the solid content. The obtained membrane was immersed in pure water at room temperature for 1 day, and then immersed twice in a 2 mol / L aqueous sulfuric acid solution for 1 hour. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

[In the formula (6A), one of the units surrounded by () in one [] and one of the units surrounded by () in the other [] are joined together. Y represents Na or K ion, respectively. The number on the right of () represents the molar ratio of each unit. Formula (7A) represents that the compound consists of four types of repeating structural units, and n, n ′, n ″, and n ′ ″ are 0.4 <(n + n ′) / (n ″. + N ′ ″) <0.6 represents an integer of 1 or more. ]

<Example 2>
9.5 g of polymer having a structure represented by the general formula (6A) (logarithmic viscosity: 1.13 dL / g), compound represented by the general formula (7A) (number in terms of polystyrene determined by GPC method) A polymer electrolyte membrane was prepared in the same manner as in Example 1 except that the amount of the average molecular weight was 800 and the weight average molecular weight was 25000) was changed to 0.5 g.

<Example 3>
The amount of the polymer having the structure represented by the general formula (6A) (logarithmic viscosity: 1.13 dL / g) is 8 g, and the compound represented by the general formula (7A) (number average molecular weight in terms of polystyrene determined by GPC method) The polymer electrolyte membrane was prepared in the same manner as in Example 1 except that the amount of 800 and the weight average molecular weight of 25000 was changed to 2 g.

<Example 4>
Instead of the compound represented by the general formula (7A) (the number average molecular weight in terms of polystyrene determined by GPC method is 800 and the weight average molecular weight is 25000), a compound having a structure represented by the following general formula (7B) ( A polymer electrolyte membrane was prepared in the same manner as in Example 1 except that the polystyrene-equivalent number average molecular weight obtained by GPC method was 700 and the weight average molecular weight was 28000). The compound represented by the following general formula (7B) was insoluble in methanol, and the solubility in N-methyl-2-pyrrolidone was 1% by weight or more.

[Formula (7B) represents that the compound consists of two types of repeating structural units, and n and n ′ are integers of 1 or more satisfying 0.4 <(n / n ′) <0.6 Represents. ]

<Comparative Example 1>
9 g of a polymer having a structure represented by the general formula (6A) (logarithmic viscosity: 1.13 dL / g), a compound represented by the general formula (7A) as an organic compound having a proton conductivity of 0.1 mS / cm or less (GPC 1 g of polystyrene-reduced number average molecular weight determined by the method is 800 and weight average molecular weight is 25000) and 30 g of N-methyl-2-pyrrolidone are put into a 100 mL glass flask and stirred at 50 ° C. for 6 hours in a nitrogen atmosphere. did. The resulting solution was cast on a glass plate to a thickness of about 400 μm, heated in a hot air oven at 80 ° C. for 0.5 hours to remove the solvent, and cooled. It was difficult to peel the film from the glass plate. The residual amount of N-methyl-2-pyrrolidone in the glass plate-like gel was 60% by weight based on the solid content. When the glass plate to which the gel-like material adhered was immersed in pure water at 25 ° C. and left for 1 day, the film peeled off. The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution twice for 1 hour each. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

<Comparative example 2>
9 g of a polymer having a structure represented by the general formula (6A) (logarithmic viscosity: 1.13 dL / g), a compound represented by the general formula (7A) as an organic compound having a proton conductivity of 0.1 mS / cm or less (GPC 1 g of polystyrene-reduced number average molecular weight determined by the method is 800 and weight average molecular weight is 25000) and 30 g of N-methyl-2-pyrrolidone are put into a 100 mL glass flask and stirred at 50 ° C. for 6 hours in a nitrogen atmosphere. did. The obtained solution was cast on a glass plate to a thickness of about 400 μm, immersed in pure water at 25 ° C. together with the glass plate, and allowed to stand for 1 day. As a result, the film peeled off. The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution twice for 1 hour each. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

<Comparative Example 3>
10 g of a polymer having a structure represented by the general formula (6A) (logarithmic viscosity: 1.13 dL / g) and 30 g of N-methyl-2-pyrrolidone were put into a 100 mL glass flask, and 6% at 50 ° C. in a nitrogen atmosphere. Stir for hours. The resulting solution was cast on a glass plate to a thickness of about 400 μm and heated in a hot air oven at 80 ° C. for 0.5 hours, 110 ° C. for 0.5 hours, and 130 ° C. for 0.5 hours to remove the solvent. After cooling, the film was peeled off to obtain a self-supporting film. The residual amount of N-methyl-2-pyrrolidone in the obtained film was 24% by weight based on the solid content. The obtained membrane was immersed in pure water at room temperature for 1 day, and then immersed twice in a 2 mol / L aqueous sulfuric acid solution for 1 hour. After that, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

<Comparative Example 4>
10 g of a polymer having a structure represented by the following general formula (8A) (logarithmic viscosity: 1.21 dL / g) and 30 g of N-methyl-2-pyrrolidone were put into a 100 mL glass flask, and at 50 ° C. in a nitrogen atmosphere. Stir for 6 hours. The resulting solution was cast on a glass plate to a thickness of about 400 μm and heated in a hot air oven at 80 ° C. for 0.5 hours, 110 ° C. for 0.5 hours, and 130 ° C. for 0.5 hours to remove the solvent. After cooling, the film was peeled off to obtain a self-supporting film. The residual amount of N-methyl-2-pyrrolidone in the obtained film was 26% by weight based on the solid content. The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution twice for 1 hour each. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

[In the formula (8A), one of the units surrounded by () in one [] and one of the units surrounded by () in the other [] are bonded to each other. Y represents Na or K ion, respectively. The number on the right of () represents the molar ratio of each unit. ]

<Comparative Example 5>
10 g of a polymer having a structure represented by the following general formula (8B) (logarithmic viscosity: 1.25 dL / g) and 30 g of N-methyl-2-pyrrolidone were put into a 100 mL glass flask, and the reaction was performed at 50 ° C. in a nitrogen atmosphere. Stir for 6 hours. The resulting solution was cast on a glass plate to a thickness of about 400 μm and heated in a hot air oven at 80 ° C. for 0.5 hours, 110 ° C. for 0.5 hours, and 130 ° C. for 0.5 hours to remove the solvent. After cooling, the film was peeled off to obtain a self-supporting film. The residual amount of N-methyl-2-pyrrolidone in the obtained film was 25% by weight based on the solid content. The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution twice for 1 hour each. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

[In the formula (8B), one of the units surrounded by () in one [] and one of the units surrounded by () in the other [] are bonded to each other. Y represents Na or K ion, respectively. The number on the right of () represents the molar ratio of each unit. ]

<Comparative Example 6>
10 g of a polymer having a structure represented by the following general formula (8C) (logarithmic viscosity: 1.19 dL / g) and 30 g of N-methyl-2-pyrrolidone were put into a 100 mL glass flask, and the reaction was performed at 50 ° C. in a nitrogen atmosphere. Stir for 6 hours. The resulting solution was cast on a glass plate to a thickness of about 400 μm and heated in a hot air oven at 80 ° C. for 0.5 hours, 110 ° C. for 0.5 hours, and 130 ° C. for 0.5 hours to remove the solvent. After cooling, the film was peeled off to obtain a self-supporting film. The residual amount of N-methyl-2-pyrrolidone in the obtained film was 27% by weight with respect to the solid content. The obtained film was immersed in pure water at room temperature for 1 day, and then immersed in a 2 mol / L sulfuric acid aqueous solution twice for 1 hour each. Thereafter, the film is washed with pure water until the washing water becomes neutral, the water adhering to the surface is removed with filter paper, both sides are sandwiched with new filter paper, and both sides are further sandwiched with a glass plate. A polymer electrolyte membrane was obtained by applying a load and leaving it in a room at 23 ° C. and a relative humidity of 50% for 2 days to dry.

[In the formula (8C), one of the units surrounded by () in one [] and one of the units surrounded by () in the other [] are bonded to each other. Y represents Na or K ion, respectively. The number on the right of () represents the molar ratio of each unit. ]

<Comparative Example 7>
The same procedure as in Example 1 was performed except that Irganox 1010 (manufactured by Ciba Specialty Chemicals), which is a phenolic antioxidant having a phenolic hydroxyl group, was used instead of the compound represented by the general formula (7A). A polymer electrolyte membrane was prepared and evaluated. 2 g of Irganox 1010 was dissolved in 98 g of methanol at 25 ° C., and the solubility was 2% by weight or more.

<Comparative Example 8>
A polymer electrolyte membrane was tried in the same manner as in Example 1 except that a xylene resin (average molecular weight 12000) was used in place of the compound represented by the general formula (7A). However, uneven thickness and defects occurred frequently. A polymer electrolyte membrane could not be obtained.

<Comparative Example 9>
A polymer electrolyte membrane (trade name: Nafion 117), which is a commercially available perfluorocarbon sulfonic acid polymer membrane, was evaluated.

  Various evaluation was performed about the polymer electrolyte membrane of the Example and the comparative example. The results are shown in Tables 1 and 2.

  The polymer electrolyte membranes of Examples 1 to 4 do not contain an organic compound (b) whose proton conductivity (in water at 25 ° C.) is 0.1 mS / cm or less. In comparison with proton conductivity, methanol permeability is suppressed to about 1/8 to 1/5, and methanol permeability can be suppressed without lowering proton conductivity. I understand that. In addition, the softening temperature of the polymer electrolyte membrane of the example is lower than the softening temperature of the polymer electrolyte membrane of Comparative Example 3 made of only the proton conductive polymer of the example. This supports that a part of the compound having the structure represented by the chemical formula (7A) or (7B) is contained in the matrix. Incidentally, when the melting point of the compound having the structure represented by the chemical formula (7A) or (7B) was measured using a melting point observation device, the flow started in the range of 110 to 150 ° C.

In addition, according to observation with a transmission electron microscope, a particulate phase separation structure was observed in each of the polymer electrolyte membranes of Examples 1 to 4. The polymer electrolyte membranes of Comparative Examples 1 and 2 having the same composition as in Example 1 and different film-forming methods were soaked in water at a stage where the amount of residual solvent was large, so that the membrane became porous, and a clear phase separation structure As it did not form, methanol permeability had increased. Moreover, from the composition analysis by the solid ATR method, it was confirmed that the composition ratio in the film was not significantly different.
Electricity generation evaluation was performed on the polymer electrolyte membrane of Example 1 and the polymer electrolyte membrane of Comparative Example 2, respectively. In the former, an output voltage of 0.33 V was obtained at 0.05 A / cm ² , whereas in the latter, the voltage suddenly decreased when current started to flow, and at 0.05 A / cm ² , the output voltage was obtained. I couldn't.
Furthermore, although the polymer electrolyte membrane of the present invention has a slightly higher membrane resistance than a polymer electrolyte membrane made of a commercially available perfluorocarbon sulfonic acid polymer, the methanol permeability is extremely low, and a direct methanol fuel cell. It can be seen that the polymer electrolyte membrane is suitable for use in the present invention.

  Moreover, the fact that the acidic group and the hydroxyl group of the proton conductive polymer do not interact as in the prior art means that the polymer electrolyte membranes of Examples 1 and 4 and the polymer of Comparative Example 5 having the same ion exchange capacity are used. It is clear from comparison with the electrolyte membrane, comparison between the polymer electrolyte membrane of Example 2 and the polymer electrolyte membrane of Comparative Example 4, and comparison of the polymer electrolyte membrane of Example 3 and the polymer electrolyte membrane of Comparative Example 6. . The polymer electrolyte membrane of Comparative Example 3 is a polymer electrolyte membrane consisting only of a proton conductive polymer having a structure represented by the chemical formula (6A). The polymer electrolyte membrane of Example 1 is a polymer obtained by adding 1 part by weight of a compound having a structure represented by the chemical formula (7A) to 9 parts by weight of a proton conductive polymer having a structure represented by the chemical formula (6A). It is an electrolyte membrane. That is, since the content of the proton conductive polymer in Example 1 is 90% by weight, the calculated ion exchange capacity is 1.04 meq / g (ion exchange capacity of the polymer electrolyte membrane of Comparative Example 3). 90%, that is, 0.94 meq / g. Since the ion exchange capacity of the polymer electrolyte membrane of Example 1 is 0.92 meq / g from Table 1, it agrees with the theoretical value. This indicates that the sulfonic acid group of the proton conductive polymer is not consumed by being bonded to the hydroxyl group. The same can be said for Examples 2 to 4. Further, the polymer electrolyte membranes of Comparative Examples 4 to 6 having only the proton conductive polymer and equivalent ion exchange capacity to the polymer electrolyte membranes of Examples 1 to 4 showed equivalent proton conductivity. Therefore, in the polymer electrolyte membranes of the examples, the sulfonic acid group exhibits proton conductivity without being influenced by the phenol aralkyl resin, indicating that there is no interaction. It can be inferred that this is due to a method in which the sulfonic acid groups of the proton conducting polymer are mixed in a salt state.

  The polymer electrolyte membrane of the present invention can remarkably suppress methanol permeability without increasing membrane resistance, so that it can be used in a direct methanol fuel cell to improve its output or to enable the use of high-concentration methanol. Can do. Furthermore, the polymer electrolyte membrane of the present invention can be particularly suitably used for fuel cells using liquids such as dimethyl ether and formic acid in addition to methanol. Furthermore, it can be used for any known application as a polymer electrolyte membrane, such as an electrolytic membrane and a separation membrane, and contributes greatly to the industrial world.

2 is a transmission electron micrograph of a cross section of the polymer electrolyte membrane obtained in Example 1. FIG. 4 is a transmission electron micrograph of a cross section of a polymer electrolyte membrane obtained in Example 3. FIG. FIG. 3 is a graph showing the temperature dependence of dynamic viscoelasticity (E ′, E ″, tan δ) of the polymer electrolyte membrane obtained in Example 1. FIG. 6 is a graph showing the temperature dependence of dynamic viscoelasticity (E ′, E ″, tan δ) of the polymer electrolyte membrane obtained in Comparative Example 3.

Claims (16)

  An organic compound having an acidic group and a proton conductive polymer (a) having a proton conductivity of 1 mS / cm or more in water at 25 ° C. and having a proton conductivity in water of 25 ° C. of 0.1 mS / cm or less. A polymer electrolyte membrane, wherein the compound (b) is phase-separated and dispersed in the form of particles having an average particle size of 0.01 to 10 μm.   The polymer according to claim 1, wherein the organic compound (b) has a solubility in methanol at 25 ° C of 1% by weight or less and a solubility in N-methyl-2-pyrrolidone at 25 ° C of 1% by weight or more. Electrolyte membrane.   The polymer electrolyte membrane according to claim 1, wherein the organic compound (b) is a compound having a molecular weight of 300 or more.   4. The polymer electrolyte membrane according to claim 1, wherein the content of the organic compound (b) in the polymer electrolyte membrane is 2 to 50% by weight.   The organic compound (b) is a polymer comprising at least one compound having at least one polar group selected from the group consisting of a hydroxyl group, an alkoxy group, a cyano group, and an amide group as a constituent component. The polymer electrolyte membrane according to any one of the above.   The polymer electrolyte membrane according to claim 5, wherein the polar group is a phenolic hydroxyl group.   The polymer electrolyte membrane according to claim 6, wherein the organic compound (b) is at least one resin selected from the group consisting of a phenol resin, an alkylphenol resin, a phenol aralkyl resin, and a phenol cycloalkyl resin.   The value of the membrane surface in the composition ratio of the organic compound (b) to the proton conductive polymer (a) in the polymer electrolyte membrane is in the range of 80 to 120% with respect to the value at the center of the membrane. The polymer electrolyte membrane according to any one of the above.   The high part according to any one of claims 1 to 8, wherein a part of the organic compound (b) is dissolved or reacted in a matrix composed of the proton conductive polymer (a), and the remainder is phase-separated and dispersed. Molecular electrolyte membrane.   The polymer electrolyte membrane according to any one of claims 1 to 9, wherein the organic compound (b) is a compound having a molecular weight distribution in which the ratio of the weight average molecular weight to the number average molecular weight is between 10 and 100.   The organic compound (b) formed by dissolving or reacting in the matrix made of the proton conductive polymer (a) is a low molecular weight component having a ratio of the weight average molecular weight to the number average molecular weight of 10 to 100. The polymer electrolyte membrane according to claim 9 or 10.   The glass transition temperature measured by the dynamic viscoelasticity method of the polymer electrolyte membrane is 5 ° C. or more lower than the glass transition temperature measured by the dynamic viscoelasticity method of the polymer electrolyte membrane consisting only of the proton conductive polymer (a). The polymer electrolyte membrane according to claim 1.   A membrane / electrode assembly using the polymer electrolyte membrane according to claim 1.   A fuel cell using the membrane / electrode assembly according to claim 13.   Polymer (c) in which the acidic group of the proton conductive polymer (a) having a proton conductivity in water at 25 ° C. of 1 mS / cm or more forms a salt with a cation, and the proton conductivity in water at 25 ° C. is 0.1 mS A solution composition containing an organic compound (b) having a boiling point of not more than / cm and a solvent having a boiling point of not more than 300 ° C. as an essential constituent is cast on a substrate, and the amount of solvent is reduced relative to the solid content by heating. The solvent is evaporated to 40 wt% or less to form a self-supporting membrane in which at least a part of the organic compound (b) is phase-dispersed and dispersed in the membrane, and then treated with an acid. Item 13. A method for producing a polymer electrolyte membrane according to any one of Items 1 to 12. The method for producing a polymer electrolyte membrane according to claim 15, wherein the organic compound (b) is a polymer having a ratio of a weight average molecular weight to a number average molecular weight of 10 to 100.