JP4929569B2 - POLYMER ELECTROLYTE MATERIAL, POLYMER ELECTROLYTE MEMBRANE, MEMBRANE ELECTRODE COMPOSITE AND POLYMER ELECTROLYTE TYPE FUEL CELL USING SAME - Google Patents

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 has been attracting attention again in recent years due to the growing interest in protecting 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 ion 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.

  Until now, for example, Nafion (registered trademark of Nafion, 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, fuel such as methanol with high affinity for water is used. There was a problem that the electrolyte membrane easily permeates, 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. 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). However, in this document, these blend electrolyte materials are described as being translucent or white, and there is no description about methanol crossover, etc., but in such a blend electrolyte material having such a phase separation structure and a large haze. As far as we know, a sufficient methanol crossover suppression effect cannot be expected.

  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, it is conceivable to form the polymer electrolyte membrane, and then apply the catalyst paste onto the polymer electrolyte membrane and dry it. However, the polymer electrolyte material based on the hydrocarbon polymer described above is a catalyst paste. When the film is applied, the film dissolves or cracks or deformation occurs, and the power generation performance is not sufficiently exhibited. 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

  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 composite comprising the polymer electrolyte material, and a polymer electrolyte fuel cell.

In order to solve the above problems, the present invention employs the following means. That is, the polymer electrolyte material of the present invention is a polymer electrolyte material obtained from a hydrocarbon-based polymer having at least an ionic group and a crosslinkable compound having two or more groups represented by the following general formula (M1). The main chain structure of the hydrocarbon polymer having an ionic group is at least one selected from aromatic hydrocarbon polymers having an ionic group having a repeating unit represented by the following general formula (P1). The crosslinkable compound does not have a crosslinkable group other than the group represented by the following general formula (M1), and the water content haze of the polymer electrolyte material is 30% or less. Is. 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.

（ここで、Ｚ ^１ 、Ｚ ^２ は芳香環を含む有機基を表し、それぞれが２種類以上の基を表してもよい。Ｙ ^１ は電子吸引性基を表す。Ｙ ^２ はＯまたはＳを表す。ａおよびｂはそれぞれ独立に０〜２の整数を表し、ただしａとｂは同時に０ではない。） (Where R1 is hydrogen or any organic group.)

(Here, Z ¹ and Z ² each represent 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.)

  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. for it polyelectrolyte material, intensive study, the hydrocarbon polymer and the group of two or more with the crosslinking compound with the polymer electrolyte material obtained from represented by the following general formula (M1) having an ionic group, the The main chain structure of the hydrocarbon polymer having an ionic group is at least one selected from aromatic hydrocarbon polymers having an ionic group having a repeating unit represented by the following general formula (P1), crosslinkable compound has no crosslinkable group other than the group represented by the following general formula (M1), when the polymer electrolyte material is transparent to near-potato hydrous state, such problems It is obtained by investigation to resolve the behavior.

（ここで、Ｚ ^１ 、Ｚ ^２ は芳香環を含む有機基を表し、それぞれが２種類以上の基を表してもよい。Ｙ ^１ は電子吸引性基を表す。Ｙ ^２ はＯまたはＳを表す。ａおよびｂはそれぞれ独立に０〜２の整数を表し、ただしａとｂは同時に０ではない。）
すなわち、本発明の高分子電解質材は、少なくともイオン性基を有する炭化水素系ポリマーと前記一般式（Ｍ１）で示される基を２つ以上有する架橋性化合物からなり、該イオン性基を有する炭化水素系ポリマーの主鎖構造が下記一般式（Ｐ１）で示される繰返し単位を有するイオン性基を有する芳香族炭化水系ポリマーから選ばれた少なくとも１種からなるものであり、該架橋性化合物は下記一般式（Ｍ１）で示される基以外の架橋性基を有さず、その高分子電解質材の含水状態におけるヘーズが３０％以下であるという透明性を有することが特徴である。 (Where R1 is hydrogen or any organic group.)

(Here, Z ¹ and Z ² each represent 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.)
That is, the polymer electrolyte material of the present invention comprises at least a hydrocarbon polymer having an ionic group and a crosslinkable compound having two or more groups represented by the general formula (M1), and the carbon electrolyte having the ionic group. The main chain structure of the hydrogen-based polymer is at least one selected from aromatic hydrocarbon-based polymers having an ionic group having a repeating unit represented by the following general formula (P1). It is characterized in that it has no crosslinkable group other than the group represented by the general formula (M1) and has transparency such that the haze in the water-containing state of the polymer electrolyte material is 30% or less.

The present inventors include a hydrocarbon polymer having an ionic group and a crosslinkable compound having two or more groups represented by the general formula (M1), and a hydrocarbon polymer having the ionic group. The main chain structure is at least one selected from aromatic hydrocarbon polymers having an ionic group having a repeating unit represented by the general formula (P1), and the crosslinkable compound is represented by the general formula (M1). The polymer electrolyte material satisfying both of having no crosslinkable group other than the group represented by (2) and having a water-containing haze of 30% or less can achieve both high proton conductivity and fuel crossover suppression. The present inventors have found that it is effective, and that the membrane performance of the polymer electrolyte material depends on the uniformity and transparency of the polymer electrolyte material, that is, the haze in a water-containing state.

  The water-containing haze as used in the present invention is defined as a value measured as follows. As a sample, a polymer electrolyte membrane immersed in pure water having a water content, that is, 25 ° C. and 1000 times the weight of a dried polymer electrolyte membrane for 24 hours was used. After wiping off water droplets on the surface, fully automatic direct reading haze It is the value measured by the computer (Suga Test Instruments Co., Ltd. product: 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), n1 and n2 each independently represents a natural number. k1 and k2 each independently represents 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-based polymer having an ionic group and a crosslinkable compound having two or more groups represented by the general formula (M1), and by suppressing the haze in a water-containing state to 30% or less, It can achieve both high proton conductivity and low fuel crossover. 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 a fuel aqueous solution such as methanol does not swell at all in the fuel aqueous solution such as methanol, and has two or more groups represented by the general formula (M1). By being mixed with the crosslinkable compound at the molecular level, it is restrained at the molecular level, the swelling of the polymer electrolyte material to the aqueous fuel solution such as methanol is suppressed, the fuel crossover is reduced, and the strength of the membrane is also suppressed. Presumed to be.

  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. It becomes easy to form a cluster of water, 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.

In order that the polymer electrolyte material composed of the hydrocarbon polymer having an ionic group of the present invention and the crosslinkable compound having two or more groups represented by the general formula (M1) may be compatible with each other, You may mix a compatibilizing agent as needed. 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 water content haze 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 crosslinkable compound having two or more groups represented by the general formula (M1) are not uniformly mixed, Phase separation or the influence between these phases or the nature of the polymer having the original ionic group is reflected, and sufficient proton conductivity, fuel crossover suppression effect, and solvent resistance cannot be obtained. Moreover, the properties of the crosslinkable compound having two or more groups represented by the general formula (M1) 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 has excellent solvent resistance from the viewpoint of production cost and fuel crossover suppression effect, that is, a weight loss when immersed in N-methylpyrrolidone at 50 ° C. for 5 hours is 30%. % Or less is more preferable. More preferably, the weight source 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 composite. In addition to an increase in cost, 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 is immersed in 1000 times weight of N-methylpyrrolidone and heated in a sealed container at 50 ° C. for 5 hours with stirring. 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. The residue is vacuum-dried at 40 ° C. for 24 hours, and the weight loss is calculated by 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 the film with a film, and therefore it is preferable that the film is 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 dissolves in N-methylpyrrolidone, can reduce the interface resistance with the catalyst layer by direct coating, and can be manufactured at a low cost. This is considered to be an excellent polymer electrolyte material capable of greatly reducing

In the polymer electrolyte material of the present invention, the composition ratio of the hydrocarbon-based polymer having the ionic group and the crosslinkable compound having two or more groups represented by the general formula (M1) is a carbonization having an ionic group. 20 crosslinkable compounds having two or more groups represented by the general formula (M1) with respect to the total amount of the hydrogen-based polymer and the crosslinkable compound having two or more groups represented by the general formula (M1). More preferably, it is contained at 80% by weight. When the content of the crosslinkable compound having two or more groups represented by the general formula (M1) is less than 20% by weight, the fuel crossover suppressing effect and the solvent resistance may be insufficient. When it is included in excess, there is a tendency that sufficient proton conductivity cannot be obtained.

  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 cations forming the salt include arbitrary metal cations, ammonium cations, 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 from 0.1 to 5.0 mmol / g, more preferably from the viewpoint of proton conductivity, fuel crossover, and mechanical strength. From the standpoint of fuel crossover, it is most preferably 0.8 to 2.0 mmol / g. 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. When the sulfonic acid group density is higher than 5.0 mmol / g, it may be used as an electrolyte membrane for a fuel cell. 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 in a dry state, 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 in the effect of suppressing fuel crossover because it forms a cluster structure. It becomes very difficult to put a polymer electrolyte fuel cell that requires 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 crosslinked polymer means a polymer that has substantially no fluidity to heat or a polymer that is substantially insoluble in a solvent. If it does not dissolve in the solvent, it is insoluble. Further, the non-crosslinked polymer means that it is not a crosslinked polymer. The determination is defined to be determined 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 1000-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. 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. 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 that the elution weight is substantially insoluble in the solvent. This test was carried out for five solvents of toluene, hexane, N-methylpyrrolidone, methanol and water, and when it was determined that all the solvents were substantially insoluble, it was determined that the polymer was a crosslinked polymer, What was not determined as a crosslinked polymer by determination is determined as a non-crosslinked polymer.

Exemplified below an example of a hydrocarbon polymer having an ionic group (E-2).

  Next, (E-2) a polymer having an anionic group and having an aromatic ring in the main chain is a polymer having an aromatic ring in the main chain (hereinafter sometimes referred to as an aromatic hydrocarbon-based polymer). And having an ionic group.

  That is, the main chain structure is not particularly limited as long as it has an aromatic ring, but preferably has a sufficient mechanical strength such as that used as an engineering plastic. 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.

  Such a polar group is not particularly limited, but a functional group capable of coordinating 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 R1 represents a monovalent organic group), and a phosphonate ester group represented by formula (g6) (wherein , R2 represents a monovalent organic group.), An ester group represented by the general formula (g7), an amide group represented by the general formula (g8) (wherein R3 represents a monovalent organic group). ), An imide group represented by the general formula (g9) and a phosphazene group represented by the general formula (g10) (wherein R4 and R5 represent a monovalent organic group) and the like are preferable.

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

(Here, Z1 and Z2 each represent an organic group containing an aromatic ring, and each may represent two or more groups. Y1 represents an electron-withdrawing group. Y2 represents O or S. a and b. Each independently represents an integer of 0-2, provided that a and b are not 0 at the same time.)
An aromatic hydrocarbon polymer having a repeating unit represented by is selected.

The polymer electrolyte material is required to be an aromatic hydrocarbon polymer having an ionic group having a repeating unit represented by the general formula (P1) as a main chain structure in terms of excellent hydrolysis resistance. There is . Among the aromatic hydrocarbon polymer having an ionic group having a repeating unit represented as such a main chain structure in the general formula (P1), the general formula (P1-1) ~ formula as a main chain structure (P1-9) An aromatic hydrocarbon polymer having an ionic group having a repeating unit represented by is particularly preferable. Aromatic hydrocarbons having an ionic group having a repeating unit represented by general formula (P1-6) to general formula (P1-9) as the main chain structure in terms of high proton conductivity and ease of production Polymers are most preferred.

  Preferred organic groups as Z1 are a phenylene group and a naphthylene group. These may be substituted.

  Preferred organic groups as Z2 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. Among these, the organic groups represented by the general formulas (Z2-7) to (Z2-14) are particularly preferable because they are excellent in fuel permeation suppressing effect, and the polymer electrolyte of the present invention is represented by the general formula (Z2−2) as 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 general formula (Z2-7) to general formula (Z2-14), the organic group represented by general formula (Z2-8) is most preferable.

  Preferred examples of the organic group represented by R1 in the general formula (P1-4) and 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, and vinyl. Group, allyl group, benzyl group, phenyl group, naphthyl group, phenylphenyl group and the like. In view of industrial availability, R1 is most preferably 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 known method described in JP-A-2-16126 or JP-A-2-208322 may be used. it can. 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, description is added about the crosslinkable compound which has two or more groups shown by the following general formula (M1). In the present invention, two or more kinds of such crosslinkable compounds may be used at the same time.

(Where R1 is hydrogen or any organic group.)
A preferred embodiment of the polymer electrolyte material of the present invention is a polymer electrolyte membrane obtained by crosslinking the polymer electrolyte material of the present invention with a crosslinkable compound having two or more groups represented by the general formula (M1). By crosslinking with the crosslinkable compound, an effect of suppressing fuel crossover and swelling with respect to fuel can be expected, and mechanical strength is improved, which is more preferable.

When an aromatic hydrocarbon polymer is used for a polymer electrolyte material, since the polymer is generally excellent in radical resistance, it is difficult to sufficiently crosslink the inside by radiation crosslinking such as electron beam or γ-ray. However, when cross-linking is performed with a cross-linkable compound having two or more groups represented by the formula (M1) of the present invention, sufficient cross-linking proceeds, and it is relatively easy to suppress fuel crossover and solvent resistance. A polymer electrolyte material can be obtained.

  Among these, from the viewpoint of industrial availability and reaction efficiency, R1 is more preferably an alkyl group having 1 to 20 carbon atoms or an R2CO group (R2 represents an alkyl group having 1 to 20 carbon atoms). preferable.

Examples of the crosslinkable compound containing two or more groups represented by the formula (M1) used in the present invention include those having two organic groups (M1) as DM-BI25X-F, 46DMOC, 46DMOIPP, 46DMOEP (trade name, manufactured by Asahi Organic Materials Co., Ltd.), DML-MBPC, DML-MBOC, DML-OCHP, DML-PC, DML-PCHP, DML-PTBP, DML-34X, DML-EP, DML -POP, DML-OC, dimethylol-Bis-C, dimethylol-BisOC-P, DML-BisOC-Z, DML-BisOCHP-Z, DML-PFP, DML-PSBP, DML-MB25, DML-MTrisPC, DML-Bis25X -34XL, DML-Bis25X-PCHP (trade name, Honshu Chemical Industries Manufactured by), “Nicarak” (R) MX-290 (trade name, manufactured by Sanwa Chemical Co., Ltd.), 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p- There are three such as TriML-P, TriML-35XL, TriML-TrisCR-HAP (trade name, manufactured by Honshu Chemical Industry Co., Ltd.), etc. as having three such as cresol and 2,6-diacetoxymethyl-p-cresol TM-BIP-A (trade name, manufactured by Asahi Organic Materials Co., Ltd.), TML-BP, TML-HQ, TML-pp-BPF, TML-BPA, TMOM-BP (trade name, Honshu Chemical Industry ( Co., Ltd.), “Nicarac” MX-280, “Nicarac” MX-270 (trade name, manufactured by Sanwa Chemical Co., Ltd.), etc., and HML-TPPHBA, HM -TPHAP (trade name, manufactured by Honshu Chemical Industry Co., Ltd.) and the like. From the viewpoint of crosslinking in the present invention, a group represented by the formula (M1) are those which contain at least two.

  By adding these crosslinkable compounds, swelling of the resulting polymer electrolyte material with respect to the aqueous fuel solution is suppressed, high proton conductivity and fuel crossover suppression are compatible, and solvent resistance is greatly improved.

  These crosslinkable compounds are presumed that the polymer is crosslinked by a reaction mechanism that directly adds to the benzene ring as described below.

  Among these, from the viewpoint of industrial availability, fuel crossover suppression effect, and compatibility with a polymer having an ionic group, the structures of crosslinkable compounds particularly preferred for use in the present invention are shown below.

  The addition amount of such a crosslinkable compound is preferably 1 to 50 parts by weight, more preferably 3 to 40 parts by weight with respect to 100 parts by weight of the polymer. If the addition amount is less than 1 part by weight, the effect of crosslinking may be insufficient, and if it exceeds 50 parts by weight, proton conductivity or mechanical strength may be insufficient. The type and amount of the crosslinkable compound contained in the polymer electrolyte can be analyzed by various nuclear magnetic resonance spectra (NMR), infrared absorption spectra (IR), pyrolysis gas chromatographs and the like.

  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 crosslinkability having a group represented by the general formula (M1) The compound is mixed in a solution state, cast onto a support, and the crosslinkable compound is thermally cross-linked while evaporating the solvent to obtain a self-supporting composite polymer electrolyte material. Can be manufactured. 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, so the production cost is extremely low, and the crosslinkable compound Due to the crosslinking effect, it is possible to impart solvent resistance, 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. Most preferably, it can be used.

  In the polymer electrolyte material of the present invention, it is possible to suppress the fuel crossover and that the hydrocarbon polymer having an ionic group and the crosslinkable compound having the group represented by the general formula (M1) are uniformly mixed. Preferred for proton conductivity. The state in which the hydrocarbon-based polymer having an ionic group and the crosslinkable compound are uniformly mixed is obtained from the polymer and the crosslinkable compound without causing the crosslinkable compound to bleed out. The polymer electrolyte material is in a state of being mixed without substantially taking a phase separation structure even in a water-containing state. Confirmation that the polymer electrolyte material obtained from the polymer and the crosslinkable compound is substantially uniformly mixed can be confirmed by measuring the water-containing 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. It is determined that the polymer electrolyte material obtained from the polymer and the crosslinkable compound is not substantially uniformly mixed. On the other hand, when the haze is 30% or less, the polymer electrolyte material obtained from the polymer and the crosslinkable compound is substantially uniformly mixed at the molecular level, and is crosslinked by the crosslinkable compound. The movement of the molecular chain of the hydrocarbon polymer having an ionic group is limited, that is, the molecular chain of the hydrocarbon polymer having an ionic group is constrained. In a state where the hydrocarbon-based polymer having an ionic group and the crosslinkable compound are substantially uniformly mixed, the polymer chains are sufficiently cross-linked with each other, restraining each other's movement, It has the effect of hindering fuel permeation or hindering dissolution in a solvent.

  As a method for realizing a state in which the hydrocarbon polymer having an ionic group and the crosslinkable compound are substantially uniformly mixed, the hydrocarbon polymer having an ionic group from the viewpoint of compatibility, The most preferable method is to prepare a polymer electrolyte material by mixing the crosslinkable compound in a solution state, and then performing a step of crosslinking the crosslinkable compound after casting.

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

  Next, an example of a method for obtaining the polymer electrolyte membrane of the present invention by mixing the hydrocarbon-based polymer having the ionic group and the crosslinkable compound will be described.

  The same technique can be applied when the polymer electrolyte of the present invention is applied to the catalyst layer. These are examples, and there is no problem even if other methods are adopted.

  The first method is a method of forming a film after mixing a hydrocarbon polymer having an ionic group in a solution state or a molten state or a precursor thereof and the crosslinkable compound in a solution state or a molten state.

  The second method is a method in which a film made of a hydrocarbon polymer having an ionic group is brought into contact with and impregnated with the crosslinkable compound in a solution state or a molten state to form a film.

  In the former method, for example, a hydrocarbon polymer having an ionic group in a solution state and the crosslinkable compound in a solution state are mixed, the solution is cast on a glass plate or the like, and the crosslinkable compound is mixed. An example is a method of forming a film by removing the solvent while crosslinking.

  The solvent used for the 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. Solvents that may be used in combination with these solvents include methanol, ethanol 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.

  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 this C1-C6 organic compound, C1-C3 alcohols, such as methanol, ethanol, and isopropyl alcohol, and dimethyl ether are preferable, and methanol is used most preferably.

  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, it is preferably used as a power supply source for mobile devices such as mobile devices such as mobile phones, personal computers and PDAs, household appliances such as vacuum cleaners, automobiles such as passenger cars, buses and trucks, 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 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 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) Method for measuring haze of polymer electrolyte membrane As a sample, a polymer electrolyte membrane immersed in pure water with a weight of 1000 times that of a dry polymer electrolyte membrane in a water-containing state, that is, at 25 ° C., was used for the surface. After wiping off the water droplets, 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.

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 at 150 ° C. for 10 hours in 150 mL of fuming sulfuric acid (50% SO 3). 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.

Example 1
As a hydrocarbon polymer having an ionic group, 16 g of a 25 wt% N-methylpyrrolidone (NMP) solution obtained by dissolving the polymer of the formula (G2) obtained in Synthesis Example 2, and HMOM-TPPHBA (Honshu) as a crosslinkable compound 1 g of Chemical Industries, Ltd.) was mixed and stirred at room temperature for 1 hour. The mixed solution was cast-coated on a glass substrate, dried at 100 ° C. for 2 hours, and then heat-treated at 325 ° C. for 10 minutes under nitrogen to obtain a polymer electrolyte membrane. After immersing in 1N hydrochloric acid for 24 hours for proton substitution, it was immersed in a large excess amount of pure water for 24 hours and thoroughly washed.

  The obtained film was red and transparent, haze was 14%, weight loss with respect to NMP was 4%, and sulfonic acid group density was 1.4 mmol / g. The evaluation results of proton conductivity and methanol permeation amount are summarized in Table 1. The haze was small and the solvent resistance was excellent. Moreover, the effect of suppressing methanol crossover was large while maintaining high ionic conductivity.

Example 2
A film was prepared by the method described in Example 1 except that 1 g of the crosslinkable compound HMOM-TPPHBA (Honshu Chemical Co., Ltd.) was changed to 1 g of TML-BPA (Honshu Chemical Co., Ltd.).

  The obtained film was red and transparent, having a haze of 16%, a weight loss with respect to NMP of 5%, and a sulfonic acid group density of 1.4 mmol / g. The evaluation results of proton conductivity and methanol permeation amount are summarized in Table 1. The haze was small and the solvent resistance was excellent. Moreover, the effect of suppressing methanol crossover was large while maintaining high proton conductivity.

Comparative Example 1
A perfluoro-based commercially available Nafion (R) 117 membrane (manufactured by DuPont) was used as the polymer having an ionic group, and ionic conductivity, MCO and haze, and weight loss relative to N-methylpyrrolidone were evaluated. The Nafion 117 membrane was immersed in 5% hydrogen peroxide water at 100 ° C. for 30 minutes, then in 5% dilute sulfuric acid at 100 ° C. for 30 minutes, and then thoroughly washed with deionized water at 100 ° C. The haze of the Nafion (R) 117 membrane was 5%, and the weight loss with respect to NMP was 2%. The evaluation results of proton conductivity and methanol permeation amount are summarized in Table 1. The haze was small and the solvent resistance was excellent. Proton conductivity was relatively high, but methanol crossover was very large.

Comparative Example 2
For the synthesis of sulfonated PPO (S-PPO), which is a hydrocarbon polymer having an ionic group, YPX-100L manufactured by Mitsubishi Gas Chemical Co., Ltd. was used as PPO. J. Appl. Polym. Sci., 29, 4017 (1984) A sulfonated PPO / PVDF blend polymer electrolyte material was prepared by the method described.

  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. Without adding the crosslinkable compound, the mixed solution was cast-coated 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. This polymer electrolyte membrane had a haze of 92%, a weight loss with respect to NMP of 100%, and a sulfonic acid group density of 2.4 mmol / g. The evaluation results of proton conductivity and methanol permeation amount are summarized in Table 1. The haze was large and the solvent resistance was poor. Although proton conductivity was excellent, there was no methanol crossover suppression effect.

Comparative Example 3
The polymer (Na type) obtained in Synthesis Example 2, which is a hydrocarbon polymer having an ionic group, is made into a 25 wt% solution using N-methylpyrrolidone as a solvent, and the solution is made of glass without adding a crosslinking compound. The solvent was removed by casting on a substrate and drying at 100 ° C. for 4 hours. 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. This polymer electrolyte membrane had a haze of 14%, a weight loss with respect to NMP of 100%, and a sulfonic acid group density of 1.7 mmol / g. The evaluation results of proton conductivity and methanol permeation amount are summarized in Table 1. Although the haze was small, the solvent resistance was poor. Compared with “Nafion” 117 (R) of Comparative Example 1, the proton conductivity and the fuel blocking property were excellent, but Examples 1 and 2 were inferior in the fuel blocking property.

Example 3 and Comparative Example 4
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 (R) membrane of Comparative Example 1 was similarly produced and evaluated as 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 base material, an anode electrode catalyst coating solution made of Pt-Ru-supported carbon and a commercially available Nafion solution (R) (manufactured by DuPont) was applied and dried to obtain another anode electrode. A cathode electrode catalyst coating solution composed of Pt-supported carbon and a Nafion solution was applied onto a piece of electrode base material and dried to prepare a cathode electrode.

  The polymer electrolyte membrane of Example 1 was sandwiched 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 is 2.0 times the output (mW / cm ² ) and the energy capacity (Wh) than the MEA using the “Nafion” 117 (R) membrane of Comparative Example 1. It showed a value of 2.9 times and had excellent characteristics.

  Each evaluation result of Examples 1-2 and Comparative Examples 1-3 is shown in Table 1.

  As is clear from Table 1, the electrolyte membranes of Examples 1 and 2 of the present invention comprising at least a hydrocarbon polymer having an ionic group and a crosslinkable compound have a water-containing haze of 30% or less, While having proton conductivity, it was excellent in fuel cutoff. Furthermore, since it was crosslinked with a crosslinkable compound, it was excellent in solvent resistance.

Claims (14)

A polymer electrolyte material obtained from a hydrocarbon polymer having at least an ionic group and a crosslinkable compound having two or more groups represented by the following general formula (M1), the hydrocarbon system having the ionic group The main chain structure of the polymer is at least one selected from aromatic hydrocarbon polymers having an ionic group having a repeating unit represented by the following general formula (P1). A polymer electrolyte material having no crosslinkable group other than the group represented by the formula (M1) and having a water-containing haze of 30% or less.

(Where R1 is hydrogen or any organic group.)

(Here, Z ¹ and Z ² each represent 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.) 2. The polymer electrolyte material according to claim 1, wherein the polymer electrolyte material has a weight loss of 30% by weight or less when immersed in N-methylpyrrolidone at 50 ° C. for 5 hours. The polymer electrolyte according to claim 1 or 2, wherein the polymer electrolyte material contains 1 to 50 parts by weight of the crosslinkable compound with respect to 100 parts by weight of a hydrocarbon polymer having an ionic group. Wood. 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 polymer electrolyte material has a sulfonic acid group density of 0.5 to 3.0 mmol / g. The polymer electrolyte material according to any one of claims 1 to 6, wherein the hydrocarbon-based polymer having an ionic group is a non-crosslinked polymer. The hydrocarbon polymer having the ionic group is at least one selected from sulfonyl group, oxy group, thio group, carbonyl group, phosphine oxide group, phosphonic acid ester group, ester group, amide group, imide group and phosphazene group. The polymer electrolyte material according to any one of claims 1 to 7, wherein the polymer electrolyte material contains a seed group. R ^{1 in the} general formula (M1) is an alkyl group having 1 to 20 carbon atoms or an R ² CO group (R ² represents an alkyl group having 1 to 20 carbon atoms). Item 9. The polymer electrolyte material according to any one of Items 1 to 8 . A polymer electrolyte membrane comprising the polymer electrolyte material according to any one of claims 1 to 9 . By passing a coating liquid composed of a mixture of a hydrocarbon polymer having at least an ionic group and a crosslinkable compound having a group represented by the general formula (M1), followed by crosslinking, A method for producing a polymer electrolyte membrane, comprising producing the polymer electrolyte membrane according to claim 10 . A membrane electrode composite comprising the polymer electrolyte material or polymer electrolyte membrane according to any one of claims 1 to 10 . A polymer electrolyte fuel cell comprising the polymer electrolyte material or polymer electrolyte membrane according to any one of claims 1 to 10 . Polymer electrolyte fuel cell, an organic compound having 1 to 6 carbon atoms, and that in claim 13, wherein at least one selected from a mixture thereof with water is a direct-type fuel cell to the fuel The polymer electrolyte fuel cell as described.