JP2005350658A - Polymer electrolyte material, and polymer electrolyte membrane, membrane electrode assembly and polymer electrolyte fuel cell produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte material having excellent solvent resistance and high proton conductivity as well as low fuel crossover and giving a polymer electrolyte fuel cell achieving high output and high energy density, and a polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel cell composed of the electrolyte material. <P>SOLUTION: The polymer electrolyte material is at least composed of a hydrocarbon polymer having an ionic group and a heterocyclic polymer wherein the haze of the polymer electrolyte material is ≤30% in hydrated state. The polymer electrolyte membrane, the membrane electrode assembly and the polymer electrolyte fuel cell are produced by using the polymer electrolyte material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte material excellent in practical use capable of achieving high output and high energy capacity, and a polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel cell using the same. .

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low environmental burden. For this reason, it is in the spotlight again in recent years to the protection of the global environment. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and portable devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel metal hydride batteries and lithium ion batteries.

  In polymer electrolyte fuel cells, in addition to conventional polymer electrolyte fuel cells that use hydrogen gas as fuel (hereinafter referred to as PEFC), direct methanol fuel cells that supply methanol directly (hereinafter referred to as DMFC) It is also attracting attention. Although the DMFC has a lower output than the conventional PEFC, the fuel is liquid and does not use a reformer. Therefore, the energy density is high and the usage time of the portable device per filling is long. is there.

  In a fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs and an electrolyte membrane serving as an ionic conductor between the anode and the cathode constitute a membrane-electrode complex (MEA), and this MEA is separated by a separator. The sandwiched cell is configured as a unit. Here, the electrode is composed of an electrode substrate (also referred to as a gas diffusion electrode or a current collector) that promotes gas diffusion and collects (supply) electricity, and an electrode catalyst layer that actually becomes an electrochemical reaction field. ing. For example, in an anode electrode of a polymer electrolyte fuel cell, a fuel such as hydrogen gas reacts with a catalyst layer of the anode electrode to generate protons and electrons, and the electrons are conducted to the electrode substrate, and the protons flow to the polymer electrolyte membrane. Conducted with. For this reason, the anode electrode is required to have good gas diffusibility, electron conductivity, and ion conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air is reacted with protons conducted from the polymer electrolyte membrane and electrons conducted from the electrode base material in the catalyst layer of the cathode electrode to produce water. For this reason, in the cathode electrode, it is necessary to efficiently discharge the generated water in addition to gas diffusibility, electron conductivity, and ion conductivity.

  In particular, among polymer electrolyte fuel cells, the polymer electrolyte membrane for DMFC using an organic solvent such as methanol as the fuel has the performance required for the conventional polymer electrolyte membrane for PEFC using hydrogen gas as the fuel. In addition, fuel permeation suppression such as methanol is also required. Methanol permeation of the polymer electrolyte membrane, also called methanol crossover (MCO) or chemical short, causes a problem that the battery output and energy efficiency are lowered.

  In the past, for example, “Nafion” (“Nafion”, a registered trademark of DuPont), which is a perfluorosulfonic acid polymer, has been used in an electrolyte membrane of a polymer electrolyte fuel cell. However, “Nafion” is a perfluoro polymer produced through multi-step synthesis, so it is very expensive, and in order to form a cluster structure, it has a high affinity with water such as methanol. There is a problem that the fuel easily permeates the electrolyte membrane, that is, the fuel crossover is large. In addition, there is a problem that the mechanical strength of the film is reduced due to swelling, a problem of disposal treatment after use, and a problem that recycling of the material is difficult. Therefore, in order to put these polymer electrolyte fuel cells into practical use, polymer electrolyte materials that are inexpensive and have suppressed fuel crossover have been desired from the market.

  Some efforts have already been made on polymer electrolyte materials based on non-perfluoropolymers. In the 1950s, styrene-based cation exchange resins were studied. However, since the strength as a membrane, which is a form when used in a normal fuel cell, was not sufficient, a sufficient battery life could not be obtained.

  A fuel cell using a sulfonated aromatic polyetheretherketone as a polymer electrolyte material has also been studied. For example, it is known that aromatic polyetheretherketone (hereinafter sometimes abbreviated as PEEK), which is sparingly soluble in organic solvents, becomes soluble in organic solvents and becomes easy to form when highly sulfonated. (See Non-Patent Document 1). However, these sulfonated PEEKs simultaneously improve hydrophilicity, become water-soluble, or cause a decrease in strength during water absorption. The fuel cell usually produces water as a by-product by the reaction of fuel and oxygen, or in DMFC, the fuel itself is a methanol aqueous solution. Therefore, when such sulfonated PEEK becomes water-soluble, the electrolyte for the fuel cell is used as it is. Not suitable for use.

  Non-Patent Document 2 describes PSF (UDELP-1700), which is an aromatic polyethersulfone, and a sulfonated product of PES (see Non-Patent Document 2). This document describes that sulfonated PSF is completely water-soluble and cannot be evaluated as an electrolyte. Further, in this document, although sulfonated PES is not water-soluble, the introduction of a crosslinked structure is proposed because of the problem of high water absorption.

  As described above, none of the polymer electrolyte materials known so far does not satisfy all of the above-mentioned high proton conductivity, fuel crossover suppression effect, and economic efficiency, but is a polymer electrolyte material that satisfies higher requirements. Development was awaited.

  As an attempt to satisfy this requirement, a composite of a polymer having an ionic group and another polymer has been proposed. This method is simple and more convenient than copolymerization or IPN (Interpenetrating Polymer Network). Uniform polymer blends mixed at the molecular level have the potential to create new materials that are completely different in nature from any of the original polymers. However, it is very rare for different polymers to mix uniformly. In general, polymers are not homogeneously mixed even if prepared using the same solvent. Among them, the polymer having an ionic group is usually hydrophilic, while the polymer capable of suppressing swelling in an aqueous fuel solution such as methanol is hydrophobic, so that these two different polymers are uniformly mixed. Such an example has not been published so far.

  Also, if the polymers do not mix uniformly, the blend will phase separate resulting in insufficient mechanical strength. Even in the case of micro phase separation, in most cases, insufficient interaction occurs between phases, or the properties of the original polymer are reflected, and a sufficient fuel crossover suppression effect cannot be obtained.

  Some efforts have already been made for blended polymer electrolyte materials. For example, a polymer electrolyte material in which sulfonated polyphenylene oxide (hereinafter sometimes abbreviated as S-PPO) and polyvinylidene fluoride (hereinafter sometimes abbreviated as PVDF) are blended at various mixing ratios is introduced. (Patent Document 1). A polymer electrolyte material obtained by blending a block copolymer having a sulfonic acid group and an aromatic polyimide has also been introduced (Patent Document 2). However, in this document, these blend electrolyte materials are described as being translucent, white or light yellow opaque, and there is no description about methanol crossover, etc., but having such a phase separation structure and large haze. As far as we know, blend electrolyte materials cannot be expected to have a sufficient methanol crossover suppression effect.

  Furthermore, a fuel cell is usually formed by forming a polymer electrolyte material on an electrode layer. Conventionally, in order to integrally form an electrode and a polymer electrolyte material, a carbon carrying a hydrogen reduction catalyst is prepared in advance, the catalyst paste is applied to carbon paper, a heat treated electrode layer is formed, and a film-like polymer is formed. The electrolyte material was sandwiched between two electrode layers and molded by hot pressing to perform three-layer joining of anode / polymer electrolyte membrane / cathode.

  However, in such a three-layer joining method, there are technical problems such as inferior adhesion of each layer, and it takes time to integrate the three layers, and each layer is formed individually and is not suitable for mass production. there were. In addition, the polymer electrolyte material based on a hydrocarbon-based polymer has a problem that the thermoplasticity of the polymer is insufficient, the interface resistance with the electrode layer is large, and sufficient power generation characteristics cannot be obtained.

Therefore, a method has been proposed in which after the polymer electrolyte membrane is formed, a catalyst paste is applied onto the polymer electrolyte membrane and dried. However, the above-mentioned polymer electrolyte material based on a hydrocarbon-based polymer has a problem that when the catalyst paste is applied, the film dissolves or cracks or deformation occurs, and the power generation performance is not sufficiently exhibited. there were. For this reason, in order to put a polymer electrolyte fuel cell into practical use, it has been desired to develop a polymer electrolyte material that is inexpensive, easy to mold, and excellent in solvent resistance.
"Polymer", 1987, vol. 28, 1009. "Journal of Membrane Science", 83 (1993) 211-220. JP 2002-294087 A JP 2002-260687 A

  In view of the background of the prior art, the present invention achieves both high proton conductivity and low fuel crossover, excellent solvent resistance, and high output and high energy density when used as a polymer electrolyte fuel cell. It is an object of the present invention to provide a polymer electrolyte material that can be achieved, and a polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel cell comprising the same.

  The present invention employs the following means in order to solve the above problems. That is, the polymer electrolyte material of the present invention is a polymer electrolyte material comprising at least a hydrocarbon polymer having an ionic group and a heterocyclic polymer, and the haze of the water content of the polymer electrolyte material is 30% or less. It is characterized by being. In addition, the polymer electrolyte membrane, the membrane electrode assembly, and the polymer electrolyte fuel cell of the present invention are configured using such a polymer electrolyte material.

  According to the present invention, a polymer electrolyte material excellent in practicality capable of achieving a high output and a high energy capacity, which has both high proton conductivity and low fuel crossover, excellent solvent resistance, and production thereof It is possible to provide a method, and a high-performance polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel cell using the method.

  The present invention achieves the above-mentioned problems, that is, high proton conductivity and low fuel crossover, excellent solvent resistance, and achieves high output and high energy density when used as a polymer electrolyte fuel cell. In the polymer electrolyte material comprising at least a hydrocarbon polymer having an ionic group and a heterocyclic polymer, the polymer electrolyte material is transparent in a water-containing state. It has been sought to solve such a problem all at once when it is close to or insoluble in a hot solvent.

  The polymer electrolyte material of the present invention is characterized by comprising at least a hydrocarbon-based polymer having an ionic group and a heterocyclic polymer, and the haze of the polymer electrolyte material in a water-containing state is 30% or less. .

  The inventors of the present invention provide a polymer electrolyte material comprising at least a hydrocarbon polymer having an ionic group and a heterocyclic polymer, and having a water-containing haze of 30% or less, achieving both high proton conductivity and suppression of fuel crossover. And the membrane performance of the polymer electrolyte material was found to be influenced by the uniformity and transparency of the polymer electrolyte material, that is, the haze in a water-containing state, and the present invention was reached.

  The water-containing haze as used in the present invention is a value measured as follows. As a sample, a polymer electrolyte membrane immersed in pure water at 25 ° C. for 24 hours was used as a sample. After wiping off water droplets on the surface, a fully automatic direct reading haze computer (manufactured by Suga Test Instruments Co., Ltd.): HGM-2DP). The film thickness can be arbitrarily selected within the range of 10 to 500 μm.

  Further, the hydrocarbon polymer having an ionic group in the present invention means a polymer having an ionic group other than a perfluoro polymer. Here, the perfluoro polymer means a polymer in which most or all of the hydrogen atoms of the alkyl group and / or alkylene group in the polymer are substituted with fluorine atoms. In the present specification, a polymer in which 85% or more of hydrogen of an alkyl group and / or an alkylene group in a polymer is substituted with a fluorine atom is defined as a perfluoro polymer. Representative examples of the perfluoro polymer having an ionic group of the present invention include Nafion (R) (manufactured by DuPont), Flemion (R) (manufactured by Asahi Glass) and Aciplex (R) (manufactured by Asahi Kasei). A commercial item can be mentioned. The structure of the perfluoro polymer having these ionic groups can be represented by the following general formula (N1).

[In formula (N1), n ₁ and n ₂ each independently represents a natural number. k ₁ and k ₂ each independently represent an integer of 0 to 5. ]
In the perfluoro-based polymer having these ionic groups, a hydrophobic portion and a hydrophilic portion in the polymer form a clear phase structure, so that a water channel called a cluster is formed in the polymer in a water-containing state. In such a water channel, fuel such as methanol can easily move, and a reduction in fuel crossover cannot be expected.

  On the other hand, the present invention comprises at least a hydrocarbon polymer having an ionic group and a heterocyclic polymer, and can suppress both the water content haze to 30% or less, and can achieve both high proton conductivity and low fuel crossover. is there. In the polymer electrolyte material of the present invention, the cause of the fuel crossover reduction such as methanol is not clear at this stage, but is presumed as follows. That is, the molecular chain of a polymer having an ionic group that easily swells in an aqueous fuel solution such as methanol is mixed with a rigid heterocyclic polymer that does not swell at all in an aqueous fuel solution such as methanol at the molecular level. It is presumed that the polymer electrolyte is restrained at the molecular level, the swelling of the polymer electrolyte material with respect to the aqueous fuel solution such as methanol is suppressed, the fuel crossover is reduced, and the strength of the membrane is also suppressed.

  That is, when a conventional polymer having an ionic group is used alone as a polymer electrolyte material, if the content of the ionic group is increased in order to increase proton conductivity, the polymer electrolyte material swells and a large amount is formed inside. Water clusters are easily formed, and so-called free water increases in the polymer electrolyte material. In such free water, the movement of fuel such as methanol is easily performed, so that the crossover of fuel such as methanol is difficult to be suppressed.

  The polymer electrolyte material composed of the hydrocarbon polymer having an ionic group and the heterocyclic polymer of the present invention is preferably mixed with a compatibilizing agent as necessary in order to make both of these polymers compatible. That is, since the polymer electrolyte material of the present invention is expected to exhibit homogeneity with respect to characteristics such as optical transparency, it is necessary to control the haze of its water content to 30% or less, and further, proton conduction More preferably, the haze in the water-containing state is controlled to 20% or less from the viewpoint of the property and the effect of suppressing the fuel crossover. When the haze in the water-containing state exceeds 30%, the hydrocarbon polymer having an ionic group and the heterocyclic polymer are not uniformly mixed and phase-separated, the influence between these phases, or the original The properties of the polymer having an ionic group are reflected, and sufficient proton conductivity, fuel crossover suppressing effect, and solvent resistance cannot be obtained. In addition, the properties of the heterocyclic polymer are also reflected, and sufficient proton conductivity may not be obtained. Further, from the viewpoint of positioning of the anode electrode and the cathode electrode with respect to the polymer electrolyte membrane during the production of the membrane electrode composite, it is more preferable to use a polymer electrolyte membrane having a water-containing haze of 30% or less.

  Such a polymer electrolyte material of the present invention is excellent in solvent resistance from the viewpoint of production cost and fuel crossover suppression effect, that is, a weight loss after being immersed in N-methylpyrrolidone at 50 ° C. for 5 hours is 30% by weight. The following is more preferable. More preferably, the weight loss is 20% by weight or less. If the weight loss exceeds 30%, the fuel crossover suppression effect is insufficient, or it becomes difficult to apply a catalyst paste directly to the polymer electrolyte membrane to produce a membrane electrode assembly, resulting in production costs. Not only increases, but also the interface resistance with the catalyst layer increases, and sufficient power generation characteristics may not be obtained.

  The weight loss of the polymer electrolyte material relative to N-methylpyrrolidone is measured by the following method.

That is, a polymer electrolyte material (about 0.1 g) serving as a specimen is washed with pure water and then vacuum-dried at 40 ° C. for 24 hours to measure the weight. The polymer electrolyte material was immersed in N- methylpyrrolidone 1000 times by weight, in a closed vessel, with stirring 50 ° C., heated for 5 hours. Next, filtration is performed using filter paper (No. 2) manufactured by Advantech. At the time of filtration, the filter paper and the residue are washed with the same solvent 1000 times weight, and the eluate is sufficiently eluted in the solvent. Weight loss is calculated by vacuum drying the residue at 40 ° C. for 24 hours and measuring the weight.

  By the way, normally, hydrocarbon polymers having ionic groups are difficult to melt and form due to the low heat resistance of the ionic groups. It is preferable to form a film, and it is preferable to be soluble in a solvent.

  On the other hand, as a method for providing a catalyst layer on the polymer electrolyte membrane, a method of directly applying a catalyst paste to the polymer electrolyte membrane is considered to be more preferable from the viewpoint of reducing interface resistance. When the polymer electrolyte membrane is inferior in properties, the membrane often dissolves, cracks or deforms, and the original membrane performance cannot be expressed in many cases. Furthermore, when the polymer electrolyte membrane is a laminated film, a method of directly applying the following polymer solution directly to the polymer electrolyte membrane is widely adopted. There was a problem that performance could not be expressed.

  On the other hand, the polymer electrolyte material excellent in solvent resistance of the present invention hardly swells with respect to N-methylpyrrolidone, can reduce the interface resistance with the catalyst layer, and greatly increases the production cost. This is considered to be an excellent polymer electrolyte material that can be reduced.

  In the polymer electrolyte material of the present invention, the composition ratio of the hydrocarbon polymer having an ionic group and the heterocyclic polymer is based on the total amount of the hydrocarbon polymer having an ionic group and the heterocyclic polymer. More preferably, it contains 20 to 80% by weight of the heterocyclic polymer. If the amount of the heterocyclic polymer is less than 20% by weight, the fuel crossover suppressing effect and the solvent resistance may be insufficient. If the amount exceeds 80% by weight, sufficient proton conductivity is obtained. There is no tendency.

  Next, the hydrocarbon polymer having an ionic group used in the present invention will be described. In the present invention, as the hydrocarbon polymer having such an ionic group, two or more kinds of polymers may be used simultaneously.

  The ionic group used in the present invention is not particularly limited as long as it is a negatively charged atomic group, but is preferably one having proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group are preferably used. Here, the sulfonic acid group is a group represented by the following general formula (f1), the sulfonimide group is a group represented by the following general formula (f2) [wherein R represents an arbitrary atomic group. The sulfuric acid group is represented by the following general formula (f3), the phosphonic acid group is represented by the following general formula (f4), and the phosphoric acid group is represented by the following general formula (f5) or (f6). And the carboxylic acid group means a group represented by the following general formula (f7).

Such ionic groups include cases where the functional groups (f1) to (f7) are salts. Examples of the cation forming the salt include an arbitrary metal cation, NR ₄ ⁺ (R is an arbitrary organic group), and the like. In the case of a metal cation, the valence and the like are not particularly limited and can be used. Specific examples of preferable metal ions include Li, Na, K, Rh, Mg, Ca, Sr, Ti, Al, Fe, Pt, Rh, Ru, Ir, and Pd. Among these, Na and K which are inexpensive and can be easily proton-substituted are more preferably used as the polymer electrolyte material.

  Two or more kinds of these ionic groups can be contained in the polymer electrolyte material, and may be preferable by combining them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least a sulfonic acid group, a sulfonimide group, and a sulfuric acid group from the viewpoint of high proton conductivity, and most preferable to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance.

  The amount of sulfonic acid group in the polymer electrolyte material can be shown as a value of sulfonic acid group density (mmol / g). The sulfonic acid group density of the polymer electrolyte material in the present invention is preferably 0.1 to 5.0 mmol / g, more preferably 0.5 to 5.0 in terms of proton conductivity, fuel crossover, and mechanical strength. 3.0 mmol / g, and most preferably 0.8 to 2.0 mmol / g from the point of fuel crossover. When the sulfonic acid group density is lower than 0.1 mmol / g, sufficient proton generation characteristics may not be obtained due to low proton conductivity. In addition, sufficient water resistance and mechanical strength when containing water may not be obtained.

  Here, the sulfonic acid group density is the number of moles of sulfonic acid groups introduced per gram of the polymer electrolyte material, and the larger the value, the greater the amount of sulfonic acid groups. The sulfonic acid group density can be determined by elemental analysis or neutralization titration. Among these, the elemental analysis method is preferably used from the viewpoint of easiness of measurement, but when a sulfur source other than the sulfonic acid group is included, the sulfonic acid group density can also be obtained by a neutralization titration method.

  As the polymer having an ionic group used in the present invention, a hydrocarbon-based polymer is more preferably used from the viewpoint of the fuel crossover suppressing effect and the production cost. When a perfluoro-based polymer such as “Nafion” (R) (manufactured by DuPont) is used, as described above, it is expensive and has a limit to the fuel crossover suppression effect because it forms a cluster structure. Therefore, it is very difficult to put a polymer electrolyte fuel cell that requires a high energy capacity into practical use.

  In addition, as the hydrocarbon-based polymer having an ionic group used in the present invention, a solvent-soluble non-crosslinked polymer is more preferably used from the viewpoint of ease of molding and production cost.

  Here, the cross-linked polymer means a polymer that has substantially no fluidity to heat or a polymer that is substantially insoluble in a solvent. Further, the non-crosslinked polymer means that it is not a crosslinked polymer. The determination is made by the following method.

  A sample polymer (about 0.1 g) is washed with pure water and then vacuum dried at 40 ° C. for 24 hours to measure the weight. The polymer is immersed in a 100-fold weight solvent and heated in a sealed container at 70 ° C. for 40 hours with stirring. Next, filtration is performed using filter paper (No. 2) manufactured by Advantech. During filtration, the filter paper and the residue are washed with the same solvent of 100 times weight, and the eluate is sufficiently eluted in the solvent. Dry the filtrate and determine the weight of the elution. When the elution weight is less than 10% of the initial weight, it is determined to be substantially insoluble in the solvent. This test was carried out for five types of solvents such as toluene, hexane, N-methylpyrrolidone, methanol and water. When it was determined that all the solvents were substantially insoluble, the polymer was determined to be a crosslinked polymer, Those that are not polymers are determined as non-crosslinked polymers.

Examples of the hydrocarbon polymer having an ionic group are illustrated in (E-1) and (E-2) below.
(E-1) Polymer obtained from vinyl polymerization monomer, for example, acrylic acid, methacrylic acid, vinyl benzoic acid, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, maleic acid, 2-acrylamido-2-methylpropane sulfone Examples thereof include a polymer obtained from a vinyl polymerization monomer having an ionic group represented by acid, sulfopropyl (meth) acrylate, ethylene glycol methacrylate phosphate and the like. A polymer obtained by copolymerizing such a vinyl polymerization monomer having an ionic group and a monomer having no ionic group is also suitable.

  As the monomer having no ionic group, any compound having a vinyl polymerizable functional group can be used without particular limitation. Preferably methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid ester compounds such as benzyl acid, 2-hydroxyethyl (meth) acrylate, styrene compounds such as styrene, α-methylstyrene, aminostyrene, chloromethylstyrene, (meth) acrylonitrile, (meth) Males such as (meth) acrylamide compounds such as acrylamide, N, N-dimethylacrylamide, N-acryloylmorpholine, N-methylacrylamide, N-phenylmaleimide, N-benzylmaleimide, N-cyclohexylmaleimide, N-isopropylmaleimide Bromide based compounds.

  A polymer obtained by introducing an ionic group into a polymer obtained from a vinyl polymerization monomer having no ionic group is also suitable. As a method for introducing an ionic group, a known method can be applied. For example, first, a phosphonic acid group can be introduced by a method described in Polymer Preprints, Japan, 51, 750 (2002), etc. It is. Next, introduction of a phosphate group is possible by, for example, phosphoric esterification of a polymer having a hydroxyl group. Carboxylic acid groups can be introduced, for example, by oxidizing a polymer having an alkyl group or a hydroxyalkyl group. The introduction of a sulfate group is possible by, for example, sulfate esterification of a polymer having a hydroxyl group. As a method for introducing a sulfonic acid group, for example, a method described in JP-A-2-16126 or JP-A-2-208322 is known. Specifically, for example, the polymer is sulfonated by reacting with a sulfonating agent such as chlorosulfonic acid in a halogenated hydrocarbon solvent such as chloroform, or by reacting in concentrated sulfuric acid or fuming sulfuric acid. Can do. The sulfonating agent is not particularly limited as long as it can sulfonate a polymer, and in addition to the above, sulfur trioxide and the like can be used. For example, a polymer having an epoxy group can be sulfonated by the method described in J. Electrochem. Soc., Vol. 143, No. 9, 2795-2799 (1996). When the polymer is sulfonated by these methods, the degree of sulfonation can be easily controlled by the amount of the sulfonating agent used, the reaction temperature and the reaction time. Introduction of a sulfonimide group into an aromatic polymer can be achieved, for example, by a method of reacting a sulfonic acid group and a sulfonamide group.

  If the polymer having such an ionic group is a crosslinked polymer, it is advantageous for suppressing fuel crossover, but the production cost is often increased. When the polymer obtained from the vinyl polymerization monomer is crosslinked, a vinyl polymerization monomer having a plurality of polymerizable functional groups may be copolymerized as a crosslinking agent. Some examples of vinyl polymerization monomers having a plurality of vinyl polymerizable functional groups include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (Meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol (Meth) acrylate compounds such as tetra (meth) acrylate and dipentaerythritol poly (meth) acrylate, dibilbenzene, divinylnaphthalene, dibi Styrene compounds such as Le biphenyl, methylenebis (meth) acrylamide (meth) acrylamide compound, phenylene bismaleimide, p, p'-oxybis (phenyl -N- maleimide) a maleimide-based compounds such as.

  In the case of producing a polymer obtained from such a vinyl polymerization monomer, the monomer composition includes a thermal polymerization initiator typified by a peroxide type or an azo type, or a photopolymerization initiator in order to facilitate polymerization. Is generally added.

  In the case of performing thermal polymerization, one having an optimum decomposition characteristic for a desired reaction temperature is selected and used. In general, a peroxide-based initiator having a 10-hour half-life temperature of 40 to 100 ° C. is suitable, and a polymer electrolyte material free from cracks can be produced with such an initiator.

  Examples of the photopolymerization initiator include a carbonyl compound such as benzophenone and an amine combined system, a mercaptan compound, a disulfide compound, and the like.

  These polymerization initiators are used alone or in combination, and are used in an amount of up to about 1% by weight.

  As a polymerization method and a molding method, known methods can be used. For example, there are a method of polymerizing a monomer composition formed into a thin film by a method such as inter-plate polymerization and coating in an inert gas or a reduced-pressure atmosphere.

As an example, the interplate polymerization method will be described below. First, the monomer composition is filled in the gap between two plate molds. Then, photopolymerization or thermal polymerization is performed to form a film. The plate-shaped mold is made of resin, glass, ceramics, metal, etc., but in the case of photopolymerization, an optically transparent material is used, and usually resin or glass is used. If necessary, a gasket having the purpose of giving a certain thickness to the film and preventing liquid leakage of the filled monomer composition may be used in combination. The plate mold in which the monomer composition is filled in the voids is subsequently irradiated with actinic rays such as ultraviolet rays, or is heated in an oven or a liquid tank to be polymerized. There may be a method in which both heat polymerization is carried out after photopolymerization, or conversely, photopolymerization after heat polymerization is used in combination. In the case of photopolymerization, it is common to irradiate light containing a large amount of ultraviolet light using, for example, a mercury lamp or insect trap as a light source for a short time (usually 1 hour or less). When thermal polymerization is performed, the temperature is gradually raised from around room temperature and the temperature is raised to 60 ° C. to 200 ° C. over several hours to several tens of hours, maintaining uniformity and quality, and reproducibility. Is preferred to enhance.
(E-2) Polymer having an anionic group and having an aromatic ring in the main chain A polymer having an aromatic ring in the main chain (hereinafter sometimes referred to as an aromatic hydrocarbon polymer), which is an ionic group It is what has.

  The main chain structure is not particularly limited as long as it has an aromatic ring, but a material having sufficient mechanical strength such as used as an engineering plastic is preferable. For example, polyphenylene polymers described in US Pat. No. 5,403,675, Japanese Patent Application Laid-Open No. 2001-192531, and Japanese Patent Application Laid-Open No. 2002-293889 are suitable examples.

  Furthermore, a polymer having at least one polar group different from the ionic group in the main chain is preferable. The reason for this is presumed to be that high proton conductivity can be provided and fuel crossover can be reduced by promoting the coordination of water in the vicinity of the main chain and increasing the amount of antifreeze water.

Although it does not specifically limit with a polar group, The functional group which can coordinate water is preferable. Examples of such a polar group include a sulfonyl group represented by the following general formula (g1), an oxy group represented by the general formula (g2), a thio group represented by the general formula (g3), and a general formula (g4). A carbonyl group represented by formula, a phosphine oxide group represented by formula (g5) (wherein R ¹ represents a monovalent organic group), a phosphonate ester group represented by formula (g6) (formula R ² represents a monovalent organic group), an ester group represented by the general formula (g7), an amide group represented by the general formula (g8) (wherein R ³ represents a monovalent organic group) And an imide group represented by the general formula (g9) and a phosphazene group represented by the general formula (g10) (wherein R ⁴ and R ⁵ represent a monovalent organic group). It is.

  Among polymers having such a polar group, the following general formula (P1)

(Here, Z ¹ and Z ² each represents an organic group containing an aromatic ring, and each may represent two or more groups. Y ¹ represents an electron-withdrawing group. Y ² represents O or S.) A and b each independently represents an integer of 0 to 2, provided that a and b are not 0 at the same time.)
An aromatic hydrocarbon polymer having a repeating unit represented by the following general formula (P3)

(Here, Z ⁵ and Z ⁶ each represents an organic group containing an aromatic ring, and each may represent two or more groups.)
It is preferably selected from polyimides having a repeating unit represented by:

Preferred organic groups as Z ⁵ are organic groups represented by the following general formula (Z5-1) to general formula (Z5-4), and most preferred in terms of hydrolyzability: An organic group represented by Z5-1). These may be substituted.

Preferred organic groups as Z ⁶ are organic groups represented by the following general formulas (Z6-1) to (Z6-10). These may be substituted.

  As the polymer electrolyte material, an aromatic hydrocarbon polymer having a repeating unit represented by the following general formula (P1) is more preferable from the viewpoint of excellent hydrolysis resistance. Among the aromatic hydrocarbon polymers having the repeating unit represented by the general formula (P1), the aromatic hydrocarbon polymer having the repeating unit represented by the general formula (P1-1) to the general formula (P1-9). Is particularly preferred. An aromatic hydrocarbon polymer having a repeating unit represented by formulas (P1-6) to (P1-9) is most preferable from the viewpoint of high proton conductivity and ease of production.

Preferred organic groups as Z ¹ are a phenylene group and a naphthylene group. These may be substituted.

Preferred organic groups as Z ² are a phenylene group, a naphthylene group, and organic groups represented by the following general formulas (Z2-1) to (Z2-14). These may be substituted. The organic group represented by the Among these general formulas (Z2-7) ~ Formula (Z2-14), particularly preferred for excellent fuel permeation suppressing effect, the polymer electrolyte of the present invention have the general formula as Z ² (Z2 It is preferable to contain at least one of organic groups represented by -7) to general formula (Z2-14). Of the organic groups represented by the general formulas (Z2-7) to (Z2-14), the organic groups represented by the general formulas (Z2-7) and (Z2-8) are most preferable.

Preferred examples of the organic group represented by R ¹ in the general formula (P1-4) and the general formula (P1-9) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, A vinyl group, an allyl group, a benzyl group, a phenyl group, a naphthyl group, a phenylphenyl group, and the like. From the viewpoint of industrial availability, the most preferable R ¹ is a phenyl group.

  Examples of a method for introducing an ionic group into these aromatic hydrocarbon polymers include a method of polymerizing using a monomer having an ionic group and a method of introducing an ionic group by a polymer reaction.

  As a method of polymerizing using a monomer having an ionic group, a monomer having an ionic group in a repeating unit may be used, and if necessary, an appropriate protecting group may be introduced to perform a deprotecting group after polymerization. . Such a method is described in, for example, Journal of Membrane Science, 197 (2002) 231-242.

  The method for introducing an ionic group in a polymer reaction will be described with an example. The introduction of a phosphonic acid group into an aromatic polymer is described in, for example, Polymer Preprints, Japan, 51, 750 (2002) Is possible. Introduction of a phosphate group into an aromatic polymer can be achieved by, for example, phosphoric esterification of an aromatic polymer having a hydroxyl group. Introduction of a carboxylic acid group into an aromatic polymer can be performed by oxidizing an aromatic polymer having an alkyl group or a hydroxyalkyl group, for example. Introduction of a sulfate group into an aromatic polymer can be achieved by, for example, sulfate esterification of an aromatic polymer having a hydroxyl group. As a method for sulfonating an aromatic polymer, that is, a method for introducing a sulfonic acid group, for example, a method described in JP-A-2-16126 or JP-A-2-208322 is known. Specifically, for example, an aromatic polymer can be sulfonated by reacting with a sulfonating agent such as chlorosulfonic acid in a solvent such as chloroform, or by reacting in concentrated sulfuric acid or fuming sulfuric acid. . The sulfonating agent is not particularly limited as long as it sulfonates an aromatic polymer, and sulfur trioxide or the like can be used in addition to the above. When the aromatic polymer is sulfonated by this method, the degree of sulfonation can be easily controlled by the amount of the sulfonating agent used, the reaction temperature and the reaction time. Introduction of a sulfonimide group into an aromatic polymer can be achieved, for example, by a method of reacting a sulfonic acid group and a sulfonamide group.

  Next, explanation will be given on the heterocyclic polymer.

The heterocyclic polymer in the present invention means a polymer containing a heterocyclic ring in a repeating unit, and the heterocyclic ring is a ring having one or more heteroatoms, that is, one of O, S, and N atoms. Means that. Such a heterocyclic ring may be in the main chain or in the side chain in the polymer, but from the viewpoint of mechanical strength, a heterocyclic polymer containing a heterocyclic ring in the main chain is more preferable.

Specific examples of the heterocyclic ring include, but are not limited to, the following general (h1) to (h12) as well as the total hydrogen adduct and partial hydrogen adduct thereof. . Two or more kinds of these heterocyclic rings can be contained in the polymer electrolyte material, and may be preferable by combining them.

  Since the heterocyclic polymer needs to be effective in suppressing fuel crossover, it is preferably insoluble in a 10 M aqueous methanol solution at 40 ° C. Therefore, a polymer containing a heterocyclic ring in the main chain is more preferable. preferable. Insoluble means that the polymer electrolyte membrane is immersed in a 10 M aqueous methanol solution at 40 ° C. for 8 hours and then filtered through a filter paper. The amount of the heterocyclic polymer detected from the filtrate is the amount of the complex polymer contained in the entire polymer electrolyte membrane. Meaning 5% by weight or less of the amount of the cyclic polymer. In addition, although methanol aqueous solution was assumed here as fuel, the behavior with respect to methanol aqueous solution is common also to other fuels, and has generality.

  Moreover, since this heterocyclic polymer is more preferable if it can provide solvent resistance, it is more preferable that it is insoluble with respect to N-methylpyrrolidone at 50 ° C. Insoluble means that the polymer electrolyte membrane is immersed in N-methylpyrrolidone at 50 ° C. for 5 hours and then filtered through filter paper, and the amount of the heterocyclic polymer detected from the filtrate is contained in the entire polymer electrolyte membrane. Meaning 5% by weight or less of the amount of the heterocyclic polymer. In this case, N-methylpyrrolidone is assumed as an example of the solvent for the polymer electrolyte material, but the behavior with respect to N-methylpyrrolidone is common to other solvents and has generality.

  Next, the heterocyclic polymer used in the present invention will be specifically described. The heterocyclic polymer used in the present invention is not particularly limited as long as it is substantially uniformly mixed with the hydrocarbon polymer having an ionic group to be used, and the resulting polymer electrolyte material has a haze of 30% or less. Is not to be done. A polymer having an effect of suppressing fuel crossover and excellent in mechanical strength and solvent resistance can be used more preferably without significantly degrading proton conductivity.

  Specific examples thereof include polyfuran, polythiophene, polypyrrole, polypyridine, polyoxazole, polybenzoxazole, polythiazole, polybenzthiazole, polyimidazole, polybenzimidazole, polypyrazole, polybenzpyrazole, polyoxadiazole, oxadiazole. Ring-containing polymers, polythiadiazoles, thiadiazole ring-containing polymers, polytriazoles, triazole ring-containing polymers, polyamic acids, polyimides, polyetherimides, polyimide sulfones and other hydrocarbon polymers, etc., but are not limited to these Absent. A plurality of types of polymers may be used in combination. Among them, in terms of solvent resistance and molding processability, polyoxazole, polybenzoxazole, polythiazole, polybenzthiazole, polyimidazole, polybenzimidazole, polypyrazole, polybenzpyrazole, polyoxadiazole, oxadiazole Ring-containing polymers, polythiadiazoles, thiadiazole ring-containing polymers, polytriazoles, triazole ring-containing polymers, and polyimides are preferred, and polyoxazoles, polybenzoxazoles, polyimidazoles, polybenzimidazoles, and polyimides are more preferable from the viewpoint of easy availability of industrial products. Preferably, polyimide is most preferably used in terms of compatibility and solvent resistance. In addition, the heterocyclic polymer is more preferably a solvent-insoluble polymer from the viewpoints of a fuel crossover suppressing effect, a swelling suppressing effect, and a solvent resistance. However, when a solvent-insoluble polymer is used, the precursor is considered in consideration of production costs. As the polymer, it is most preferable to use a polymer that can be formed into a solution and can be ring-closed and insolubilized by heat treatment or some kind of treatment such as a ring-closure accelerator.

  Among these, polyimide and its precursor polyamic acid are most preferably used from the viewpoint of compatibility with the hydrocarbon-based polymer having an ionic group, mechanical strength, solvent resistance and solvent solubility. The polyamic acid, which is a polyimide precursor, has a carboxylic acid group in addition to an amide group, and therefore has very good compatibility with a hydrocarbon polymer having an ionic group.

  Here, as an example of a preferable method for producing a polymer electrolyte material, a hydrocarbon polymer having an ionic group substituted with an alkali metal such as sodium and a polyamic acid which is a polyimide precursor are mixed in a solution state, It can be produced by casting on a support to obtain a self-supporting polyamic acid composite polymer electrolyte material, followed by heat imidization of the polyamic acid and proton substitution of the ionic group. The polymer electrolyte material produced by such a method not only can achieve both high proton conductivity and suppression of fuel crossover, but also enables solution film formation. The solvent resistance can be imparted due to the effect, so the catalyst paste can be directly applied to the polymer electrolyte membrane, and the production cost of the membrane electrode assembly can be greatly reduced, so it is most preferably used. can do.

  Next, the polyimide used for this invention and the polyamic acid which is its precursor are demonstrated concretely. The polyamic acid and imide used in the present invention are polymers that are substantially uniformly mixed with the hydrocarbon polymer having an ionic group and have a fuel crossover suppressing effect and can impart solvent resistance. If there is, it will not be specifically limited. As such a polyimide, a polymer that is soluble in the state of polyamic acid, is a polyimide after ring-closing imidization, and is insoluble in a solvent is more preferably used.

  The polyamic acid can be synthesized by a known method. For example, a method of reacting a tetracarboxylic dianhydride and a diamine compound at a low temperature, a method of obtaining a diester by tetracarboxylic dianhydride and an alcohol, and then reacting in the presence of an amine and a condensing agent; It can be synthesized by a method in which a diester is obtained with an anhydride and an alcohol, and then the remaining dicarboxylic acid is acid chlorideed and reacted with an amine.

  Specific examples of the acid dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic acid. Dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3,3′- Benzophenone tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1- Bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboki Phenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 1,2,5,6-naphthalene tetracarboxylic acid Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride Aromatic tetracarboxylic dianhydrides such as 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, butanetetracarboxylic dianhydride, 1,2,3,4-cyclo Examples thereof include aliphatic tetracarboxylic dianhydrides such as pentanetetracarboxylic dianhydride. These are used alone or in combination of two or more.

  Specific examples of diamines include 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, and 3,4'-diaminodiphenyl. Sulfone, 4,4′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfide, 1,4-bis (4-aminophenoxy) benzene, benzine, m-phenylenediamine , P-phenylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, bis (4-aminophenoxyphenyl) sulfone, bis (3-aminophenoxyphenyl) sulfone, bis (4-aminophenoxy) biphenyl, bis {4- (4-Aminophenoxy) fe Ether}, 1,4-bis (4-aminophenoxy) benzene, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-diethyl-4,4′-diaminobiphenyl, 3,3 '-Dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, 2,2', 3,3'-tetramethyl-4,4'-diaminobiphenyl, 3, 3 ′, 4,4′-tetramethyl-4,4′-diaminobiphenyl, 2,2′-di (trifluoromethyl) -4,4′-diaminobiphenyl, 9,9-bis (4-aminophenyl) Fluorene and its derivatives, or compounds in which these aromatic rings are substituted with alkyl groups or halogen atoms, aliphatic cyclohexyldiamine, methylenebiscyclohexylamine, etc. . These are used alone or in combination of two or more.

  Among these, an aromatic polyimide having a repeating unit represented by the following general formula (P2) is more preferably used from the viewpoint of the fuel crossover suppressing effect, solvent resistance, and mechanical strength.

(Here, Z ³ and Z ⁴ represent an organic group containing an aromatic ring, and each may represent two or more types of groups.)
Among these, more preferable polyamic acids include aromatic diamine components such as paraphenylenediamine, benzidine derivatives, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bisaminophenoxybenzenes, diaminobenzanilides, and the like. , Pyromellitic acid represented by pyromellitic dianhydride, 3,3′-4,4′-biphenyltetracarboxylic acid or its dianhydride, 3,3′-4,4′-benzophenonetetracarboxylic acid Alternatively, polyimide obtained by polymerizing an aromatic tetracarboxylic acid compound such as its dianhydride in a solvent and having excellent solvent resistance can be used more preferably.

  Solvents used in the polymerization include dimethyl sulfoxide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, N-methyl-2-pyrrolidone and dimethyl Examples thereof include sulfone, and these are preferably used alone or in combination.

  The polyamic acid obtained by the polymerization is prepared so as to have a ratio of 10 to 30% by weight in the solvent.

  In the polymer electrolyte material of the present invention, the hydrocarbon polymer having an ionic group and the heterocyclic polymer are preferably mixed uniformly for fuel crossover suppression and proton conductivity. The state in which the hydrocarbon polymer having an ionic group and the heterocyclic polymer are uniformly mixed is a state in which the two types of polymers are mixed without substantially taking a phase separation structure even in a water-containing state. is there. Confirmation that the two types of polymers are mixed substantially uniformly is possible by measuring the water content haze of the polymer electrolyte material. When the haze of the polymer electrolyte material in a water-containing state is measured and the haze exceeds 30%, for example, the domain size of the phase separation between the hydrophilic portion and the hydrophobic portion of the polymer electrolyte material is not less than the visible light wavelength size. Therefore, it is determined that the two types of polymers are not substantially uniformly mixed. When the haze is 30% or less, the movement of the molecular chain of the hydrocarbon polymer having the ionic group due to the interaction with the heterocyclic polymer in which the two types of polymers are substantially uniformly mixed at the molecular level. Is considered to be restricted, that is, the molecular chain of the hydrocarbon polymer having an ionic group is constrained. In a state where the hydrocarbon polymer having an ionic group and the heterocyclic polymer are substantially uniformly mixed, it is considered that the polymer chains are sufficiently entangled with each other, restraining each other's movement, It is considered that the fuel permeation is prevented or the solvent is dissolved.

  As a method for realizing a state in which a hydrocarbon polymer having an ionic group and a heterocyclic polymer are substantially uniformly mixed, both a hydrocarbon polymer having an ionic group and a heterocyclic polymer are polymer solutions. Or at least one of a hydrocarbon polymer having an ionic group and a heterocyclic polymer in the state of a precursor (monomer, oligomer, or precursor polymer), and then polymerization. Alternatively, there is a method of producing a polymer electrolyte material by performing a reaction. Among them, from the viewpoint of ease of molding processing and production cost, a step of mixing a hydrocarbon polymer having an ionic group and a heterocyclic polymer in a precursor state, and then ring-closing the precursor polymer after film formation The method of producing the polymer electrolyte material by going through is most preferable.

  In the present invention, if the compatibility is insufficient, a compatibilizing agent can be used as necessary. The compatibilizer used is not particularly limited as long as it compatibilizes the hydrocarbon polymer having an ionic group and the heterocyclic polymer to be used. For example, linear alkylbenzene sulfonate and Surfactant such as alkyl sulfate salt, hydroxyl group, ester group, amide group, imide group, ketone group, sulfone group, ether group, sulfonic acid group, sulfuric acid group, phosphonic acid group, phosphoric acid group, carboxylic acid group, etc. Examples include organic compounds and polymers having polar groups.

  When the polymer electrolyte material of the present invention is used for a fuel cell, it is usually used in a membrane state. However, the polymer electrolyte material of the present invention is not limited to a film shape, and the shape is not limited to the above-mentioned film shape, but is used for plate, fiber, hollow fiber, particle, lump, etc. Can take various forms. The method for converting the polymer electrolyte material of the present invention into a membrane is not particularly limited, but a method of forming a film from a solution state or a method of forming a film from a molten state is possible. In the former, for example, a method of forming a film by dissolving the polymer electrolyte material in a solvent such as N, N-dimethylacetamide, casting the solution on a glass plate or the like, and removing the solvent is exemplified. it can. The solvent used for film formation is not particularly limited as long as it dissolves the polymer and can be removed thereafter. N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), N- Aprotic polar solvents such as methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), sulfolane, 1,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphontriamide, or ethylene glycol monomethyl ether; An alkylene glycol monoalkyl ether such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, or propylene glycol monoethyl ether is preferably used. Examples of solvents that may be used in combination with these solvents include methanol, alcohols typified by ethanol, acetone, ketones typified by 2-butanone, ethyl acetate, esters typified by butyl acetate, diethyl ether, Examples include tetrahydrofuran, ethers typified by dioxane, triethylamine, amines typified by ethylenediamine, and the like. The film thickness can be controlled by the solution concentration or the coating thickness on the substrate. In the case of forming a film from a molten state, a melt press method or a melt extrusion method can be used.

  The thickness of the polymer electrolyte membrane is not particularly limited, but is preferably 1 to 500 μm. A thickness of more than 1 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 500 μm is preferable in order to reduce membrane resistance, that is, to improve power generation performance.

  In addition, the polymer electrolyte material of the present invention may contain additives such as plasticizers, stabilizers, mold release agents, etc. used in ordinary polymers within a range not contrary to the object of the present invention. I do not care.

  The membrane electrode assembly (MEA) of the present invention is constituted using the polymer electrolyte material of the present invention. Such a membrane electrode assembly is composed of a polymer electrolyte component constituted by using the polymer electrolyte material of the present invention. Examples of such a polymer electrolyte component include a polymer electrolyte membrane and / or an electrode catalyst layer.

  The electrode catalyst layer is a layer containing an electrode catalyst that promotes an electrode reaction, an electron conductor, an ion conductor, and the like. As the electrode catalyst contained in the electrode catalyst layer, for example, a noble metal catalyst such as platinum, palladium, ruthenium, rhodium, iridium and gold is preferably used. One of these may be used alone, or two or more of them, such as alloys and mixtures, may be used in combination.

  In general, various organic and inorganic materials are known as substances having ion conductivity (ion conductor) used in such an electrode catalyst layer. However, when used in a fuel cell, the ion conductivity is improved. A polymer having an ionic group such as a sulfonic acid group, a carboxylic acid group, or a phosphoric acid group (ion conductive polymer) is preferably used. Among these, the polymer electrolyte material of the present invention is particularly preferably used from the viewpoint of insolubility in fuel such as methanol. These ion conductive polymers are provided in the electrode catalyst layer in the state of a solution or a dispersion. At this time, the solvent for dissolving or dispersing the polymer is not particularly limited, but a polar solvent is preferable from the viewpoint of the solubility of the ion conductive polymer.

  There are no particular limitations on the method of joining the polymer electrolyte material and the electrode when such a polymer electrolyte material is used as a fuel cell, and known methods (for example, the chemical plating method described in Electrochemistry, 1985, 53, 269. Electrochem. Soc .: Electrochemical Science and Technology, 1988, 135 (9), 2209. can be applied. However, the film in the present invention is characterized by excellent solvent resistance. In such a case, a method of directly applying a catalyst paste to the polymer electrolyte film can be preferably used.

  The polymer electrolyte material of the present invention can be applied to various uses. For example, it can be applied to medical applications such as extracorporeal circulation columns and artificial skin, applications for filtration, ion exchange resin applications, various structural materials, and electrochemical applications. Among these, it can be preferably used for various electrochemical applications. Examples of the electrochemical application include a fuel cell, a redox flow battery, a water electrolysis device, a chloroalkali electrolysis device, and the like, among which the fuel cell is most preferable. Further, among fuel cells, it is suitable for a polymer electrolyte fuel cell, and there are those using hydrogen as a fuel and those using an organic compound such as methanol as a fuel. It is particularly preferably used for a direct fuel cell using at least one selected from a mixture of water and water as fuel. As the organic compound having 1 to 6 carbon atoms, alcohols having 1 to 3 carbon atoms such as methanol, ethanol and isopropyl alcohol, and dimethyl ether are preferable, and methanol is most preferably used.

  Furthermore, the application of the polymer electrolyte fuel cell of the present invention is not particularly limited, but a power supply source for a mobile body is preferable. In particular, mobile devices such as mobile phones, personal computers, PDAs, TVs, radios, music players, digital cameras, video cameras, game machines, headsets, DVD players, various human-type and animal-type robots for industrial use, vacuum cleaners, etc. It is preferably used as an electric power supply source for automobiles such as home appliances such as automobiles, passenger cars, buses, trucks, and mobiles such as ships and railways.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. In addition, the measurement conditions of each physical property are as follows.

(1) Sulfonic Acid Group Density A film-like sample serving as a specimen was immersed in pure water at 25 ° C. for 24 hours, vacuum-dried at 40 ° C. for 24 hours, and then measured by elemental analysis. Carbon, hydrogen, and nitrogen were analyzed by a fully automatic elemental analyzer varioEL, and sulfur was analyzed by a flask combustion method and barium acetate titration. The sulfonic acid group density per unit gram (mmol / g) was calculated from the composition ratio of the polymer.

(2) Proton conductivity After immersing the membrane-like sample in a 30 wt% methanol aqueous solution at 25 ° C for 24 hours, the membrane sample is taken out in an atmosphere of 25 ° C and relative humidity of 50-80%, and protons are obtained as quickly as possible by the constant potential AC impedance method. Conductivity was measured.

As a measuring apparatus, a Solartron electrochemical measurement system (Solartron 1287 Electrochemical Interface and Solartron 1255B Frequency Response Analyzer) was used. The sample was sandwiched between two circular electrodes (made of stainless steel) of φ2 mm and φ10 mm with a weight of 1 kg. The effective electrode area is 0.0314 cm ² . A 15% aqueous solution of poly (2-acrylamido-2-methylpropanesulfonic acid) was applied to the interface between the sample and the electrode. At 25 ° C., a constant potential impedance measurement with an AC amplitude of 50 mV was performed to determine proton conductivity in the film thickness direction.

(3) Methanol Permeation A film-like sample was immersed in a 30% by weight methanol aqueous solution for 24 hours and then measured at 20 ° C. using a 30% by weight methanol aqueous solution.

A sample membrane was sandwiched between the H-type cells, pure water (60 mL) was placed in one cell, and 30 wt% aqueous methanol solution (60 mL) was placed in the other cell. The cell capacity was 80 mL each. Moreover, the opening part area between cells was 1.77 cm < ² >. Both cells were stirred at 20 ° C. The amount of methanol eluted in pure water at the time of 1 hour, 2 hours and 3 hours was measured and quantified with a gas chromatography (GC-2010) manufactured by Shimadzu Corporation. The methanol permeation amount per unit time was determined from the slope of the graph.

(4) Haze measurement method of polymer electrolyte membrane As a sample, a polymer electrolyte membrane immersed in 1000 times weight pure water at 25 ° C. for 24 hours was used as a sample, and water droplets on the surface were wiped off. The haze value (Hz%) was measured using a fully automatic direct reading haze computer (manufactured by Suga Test Instruments Co., Ltd .: HGM-2DP).

(5) Weight reduction with respect to N-methylpyrrolidone A polymer electrolyte material (about 0.1 g) as a specimen was sufficiently washed with pure water, and then vacuum-dried at 40 ° C. for 24 hours to measure the weight. . The polymer electrolyte material was immersed in 1000 times weight of N-methylpyrrolidone and heated in a sealed container at 50 ° C. for 5 hours with stirring. Next, filtration was performed using filter paper (No. 2) manufactured by Advantech. During filtration, the filter paper and the residue were washed with the same solvent 1000 times weight, and the eluate was sufficiently eluted in the solvent. The residue was vacuum-dried at 40 ° C. for 24 hours and the weight was measured to calculate the weight loss.

(6) Weight average molecular weight The weight average molecular weight of the polymer was measured by GPC. Tosoh's HLC-8022GPC is used as an integrated device of an ultraviolet detector and a differential refractometer, and Tosoh's TSK gel SuperHM-H (inner diameter 6.0 mm, length 15 cm) is used as the GPC column. N-methyl-2 -Measured with a pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol / L of lithium bromide) at a flow rate of 0.2 mL / min, and the weight average molecular weight was determined in terms of standard polystyrene.

Comparative Example 1
A commercially available “Nafion” (R) 117 membrane (manufactured by DuPont) was used to evaluate ionic conductivity, MCO and haze, and weight loss relative to N-methylpyrrolidone. The “Nafion 11” 7 membrane was immersed in 5% hydrogen peroxide water at 100 ° C. for 30 minutes and then in 5% dilute sulfuric acid at 100 ° C. for 30 minutes, and then thoroughly washed with deionized water at 100 ° C. The evaluation results are summarized in Table 1.

Comparative Example 2
For the synthesis of sulfonated PPO (S-PPO), YPX-100L manufactured by Mitsubishi Gas Chemical Co., Ltd. was used as PPO, and the method described in J. Appl. Polym. Sci., 29, 4017 (1984). A blend polymer electrolyte material was prepared.

  The sulfonate group density of the sulfonated PPO was 3.0 mmol / g. S-PPO / PVDF = 8/2 containing S-PPO dissolved in N, N-dimethylacetamide (DMAc) and PVDF dissolved in N-methylpyrrolidone (NMP) (W # 1100 manufactured by Kureha Chemical Co., Ltd.) (Weight ratio) and stirred for 1 hour at room temperature. The mixed solution was cast on a glass substrate and dried at 100 ° C. for 3 hours to remove the solvent. The obtained film had a film thickness of 200 μm and was a soft film with white turbidity. The polymer electrolyte material had a sulfonic acid group density of 2.4 mmol / g. The evaluation results are summarized in Table 1. Although ionic conductivity was superior to “Nafion” 117, there was no methanol crossover suppression effect.

Synthesis example 1
Synthesis of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone represented by the following formula (G1)

109.1 g of 4,4′-difluorobenzophenone was reacted in 150 mL of fuming sulfuric acid (50% SO ₃ ) at 100 ° C. for 10 hours. Thereafter, the mixture was poured little by little into a large amount of water, neutralized with NaOH, and 200 g of sodium chloride was added to precipitate the composite. The obtained precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone represented by the above formula (G1).

Synthesis example 2
Synthesis of a polymer represented by the following formula (G2)

(In the formula, * represents that the right end of the upper formula and the left end of the lower formula are connected at that position.)
6.9 g of potassium carbonate, 14.1 g of 4,4 ′-(9H-fluorene-9-ylidene) bisphenol, and 4.4 g of 4,4′-difluorobenzophenone, and disodium 3,3 ′ obtained in Synthesis Example 1 above Polymerization was performed at 190 ° C. in N-methylpyrrolidone (NMP) using 8.4 g of disulfonate-4,4′-difluorobenzophenone. Purification was carried out by reprecipitation with a large amount of water to obtain a polymer represented by the above formula (G2). The resulting polymer had a sulfonic acid group density after proton substitution of 1.7 mmol / g and a weight average molecular weight of 220,000.

Comparative Example 3
The polymer (Na type) obtained in Synthesis Example 2 was made into a 25 wt% solution using N-methylpyrrolidone as a solvent, the solution was cast on a glass substrate and dried at 100 ° C. for 4 hours to remove the solvent. did. Furthermore, it heated up on 200-325 degreeC over 1 hour in nitrogen gas atmosphere, and heat-processed on the conditions heated at 325 degreeC for 10 minutes, Then, it stood to cool. After immersing in 1N hydrochloric acid for 1 day or longer to perform proton substitution, it was immersed in a large excess of pure water for 1 day or longer and washed thoroughly. The obtained film had a thickness of 70 μm and was a light yellow transparent flexible film.

  The evaluation results are summarized in Table 1. Compared with “Nafion” 117 of Comparative Example 1, the proton conductivity and the fuel blocking property were excellent. However, the solvent resistance was poor.

Example 1
The polymer of the formula (G2) obtained in Synthesis Example 2 dissolved in N-methylpyrrolidone (NMP), and a polyamic acid dissolved in N-methylpyrrolidone (NMP) (“Trenis” # 3000 manufactured by Toray Industries, Inc.) Were mixed with G2 / polyamic acid = 6/4 (weight ratio) and stirred at room temperature for 1 hour. The mixed solution is cast-coated on a glass substrate, pre-dried at 100 ° C. for 30 minutes, then heated to 200 to 325 ° C. over 1 hour in a nitrogen gas atmosphere, and heat treated under the conditions of heating at 325 ° C. for 10 minutes. And then allowed to cool. After immersing in 1N hydrochloric acid for 1 day or longer to perform proton substitution, it was immersed in a large excess of pure water for 1 day or longer and washed thoroughly.

  The obtained membrane had a thickness of 15 μm, and the sulfonic acid group density was 1.0 mmol / g. The evaluation results are summarized in Table 1. While maintaining high proton conductivity, the effect of suppressing methanol crossover was great. Moreover, it was excellent in solvent resistance.

Example 2
A film was prepared by the method described in Example 1 except that the weight ratio of G2 / polyamic acid was changed to G2 / polyamic acid = 4/6.

  The obtained membrane had a thickness of 10 μm and the sulfonic acid group density was 0.7 mmol / g. The evaluation results are summarized in Table 1. While maintaining high proton conductivity, the effect of suppressing methanol crossover was great. Moreover, it was excellent in solvent resistance.

Comparative Example 4
A film was prepared by the method described in Example 1 except that the weight ratio of G2 / polyamic acid was changed to G2 / polyamic acid = 0/10. The obtained film was 10 μm thick. The evaluation results are summarized in Table 1. There was no proton conductivity. Excellent solvent resistance.

Example 3 and Comparative Example 5
Using the polymer electrolyte membrane of Example 1, a polymer electrolyte fuel cell was prepared and evaluated by the following method. In addition, a commercially available “Nafion” 117 membrane of Comparative Example 1 was similarly evaluated by producing a polymer electrolyte fuel cell.

  The two carbon fiber cloth base materials were subjected to a water repellent treatment by immersion in 20% PTFE water, and then fired to prepare an electrode base material. On one electrode substrate, an anode electrode catalyst coating solution made of Pt-Ru-supported carbon and a commercially available “Nafion” solution (manufactured by DuPont) is applied and dried to form an anode electrode and another electrode substrate. A cathode electrode catalyst coating solution composed of Pt-supported carbon and Nafion solution was coated on the material and dried to prepare a cathode electrode.

  The polymer electrolyte membrane of Example 1 was held between the anode electrode and the cathode electrode prepared earlier and heated and pressed to prepare a membrane-electrode assembly (MEA). This MEA was set in a cell manufactured by Electrochem, and the MEA was evaluated by flowing a 30% aqueous methanol solution on the anode side and air on the cathode side. In the evaluation, a constant current was passed through the MEA, and the voltage at that time was measured. The measurement was performed until the current was increased successively until the voltage became 10 mV or less. The product of the current and voltage at each measurement point is the output.

The MEA using the polymer electrolyte membrane of Example 1 was 2.2 times the output (mW / cm ² ) and 3.1 times the energy capacity (Wh) than the MEA using the “Nafion” 117 membrane of Comparative Example 1. The value was doubled and had excellent characteristics.

  Table 1 shows the evaluation results of Examples 1-2 and Comparative Examples 1-4.

Synthesis example 3
Synthesis of a polymer represented by the following formula (G3)

(In the formula, * represents that the right end of the upper formula and the left end of the lower formula are connected at that position.)
It is represented by the above formula (G3) by the method described in Synthesis Example 1 except that 14.1 g of 9,9-bis (4-hydroxyphenyl) fluorene is changed to 14.1 g of 4,4′-dihydroxytetrafermethane. A polymer was obtained. The resulting polymer had a sulfonic acid group density after proton substitution of 1.7 mmol / g and a weight average molecular weight of 2
It was 0,000.

Synthesis example 4
Synthesis of polyamic acid represented by the following formula (G4)

  By reacting 17.42 g of 9,9-bis (4-aminophenyl) fluorene and 10.91 g of pyromellitic acid in 200 mL of N-methylpyrrolidone (NMP), NMP of the polyamic acid represented by the above formula (G4) A solution was obtained.

Synthesis example 5
Synthesis of polyamic acid represented by the following formula (G5)

  By reacting 10.81 g of paraphenylenediamine with 29.42 g of 3,3′-4,4′-biphenyltetracarboxylic dianhydride in 200 mL of N-methylpyrrolidone (NMP), the above formula (G5) is obtained. An NMP solution of polyamic acid was obtained.

Example 4
Production of a membrane by the method described in Example 1 except that the polymer represented by the formula (G3) was used instead of the polymer represented by the formula (G2) as the hydrocarbon polymer having an ionic group. Went.

  The obtained membrane had a thickness of 15 μm, and the sulfonic acid group density was 1.0 mmol / g. The evaluation results are summarized in Table 2. While maintaining high proton conductivity, the effect of suppressing methanol crossover was great. Moreover, it was excellent in solvent resistance.

Example 5
A film was prepared by the method described in Example 4 except that a polymer represented by the above formula (G4) was used as the polyamic acid instead of “Trenice” # 3000 manufactured by Toray Industries, Inc.

  The obtained membrane had a thickness of 15 μm, and the sulfonic acid group density was 1.0 mmol / g. The evaluation results are summarized in Table 2. While maintaining high proton conductivity, the effect of suppressing methanol crossover was great.

Example 6
A film was prepared by the method described in Example 4 except that the polymer represented by the formula (G5) was used in place of “Trenice” # 3000 manufactured by Toray Industries, Inc. as the polyamic acid.

  The obtained membrane was 15 μm thick, and the sulfonic acid group density was 1.0 mmol / g. The evaluation results are summarized in Table 2. While maintaining high proton conductivity, the effect of suppressing methanol crossover was great. Moreover, it was excellent in solvent resistance.

  Table 2 shows the evaluation results of Examples 4 to 6.

  The polymer electrolyte materials obtained in Examples 4 to 6 all had a great effect of suppressing methanol crossover while maintaining high proton conductivity. Moreover, the haze at the time of water | moisture content was 30% or less. The polymer electrolyte materials obtained in Examples 4 and 6 were excellent in solvent resistance.

The polymer electrolyte material obtained by the present invention can be applied to various electrochemical devices (for example, a fuel cell, a water electrolysis device, a chloroalkali electrolysis device, etc.). Among these devices, it is suitable for a fuel cell, and particularly suitable for a fuel cell using a methanol aqueous solution as a fuel.

The application of the polymer electrolyte fuel cell using the polymer electrolyte material obtained by the present invention is not particularly limited, but it is a mobile phone, personal computer, PDA, video camera, digital camera, television, radio, music player, game machine. , Portable devices such as headsets and DVD players, human-type and animal-type robots for industrial use, home appliances such as cordless vacuum cleaners, toys, electric bicycles, motorcycles, automobiles, buses, trucks and other vehicles and ships It is preferably used as a power supply source for a mobile body such as a railway, a conventional primary battery such as a stationary generator, an alternative to a secondary battery, or a hybrid power source with these.

Claims (16)

A polymer electrolyte material comprising a hydrocarbon-based polymer having at least an ionic group and a heterocyclic polymer, wherein the polymer electrolyte material has a water-containing haze of 30% or less. 2. The polymer electrolyte material according to claim 1, wherein the polymer electrolyte material has a weight loss of not more than 30% by weight after being immersed in N-methylpyrrolidone at 50 ° C. for 5 hours. 3. The polymer electrolyte material according to claim 1, comprising 20 to 80% by weight of the heterocyclic polymer based on the total amount of the hydrocarbon-based polymer having an ionic group and the heterocyclic polymer. Polymer electrolyte material. The hydrocarbon polymer having an ionic group has at least one ionic group selected from a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group. The polymer electrolyte material according to any one of claims 1 to 3. The polymer electrolyte material according to any one of claims 1 to 4, wherein the hydrocarbon-based polymer having an ionic group has at least a sulfonic acid group. 6. The polymer electrolyte material according to claim 5, wherein the hydrocarbon polymer having an ionic group has a sulfonic acid group density of 0.5 to 3.0 mmol / g. The polymer electrolyte material according to claim 1, wherein the hydrocarbon polymer having an ionic group is a non-crosslinked polymer. The hydrocarbon polymer having an ionic group is at least one selected from a sulfonyl group, an oxy group, a thio group, a carbonyl group, a phosphine oxide group, a phosphonic acid ester group, an ester group, an amide group, an imide group, and a phosphazene group. The polymer electrolyte material according to any one of claims 1 to 7, which comprises The hydrocarbon polymer having an ionic group comprises at least one selected from aromatic hydrocarbon polymers having a repeating unit represented by the following general formula (P1). A polymer electrolyte material according to any one of the above.

(Here, Z ¹ and Z ² each represents an organic group containing an aromatic ring, and each may represent two or more groups. Y ¹ represents an electron-withdrawing group. Y ² represents O or S.) A and b each independently represents an integer of 0 to 2, provided that a and b are not 0 at the same time.) The polymer electrolyte material according to claim 1, wherein the heterocyclic polymer is polyimide. The polymer electrolyte material according to claim 10, wherein the polyimide is a polymer having at least a repeating unit represented by the following general formula (P2).

(Here, Z ³ and Z ⁴ represent an organic group containing an aromatic ring, and each may represent two or more types of groups.) A polymer electrolyte membrane comprising the polymer electrolyte material according to claim 1. The polymer according to claim 12, after forming a mixture of a hydrocarbon polymer having an ionic group and a precursor of a heterocyclic polymer, and then ring-closing the precursor of the heterocyclic polymer. A method for producing a polymer electrolyte membrane, comprising producing an electrolyte membrane. A membrane electrode composite comprising the polymer electrolyte material or polymer electrolyte membrane according to any one of claims 1 to 13. A polymer electrolyte fuel cell comprising the polymer electrolyte material or polymer electrolyte membrane according to any one of claims 1 to 14. The polymer electrolyte fuel cell is a direct fuel cell using at least one selected from an organic compound having 1 to 6 carbon atoms and a mixture thereof with water as a fuel. The polymer electrolyte fuel cell as described.