JP5067083B2 - POLYMER ELECTROLYTE MATERIAL, POLYMER ELECTROLYTE MEMBRANE, MEMBRANE ELECTRODE COMPOSITION 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, high energy capacity, and long-term durability, and a polymer electrolyte membrane, a membrane electrode assembly and a polymer electrolyte fuel using the same It relates to batteries.

  BACKGROUND ART A fuel cell is a kind of power generation device that extracts electrical energy by electrochemically oxidizing a fuel such as hydrogen or methanol, and has recently attracted attention as a clean energy supply source. In particular, the polymer electrolyte fuel cell has a low standard operating temperature of around 100 ° C. and a high energy density, so that it is a relatively small-scale distributed power generation facility, a mobile power generator such as an automobile or a ship. As a wide range of applications are expected. 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. Since DMFC is liquid and does not use a reformer, it has the advantage that the energy density is high and the usage time of the portable device per filling is long.

  In a fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and a polymer electrolyte membrane serving as a proton conductor between the anode and the cathode are sometimes referred to as a membrane electrode assembly (hereinafter, abbreviated as MEA). ) And a cell in which this MEA is sandwiched between separators 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 the anode electrode of a polymer electrolyte fuel cell, a fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, which 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.

  As the required characteristics of the polymer electrolyte membrane, firstly, high proton conductivity can be mentioned. In addition, since the polymer electrolyte membrane functions as a barrier that prevents direct reaction between the fuel and oxygen, low permeability of the fuel is required. In particular, in a polymer electrolyte membrane for DMFC that uses an organic solvent such as methanol as fuel, methanol permeation is called methanol crossover (hereinafter sometimes abbreviated as MCO), which means that battery output and energy efficiency are reduced. Cause problems. Other required characteristics include chemical stability to withstand a strong oxidizing atmosphere during fuel cell operation and mechanical strength to withstand repeated thinning and swelling and drying.

  Conventionally, Nafion (registered trademark) (Nafion (registered trademark): manufactured by DuPont), which is a perfluorosulfonic acid polymer, has been widely used for polymer electrolyte membranes as a polymer electrolyte material. Nafion (registered trademark) is very expensive because it is manufactured through multi-step synthesis, and there is a problem that fuel crossover is large to form a cluster structure. In addition, due to the lack of hot water resistance and methanol resistance, there is a problem that the mechanical strength of the film made by swelling and drying is lowered, a problem that the softening point is low and the film cannot be used at a high temperature, and a disposal problem and materials after use. There was also a problem that it was difficult to recycle. 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.

  Here, being excellent in hot water resistance and heat resistant methanol property means that the dimensional change (swelling) in high temperature water and high temperature methanol is small. If this dimensional change is large, the membrane may be broken during use as a polymer electrolyte membrane, or it may swell and peel from the electrode catalyst layer, resulting in an increase in resistance. These hot water resistance and hot methanol properties are both important characteristics required for polymer electrolyte materials used in polymer electrolyte fuel cells.

  In order to overcome such drawbacks, some efforts have already been made to use a hydrocarbon-based polymer, which is a non-perfluoro-based polymer, as a polymer electrolyte material. As hydrocarbon polymers, aromatic polyether ketones and aromatic polyether sulfones have been particularly actively studied from the viewpoints of heat resistance and chemical stability.

  For example, a sulfonated product (for example, non-soluble aromatic polyetheretherketone (Victrex (registered trademark) PEEK (registered trademark) (manufactured by Victrex), etc.)), which is an aromatic polyetherketone, is used. Patent Document 1), a narrowly defined polysulfone that is an aromatic polyethersulfone (hereinafter sometimes abbreviated as PSF) (UDEL P-1700 (manufactured by Amoco) and the like) and a narrowly defined polyethersulfone. (Hereafter, it may be abbreviated as PES.) Sulfonated products (for example, Non-Patent Document 2) of SUMIKAEXCEL (registered trademark) PES (manufactured by Sumitomo Chemical Co., Ltd.) have been reported. There is a problem that the polymer swells under high humidity, especially in a fuel aqueous solution such as methanol or in a composition where the sulfonic acid density is high. Direction was remarkable.

  In addition, the method of introducing sulfonic acid groups onto the aromatic ring by sulfonation reaction (polymer reaction) of these polymers has a problem that the amount and position of the sulfonic acid groups introduced into the polymer cannot be precisely controlled. It was. As a method for improving this, a sulfonated aromatic polyether sulfone having a controlled amount of sulfonic acid group obtained by polymerization using a monomer having a sulfonic acid group introduced therein has been reported (for example, Non-Patent Document 1). reference). However, the problem that the polymer swells under high temperature and high humidity is not improved here either, especially in a fuel aqueous solution such as methanol or in a composition having a high sulfonic acid density. It has been difficult to sufficiently suppress combustion crossover and swelling of methanol or the like with an electrolyte membrane made of a polymer having poor properties.

  As one of the measures for suppressing the swelling, mixing with a basic polymer is performed. This is intended to suppress swelling by crosslinking acidic groups such as sulfonic acid groups in the polymer with a basic polymer. For example, a polyethersulfone having a sulfonic acid group or a mixture of a polyetheretherketone having a sulfonic acid group (acidic polymer) and polybenzimidazole (basic polymer) (see Patent Document 1) is known. However, it is usually difficult to mix different polymers at the molecular level, and it has not been possible to produce a membrane having excellent proton conductivity, fuel crossover, and mechanical properties. Patent Document 2 describes a polymer electrolyte material that is a blend polymer of a polybenzoxazole having an acidic group and a basic polymer having an acidic group, but the introduction amount of the basic group cannot be controlled, Protons were trapped in the basic group, and sufficient proton conductivity was not obtained. Furthermore, Patent Document 3 describes a polymer obtained by copolymerizing a monomer having an acidic group and a monomer having a basic group. However, the polymer is an aliphatic polymer, and a crosslinkable monomer must be added. Therefore, the mechanical strength and hot water resistance of membranes made of these polymers were not sufficient.

As described above, the polymer electrolyte material according to the prior art is insufficient as a means for improving economy, workability, proton conductivity, fuel crossover, mechanical strength, and long-term durability, and is an industrially useful fuel cell. It could not be a polymer electrolyte material for use.
"Polymer", 1987, vol. 28, 1009. “Journal of Membrane Science”, 83 (1993) 211-220. International Patent Publication No. W099 / 54389 JP 2003-022709 A JP 2006-024552 A

  In view of the background of such prior art, the present invention achieves both high proton conductivity and low fuel crossover, is excellent in mechanical strength, hot water resistance, and hot methanol resistance, and has a high polymer electrolyte fuel cell. It is an object of the present invention to provide a polymer electrolyte material that can achieve output, high energy density, and long-term durability, and a polymer electrolyte membrane, a membrane electrode assembly, and a polymer electrolyte fuel cell comprising the same.

（一般式（Ｑ１−ｓ）中、Ｘ^１は−ＣＯ−、−ＳＯ_２−、または−Ｐ（Ｒｐ）Ｏ−（Ｒｐは任意の有酸基）、Ｍ^１およびＭ^２は水素、金属カチオン、アンモニウムカチオン、ａ１およびａ２は１〜４の整数を表す。）

The present invention employs the following means in order to solve the above problems. That is, the polymer electrolyte material of the present invention contains at least a monomer structure having an acidic group, a monomer structure having a basic group in the main chain, and a neutral monomer structure as a copolymer structure, and has a monomer structure having an acidic group. The structure represented by the following general formula (Q1-s), wherein the basic group is a heterocyclic ring containing nitrogen selected from the following general formulas (N1) to (N8): It is a molecular electrolyte material. In addition, the polymer electrolyte membrane, the membrane electrode assembly and the polymer electrolyte fuel cell of the present invention are characterized by using such a polymer electrolyte material.

(In the general formula (Q1 -s), ^{X 1} is -CO -, - SO ₂ -, or -P (Rp) O- (Rp any Yusanmoto is), ^{M 1} and ^{M 2} is hydrogen, a metal cation , Ammonium cation, a1 and a2 represent an integer of 1 to 4.)

  According to the present invention, high output, high energy capacity and long-term durability are achieved with excellent proton conductivity, excellent fuel cutoff, mechanical strength, hot water resistance, heat resistance methanol resistance, processability, and chemical stability. It is possible to provide a polymer electrolyte material excellent in practicality that can be used, and a high-performance polymer electrolyte membrane, a membrane electrode assembly and a solid polymer fuel cell using the same.

  Hereinafter, the present invention will be described in detail.

The present invention is excellent in proton conductivity, fuel cutoff, mechanical strength, hot water resistance, hot methanol resistance, processability, and chemical stability, and is used for a polymer electrolyte fuel cell. As a polymer electrolyte material that can achieve high output, high energy density and long-term durability, the monomer structure having at least an acidic group, the monomer structure having a basic group in the main chain, and a medium The monomer structure containing a basic monomer structure as a copolymer structure and having an acidic group is a structure represented by the general formula (Q1-s), and the basic group is represented by the general formulas (N1) to (N8). when using an ionic group-containing polymer electrolyte material characterized heterocyclic der Rukoto containing nitrogen chosen is obtained by investigation to solve such problems at a stroke.

  The polymer electrolyte material of the present invention does not simply introduce a basic group together with an acidic group as a polymer, but a monomer structure having an acidic group as a copolymer structure, a monomer structure having a basic group in the main chain, and a neutral monomer By introducing the structure, the introduction position, introduction amount and introduction ratio of the acid base and the acid / base interaction between the acidic group and the basic group are strictly controlled at the molecular level, and high proton conductivity is maintained while maintaining high proton conductivity. Suppression of swelling of molecular electrolyte material was realized. As a result, it was excellent in dimensional stability and mechanical strength in high-temperature and high-humidity fuel solutions such as methanol, and achieved both high proton conductivity and suppression of fuel crossover. In addition, since the solvent resistance is excellent due to ionic crosslinking, it is possible to use high-concentration methanol as a fuel. Furthermore, it is possible to achieve excellent chemical stability and tough physical properties by introducing a basic group into the main chain.

  The ionic group-containing polymer used in the polymer electrolyte material and the polymer electrolyte membrane of the present invention is more preferably a hydrocarbon polymer. The ionic group-containing hydrocarbon polymer referred to 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 (registered trademark) (manufactured by DuPont), Flemion (registered trademark) (manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark) (manufactured by Asahi Kasei Co., Ltd.). ) And other commercial products. 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. Due to the bulky side chain, no crystallization peak is observed in the differential scanning calorimetry, which is not preferable. Moreover, since the packing of the polymer molecular chain is poor, the tear strength and tensile strength at break are small, which is not preferable.

  The polymer electrolyte material of the present invention is more preferably a polymer having an aromatic ring in the main chain among hydrocarbon polymers from the viewpoint of hot water resistance and mechanical strength. That is, it is a polymer having an aromatic ring in the main chain and having an acidic group. The main chain structure is not particularly limited as long as it has an aromatic ring, but preferably has a sufficient mechanical strength to be used, for example, as an engineering plastic.

  Specific examples of the polymer having an aromatic ring in the main chain used in the polymer electrolyte material of the present invention include polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether-based polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, Composition of polyarylene polymer, polyarylene ketone, polyether ketone, polyarylene phosphine oxide, polyether phosphine oxoxide, polybenzoxazole, polybenzthiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, polyimidesulfone, etc. Examples include polymers containing at least one of the components. Polysulfone, polyethersulfone, polyetherketone, and the like referred to here are generic names for polymers having a sulfone bond, an ether bond, and a ketone bond in the molecular chain thereof. Polyetherketoneketone, polyetheretherketone, It includes polyether ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone and the like, and does not limit the specific polymer structure.

  Among the polymers having an aromatic ring in the main chain, polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyarylene ketone, polyether ketone, polyarylene phosphine hydroxide, poly A polymer such as ether phosphine oxide is more preferable from the viewpoint of mechanical strength, processability and hydrolysis resistance. Specifically, a polymer containing an aromatic group in the main chain having a repeating unit represented by the following general formula (T1) can be given.

(Here, Z ¹ and Z ² each represents an organic group containing an aromatic ring, and each of them may represent two or more groups. At least a part of at least one of Z ¹ and Z ² is an acidic group. Y ¹ represents an electron-withdrawing group, Y ² represents O or S. a and b each independently represent 0 or a positive integer, provided that a and b are not 0 at the same time.)
Among the polymers containing aromatic groups in the main chain having the repeating unit represented by the general formula (T1), the polymers having the repeating units represented by the general formula (T1-1) to the general formula (T1-6) are resistant to It is more preferable in terms of hydrolyzability, mechanical strength and production cost. Among them, from the viewpoint of mechanical strength and production cost, an aromatic polyether polymer in which Y ² is O is more preferable, and most preferably has a repeating unit represented by the general formula (T1-3), that is, Aromatic polyether ketone polymers are most preferred.

(Here, Z ¹ and Z ² each represents an organic group containing an aromatic ring, and each of them may represent two or more groups. At least a part of at least one of Z ¹ and Z ² is an acidic group. A and b each independently represent 0 or a positive integer, provided that a and b are not 0 at the same time.)
Preferred organic groups as Z ¹ are a phenylene group and a naphthylene group. These may be substituted.

Preferred examples of the organic group represented by R ^p in the general formula (T1-4) 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, and 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 ^p is a phenyl group.

  In the present invention, the aromatic polyether-based polymer refers to a polymer mainly composed of an aromatic ring and containing an ether bond as a mode in which the aromatic ring units are connected. In addition to the ether bond, there may be a bond mode generally used for forming an aromatic polymer such as a direct bond, ketone, sulfone, sulfide, various alkylenes, imides, amides, esters, and urethanes. The ether bond is preferably at least one per repeating unit of the main constituent component. The aromatic ring may include not only a hydrocarbon aromatic ring but also a hetero ring. Further, a part of the aliphatic units may constitute a polymer together with the aromatic ring unit. Aromatic units include hydrocarbon groups such as alkyl groups, alkoxy groups, aromatic groups, allyloxy groups, halogen groups, nitro groups, cyano groups, amino groups, halogenated alkyl groups, carboxyl groups, phosphonic acid groups, hydroxyl groups, etc. And may have an arbitrary substituent.

  The acidic 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 acidic groups include the case 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 them, Na and K that are inexpensive and can easily be proton-substituted without being adversely affected by solubility are more preferably used as the polymer electrolyte material.

Two or more kinds of these acidic 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 these, 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 it is necessary to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance.

  The method for synthesizing the aromatic polyether polymer of the present invention is not particularly limited as long as it is a method capable of substantially increasing the molecular weight. For example, an aromatic active dihalide compound and a dihydric phenol are used. It can be synthesized using an aromatic nucleophilic substitution reaction of a compound or an aromatic nucleophilic substitution reaction of a halogenated aromatic phenol compound.

  As a monomer for obtaining a monomer structure having an acidic group used in the present invention, an acidic group may be introduced into either a dihydric phenol compound or an aromatic active dihalide compound, but in consideration of chemical durability. Thus, it is preferable to synthesize by using a compound having an acidic group introduced into an aromatic active dihalide compound as a monomer.

Therefore, the polymer electrolyte material of the present invention as a monomer structure having an acidic group, a monomer structure represented by the following general formula (Q1-s).

(In the general formula (Q1 -s), ^{X 1} is -CO -, - SO ₂ -, or -P (Rp) O- (Rp any Yusanmoto is), ^{M 1} and ^{M 2} is hydrogen, a metal cation , Ammonium cation, a1 and a2 represent an integer of 1 to 4.)
Of the general formula (Q1-s), the following general formula (Q2-s) is preferable from the viewpoint of mechanical strength and dimensional stability.

(In the general formula (Q2- s ) , M ³ and M ⁴ represent hydrogen, a metal cation, or an ammonium cation.)
The aromatic active dihalide compound to be used is not particularly limited as long as the molecular weight can be increased by an aromatic nucleophilic substitution reaction with a divalent phenol compound. It is preferable to use a compound in which an acidic group is introduced into an aromatic active dihalide compound as a monomer because the amount of the acidic group can be precisely controlled. In view of proton conductivity and hydrolysis resistance, the acidic group is most preferably a sulfonic acid group, and an aromatic dihalide compound represented by the following general formula (Q1) is more preferable. These sulfonic acid groups are preferably salted with a monovalent cationic species during polymerization. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. These aromatic active dihalide compounds can be used alone, but a plurality of aromatic active dihalide compounds can also be used in combination.

(In general formula (Q1), Z ¹ is halogen, X ¹ is —CO—, —SO ₂ —, or —P (Rp) O— (Rp is any acid group), M ¹ and M ² are hydrogen , Metal cation, ammonium cation, a1 and a2 each represent an integer of 1 to 4.)
In the present invention, preferred specific examples of the electron withdrawing group X ¹ of the aromatic dihalide compound represented by the general formula (Q1), ketone, sulfone, phosphine oxide, and the like. Preferred examples of the phosphine oxide substituent include methyl, ethyl, propyl, isopropyl, cyclopentyl, cyclohexyl, norbornyl, vinyl, allyl, benzyl, phenyl, naphthyl, and phenylphenyl. Group. A phenyl group is most preferable as a substituent in terms of industrial availability.

Among these, from the viewpoint of mechanical strength and dimensional stability, an aromatic dihalide compound represented by the following general formula (Q2) in which X ¹ is a ketone is more preferable.

(In General Formula (Q2), Z ² represents halogen, M ³ and M ⁴ represent hydrogen, a metal cation, and an ammonium cation.)
Specific examples of the aromatic dihalide compound represented by the general formula (Q1) include 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfonate-4,4′-difluoro. Diphenyl sulfone, 3,3′-disulfonate-4,4′-dichlorodiphenyl ketone, 3,3′-disulfonate-4,4′-difluorodiphenyl ketone, 3,3′-disulfonate-4,4′- Examples thereof include dichlorodiphenylphenylphosphine oxide and 3,3′-disulfonate-4,4′-difluorodiphenylphenylphosphine oxide. Among these, as the aromatic active dihalide compound represented by the general formula (Q1), 3,3′-disulfonate-4,4′-dichlorodiphenyl ketone is preferable in terms of production cost, heat-resistant methanol resistance, and fuel crossover suppression effect. 3,3′-disulfonate-4,4′-difluorodiphenyl ketone is more preferable, and 3,3′-disulfonate-4,4′-difluorodiphenyl ketone is most preferable from the viewpoint of polymerization activity.

  In the polymer electrolyte material of the present invention, the content mole fraction W1 of the monomer structure having an acidic group is 2 mol% or more and 40 mol% or less with respect to the total molar amount of the structural units, proton conductivity and dimensional stability, From the balance, it is more preferably 7 mol% or more and 35 mol% or less.

  When the content mole fraction W1 of the aromatic dihalide compound having a sulfonic acid group represented by the general formula (Q1) is less than 2 mol%, proton conductivity may be insufficient. Since stability may be insufficient, each is not preferable.

  In the polymer electrolyte material of the present invention, the molar fraction W1 of the structural unit represented by the general formula (Q1) can be measured by neutralization titration or elemental analysis of sulfonic acid groups. However, when the acidic group density is larger than the basic density, (acidic group density−basic density) is calculated from the neutralization titration measurement.

  The amount of sulfonic acid group in the polymer electrolyte material can be expressed 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 0.5 to 3.0 mmol / g in terms of proton conductivity, fuel crossover and mechanical strength, and most preferably in terms of fuel crossover. Is 0.7-1.5 mmol / g. When the sulfonic acid group density is lower than 0.5 mmol / g, sufficient proton generation characteristics may not be obtained due to low proton conductivity. When the sulfonic acid group density is higher than 3.0 mmol / g, it may be used as an electrolyte membrane for a fuel cell. In addition, sufficient hot 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 dried 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, it is preferable to calculate from the S / C ratio using an elemental analysis method for ease of measurement. However, when a sulfur source other than a sulfonic acid group is included, the ion exchange capacity is obtained by a neutralization titration method. You can also

The procedure for neutralization titration is as follows. The measurement shall be performed three times or more and the average shall be taken.
(1) The sample is pulverized by a mill, and in order to make the particle diameter uniform, the sample is passed through a 50-mesh mesh sieve and the sample passed through the sieve is used as the measurement sample.
(2) Weigh the sample tube (with lid) with a precision balance.
(3) About 0.1 g of the sample of (1) is put into a sample tube and vacuum dried at 40 ° C. for 16 hours.
(4) Weigh the sample tube with the sample and determine the dry weight of the sample.
(5) Dissolve sodium chloride in a 30 wt% aqueous methanol solution to prepare a saturated saline solution.
(6) Add 25 mL of the saturated salt solution of (5) above to the sample and stir for 24 hours for ion exchange.
(7) Titrate the resulting hydrochloric acid with 0.02 mol / L aqueous sodium hydroxide. Two drops of a commercially available titration phenolphthalein solution (0.1% by volume) as an indicator are added, and the point at which light reddish purple is obtained is the end point.
(8) The ion exchange capacity is obtained by the following formula.

Ion exchange capacity (meq / g) =
[Concentration of sodium hydroxide aqueous solution (mmol / ml) × Drip amount (ml)] / Dry weight of sample (g)
The polymer having an ionic group of the present invention contains other components, for example, an inactive polymer or an organic or inorganic compound having no conductivity or ionic conductivity, as long as the object of the present invention is not impaired. It does not matter.

  The method for introducing an ionic group will be described with an example. The introduction of a phosphonic acid group into an aromatic compound can be performed by the method described in Polymer Preprints, Japan, 51, 750 (2002), for example. Introduction of a phosphate group into an aromatic compound is possible by, for example, phosphoric esterification of an aromatic compound having a hydroxyl group. Introduction of a carboxylic acid group into an aromatic compound is possible, for example, by oxidizing an aromatic compound having an alkyl group or a hydroxyalkyl group. Introduction of a sulfate group into an aromatic compound can be performed by, for example, sulfate esterification of an aromatic compound having a hydroxyl group. As a method for sulfonating an aromatic compound, 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, the aromatic compound 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 compound, and in addition to the above, sulfur trioxide and the like can be used. When the aromatic compound 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 compound can be achieved, for example, by a method of reacting a sulfonic acid group and a sulfonamide group.

  Next, a monomer for obtaining a monomer structure having a basic group in the main chain will be described.

The polymer electrolyte material of the present invention is not a side chain from the viewpoint of suppressing swelling by strongly crosslinking a basic group with an acidic group and obtaining an electrolyte membrane excellent in mechanical strength and long-term durability. The main chain must contain a basic group. In the present invention, the main chain in the monomer is a site that forms a skeleton when it becomes a polymer. In the present invention, a nitrogen-containing heterocyclic ring is effective as a radical trapping agent, and the chemistry of the electrolyte membrane. It is preferable to introduce from the viewpoint of mechanical durability. Further, doping a nitrogen-containing heterocyclic ring with a strong acid such as phosphoric acid or sulfuric acid is preferable because proton conductivity can be improved without humidification or low humidification.
The basicity of the main chain means that the polymer skeleton is broken when the basicity is removed.

As a basic group used in the present invention, heterocycles can be mentioned including the nitrogen selected from the following formulas (N1) ~ (N8), these heterocycles aromatic active dihalide compound, a divalent phenol It may be contained on either side of the compound. From the viewpoint of production cost, among these, a heterocyclic ring containing nitrogen selected from the general formulas (N1), (N6) and (N8) is more preferable, and the heterocyclic ring represented by the general formula (N1) due to its basic strength. Is most preferred.

  As the monomer structure having a basic group in the main chain, a monomer structure represented by the following general formula (N1-1) is preferable.

  Among these compounds containing a basic group, a compound structure represented by the following general formula (Q3-s) is preferable from the viewpoint of ease of synthesis and high stability.

  As the basic group-containing monomer, a basic group-containing bisphenol represented by the following general formula (N1-2) or a basic group-containing aromatic dihalide compound represented by the following general formula (N1-3) is most preferable. .

  In the polymer electrolyte material of the present invention, the content mole fraction W2 of the monomer structure having a basic group in the main chain is 0.5 mol% or more and 15 mol% or less with respect to the total mol amount of the structural units. Is more preferably 3 mol% or more and 10 mol% or less from the viewpoint of dimensional stability due to the construction of a crosslinked structure. If it is less than 0.5 mol%, no crosslinking effect is observed, and if it exceeds 15 mol%, proton conductivity may be lowered.

  The molar fraction ratio W2 / W1 of the monomer structure having an acidic group and the monomer structure having a basic group in the main chain is more preferably 0.02 to 0.4, still more preferably 0.1. ~ 0.3. If it is less than 0.02, the crosslinking effect may not be observed, and if it exceeds 0.4, the acidic group may be weakened and proton conductivity may be insufficient.

  Next, the monomer for obtaining the neutral monomer structure used in the present invention will be described.

  In the polymer electrolyte material of the present invention, it is necessary to copolymerize a neutral monomer from the viewpoint of strictly controlling the introduction position, introduction amount and introduction ratio of the acid base at the molecular level. In the present invention, the neutral monomer does not mean that the monomer itself is neutral, but means that it contains neither an acidic group nor a basic group when copolymerized into a polymer. For example, even a bisphenol compound is defined as a neutral monomer if it has no acidic group or basic group in addition to two phenol groups. In the aromatic polyether polymer of the present invention, the neutral monomer may be contained on the aromatic dihalide compound side, the bisphenol side, or both. It is possible to select conveniently according to the monomer having an acidic group or the monomer having a basic group.

  As the neutral monomer structure, a compound structure selected from the following general formulas (Ar1-1) to (Ar1-13) is preferable. Of these, (Ar1-4) is more preferable.

  Preferable specific examples of the aromatic active dihalide compound used as a neutral monomer in the present invention include 4,4′-dichlorodiphenylsulfone, 4,4′-difluorodiphenylsulfone, 4,4′-dichlorodiphenylketone, 4 , 4'-difluorodiphenyl ketone, 4,4'-dichlorodiphenylphenylphosphine oxide, 4,4'-difluorodiphenylphenylphosphine oxide, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, etc. Can do. Among these, 4,4′-dichlorodiphenyl ketone and 4,4′-difluorodiphenyl ketone are more preferable from the viewpoint of mechanical strength, heat-resistant methanol resistance, and fuel crossover suppression effect, and 4,4′-difluorodiphenyl ketone from the viewpoint of polymerization activity. Is most preferred. These aromatic active dihalide compounds can be used alone, but a plurality of aromatic active dihalide compounds can also be used in combination.

  In the polymer electrolyte material of the present invention, it is also preferable to copolymerize a bisphenol compound as a neutral monomer. At this time, the structure of the bisphenol compound can be conveniently selected in consideration of hot water resistance, hot methanol resistance, mechanical strength, and the like.

  Specific examples of suitable bisphenol compounds used as neutral monomers in the present invention include compounds represented by the following general formulas (ArB1-1) to (ArB1-13). These may have a substituent. Among these, the compounds represented by the general formulas (ArB1-1) to (ArB1-9) are particularly preferable because they have a large fuel permeation suppressing effect and are effective in improving dimensional stability in fuel. As the electrolyte material, it is preferable to use at least one of the compounds represented by the general formulas (ArB1-1) to (ArB1-9) as a monomer. Of the compounds of the general formulas (ArB1-1) to (ArB1-9), the compounds of the general formulas (ArB1-1) to (ArB1-6) are particularly preferable, and the compound of the (ArB1-4) is most preferable. .

  The aromatic polyetherketone polymer composed of the compound of the general formula (ArB1-4) exhibits crystallinity because of its good packing and extremely strong intermolecular cohesive force, and has the property of not dissolving in a general solvent at all. On the other hand, by adding a protecting group in the polymer, solubility has been improved by reducing the crystallinity of crystalline polymers such as polyetherketone-based polymers that have been difficult to form in the past. And can be used for film formation. Examples of the protective group used in the polymer electrolyte material of the present invention include those commonly used in organic synthesis, and the protective group is temporarily introduced on the assumption that it is removed at a later stage. It is a substituent to be protected, which protects a highly reactive functional group and renders it inactive to the subsequent reaction, and can be deprotected and returned to the original functional group after the reaction. That is, it is a pair with a functional group to be protected. For example, a t-butyl group may be used as a protective group for a hydroxyl group, but when the same t-butyl group is introduced into an alkylene chain, It is not called a protecting group. The reaction for introducing a protecting group is called protection (reaction), and the reaction for removal is called deprotection (reaction).

  Such protective reactions include, for example, Theodora W. Greene, “Protective Groups in Organic Synthesis”, US, John Wiley & Sons, Inc), 1981, which can be preferably used. It can be appropriately selected in consideration of the reactivity and yield of the protection reaction and deprotection reaction, the stability of the protecting group-containing state, the production cost, and the like. In addition, the stage for introducing a protecting group in the polymerization reaction may be selected from the monomer stage, the oligomer stage, or the polymer stage, and can be appropriately selected.

  Specific examples of the protection reaction include protecting / deprotecting a ketone moiety with an acetal or ketal moiety, and protecting / deprotecting a ketone moiety with a heteroatom analog of the acetal or ketal moiety, such as thioacetal or thioketal. The method of doing is mentioned. These methods are described in Chapter 4 of “Protective Groups in Organic Synthesis”. Further, a method for protecting / deprotecting between a sulfonic acid and a soluble ester derivative, a method for protecting / deprotecting by introducing a t-butyl group as a soluble group into an aromatic ring and det-butylating with an acid, etc. . However, it is not limited to these and can be preferably used. In terms of improving solubility in a general solvent and reducing crystallinity, an aliphatic group, particularly an aliphatic group containing a cyclic moiety, is preferably used as a protective group in terms of large steric hindrance.

  The position of the functional group for introducing the protective group is more preferably the main chain of the polymer. Since the polymer electrolyte material of the present invention introduces a protecting group into a polymer having good packing for the purpose of improving processability, the effect of the present invention can be sufficiently obtained even if a protecting group is introduced into the side chain portion of the polymer. There may not be. Here, the functional group present in the main chain of the polymer is defined as a functional group that breaks the polymer chain when the functional group is deleted. For example, this means that if the ketone group of the aromatic polyether ketone is deleted, the benzene ring and the benzene ring are broken.

  In the present invention, the polymer being crystalline means that the polymer has a crystallizable property that can be crystallized under some conditions. The term “amorphous polymer” means that the polymer is amorphous when used, regardless of whether the polymer is crystalline or not. The presence or absence of crystallinity of these polymers and the crystalline and amorphous states can be evaluated by sharp peaks derived from crystals in wide-angle X-ray diffraction (XRD), crystallization peaks in differential scanning calorimetry (DSC), and the like. .

  The protective reaction used in the polymer electrolyte material of the present invention is more preferably a method of protecting / deprotecting a ketone moiety with an acetal or ketal moiety, and a ketone moiety with an acetal or ketal moiety in terms of reactivity and stability. This is a method of protecting / deprotecting with a heteroatom analog of thioacetal or thioketal. Accordingly, the bisphenol compound used as a neutral monomer in the present invention is preferably a compound represented by the following general formula (P1-1) or (P2-1).

(In the general formulas (P1-1) and (P2-1), Ar _{1 to} Ar ₄ are any divalent arylene group, R ₁ and R ₂ are at least one group selected from H and an alkyl group, R ₃ represents an arbitrary alkylene group, and E represents O or S. The compounds represented by the general formula (P1-1) and the general formula (P2-1) may be optionally substituted.
Specific examples of particularly preferred bisphenol compounds used in the present invention include compounds represented by the following general formulas (r1) to (r10), and derivatives derived from these bisphenol compounds.

  Among these bisphenol compounds, compounds represented by the general formulas (r4) to (r10) are more preferable from the viewpoint of stability, and more preferably represented by the general formulas (r4), (r5), and (r9). A compound, most preferably a compound represented by the general formula (r4).

  In the present invention, as a method for producing a ketal bisphenol compound of the above general formula with a short reaction time and high conversion rate, for example, 4,4′-dihydroxybenzophenone as a ketone precursor is represented by the following general formula (2 )

[Wherein R ¹ , R ² , R ³ and R ⁴ each represent an independent substituent, and R ¹ , R ² , R ³ and R ⁴ are a hydrogen atom or a linear or branched group having 1 to 4 carbon atoms. -Like hydrocarbon group. And a glycol (2) represented by formula (II) in the presence of an alkyl orthoester and an organic sulfonic acid.

  Specific examples of the linear or branched hydrocarbon group having 1 to 4 carbon atoms in the glycols (2) used include methyl, ethyl, n-propyl, isopropyl, n-butyl, and t-butyl. Group and the like. Specific glycols (2) include ethylene glycol, 1,2-propanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 2-methyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 1,2-hexanediol, 2,3-hexanediol, 3,4-hexanediol, etc. It is done. The amount of glycols (2) to be used is usually 1 to 30 mol times, preferably 5 to 15 mol times with respect to 4,4'-dihydroxybenzophenone.

  Examples of the alkyl orthoester used include trimethyl orthoformate, triethyl orthoformate, trimethyl orthoacetate, triethyl orthoacetate and the like. The amount of alkyl orthoester used is usually 1 to 10 moles, preferably 2 to 5 moles per 4,4'-dihydroxybenzophenone.

  Examples of the organic sulfonic acids used in this reaction include p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and the like. Preferably, p-toluenesulfonic acid and benzenesulfonic acid are used. Moreover, the acid to be used may contain crystal water. The amount of the organic sulfonic acids used is usually 0.1 mol% to 50 mol%, preferably 0.5 mol% to 5 mol%, based on 4,4'-dihydroxybenzophenone.

  This reaction is performed in a solvent if necessary. Examples of the solvent include hydrocarbons such as toluene and xylene, and each is used alone or in combination of two or more.

  For mixing 4,4′-dihydroxybenzophenone and glycols (2), for example, in an inert gas atmosphere such as nitrogen gas, in a solvent, or in the absence of a solvent, 4,4′-dihydroxybenzophenone and glycol are mixed. Class (2), alkyl orthoesters, and organic sulfonic acids may be added in any order.

  The reaction temperature is usually in the range of 20 to 150 ° C. Preferably, the reaction is carried out at a temperature from 25 ° C. to the boiling point of the orthoformate used, more preferably at a temperature at which the alcohol produced as a by-product from the orthoformate is distilled off. The reaction time is usually from 0.1 hour to 10 hours, and the reaction is completed in 0.5 to 8 hours. After the reaction, the reaction mixture may be mixed with an organic solvent, neutralized, and then washed with water.

  Reaction of 4,4′-dihydroxybenzophenone and glycols (2) produces a ketal bisphenol compound. To remove the ketal bisphenol compound, for example, after adding an alkaline aqueous solution of pH 9 to 13 and an organic solvent, An aqueous layer containing unreacted glycols can be separated to obtain an organic layer containing a ketal bisphenol compound. Examples of the organic solvent used in this case include toluene, benzene, ethylbenzene, amylbenzene, isopropylbenzene, xylene, heptane, hexane, chlorobenzene, dichlorobenzene, dichloroethane, trichloroethane, chloroform, chlorotoluene, dichlorotoluene, methyl chloride, and methylene chloride. , Amyl alcohol, octanol, t-butanol, benzyl alcohol, methyl tertiary butyl ether, diisobutyl ketone, diisopropyl ketone, methyl ethyl ketone, methyl isopropyl ketone, methyl benzoate, ethyl acetate, propyl acetate, isobutyl acetate, amyl acetate, benzyl acetate, propion Examples include methyl acid. The organic solvent can be used alone or in combination of two or more. Of these, ethyl acetate, isobutyl acetate, and methyl isobutyl ketone are preferred.

  The amount of the organic solvent used when extracting the reaction solution containing the ketal bisphenol compound may be any amount as long as it is an amount that can dissolve the ketal bisphenols, but is usually 1 to 30 times the amount of the ketal bisphenol compound. The amount is preferably in the range of 3 to 10 times. If the amount is less than 1 time, the extraction efficiency is lowered because the ketal bisphenol compound is not completely dissolved. If it is 30 times or more, the volumetric efficiency is lowered and the economic efficiency is deteriorated.

  Examples of the alkaline aqueous solution having a pH of 9 to 13 include alkali metal carbonates such as sodium carbonate and potassium carbonate, and aqueous solutions of ammonia. This aqueous alkaline solution can efficiently remove not only glycols but also 4,4'-dihydroxybenzophenone as an impurity into the aqueous layer. However, in the case of an alkaline aqueous solution having a pH of less than 9, removal of the impurity 4,4'-dihydroxybenzophenone is insufficient. In the case of an alkaline aqueous solution having a pH of 13 or more, not only the glycols and impurities 4,4'-dihydroxybenzophenone but also the ketal bisphenol compound are extracted into the aqueous layer, resulting in a decrease in yield.

  As a purification method, a high-purity ketal bisphenol compound in which the amount of 4,4′-dihydroxybenzophenone is 1% by weight or less can be obtained by concentrating and crystallizing an organic solvent containing the obtained ketal bisphenol compound. . For example, the concentrated solution is cooled as it is to crystallize the ketal bisphenol compound, followed by solid-liquid separation, or the concentrated solution is added with a poor solvent, cooled and crystallized, and then solid-liquid separated.

The chemical structure of the polymer electrolyte material of the present invention has an S = O absorption of 1,030 to 1,045 cm ⁻¹ , 1,160 to 1,190 cm ⁻¹ , 1,130 to ¹ , C-O-C absorption at 250 cm ^-1, can be confirmed by such C = O absorption of 1,640～1,660Cm ^-1, these composition ratio, neutralization titration or sulfonic acid groups, knowing by elemental analysis Can do. Moreover, the structure can be confirmed from the peak of an aromatic proton of 6.8 to 8.0 ppm, for example, by nuclear magnetic resonance spectrum ( ¹ H-NMR). Further, the position and arrangement of sulfonic acid groups can be confirmed by solution ¹³ C-NMR and solid ¹³ C-NMR.

  Furthermore, the polymer electrolyte material of the present invention can be used for TEM phase analysis by dyeing sulfonic acid groups and basic groups, S and N distribution analysis by EPMA, polymer extraction using various solvents, etc. By using in combination, it is possible to distinguish the copolymer structure or the blend structure. In the polymerization by the aromatic nucleophilic substitution reaction in the present invention, a polymer can be obtained by reacting the monomer mixture in the presence of a basic compound. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more.

  Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and those that can convert an aromatic diol into an active phenoxide structure may be used. It can use without being limited to. In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system.

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

  The molecular weight of the polymer used as the polymer electrolyte material of the present invention thus obtained is 10000 to 5 million, preferably 10,000 to 500,000 in terms of polystyrene-converted weight average molecular weight. If it is less than 10,000, the mechanical strength may be insufficient, such as cracking in the molded film. On the other hand, if it exceeds 5 million, there may be problems such as insufficient solubility, high solution viscosity, and poor processability.

  The sulfonic acid group in the polymer used as the polymer electrolyte material of the present invention may be introduced by block copolymerization or random copolymerization. It can be appropriately selected depending on the chemical structure of the polymer used and the high crystallinity. Random copolymerization is more preferable when fuel barrier properties and low water content are required, and block copolymerization is more preferably used when proton conductivity and high water content are required.

  When the polymer electrolyte material of the present invention is used for a fuel cell, it is usually used in a membrane state and a binder for a catalyst layer.

  The method for forming the polymer electrolyte material of the present invention into a polymer electrolyte 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, the polymer electrolyte material is dissolved in a solvent such as N-methyl-2-pyrrolidone, the solution is cast on a glass plate or the like, and the solvent is removed to form a film. It can be illustrated.

  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 membrane shape, and the shape is not limited to the above-mentioned membrane shape, but can be used such as a plate shape, a fiber shape, a hollow fiber shape, a particle shape, and a lump shape. 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 the polymer electrolyte material can be dissolved and then removed. For example, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone , Aprotic polar solvents such as dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphontriamide, ester solvents such as γ-butyrolactone and butyl acetate, carbonates such as ethylene carbonate and propylene carbonate Solvent, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, alkylene glycol monoalkyl ether such as propylene glycol monoethyl ether, or isopropanol Alcohol solvents, water and mixtures thereof is preferably used, is preferred for high highest solubility aprotic polar solvent.

  It is a preferable method to obtain a tough membrane by subjecting the polymer solution prepared to a required solid content concentration to normal pressure filtration or pressure filtration to remove foreign substances present in the polymer electrolyte solution. The filter medium used here is not particularly limited, but a glass filter or a metallic filter is suitable. In the filtration, the pore size of the minimum filter through which the polymer solution passes is preferably 1 μm or less. If filtration is not carried out, foreign matter is allowed to enter, and film breakage occurs or durability becomes insufficient.

  Next, the obtained polymer electrolyte membrane is preferably heat-treated after at least a part of the acidic groups is in a metal salt state. The metal of the metal salt may be any metal that can form a salt with sulfonic acid, but from the viewpoint of cost and environmental load, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, and the like are preferable. Among these, Li, Na, K, Ca, Sr, and Ba are more preferable, and Li, Na, and K are more preferable. The temperature of this heat treatment is preferably 150 to 550 ° C, more preferably 160 to 400 ° C, and particularly preferably 180 to 350 ° C. The heat treatment time is preferably 10 seconds to 12 hours, more preferably 30 seconds to 6 hours, and particularly preferably around 1 hour. If the heat treatment temperature is too low, the effect of suppressing fuel permeability is insufficient. On the other hand, if it is too high, the film material tends to deteriorate. If the heat treatment time is less than 10 seconds, the effect of suppressing fuel permeability is insufficient. On the other hand, when it exceeds 12 hours, the film material tends to deteriorate. The polymer electrolyte membrane obtained by the heat treatment can be proton-substituted by being immersed in an acidic aqueous solution as necessary. By molding by this method, the polymer electrolyte membrane of the present invention can achieve both a good balance between proton conductivity and fuel cutoff.

  The polymer electrolyte membrane obtained by the heat treatment can be proton-substituted by being immersed in an acidic aqueous solution as necessary. By molding by this method, the polymer electrolyte membrane of the present invention can achieve both a good balance between proton conductivity and fuel cutoff. Among them, it is more preferable that at least a part of the acidic group is in the form of a metal salt until polymerization or film formation, and the acid type is substituted by the above method after film formation. By this method, it is possible to prevent the acid-base interaction from acting at the time of processing, to impart processability, and to provide pseudo-crosslinking between polymer chains by the acid-base interaction after processing. Moreover, the method of deprotecting a part or all of the ketone moiety protected with acetal and / or ketal to form a ketone moiety is not particularly limited, but includes a method of acid treatment after molding. Specifically, it is possible to deprotect the molded membrane by immersing it in an aqueous hydrochloric acid or sulfuric acid solution. The acid concentration and aqueous solution temperature take into account the ease of soaking into the molded product. It can be selected appropriately. For example, if the film has a thickness of 50 μm, it can be easily deprotected by dipping in an acidic aqueous solution as exemplified by a 6N hydrochloric acid aqueous solution and heating at 95 ° C. for 8 hours. However, the deprotection conditions are not limited to these, and the deprotection may be performed with an acid gas or an organic acid.

  The film thickness of the polymer electrolyte membrane of the present invention is preferably 1 to 2000 μm. A thickness of more than 1 μm is more preferable for obtaining the strength of a film that can withstand practical use, and a thickness of less than 2000 μm is preferable for reducing the film resistance, that is, improving the power generation performance. A more preferable range of the film thickness is 3 to 500 μm, and a particularly preferable range is 5 to 250 μm. The film thickness can be controlled by the solution concentration or the coating thickness on the substrate.

  In addition, an additive such as a plasticizer, a stabilizer, or a mold release agent used for a general polymer compound may be added to the polymer electrolyte material of the present invention within a range not contrary to the object of the present invention. it can.

  In addition, the polymer electrolyte material of the present invention includes various polymers, elastomers, fillers, and the like for the purpose of improving mechanical strength, thermal stability, workability, and the like within a range that does not adversely affect the above-described properties. Fine particles, various additives, and the like may be included.

The polymer electrolyte membrane of the present invention preferably has a methanol permeation amount per unit area of 40 μmol · min ⁻¹ · cm ⁻² or less with respect to a 30 wt% aqueous methanol solution under the condition of 20 ° C. In the fuel cell using the polymer electrolyte membrane, from the viewpoint of obtaining high output and high energy capacity in a region where the fuel concentration is high, it is desired that the fuel permeation amount is small in order to maintain a high fuel concentration. is there. The amount of methanol permeated is measured after the polymer electrolyte membrane is immersed in pure water at 25 ° C. for 24 hours.

From this viewpoint, 0 μmol · min ⁻¹ · cm ⁻² is most preferable, but from the viewpoint of ensuring proton conductivity, 0.01 μmol · min ⁻¹ · cm ⁻² or more is preferable.

In addition, the polymer electrolyte membrane of the present invention preferably has a proton conductivity per unit area of 1 S · cm ⁻² or more, and more preferably ² S · cm ⁻² or more. Proton conductivity can be measured by the constant potential alternating current impedance method, which is performed as quickly as possible after immersing the polymer electrolyte membrane in pure water at 25 ° C. for 24 hours, taking it out in an atmosphere of 25 ° C. and 50% to 80% relative humidity. it can.

By setting the proton conductivity per unit area to 1 S · cm ⁻² or more, when used as a polymer electrolyte membrane for a fuel cell, sufficient proton conductivity, that is, sufficient battery output can be obtained. Higher proton conductivity is preferable, but a membrane with high proton conductivity is likely to be dissolved or disintegrated by a fuel such as methanol water, and the fuel permeation amount tends to increase, so a practical upper limit is 50 S · cm. ^-2 .

  The polymer electrolyte membrane of the present invention preferably achieves the low methanol permeation amount and the high proton conductivity as described above from the viewpoint of achieving both high output and high energy capacity.

  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.

  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.

  Fuels for fuel cells using the membrane electrode assembly of the present invention include oxygen, hydrogen and methane, ethane, propane, butane, methanol, isopropyl alcohol, acetone, glycerin, ethylene glycol, formic acid, acetic acid, dimethyl ether, hydroquinone, cyclohexane Examples thereof include organic compounds having 1 to 6 carbon atoms and mixtures of these with water, and may be one kind or a mixture of two or more kinds. In particular, a fuel containing hydrogen and an organic compound having 1 to 6 carbon atoms is preferably used from the viewpoint of power generation efficiency and simplification of the entire battery system, and hydrogen and aqueous methanol are particularly preferable in terms of power generation efficiency.

  In the case of using an aqueous methanol solution, the concentration of methanol is appropriately selected depending on the fuel cell system to be used. A concentration as high as possible is preferable from the viewpoint of long-time driving. For example, an active fuel cell having a system for sending a medium necessary for power generation, such as a liquid feed pump or a blower fan, to a membrane electrode assembly, or an auxiliary machine such as a cooling fan, a fuel dilution system, or a product recovery system has a methanol concentration of 30 It is preferable to inject ~ 100% or more of fuel with a fuel tank or fuel cassette, dilute it to about 0.5 to 20% and send it to the membrane electrode assembly. A passive fuel cell without auxiliary equipment has a methanol concentration Is preferable in the range of 10 to 100%.

  Furthermore, the application of the polymer electrolyte fuel cell using the polymer electrolyte material of the present invention is not particularly limited, but a power supply source for a moving body is preferable. In particular, mobile devices such as mobile phones, personal computers, PDAs, televisions, radios, music players, game machines, headsets, DVD players, human-type and animal-type robots for industrial use, home appliances such as cordless vacuum cleaners, and toys , Electric bicycles, motorcycles, automobiles, buses, trucks and other vehicles and ships, power supplies for mobiles such as railways, stationary primary generators such as stationary generators, or alternatives to these It is preferably used as a hybrid power source.

  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. Further, a chemical structural formula is inserted in this example, and the chemical structural formula is inserted for the purpose of helping the reader to understand. The chemical structure of the polymerization component of the polymer, the exact composition, the arrangement, the sulfonic acid The position, number, molecular weight, and the like of the group are not necessarily expressed accurately, and are not limited thereto.

(1) Density of sulfonic acid group The polymer electrolyte membrane 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, sulfur was analyzed by a flask combustion method / barium acetate titration, and fluorine was analyzed by a flask combustion / ion chromatograph method. The sulfonic acid group density per unit gram (mmol / g) was calculated from the composition ratio of the polymer.

(2) Proton conductivity After immersing a membrane sample in pure water at 25 ° C. for 24 hours, the membrane sample is taken out in an atmosphere at 25 ° C. and a relative humidity of 50 to 80%, and the proton conductivity is measured by the constant potential AC impedance method as quickly as possible. did.

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) Weight average molecular weight The weight average molecular weight of the polymer electrolyte material 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 lithium bromide) at a sample concentration of 0.1 wt%, a flow rate of 0.2 mL / min, and a temperature of 40 ° C. The weight average molecular weight was determined.

(4) Film thickness It measured using Mitutoyo ID-C112 type | mold set to Mitutoyo granite comparator stand BSG-20.

(5) Hot water resistance The hot water resistance of the electrolyte membrane was evaluated by measuring the dimensional change rate in hot water at 95 ° C. The electrolyte membrane was cut into a strip having a length of about 5 cm and a width of about 1 cm, immersed in water at 25 ° C. for 24 hours, and the length (L1) was measured with a caliper. The electrolyte membrane was immersed in hot water at 95 ° C. for 8 hours, and then the length (L2) was measured again with a caliper, and the size change was visually observed.

(6) Heat-resistant methanol property The heat-resistant methanol property of the polymer electrolyte membrane was evaluated by measuring the dimensional change rate in a 30 wt% methanol aqueous solution at 60 ° C. The polymer electrolyte membrane was cut into a strip having a length of about 5 cm and a width of about 1 cm, immersed in water at 25 ° C. for 24 hours, and then the length (L1) was accurately measured with a caliper. The polymer electrolyte membrane was immersed in a 30 wt% methanol aqueous solution at 60 ° C. for 12 hours, and then the length (L2) was accurately measured again with a caliper, and the dimensional change rate was calculated by the following formula (S1).

(Dimensional change rate in 30 wt% methanol aqueous solution) = L2 / L1 (S1)
L1: length of polymer electrolyte membrane (cm) after being immersed in water at 25 ° C. for 24 hours
L2: Length of the polymer electrolyte membrane (cm) after being immersed in a 30 wt% methanol aqueous solution at 60 ° C. for 12 hours
(7) Methanol Permeation A film-like sample was immersed in pure water at 25 ° C. for 24 hours and then measured at 20 ° C. using a 1 mol% methanol aqueous solution.

A sample membrane was sandwiched between the H-type cells, and pure water (60 mL) was placed in one cell, and 1 mol% 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.
(8) Nuclear magnetic resonance spectrum (NMR)
NMR measurement was performed under the following measurement conditions to confirm the monomer structure.

Apparatus: EX-270 manufactured by JEOL Ltd.
Resonance frequency: 270 MHz
Measurement temperature: room temperature Dissolving solvent: DMSO-d6
Internal reference material: TMS (0 ppm)
Synthesis example 1
Synthesis of 2,2′-bis (4-hydroxyphenyl) -6,6′-bibenzimidazole represented by the following general formula (G1)

In a 500 ml flask equipped with a stirrer, thermometer and distillation tube, 3,3′-diaminobenzidine and 4-hydroxybenzoic acid were added, and polyphosphoric acid was added while washing the wall of the flask. Thereafter, the internal temperature was gradually raised to 175 ° C. and stirred for 24 hours. Methanol was added to precipitate and isolated by filtration. Water and methanol were added thereto to remove excess polyphosphoric acid and unreacted 4-hydroxybenzoic acid. The crude product was recrystallized with NMP to obtain G1. This crystal was analyzed by GC and found to be 99.8% pure.
Synthesis example 2
Synthesis of 2,2′-bis (4-fluorophenyl) -6,6′-bibenzimidazole represented by the following general formula (G2)

In a 500 ml flask equipped with a stirrer, thermometer and distillation tube, 3,3'-diaminobenzidine and 4-fluorobenzoic acid were added, and polyphosphoric acid was added while washing the flask wall. Thereafter, the internal temperature was gradually raised to 175 ° C. and stirred for 24 hours. Methanol was added to precipitate and isolated by filtration. Water and methanol were added thereto, and excess polyphosphoric acid and unreacted 4-fluorobenzoic acid were removed. The crude product was recrystallized with NMP to obtain G1. This crystal was analyzed by GC and found to be 99.2% pure.
Synthesis example 3
Synthesis of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone represented by the following general formula (G3)

109.1 g (Aldrich reagent) of 4,4′-difluorobenzophenone was reacted at 100 ° C. for 10 hours in 150 mL of fuming sulfuric acid (50% SO ₃ ) (Wako Pure Chemicals reagent). 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 resulting precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone represented by the above general formula (G3). The purity was 99.3%. The structure was confirmed by ¹ H-NMR. Impurities were quantitatively analyzed by capillary electrophoresis (organic matter) and ion chromatography (inorganic matter).
Synthesis example 4
Synthesis of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane (K-DHBP) represented by the formula (r4) In a 500 ml flask equipped with a stirrer, a thermometer and a distillation tube, 4,4'-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate and 0.50 g of p-toluenesulfonic acid monohydrate are charged and dissolved. Thereafter, the mixture was stirred while maintaining at 78 to 82 ° C. for 2 hours. Further, the internal temperature was gradually raised to 120 ° C. and heated until the distillation of methyl formate, methanol, and trimethyl orthoformate completely stopped. After cooling this reaction liquid to room temperature, the reaction liquid was diluted with ethyl acetate, the organic layer was washed with 100 ml of 5% aqueous potassium carbonate solution and separated, and then the solvent was distilled off. Crystals were precipitated by adding 80 ml of dichloromethane to the residue, filtered and dried to obtain 52.0 g of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane. GC analysis of the crystals revealed 99.8% 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane and 0.2% 4,4'-dihydroxybenzophenone.

Example 1
Synthesis and evaluation of a polymer electrolyte material represented by the following general formula (J1), and preparation and evaluation of a polymer electrolyte membrane

(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.)
In a 500 mL three-necked flask equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap, 6.9 g of potassium carbonate (Aldrich reagent, 50 mmol), 13.4 g (38 mmol) of 4,4′-dihydroxytetraphenylmethane, 4,4 '-Difluorobenzophenone 4.4 g (Aldrich reagent, 20 mmol), 0.84 g (2.0 mmol) of the bisphenol monomer obtained in Synthesis Example 1, and disodium 3,3'-disulfonate-4 obtained in Synthesis Example 3 , 4′-difluorobenzophenone 8.9 g (21 mmol) was added, and after nitrogen replacement, dehydration was performed at 180 ° C. in 60 mL of N-methylpyrrolidone (NMP) and 40 mL of toluene, and the temperature was raised to remove toluene. Polymerization was performed. Purification was performed by reprecipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (J1). The weight average molecular weight of the obtained polymer electrolyte material was 450,000, and the sulfonic acid group density after membrane formation and proton substitution (details will be described later) was 1.4 mmol / g.

  A 20 wt% N-methylpyrrolidone (NMP) solution in which the obtained polymer electrolyte material was dissolved was casted on a glass substrate to obtain a polymer electrolyte membrane. Furthermore, after drying at 100 ° C. for 4 hours, heat treatment was performed at 350 ° C. for 10 minutes under nitrogen to obtain a polymer electrolyte membrane. This was immersed in 1N hydrochloric acid at 25 ° C. for 24 hours for proton substitution, and then sufficiently immersed in a large excess amount of pure water for 24 hours for washing.

  The obtained polymer electrolyte membrane had a thickness of 32 μm. 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 heat-resistant methanol property.

Example 2
Synthesis and evaluation of polymer electrolyte material represented by the following formula (J2), and creation and evaluation of polymer electrolyte membrane

(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.)
To a 500 mL three-necked flask equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap, 6.9 g of potassium carbonate (Aldrich reagent, 50 mmol), 9,9′-bis (4-hydroxyphenyl) fluorene (38 mmol), 4, 4.4 g (Aldrich reagent, 20 mmol) of 4′-difluorobenzophenone, 0.84 g (2.0 mmol) of the bisphenol monomer obtained in Synthesis Example 1, and disodium 3,3′-disulfonate obtained in Synthesis Example 3 8.9 g (21 mmol) of 4,4′-difluorobenzophenone was added, and after nitrogen replacement, dehydration was performed at 180 ° C. in 60 mL of N-methylpyrrolidone (NMP) and 40 mL of toluene. Time polymerization was performed. Purification was performed by reprecipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (J2). The obtained polymer electrolyte material had a weight average molecular weight of 350,000, and the sulfonic acid group density after membrane formation and proton substitution (details will be described later) was 1.4 mmol / g.

The polymer electrolyte membrane obtained in the same manner as in Example 1 had a thickness of 31 μm. 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 heat-resistant methanol property.
Example 3
Synthesis and evaluation of a polymer electrolyte material represented by the following general formula (J3), and preparation and evaluation of a polymer electrolyte membrane

(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.)
In a 500 mL three-necked flask equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap, 6.9 g of potassium carbonate (Aldrich reagent, 50 mmol), 14.1 g (40 mmol) of 4,4′-dihydroxytetraphenylmethane, 4,4 '-Difluorobenzophenone 4.2 g (Aldrich reagent, 19 mmol), aromatic dihalide monomer 0.84 g (2.0 mmol) obtained in Synthesis Example 2, and disodium 3,3′-di-acid obtained in Synthesis Example 3 Add 8.5 g (20 mmol) of sulfonate-4,4′-difluorobenzophenone, purge with nitrogen, dehydrate at 180 ° C. in 60 mL of N-methylpyrrolidone (NMP) and 40 mL of toluene, and then elevate the temperature to remove toluene, 230 ° C. For 12 hours. Purification was performed by reprecipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (J3). The weight average molecular weight of the obtained polymer electrolyte material was 400,000, and the sulfonic acid group density after membrane formation and proton substitution (details will be described later) was 1.3 mmol / g.

The polymer electrolyte membrane obtained in the same manner as in Example 1 had a thickness of 32 μm. 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 heat-resistant methanol property.
Example 4
Synthesis and evaluation of a polymer electrolyte material represented by the following general formula (J4), and preparation and evaluation of a polymer electrolyte membrane

(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.)
In a 500 mL three-necked flask equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap, 6.9 g of potassium carbonate (Aldrich reagent, 50 mmol), 9.81 g (38 mmol) of K-DHBP obtained in Synthesis Example 4, 4, 4 '-Difluorobenzophenone 4.4 g (Aldrich reagent, 20 mmol), 0.84 g (2.0 mmol) of the bisphenol monomer obtained in Synthesis Example 1, and disodium 3,3'-disulfonate-4 obtained in Synthesis Example 3 , 4′-difluorobenzophenone 8.9 g (21 mmol) was added, and after nitrogen replacement, dehydration was performed at 180 ° C. in 60 mL of N-methylpyrrolidone (NMP) and 40 mL of toluene, and the temperature was raised to remove toluene. Polymerization was performed. Purification was performed by reprecipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (J4). The weight average molecular weight of the obtained polymer electrolyte material was 450,000, and the sulfonic acid group density after membrane formation and proton substitution (details will be described later) was 1.4 mmol / g.

The obtained 25 wt% N-methylpyrrolidone (NMP) solution in which the soluble polymer electrolyte material for molding of the formula (J4) was dissolved was subjected to pressure filtration using a glass fiber filter, and then cast onto a glass substrate. After drying at 100 ° C. for 4 hours, the temperature was raised to 300 ° C. over 30 minutes under nitrogen and heat treated at 300 ° C. for 10 minutes to obtain a film. The solubility of the polymer was very good. After being immersed in 6N hydrochloric acid at 95 ° C. for 24 hours for proton substitution and deprotection, it was immersed in a large excess of pure water for 24 hours and washed sufficiently to obtain a polymer electrolyte membrane. The obtained polymer electrolyte membrane had a thickness of 32 μm. 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 heat-resistant methanol property.
Example 5
Synthesis and evaluation of polymer electrolyte material represented by the following general formula (J5), and preparation and evaluation of polymer electrolyte membrane

(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.)
In a 500 mL three-necked flask equipped with a stirrer, a nitrogen introducing tube, and a Dean-Stark trap, 6.9 g of potassium carbonate (Aldrich reagent, 50 mmol), 10.33 g (40 mmol) of K-DHBP obtained in Synthesis Example 4, 4, 4 '-Difluorobenzophenone 4.2 g (Aldrich reagent, 19 mmol), aromatic dihalide monomer 0.84 g (2.0 mmol) obtained in Synthesis Example 2, and disodium 3,3′-di-acid obtained in Synthesis Example 3 Add 8.5 g (20 mmol) of sulfonate-4,4′-difluorobenzophenone, purge with nitrogen, dehydrate at 180 ° C. in 60 mL of N-methylpyrrolidone (NMP) and 40 mL of toluene, and then elevate the temperature to remove toluene, 230 ° C. For 12 hours. Purification was performed by reprecipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (J3). The weight average molecular weight of the obtained polymer electrolyte material was 400,000, and the sulfonic acid group density after membrane formation and proton substitution (details will be described later) was 1.3 mmol / g.

  The obtained 25 wt% N-methylpyrrolidone (NMP) solution in which the soluble polymer electrolyte material for molding of the formula (J5) was dissolved was subjected to pressure filtration using a glass fiber filter, and then cast onto a glass substrate. After drying at 100 ° C. for 4 hours, the temperature was raised to 300 ° C. over 30 minutes under nitrogen and heat treated at 300 ° C. for 10 minutes to obtain a film. The solubility of the polymer was very good. After being immersed in 6N hydrochloric acid at 95 ° C. for 24 hours for proton substitution and deprotection, it was immersed in a large excess of pure water for 24 hours and washed sufficiently to obtain a polymer electrolyte membrane. The obtained polymer electrolyte membrane had a thickness of 32 μm. 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 heat-resistant methanol property.

Comparative Example 1
A commercially available Nafion (registered trademark) 117 membrane (manufactured by DuPont) was used to evaluate ion conductivity, hot water resistance, MCO, and hot methanol resistance. The Nafion (registered trademark) 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 evaluation results are summarized in Table 1.

    Comparative Example 2

(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.)
A polymer electrolyte membrane was prepared by the method described in Example 1, except that the polymer electrolyte material of the formula (J1) obtained in Example 1 was changed to the polymer of the formula (J4).

  The obtained polymer electrolyte membrane had a thickness of 38 μm. The evaluation results are summarized in Table 1. There was not much suppression effect of methanol crossover. Moreover, heat-resistant methanol property was insufficient.

  Each evaluation result of Examples 1-5 and Comparative Examples 1-2 is shown in Table 1. The membranes of Examples 1 to 5 had a greater effect of suppressing methanol crossover than the Nafion (registered trademark) 117 membrane of Comparative Example 1, and were excellent in heat-resistant methanol resistance. Further, although having the same level of sulfonic acid group as compared with the membrane of Comparative Example 2, the effect of suppressing methanol crossover was great and the heat resistant methanol resistance was also excellent.

  The electrolyte membrane of 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 use of the polymer electrolyte fuel cell of the present invention is not particularly limited, but mobile devices such as mobile phones, personal computers, PDAs, video cameras, digital cameras, home appliances such as cordless vacuum cleaners, toys, electric bicycles, automatic It is preferably used as a power supply source for vehicles such as motorcycles, automobiles, buses, trucks, etc., moving bodies such as ships, railways, etc., conventional primary batteries such as stationary generators, alternatives to secondary batteries, or hybrid power sources with these. .

Claims (11)

A monomer structure having an acidic group, a monomer structure having a basic group in the main chain, and a neutral monomer structure are contained as a copolymer structure, and the monomer structure having an acidic group is represented by the following general formula (Q1-s). An ionic group-containing polymer electrolyte material, wherein the basic group is a heterocyclic ring containing nitrogen selected from the following general formulas (N1) to (N8).

(In the general formula (Q1 -s), ^{X 1} is -CO -, - SO ₂ -, or -P (Rp) O- (Rp any Yusanmoto is), ^{M 1} and ^{M 2} is hydrogen, a metal cation , Ammonium cation, a1 and a2 represent an integer of 1 to 4.)

  The polymer electrolyte material according to claim 1, wherein the copolymer is an aromatic polyether copolymer. The polymer electrolyte material according to claim 1 or 2, wherein the general formula (Q1-s) is the following general formula (Q2-s).

(In the general formula (Q2-s), M ³ and M ⁴ represent hydrogen, a metal cation, or an ammonium cation.)   The polymer electrolyte material according to any one of claims 1 to 3, wherein the content mole fraction W1 of the monomer structure having an acidic group is 2 mol% or more and 40 mol% or less. The polymer electrolyte material according to any one of claims 1 to 4, wherein the monomer structure having a basic group in the main chain is a compound structure represented by the following general formula (Q3-s).

  The polymer electrolyte material according to any one of claims 1 to 5, wherein the content mole fraction W2 of the monomer structure having a basic group in the main chain is 0.5 mol% or more and 15 mol% or less. .   The ratio W2 / W1 of the content mole fraction of the monomer structure having an acidic group and the monomer structure having a basic group in the main chain is 0.02 to 0.4. The polymer electrolyte material described in 1. The polymer electrolyte material according to any one of claims 1 to 7, wherein the neutral monomer structure is at least one compound structure selected from the following general formulas (Ar1-1) to (Ar1-6).

  A polymer electrolyte membrane comprising the polymer electrolyte material according to claim 1.   A membrane electrode assembly comprising the polymer electrolyte material according to any one of claims 1 to 8.   A solid polymer fuel cell comprising the polymer electrolyte material according to claim 1.