JP5315877B2 - Polymer electrolyte material and polymer electrolyte fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte material excellent in proton conductivity, a fuel cutoff property, mechanical strength, hot water resistance, hot methanol resistance, workability, and chemical stability, and to provide a polymer electrolyte fuel cell using the same. <P>SOLUTION: The polymer electrolyte material is an aromatic polyether polymer having a constitutional unit represented by general formula (1), (2), or (3). In general formulas (1), (2), or (3), R represents a hydrogen atom, an alkali metal atom, an alkali earth metal atom, or a 1-20C hydrocarbon radical. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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 fuel cell using the same.

  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. The polymer electrolyte membrane is mainly composed of a polymer electrolyte material. The polymer electrolyte material is also used as a binder for the electrode catalyst layer.

  The required characteristics of the polymer electrolyte membrane include firstly high proton conductivity. 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.

  Until now, Nafion (registered trademark) (Nafion (registered trademark): manufactured by DuPont), which is a perfluorosulfonic acid polymer, has been widely used for the polymer electrolyte membrane. 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. Perfluorosulfonic acid-based membranes have characteristics that are generally balanced as polymer electrolyte membranes, but further improvements in properties have been required as the batteries are put into practical use.

  In order to overcome such drawbacks, several efforts have already been made on polymer electrolyte materials based on non-perfluoropolymer hydrocarbon polymers. As the polymer skeleton, aromatic polyether ketone and aromatic polyether sulfone have been particularly actively studied from the viewpoint 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. (Hereinafter, 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. When the content of ionic groups is increased to increase conductivity, the created membrane swells, and fuel crossover such as methanol is large. There are cormorants problems, also due to the low cohesive force of polymer molecular chains, poor stability of the conformation, there is a problem that insufficient mechanical strength and physical durability of the film produced.

  Moreover, in the sulfonated product (for example, Patent Documents 1 and 2) of an aromatic polyether ketone (hereinafter sometimes abbreviated as PEK) (including Victrex PEEK-HT (manufactured by Victrex)). A polymer having a low sulfonic acid group density composition due to its high crystallinity has the problem that crystals remain insoluble in a solvent due to residual crystals, resulting in poor processability. Conversely, if the sulfonic acid group density is increased to improve processability, Since the polymer was not crystalline, it swelled remarkably in water, resulting in not only a large fuel crossover but also an insufficient strength of the membrane produced.

  As a method for controlling the amount of sulfonic acid groups, in aromatic polyether sulfone systems, there have been reports of sulfonated aromatic polyether sulfones in which the amount of sulfonic acid groups is controlled by polymerization using monomers introduced with sulfonic acid groups. (For example, refer to Patent Document 3). However, here too, the problem of swelling of the film prepared under high temperature and high humidity is not improved, and this tendency is particularly remarkable in a fuel aqueous solution such as methanol or in a composition having a high sulfonic acid group density. In addition, it has been difficult for a polymer electrolyte membrane having poor heat resistance and methanol resistance to sufficiently suppress fuel crossover such as methanol and to provide mechanical strength that can withstand a swelling and drying cycle.

  Patent Documents 4, 5, and 6 describe an aromatic polyarylene polymer having a structural unit represented by the following formulas (H1), (H2), and (H3). However, here, the degree of difficulty of polymerization is high and the productivity is poor.

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. JP-A-6-93114 Japanese translation of PCT publication No. 2004-528683 US Patent Application Publication No. 2002/0091225 JP 2006-298794 A JP 2006-299015 A JP 2006-299080 A

  In view of the background of such prior art, the present invention is excellent in proton conductivity and excellent in fuel cutoff, mechanical strength, hot water resistance, hot methanol resistance, workability, chemical stability, and polymer electrolyte type It is an object of the present invention to provide a polymer electrolyte material that can achieve high output, high energy density, and long-term durability when used as a fuel cell, and a polymer electrolyte fuel cell comprising the same.

  In the prior art, the method of introducing sulfonic acid groups onto the aromatic ring by polymer sulfonation reaction (polymer reaction) has the problem that the amount and position of the sulfonic acid groups introduced into the polymer cannot be precisely controlled. Therefore, mass production of the polymer has been difficult. Therefore, focusing on the synthesis of a polymer electrolyte material having an ionic group in the side chain as a polymer electrolyte material having an ionic group, an attempt to synthesize a polymer using a monomer having a plurality of sulfonic acid groups substituted in the side chain, The membrane thus prepared was considered for fuel cell use, and the relationship between mechanical property evaluation, hot water resistance, heat resistant methanol property, processability, etc. was studied, and the present invention was completed.

The present invention employs the following means in order to solve the above problems. That is, the polymer electrolyte material of the present invention is represented by the following general formula (2) or (3) and a constitutional unit represented by the aromatic polyether-based high consisting of structural units represented by the general formula (K1) which will be described later It is a molecular electrolyte membrane . Moreover, the structural unit represented by the following general formula (2) or (3), the structural unit represented by the general formula (K1) described later, and the structural unit represented by the general formula (X-21) described later An aromatic polyether polymer electrolyte membrane comprising: The polymer electrolyte fuel cell of the present invention is characterized by using such a polymer electrolyte material.

(In general formulas ( 2) and (3), R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms.)

  According to the present invention, it has excellent proton conductivity, excellent fuel barrier properties, mechanical strength, hot water resistance, hot methanol resistance, processability, chemical stability, and a polymer electrolyte fuel cell. A polymer electrolyte material that can achieve high output, high energy density, and long-term durability, and a polymer electrolyte fuel cell comprising the same can be provided.

Hereinafter, the present invention will be described in detail first. The present invention has the above-described problems, that is, excellent proton conductivity, fuel barrier property, mechanical strength, hot water resistance, heat resistant methanol property, processability, chemical stability, and a polymer electrolyte fuel cell. Occasionally, a polyelectrolyte material capable of achieving high output, high energy density, and long-term durability is intensively studied, and an aromatic polyether having a structural unit represented by the following general formula ( 2) or (3) As a result of polymerizing a polymer, it has been found that a polymer electrolyte material can be provided that solves such problems all at once.

(In general formulas ( 2) and (3), R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms.)
The polymer electrolyte material of the present invention includes membranes (including films and films), plates, fibers, hollow fibers, particles, lumps, micropores, coatings, foams, etc. It can take various forms depending on the intended use. The polymer can be applied to a wide range of applications because it can improve the design freedom of the polymer and various properties such as mechanical properties and solvent resistance. It is particularly suitable when the polymer electrolyte material is a membrane. Hereinafter, the case of the polymer electrolyte membrane will be described.

  When conventional sulfonated aromatic polyether ketone or sulfonated aromatic polyethersulfone is used as a polymer electrolyte material, the membrane swells when the content of ionic groups is increased to increase proton conductivity, There was a problem that the fuel crossover of methanol or the like was large, and a problem that the mechanical strength of the membrane and the stability of the higher order structure were insufficient due to the low cohesion of the polymer molecular chains.

  On the other hand, the polymer electrolyte material of the present invention is characterized by a structure having a plurality of sulfonic acid groups at a high concentration in a highly rigid side chain. Thereby, even if sulfonic acid groups are introduced at a high concentration, a solid polymer electrolyte excellent in proton conductivity can be obtained without impairing hot water resistance and mechanical strength.

  In order to improve the packing of molecular chains of the polymer, and to give intermolecular cohesion and crystallinity again, the crystalline monomer is substituted with a protective group to be soluble and polymerized, and after being formed into a film or the like , At least a part may be deprotected. In that case, a polymer electrolyte membrane with greatly improved solvent resistance such as hot water resistance and methanol resistance, mechanical properties such as tensile strength and elongation, tear strength and fatigue resistance, and fuel barrier properties such as methanol and hydrogen. Can be obtained. Through this manufacturing process, the polymer electrolyte membrane of the present invention, in particular, has not only high proton conductivity but also film-forming properties (workability), manufacturing costs, hot water resistance, methanol resistance, fuel barrier properties, and mechanical properties. It has the feature that it can.

  In addition, the polymer electrolyte membrane obtained by the present invention has a property that is very difficult to break even in a water-containing state due to its strong intermolecular cohesion, that is, has a high tear strength, and repeats swelling and drying. It has a feature that it can achieve extremely excellent long-term durability even under the operating conditions of a polymer electrolyte fuel cell using hydrogen as a fuel used in an automobile or the like.

  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. .

  Moreover, in this invention, 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 respectively 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 the electrolyte polymer used in the polymer electrolyte fuel cell.

  The polymer electrolyte material used in the present invention is more preferably a polymer having an aromatic ring in the main chain among hydrocarbon polymers from the viewpoints of mechanical strength and chemical stability. That is, it is a polymer having an aromatic ring in the main chain and having an ionic group in the side chain. 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 present invention include polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, At least one of structural components such as polyarylene ketone, polyether ketone, polyarylene phosphine oxide, polyether phosphine oxide, polybenzoxazole, polybenzthiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, polyimidesulfone, etc. The polymer containing is mentioned.

  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 represent an organic group containing an aromatic ring, and each may represent two or more groups. At least one of Z ¹ and Z ² is ionic.) 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 represent an organic group containing an aromatic ring, and each may represent two or more groups. At least one of Z ¹ and Z ² is ionic.) A and b each independently represents 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 method for synthesizing the aromatic polyether polymer used in the present invention is not particularly limited as long as it is a method capable of substantially increasing the molecular weight. For example, the aromatic active dihalide compound and 2 It can be synthesized using an aromatic nucleophilic substitution reaction of a polyhydric phenol compound or an aromatic nucleophilic substitution reaction of a halogenated aromatic phenol compound.

Specifically, for example, an aromatic polyether polymer containing the structural unit represented by the general formula ( 2) or (3) is represented by the following general formula ( S2) or (S3) as an aromatic active dihalide compound. It is possible to synthesize by an aromatic nucleophilic substitution reaction with a dihydric phenol compound. Although the structural unit represented by the general formula ( 2) or (3) may be derived from either the divalent phenol compound or the aromatic active dihalide compound, it is derived from the aromatic active dihalide compound in consideration of the reactivity of the monomer. Is more preferable.

(In general formulas ( S2) and (S3), R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms, and X represents a halogen atom.)
The aromatic active dihalide compound having no ionic group is not particularly limited as long as it can be increased in molecular weight by aromatic nucleophilic substitution reaction with a divalent phenol compound. More preferable specific examples of the aromatic active dihalide compound include 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-dichlorodiphenyl ketone, 4,4′-difluorodiphenyl ketone, 4,4′-dichlorodiphenylphenylphosphine oxide, 4,4′-difluorodiphenylphenylphosphine oxide, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile and the like can be mentioned. Among these, 4,4′-dichlorodiphenyl ketone and 4,4′-difluorodiphenyl ketone are more preferable in terms of imparting crystallinity, mechanical strength, heat-resistant methanol property, and fuel crossover suppressing effect, and 4,4 ′ from the viewpoint of polymerization activity. -Difluorodiphenyl ketone 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.

  As a polymer electrolyte material containing an aromatic ring having a t-butyl group synthesized using 4,4′-dichlorodiphenyl ketone or 4,4′-difluorodiphenyl ketone as an aromatic active dihalide compound, the following general formula It further includes a component represented by (K1), becomes a component that imparts intermolecular cohesive strength and crystallinity, and has high dimensional stability and mechanical strength at high temperatures in methanol water used as fuel, and also uses hydrogen as fuel. The polymer electrolyte fuel cell is preferably used because it is an effective component for a material having high tear strength and excellent resistance to repeated swelling and drying.

(The structural unit represented by the general formula (K1) may be optionally substituted, but does not contain an ionic group.)
As the aromatic polyether polymer used in the present invention, a monomer having a protective group is preferably used in combination with the structural unit represented by the general formula ( 2) or (3) and the general formula (K1). The More preferably, the structural unit containing a protecting group contains at least one selected from the following general formulas (K2) and (K3).

(In General Formulas (K2) and (K3), 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, and R ₃ is any And E represents O or S, each of which may represent two or more groups, and the groups represented by the general formulas (K2) and (K3) may be optionally substituted.)
Among them, in the general formulas (K2) and (K3), E is O in terms of the odor, reactivity, stability, etc. of the compound, that is, the ketone moiety is protected / deprotected with an acetal or ketal moiety. The method is most preferred. It is preferable to use a compound in which a protective group is introduced into a dihydric phenol compound as a monomer because crystallinity can be imparted after molding and mechanical strength can be improved. The structural units represented by the general formulas (K2) and (K3) may be derived from either the divalent phenol compound or the aromatic active dihalide compound. However, in consideration of the reactivity of the monomer, It is more preferable to do this.

(In the general formulas (K2-1) and (K3-1), 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 (K2-1) and the general formula (K3-1) may be optionally substituted.
Specific examples of particularly preferred dihydric phenol compounds used in the present invention include compounds represented by the following general formulas (r1) to (r10), and derivatives derived from these dihydric phenol compounds.

  Among these dihydric phenol compounds, the compounds represented by the general formulas (r4) to (r10) are more preferable from the viewpoint of stability, and more preferably the compounds represented by the general formulas (r4), (r5), and (r9). The compound represented by the general formula (r4) is most preferred.

  In terms of proton conductivity and hydrolysis resistance, a sulfonic acid group is most preferable as an ionic group, but the monomer having an ionic group used in the present invention may have another ionic group. . In addition, the polymer electrolyte material obtained in the present invention has a high crystallinity characteristic possessed by a ketone group, and a component superior in heat-resistant methanol property to a sulfone group. Since it becomes an effective component for the material excellent in dimensional stability and mechanical strength, it is used more preferably. 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 the case of obtaining an aromatic polyether polymer, the halogenated aromatic hydroxy compound is not particularly limited, but 4-hydroxy-4′-chlorobenzophenone, 4-hydroxy-4′-fluoro. Benzophenone, 4-hydroxy-4′-chlorodiphenylsulfone, 4-hydroxy-4′-fluorodiphenylsulfone, 4- (4′-hydroxybiphenyl) (4-chlorophenyl) sulfone, 4- (4′-hydroxybiphenyl) ( Examples include 4-fluorophenyl) sulfone, 4- (4′-hydroxybiphenyl) (4-chlorophenyl) ketone, 4- (4′-hydroxybiphenyl) (4-fluorophenyl) ketone, and the like. These can be used alone or can be used as a mixture of two or more. Further, in the reaction of the activated dihalogenated aromatic compound and the aromatic dihydroxy compound, these halogenated aromatic hydroxy compounds may be reacted together to synthesize an aromatic polyether compound.

  In the present invention, the dihydric phenol compound used together with the dihydric phenol compound represented by the general formulas (K2-1) and (K3-1) or used alone is not particularly limited, Can be selected as appropriate in consideration of properties, fuel cutoff, mechanical strength, and the like.

  Preferable specific examples of the dihydric phenol residue to be used include divalent phenol residues represented by the following general formulas (X-1) to (X-28). In the specification of the present invention, the dihydric phenol residue means a structural unit remaining after the corresponding dihydric phenol compound reacts with the aromatic active dihalide.

  (N and m are integers of 1 or more, and Rp represents an arbitrary organic group.)

  These may have a substituent and an ionic group. Those having an aromatic ring in the side chain are also preferred specific examples. Moreover, these can also be used together as needed.

  Among these, the dihydric phenol residue represented by the general formulas (X-1) to (X-17) is a dihydric phenol residue that can improve crystallinity depending on the method of use. Due to the improvement in crystallinity, the polymer electrolyte material obtained in the present invention can be preferably used because it can exhibit performances excellent in mechanical properties, solvent resistance, fuel cutoff properties, long-term durability, and the like. Among these, a dihydric phenol residue represented by the general formulas (X-1) to (X-5), (X-7), (X-14), and (X-17) is most preferable, Preferably, it is a dihydric phenol residue represented by general formulas (X-1) to (X-5).

  Moreover, since the dihydric phenol residue represented by the general formulas (X-18) to (X-28) has an effect of increasing hydrophobicity or rigidity, the fuel permeation suppressing effect is large, and the dimensional stability in the fuel is improved. It can be preferably used because it is effective in improving the properties. Among them, more preferred are those represented by the general formula (X-21) and the general formula (X-22), and particularly preferred is a dihydric phenol residue represented by the general formula (X-21). .

In the polymer electrolyte material obtained in the present invention, the content of the structural unit selected from the general formula ( 2) or (3) is not particularly limited, but is larger in terms of proton conductivity. It is preferable.

It is preferable that the content of the aromatic active dihalide compound consisting of the general formulas ( S2) and (S3) is 20 mol% or more. Especially, it is preferable that it is 30 mol or more from a viewpoint of proton conductivity, and it is preferable that it is less than 50 mol% from the point of mechanical characteristics, a fuel crossover suppression effect, and dimensional stability. When the structural unit represented by the general formula ( 2) or (3) is contained in an amount of 50 mol% or more, the breaking strength, elastic modulus, hot water resistance, and fuel crossover suppressing effect may be insufficient.

  In the polymer electrolyte membrane obtained by the present invention, it is more preferable that all of the protecting groups substituted on the aromatic ring are deprotected particularly from the viewpoint of mechanical strength, heat resistance methanol resistance and fuel crossover suppression effect. However, a part of the protecting group substituted with the aromatic ring may remain as long as it does not adversely affect the hot water resistance, hot methanol resistance and fuel crossover suppression effect. Here, the fact that all of the protecting groups substituted on the aromatic ring are deprotected means that the remaining amount of the protecting group is below the detection limit.

  As content of the protective group contained in the soluble polymer electrolyte material for molding used in the present invention, for example, when the general formula (K2-1) is used as the divalent phenol compound, the total of the divalent phenol compounds The total molar amount of the general formula (K2-1) is preferably 5 mol% or more with respect to the molar amount. If the total molar amount of the said general formula (K2-1) is less than 5 mol%, solubility may become insufficient and film forming property may become inadequate. The molar amount of the general formula (K2-1) is more preferably 30 mol% or more, and further preferably 45 mol% or more in terms of the effect of improving solubility. A material containing a large amount of the structural unit represented by the general formula (K2) is excellent in solubility and workability, and therefore, in producing an extremely tough polymer electrolyte membrane, a soluble polymer electrolyte material for molding thereof. Can be used particularly preferably.

  In the main chain skeleton structure of the polymer electrolyte molded body obtained in the present invention, it exhibits crystallinity from its good packing and extremely strong intermolecular cohesive force, and has the property of not dissolving in a general solvent at all. In view of tensile strength and elongation, tear strength, and fatigue resistance, aromatic polyether ketone (PEK) -based polymers, that is, those having a repeating unit represented by the general formula (T1-3) are particularly preferable. Here, the aromatic polyether ketone polymer is a general term for polymers having at least an ether bond or a ketone bond in the molecular chain, and is a polyether ketone, a polyether ketone ketone, a polyether ether ketone, a polyether. It includes ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone, polyether ketone phosphine oxide, polyether ketone nitrile and the like, and does not limit the specific polymer structure. Those containing a large amount of phosphine oxide or nitrile may have insufficient solvent solubility in a soluble polymer electrolyte material for molding containing a protecting group. May have insufficient solvent resistance.

(Here, Z ¹ and Z ² each represent an organic group containing an aromatic ring, and each may represent two or more groups. At least one of Z ¹ and Z ² is ionic.) A and b each independently represents a positive integer.)
Preferred organic groups as Z ¹ and Z ² are a phenylene group, a naphthylene group, and a biphenylene group. These may be substituted, but unsubstituted ones are more preferable in terms of imparting crystallinity. Furthermore, a phenylene group is preferable, and a p-phenylene group is most preferable.

  In the present invention, it is more preferable to use a compound having an ionic acid group introduced as a monomer because the amount of the ionic group can be precisely controlled.

  The polyelectrolyte material obtained by the present invention has a higher-order structure different from the sulfonated product of the conventional crystalline polymer, and gives solubility to the crystalline polymer to obtain a uniform and tough membrane. Is.

  Polymerization by the aromatic nucleophilic substitution reaction to obtain the aromatic polyether polymer used in the present invention 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. Solvents that can be used include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphontriamide and the like. However, it is not limited to these, and any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction may be used. 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.

  Azeotropic agents used to remove reaction water or water introduced during the reaction generally do not substantially interfere with polymerization, co-distill with water and boil between about 25 ° C and about 250 ° C. Any inert compound. Common azeotropic agents include benzene, toluene, xylene, chlorobenzene, methylene chloride, dichlorobenzene, trichlorobenzene and the like. Of course, it is beneficial to select an azeotropic agent whose boiling point is lower than that of the dipolar solvent used. An azeotropic agent is commonly used, but it is not always necessary when high reaction temperatures are used, such as temperatures above 200 ° C., especially when the inert gas is continuously sparged into the reaction mixture. In general, it is desirable to carry out the reaction in an inert atmosphere and in the absence of oxygen.

  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, by adding the reaction solution to a solvent having low polymer solubility and high by-product inorganic salt solubility, the inorganic salt is removed, the polymer is precipitated as a solid, and the polymer is obtained by filtering the precipitate. You can also. The recovered polymer is optionally washed with water, alcohol or other solvent and dried. Once the desired molecular weight is obtained, halide or phenoxide end groups can optionally be reacted by introducing a phenoxide or halide end-capping agent that forms a stable end group.

  In the case where a crystalline monomer is used in the present invention, it is necessary to introduce the protective group without deprotecting from the viewpoint of processability until the film-forming stage, so the conditions under which the protective group can exist stably are considered. Thus, it is necessary to perform polymerization and purification. Since the protecting group substituted on the aromatic ring undergoes a deprotection reaction under acidic conditions, it is necessary to keep the system neutral or alkaline.

  The deprotection reaction can be performed in the presence of water and acid under non-uniform or uniform conditions, but from the viewpoint of mechanical strength and solvent resistance, a method of acid treatment after molding into a film or the like Is more preferable. Specifically, it is possible to deprotect the molded membrane by immersing it in an aqueous hydrochloric acid solution, and the acid concentration and the aqueous solution temperature can be appropriately selected.

  The weight ratio of the acidic aqueous solution required for the polymer is preferably 1 to 100 times, but a larger amount of water can be used. The acid catalyst is preferably used at a concentration of 0.1 to 50% by weight of water present. Suitable acid catalysts include strong mineral acids such as hydrochloric acid, nitric acid, fluorosulfonic acid, sulfuric acid, and strong organic acids such as p-toluenesulfonic acid, trifluoromethane sulfonic acid, and the like. Depending on the film thickness of the polymer and the like, the amount of acid catalyst and excess water, reaction pressure, and the like can be selected as appropriate.

  For example, if it is a film with a thickness of 50 μm, it can be easily deprotected by immersing it in an acidic aqueous solution as exemplified by a 6N hydrochloric acid aqueous solution and heating at 95 ° C. for 1 to 48 hours. It is. Further, even when immersed in a 1N aqueous hydrochloric acid solution at 25 ° C. for 24 hours, most of the protecting groups can be deprotected. However, the deprotection conditions are not limited to these, and the deprotection may be performed with an acid gas, an organic acid, or the like, or may be deprotected by heat treatment.

  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. In addition, since the polymer electrolyte material obtained by the present invention is insoluble in a solvent, it may be difficult to measure the molecular weight.

  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.

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

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

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

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

  Here, the sulfonic acid group density is the number of moles of sulfonic acid groups introduced per gram of the dried polymer electrolyte membrane, 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 polyelectrolyte material of the present invention includes an embodiment in which the polymer electrolyte material has a complex composed of a polymer having an ionic group and other components, as will be described later. In this case, the sulfonic acid group density is based on the total amount of the complex Suppose that

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 sulfonic acid group density is determined by the following formula.

Sulfonic acid group density (mmol / g) =
[Concentration of sodium hydroxide aqueous solution (mmol / ml) × Drip amount (ml)] / Dry weight of sample (g)
The polymer having an ionic group used in the present invention is not limited to the purpose of the present invention, and other components such as an inert polymer or an organic or inorganic compound having no conductivity or ionic conductivity, May be contained.

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

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

  The method of introducing an ionic group in a polymer reaction will be described with an example. For example, introduction of a phosphonic acid group into an aromatic polymer is described in Polymer Preprints, 51, 2002, p.750, etc. This is possible by the method described. Introduction of a phosphate group into an aromatic polymer can be achieved by, for example, phosphoric esterification of an aromatic polymer having a hydroxyl group. Introduction of a carboxylic acid group into an aromatic polymer can be performed by oxidizing an aromatic polymer having an alkyl group or a hydroxyalkyl group, for example. Introduction of a sulfate group into an aromatic polymer can be achieved by, for example, sulfate esterification of an aromatic polymer having a hydroxyl group.

  As a method for sulfonating an aromatic polymer, that is, a method for introducing a sulfonic acid group, for example, a method described in JP-A-2-16126 or JP-A-2-208322 is known. Specifically, for example, an aromatic polymer can be sulfonated by reacting with a sulfonating agent such as chlorosulfonic acid in a solvent such as chloroform, or by reacting in concentrated sulfuric acid or fuming sulfuric acid. . The sulfonating agent is not particularly limited as long as it sulfonates an aromatic polymer, and sulfur trioxide or the like can be used in addition to the above. When the aromatic polymer is sulfonated by this method, the degree of sulfonation can be easily controlled by the amount of the sulfonating agent used, the reaction temperature and the reaction time. Introduction of a sulfonimide group into an aromatic polymer can be achieved, for example, by a method of reacting a sulfonic acid group and a sulfonamide group.

  The polymer electrolyte material of the present invention preferably has a crystallinity of less than 0.5% as measured by wide angle X-ray diffraction (XRD).

  The polymer electrolyte material having a protecting group used in the present invention is more preferably amorphous and less than 0.5% from the viewpoint of a soluble polymer electrolyte material for molding that requires processability. preferable. When the degree of crystallinity is 0.5% or more, workability is insufficient and a uniform and tough electrolyte membrane may not be obtained. Moreover, since the polymer electrolyte molded body obtained by the present invention is also affected by the crystallinity of the soluble polymer electrolyte material for molding, the crystallinity is more preferably less than 0.5%. When the crystallinity is 0.5% or more, the toughness is insufficient and the long-term durability may be insufficient, which is not preferable.

  The crystallinity measurement of such a polymer electrolyte material by wide-angle X-ray diffraction is performed by the method described in the examples.

  The polymer electrolyte material obtained in the present invention is excellent in solvent resistance from the viewpoint of fuel barrier properties and high energy capacity by using a high concentration fuel, that is, after being immersed in N-methylpyrrolidone at 100 ° C. for 2 hours. More preferably, the weight loss is 70% by weight or less. Alcohols such as methanol are often used as the liquid fuel. In the present invention, the solvent resistance is evaluated using N-methylpyrrolidone having excellent solubility regardless of the polymer type. More preferably, it is 50 weight% or less, Most preferably, it is 30 weight% or less. When the weight loss exceeds 70% by weight, not only the fuel barrier property but also the crystallinity is insufficient, resulting in insufficient mechanical strength and long-term durability, or for DMFC using high-temperature and high-concentration methanol aqueous solution as fuel When used in the above, it is not preferable because the film dissolves or swells greatly. In addition, it becomes difficult to apply a catalyst paste directly to the polymer electrolyte membrane to produce a membrane electrode assembly, which not only increases the manufacturing cost but also increases the interfacial resistance with the catalyst layer, resulting in sufficient power generation. Characteristics may not be obtained.

  The weight loss of such a polymer electrolyte material with respect to N-methylpyrrolidone is measured by the method described in Examples.

  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 at a stage having a t-butyl group is possible. It is. 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.

  The solvent used for film formation is not particularly limited as long as it can dissolve the aromatic polyether polymer and then remove it. For example, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl- Aprotic polar solvents such as 2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphontriamide, ester solvents such as γ-butyrolactone, butyl acetate, ethylene carbonate, propylene carbonate Carbonate solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether and other alkylene glycol monoalkyl ethers, or isopropanol Alcohol solvents such as Le, 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 polymer electrolyte membrane obtained in the present invention is preferably heat-treated in the state of a metal salt at least part of the ionic groups. Further, if the polymer electrolyte material is polymerized in the state of a metal salt at the time of polymerization, it is preferable to perform film formation and heat treatment as it is. 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 1 minute to 1 hour. If the heat treatment temperature is too low, the fuel permeability suppressing effect, elastic modulus, and breaking strength are 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 heat treatment effect 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 barrier properties, mechanical properties, long-term durability, and solvent resistance.

  As a method for converting the polymer electrolyte material used in the present invention into a polymer electrolyte membrane, a membrane composed of the aromatic polyether polymer is prepared by the above method, and then a protective group substituted with an aromatic ring is used. At least a part of it is deprotected. This method makes it possible to form a solution of a low sulfonic acid group polymer with poor solubility, achieving both proton conductivity and a fuel crossover suppression effect, excellent solvent resistance, mechanical properties, and dimensional stability. It becomes possible.

  In the present invention, the method for substituting a protecting group on the aromatic ring and deprotecting part or all of the aromatic ring is not particularly limited, but examples include 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 polymer electrolyte membrane obtained by the present invention can further have a polymer structure crosslinked by means such as radiation irradiation, if necessary. By crosslinking such a polymer electrolyte membrane, an effect of further suppressing fuel crossover and swelling with respect to the fuel can be expected, and the mechanical strength may be improved, which may be more preferable. Examples of such radiation irradiation include electron beam irradiation and γ-ray irradiation.

  The thickness of the polymer electrolyte membrane obtained by 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, the polymer electrolyte membrane obtained by the present invention contains additives such as crystallization nucleating agents, plasticizers, stabilizers, antioxidants or mold release agents used in ordinary polymer compounds. It can be added within a range not contrary to the purpose. Moreover, you may reinforce with a microporous film, a nonwoven fabric, a mesh, etc.

  In addition, the polymer electrolyte membrane obtained by the present invention has various polymers, elastomers, and the like for the purpose of improving mechanical strength, thermal stability, workability, etc. within a range that does not adversely affect the above-mentioned various properties. Fillers, 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 obtained by 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 obtained by 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.

  The polymer electrolyte component in the present invention means a component containing a polymer electrolyte molded body and a polymer electrolyte material. In the present invention, the shape of the polymer electrolyte component is the same as that of the aforementioned polymer electrolyte molded body.

  When the polymer electrolyte material obtained by the present invention is used for a fuel cell, it is suitable for a membrane state and a catalyst layer binder.

  The polymer electrolyte membrane obtained by 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. It is also suitable as an artificial muscle. 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.

  The membrane electrode composite obtained by the present invention means a membrane electrode composite containing the polymer electrolyte material obtained by the present invention in a polymer electrolyte membrane or a catalyst layer. Furthermore, the membrane electrode composite is a component in which a polymer electrolyte membrane and an electrode are combined.

  There is no particular limitation on the method of joining the polymer electrolyte membrane and the electrode when using such a polymer electrolyte membrane as a fuel cell, and a known method (for example, a chemical plating method described in Electrochemistry, 1985, 53, p.269. , Applied Electrochemical Society (J. Electrochem. Soc.), Electrochemical Science and Technology, 1988, 135, 9, p.2209. Is possible.

  In the case of integration by heating press, the temperature and pressure may be appropriately selected depending on the thickness of the polymer electrolyte membrane, the moisture content, the catalyst layer and the electrode substrate. Further, in the present invention, it is possible to form a composite by pressing even when the polymer electrolyte membrane is in a dry state or in a state where water is absorbed. Specific press methods include roll presses that specify pressure and clearance, and flat plate presses that specify pressure. From the viewpoint of industrial productivity and suppression of thermal decomposition of polymer electrolyte materials having ionic groups. It is preferable to perform in the range of 0 ° C to 250 ° C. The pressurization is preferably as weak as possible from the viewpoint of polymer electrolyte membrane and electrode protection. In the case of a flat plate press, a pressure of 10 MPa or less is preferable, and the electrode and the polymer electrolyte membrane are bonded without carrying out the composite by the hot press process. It is one of the preferred options from the viewpoint of preventing short-circuiting of the anode and cathode electrodes to form a stacked fuel cell. In the case of this method, when power generation is repeated as a fuel cell, the deterioration of the polymer electrolyte membrane presumed to be caused by a short-circuited portion tends to be suppressed, and the durability as a fuel cell is improved.

  Also, when heat-pressing above the softening temperature or glass transition temperature of the polymer electrolyte material, if the decomposition temperature of the ionic group is close, it is difficult to adopt a temperature above the softening temperature or glass transition temperature of the polymer electrolyte material. Thus, decomposition can be suppressed by using this ionic group as a metal salt, and hot pressing can be performed at a temperature higher than the softening temperature or glass transition temperature of the polymer electrolyte material. For example, when the ionic group of the polymer electrolyte material such as the binder in the electrode or the polymer electrolyte membrane is a sulfonic acid group, the sulfonic acid Na is used, and proton bonding is performed with hydrochloric acid, sulfuric acid, etc. after joining by heating press. Manufacturing membrane electrode composites.

  It is also a preferable method that an interfacial resistance reducing layer is interposed between the electrode and the polymer electrolyte membrane when the electrode and the polymer electrolyte membrane are combined. These contact areas can be substantially increased by filling at least a part of the fine gap between the electrode and the polymer electrolyte membrane with the interface resistance-reducing layer, and in the gap, fuel or air used as a fuel cell, In addition, it is possible to prevent an increase in resistance due to the ingress of generated water or carbon dioxide. In addition, the interfacial resistance reducing composition penetrates into the cracks generated in the catalyst layer of the electrode, and the inner wall surface of the crack of the catalyst layer that could not be used for power generation can be used effectively. The contact area can be increased. As a result, the resistance of the membrane electrode assembly decreases, the power density increases, and a high-performance fuel cell can be obtained. Furthermore, it is also possible to cover the protrusions of the electrode base material and catalyst layer, etc., which can reduce the micro short-circuit during the production of the membrane electrode composite and the micro short-circuit in use as a fuel cell, thereby reducing the performance of the membrane electrode composite. The effect which can be suppressed can also be expected. Furthermore, even when the polymer electrolyte membrane has pinholes, surface defects, etc., it can be protected and repaired by the interface resistance reducing layer, and the performance and durability of the membrane electrode assembly can be stabilized.

  This interface resistance reduction layer is not particularly limited as long as it has ion conductivity such as the polymer electrolyte material of the present invention and has resistance to the fuel used, but was obtained in the present invention from the viewpoint of mechanical strength and fuel resistance. It is particularly preferred to include a polymer electrolyte material. For example, when a membrane electrode is combined, a composition containing a polymer electrolyte material containing at least a protecting group and an ionic group, a solvent and a plasticizer according to the present invention is used as a precursor for an interface resistance reducing layer. By removing the solvent and plasticizer by drying, extraction washing and the like after the composite, a high-performance membrane electrode assembly having a reduction in interfacial resistance, mechanical strength, and fuel resistance can be obtained. At this time, the interface resistance reducing layer precursor may be formed on the electrode side or the polymer electrolyte membrane side before the composite step.

  Next, an example of an electrode suitable for the membrane electrode assembly of the present invention will be described. Such an electrode comprises a catalyst layer and an electrode substrate. The catalyst layer here is a layer containing a catalyst for promoting an electrode reaction, an electron conductor, an ion conductor, and the like. As the catalyst contained in the catalyst layer, for example, a noble metal catalyst such as platinum, palladium, ruthenium, rhodium, iridium, gold is preferably used. One of these may be used alone, or two or more of them, such as alloys and mixtures, may be used in combination.

  Moreover, when using an electronic conductor (conductive material) for a catalyst layer, a carbon material and an inorganic conductive material are preferably used from the point of electronic conductivity or chemical stability. Among these, amorphous and crystalline carbon materials are mentioned. For example, carbon black such as channel black, thermal black, furnace black, and acetylene black is preferably used because of its electron conductivity and specific surface area. As furnace black, Vulcan XC-72R (registered trademark), Vulcan P (registered trademark), Black Pearls 880 (registered trademark), Black Pearls 1100 (registered trademark), Black Pearls 1300 (registered trademark), Black Pearls manufactured by Cabot Corporation 2000 (Registered Trademark), Legal 400 (Registered Trademark), Ketjen Black International Ketjen Black EC (Registered Trademark), EC600JD, Mitsubishi Chemical Corporation # 3150, # 3250, and the like. Examples include Denka Black (registered trademark) manufactured by Chemical Industries. In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin can also be used. As the form of these carbon materials, in addition to irregular particles, fibers, scales, tubes, cones, and megaphones can also be used. Moreover, you may use what post-processed these carbon materials.

  Moreover, when using an electronic conductor, it is preferable from the point of electrode performance that it is disperse | distributing uniformly with a catalyst particle. For this reason, it is preferable that the catalyst particles and the electron conductor are well dispersed in advance as a coating liquid. Furthermore, it is also a preferred embodiment to use catalyst-supporting carbon or the like in which the catalyst and the electron conductor are integrated as the catalyst layer. By using this catalyst-supporting carbon, the utilization efficiency of the catalyst is improved, which can contribute to the improvement of battery performance and cost reduction. Here, even when catalyst-supported carbon is used for the catalyst layer, a conductive agent can be added to further increase the electron conductivity. As such a conductive agent, the above-described carbon black is preferably used.

  As the substance having ion conductivity (ion conductor) used in the catalyst layer, various organic and inorganic materials are generally known. However, when used in a fuel cell, sulfone which improves ion conductivity. A polymer having an ionic group such as an acid group, a carboxylic acid group, or a phosphoric acid group (ion conductive polymer) is preferably used. Among them, from the viewpoint of the stability of the ionic group, a polymer having ion conductivity composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain, or the polymer electrolyte material of the present invention and a known hydrocarbon-based polymer. A molecular electrolyte material is preferably used. As the perfluoro-based ion conductive polymer, for example, Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., and the like are preferably used. These ion conductive polymers are provided in the catalyst layer in a solution or dispersion state. At this time, the solvent for dissolving or dispersing the polymer is not particularly limited, but a polar solvent is preferable from the viewpoint of the solubility of the ion conductive polymer. Among them, the polymer electrolyte material obtained in the present invention can be most suitably used as a substance (ion conductor) having ion conductivity in the catalyst layer. In particular, in the case of a fuel cell using methanol aqueous solution or methanol as fuel, the polymer electrolyte material obtained by the present invention is effective in durability from the viewpoint of methanol resistance. The polymer electrolyte material of the present invention is processed at the stage of a soluble polymer electrolyte material for molding, and after being made into a MEA, it is deprotected and imparts solvent resistance, thereby achieving both workability and solvent resistance. Preferred binders can be made.

  Since the catalyst and the electronic conductors are usually powders, the ionic conductor usually plays a role of solidifying them. It is preferable from the viewpoint of electrode performance that the ionic conductor is added in advance to a coating liquid containing catalyst particles and an electronic conductor as main constituents when the catalyst layer is prepared, and is applied in a uniformly dispersed state. is there. The amount of the ionic conductor contained in the catalyst layer should be appropriately determined according to the required electrode characteristics and the conductivity of the ionic conductor used, and is not particularly limited, but the weight ratio The range of 1 to 80% is preferable, and the range of 5 to 50% is more preferable. When the ion conductor is too small, the ion conductivity is low, and when it is too much, the gas permeability may be hindered.

  Such a catalyst layer may contain various substances in addition to the catalyst, the electron conductor, and the ionic conductor. In particular, in order to improve the binding property of the substance contained in the catalyst layer, a polymer other than the above-described ion conductive polymer may be included. Examples of such a polymer include fluorine atoms such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), polytetrafluoroethylene, and polyperfluoroalkyl vinyl ether (PFA). These copolymers, copolymers of monomer units constituting these polymers and other monomers such as ethylene and styrene, or blend polymers can be used. The content of these polymers in the catalyst layer is preferably in the range of 5 to 40% by weight. When there is too much polymer content, there exists a tendency for an electronic and ionic resistance to increase and for electrode performance to fall.

  In addition, when the fuel is a liquid or gas, the catalyst layer preferably has a structure in which the liquid or gas easily permeates, and preferably has a structure that promotes the discharge of by-products due to the electrode reaction.

  Moreover, as an electrode base material, an electrical resistance is low and what can collect or supply electric power can be used. Further, when the catalyst layer is used also as a current collector, it is not necessary to use an electrode substrate. Examples of the constituent material of the electrode base material include carbonaceous and conductive inorganic substances. For example, a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, molybdenum And titanium. These forms are not particularly limited, and are used, for example, in the form of fibers or particles. From the viewpoint of fuel permeability, fibrous conductive materials (conductive fibers) such as carbon fibers are preferable. As an electrode base material using conductive fibers, either a woven fabric or a non-woven fabric structure can be used.

  For example, carbon paper TGP series, SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. Examples of the woven fabric include plain weave, oblique weaving, satin weaving, crest weaving, binding weaving, and the like. Moreover, as a nonwoven fabric, it does not specifically limit, such as a paper making method, a needle punch method, a spun bond method, a water jet punch method, and a melt blow method. It may also be a knitted fabric. In these fabrics, especially when carbon fibers are used, a plain fabric using flame-resistant spun yarn is carbonized or graphitized woven fabric, and the flame-resistant yarn is carbonized after being processed into a nonwoven fabric by the needle punch method or water jet punch method. Alternatively, a graphitized nonwoven fabric, a flameproof yarn, a carbonized yarn, or a mat nonwoven fabric by a paper making method using a graphitized yarn is preferably used. In particular, it is preferable to use a nonwoven fabric or cloth from the viewpoint of obtaining a thin and strong fabric.

  Examples of the carbon fiber used for the electrode substrate include polyacrylonitrile (PAN) carbon fiber, phenolic carbon fiber, pitch carbon fiber, and rayon carbon fiber.

  In addition, the electrode base material has a water repellent treatment for preventing gas diffusion / permeability deterioration due to water retention, a partial water repellent treatment for forming a water discharge path, a hydrophilic treatment, and a resistance reduction. For example, carbon powder can be added. Further, a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer can be provided between the electrode substrate and the catalyst layer. In particular, when the electrode base material is a carbon fiber woven fabric or a nonwoven fabric having a large porosity, by providing the conductive intermediate layer, it is possible to suppress performance degradation due to the catalyst layer soaking into the electrode base material.

  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 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, but 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 molded body obtained by the present invention is not particularly limited, but a power supply source of a mobile 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 A sample of a membrane serving as a specimen was immersed in pure water at 25 ° C. for 24 hours, vacuum-dried at 40 ° C. for 24 hours, and then measured by elemental analysis. Carbon, hydrogen, and nitrogen were analyzed by a fully automatic elemental analyzer varioEL, 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 the membrane sample in a 30% by weight aqueous methanol solution at 25 ° C. for 24 hours, the membrane sample is taken out in an atmosphere at 25 ° C. and a relative humidity of 50-80%, and proton conduction is performed as quickly as possible by the constant potential AC impedance method Degree A was measured.

  Further, the membrane sample was immersed in pure water at 25 ° C. for 24 hours, and then taken out in an atmosphere at 25 ° C. and a relative humidity of 50 to 80%, and the proton conductivity B was measured as quickly as possible by the constant potential AC impedance method.

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

(4) Hot water resistance and hot methanol resistance The hot water resistance and hot methanol resistance of the electrolyte membrane were evaluated by measuring the dimensional change rate in a 30 wt% methanol aqueous solution at 60 ° 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. After immersing the electrolyte membrane in a 30 wt% aqueous methanol solution at 60 ° C. for 12 hours, the length (L2) was measured again with a caliper, and the size change was visually observed.

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

(6) Methanol Permeation A film-like sample was immersed in 25 ° C. hot water pure water 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.

(7) Wide-angle X-ray diffraction The polymer electrolyte material used as a specimen was set in a diffractometer, and X-ray diffraction measurement was performed under the following conditions.

X-ray diffractometer: RINT2500V manufactured by Rigaku Corporation
X-ray: Cu-Kα
X-ray output: 50kV-300mA
Optical system: Concentrated optical system Scan speed: 2θ = 2 ° / min
Scanning method: 2θ-θ
Scan range: 2θ = 5-60 °
Slit: Divergence slit -1 / 2 °, Light receiving slit -0.15mm, Scattering slit -1 / 2 °
The degree of crystallinity is obtained by separating each component by profile fitting, obtaining the diffraction angle and integrated intensity of each component, and using the obtained crystalline peak and integrated intensity of amorphous halo, the general formula (S1) The crystallinity was calculated from the following formula.
Crystallinity (%) = (sum of integrated intensities of all crystalline peaks) / (sum of integrated intensities of all crystalline peaks and amorphous halo) × 100 (S1)
(8) Weight reduction with respect to N-methylpyrrolidone A polymer electrolyte membrane (about 0.1 g) as a specimen was sufficiently washed with pure water, and then vacuum-dried at 40 ° C. for 24 hours to measure the weight. The polymer electrolyte membrane was immersed in 1000 times the weight of N-methylpyrrolidone and heated in an airtight container at 100 ° C. for 2 hours with stirring. Next, filtration was performed using filter paper (No. 2) manufactured by Advantech. At the time of filtration, the filter paper and the residue were washed with 1000 times weight of the same solvent, the eluate was sufficiently eluted in the solvent, and the N-methylpyrrolidone contained in the residue was sufficiently washed with pure water. The residue was vacuum-dried at 40 ° C. for 24 hours and the weight was measured to calculate the weight loss.

(9) Performance evaluation of membrane electrode assembly Voltage holding ratio The membrane electrode assembly was incorporated into an electrochem single cell “EFC05-01SP” (cell for electrode area 5 cm ² ), the cell temperature was set to 50 ° C., and 20% methanol aqueous solution 0.2 ml / min on the anode side Measure the voltage-current characteristics using a Toyo Technica evaluation device, a potentiostat 1470 made by solartron, and a frequency response analyzer made by solartron 1255B. Then, a voltage having a current density of 250 mA / cm ² was read, and thereafter, operation was stopped for 100 hours at a constant current of 250 mA / cm ^{2 in} a pattern in which power generation was stopped every 5 hours for 1 hour. After the constant current evaluation, a voltage with a current density of 250 mA / cm ² was read from the current-voltage curve, and the retention rate from the first time was calculated.

B. Measurement of fuel (methanol) permeation amount (hereinafter sometimes referred to as “MCO”) Before applying an electric current, the synthetic air discharged from the cathode is collected in a gas collection bag, and GE Using a gas chromatograph “MicroGC CP4900” with an autosampler manufactured by Science, the concentrations of both methanol in the sampling gas and carbon dioxide produced by oxidation were measured and calculated. Here, it was assumed that all carbon dioxide was generated from permeated methanol. The cathode air flow rate is L (ml / min), the total concentration of methanol and carbon dioxide by gas chromatography is Z (% by volume), the total volume is V (ml), and the open area (the aqueous methanol fuel in the membrane electrode assembly is The area of direct contact) was A (cm ² ), and the following formula was used for calculation.
MCO (mol / cm ² / min) = (L + V) × (Z / 100) / 22400 / A
C. Power generation evaluation (methanol water fuel)
In a state where 30% by weight methanol water was stored in the anode, measurement was performed using an evaluation apparatus manufactured by Toyo Technica, a potentiostat 1470 manufactured by solartron, and a frequency response analyzer 1255B manufactured by solartron. The current sweep rate was 10 mV / min, and the voltage was measured up to 30 mV. A value obtained by dividing the point at which the product of the current and voltage in the current-voltage curve becomes the highest by the electrode area was taken as the output density.

D. Power generation evaluation (hydrogen fuel)
Fuel cell: cell temperature: 60 ° C., fuel gas: hydrogen, oxidizing gas: air, gas utilization: anode 70% / cathode 40%, humidification; anode-90% / cathode 90% current-voltage (IV) )It was measured. A value obtained by dividing the point at which the product of the current and voltage in the current-voltage curve becomes the highest by the electrode area was taken as the output density.

Synthesis example 1
A sulfonic acid derivative represented by the following general formula ( Q2) was synthesized.

  In a 100 ml three-necked flask equipped with a nitrogen inlet tube and a stirrer, 2.1 g of aluminum chloride and 6 ml of 1,2-dichloroethane were weighed and cooled in an ice bath. 2,6-Difluorobenzoic acid chloride was added thereto, and then a solution obtained by dissolving 2.55 g of diphenyl ether in 2.0 ml of 1,2-dichloroethane was added dropwise. After dropping, the reaction solution was poured into ice water, and the separated organic layer was concentrated to dryness. This was dissolved in 30 ml of acetone and the salt was filtered. The filtrate was concentrated to dryness to obtain 2,6-difluoro-4'-phenoxybenzophenone. The 2,6-difluoro-4'-phenoxybenzophenone obtained as described above was cooled in an ice bath in a 100 ml three-necked flask equipped with a nitrogen inlet tube and a stirrer. After adding 30 ml of concentrated sulfuric acid to this, 32 ml of 60% fuming sulfuric acid was added and stirred for 1 hour. The mixture was then warmed to 70 ° C. and stirred for 15 hours. The reaction solution was cooled, poured into 400 ml of ice water, and the pH was adjusted to 6-7 with an aqueous sodium hydroxide solution, followed by filtration. The filtrate was concentrated and extracted with 400 ml dimethyl sulfoxide. The insoluble material was filtered off, and the filtrate was concentrated. The residue was dissolved in 60 ml of water and heated to 60 ° C. To this, water was added until no more precipitate was formed, and the product was filtered to obtain a trisulfonated product.

Synthesis example 2
A sulfonic acid derivative represented by the following general formula (Q3) was synthesized.

  To 2,6-difluoro-4'-phenoxybenzophenone obtained in Synthesis Example 1, 30 ml of concentrated sulfuric acid was added, and then 40 ml of 60% fuming sulfuric acid was added to sulfonate and obtain a tetrasulfonated product.

Synthesis example 3
2,2-bis (4-hydroxyphenyl) -1,3-dioxolane represented by the general formula (D1) was synthesized.

  In a 500 ml flask equipped with a stirrer, thermometer and distillation tube, 49.5 g of 4,4'-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate and 0.50 g of p-toluenesulfonic acid monohydrate were added. Charge and dissolve. 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
A polymer represented by the following general formula (G2) was synthesized.

  6.91 g (50 mmol) of potassium carbonate, 10.23 g (39.6 mmol) of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane, 6.98 g (32 mmol) of 4,4′-difluorobenzophenone, and Polymerization was performed at 230 ° C. in N-methylpyrrolidone (NMP) using the trisulfonated product Q2 (8 mmol) obtained in Synthesis Example 1. Purification was performed by re-precipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (G2). The weight average molecular weight was 143,000.

  A 25 wt% N-methylpyrrolidone (NMP) solution in which the obtained polymer electrolyte material containing an aromatic ring having a ketal having the general formula (G2) was dissolved was casted on a glass substrate at 100 ° C. After drying for 4 hours, heat treatment was performed at 300 ° C. for 10 minutes under nitrogen to obtain a film. The solubility of the polymer electrolyte material before molding 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 amount of pure water for 24 hours and washed thoroughly. The resulting membrane had a sulfonic acid group density of 2.34 mmol / g.

The obtained membrane had a thickness of 41 μm and a proton conductivity A per area of 19.8 S / cm ² . Further, almost no dimensional change was observed in a 60 ° C., 30 wt% methanol aqueous solution, the conductivity was high, and the heat resistant methanol resistance was excellent. Even when immersed in NMP at 100 ° C., it did not dissolve. The evaluation results are summarized in Table 1. The obtained polymer electrolyte membrane was a very tough electrolyte membrane although no crystalline peak was observed by wide-angle X-ray diffraction. Excellent solvent resistance. Furthermore, while maintaining conductivity, it was excellent in fuel cutoff.

Example 2
A polymer represented by the following general formula (G3) was synthesized.

  6.91 g (50 mmol) of potassium carbonate, 10.23 g (39.6 mmol) of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane, 6.98 g (32 mmol) of 4,4′-difluorobenzophenone, and Polymerization was performed at 230 ° C. in N-methylpyrrolidone (NMP) using the tetrasulfonated product Q3 (8 mmol) obtained in Synthesis Example 2. Purification was performed by re-precipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (G3). The weight average molecular weight was 143,000.

  A 25 wt% N-methylpyrrolidone (NMP) solution in which the obtained polymer electrolyte material containing an aromatic ring having a ketal having the general formula (G3) was dissolved was casted on a glass substrate at 100 ° C. After drying for 4 hours, heat treatment was performed at 300 ° C. for 10 minutes under nitrogen to obtain a film. The solubility of the polymer electrolyte material before molding 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 amount of pure water for 24 hours and washed thoroughly. The resulting membrane had a sulfonic acid group density of 2.92 mmol / g.

The obtained membrane had a thickness of 41 μm and a proton conductivity A per area of 24.4 S / cm ² . Further, almost no dimensional change was observed in a 60 ° C., 30 wt% methanol aqueous solution, the conductivity was high, and the heat resistant methanol resistance was excellent. Even when immersed in NMP at 100 ° C., it did not dissolve. The evaluation results are summarized in Table 1. The obtained polymer electrolyte membrane was a very tough electrolyte membrane although no crystalline peak was observed by wide-angle X-ray diffraction. Excellent solvent resistance. Furthermore, while maintaining conductivity, it was excellent in fuel cutoff.

Example 3
A polymer represented by the following general formula (G6) was synthesized.

  6.91 g (50 mmol) of potassium carbonate, 4,4′-dihydroxytetraphenylmethane (39.6 mmol), 6.11 g (28 mmol) of 4,4′-difluorobenzophenone, and trisulfonated product Q2 obtained in Synthesis Example 1 (12 mmol) was used for polymerization at 230 ° C. in N-methylpyrrolidone (NMP). Purification was performed by re-precipitation with a large amount of water to obtain a polymer electrolyte material represented by the above general formula (G6). The weight average molecular weight was 153,000.

  The obtained 25 wt% N-methylpyrrolidone (NMP) solution in which the polymer electrolyte material of the general formula (G6) was dissolved was cast on a glass substrate, dried at 100 ° C. for 4 hours, and then at 300 ° C. under nitrogen. For 10 minutes to obtain a film. The solubility of the polymer electrolyte material before molding was very good. After proton substitution by immersing in 6N hydrochloric acid at 95 ° C. for 24 hours, it was immersed in a large excess of pure water for 24 hours and thoroughly washed. The resulting membrane had a sulfonic acid group density of 2.82 mmol / g.

The obtained membrane had a thickness of 41 μm and a proton conductivity A per area of 23.9 S / cm ² . Further, almost no dimensional change was observed in a 60 ° C., 30 wt% methanol aqueous solution, the conductivity was high, and the heat resistant methanol resistance was excellent. Even when immersed in NMP at 100 ° C., it did not dissolve. The evaluation results are summarized in Table 1. It was an extremely tough electrolyte membrane and excellent in solvent resistance. Furthermore, while maintaining conductivity, it was excellent in fuel cutoff .

Comparative Example 1
A commercially available Nafion (registered trademark) 117 membrane (manufactured by DuPont) was used to evaluate ion conductivity, MCO and heat-resistant 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 film thickness was 209 μm, and the proton conductivity A per area was 5.0 S / cm ² . In addition, a 20% dimensional change (swelling) was observed in a 30 wt% methanol aqueous solution at 60 ° C. The conductivity was high, but the heat-resistant methanol resistance was insufficient.

  The evaluation results are summarized in Table 1. The conductivity was high, but the fuel cutoff was inferior.

Comparative Example 2
Various characteristics were evaluated using a commercially available Nafion (R) 111 membrane (manufactured by DuPont). The Nafion (R) 111 membrane was immersed in 5% hydrogen peroxide water at 100 ° C. for 30 minutes, and then immersed 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. The conductivity was high, but the fuel cutoff was inferior.

Comparative Example 3
Sulfonation of PEEK 10 g of polyetheretherketone (Victrex (registered trademark) PEEK (registered trademark) (manufactured by Victrex)) was reacted in 100 mL of concentrated sulfuric acid at 25 ° C. for 20 hours. By gradually throwing it into a large amount of water, a sulfonated product of polyetheretherketone was obtained. The resulting polymer had a sulfonic acid group density of 2.1 mmol / g. Since the polymer is sulfonated while being dissolved, it is difficult to obtain the position and amount of the sulfonic acid group with good reproducibility.

  A 25 wt% N-methylpyrrolidone (NMP) solution in which the resulting sulfonated product was dissolved was subjected to pressure filtration using a glass fiber filter, and then cast on a glass substrate, dried at 100 ° C. for 4 hours, Got. The solubility of the polymer was good. The polymer electrolyte membrane was obtained by immersing in a large excess of pure water for 24 hours and thoroughly washing.

  The evaluation results are summarized in Table 1. In the obtained polymer electrolyte membrane, no crystalline peak was observed by wide-angle X-ray diffraction. Furthermore, the conductivity was relatively high, but the fuel shut-off property was inferior. Moreover, it collapsed in 60 degreeC and 30 wt% methanol aqueous solution, or 95 degreeC hot water. It was inferior in solvent resistance.

Comparative Example 4
PEK was sulfonated.

  10 g of polyetherketone resin (manufactured by Victrex) was reacted in 100 mL of fuming sulfuric acid at 100 ° C. for 2 hours. After diluting with concentrated sulfuric acid, it was gradually poured into a large amount of water to obtain a polyether ketone sulfonated product SPEK-2. The sulfonic acid group density of the obtained SPEK-2 was 1.2 mmol / g.

The SPEK-2 polymer could not be dissolved in N-methylpyrrolidone (NMP), and film formation was difficult. The composition was similar to the polymer of Example 1, but poor in solubility. Further, the presence of a ketal group could not be confirmed from IR and solid ¹³ C-CP / MAS spectrum. Various evaluations could not be performed.

  The powdered polyetherketone resin showed a crystalline peak by wide-angle X-ray diffraction, and the crystallinity was 30%.

Comparative Example 5
The polyether ketone polymer was polymerized by the method described in Example 2 except that the hydroquinone was changed to 4.40 g (40 mmol). From the initial stage of polymerization, a polymer was precipitated, and the polymerization was difficult. Molecular weight could not be measured due to solvent insolubility. Since the solubility was insufficient, the film could not be formed and various measurements could not be performed.

  Table 1 shows the evaluation results of Examples 1 to 7 and Comparative Examples 1 to 3. The electrolyte membranes of Examples 1 to 7 were excellent in proton conductivity, excellent in fuel cutoff properties and solvent resistance. The electrolyte membrane of the comparative example was inferior in fuel barrier property or solvent resistance.

Electrode production example 1
(1) Electrode for Membrane Electrode Assembly Using Methanol Aqueous Solution as Fuel On a carbon cloth “TL-1400W” manufactured by E-TEK made of carbon fiber fabric, Pt− manufactured by Johson & Matthey From Ru-supported carbon catalyst “HiSPEC” (registered trademark) 10000 and “HiSPEC” (registered trademark) 6000, the soluble polymer electrolyte material for molding of the formula (G1) obtained in Example 1 and N-methyl-2-pyrrolidone An anode catalyst coating solution was applied and dried to prepare an electrode A. The anode catalyst coating solution was applied to the surface coated with the carbon black dispersion. Similarly, on the above electrode base material, Tanaka Kikinzoku Kogyo Co., Ltd. Pt-supported carbon catalyst TEC10V50E, DuPont 20% "Nafion" (registered trademark) solution and n-propanol The cathode catalyst coating solution was applied and dried to prepare an electrode B.

The catalyst adhesion amount was adjusted so that the electrode A was 2.5 mg / cm ² in terms of platinum weight, and the electrode B was 4.5 mg / cm ^{2 in} terms of platinum weight.

(2) Electrode for membrane electrode assembly using hydrogen as fuel
Aldrich “Nafion” (registered trademark) solution is loaded with catalyst-supported carbon (catalyst: Pt, carbon: Cabot ValcanXC-72, platinum loading: 50% by weight) with platinum and “Nafion” (registered trademark) weight The catalyst-polymer composition was prepared by adding to a ratio of 1: 0.5 and stirring well. This catalyst-polymer composition was applied to an electrode base material (carbon paper TGP-H-060 manufactured by Toray Industries, Inc.) that had been subjected to a water-repellent treatment (impregnated with 20% by weight of PTFE and calcined) and immediately dried. Thus, an electrode C was produced. The electrode adhesion amount of the electrode C was adjusted so as to be 1.0 mg / cm ^{2 in} terms of platinum weight.

Preparation Example of Interfacial Resistance Reduction Layer Precursor 10 g of the soluble polymer electrolyte material for molding of formula (G2) obtained in Example 2, 55 g of N-methyl-2-pyrrolidone, and 45 g of glycerin are placed in a container and heated to 100 ° C. Then, the mixture was stirred until it became uniform to obtain an interface resistance reducing layer precursor B.

Example 8
Using two electrodes C, the electrolyte membrane obtained in Example 2 was sandwiched so as to face each other, and heated and pressed at 130 ° C. for 10 minutes at a pressure of 5 MPa to obtain a membrane electrode assembly. This was incorporated into a power generation cell to obtain a fuel cell.

When the power generation characteristics of this fuel cell using hydrogen as a fuel were evaluated, the maximum output was 700 mW / cm ² .

Example 9
The film before deprotection obtained in Example 2 was sandwiched so that the electrode A and the electrode B were opposed to each other, and joined by performing a heat press at 200 ° C. for 1 minute at a pressure of 3 MPa. Next, the joined body was immersed in 100 g of 6N hydrochloric acid, heated to 80 ° C., and treated for 24 hours to obtain a membrane electrode composite. After that, it was washed with pure water until the washing solution became neutral, and incorporated into a power generation cell to obtain a fuel cell.

  The voltage holding ratio was 96% (the initial voltage was 0.25 V, and the voltage after 100 hours constant current power generation was 0.24 V), indicating excellent durability.

Further, the methanol permeation amount of this membrane electrode assembly was 4.5 μmol / cm ² / min. Moreover, the output in passive evaluation showed 70 mW / cm < ² >.

Comparative Example 6
A commercially available Nafion (registered trademark) solution (aldrich reagent) was applied to electrodes A and B and dried at 100 ° C. to obtain an electrode with a Nafion (registered trademark) coating. Using “Nafion 117 (registered trademark)” manufactured by DuPont as an electrolyte membrane, the above-mentioned electrodes were laminated so as to sandwich the electrolyte membrane without using the interface resistance reducing composition, and the pressure was 5 MPa at 130 ° C. for 30 minutes. Heat pressing was performed under pressure to obtain a membrane electrode assembly.

The membrane electrode composite has a large methanol permeation amount of 13.0 μmol / cm ² / min and a voltage holding ratio of 48% (the initial voltage is 0.21 V and the voltage after 100 hours of constant current power generation is 0.1 V). And the durability was inferior. Moreover, the output in passive evaluation was 10 mW / cm < ² > and was a low output. When the evaluation cell after these evaluations was disassembled, the membrane electrode assembly was taken out and visually observed, peeling due to swelling of the methanol aqueous solution occurred at the interface between the anode electrode and the electrolyte membrane, and part of the catalyst collapsed and flowed out. Was. The electrolyte material used had insufficient heat-resistant methanol resistance.

Example 10
The interface resistance reducing layer precursor B was applied on the electrodes A and B so as to be 3 mg / cm ^2, and heat-treated at 100 ° C. for 1 minute. These electrodes were cut so that the electrode projection area was 5 cm ² .

  Next, these electrodes with the interface resistance reduction layer precursor B are laminated so that the interface resistance reduction layer precursor B is on the film side before the deprotection treatment obtained in Example 2, and at 100 ° C. for 1 minute. Heat pressing was performed at a pressure of 3 MPa, and the pressed joined body was immersed in a solution obtained by adding 10 g of methanol to 90 g of 6N hydrochloric acid, heated to 80 ° C., and treated for 30 hours while refluxing to obtain a membrane electrode assembly. (Residual solvent extraction and proton exchange). After that, it was washed with pure water until the washing solution became neutral, and incorporated into a power generation cell to obtain a fuel cell.

  The voltage holding ratio was 96% (the initial voltage was 0.25 V, and the voltage after 100 hours constant current power generation was 0.24 V), indicating excellent durability.

Further, the methanol permeation amount of this membrane electrode assembly was 4.5 μmol / cm ² / min. Moreover, the output in passive evaluation showed 50 mW / cm < ² >.

Example 11
The membrane composite electrode body of Example 10 was prepared so as to have an electrode area of 32 cm ^2, and a stack cell as shown in FIG. 1 was used to manufacture a fuel cell with 6 membrane electrode assemblies. When power was generated while circulating a 10% aqueous methanol solution on the anode side with a pump, an output of 7 W was obtained.

It is the figure which showed an example of the stacked fuel cell.

Explanation of symbols

1: Membrane electrode composite 2: Gasket 3: Bipolar separator 4: Current collector plate 5: Fuel supply port 6: Clamping screw 7: Air flow path 8: Fuel flow path 9: Fuel tank

Claims (4)

An aromatic polyether polymer electrolyte membrane comprising a structural unit represented by the following general formula (2) or (3) and a structural unit represented by the following general formula (K1) .

(In general formulas (2) and (3), R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms.)

(The structural unit represented by the general formula (K1) may be optionally substituted, but does not contain an ionic group.) An aromatic composed of a structural unit represented by the following general formula (2) or (3), a structural unit represented by the following general formula (K1), and a structural unit represented by the following general formula (X-21) Polyether polymer electrolyte membrane.

(In general formulas (2) and (3), R represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or a hydrocarbon group having 1 to 20 carbon atoms.)

(The structural unit represented by the general formula (K1) may be optionally substituted, but does not contain an ionic group.)

(The structural unit represented by the general formula (X-21) may have a substituent and an ionic group.) The polymer electrolyte membrane according to claim 1 or 2, wherein the sulfonic acid group density is 0.5 to 3.0 mmol / g. A polymer electrolyte fuel cell comprising the polymer electrolyte membrane according to claim 1.

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