JP2016139587A - Polymer electrolyte membrane, membrane/electrode assembly and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrocarbon polymer electrolyte membrane suitable for use as an electrolyte membrane for a fuel cell, which exhibits high proton conductivity, has mechanical characteristics low in moisture dependency, and accordingly has membrane strength that is not impaired even after a water-containing state and a dried state are repeated.SOLUTION: A polymer electrolyte membrane is obtained by combining a glass non-woven fabric and a polymer electrolyte including, as a main chain, a unit derived from a hydrophobic oligomer, which substantially does not have a sulfonic acid group and has a main chain mainly comprising an aromatic ring group, and a unit derived from a hydrophilic oligomer, which has a sulfonic acid group and has a main chain mainly comprising an aromatic ring group. The glass non-oven fabric includes glass fibers having an average diameter of 1 μm or less, and is treated with a silicon-based compound binder or an epoxy-based compound binder.SELECTED DRAWING: None

Description

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

In recent years, development of highly efficient and clean energy sources has been demanded from the viewpoint of environmental problems such as global warming. Fuel cells are attracting attention as one candidate for that requirement. A fuel cell directly supplies power by supplying a fuel such as hydrogen gas or methanol and an oxidant such as oxygen to electrodes separated by an electrolyte, while oxidizing the fuel on the one hand and reducing the oxidant on the other. is there. Among the fuel cell materials described above, one of the most important materials is an electrolyte. Various types of electrolyte membranes have been developed so far to separate the electrolyte fuel and oxidant, and in recent years, the electrolyte membrane is composed of a polymer compound containing a proton conductive functional group such as a sulfonic acid group. The development of polymer electrolytes is thriving. In addition to the solid polymer fuel cell, such a polymer electrolyte is used as a raw material for electrochemical elements such as a humidity sensor, a gas sensor, and an electrochromic display element. Among these polymer electrolyte utilization methods, in particular, polymer electrolyte fuel cells are expected as one of the pillars of new energy technology. For example, a polymer electrolyte fuel cell using an electrolyte membrane made of a polymer compound having a proton-conducting functional group has features such as operation at a low temperature and reduction in size and weight. Application to consumer cogeneration systems and consumer small portable devices is under consideration.

As an electrolyte membrane used in a polymer electrolyte fuel cell, there is a styrene-based cation exchange membrane developed in the 1950s. However, the fuel cell has poor stability under a fuel cell operating environment and has a sufficient lifetime. Has not yet been manufactured. On the other hand, as an electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. Perfluorocarbon sulfonic acid membranes are said to have high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, Nafion (registered trademark) has a drawback that it is very expensive because it uses high raw materials and undergoes complicated manufacturing processes. In addition, it has been pointed out that it is deteriorated by hydrogen peroxide generated by the electrode reaction and by-product hydroxy radical. Furthermore, due to its structure, there is a limit to the introduction of sulfonic acid groups that are proton conducting groups.

Against this background, the development of hydrocarbon electrolyte membranes has come to be expected. The reason for this is that the hydrocarbon electrolyte membrane is easy to have a variety of chemical structures, the range of introduction of proton conducting groups such as sulfonic acid groups can be adjusted widely, compounding with other materials, introduction of crosslinking, etc. This is because there is a feature that is relatively easy.

In recent years, there are examples in which proton conductivity is improved by introducing a large number of sulfonic acid groups into the electrolyte membrane. However, such a membrane has a large swelling in a water-containing state, and by repeating the water-containing state and the dry state, the membrane is The strength was impaired, and there was a problem in using it as an electrolyte membrane for fuel cells.

Thus, it has been proposed to reinforce the electrolyte membrane with a porous substrate. Patent Document 1 discloses a method in which various polymer electrolytes such as fluorine-based and hydrocarbon-based compounds are combined with inorganic fibers such as glass cloth by thermocompression bonding. However, in the polymer electrolyte exemplified in this, although the strength can be improved by compounding, the problem is a decrease in proton conductivity with low humidification. Patent Document 2 discloses a polymer electrolyte membrane having a reinforcing material such as glass fiber. However, the polyelectrolytes exemplified here are alkaline polymers and acidic polymers, and the problem is also a decrease in proton conductivity due to low humidity due to the composite.

JP 2006-128014 A JP 2009-545841 A

The object of the present invention is to provide a hydrocarbon-based high fiber reinforced with a nonwoven glass fabric that exhibits high proton conductivity, high swelling resistance, and therefore high dry and wet cycle resistance, and is suitable for use as an electrolyte membrane for fuel cells. It is to provide a molecular electrolyte membrane.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a composite film obtained by forming a specific glass nonwoven fabric together with an electrolyte resin is superior in swelling resistance and wet and dry compared to a film made of an electrolyte resin alone. In a test for evaluating mechanical stability such as a cycle test, it was found that higher durability was developed, and the present invention was completed.

That is, the present invention includes a unit derived from a hydrophobic moiety oligomer having substantially no sulfonic acid group, the main chain mainly consisting of an aromatic ring group, and a sulfonic acid group, the main chain being mainly aromatic. A polymer electrolyte membrane comprising a polymer electrolyte having a main chain derived from a unit derived from a hydrophilic oligomer comprising a cyclic group and a glass nonwoven fabric, wherein the glass nonwoven fabric is a glass having an average diameter of 1 μm or less. The present invention relates to a polymer electrolyte membrane containing fibers and treated with a silicon compound binder or an epoxy compound binder.

It is preferable that the glass nonwoven fabric further includes glass fibers having an average diameter of more than 1 μm and less than 10 μm.

The glass nonwoven fabric is preferably treated with an epoxy compound binder.

（式中、Ａｒ^１は、下記式群（２）に記載の構造のいずれかを有する２価の基を表し、当該２価の基は置換基を有していてもよい。Ａｒ^２は、スルホン酸基を少なくとも１つ有する２価の芳香族基を表す。Ａｒ^１またはＡｒ^２が複数存在する場合は、それらは同一であっても異なっていてもよい。ｎは１〜４の整数、Ｘは−Ｏ−または−Ｓ−、Ｙは−ＳＯ_２−または−ＣＯ−を表す。）

It is preferable that the unit derived from the hydrophilic part oligomer contains at least one of the structures described in the following general formula group (1) as a repeating unit.

(In the formula, Ar ¹ represents a divalent group having any of the structures described in the following formula group (2), .Ar ² may have a substituent group of the divalent groups, A divalent aromatic group having at least one sulfonic acid group, when there are a plurality of Ar ¹ or Ar ^{2 s} , they may be the same or different, n is an integer of 1 to 4, X represents —O— or —S—, and Y represents —SO ₂ — or —CO—.

Ar ² is preferably a divalent aromatic group having any one of the structures described in the following formula group (3) and having at least one sulfonic acid group.

（式中、Ａｒは、２価の芳香族基を表す。Ａｒが複数存在する場合は、それらは同一であっても異なっていてもよい。） It is preferable that the unit derived from the hydrophobic moiety oligomer contains at least one of the structures described in the following general formula group (4) as a repeating unit.

(In the formula, Ar represents a divalent aromatic group. When a plurality of Ar are present, they may be the same or different.)

The ion exchange capacity of the polymer electrolyte membrane is 1.5 to 3.5 meq. / G is preferable.

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

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

According to the present invention, a specific glass nonwoven fabric is combined with a polymer electrolyte having a specific structure, thereby suppressing dimensional changes when containing water, excellent mechanical strength, and high proton conductivity even under low humidification. A polymer electrolyte membrane having properties can be provided. Further, by using this polymer electrolyte membrane, high performance and high mechanical strength can be realized regardless of the humidity of the fuel gas, so that a fuel cell with high reliability in long-time use can be provided.

It is a wet-and-dry cycle resistance comparison test result of Example 6 and Comparative Example 1.

An embodiment of the present invention will be described as follows. The present invention is not limited to the following description.

<1. Polymer electrolyte>
The polyelectrolyte used in the present invention, that is, the polyelectrolyte that is combined with the glass nonwoven fabric, has substantially no sulfonic acid group, a unit derived from a hydrophobic oligomer having a main chain mainly composed of an aromatic ring group, and A unit having a sulfonic acid group and having a main chain derived from a hydrophilic oligomer mainly composed of an aromatic ring group is used as the main chain. The polymer electrolyte is preferably a block copolymer composed of a unit derived from a hydrophobic part oligomer and a unit derived from a hydrophilic part oligomer. By using a block copolymer, the proton conductivity of the polymer electrolyte under low humidity is improved.

The unit derived from the hydrophilic part oligomer has a sulfonic acid group, and the main chain mainly consists of an aromatic ring group. That is, a sulfonic acid group is introduced into the unit derived from the hydrophilic part oligomer. Since the unit derived from the hydrophilic part oligomer has a sulfonic acid group, the proton conductivity of the polymer electrolyte is expressed, and the main chain of the unit derived from the hydrophilic part oligomer is mainly composed of an aromatic ring group. Excellent heat resistance and chemical durability.

The sulfonic acid group may be, for example, a salt such as sodium salt or potassium salt, or may be a sulfonic acid ester group such as neopentyl ester, methyl ester, or propyl ester. In particular, during and after the synthesis of the oligomer, it is often preferable to have a protective group such as a salt or ester. However, when the polymer electrolyte is used as an electrolyte membrane of a fuel cell, for example, it is inorganic. It is often used after being converted into a sulfonic acid group by immersing in an acid aqueous solution. Therefore, in the present invention, the sulfonic acid group includes a state having a protective group such as a salt or an ester as long as it 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 unit derived from the hydrophilic oligomer. When the number is more than 6, the water solubility of the unit increases, and the handling during synthesis tends to be difficult. When it is less than one, sufficient proton conductivity tends to be difficult to be exhibited.

The unit derived from the hydrophilic oligomer has a main chain mainly composed of an aromatic ring group. Here, “the main chain is mainly composed of an aromatic ring group” means that the molecular weight of the portion other than the main chain linking group (ether group, thioether group, sulfone group, ketone group, sulfide group, etc.) in the unit is 100%. In this case, it means that 70% or more of them consists of an aromatic ring group. Examples of the aromatic ring group include benzene, naphthalene, anthracene, biphenyl, aromatic heterocyclic groups containing sulfur, nitrogen and the like.
When the main chain is mainly composed of an aromatic ring group, chemical and thermal stability is high. Examples of such a main chain structure include polyether, polyether ketone, polyether ether ketone, polyether sulfone, polyether ether sulfone, polyketone, polysulfone, polysulfide, polyphenylene, polyimide, polybenzimidazole, and the like.

（式中、Ａｒ^１は、下記式群（２）に記載の構造のいずれかを有する２価の基を表し、当該２価の基は置換基を有していてもよい。Ａｒ^２は、スルホン酸基を少なくとも１つ有する２価の芳香族基を表す。Ａｒ^１またはＡｒ^２が複数存在する場合は、互いに同じであっても異なっていてもよい。ｎは１〜４の整数、Ｘは−Ｏ−または−Ｓ−、Ｙは−ＳＯ_２−または−ＣＯ−を表す。）

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

(In the formula, Ar ¹ represents a divalent group having any of the structures described in the following formula group (2), .Ar ² may have a substituent group of the divalent groups, Represents a divalent aromatic group having at least one sulfonic acid group, and when there are a plurality of Ar ¹ or Ar ^{2 s} , they may be the same or different from each other, n is an integer of 1 to 4, X Represents —O— or —S—, and Y represents —SO ₂ — or —CO—.

The Ar ² is a divalent aromatic group having any one of the structures described in the following formula group (3) and having at least one sulfonic acid group, that is, the following formula group (3 ) Is preferably a structure in which at least one sulfonic acid group is introduced into a divalent aromatic group having any one of the structures described in (1).

In the structure described in the general formula group (1), the benzene ring may have a substituent. The divalent group having the structure described in the above formula group (2) may have a substituent. Furthermore, the divalent aromatic group having the structure described in the above formula group (3) may have a substituent in addition to the sulfonic acid group. Examples of these substituents include alkyl groups having 1 to 6 carbon atoms (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc.), and alkoxy groups having 1 to 6 carbon atoms (methoxy group, ethoxy group). Group, propoxy group, butoxy group, pentyloxy group, hexyloxy group, etc.), phenyl group and the like. One or more substituents can be included. The unit derived from the hydrophilic part oligomer may have a sulfonic acid group in any of its main chain, side chain, and both (main chain and side chain).

As a monomer which comprises a hydrophilic part oligomer, the monomer which can comprise the structure as described in the said General formula group (1) is mentioned, for example, Specifically, the monomer represented by the following Formula is mentioned preferably. In addition, in the case where X is —S— in the general formula group (1), a monomer having an —SH group instead of an —OH group in the monomer represented by the following formula may be used. Furthermore, as will be described later, when preparing a hydrophilic part oligomer by polymerization of a monomer having a sulfonic acid group, in the monomer represented by the following formula, a monomer having a sulfonic acid group on its benzene ring And so on.

Other examples of the monomer constituting the hydrophilic part oligomer include those shown in JP-A-2002-238889 (monomers having an electron withdrawing group and an electron donating group).

The ion exchange capacity of only the unit derived from the hydrophilic oligomer (hereinafter, the ion exchange capacity is also referred to as IEC) can be set high for IEC as a polymer electrolyte membrane, and also exhibits high proton conductivity under low humidification. 4.0 meq. / G or more is preferable. The IEC of the unit derived from the hydrophilic oligomer is calculated based on the NMR analysis and the IEC of the block electrolyte (which can be easily obtained by a conventionally known method such as titration) by the weight ratio of the unit derived from the hydrophilic oligomer. However, in this specification, it is obtained by the latter method. That is, the IEC of the unit derived from the hydrophilic part oligomer is the IEC of the polymer electrolyte obtained in the same manner as the IEC measurement method of the polymer electrolyte membrane described in the examples, and the weight ratio of the unit derived from the hydrophilic part oligomer. Calculate by dividing by. In addition, meq. / G means milliequivalent / g.

The unit derived from the hydrophobic part oligomer has substantially no sulfonic acid group. “Substantially has no sulfonic acid group” means that the unit derived from the hydrophobic part oligomer has no sulfonic acid group or the number of sulfonic acid groups per repeating unit in the unit derived from the hydrophobic part oligomer Means 1/10 or less of the number of sulfonic acid groups per repeating unit in the unit derived from the hydrophilic oligomer. Thereby, 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 unit derived from the hydrophobic part oligomer.

The unit derived from the hydrophobic part oligomer is preferably a polyimide-based, polybenzimidazole-based, polyether-based, etc. structure having a main chain mainly composed of an aromatic ring group from the viewpoint of heat resistance. From the viewpoint of easiness. “The main chain is mainly composed of an aromatic ring group” means that when the molecular weight of the unit other than the main chain linking group (ether group, sulfone group, ketone group, sulfide group, etc.) in the unit is 100%, 70 It means that more than% consists of aromatic ring groups.

（式中、Ａｒは、２価の芳香族基を表す。Ａｒが複数存在する場合は、それらは同一であっても異なっていてもよい。） As a unit derived from such a hydrophobic part oligomer, it is preferable that at least one of the structures described in the following general formula group (4) is included as a repeating unit.

(In the formula, Ar represents a divalent aromatic group. When a plurality of Ar are present, they may be the same or different.)

Preferred examples of the divalent aromatic group for Ar include a group represented by the following formula group (5).

Moreover, 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). Group, propoxy group, butoxy group, pentyloxy group, hexyloxy group, etc.), phenyl group, cyano group and the like. One or more substituents can be included.

As a monomer which comprises a hydrophobic part oligomer, the monomer which can comprise the structure of the said General formula group (4) is mentioned, for example, Specifically, the monomer represented by the following Formula is mentioned preferably.

The molecular weight of the unit derived from the hydrophilic part oligomer and the unit derived from the hydrophobic part oligomer vary depending on the chemical structure, ease of synthesis, etc., but each has a number average molecular weight of 700 to 30,000 [g / mol]. Is preferable, and 2,000 to 10,000 [g / mol] is more preferable. If it is smaller than 700 [g / mol], the properties as a block copolymer type polymer electrolyte tend to hardly appear, and if it is larger than 30,000 [g / mol], synthesis becomes difficult due to problems such as solubility. There is a tendency to become.

The molecular weight of the polyelectrolyte is preferably 10,000 to 300,000 [g / mol] in terms of number average molecular weight, and 30,000 to 150,000 [g / mol] from the balance of ease of synthesis and solubility in a solvent. Is more preferable. The molecular weight of each oligomer and polymer electrolyte can be determined by the measurement method described in the examples.

The IEC of the polymer electrolyte is 1.5 to 3.5 meq. / G because it is easy to express the performance as an electrolyte, and is preferably 1.6 to 3.0 meq. / G is more preferable because it provides 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 measurement method described in the examples.

In addition, it is also within the scope of the present invention to perform chemical modification such as introduction of cross-linking to the polymer electrolyte in order to further improve the mechanical strength or suppress swelling with respect to moisture.

The polymer electrolyte can be produced by a conventionally known method. For example, after preparing an oligomer that can become a hydrophilic part oligomer, this and a hydrophobic part oligomer are converted into a block copolymer, and only the unit that can become the hydrophilic part of the block copolymer is sulfonated to produce a hydrophilic part-hydrophobic part block copolymer. (Method (a)): After preparing an oligomer that can be a hydrophilic part oligomer, a sulfonic acid group is introduced to prepare a hydrophilic part oligomer, and this is a block copolymer of the hydrophobic part oligomer (method ( b)); a method in which a hydrophilic oligomer is prepared by polymerization of a monomer having a sulfonic acid group, and a hydrophobic copolymer is made into a block copolymer (method (c)); a large amount having a hydrophobic oligomer and a sulfonic acid group As a result, the unit derived from the hydrophilic part oligomer and the unit derived from the hydrophobic part oligomer How to block copolymer consisting of (method (d)) and the like.

The method (a) will be described below. In addition, the manufacturing method of a polymer electrolyte is not limited to the following.
First, an oligomer (an oligomer including a site capable of being sulfonated) and a hydrophobic part oligomer are prepared using the monomer constituting the hydrophilic part oligomer and the monomer constituting the hydrophobic part oligomer. Methods for obtaining these oligomers include 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-containing group at the terminal, or a monomer having a leaving group. Examples thereof include a method in which a catalyst is added and condensed.

The polymerization reaction (condensation reaction) can be performed in a molten state without using a solvent, but is preferably performed 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 solvent include dichlorobenzene and trichlorobenzene. Examples of ether solvents include tetrahydrofuran, dioxane, cyclopentyl methyl ether, and the like. Examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone. 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 and diethyl sulfoxide. These may be used alone or in combination of two or more.

In order to accelerate the reaction, a basic compound is usually used as a catalyst. As the basic compound, an alkali metal salt, an alkaline earth metal salt, or the like is preferably used. For example, LiOH, NaOH, KOH, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , LiHCO ₃ , NaHCO ₃ , KHCO _{3 and the} like.

What is necessary is just to set the reaction temperature of a polymerization reaction process suitably according to a polymerization reaction. Specifically, it may be set to 20 ° C. to 250 ° C. of the optimum use range, 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 be easily broken. Although the reaction time of a polymerization reaction process is not specifically limited, Preferably it is 0.1-500 hours, More preferably, it is 0.5-300 hours.

After obtaining the oligomer which can become a hydrophilic part oligomer and the hydrophobic part oligomer as mentioned above, these are chemically bonded to form a block copolymer. The method of chemically bonding these oligomers to form a block 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 (“Synthesis and Reaction of Polymer (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 and an oligomer having a leaving group such as a halogen-containing group at the terminal are condensed in the presence of a basic compound to form a block copolymer. Polymerize. Alternatively, each oligomer having a halogen-containing group at the terminal can be condensed in the presence of a transition metal to form a block copolymer.

Next, in the block copolymer obtained as described above, only the unit that can be a hydrophilic portion is sulfonated. In this case, a portion having a relatively high electron density of the benzene ring is sulfonated. That is, a unit derived from a hydrophilic part oligomer and a unit derived from a hydrophobic part oligomer by reacting the block copolymer (obtained from an oligomer that can be a hydrophilic part oligomer and a hydrophobic part oligomer) and a sulfonated agent. A block copolymer (polymer electrolyte) made of can be synthesized.

Examples of the sulfonating agent include chlorosulfonic acid, sulfuric anhydride, fuming sulfuric acid, sulfuric acid, acetyl sulfuric acid and the like. Chlorosulfonic acid and fuming sulfuric acid are preferable because they have appropriate reactivity.
In the sulfonation reaction, a solvent may or may not be used. In the case of using a solvent, the solvent is not particularly limited as long as it is inert to the sulfonated agent, and examples thereof include hydrocarbon solvents and halogenated hydrocarbon solvents. Examples of the hydrocarbon solvent include saturated aliphatic hydrocarbons, and linear or branched hydrocarbons having 5 to 15 carbon atoms are particularly preferable. From the viewpoint of solubility, pentane, hexane, heptane, octane and decane are preferable. More preferred. Examples of the halogenated hydrocarbon solvent include a halogenated saturated aliphatic hydrocarbon and a halogenated aromatic hydrocarbon. Examples of the halogenated saturated aliphatic hydrocarbon include monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, dichloroethane, trichloroethane, tetrachloroethane, and the like. Dichloromethane is preferable because of easy handling. Examples of the halogenated aromatic hydrocarbon include chlorobenzene, dichlorobenzene, trichlorobenzene, and the like, and chlorobenzene is preferable because of easy handling.

The reaction temperature of the sulfonation process may be set as appropriate according to the reaction, specifically, it may be set to −80 ° C. to 200 ° C. which is the optimum use range of the sulfonation agent, more preferably −50 ° C. to It is 150 degreeC, More preferably, it is -20 degreeC-130 degreeC. If the temperature is lower than −80 ° C., the reaction is slow, and the intended sulfonation tends not to proceed to 100%, and if the temperature is higher than 200 ° C., side reaction tends to occur.

The reaction time of the sulfonating step can be appropriately selected depending on the structure of the oligomer that can be a hydrophilic part oligomer, but it may usually be in the range of about 1 minute to 50 hours. When it is shorter than 1 minute, uniform sulfonation tends not to proceed, and when it is longer than 50 hours, side reaction tends to occur.

The addition amount of the sulfonating agent in the sulfonating step is preferably 1 to 50 equivalents when the total amount (mole) of the sites to be sulfonated contained in the oligomer that can be a hydrophilic oligomer is 1 equivalent. When the amount is less than 1 equivalent, there is a tendency that a portion that is not sulfonated is generated. On the other hand, when the amount is more than 50 equivalents, the main chain of the oligomer that can be a hydrophilic oligomer tends to be cleaved.

The concentration of the oligomer capable of becoming a hydrophilic oligomer in the sulfonating step is not particularly limited as long as the reaction proceeds uniformly when brought into contact with the sulfonating agent, but the oligomer capable of becoming the hydrophilic oligomer undergoes side reactions such as lower molecular weight. From the viewpoint of not causing it and cost superiority by suppressing the amount of solvent, the content is preferably 1 to 30% by weight with respect to the total weight of the compound used in the sulfonation reaction.

In the above methods (b) to (d), the ends of the hydrophobic oligomer and the hydrophilic oligomer or the hydrophilic monomer having a sulfonic acid group are all halogenated, and the method described in JP 2012-229418 A is followed. Alternatively, a polycondensation method using a transition metal compound can also be used. As such a transition metal compound, a nickel-based compound, a palladium-based compound, or a copper compound is preferably used, and preferably a zero-valent nickel complex such as bis (1,5-cyclooctadiene) nickel or tetrakistriphenylphosphine nickel. Is used. Further, a divalent nickel complex such as dichlorobistriphenylphosphine nickel may be used in the presence of a reducing agent such as zinc.

<2. Glass nonwoven fabric>
The glass nonwoven fabric is a glass fiber that is irregularly entangled and processed into a sheet shape. The glass nonwoven fabric in the present invention includes glass fibers having an average diameter of 1 μm or less and is treated with a silicon compound binder or an epoxy compound binder. When the glass nonwoven fabric has such characteristics, it is possible to obtain a polymer electrolyte membrane having high mechanical strength, suppressing dimensional changes when containing water, and having excellent dry and wet cycle resistance.

If the average diameter of the glass fibers exceeds 1 μm, the wet / dry cycle resistance of the polymer electrolyte membrane tends to be lowered. Moreover, it is preferable that the average diameter of glass fiber is 0.8 micrometer or less.

The glass nonwoven fabric may further contain glass fibers having an average diameter of more than 1 μm and less than 10 μm. It is more preferable to mix glass fibers having an average diameter of 1 μm or less with those having an average diameter of more than 1 μm and less than 10 μm because the rigidity of the glass nonwoven fabric is improved and higher wet / dry cycle resistance is exhibited. It is preferable that the content rate of the glass fiber whose average diameter exceeds 1 micrometer and is less than 10 micrometers is 10 to 70 weight% with respect to the total 100 weight% of glass fiber. If it is less than 10% by weight, the effect of improving the rigidity is small, and if it exceeds 70% by weight, the gap between the thick glass fibers spreads and the tensile strength tends to decrease, and the polymer electrolyte is uniformly distributed in a minute region. There is a possibility that it cannot be held.

Since the fiber diameter of glass fiber usually varies to some extent, an average value is used. More specifically, about 10 arbitrary fiber diameters in a glass nonwoven fabric are observed and measured with an optical microscope, and the average value is taken as the average diameter of the glass fibers.

The average fiber length of the glass fibers constituting the nonwoven fabric is preferably in the range of 0.5 mm to 20 mm, and more 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 nonwoven fabric decreases, and the reinforcing effect of the electrolyte membrane tends to decrease. On the other hand, when the average fiber length exceeds 20 mm, the dispersibility of the glass fibers at the time of forming the nonwoven fabric tends to decrease, and the uniformity of thickness and the uniformity of basis weight tend to decrease. As a result, there is a possibility that a nonwoven fabric suitable for reinforcing the electrolyte membrane cannot be obtained.

Since the polymer electrolyte to be combined has a sulfonic acid group, it is more preferable from the viewpoint of durability that the glass fiber is made of acid-resistant glass, so-called C glass or alkali-containing glass. . Here, glass called C glass or alkali-containing glass is a glass having a composition having an alkali content of 0.8 to 20% by weight, and is excellent in acid resistance.

Various compounds are known as binders, but the glass nonwoven fabric used in the present invention is treated with a silicon compound binder or an epoxy compound binder, thereby firmly restraining the glass fibers. The dimensional stability and strength of the nonwoven fabric can be increased. Further, the swelling resistance and the wet and dry cycle resistance of the reinforced polymer electrolyte membrane are improved. When a nonwoven fabric is formed only with glass fibers, the dimensional stability and tensile strength of the nonwoven fabric depend only on the entanglement of the fibers. Therefore, the connection between the fibers is weak, and the glass fiber that is in close contact with the polymer electrolyte also moves with the deformation of the polymer electrolyte. That is, the binding force between the glass fibers is very weak, and the dimensional stability required for the electrolyte membrane of the fuel cell cannot be obtained.

In addition, you may use a binder individually or in mixture of 2 or more types. Among the above binders, epoxy compound binders are preferable from the viewpoint that the binding force of glass fibers is strong and the affinity with the polymer electrolyte is high, so that the wet and dry cycle resistance of the polymer electrolyte membrane is further improved.

As an example of a silicon-type compound binder, what is generally called a silane coupling agent is mentioned first. Specific examples include vinyl silanes such as vinyltris (β-methoxyethoxy) silane, vinyltrichlorosilane, vinyltrimethoxysilane, acrylic silanes such as γ-methacryloyloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β. Aminosilanes such as-(aminoethyl) -γ-aminopropyltrimethoxysilane, epoxysilanes such as γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-ureidopropyl Ureidosilane such as triethoxysilane, chlorosilane such as γ-chloropropyltrimethoxysilane, mercaptosilane such as γ-mercaptopropyltrimethoxysilane, isocyanate such as γ-isocyanatopropyltrimethoxysilane And tosilane. Further, the reaction product of aminosilane and epoxysilane, the reaction product of aminosilane and isocyanate silane, or the like can also be used.

Silicon compound binders other than silane coupling agents include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, n-propyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, n- Alkyl silicates such as butyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, n-dodecyltrimethoxysilane, polydimethylsiloxane, polydiethylsiloxane, polymethylphenylsiloxane And the like.

There is no limitation in particular as an epoxy-type compound binder, A well-known thing can be used. Illustrative examples include bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins, glycidyl ether type epoxy resins of bisphenol A propylene oxide adducts, and hydrogenated bisphenol A type epoxy resins.

When using an epoxy compound binder, an epoxy resin curing agent is used in combination. As the curing agent, known ones can be used. For example, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, N-aminoethylpiperazine, benzyldimethylamine, tris (dimethylaminomethyl) phenol, metaphenylenediamine , Amine compounds such as diaminodiphenylmethane, diaminodiphenylsulfone, dicyandiamide, menthanediamine, xylenediamine, ethylmethylimidazole, various polyamide resins, phthalic anhydride, maleic anhydride, dodecyl succinic anhydride, hexahydrophthalic anhydride, methyl anhydride Examples thereof include acid anhydrides such as nadic acid, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, and dichlorosuccinic anhydride.

Examples of binders other than silicon compound binders and epoxy compound binders include acrylic resin dispersions, acrylic resin emulsions, fluororesin dispersions, fluororesin emulsions, polyurethane dispersions, polyurethane emulsions, silicone resin dispersions, and silicone resin emulsions. Various liquid binders such as polyimide varnish, aqueous polyvinyl alcohol solution, colloidal silica dispersion, alkyl silicate, silicon or titanium alkoxide, and titania sol are known.

After the treatment with the binder generally used as a binder, the treatment with the silane coupling agent may be further performed. Since the general binder and the silane coupling agent exhibit a reinforcing effect by an independent mechanism, they can be used together, and the effects are synergistic.

The above silicon compound binder or epoxy compound binder may contain an inorganic binder. As inorganic binders, synthetic inorganic sols such as silica sol, alumina sol, and titania sol (dispersed in water as fine particles and hardened as gel after drying and solidification), natural such as kaolin, clay, sepiolite, attapulgite, bentonite Mineral mineral powder (which disperses in water and then solidifies upon drying), mineral flakes such as mica and smectite, synthetic flakes such as silica flakes, silica-titania flakes and alumina flakes (dispersed in water) Inorganic binders such as silica fine particles are used. Among them, a synthetic inorganic binder with few impurities is preferable. Further, those having an average particle diameter of 0.01 to 2 μm, preferably 0.1 to 1 μm, more preferably 0.2 to 0.6 μm are used.

About the usage-amount of a silicon-type compound binder or an epoxy-type compound binder, the adhesion amount of the solid content of the binder in a glass nonwoven fabric is 0.5-10% (more preferably 2-9%) of the mass of glass fiber. It is preferable to adjust the range.

The glass nonwoven fabric used by this invention can be manufactured with the following method, for example.

In the first method, first, a mixed solution containing glass fibers and a binder component that strengthens the bonding between the glass fibers is prepared (step (i)). As described above, a glass fiber having an average diameter of 1 μm or less or a mixture of an average diameter of 1 μm or less and an average diameter of more than 1 μm and less than 10 μm is used. As the binder component, the above silicon compound or epoxy compound is used. The mixed solution in step (i) may contain a dispersant, a surfactant, a pH adjuster, a flocculant and the like. Next, a nonwoven fabric containing glass fibers and a binder is formed from the mixed solution (step (ii)). The nonwoven fabric can be formed by, for example, a general wet papermaking method. After forming a nonwoven fabric, you may heat-process etc. as needed. By the step (ii), a nonwoven fabric in which glass fibers are bound with a binder is obtained.

In the second method, first, a nonwoven fabric is formed using glass fibers, for example, by a general wet papermaking method (step (I)). Next, the liquid containing the binder component is applied to the nonwoven fabric and then dried, thereby strengthening the connection between the glass fibers (step (II)). You may heat-process at the time of drying. The application of the binder may be performed by immersing the nonwoven fabric in the binder, or may be performed by impregnating the nonwoven fabric with the binder. In step (II), in order to suppress the formation of a film between the glass fibers, it is preferable to remove the excess binder after applying the binder.

The first method has an 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 glass fibers and a high effect can be obtained with a small amount of the binder.

Since the thickness of the polymer electrolyte membrane of the present invention is preferably 300 μm or less as described later, the glass nonwoven fabric combined therewith is also preferably thin within the range that exhibits the effect of improving the mechanical strength. The thickness (measured value at a pressure of 20 kP) is preferably 50 μm or less, and more preferably 30 μm or less. Further, the thickness of the glass nonwoven fabric is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of strength improvement. The thickness of the glass nonwoven fabric is an average value obtained by applying a uniform pressure (20 kPa) to the entire glass nonwoven fabric, measuring the thickness of about 10 arbitrary locations of the glass nonwoven fabric using a dial gauge.

The basis weight (mass per unit area) of the nonwoven fabric is preferably ² to 50 g / m ² , and more preferably 3 to 25 g / m ² . When the basis weight is less than 2 g / m ² , the entanglement between the glass fibers decreases, and the tensile strength tends to decrease. On the other hand, if the weight per unit area exceeds 50 g / m ² , the reinforcing material for the electrolyte membrane may become too thick. If the density is increased by a press or the like in order to reduce the thickness, the glass fiber may have its intersection. May break and shorten, and the tensile strength may decrease.

The glass nonwoven fabric preferably has a porosity of 80% or more, more preferably in the range of 85 to 95%, from the viewpoint of improving mechanical strength and minimizing a decrease in proton conductivity due to complexation. . The porosity of the glass nonwoven fabric can be calculated by calculating the specific gravity from the volume and weight of the glass nonwoven fabric and dividing this by the true specific gravity of the glass.

<3. Polymer electrolyte membrane>
The polymer electrolyte membrane of the present invention is a composite of the polymer electrolyte and the glass nonwoven fabric. That is, the polymer electrolyte membrane of the present invention has substantially no sulfonic acid group, a unit derived from a hydrophobic oligomer whose main chain is mainly composed of an aromatic ring group, and a sulfonic acid group. A polymer electrolyte membrane in which a polymer electrolyte having a main chain consisting of a unit derived from a hydrophilic oligomer whose chain is mainly composed of an aromatic ring group and a glass nonwoven fabric, wherein the glass nonwoven fabric has an average diameter Includes glass fibers of 1 μm or less and is treated with a silicon compound binder or an epoxy compound binder.

The composite of the polymer electrolyte and the glass nonwoven fabric means that both are integrated, that is, the glass nonwoven fabric is embedded in the polymer electrolyte. A conventionally known method can be applied to the composite method. As a simple method, a glass nonwoven fabric is fixed on a substrate such as glass, a polymer electrolyte solution is cast thereon, and the solvent is removed; first, the polymer electrolyte solution is cast on a glass substrate. A method of removing a solvent after placing a glass nonwoven fabric thereon and further casting a polymer electrolyte solution; by dipping the glass nonwoven fabric into the polymer electrolyte solution, the polymer electrolyte in the voids of the glass nonwoven fabric After the impregnation, a method of removing the solvent in a state where the glass nonwoven fabric containing the solution is spread in a vertical state is exemplified. Such a technique is generally a method used when producing a composite material of a nonwoven fabric and a resin. In addition, a method of thermocompression bonding a polymer electrolyte and a glass nonwoven fabric; a method of sandwiching a glass nonwoven fabric between two semi-solid polymer electrolytes containing a solvent, pressing, drying, and the like can also be applied.

The solvent can be removed by drying at a temperature of preferably 10 to 200 ° C, more preferably 40 to 150 ° C. When drying the glass nonwoven fabric containing the solution with a single sheet, it is preferable to set the drying temperature to about 45 to 130 ° C. and to dry for 1 to 20 hours. 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 include pyrrolidone and the like. As described above, the polymer electrolyte membrane of the present invention in which the polymer electrolyte and the glass nonwoven fabric are combined can be obtained.

As the polymer electrolyte, the aforementioned polymer electrolyte may be used alone, or other polymer electrolytes may be mixed and used. The polymer electrolyte membrane of the present invention may contain additives other than the polymer electrolyte and the glass nonwoven fabric. Examples include antioxidants for preventing resin degradation, and various additives such as antistatic agents and lubricants for improving handling in film forming processes, which affect the processing and performance of electrolyte membranes. It can be used as appropriate within the range not affected. From the viewpoint of proton conductivity, in the polymer electrolyte membrane of the present invention, the aforementioned polymer electrolyte is preferably a main component that accounts for 70% by weight or more of the entire polymer electrolyte membrane.

In addition, after obtaining the electrolyte membrane, a treatment such as biaxial stretching may be performed to control molecular orientation or the like, or a heat treatment may be performed to control crystallinity or residual stress. Furthermore, an appropriate chemical treatment may be performed during film formation. The chemical treatment includes, for example, crosslinking for increasing the strength of the electrolyte membrane, addition of a protic compound for increasing conductivity, addition of a trace amount of polyvalent metal ions for improving durability and ionic crosslinking, and the like. It is done. In any case, a polymer electrolyte membrane produced using the above-described polymer electrolyte in combination with a conventionally known technique is also included in the scope of the present invention.

As the thickness of the polymer electrolyte membrane, any thickness can be selected according to the application. 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 properties, handling properties, and resistance to tearing when bonded to the electrode, the polymer electrolyte membrane may be undesirably too thin. Considering these, the thickness of the polymer electrolyte membrane is preferably 5 μm or more, more preferably 10 μm or more, and preferably 300 μm or less, more preferably 100 μm or less. In the case where importance is attached to the output as a fuel cell, 10 μm or more and 50 μm or less are particularly preferable. If the thickness of the polymer electrolyte membrane is 5 μm or more and 300 μm or less, the production is easy, the membrane resistance and mechanical properties are balanced, and the handling property when processing as a fuel cell material is excellent. The thickness of the polymer electrolyte membrane can be determined by the measurement method described in the examples.

The ion exchange capacity (IEC) of the polymer electrolyte membrane can be adjusted by the IEC of the polymer electrolyte. For example, when the polymer electrolyte membrane contains a material other than the polymer electrolyte and the glass nonwoven fabric, the IEC as the polymer electrolyte membrane is thereby lowered, so that the IEC of the polymer electrolyte membrane is set to a higher value, etc. Yes.

The IEC of the polymer electrolyte membrane is 1.0 meq. / G or more, preferably 1.5 meq. / G or more, and 3.5 meq. / G or less, preferably 3.0 meq. / G or less is more preferable. IEC is 1.0 eq. If it is smaller than / g, high proton conductivity tends to be difficult to develop, and 3.5 meq. When it is larger than / g, mechanical strength decreases due to swelling with water, and it tends to be difficult to have sufficient strength. The IEC of the polymer electrolyte membrane can be determined by the measurement method described in the examples.

<4. Membrane / electrode assembly, fuel cell>
The membrane / electrode assembly for a fuel cell according to the present invention (hereinafter, the membrane / electrode assembly is referred to as “MEA”) is obtained by forming an electrode catalyst layer on the polymer electrolyte membrane of the present invention.

The electrode catalyst used in the present invention may literally be a conventionally known electrode catalyst for those skilled in the art, as long as it contains 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 active for the electrode reaction of the fuel cell is used. On the anode side, a catalyst having the ability to oxidize fuel (hydrogen, methanol, etc.) is used.

As the conductive catalyst carrier, a carbon carrier having a high surface area such as carbon black, ketjen black, activated carbon, carbon nanohorn, and carbon nanotube is preferable from the viewpoint of catalyst supporting ability, electronic conductivity, electrochemical stability, and the like.

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

The electrode catalyst layer can be prepared by first preparing a catalyst ink containing a polymer electrolyte, an electrode catalyst, and a solvent, applying the catalyst ink on a support, and removing the solvent. Examples of the polymer electrolyte used in the catalyst ink include perfluorocarbon sulfonic acid electrolytes used conventionally and hydrocarbon polymer electrolytes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, and sulfonated). Polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide). The solvent can be used without any limitation as long as it can dissolve the polymer electrolyte and does not poison the fuel cell catalyst.

The catalyst ink may contain additives such as a non-electrolyte binder, a water repellent, a dispersant, a thickener, and a pore former as necessary. In addition, those additives conventionally known to those skilled in the art can be used, and other specific configurations are not particularly limited.

For the catalyst ink prepared by the above composition and method, the following coating methods can be used depending on the viscosity and the type of substrate. The coating method may be any coating method known to those skilled in the art. For example, a method using a knife coater, bar coater, spray, dip coater, spin coater, roll coater, die coater, curtain coater, screen printing or the like. However, it is not limited to these. Other specific configurations are not particularly limited. When a polymer film is used as the substrate, a fuel cell catalyst layer transfer sheet can be produced, and when a conductive porous sheet is used as the substrate, a fuel cell gas diffusion electrode can be produced.

The MEA can be produced by a method such as applying the catalyst ink to the polymer electrolyte membrane of the present invention by the above method, or peeling the polymer film after the catalyst layer transfer sheet is pressure-bonded. The MEA can also be produced by attaching a conductive porous sheet to the polymer electrolyte membrane of the present invention.

Such an MEA can be used, for example, in a fuel cell, in particular, a polymer electrolyte fuel cell. A fuel cell using the polymer electrolyte membrane of the present invention is also included in the scope of the present invention.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. Embodiments obtained by appropriately combining the disclosed technical means also apply to the embodiments of the present invention. Included in the technical scope.

Hereinafter, examples will be shown, and the embodiment of the present invention will be described in more detail. The present invention is not limited to the following examples, and it goes without saying that various modes are possible for details.

Each measurement was performed as follows.
(Measurement of molecular weight)
The molecular weight was measured by GPC method. The conditions are as follows.
GPC measuring device: HLC-8220 (manufactured by Tosoh Corporation)
Column: Super AW 4000 and Super AW 2500 (made by Showa Denko KK) are connected in series. Column temperature: 40 ° C
Mobile phase solvent: NMP (N-methylpyrrolidone, LiBr added to 10 mmol / dm ³ )
Solvent flow rate: 0.3 mL / min
Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation)
Hereinafter, the number average molecular weight converted with standard polystyrene is expressed as Mn, and the weight average molecular weight converted with standard polystyrene is expressed as Mw.

(Measurement of polymer electrolyte membrane thickness)
Using a digital thickness meter (PDN-20) manufactured by Peacock, the thickness of 9 positions of the polymer electrolyte membrane was measured, and the average value was defined as the thickness.

(Measurement of ion exchange capacity)
As a measurement sample, 10 to 20 mg of the membrane after acid treatment was cut out and 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 group from H ⁺ type to Na ⁺ type. Thereafter, HCl contained in the obtained solution was quantified with a 0.01 M NaOH aqueous solution using an automatic potentiometric titrator AT-510 (manufactured by Kyoto Electronics Industry Co., Ltd.), and the ion exchange capacity IEC value was calculated using the following equation. 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 to about 2 cm × 3 cm was prepared and immersed in pure water at room temperature for 6 hours. The sample immediately after the immersion and the sample that was vacuum dried at 100 ° C. for 2 hours to be completely dried were measured for the dimensional change and weight in the plane direction and the vertical direction, and the rate of change was calculated. Regarding the planar direction, the dimensional change of the four sides was measured, and the average value was taken as the result. In the vertical direction (film thickness direction), the dimensional change at three points in the plane was measured, and the average value was taken as the result.

(Evaluation of wet and dry cycle resistance)
A sample of a polymer electrolyte membrane cut to about 6.5 cm × 6.5 cm was prepared, and a sample was prepared by placing a silicon packing and a gas diffusion layer (manufactured by SGL Carbon) on both sides. This sample was incorporated into a commercially available Japan Automobile Research Institute (JARI) standard fuel cell, and fixed with a fastening pressure of 4 N · m using 8 screws. A pressure of 0.2 MPa was applied to this cell with nitrogen gas, and it was confirmed that there was no leakage because the pressure did not decrease for 15 minutes. In the characteristic evaluation, hydrogen was supplied to one side of the cell and argon was supplied to the other side at a flow rate of 30 ml / min. Each gas was exchanged at 80 ° C. while maintaining a dry state (0% RH) and a wet state (100% RH) for 2 minutes, and a dry and wet cycle test was performed. The amount of hydrogen permeated to the argon side through the polymer electrolyte membrane was quantified by gas chromatography every three cycles. As a result, the number of cycles until the hydrogen permeation coefficient suddenly increased due to the membrane breakage was obtained.

(Used glass nonwoven fabric)
A glass nonwoven fabric having the characteristics shown in Table 1 was prepared and used.

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

(Production Example 2)
To a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube, 4,4′-dichlorodiphenylsulfone (31.6 g, 110 mmol), 4,4′-dihydroxybenzophenone (21.4 g, 100 mmol), potassium carbonate ( 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 generated water. 4,4′-Dichlorodiphenylsulfone (0.5 g) was added, and the mixture was further stirred for 5 hours. The mixture was filtered using 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 with 500 mL of pure water twice at 60 ° C., then once with 500 mL of methanol at 60 ° C., and overnight under reduced pressure at 70 ° C. It dried and obtained 41.5g of hydrophobic part oligomers of the following Formula. The molecular weight by GPC was Mn = 5,400 and Mw = 13,900.

(Production Example 3)
Into a 1 L four-necked flask equipped with a mechanical stirrer, reflux tube, and DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 1 (24 g, 52.7 mmol) and the hydrophobic part oligomer obtained in Production Example 2 ( 16 g), dimethyl sulfoxide (480 mL), and toluene (120 mL) were added to a nitrogen atmosphere and heated to 170 ° C. for 3 hours for azeotropic dehydration. After toluene was distilled off 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. The reaction solution was poured into 700 mL of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (600 mL), and further repeatedly washed with pure water until the pH of the washing solution became 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain a polymer electrolyte of the following formula (33.2 g). 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 concentration of about 12%. As shown in Comparative Example 1, the obtained polymer electrolyte was formed into a single film and its molecular weight was measured by GPC. As a result, Mn = 85,100 and Mw = 177,000. The ion exchange capacity is 2.06 meq. / G.

Example 1
On the glass plate, the polymer electrolyte solution prepared in Production Example 3 was applied with a bar coater. On the coating film, glass nonwoven fabric A (11 cm × 10 cm) in Table 1 was gently placed so that bubbles were not mixed, and then the polymer electrolyte solution of Production Example 3 was applied again with a bar coater. The obtained composite film was dried at 120 ° C. for 12 hours using a hot plate while being applied to a glass substrate. The membrane was removed from the glass plate, washed with 6N hydrochloric acid and then with distilled water, wiped off with water on the surface, and dried at 60 ° C. for 30 minutes to obtain a polymer electrolyte membrane A. The thickness, ion exchange capacity, and swelling rate of the polymer electrolyte membrane A were measured by the methods described above. The results are summarized in Table 2.

(Examples 2 to 7)
Polymer electrolyte membranes B to G were obtained in the same manner as in Example 1 except that the glass nonwoven fabrics B to G were used. The thickness, ion exchange capacity, swelling rate, and wet / dry cycle resistance of the polymer electrolyte membrane were measured by the methods described above. The results are summarized in Table 2. Moreover, the result of the wet and dry cycle resistance test of the polymer electrolyte membrane F is shown in FIG.

(Comparative Example 1)
An electrolyte membrane was produced using the polymer electrolyte solution of Production Example 3 without using a glass nonwoven fabric. Thickness, ion exchange capacity, swelling rate, and wet / dry cycle resistance were measured by the methods described above. The results are summarized in Table 2. Further, the results of the wet and dry cycle resistance test are shown in FIG. 1 in comparison with the polymer electrolyte membrane F.

(Comparative Example 2)
A polymer electrolyte membrane H was obtained in the same manner as in Example 1 except that the glass nonwoven fabric H was used. The thickness, ion exchange capacity, swelling rate, and wet / dry cycle resistance of the polymer electrolyte membrane were measured by the methods described above. The results are summarized in Table 2.

In each example, the glass fiber has an average diameter of 1 μm or less, or a mixture of an average diameter of 1 μm or less and an average diameter of more than 1 μm and less than 10 μm, and is treated with a binder. The glass nonwoven fabric which is being used is used. Comparative Example 1 is a non-reinforced film that does not use a glass nonwoven fabric. In Comparative Example 2, a glass fiber having an average diameter of 1 μm or less is used, but a glass nonwoven fabric that is not surface-treated with a binder is used. It can be seen that the polymer electrolyte membrane of each example has improved swelling resistance and wet / dry cycle resistance compared to each comparative example.

Claims (9)

A unit derived from a hydrophobic part oligomer having a main chain mainly composed of an aromatic ring group and having substantially no sulfonic acid group, and a hydrophilic part having a sulfonic acid group and the main chain mainly composed of an aromatic ring group A polymer electrolyte membrane comprising a polymer electrolyte having a unit derived from an oligomer as a main chain and a glass nonwoven fabric,
A polymer electrolyte membrane, wherein the glass nonwoven fabric includes glass fibers having an average diameter of 1 μm or less and is treated with a silicon compound binder or an epoxy compound binder. The polymer electrolyte membrane according to claim 1, wherein the glass nonwoven fabric further comprises glass fibers having an average diameter of more than 1 µm and less than 10 µm. 3. The polymer electrolyte membrane according to claim 1, wherein the glass nonwoven fabric is treated with an epoxy compound binder. The polymer electrolyte membrane according to any one of claims 1 to 3, wherein the unit derived from the hydrophilic part oligomer contains at least one of the structures described in the following general formula group (1) as a repeating unit. .

(In the formula, Ar ¹ represents a divalent group having any of the structures described in the following formula group (2), .Ar ² may have a substituent group of the divalent groups, A divalent aromatic group having at least one sulfonic acid group, when there are a plurality of Ar ¹ or Ar ^{2 s} , they may be the same or different, n is an integer of 1 to 4, X represents —O— or —S—, and Y represents —SO ₂ — or —CO—.

The Ar ² is a divalent aromatic group having any one of the structures described in the following formula group (3) and having at least one sulfonic acid group. Polymer electrolyte membrane.

6. The polymer electrolyte membrane according to claim 1, wherein the unit derived from the hydrophobic moiety oligomer includes at least one of the structures described in the following general formula group (4) as a repeating unit. .

(In the formula, Ar represents a divalent aromatic group. When a plurality of Ar are present, they may be the same or different.) The ion exchange capacity is 1.5 to 3.5 meq. It is / g, The polymer electrolyte membrane in any one of Claims 1-6 characterized by the above-mentioned. A membrane / electrode assembly for a fuel cell using the polymer electrolyte membrane according to claim 1. A fuel cell using the polymer electrolyte membrane according to claim 1.

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