JP6779449B2 - Polymer electrolyte membrane and its use - Google Patents

Description

The present invention relates to a polymer electrolyte membrane suitable for a polymer electrolyte fuel cell, a membrane using the same, an electrode assembly, and a fuel cell containing these.

In recent years, from the viewpoint of environmental problems such as global warming, the development of highly efficient and clean energy sources has been required, and fuel cells are attracting attention as one of such energy sources. Among them, the development of a polymer electrolyte fuel cell using a polymer compound containing a proton conductive functional group for an electrolyte membrane is underway. In particular, a hydrocarbon-based electrolyte membrane in which a large number of sulfonic acid groups are introduced has high proton conductivity and is attracting attention as a material for polymer electrolyte fuel cells. This hydrocarbon-based electrolyte membrane is characterized in that it is easy to have a variety of chemical structures and the range of introduction of a proton conductive group such as a sulfonic acid group can be widely adjusted.

However, since the hydrocarbon-based electrolyte membrane containing a large amount of sulfonic acid groups has a large swelling rate, there is a problem that the electrolyte membrane is easily torn due to repeated water-containing and dry states under the operating conditions of the fuel cell. Patent Document 1 discloses a polymer electrolyte membrane reinforced with a glass non-woven fabric. It has been proposed that the swelling resistance of the electrolyte membrane is improved by combining the polymer electrolyte and the glass non-woven fabric.

WO2005 / 086265A1 Gazette

However, while the swelling resistance of the film is improved, the conventional technique tends to be brittle due to a decrease in elongation. Therefore, under the repeated stress of water content-drying, the film may be cracked and sufficient durability may not be exhibited.

The present invention exhibits high proton conductivity and high swelling resistance, and therefore has high mechanical durability even under repeated water-containing-drying conditions, and is a hydrocarbon system suitable for use as an electrolyte membrane for fuel cells. Provided is a polymer electrolyte membrane.

The polymer electrolyte membrane of the present invention is a polymer electrolyte membrane having a sulfonic acid group and a composite of a hydrocarbon-based electrolyte having a main chain mainly containing an aromatic ring and a reinforcing material, and the reinforcing material is glass. Ri nonwoven der comprising a mixture of fibers and organic fibers, the glass fibers, and an average fiber diameter of 1 [mu] m or less, an average fiber diameter of a mixture of of less than 10μm exceed 1 [mu] m, an average fiber diameter of 1 [mu] m The content of glass fibers exceeding and less than 10 μm is 10 to 70% by weight based on 100% by weight of the total of glass fibers having an average fiber diameter of 1 μm or less and glass fibers having an average fiber diameter of more than 1 μm and less than 10 μm. It is characterized by.

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

According to the present invention, by compounding a reinforcing material containing a mixture of glass fibers and organic fibers with a hydrocarbon-based polymer electrolyte, dimensional changes during water content can be suppressed, and dry / wet cycle resistance is high and low. It is possible to provide a polymer electrolyte membrane having high proton conductivity even under humidification. Further, by using this polymer electrolyte membrane, it is possible to provide a highly reliable fuel cell for long-term use because it has high performance regardless of the humidity of the fuel gas and is excellent in dry-wet cycle resistance.

FIG. 1 is a graph showing the proton conductivity of the polymer electrolyte membranes of Example 1 and Comparative Example 2 of the present invention.

As a result of diligent studies, the present inventors have made a composite film obtained by forming a specific reinforcing material, that is, a non-woven fabric made of a mixture of glass fibers and organic fibers together with an electrolyte resin, as compared with a film of an electrolyte resin alone. It has been found that it has excellent swelling resistance and exhibits higher durability even in a test for evaluating mechanical stability such as a repeated water-containing-drying test (dry-wet cycle test), and has completed the present invention.

The polymer electrolyte used in the present invention, that is, the polymer electrolyte composited with the reinforcing material is a hydrocarbon-based electrolyte having a sulfonic acid group and having a main chain mainly composed of an aromatic ring, and its structure is not particularly limited. Here, "the main chain mainly consists of an aromatic ring" means that the proportion of the portion derived from the aromatic ring in the molecular weight of the portion excluding the group connecting the aromatic rings is 70% or more. To do. Examples of such hydrocarbon-based polymers include polyethersulfone, polysulfone, polyetheretherketone, polyetherketoneketone, polyetherethersulfone, polyketone, polyimide, polybenzimidazole, polybenzoxazole, polyphenylene ether and the like. ..

The polymer electrolyte particularly preferably used in the present invention mainly comprises a hydrophobic portion segment having substantially no sulfonic acid group and a hydrophilic portion segment having a sulfonic acid group and having a main chain mainly composed of an aromatic ring. It has as a chain. By making the polymer electrolyte a copolymer type consisting of a hydrophilic part segment and a hydrophobic part segment, the proton conductivity of the polymer electrolyte under low humidification is improved.

The hydrophilic portion segment in the present invention has a sulfonic acid group and the main chain mainly consists of an aromatic ring. That is, the hydrophilic segment is a segment into which a sulfonic acid group is introduced. As described above, since the hydrophilic part segment has a sulfonic acid group, the proton conductivity of the polymer electrolyte is exhibited, and the main chain of the hydrophilic part segment is mainly composed of an aromatic ring, so that the polymer electrolyte is heat resistant and chemically. It will be excellent in durability.

Examples of the sulfonic acid group in the present invention include a sulfonic acid group, a sulfonate group, a sulfonic acid ester group, and the like. That is, the sulfonic acid group may be, for example, a salt such as sodium or potassium, or may be protected by an ester group such as neopentyl ester, methyl ester or propyl ester. In particular, during or after the synthesis of the oligomer to be the hydrophilic segment, it is often preferable that the oligomer has a protective group such as a salt or an ester, but the polymer electrolyte can be used as an electrolyte membrane of a fuel cell, for example. When it is used, it is often converted into a sulfonic acid group by immersing it in an aqueous solution of an inorganic acid or the like. Therefore, in the present invention, the sulfonic acid group includes a group having a protecting group such as a salt or an ester as long as it is a group that easily becomes a sulfonic acid group.

The amount of the sulfonic acid group is preferably 1 to 6 and more preferably 1 to 4 per repeating unit forming the hydrophilic segment. If the amount of the sulfonic acid group is larger than 6, the water solubility of the hydrophilic segment becomes high, and the handling during synthesis tends to be difficult. If the number is less than one, it tends to be difficult to develop sufficient proton conductivity.

In the hydrophilic portion segment in the present invention, the main chain is mainly composed of an aromatic ring.
Here, "the main chain is mainly composed of an aromatic ring" means that the molecular weight of the portion other than the linking group (ether group, thioether group, sulfone group, ketone group, sulfide group, etc.) of the main chain in the hydrophilic portion segment is 100%. If, it means that 70% or more of them are composed of aromatic rings.

Examples of the aromatic ring include aromatic heterocycles containing benzene, naphthalene, anthracene, biphenyl, sulfur, nitrogen and the like.

Specific examples of the hydrophilic segment include those containing at least one of the structures described in the following general formula group (1) as a repeating unit.

（式中、Ａｒ¹は、下記式群（２）に記載の構造を有する２価の基を表し、前記２価の基は置換基を有していてもよく、複数あるＡｒ¹は互いに同じであっても異なっていてもよい。Ａｒ²は、スルホン酸基を少なくとも１つ有する２価の芳香族基、ｎは１〜４の整数、Ｘは−Ｏ−又はＳ−、Ｙは直接結合、−ＳＯ₂−又はＣＯ−を表す。）
なお、上記一般式群（１）の繰り返し単位が複数回繰り返された場合、複数あるＡｒ¹は互いに同じであっても異なっていてもよい。

(Wherein, Ar ¹ represents a divalent group having a structure according to the following formula group (2), the divalent groups may have a substituent, a plurality of Ar ¹ are the same as each other Ar ² is a divalent aromatic group having at least one sulfonic acid group, n is an integer of 1 to 4, X is -O- or S-, and Y is a direct bond. , -SO _2- or CO-)
In the case where the repeating units of the general formula group (1) was repeated several times, a plurality of Ar ¹ may be different be the same as each other.

Further, Ar ² is a divalent aromatic group having the structure described in the following formula group (3) and having at least one sulfonic acid group, that is, described in the following formula group (3). A structure in which at least one sulfonic acid group is introduced into a divalent aromatic group having the above structure is preferable because synthesis is easy.

As a specific example of the hydrophilic segment, the structure described in the general formula group (1) may have a substituent on the benzene ring. Further, in Ar ¹ , the divalent group having the structure described in the formula group (2) may have a substituent. Further, in Ar ² , the divalent aromatic group having the structure described in the formula group (3) may have a substituent in addition to the sulfonic acid group. Examples of these substituents include an alkyl group having 1 to 6 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc.) and an alkoxy group having 1 to 6 carbon atoms (methoxy group, ethoxy group). Groups, propoxy groups, butoxy groups, pentyloxy groups, hexyloxy groups, etc.), phenyl groups and the like can be mentioned. In addition, it can have one or more of the substituents.

The hydrophilic portion segment has a sulfonic acid group, but the main chain, the side chain, or both (main chain and side chain) may have a sulfonic acid group.

Examples of the monomer constituting the hydrophilic segment include a monomer that can form the structure of the general formula group (1), and specifically, a monomer represented by the following formula is preferable. Further, in the case of producing a hydrophilic segment in which X is −S− in the above general formula group (1), in the monomer represented by the following formula, a monomer having a −SH group instead of the −OH group, or the like. Can also be mentioned. Further, as described later, when a hydrophilic part segment is produced by polymerizing a monomer having a sulfonic acid group, the monomer represented by the following formula has a sulfonic acid group on the benzene ring. And so on.

The ion exchange capacity of only the hydrophilic segment (hereinafter, the ion exchange capacity may be referred to as IEC) can be set high as the polymer electrolyte membrane, and can exhibit high proton conductivity under low humidification. From the point of view, 4.0 meq. It is preferably / g or more. The IEC of the hydrophilic part segment can be obtained by calculation by NMR analysis or by dividing the IEC of the electrolyte (which can be easily obtained by a conventionally known method such as titration) by the weight ratio of the hydrophilic part segment. However, in the present invention, it is obtained by the latter method. That is, the IEC of the hydrophilic portion segment is obtained by dividing the IEC of the polymer electrolyte obtained in the same manner as the method for measuring the IEC of the polymer electrolyte membrane described in the examples by the weight ratio of the hydrophilic portion segment. In addition, meq. / G means milliequivalent / g.

Examples of the monomer constituting the hydrophilic segment include those shown in JP-A-2002-293889 (monomers having an electron-withdrawing group and an electron-donating group, etc.).

The hydrophobic portion segment in the present invention has substantially no sulfonic acid group. As a result, the phase separation from the hydrophilic portion is clarified, the proton conductivity of the polymer electrolyte under low humidification is improved, and the strength of the polymer electrolyte is improved. It is preferable that no sulfonic acid group is introduced into the hydrophobic portion segment, but the hydrophobic portion segment may be relatively hydrophobic with respect to the hydrophilic portion segment, and the number of sulfonic acid groups per repeating unit is the hydrophilic portion segment. It may be 1/10 or less. That is, "substantially free of sulfonic acid groups" means that the hydrophobic portion segment has no sulfonic acid groups, or the number of sulfonic acid groups per repeating unit in the hydrophobic portion segment is the hydrophilic portion segment. It means that it is 1/10 or less of the number of sulfonic acid groups per repeating unit.

The hydrophobic portion segment is preferably a polyimide-based, polybenzimidazole-based, or polyether-based structure from the viewpoint of having heat resistance, and has a structure in which the main chain is mainly composed of an aromatic ring, and the polyether-based segment is easy to synthesize. More preferable from the viewpoint of Here, "the main chain mainly consists of an aromatic ring" means that the molecular weight of the portion other than the connecting group (ether group, sulfone group, ketone group, sulfide group, etc.) of the main chain in the hydrophobic portion segment is 100%. , 70% or more of which is composed of aromatic rings. As such a hydrophobic portion segment, it is preferable to include at least one of the structures described in the following general formula group (4) as a repeating unit.

（式中、Ａｒは、２価の芳香族基を表す。）

(In the formula, Ar represents a divalent aromatic group.)

When the repeating unit of the general formula group (4) is repeated a plurality of times, the plurality of Ars may be the same or different from each other. As the divalent aromatic group of Ar, for example, a group represented by the following formula (5) is preferably mentioned.

Further, the divalent aromatic group of Ar may have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc.) and an alkoxy group having 1 to 6 carbon atoms (methoxy group, ethoxy group). Groups, propoxy groups, butoxy groups, pentyloxy groups, hexyloxy groups, etc.), phenyl groups, cyano groups and the like can be mentioned. In addition, it can have one or more of the substituents.

Examples of the monomer constituting the hydrophobic portion segment include a monomer that can form the structure of the above general formula (4), and specifically, a monomer represented by the following formula is preferably mentioned.

The molecular weights of the hydrophilic portion segment and the hydrophobic portion segment differ depending on the chemical structure, ease of synthesis, etc., but the number average molecular weight is preferably 700 to 30,000 g / mol, more preferably 2000 to 10,000 g / mol, respectively. .. If it is less than 700 g / mol, the characteristics as a copolymer-type polymer electrolyte tend to be difficult to appear, and if it is larger than 30,000 g / mol, synthesis tends to be difficult due to problems such as solubility.

The molecular weight of the polymer electrolyte is preferably 10,000 to 300,000 g / mol in terms of number average molecular weight, and more preferably 30,000 to 150,000 g / mol from the viewpoint of the balance between ease of synthesis and solubility in a solvent. The molecular weight of each of the above segments and the polymer electrolyte can be determined by the measuring method described in Examples.

The ion exchange equivalent (IEC) of the polymer electrolyte is 1.5 to 3.5 meq. When it is / g, it is preferable because the performance as an electrolyte is easily exhibited, and 1.6 to 3.0 meq. / G is more preferable because it has an excellent balance between proton conductivity and mechanical strength under low humidification. The ion exchange capacity of the polymer electrolyte can be determined in the same manner as the method for measuring the ion exchange capacity of the polymer electrolyte membrane described in Examples.

Further, it is also within the scope of the present invention to carry out chemical modification such as introduction of crosslinks into the polymer electrolyte in order to further improve the mechanical strength and suppress swelling with respect to water.

The polymer electrolyte of the present invention can be produced by a conventionally known method. For example, after preparing an oligomer that becomes a hydrophilic part segment, the oligomer that becomes a hydrophobic part segment is copolymerized, and only the oligomer part that becomes a hydrophilic part of the copolymer is sulfonated, and the hydrophilic part-hydrophobic part co-weight. Method of coalescence; After preparing an oligomer that becomes a hydrophilic part segment, a sulfonic acid group is introduced to prepare a sulfonic acid group-containing oligomer, and this and an oligomer that becomes a hydrophobic part segment are copolymerized; a sulfonic acid group. A method in which an oligomer that becomes a hydrophilic part segment is produced by polymerization of a monomer having a hydrophobic part, and the oligomer that becomes a hydrophobic part segment is copolymerized; the oligomer that becomes a hydrophobic part segment and a large amount of monomer having a sulfonic acid group are polymerized. As a result, a method of forming a copolymer of a hydrophilic part segment and a hydrophobic part segment; and the like can be exemplified.

The method for producing a polymer electrolyte of the present invention will be described below with an example. The method for producing a polymer electrolyte of the present invention is not limited to the following.

First, using the above-mentioned monomer, an oligomer that becomes a hydrophilic part segment (oligomer containing a sulfone-oxidizable site) and an oligomer that becomes a hydrophobic part segment are prepared. To obtain these, a method of condensing a monomer having a nucleophilic substituent such as a hydroxyl group at the terminal and a monomer having a leaving group such as a halogen compound at the terminal, or a catalyst in the monomer having a leaving group is used. In addition, a method of condensation and the like can be mentioned.

The polymerization reaction (condensation reaction) can be carried out in a molten state without using a solvent, but it is preferably carried out in an appropriate solvent. Examples of the solvent include aromatic hydrocarbon solvents, halogen solvents, ether solvents, ketone solvents, amide solvents, sulfone solvents, sulfoxide solvents and the like. Examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene, 1,3,5-trimethylbenzene and the like. Examples of the halogen-based solvent include dichlorobenzene and trichlorobenzene. Examples of the ether solvent include tetrahydrofuran, dioxane, cyclopentyl methyl ether and the like. Examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone and the like. Examples of the amide solvent include N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone and the like. Examples of the sulfone solvent include sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane and the like. Examples of the sulfoxide solvent include dimethyl sulfoxide, diethyl sulfoxide and the like. These may be used alone or in combination of two or more.

A basic compound is usually used as a catalyst to accelerate the reaction. As the basic compound, alkali metal salts, alkaline earth metal salts and the like are preferably used, and for example, LiOH, NaOH, KOH, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , LiHCO ₃ , NaHCO ₃ , KHCO _3, etc.

The reaction temperature of the polymerization reaction step may be appropriately set according to the polymerization reaction. Specifically, it may be set to 20 ° C. to 250 ° C., which is the optimum range of use, and more preferably 40 ° C. to 200 ° C. If the temperature is lower than 20 ° C, the reaction tends to be slow, and if the temperature is higher than 250 ° C, the main chain tends to break easily. The reaction time of the polymerization reaction step is not particularly limited, but is preferably 0.1 to 500 hours, more preferably 0.5 to 300 hours.

As described above, after obtaining an oligomer that becomes a hydrophilic part segment and an oligomer that becomes a hydrophobic part segment, they are chemically bonded to form a block copolymer, thereby forming a copolymer (oligomer that becomes a hydrophilic part segment). And an oligomer that becomes a hydrophobic segment). The method of chemically bonding these oligomers to form a copolymer is not particularly limited, and can be appropriately determined depending on the reactivity of the oligomer to be polymerized. For the details of the polymerization method, a general method (“Polymer Synthesis and Reaction (2)” p.249-255, (1991) Kyoritsu Shuppan Co., Ltd.) can be applied. Specifically, for example, an oligomer having a nucleophilic substituent such as a hydroxyl group at the terminal is prepared, and an oligomer having a leaving group such as a halogen compound at the terminal prepared separately is condensed in the presence of a base. Make it a copolymer.

Alternatively, copolymerization can also be achieved by condensing each oligomer having a halogen compound at the terminal in the presence of a transition metal.

Next, in the copolymer obtained as described above, only the oligomer that becomes the hydrophilic portion is sulfonated. In this case, the portion of the benzene ring having a relatively high electron density is sulfonated. That is, a copolymer (polymer) composed of a hydrophilic part segment and a hydrophobic part segment by reacting the copolymer (consisting of an oligomer which becomes a hydrophilic part segment and an oligomer which becomes a hydrophobic part segment) with a sulfooxidant. (Polymer) can be synthesized.

Examples of the sulfonic acid oxidizing agent include chlorosulfonic acid, anhydrous sulfuric acid, fuming sulfuric acid, sulfuric acid, acetylsulfuric acid and the like, and chlorosulfonic acid and fuming sulfuric acid are preferable because they have appropriate reactivity.

The solvent may or may not be used in the sulfonic oxidation reaction. When a solvent is used, the solvent may be any one that is inert to the sulfonic oxidizing agent, and examples thereof include hydrocarbon solvents and halogenated hydrocarbons. Examples of the hydrocarbon solvent include saturated aliphatic hydrocarbons, and linear or branched hydrocarbons having 5 to 15 carbon atoms are particularly preferable, and pentane, hexane, heptane, octane, and decane are preferable from the viewpoint of solubility. More preferred. Examples of halogenated hydrocarbons include halogenated saturated aliphatic hydrocarbons and halogenated aromatic hydrocarbons. Examples of the halogenated saturated aliphatic hydrocarbon include monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, dichloroethane, trichloroethane, tetrachloroethane and the like, and dichloromethane is preferable from the viewpoint of ease of handling. Examples of the halogenated aromatic hydrocarbon include chlorobenzene, dichlorobenzene, trichlorobenzene and the like, and chlorobenzene is preferable from the viewpoint of ease of handling.

The reaction temperature of the sulfonic oxidation step may be appropriately set according to the reaction, and specifically, it may be set to -80 ° C to 200 ° C, which is the optimum range of use of the sulfonate, more preferably -50 ° C to -50 ° C. It is 150 ° C., more preferably −20 ° C. to 130 ° C. If the temperature is lower than -80 ° C, the reaction is slowed down, and the desired sulfonate oxidation tends not to proceed to 100%, and if the temperature is higher than 200 ° C, a side reaction tends to occur.

The reaction time of the sulfonic oxidation step can be appropriately selected depending on the structure of the oligomer that becomes the hydrophilic segment, but is usually in the range of about 1 minute to 50 hours. If it is shorter than 1 minute, uniform sulfonic oxidation tends not to proceed, and if it is longer than 50 hours, a side reaction tends to occur.

The amount of the sulfooxidant added in the sulfonate step is preferably 1 equivalent to 50 equivalents, where 1 equivalent is the total amount of the sulfonated sites contained in the oligomer that becomes the hydrophilic segment. If it is less than 1 equivalent, the site to be sulfonated tends to be non-uniform, while if it is more than 50 equivalents, the main chain of the oligomer that becomes the hydrophilic segment tends to be easily cleaved.

The concentration of the oligomer that becomes the hydrophilic part segment in the sulfonic oxidation step is not particularly limited as long as the reaction proceeds uniformly when it is brought into contact with the sulfooxidant, but the oligomer that becomes the hydrophilic part segment causes a side reaction such as lowering the molecular weight. From the viewpoint of not causing this and cost advantage due to the suppression of the amount of solvent, it is preferably 1 to 30% by weight based on the total weight of the compound used in the sulfonate oxidation reaction.

As another method, the oligomer that becomes the hydrophobic part segment and the oligomer that becomes the hydrophilic part segment or the end of the hydrophilic monomer having a sulfonic acid group are both set as halogen, and the transition is performed according to the method described in JP-A-2012-229418. A method of polycondensation using a metal compound can also be used. Nickel-based compounds, palladium-based compounds, and copper compounds are preferably used as such transition metal compounds, and zero-valent nickel complexes such as bis (1,5-cyclooctadiene) nickel and tetraxtriphenylphosphine nickel are preferably used. Is used. Further, a divalent nickel complex such as dichlorobistriphenylphosphine nickel may be used in the presence of a reducing agent such as zinc.

The reinforcing material in the present invention is a non-woven fabric containing a mixture of glass fibers and organic fibers. A non-woven fabric as a reinforcing material can be obtained by irregularly weaving a mixture of glass fibers and organic fibers in an appropriate ratio and processing them into a sheet shape. By combining such a reinforcing material with an electrolyte, it is possible to obtain a polymer electrolyte membrane that suppresses dimensional changes during water content and has excellent mechanical strength and wet / dry cycle resistance.

Glass fiber is rigid and has a high elastic modulus, and an electrolyte composite film using the glass fiber has excellent strength, but on the other hand, it has a problem of being brittle. By mixing flexible organic fiber with glass fiber, flexibility is given to the non-woven fabric, and the electrolyte membrane using this as a reinforcing material also becomes flexible, and under the condition of receiving repeated stress of swelling and contraction. However, it can follow the distortion and shows high durability.

The glass fiber constituting the reinforcing material of the present invention is not particularly limited, but is more preferably made of acid-resistant glass, so-called C glass or alkaline glass, which has acid resistance. Since the polymer electrolyte to be composited has a sulfonic acid group, sufficient strength can be maintained even under high temperature acidic conditions in such an embodiment.

Here, the glass called C glass or alkaline glass is generally a glass having a composition such as Na ₂ O or K ₂ O having an alkali content of 0.8 to 20% by mass, and is excellent in acid resistance.

The average fiber diameter of the glass fiber is preferably in the range of 0.1 μm to 20 μm. Within such a range, the balance between the manufacturing cost of the non-woven fabric and the uniformity is good.

In the present invention, the average fiber diameter of the glass fiber is more preferably 1 μm or less, further preferably 0.1 μm to 1 μm. When the average fiber diameter is such a value, the glass fibers are woven at a high density when the non-woven fabric is processed, which is suitable for improving the strength of the polymer electrolyte membrane.

A plurality of types of glass fibers having different average fiber diameters may be mixed. It is more preferable to use a mixture of one having an average fiber diameter of 1 μm or less and one having an average fiber diameter of more than 1 μm and less than 10 μm because the rigidity of the glass nonwoven fabric is improved and high wet-wet cycle resistance is exhibited.

The content of glass fibers having an average fiber diameter of more than 1 μm and less than 10 μm is 10 to 70 with respect to 100% by weight of the total of glass fibers having an average fiber diameter of 1 μm or less and glass fibers having an average fiber diameter of more than 1 μm and less than 10 μm. It is preferably% by weight. Within such a range, the balance between the rigidity and the tensile strength of the polymer electrolyte membrane is good, and the polymer electrolyte is uniformly maintained.

The fiber diameter of the fiber usually varies to some extent, but an average value is used as the fiber diameter in the present invention. The fiber diameter of the glass fiber can be measured by observation with an optical microscope. More specifically, any about 10 fiber diameters in the non-woven fabric are measured as described above, and the average value thereof is taken as the fiber diameter of the glass non-woven fabric.

The average fiber length of the glass fibers constituting the non-woven fabric is preferably in the range of 0.5 mm to 20 mm, and preferably in the range of 2 mm to 15 mm. If the average fiber length is less than 0.5 mm, the mechanical strength of the non-woven fabric is lowered, so that the reinforcing effect of the electrolyte membrane is reduced. On the other hand, when the average fiber length exceeds 20 mm, the dispersibility of the glass fiber at the time of molding the non-woven fabric is lowered, and the uniformity of the thickness and the uniformity of the grain size are lowered. As a result, a non-woven fabric suitable for reinforcing the electrolyte membrane cannot be obtained.

Organic fibers are mixed with the reinforcing material used in the present invention. Specific examples of the organic fiber are not particularly limited, and various organic fibers can be used. For example, polyvinyl chloride fiber, vinyl chloride-vinyl acetate copolymer fiber, low density polyethylene, linear low density polyethylene, polyethylene fiber such as high density polyethylene, homopolypoly, random polypropylene, block polypropylene and other polypropylene. Fibers, acrylic fibers such as polyacrylonitrile, vinyl chloride-acrylonitrile copolymer, vinylon fibers, polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polyester fibers such as polyethylene naphthalate, 6-nylon, 6,6-nylon, 6 , 12-Nylon and other polyamide fibers, cellulose fibers, rayon fibers, polylactic acid fibers, polyimide fibers, polybenzoxazole fibers, aramid fibers and the like.

Of these, polyester fiber, vinylon fiber, polyacrylonitrile fiber, polyethylene fiber, polypropylene fiber, polyamide fiber, cellulose fiber, because of their excellent flexibility, high durability such as heat resistance and acid resistance, and low cost. Rayon fiber and polylactic acid fiber are preferable, and polyester fiber, particularly polyethylene terephthalate is more preferable. One type of these organic fibers may be used, or two or more types may be used in combination.

The average fiber diameter of the organic fibers is preferably in the range of 0.1 to 20 μm, more preferably 1 to 10 μm. When the average fiber diameter is smaller than 0.1 μm, the strength of the organic fiber becomes too weak and the reinforcing effect is reduced. If it is thicker than 20 μm, it becomes difficult to form a non-woven fabric having a uniform thickness.

The length of the organic fiber is preferably in the range of 0.5 mm to 20 mm, preferably in the range of 2 mm to 15 mm. If the average fiber length is less than 0.5 mm, the mechanical strength of the non-woven fabric is lowered, so that the reinforcing effect of the electrolyte membrane is reduced. On the other hand, when the average fiber length exceeds 20 mm, the dispersibility of the organic fibers at the time of molding the non-woven fabric is lowered, and the uniformity of the thickness and the uniformity of the basis weight are lowered. As a result, a non-woven fabric suitable for reinforcing the electrolyte membrane cannot be obtained.

The mixing ratio of the glass fiber and the organic fiber in the reinforcing material of the present invention is preferably in the range of 95/5 to 5/95, more preferably 90/10 to 10/90 in terms of weight ratio. If the proportion of the organic fiber is less than 5% by weight, the effect of softening by the organic fiber cannot be sufficiently obtained, and if it exceeds 95% by weight, the strength of the non-woven fabric is insufficient and the effect of the present invention is difficult to be exhibited.

It is preferable that the reinforcing material further contains a binder. The binder has a function of binding glass fibers and organic fibers to each other.

Various liquid binders are known as binders, for example, acrylic resin dispersion, acrylic resin emulsion, fluororesin dispersion, fluororesin emulsion, polyurethane dispersion, polyurethane emulsion, silicone resin dispersion, silicone resin emulsion, polyimide. There are varnish, polyvinyl alcohol aqueous solution, colloidal silica dispersion, alkyl silicate, silicon or titanium emulsion, titania sol and the like.

Further, as the binder, a curable resin such as a silicon compound generally called a silane coupling agent or an epoxy resin can be used, and an epoxy resin is preferable.

First, examples of silicon-based compounds include those generally referred to as silane coupling agents. Specific examples include vinylsilanes such as vinyltris (β-methoxyethoxy) silanes, vinyltrichlorosilanes and vinyltrimethoxysilanes, acrylic silanes such as γ-methacryloyloxypropyltrimethoxysilanes, γ-aminopropyltrimethoxysilanes and N-β. Aminosilanes such as-(aminoethyl) -γ-aminopropyltrimethoxysilane, epoxysilanes such as γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-ureidopropyl Examples thereof include ureidosilanes such as triethoxysilane, chlorosilanes such as γ-chloropropyltrimethoxysilane, mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, and isocyanatosilanes such as γ-isocyanatopropyltrimethoxysilane. Further, the above-mentioned reaction product of aminosilane and epoxysilane and the reaction product of aminosilane and isocyanatesilane can also be used. These may be used alone or in combination of two or more.

After the treatment with the above-mentioned liquid binder generally used as a binder, a silane coupling agent treatment may be further performed. Since the liquid binder and the silane coupling agent exert a reinforcing effect by independent mechanisms, they can be used together, and the effects are synergized.

Silicon-based compounds other than the silane coupling agent include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, n-propyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, and n-butyl. Alkyl silicates such as trimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, n-dodecyltrimethoxysilane, polydimethylsiloxane, polydiethylsiloxane, polymethylphenylsiloxane, etc. Examples thereof include polysiloxane such as polysiloxane.

The epoxy compound is not particularly limited, and known ones can be used. Examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, glycidyl ether type epoxy resin with bisphenol A proprene oxide adduct, hydrogenated bisphenol A type epoxy resin, and the like.

Also, known curing agents for epoxy resins can be used, and for example, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, N-aminoethylpiperazine, benzyldimethylamine, tris (dimethylaminomethyl). Amine compounds such as phenol, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, dicyandiamide, mentandiamine, xylene diamine, ethylmethylimidazole, various polyamide resins, phthalic anhydride, maleic anhydride, dodecylsuccinic anhydride, hexahydrochloride. Acid anhydrides such as phthalic acid, methylnadic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, and dichlorosuccinic anhydride can be mentioned.

The above binder may contain an inorganic binder. Inorganic binders include synthetic inorganic sol such as silica sol, alumina sol, and titania sol (which are dispersed in water as fine particles and harden as a gel after drying and solidifying), and natural minerals such as kaolin, clay, sepiolite, attapulsite, and bentonite. Mineral powders (dispersed in water and solidified when dried), mineral scales such as mica and smectite, synthetic scales such as silica flakes, silica-titania flakes, and alumina flakes (dispersed in water) (Those that solidify when dried to form a self-film), inorganic binders such as silica fine particles are used, and synthetic inorganic binders with few impurities are preferable, and the average particle size is 0.01 to 2 μm, preferably 0. .1-1 μm, more preferably 0.2-0.6 μm is used.

The amount of the binder added is preferably such that the amount of the solid content of the binder adhered is in the range of 0.5 to 10% (more preferably 2 to 9%) of the mass of the fiber.

By using the binder, the fibers are firmly restrained, the dimensional stability and strength of the non-woven fabric are improved, and the swelling resistance of the reinforced polymer electrolyte membrane is improved so as to exhibit high wet-wet cycle resistance. Become.

The reinforcing material in the present invention can be produced by the following two methods.
In the first method, first, a mixed solution containing glass fibers, organic fibers, and a binder component that strengthens the bond between the fibers is prepared (step (i)). The mixed solution of step (i) may contain a dispersant, a surfactant, a pH adjuster, a flocculant and the like. Next, a non-woven fabric containing fibers and a binder is formed from the mixed solution (step (ii)). The non-woven fabric can be formed, for example, by a general wet papermaking method. After forming the non-woven fabric, heat treatment or the like may be performed if necessary. The step (ii) provides a non-woven fabric in which the fibers are bound to each other with a binder.

In the second method, first, the above-mentioned fibers are used to form a non-woven fabric, for example, by a general wet papermaking method (step (I)). Next, a liquid containing a binder component is applied to the non-woven fabric and then dried to strengthen the bond between the fibers (step (II)). Heat treatment may be performed at the time of drying. The binder may be applied by immersing the non-woven fabric in the binder or impregnating the non-woven fabric with the binder. In step (II), it is preferable to remove the excess binder after applying the binder in order to suppress the formation of a film between the fibers.

The first method has the advantage that the manufacturing process is simple. On the other hand, the second method has an advantage that the binder can be concentrated at the intersection of the fibers, and a high effect can be obtained with a small amount of the binder.

The upper limit of the average thickness of the reinforcing material is preferably 50 μm or less, more preferably 30 μm or less. Since the polymer electrolyte membrane of the present invention is preferably 300 μm or less, it is preferable that the glass nonwoven fabric composited with the polymer electrolyte membrane is also thin within a range having an effect of improving mechanical strength. Further, the lower limit of the average thickness of the reinforcing material is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of improving the strength.

The average thickness of the reinforcing material can be measured by applying a uniform pressure (20 kPa) to the entire reinforcing material and using a dial gauge. More specifically, the thickness of any about 10 points of the non-woven fabric is measured as described above, and the average value is taken as the thickness of the reinforcing material.

When the average thickness of the reinforcing material is in the above range, the basis weight (mass per unit area) is preferably ² to 50 g / m ² , and more preferably ^{2 to} 25 g / m ^2. preferable. When the basis weight is 2 g / m ² or more, the fibers are more entangled with each other and the tensile strength is improved. On the other hand, when the basis weight is 50 g / m ² or less, the basis weight is suitable as a reinforcing material for the electrolyte membrane, and it is not necessary to reduce the basis weight by pressing or the like.

The reinforcing material preferably has a porosity of 80% or more, more preferably 85 to 95%, from the viewpoint of improving the mechanical strength and minimizing the decrease in proton conductivity due to compounding.

The porosity of the reinforcing material can be calculated by calculating the specific gravity from the volume and weight of the reinforcing material and dividing this by the true specific gravity of the fiber.

The polymer electrolyte membrane of the present invention is a composite of the above-mentioned polymer electrolyte and a reinforcing material. That is, the polymer electrolyte membrane of the present invention is composed of a hydrocarbon-based polymer electrolyte having a sulfonic acid group and having a main chain mainly composed of an aromatic ring, in which a reinforcing material is embedded. ..

As the composite method, a conventionally known method can be applied. As a simple method, a reinforcing material is fixed on a substrate such as glass, and then a polymer electrolyte is cast to remove the solvent; a solution of the polymer electrolyte is first cast on a substrate such as glass. After that, a reinforcing material is placed on the reinforcing material, and a solution of the polymer electrolyte is cast to remove the solvent; by dipping the reinforcing material into the solution of the polymer electrolyte, the polymer electrolyte is placed in the voids of the reinforcing material. Is impregnated, a reinforcing material containing the solution is taken out from the solution, and for example, a method of removing the solvent in a vertically spread state is exemplified. When either method is used, the polymer electrolyte exists between the fibers constituting the reinforcing material, and the polymer electrolyte membrane is formed by combining the polymer electrolyte and the reinforcing material.

Examples of the solvent used for preparing the polymer electrolyte solution include dimethyl sulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, and N-methyl. Examples thereof include pyrrolidone. The solvent is removed by drying at a temperature of preferably 10 to 200 ° C, more preferably 40 to 150 ° C. When drying with a single leaf, the drying time is preferably set to a relatively high drying temperature of 20 seconds to 10 minutes. In addition, a method of heat-bonding the polymer electrolyte and the glass non-woven fabric; a method of sandwiching the glass non-woven fabric between two semi-solidified polymer electrolytes containing a solvent, pressing, and drying can also be applied. As described above, the polymer electrolyte membrane of the present invention in which the polymer electrolyte and the reinforcing material are composited can be obtained.

As the polymer electrolyte in the polymer electrolyte membrane of the present invention, the above-mentioned polymer electrolyte of the present invention may be used alone, or other polymer electrolytes and the like may be mixed and used.
Further, the polymer electrolyte membrane of the present invention may contain additives other than the above-mentioned polymer electrolyte and the reinforcing material.

From the viewpoint of proton conductivity, in the polymer electrolyte membrane of the present invention, it is preferable that the polymer electrolyte of the present invention is the main component accounting for 70% by weight or more of the entire polymer electrolyte membrane. Further, after obtaining the electrolyte membrane, a treatment such as biaxial stretching may be performed to control the molecular orientation or the like, or a heat treatment may be performed to control the crystallinity and the residual stress. Further, an appropriate chemical treatment may be applied at the time of film formation. Examples of the chemical treatment include cross-linking to increase the strength of the electrolyte membrane, addition of a protonic compound to increase conductivity, improvement of durability, addition of a trace amount of polyvalent metal ion for ion cross-linking, and the like. Be done. In any case, the polymer electrolyte membrane produced by using the polymer electrolyte in the present invention in combination with conventionally known techniques is within the scope of the present invention.

Further, in the polymer electrolyte membrane of the present invention, various additives usually used, antioxidants for preventing resin deterioration, antistatic agents and lubricants for improving handling in molding as a film are used as electrolyte membranes. It can be appropriately used as long as it does not affect the processing and performance of the product.

As the thickness of the polymer electrolyte membrane of the present invention, any thickness can be selected depending on the intended use. For example, when considering reducing the resistance of the polymer electrolyte membrane when used as a fuel cell, the thinner the polymer electrolyte membrane, the better. On the other hand, considering the gas barrier property, handleability, tear resistance at the time of bonding with the electrode, etc. of the polymer electrolyte membrane, it may not be preferable if the thickness of the polymer electrolyte membrane is too thin. Considering these, the thickness of the polymer electrolyte membrane is preferably 5 μm or more and 300 μm or less, more preferably 10 μm or more and 100 μm or less, and particularly preferably 10 μm or more and 50 μm or less when the output is important as a fuel cell. When the thickness of the polymer electrolyte membrane is 5 μm or more and 300 μm or less, it is easy to manufacture, the membrane resistance and the mechanical properties are well-balanced, and the handleability when processing as a fuel cell material is also excellent. The thickness of the polymer electrolyte membrane can be determined by the measuring method described in Examples.

The ion exchange equivalent (IEC) of the polymer electrolyte membrane of the present invention can be appropriately adjusted by including, for example, a material other than the polymer electrolyte as the polymer electrolyte membrane.

The membrane / electrode assembly according to the present invention (hereinafter referred to as "MEA") can be obtained by applying an electrode catalyst to the polymer electrolyte membrane of the present invention. The electrode catalyst used in the present invention may literally be an electrode catalyst conventionally known to those skilled in the art, and may contain a conductive catalyst carrier and a catalytically active substance supported on the conductive catalyst carrier. , Other specific configurations are not particularly limited. Specifically, a catalyst that is active against the electrode reaction of the fuel cell is used. On the anode side, a catalyst capable of oxidizing fuel (hydrogen, methanol, etc.) is used.

Specific examples of the conductive catalyst carrier include high surface area carbon carriers such as carbon black, Ketjen black, activated carbon, carbon nanohorns, and carbon nanotubes, and include catalyst-supporting ability, electron conductivity, and electrochemical stability. Therefore, these materials are preferable.

Specific examples of the catalytically active substance include platinum, cobalt, ruthenium and the like, and these may be used alone, as an alloy containing at least one of these, or as an arbitrary mixture. In particular, considering the oxidizing ability of the fuel, the reducing ability of the oxidizing agent, and the durability, platinum or an alloy containing platinum is preferable. If necessary, iron, tin, rare earth elements and the like may be used for stabilization and longevity, and these may be composed of three or more components.

The electrode catalyst layer can be prepared by applying a catalyst ink containing a polymer electrolyte, an electrode catalyst and a solvent onto a support and removing the solvent.

As the solvent, any solvent that can dissolve the polymer electrolyte and does not poison the fuel cell catalyst can be used without any limitation.

The catalyst ink may contain additives such as a non-electrolyte binder, a water repellent, a dispersant, a thickener, and a pore-forming agent, if necessary. Further, as these additives, those conventionally known to those skilled in the art can be used, and other specific configurations are not particularly limited. For the catalyst ink prepared by the above composition and method, a coating method as shown below can be used depending on the viscosity and the type of the base material. The coating method of the catalyst ink on the substrate may be any coating method conventionally known to those skilled in the art, and other specific configurations are not particularly limited. For example, methods using knife coaters, bar coaters, sprays, dip coaters, spin coaters, roll coaters, die coaters, curtain coaters, screen printing, etc. can be listed, but are not limited thereto.

When a polymer film is used as the base material, a catalyst layer transfer sheet for a fuel cell can be manufactured, and when a conductive porous sheet is used as a base material, a gas diffusion electrode for a fuel cell can be manufactured. The method for producing MEA has been conventionally studied, such as a polymer electrolyte membrane made of perfluorocarbon sulfonic acid and other hydrocarbon-based polymer electrolyte membranes (for example, sulfonated polyether ether ketone, sulfonated polyether sulfone, sulfone). Known methods performed with polysulfone oxide, polyimide sulfonated, polyphenylene sulfide sulfonated, etc.) are applicable. Such MEA can be used, for example, in a fuel cell, particularly a polymer electrolyte fuel cell.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples.

(Measurement of molecular weight)
The molecular weight was measured by the GPC method. The conditions are as follows.
GPC measuring device: HLC-8220 (manufactured by Tosoh Corporation)
Column: Two SuperAW4000 and SuperAW2500 (manufactured by Showa Denko KK) are connected in series. Column temperature: 40 ° C.
Mobile phase solvent: NMP (N-methylpyrrolidone, LiBr added to 10 mmol / dm3)
Solvent flow rate: 0.3 mL / min
Standard substance: TSK standard polystyrene (manufactured by Tosoh Corporation)
Hereinafter, the number average molecular weight converted with standard polystyrene is referred to as Mn, and the weight average molecular weight converted with standard polystyrene is referred to as Mw.

(Measurement of ion exchange capacity)
As a measurement sample, 10 to 20 mg of the acid-treated membrane was cut out, dried under reduced pressure at 80 ° C., and the dry weight (W _dry ) was measured. The membrane was immersed in a saturated aqueous NaCl solution (30 mL) at room temperature for 24 hours to convert the ionic groups from H ⁺ type to Na ⁺ type. After that, HCl contained in the obtained solution was quantified with a 0.01 M NaOH aqueous solution using an automatic potential difference titrator AT-510 (manufactured by Kyoto Electronics Co., Ltd.), and the ion exchange capacity IEC value was calculated using the following formula. Calculated. Two samples were prepared for the same membrane, and the average value of the two measurements was taken as the calculated IEC value by titration.

(Measurement of swelling rate)
A sample of a polymer electrolyte membrane cut into about 2 cm × 3 cm was prepared, and this was immersed in pure water at room temperature for 6 hours. The dimensional changes and weights of the sample immediately after immersion and the sample which was vacuum-dried at 100 ° C. for 2 hours to be in an absolutely dry state were measured, and the rate of change was calculated. In the plane direction, the dimensional changes on the four sides were measured, and the average value was used as the result. In the vertical direction (film thickness direction), dimensional changes at three points in the plane were measured, and the average value was used as the result.

(Measurement of proton conductivity)
The proton conductivity of the electrolyte membrane was measured using an electrolyte evaluation device (MSB-AD-V-FC) manufactured by Nippon Bell Co., Ltd. The temperature in the chamber was constant at 80 ° C., and the relative humidity (RH) was 20%, 40%, 60%, 80%, and 90%. For the measurement, RH = 20% → 40% → 60% → 80% → 90% → 80% → 60% → 40% → 20% as one cycle, and the value at the time of humidity drop in the second cycle is used as the measurement result. There was. The size of the sample is 1.0 cm x 3.0 cm, the distance between Au probes is 1.0 cm, and using Solartron 1255B / 1287 (manufactured by Toyo Corporation), the AC 4-terminal method (300 mV, 1-10000 Hz) is used. Measurements were made. As the impedance Z, a value having a phase angle close to 0 ° and a value close to 1000 Hz was used according to the board plot. The conductivity σ (S / cm) was calculated by the following formula.
σ = (L / Z) × 1 / A
Here, L is the distance between Au probes (1.0 cm), and A is the cross-sectional area of the sample (1 cm × film thickness X cm).

(Evaluation of dry / wet cycle characteristics)
Preparation of test samples and test conditions were in accordance with the protocol recommended by the Fuel Cell Practical Use Promotion Council (FCCJ). Platinum-carbon catalyst (TEC10E50E manufactured by Tanaka Kikinzoku), Nafion binder (D-521, IEC = 0.95-1.03meq. / G manufactured by DuPont), pure water, and ethanol are mixed in a ball mill for 30 minutes to prepare the catalyst ink. Obtained. The binder / carbon weight ratio was adjusted to 0.7. The catalyst inks obtained above were spray-coated on both sides of the electrolyte membranes produced in Examples and Comparative Examples. The obtained membrane-electrode assembly (MEA) was dried at 60 ° C. for 6 hours and then hot-pressed at 140 ° C. and 10 kgf / cm ² for 3 minutes. The area where the electrodes were formed was 25 cm ² (5 × 5 cm), and the amount of platinum supported was 0.2 mg / cm ^{2 for} both the anode and the cathode. The MEA is sandwiched between a gasket (PTFE, thickness 200 μm) and a gas diffusion layer (SGL carbon SGL25BC, thickness 235 μm), and is a standard cell of Japan Automobile Research Institute (JARI) (anode and cathode are both serpentine type gas flow paths). It was installed in (with) and fixed with a tightening force of 3N using 12 screws. In the characteristic evaluation, nitrogen gas was flowed at 800 mL / min for both the anode and the cathode, and the gas was exchanged at 80 ° C. while holding the dry state (0% RH) and the wet state (150% RH) for 2 minutes each, and the dry-wet cycle. The test was performed. After a predetermined time, hydrogen is passed through the anode at 200 mL / min and nitrogen is passed through the cathode at 200 mL / min (gas is 80 ° C., normal pressure), and the voltage is swept in the range of 0.2 to 0.5 V to increase the current density. It was measured. The crossover current density was defined as the section when the straight portion in the vicinity of 0.4 to 0.5 V was extrapolated to 0 V, and the time when it reached 10 times the initial value was defined as the wet-wet cycle resistance of the electrolyte membrane.

(Non-woven fabric used)
Nonwoven fabrics having the properties shown in Table 1 were prepared and used.

(Manufacturing Example 1)
4,4-Dichlorobenzophenone (75 g, 300 mmol) and 30% fuming sulfuric acid (400 g, 1.5 mol) were added to a 500 mL three-necked flask equipped with a thermometer and a stir bar. The mixture was heated to 130 ° C. and stirring was continued for 6 hours. After cooling to room temperature, the reaction solution was added little by little to ice water. After neutralization by adding an aqueous NaOH solution, the precipitated white solid was recovered by filtration. By drying at 105 ° C. under reduced pressure, 112 g of the sulfonic acid group-containing monomer represented by the following formula was obtained.

(Manufacturing Example 2)
4,4'-Dichlorodiphenyl sulfone (31.6 g, 110 mmol), 4,4'-dihydroxybenzophenone (21.4 g, 100 mmol), potassium carbonate (21.4 g, 100 mmol) in a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube. 20.7 g, 150 mmol), dimethylacetamide (200 mL), and toluene (50 mL) were added. The mixture was heated to 170 ° C. and stirring was continued for 35 hours while removing the water produced. 4,4'-Dichlorodiphenyl sulfone (0.5 g) was added, and the mixture was further stirred for 5 hours. The mixture was filtered through filter paper to remove excess potassium carbonate and then the filtrate was poured into 500 mL of methanol to reprecipitate the product. The product was dried under reduced pressure at 70 ° C. for 4 hours, then washed twice at 60 ° C. with 500 mL of pure water, once at 60 ° C. with 500 mL of methanol, and overnight at 70 ° C. under reduced pressure. The mixture was dried to obtain 41.5 g of the hydrophobic moiety oligomer of the following formula. The molecular weight by GPC was Mn = 6,600 and Mw = 18,800.

(Manufacturing Example 3)
The sulfonic acid group-containing compound (24 g, 52.7 mmol) obtained in Production Example 1 and the hydrophobic part oligomer obtained in Production Example 2 were placed in a 1 L four-necked flask equipped with a mechanical stirrer, a reflux tube, and a DeanStark tube. 16 g), 2,2'-bipyridyl (11.56 g), dimethyl sulfoxide (480 mL), and toluene (120 mL) were added to the nitrogen atmosphere and heated to 170 ° C. for 3 hours for azeotropic dehydration. After distilling off toluene at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (20 g) was added, and the mixture was stirred at the same temperature for 2 hours. After pouring the reaction solution into 700 mL of methanol and reprecipitating, the solid content was washed twice with 6N hydrochloric acid (600 mL), and further washed repeatedly with pure water until the pH of the washing solution reached 7. The solid content was dried under reduced pressure at 105 ° C. overnight to obtain the polymer electrolyte (33.2 g) of the following formula. The polymer electrolyte was pulverized using a pulverizer, washed with methylene chloride and methanol, and dissolved in dimethyl sulfoxide to obtain a polymer electrolyte solution having a solid content concentration of about 12%. As shown in Comparative Example 2, the obtained polymer electrolyte was independently formed into a film, and its molecular weight was measured by GPC and found to be Mn = 134,000 and Mw = 413,000. The ion exchange capacity is 2.58 meq. It was / g.

(Example 1)
A PET film having a thickness of 188 μm was attached onto a glass plate, and the polymer electrolyte solution prepared in Production Example 3 was applied with a bar coater. Non-woven fabric A (10 cm × 10 cm) made of the glass fiber / PET fiber (60 wt% / 40 wt%) shown in Table 1 is gently placed on the coating film so as not to mix bubbles, and then again in Production Example 3. The polymer electrolyte solution was applied with a bar coater. The obtained composite film was dried at 120 ° C. for 12 hours using a hot plate while being applied to the PET film on the glass substrate. The membrane was removed from the glass plate, washed with 6N hydrochloric acid and then distilled water, the surface water was wiped off, and the membrane was dried at 60 ° C. for 30 minutes to obtain a reinforcing membrane. The ion exchange equivalent, swelling rate, and dry-wet cycle resistance of the reinforcing film were measured by the above-mentioned methods. The results are summarized in Table 2. Moreover, the proton conductivity was measured by the above-mentioned method, and the measurement result is shown in FIG. In FIG. 1, for example, "1.E-02" of "Proton conductivity" of the vertical axis means "1 x 10 ^-2 ".

(Comparative Example 1)
A reinforcing film was obtained in the same manner as in Example 1 except that the polymer electrolyte solution of Production Example 3 was used and the non-woven fabric B was used. Ion exchange equivalent, swelling rate, and wet-wet cycle resistance were measured by the methods described above. The results are shown in Table 2.

(Comparative Example 2)
An electrolyte membrane was prepared using the polymer electrolyte solution of Production Example 3 without using a reinforcing material. Ion exchange equivalent, swelling rate, wet-wet cycle resistance, and proton conductivity were measured by the methods described above. The results are shown in Table 2 and FIG.

In Example 1, a reinforcing material in which glass fiber and organic fiber are mixed is used. In Comparative Example 1, a reinforcing material made only of glass fiber is used. In Comparative Example 2, no reinforcing material is used. It can be seen that the polymer electrolyte membrane of the example has a low swelling rate and is suppressed as compared with the comparative example, and has high resistance to the wet and dry cycle. Further, it can be seen that the polymer electrolyte of the example still shows a high value although the proton conductivity is slightly lowered because it is composited with the non-electrolyte non-woven fabric.

Claims (14)

A polymer electrolyte membrane in which a hydrocarbon electrolyte having a sulfonic acid group and a main chain mainly containing an aromatic ring and a reinforcing material are composited, and the reinforcing material is a non-woven fabric containing a mixture of glass fiber and organic fiber. der is,
The glass fiber is a mixture of one having an average fiber diameter of 1 μm or less and one having an average fiber diameter of more than 1 μm and less than 10 μm.
The content of glass fibers having an average fiber diameter of more than 1 μm and less than 10 μm is 10 to 70 with respect to 100% by weight of the total of glass fibers having an average fiber diameter of 1 μm or less and glass fibers having an average fiber diameter of more than 1 μm and less than 10 μm. A polymer electrolyte membrane characterized by being by weight% . The hydrocarbon-based electrolyte is a polymer electrolyte having a hydrophilic portion segment having a sulfonic acid group and the main chain mainly consisting of an aromatic ring, and a hydrophobic portion segment having substantially no sulfonic acid group as the main chain. The polymer electrolyte membrane according to claim 1. The polymer electrolyte membrane according to claim 1 or 2, wherein the organic fiber is at least one fiber selected from polyester, vinylon, polyacrylonitrile, polyethylene, polypropylene, polyamide, cellulose, rayon and polylactic acid. The polymer electrolyte membrane according to any one of claims 1 to 3, wherein the organic fiber is a polyethylene terephthalate fiber. The polymer electrolyte membrane according to any one of claims 1 to 4, wherein the average fiber diameter of the organic fiber is 1 to 10 μm. The polymer electrolyte membrane according to any one of claims 1 to 5, wherein the average fiber diameter of the glass fiber is 1 μm or less. The polymer electrolyte membrane according to any one of claims 1 to 6 , wherein the mixing ratio of the glass fiber and the organic fiber is 95/5 to 5/95 by weight. The polymer electrolyte membrane according to any one of claims 1 to 7 , wherein the nonwoven fabric contains a binder component. The polymer electrolyte membrane according to claim 8 , wherein the binder component is an epoxy resin. The polymer electrolyte membrane has an ion exchange capacity of 1.5 to 3.5 meq. The polymer electrolyte membrane according to any one of claims 1 to 9 , which is / g. The polymer electrolyte membrane according to any one of claims 1 to 10 , wherein the non-woven fabric has an average thickness of 5 to 50 μm at a pressure of 20 kPa and a mass per unit area of 5 to 50 g / m ² . The polymer electrolyte membrane according to any one of claims 1 to 11 , wherein the polymer electrolyte is present between the fibers constituting the reinforcing material. A membrane / electrode assembly for a fuel cell using the polymer electrolyte membrane according to any one of claims 1 to 12 . A fuel cell using the polymer electrolyte membrane according to any one of claims 1 to 12 .

Images