JPWO2010047329A1 - Organic-inorganic composite electrolyte, electrolyte membrane, membrane-electrode assembly, and fuel cell - Google Patents

Abstract

The present invention relates to an organic-inorganic composite electrolyte and the like suitable for producing an electrolyte membrane used for a polymer electrolyte fuel cell. In recent years, polymer electrolyte fuel cells have attracted attention as a fundamental solution to energy and environmental problems. In order for the fuel cells to be put into practical use and spread, electrolytes having high ion conductivity even under low humidity conditions. A membrane is required. In general, an increase in the amount of ion-conductive groups is considered effective for improving ion conductivity under low-humidity conditions, but mechanical durability decreases as the number of ion-conductive groups increases. There was a problem. The present invention is a block copolymer comprising, as constituent components, polymer blocks (A) and (B) that are phase-separated from each other in the electrolyte, and the polymer block (A) has an ion conductive group, A composition comprising a block copolymer in which a polymer block (B) forms a flexible phase, an ion conductive group is substantially present only in the polymer block (A), and a metal phosphate having ion conductivity The above-mentioned problems are solved by using an electrolyte made of, for example.

Description

  The present invention is an electrolyte suitable for producing an electrolyte membrane for use in a polymer electrolyte fuel cell, which can realize low resistance (= low electric resistance) and high output in a low humidity state, and methanol. Electrolyte suitable for producing an electrolyte membrane excellent in methanol barrier property, capable of realizing high output in a direct methanol fuel cell (DMFC) as a fuel, capable of realizing high output, and excellent in flexibility and moldability The present invention relates to an electrolyte membrane composed of the electrolyte, a membrane-electrode assembly using the electrolyte membrane, and a solid polymer fuel cell.

  In another aspect / mode, the present invention is an electrolyte suitable for producing an electrolyte membrane for use in a polymer electrolyte fuel cell, and realizes low resistance and high output even under high temperature and low humidity conditions. Electrolyte suitable for producing an electrolyte membrane excellent in flexibility and moldability, electrolyte membrane comprising the electrolyte, membrane-electrode assembly and solid polymer fuel cell using the electrolyte membrane About.

  In recent years, fuel cell technology has attracted attention as a fundamental solution to energy and / or environmental problems and as a central energy conversion system in the future hydrogen energy era. In particular, polymer electrolyte fuel cells (PEFC) using hydrogen as the fuel are used as power sources for electric vehicles and portable devices because they can be reduced in size and weight. Furthermore, application to power supply equipment for home use that simultaneously uses electricity and heat is being studied.

  A polymer electrolyte fuel cell is generally configured as follows. First, catalyst layers containing carbon powder carrying a white metal catalyst and an ion conductive binder made of a polymer electrolyte are formed on both sides of the polymer electrolyte membrane having ion conductivity. A gas diffusion layer, which is a porous material through which fuel gas and oxidant gas are passed, is formed outside each catalyst layer. Carbon paper, carbon cloth, or the like is used as the gas diffusion layer. A structure in which the catalyst layer and the gas diffusion layer are integrated is called a gas diffusion electrode, and a structure in which a pair of gas diffusion electrodes is bonded to the electrolyte membrane so that the catalyst layer faces the electrolyte membrane is a membrane-electrode assembly ( MEA (Mebrane Electrode Assembly). On both sides of this membrane-electrode assembly, separators having electrical conductivity and airtightness are disposed. A gas flow path for supplying a fuel gas or an oxidant gas (for example, air) to the electrode surface is formed in a contact portion of the membrane-electrode assembly and the separator or in the separator. Electric power is generated by supplying a fuel gas such as hydrogen or methanol to one electrode (fuel electrode, anode) and an oxidant gas containing oxygen such as air to the other electrode (oxygen electrode, cathode). That is, at the fuel electrode, the fuel is ionized to produce protons and electrons, the protons pass through the electrolyte membrane, the electrons travel through an external electric circuit formed by connecting both electrodes, and are sent to the oxygen electrode, Water is produced by the reaction. In this way, the chemical energy of the fuel can be directly converted into electric energy and taken out.

  In order for a polymer electrolyte fuel cell to be put into practical use and spread, an electrolyte membrane capable of exhibiting high ion conductivity even under low humidity conditions is required. Polymer electrolyte membranes used in polymer electrolyte fuel cells can exhibit high ionic conductivity by containing water, and ion conduction under low humidity and non-humidified conditions where the water content of the polymer electrolyte membrane is reduced However, there is a problem that the cell resistance during power generation (= cell electrical resistance) increases. For this reason, in order to maintain a high output, it is necessary to humidify the fuel battery cell, and the increase in the size of the apparatus and the complexity of the system are problems. In addition, it is known that the catalytic activity of the catalyst responsible for the electrochemical reaction at the anode and the cathode increases as the temperature rises. However, in order to maintain the water content of the polymer electrolyte membrane, operation above the boiling point of water is not recommended. An electrolyte membrane capable of expressing high ionic conductivity even in a low-humidity state is desired for a fuel cell that is difficult, high performance, and inexpensive. In general, it is known that increasing the amount of ion-conducting groups in the polymer electrolyte membrane is effective for improving the ionic conductivity in a low-humidity state. Since the film strength in a water-containing state is reduced and the dimensional change between drying and wetting is increased, there is a problem that mechanical durability is lowered.

  In addition, in DMFC using methanol as a fuel, an electrolyte membrane that can reduce methanol crossover (MCO) in which methanol permeates the electrolyte membrane during operation and power generation performance and fuel utilization efficiency are reduced is required. Yes. However, in the conventional polymer electrolyte membrane, it is indispensable to efficiently conduct proton conduction, that is, because the polymer electrolyte membrane has low cell resistance, and methanol is indispensable during DMFC power generation. It penetrates the water part contained in the water. In order to suppress MCO and realize low resistance, an electrolyte membrane that can exhibit high ionic conductivity even in a state where the amount of water contained as a methanol permeation path is small, that is, in a low humidity state, is desired.

  In another aspect, in order for solid polymer fuel cells to be put into practical use and spread, a technique for improving fuel cell power generation performance even under high temperature and low humidity conditions is required. Polymer electrolyte membranes used in polymer electrolyte fuel cells can exhibit high ionic conductivity by hydrating them, and in low humidity or non-humidified conditions where the moisture content of the polymer electrolyte membrane is reduced, There is a problem that conductivity is reduced and cell resistance during power generation is increased. For this reason, in order to maintain a high output, it is necessary to humidify the fuel battery cell, and there is a problem of increasing the size of the apparatus and complication of the system. In addition, the catalytic activity of the catalyst responsible for the electrochemical reaction at the anode and the cathode is known to increase as the temperature rises. However, in order to maintain the water-containing state of the polymer electrolyte membrane, operation at a temperature higher than the boiling point of water is required. Therefore, an electrolyte membrane capable of exhibiting high ionic conductivity even in a low humidity state is desired for a high-performance and inexpensive fuel cell. Therefore, there is a demand for an electrolyte membrane that exhibits high ionic conductivity even under high temperature and non-humidified conditions, and thus can achieve reduction in cell resistance and improvement in output of a fuel cell.

  In general, as a polymer electrolyte membrane for a solid polymer fuel cell, Nafion (registered trademark of DuPont), which is a perfluorocarbon sulfonic acid polymer, is used because it is chemically stable. It is used. However, since Nafion is a fluorine-based polymer, environmental considerations are necessary during synthesis and disposal, and it is expensive. Therefore, development of a novel electrolyte membrane is desired.

  In order to solve the above-mentioned problems, many polymer electrolyte membranes based on non-fluorine polymers have been proposed instead of perfluorocarbon sulfonic acid polymer electrolyte membranes. For example, sulfonated polyether ether ketone (PEEK) which is a heat-resistant aromatic polymer (Patent Document 1), sulfonated aromatic polymer sulfonated polyether sulfone (PES) (Non-Patent Document 1), etc. Can be mentioned. In general, sulfonated aromatic polymers are known to have high heat resistance, but due to their rigidity, there is a problem of poor moldability and mechanical durability. In addition, since sulfonated aromatic polymers require water for high-efficiency ion conduction, there is a problem that ion conductivity under low humidity conditions is insufficient.

  On the other hand, since a solid oxide fuel cell (SOFC) using a solid oxide such as zirconia as a solid electrolyte is operated at a high temperature of about 900 to 1000 ° C., it is not necessary to use platinum as a catalyst. In addition, catalyst poisoning is eliminated and high output can be expected. However, since a high temperature is required for the operation, the enlargement of the apparatus becomes a problem, and it is difficult to use the portable power source or a small stationary power source. In order to solve the above problems, metal phosphates having ion conductivity have been studied. (Patent Literature 2 and Non-Patent Literature 2). In addition to virtually no water required for ionic conduction, metal phosphates exhibit solid ionic conductivity at a temperature below the operating temperature of zirconia while being a solid oxide. However, the use of metal phosphate alone has problems in mechanical durability and formability due to the rigidity and brittleness inherent in inorganic materials, so polytetrafluoroethylene (PTFE) Development of a composite film using a fluororesin represented by the above as a binder has been studied. However, in the composite film with the fluororesin described above, the metal phosphate is coated with a fluororesin that does not have ionic conductivity, so in order to express high ionic conductivity, the mass ratio of the metal phosphate Therefore, it is difficult to produce an electrolyte membrane having both ionic conductivity and membrane strength because the strength of the membrane is reduced as the mass ratio of the fluororesin as a binder is reduced.

  In addition, an electrolyte containing a sulfonated aromatic polymer and an inorganic solid material such as a metal phosphate has been proposed (Patent Document 3). Similarly, if a binder is not used, mechanical durability and formability are poor. Since it is sufficient, it is difficult to increase the ionic conductivity.

JP-A-6-93114 JP 2008-53224 A JP 2008-218408 A

J. et al. Membrane Science 197 (2002) 231 J. et al. Electrochemical Society 154 (2007) B1265-B1269

A first object of the present invention is to provide an electrolyte that exhibits low resistance (electric resistance) under low humidity conditions, reduces MCO during DMFC power generation, improves output, and has excellent flexibility and moldability. And a membrane-electrode assembly and a polymer electrolyte fuel cell using the electrolyte membrane.
The second object of the present invention is to exhibit high proton conductivity even under conditions of high temperature, low humidity or no humidification, excellent membrane strength, flexibility and mechanical durability, and high formability (assembly property). It is an object of the present invention to provide an electrolyte having a bonding property with an electrode, a clamping property, etc., an electrolyte membrane made of the electrolyte, a membrane-electrode assembly using the electrolyte membrane, and a polymer electrolyte fuel cell.
The third object of the present invention is to have low resistance under low humidity conditions and to improve output by reducing methanol crossover (MCO) during direct methanol fuel cell (DMFC) power generation. Electrolyte that is excellent in electrolyte, can reduce elution of phosphoric acid from the electrolyte, and can improve durability while maintaining power generation performance, electrolyte membrane comprising the electrolyte, and membrane-electrode using the electrolyte membrane An object of the present invention is to provide a joined body and a polymer electrolyte fuel cell.

The inventors of the present invention provide a polymer block that is phase-separated from each other, and a block copolymer that includes a polymer block having an ion conductivity function and a flexibility function, respectively, and a metal phosphate having an ion conductivity The inventors have found that an electrolyte composed of a salt-containing composition satisfies the first object, and completed the present invention.
The present inventors also provide polymer blocks that are phase-separated from each other, a block copolymer that includes a polymer block having an ion conductive function and a flexible function, respectively, and a metal having an ion conductive property. An electrolyte comprising a phosphate-containing composition, the electrolyte having a mass ratio of block copolymer / metal phosphate in a specific range has been found to satisfy the second object, and the present invention has been completed did.
The inventors of the present invention include polymer blocks that are phase-separated from each other, each having a polymer block having an ion conductive function and a flexible function, and a metal phosphate having ion conductivity. An electrolyte comprising a composition, the electrolyte having a median diameter measured by static light scattering of the metal phosphate of 10 nm to 1 μm, and thus the electrolyte membrane, finds that the third object is satisfied. completed.

The present invention is broadly divided into three modes that can achieve the first, second, and third objects, respectively.
The first aspect of the present invention capable of achieving the first object is a block copolymer comprising polymer blocks (A) and (B) that are phase-separated from each other, wherein the polymer block (A) is: A block copolymer having an ion conductive group, the polymer block (B) forming a flexible phase, the ion conductive group being substantially present only in the polymer block (A), and a metal having ion conductivity The present invention relates to an electrolyte comprising a composition containing a phosphate.
In aspect 1, it is preferable that the mass ratio of the block copolymer / the metal phosphate is 99/1 to 30/70.
The second aspect of the present invention capable of achieving the second object is a block copolymer comprising polymer blocks (A) and (B) that are phase-separated from each other, wherein the polymer block (A) comprises: A block copolymer having an ion conductive group, the polymer block (B) forming a flexible phase, the ion conductive group being substantially present only in the polymer block (A), and a metal having ion conductivity A composition containing a phosphate, wherein the mass ratio of the block copolymer / the metal phosphate is 80/20 to 1/99.
The third aspect of the present invention capable of achieving the third object is a block copolymer comprising polymer blocks (A) and (B) that are phase-separated from each other, wherein the polymer block (A) is: The polymer block (B) has an ion conductive group, forms a flexible phase, and the ion conductive group has a block copolymer that is substantially present only in the polymer block (A), and has an ion conductivity. The present invention also relates to an electrolyte comprising a composition containing a metal phosphate having an average particle diameter of 10 nm to 1 μm.
In aspect 3, the mass ratio of the block copolymer / the metal phosphate is preferably 99/1 to 30/70.

  Regardless of which aspect of the invention is described above, in the block copolymer, the polymer block (A) is assumed to have a polar group and undergoes phase separation with the polymer block (B), and the polymer block (A ) And polymer blocks (B) are aggregated. In the present invention, “phase separation” means phase separation in a microscopic sense, and more specifically, called microphase separation in which the formed domain size is not more than the wavelength of visible light (3800 to 7800 mm). Is.

  Regardless of which aspect of the invention is described above, since the polymer block (A) has an ion conductive group, an ion channel is formed by the assembly of the polymer blocks (A) and becomes a path for ions. Since the polymer block (B) functions as a flexible phase, the moldability (assembling property, bonding property, clamping property, etc.) and the like are improved in the production of the membrane-electrode assembly and the polymer electrolyte fuel cell. Ion conductive groups include sulfonic acid groups, phosphonic acid groups, and salts thereof.

In the electrolyte membrane obtained from the electrolyte obtained by combining the above polymer electrolyte and the metal phosphate having ion conductivity under the non-humidified condition with respect to the first and third aspects of the present invention, the electrolyte In low humidity conditions where the membrane is in a low water content state, the metal phosphate with ion conductivity compensates for ionic conductivity, so low membrane resistance (= low membrane electrical resistance) in low humidity conditions and low cell resistance during power generation (= Low cell electrical resistance) can be realized. At this time, since the polymer block having an ion conductive function in the polymer electrolyte supplements the ion conduction network of the metal phosphate, sufficient ions can be obtained even in a state where the metal phosphates are not in contact with each other. Conductivity can be developed. In addition, since the metal phosphate does not require water for ionic conduction, water contained in the electrolyte membrane as a path for methanol to permeate can be reduced, and both low resistance and low MCO can be achieved. At this time, in the electrolyte membrane, an ion conduction mechanism that does not involve water is manifested, and the electroosmosis phenomenon of the contained water coordinated to the ions is suppressed. It is possible to alleviate the flooding phenomenon. Therefore, by using the electrolyte membrane made of the electrolyte of the present invention, the power generation performance can be improved from the viewpoint of moisture management. Furthermore, since the polymer block forming the flexible phase imparts flexibility to the electrolyte membrane, the moldability of the electrolyte membrane, the mechanical durability, and the bondability with the electrode, which are problematic only with metal phosphates, are improved. Can do.
In the electrolyte of aspect 3 of the present invention, in addition to the above, by controlling the particle size of the metal phosphate, the contact area between the metal phosphate and the block copolymer is increased, and the weight of the block copolymer is increased. The ion conductive group of the combined block (A) and the phosphate group of the metal phosphate form a hydrogen bond, thereby improving the density of the electrolyte membrane. The hydrogen bond formed between the ion conductive group of the block copolymer and the phosphate group of the metal phosphate improves the water resistance of the metal phosphate, thereby reducing the phosphate elution amount and protons. The density of the ion conductive group in the ion channel that becomes the path increases, the proton conduction efficiency in the electrolyte membrane improves, and the MCO during DMFC power generation is further suppressed, so that the DMFC power generation output can be improved.

  In the electrolyte of aspect 2 of the present invention, the above-described polymer electrolyte and a metal phosphate having ionic conductivity under non-humidified conditions are combined to form a high moisture-free condition under which the electrolyte membrane is in a low water content state. Below, since the metal phosphate with ionic conductivity compensates for ionic conductivity, low film resistance under high temperature and low humidity conditions (= low film electrical resistance) and low cell resistance during power generation (low cell electrical resistance) Can be realized. At this time, a polymer block having the ion conductivity function of the polymer electrolyte supplements the metal phosphate network, so that sufficient ionic conductivity is exhibited even when the metal phosphates are not in contact with each other. Is possible. In addition, in the electrolyte membrane, an ion conduction mechanism that does not involve water partially develops, and the electroosmosis phenomenon of contained water coordinated to protons is suppressed. It is possible to alleviate the flooding phenomenon that causes diffusion inhibition. Therefore, by using the electrolyte membrane obtained from the electrolyte of the present invention, the fuel cell power generation performance can be improved also from the viewpoint of moisture management. Furthermore, since the polymer block having the flexibility function imparts flexibility to the electrolyte membrane, the moldability of the electrolyte membrane, the mechanical durability, and the bondability with the electrode, which are problematic only with the metal phosphate, are improved. Can do.

The electrolyte membrane obtained by using the electrolyte of Embodiments 1 and 3 of the present invention has excellent ionic conductivity under low humidity conditions, improves the power generation output of a fuel cell using hydrogen that operates under low humidity conditions, and DMFC The MCO can be reduced and the power generation output can be improved. The electrolyte membrane is excellent in flexibility, moldability and processability, and has high mechanical durability. Therefore, the membrane-electrode assembly using the electrolyte membrane has excellent performance in a polymer electrolyte fuel cell operating under low humidity conditions using hydrogen as a fuel, and a polymer electrolyte fuel cell using an aqueous methanol solution as a fuel. Can be demonstrated. In addition, the electrolyte is used as a binder used to take charge of ion conduction inside the electrode and binding of the catalyst in the fuel cell electrode catalyst layer from the viewpoint of low resistance under low humidity conditions, suppression of MCO, and moisture management of the fuel cell. It is also possible to use it.
In aspect 3 of the present invention, in addition to the above, by controlling the particle size of the metal phosphate, elution of phosphoric acid from the metal phosphate can be reduced, so that the durability of the electrolyte membrane is improved. At the same time, it is possible to increase the efficiency of proton conduction, reduce the MCO during DMFC power generation, and increase the output.
The electrolyte membrane obtained by using the electrolyte of aspect 2 of the present invention has excellent ionic conductivity under low humidity conditions, improves the power generation output of a fuel cell using hydrogen that operates under low humidity conditions, and is 100 ° C. or higher. It exhibits high ionic conductivity even under high temperature and low humidity conditions. The electrolyte membrane is excellent in flexibility, moldability and processability, and has high mechanical durability. Therefore, the membrane-electrode assembly using the electrolyte membrane can exhibit excellent performance in a fuel cell that uses hydrogen as a fuel and operates under low humidity conditions and high temperature non-humidified conditions. In addition, the electrolyte can also be used as a binder for an electrolyte membrane for a fuel cell using a methanol aqueous solution as a fuel, and a fuel cell electrode catalyst layer from the viewpoint of high ion conductivity and moisture management of the fuel cell. .

  Hereinafter, the present invention will be described in detail. The block copolymer constituting the polymer electrolyte of the present invention is a block copolymer comprising polymer blocks (A) and (B) that are phase-separated from each other, and the polymer block (A) is an ion. It has a conductive group, the polymer block (B) forms a flexible phase, and the ion conductive group is a block copolymer which exists substantially only in the polymer block (A). The block copolymer can be a polymer skeleton such as an addition polymerization polymer, a polycondensation polymer, a polyaddition polymer, a vinyl polymer, a polyurethane, a polyether, a polysiloxane, a polyester, Polyamide, polycarbonate, polysulfide, polyamine, polysilane, polyazomethine, polyhydrazide, polyanhydride, polythioester, polythiocarbonate, polythioamide, polyphosphonate, polysulfonamide, polyphosphonate ester, polyphosphate ester, polyphosphonamide, polyphenylene , Polyketone, polysulfone, polyamideimide, polyimide, polyetheramide, polybenzoazole, polyoxazole, polythiazole, polyimidazole, polypyrazole, polyoxadiazole, polytriazol 1 or 2 or more polymer blocks (A) and polymer blocks each selected from the group consisting of polytriazine, polyimidine, polyquinoline, polybenzoxazinone, polyquinazolone, polyquinazolinedione, polyquinoxaline, polyphthalazinone, etc. (B) The block copolymer is synthesized by addition polymerization, coordination polymerization, group transfer polymerization, photopolymerization, radiation polymerization, polycondensation, ring-opening polymerization, polyaddition, electrolytic polymerization, oxidation polymerization, or the like. As the block copolymer, a vinyl block copolymer is preferable because of the simplicity of precision polymerization and the variety of applicable polymerization techniques.

  As the polymer block (A) constituting the vinyl block copolymer, it is easy to introduce an ion conductive group, a variety of synthetic techniques applicable to the introduction of an ion conductive group, and durability. Therefore, an aromatic vinyl polymer block (Aa) mainly composed of aromatic vinyl compound units is preferable. As the aromatic vinyl compound unit constituting the aromatic vinyl polymer block (Aa), the following general formula (I)

(In the formula, Ar represents an aryl group having 6 to 14 carbon atoms which may have 1 to 3 substituents, and R ¹ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or 1 to 3 carbon atoms. Represents an aryl group having 6 to 14 carbon atoms which may have a substituent. The main repeating unit may be comprised from 1 type chosen from the unit represented by general formula (I), and may be comprised from 2 or more types.

Examples of the aryl group having 6 to 14 carbon atoms in the definition of Ar include a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, an indenyl group, and a biphenylyl group. In the case where the aryl group has 1 to 3 substituents, the substituent is independently a linear or branched alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group). , Butyl group, etc.), halogenated alkyl groups having 1 to 4 carbon atoms (chloromethyl group, 2-chloroethyl group, 3-chloropropyl group, etc.) and the like. The alkyl group having 1 to 4 carbon atoms in the definition of R ¹ may be linear or branched, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group. Examples of the aryl group having 6 to 14 carbon atoms in the definition of R ¹ include those similar to the aryl group having 6 to 14 carbon atoms which may have 1 to 3 substituents in the definition of Ar. .

When R ¹ is an alkyl group having 1 to 4 carbon atoms, Ar preferably has no substituent, but when it has a substituent, the number of substituents is 1 or 2. Preferably, it is one. When R ¹ is an aryl group having 6 to 14 carbon atoms, it is most preferable that either or both of this aryl group and Ar have no substituent, but when both have a substituent, The number is preferably 1 or 2, and more preferably 1.

Specific examples of the aromatic vinyl compound capable of constituting the aromatic vinyl compound unit by polymerization include styrene, vinyl naphthalene, vinyl anthracene, vinyl phenanthrene, vinyl biphenyl, α-methyl styrene, 1-methyl-1-naphthyl ethylene, Examples thereof include 1-methyl-1-biphenylylethylene, and styrene and α-methylstyrene are particularly preferable.
The above aromatic vinyl compounds may be used alone or in combination of two or more. The form in the case of copolymerizing two or more types may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.

  The aromatic vinyl polymer block (Aa) may contain one or more other monomer units in addition to the aromatic vinyl compound unit as long as the effects of the present invention are not impaired. . Examples of the monomer that gives such other monomer units include conjugated alkadienes having 4 to 8 carbon atoms (specific examples are the same as those in the description of the polymer block (B) described later), and alkenes having 2 to 8 carbon atoms. (Specific examples are the same as in the description of the polymer block (B) described later), (meth) acrylate esters (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl Examples include esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ethers (methyl vinyl ether, isobutyl vinyl ether, etc.), and the like. The copolymerization form of the aromatic vinyl compound and the other monomer needs to be random copolymerization.

  The ratio of the aromatic vinyl compound unit contained in the aromatic vinyl polymer block (Aa) is preferably 50 mol% or more, and preferably 60 mol% or more from the viewpoint of imparting sufficient ion conductivity. Is more preferable, and it is still more preferable that it is 80 mol% or more.

  The molecular weight of the polymer block (A) in the state where the ion conductive group is not introduced is appropriately selected depending on the properties of the polymer electrolyte, required performance, other polymer components, etc., but the number average molecular weight in terms of polystyrene In general, it is preferably selected from 100 to 1,000,000, more preferably selected from 500 to 100,000.

  The polymer block (A) may be crosslinked by a known method within a range not impairing the effects of the present invention. By introducing the cross-linking, the ion channel phase formed by the polymer block (A) becomes difficult to swell, and the change in mechanical properties (such as tensile properties) between dry and wet tends to be small.

  In addition to the polymer block (A), the block copolymer used in the polymer electrolyte of the present invention has a polymer block (B) that forms a flexible phase and has substantially no ion conductive group. A compound unit capable of forming a flexible phase is selected as the main repeating compound unit of the polymer block (B). When the polymer block (B) forms a flexible phase, the block copolymer becomes elastic and flexible as a whole, and formability (assembleability) in the production of membrane-electrode assemblies and polymer electrolyte fuel cells. , Bondability, tightenability, etc.) are improved. The polymer block (B) here is a so-called rubber-like polymer block having a glass transition point or softening point of 50 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower.

  When the block copolymer used in the present invention is a vinyl block copolymer, the polymer block (B) forms a flexible phase and has substantially no ion conductive group. The block (Ba) is used. The vinyl compound unit that can constitute the vinyl polymer block (Ba) includes alkene units having 2 to 8 carbon atoms, cycloalkene units having 5 to 8 carbon atoms, vinyl cycloalkene units having 7 to 10 carbon atoms, carbon Examples thereof include conjugated alkadiene units having 4 to 8 carbon atoms, conjugated cycloalkadiene units having 5 to 8 carbon atoms, acrylic acid ester units, vinyl ester units, and vinyl ether units. The vinyl compounds giving these units can be used alone or in combination of two or more. The form in the case of copolymerizing two or more types may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization. Further, when the monomer to be used for (co) polymerization has two carbon-carbon double bonds, any of them may be used for the polymerization, and part or all of the double bonds remaining after the polymerization are hydrogen. Further, when the monomer is a conjugated alkadiene, it may be a 1,2-bond, a 3,4-bond or a 1,4-bond, and has a glass transition point. Or if a softening point is 50 degrees C or less, there will be no restriction | limiting in particular also in the ratio of a 1, 2- bond or a 3, 4- bond, and a 1, 4- bond.

  The vinyl polymer block (Ba) has a carbon number from the viewpoint of giving the obtained block copolymer flexibility and elasticity, and thus good moldability in the production of a membrane-electrode assembly and a polymer electrolyte fuel cell. From a 2-8 alkene unit, a C5-C8 cycloalkene unit, a C7-10 vinylcycloalkene unit, a C4-8 conjugated alkadiene unit, a C5-8 conjugated cycloalkadiene unit It is preferably a polymer block having at least one selected as a main repeating unit, and at least one selected from an alkene unit having 4 to 8 carbon atoms and a conjugated alkadiene unit having 4 to 8 carbon atoms is used as a main repeating unit. More preferably, the polymer block is at least selected from alkene units having 4 to 6 carbon atoms and conjugated alkadiene units having 4 to 8 carbon atoms. And even more preferably one is a polymer block whose main repeating unit. In the above, the most preferable alkene unit is an isobutene unit, an amorphous hydrogenated 1,3-butadiene unit (an optionally mixed 1-butene unit or a 2-butene unit), a hydrogenated isoprene unit (a mixed one). 2-methyl-1-butene unit, 3-methyl-1-butene unit, 2-methyl-2-butene unit), and the most preferable conjugated alkadiene unit is an amorphous 1,3-butadiene unit. And / or isoprene units.

As in the case where the main repeating unit of the vinyl polymer block (Ba) is a vinylcycloalkene unit, a conjugated alkadiene unit, or a conjugated cycloalkadiene unit, the monomer that can constitute the repeating unit is a plurality of carbon- When it has a carbon double bond, the carbon-carbon double bond usually remains in the polymer after polymerization. Thus, when a carbon-carbon double bond remains in the polymer, such a point is required from the viewpoints of power generation performance and heat resistance deterioration of the membrane-electrode assembly using the polymer electrolyte membrane of the present invention. More than 30 mol% of the carbon-carbon double bond is preferably hydrogenated, more preferably 50 mol% or more is hydrogenated, more preferably 80 mol% or more is hydrogenated. Even more preferred. The hydrogenation rate of the carbon-carbon double bond can be calculated by a commonly used method, for example, iodine value measurement method, ¹ H-NMR measurement or the like.

  A vinyl compound that gives a vinyl compound unit capable of forming the above-described flexible phase in the vinyl polymer block (Ba) will be described. The alkenes having 2 to 8 carbon atoms include ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene and 1-octene. , 2-octene and the like. Examples of the cycloalkene having 5 to 8 carbon atoms include cyclopentene, cyclohexene, cycloheptene and cyclooctene. Examples of the vinylcycloalkene having 7 to 10 carbon atoms include vinylcyclopentene, vinylcyclohexene and vinylcyclohexane. Heptene, vinylcyclooctene, etc. are mentioned. As the conjugated alkadiene having 4 to 8 carbon atoms, 1,3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3 -Dimethyl-1,3-butadiene, 2-ethyl-1,3-butyl Diene, 1,3-heptadiene, 1,4-heptadiene, 3,5-heptadiene and the like, cyclopentadiene, 1,3-cyclohexadiene, and the like as a conjugated cycloalkadiene having 5 to 8 carbon atoms. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, and butyl acrylate. Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate. Examples of the vinyl ether include methyl vinyl ether. And isobutyl vinyl ether.

  Further, the vinyl polymer block (Ba) does not impair the purpose of the polymer block (B) that gives the block copolymer flexibility and elasticity other than the vinyl compound unit capable of forming the flexible phase. It may contain other monomer units, for example, halogen-containing vinyl compound units such as aromatic vinyl compound units and vinyl chloride units. In this case, it is necessary that the copolymerization form of the vinyl compound capable of forming the flexible phase and the other monomer is random copolymerization. The amount of the other monomer used is preferably less than 50% by mass and less than 30% by mass with respect to the total of the vinyl compound capable of forming the flexible phase and the other monomer. Is more preferable, and it is still more preferable that it is less than 10 mass%.

  The block copolymer constituting the polymer electrolyte of the present invention is different from the polymer block (A) and the polymer block (B), and is phase-separated from these and has substantially no ion conductive group. It is a polymer block, Comprising: The polymer block (C) which functions as a constrained phase may be included. As the polymer block (C), when the block copolymer is a vinyl block copolymer, for example, a polymer block having an aromatic vinyl compound unit as a main repeating unit, a crystalline polyolefin block and the like can be mentioned. It is done. By causing the polymer block (C) to function as a constraining phase, it is possible to reduce dimensional changes and changes in mechanical properties (such as tensile strength) caused by repetition of operation and stop of the polymer electrolyte fuel cell, Changes in methanol permeability, ionic conductivity, and the like before and after power generation in a direct methanol solid polymer fuel cell can be reduced.

  The aromatic vinyl compound unit in the case of constituting the main repeating unit in the polymer block (C) is represented by the general formula (II)

(In the formula, R ^{2 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, but at least one is an alkyl group having 1 to 8 carbon atoms, and R ⁵ is a hydrogen atom or carbon. It is preferably at least one unit selected from aromatic vinyl compound units represented by formula (1-4).

Regarding each group in the general formula (II), the alkyl group having 1 to 8 carbon atoms in the definition of R ^{2 to} R ⁴ includes a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, Examples include linear alkyl groups such as octyl group, branched alkyl groups such as isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, and 1-methylpentyl group. In the definition of R ⁵ , examples of the alkyl group having 1 to 4 carbon atoms include branched alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, an isopropyl group, an isobutyl group, and a tert-butyl group. An alkyl group. Preferable specific examples of the aromatic vinyl compound unit represented by the general formula (II) include p-methylstyrene unit, 4-tert-butylstyrene unit, p-methyl-α-methylstyrene unit, 4-tert- Examples include butyl-α-methylstyrene units. These aromatic vinyl compounds giving an aromatic vinyl compound unit may be used alone or in combination of two or more. The form in the case of copolymerizing two or more types may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.

  When the polymer block (C) has an aromatic vinyl compound unit as a main repeating unit, the polymer block (C) has a monomer unit other than the aromatic vinyl compound unit as a binding phase. The monomer which may be contained within a range not hindering the function and gives another monomer unit is, for example, a conjugated alkadiene having 4 to 8 carbon atoms (specific examples are the polymer block (B) described above). ), (Meth) acrylate ester (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl ester (vinyl acetate, vinyl propionate, vinyl butyrate, Vinyl pivalate, etc.) and vinyl ether (methyl vinyl ether, isobutyl vinyl ether, etc.). At this time, the copolymerization form of the aromatic vinyl compound and the other monomer needs to be random copolymerization.

  From the viewpoint of fulfilling the function as a constrained phase, the aromatic vinyl compound unit described above preferably accounts for 50 mol% or more, more preferably 70 mol% or more of the polymer block (C), and more preferably 90 mol%. It is even more preferable to occupy% or more.

  When the polymer block (C) is constituted by a crystalline polyolefin block, examples of the crystalline polyolefin block include a crystalline polyethylene block, a crystalline polypropylene block, a crystalline hydrogenated 1,4-polybutadiene block, and the like. Of these, crystalline hydrogenated 1,4-polybutadiene blocks are most preferred.

  From the viewpoint of causing the polymer block (C) to phase-separate from the polymer block (A) and the polymer block (B) and to function as a constrained phase, examples of the polymer block (C) that are particularly suitable include poly p -Polystyrene blocks such as methylstyrene block, poly-4- (tert-butyl) styrene block, poly p-methyl-α-methylstyrene block, poly-4-tert-butyl-α-methylstyrene block; Copolymers in which two or more selected from alkyl-substituted styrenes such as p-methylstyrene, 4- (tert-butyl) styrene, p-methyl-α-methylstyrene, 4-tert-butyl-α-methylstyrene are copolymerized Polymer block; crystalline hydrogenated 1,4-polybutadiene block; crystalline polyethylene block; crystalline poly (B) pyrene block, and the like.

  The molecular weight of the polymer block (C) is appropriately selected depending on properties of the polymer electrolyte, required performance, other polymer components, and the like. When the molecular weight is large, the mechanical properties of the polymer electrolyte tend to be high, but when it is too large, it becomes difficult to mold the block copolymer, and when the molecular weight is small, the mechanical properties tend to be low, and the required performance is reduced. It is important to select the molecular weight accordingly. The number average molecular weight in terms of polystyrene is usually preferably selected from 100 to 1,000,000, more preferably from 1,000 to 100,000.

  Although the structure of the block copolymer comprised from a polymer block (A), a polymer block (B), and a polymer block (C) is not specifically limited, As an example, AB diblock copolymer, A -B-A type triblock copolymer, B-A-B triblock copolymer, A-B-C type triblock copolymer, A-B-C-A type tetrablock copolymer, A- B-A-C type tetrablock copolymer, B-A-B-C type tetrablock copolymer, A-B-C-B type tetrablock copolymer, C-B-C-A type tetrablock copolymer Copolymer, C-A-B-A-C type pentablock copolymer, C-B-A-B-C type pentablock copolymer, A-C-B-C-A type pentablock copolymer Combined, A-C-B-A-C type pentablock copolymer, A-B-C-A-B type pen tab Copolymer, A-B-C-A-C type pentablock copolymer, A-B-C-B-C type pentablock copolymer, A-B-A-B-C type pentablock Copolymer, ABACACB type pentablock copolymer, BABACA type pentablock copolymer, BABACA type pentablock copolymer Examples thereof include B-A-B-C-B type pentablock copolymer and C-A-C-B-C type pentablock copolymer.

  From the viewpoint of the flexibility of the electrolyte, it is preferable that both ends of at least one B block are bonded to other blocks and are not terminals of the block copolymer. It is preferable to have a plurality of C blocks.

  The block copolymer used in the present invention includes those partially containing graft bonds. Examples of the block copolymer partially containing a graft bond include those in which a part of the constituting polymer block is grafted to the main part (for example, main chain) of the block copolymer.

  When the block copolymer used in the present invention has two or more polymer blocks (A), they may be the same or different in structure and molecular weight. Further, when the block copolymer has two or more polymer blocks (B), they may be the same or different in structure and molecular weight. When the block copolymer has two or more polymer blocks (C), they may be the same or different in structure and molecular weight.

  In the block copolymer used in the present invention, the mass ratio of the sum of the polymer block (A) and the polymer block (C) to the polymer block (B) depends on the required performance, flexibility, elasticity, and membrane- It is important to select appropriately from the viewpoint of giving good moldability in the production of the electrode assembly and the polymer electrolyte fuel cell. When the mass ratio of the polymer block (B) is too small, the flexibility, elasticity, and moldability are poor, and the electrolyte membrane becomes rigid, so the mechanical durability tends to decrease. On the other hand, when the mass ratio of the polymer block (B) is too large, not only the morphological stability and membrane strength of the electrolyte membrane are lowered, but also the proportion of the polymer block (A) contributing to ionic conduction is lowered. Therefore, the ionic conductivity is lowered. From the above viewpoint, the mass ratio of the polymer block (A) and the polymer block (B) to the polymer block (B) in the electrolyte of the present invention is preferably 90:10 to 10:90, 70:30 to 30:70 is more preferable, and 60:40 to 40:60 is even more preferable.

  The number average molecular weight of the block copolymer constituting the electrolyte of the present invention in a state where the ion conductive group is not introduced is not particularly limited, but the number average molecular weight in terms of polystyrene is usually 10,000 to 2,000. 1,000, preferably 15,000 to 1,000,000, more preferably 20,000 to 500,000.

The block copolymer used in the present invention needs to have an ion conductive group in the polymer block (A). Examples of ions in the present invention when referring to ionic conductivity include protons. The ion conductive group is not particularly limited as long as the membrane-electrode assembly produced using the polymer electrolyte membrane can express sufficient ionic conductivity. Among them, -SO ₃ M or- A sulfonic acid group, a phosphonic acid group or a salt thereof represented by PO ₃ HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion) is preferably used. As the ion conductive group, a carboxyl group or a salt thereof can also be used. The introduction position of the ion conductive group is set to the polymer block (A) because the introduction of the ion conductive group is easy and the formation of the ion channel is facilitated.

  There are no particular restrictions on the position at which the ion conductive group is introduced into the polymer block (A), and even if it is introduced into the aromatic vinyl compound unit which is the main repeating unit, it is introduced into the other monomer units described above. May be. However, from the viewpoint of facilitating ion channel formation and suppression of MCO in DMFC, it is preferably introduced into the aromatic ring of the aromatic vinyl compound unit.

In the present invention, the ion conductive group is substantially present only in the polymer block (A). This is in part for facilitating the formation of ion channels and in part for the purpose of substantially limiting the components that form the ion channels to the polymer block (A). By forming an ion channel with a single component, ion conductive groups exist at a high density, and high-efficiency ion conduction is possible.
In the present invention, the fact that the ion conductive group is substantially present only in the polymer block (A) is 70 mol% or more, preferably 80 mol% or more, more preferably, of the ion conductive group present in the block copolymer. Means 90 mol% or more, more preferably 95 mol% or more is present in the polymer block (A).

  The amount of ion-conductive group introduced is important in determining the performance of the polymer electrolyte. In order to exhibit sufficient ion conductivity for using the polymer electrolyte of the present invention as a polymer electrolyte membrane in a solid polymer fuel cell, the ion exchange capacity of the polymer electrolyte of the present invention is 0.30 meq / The amount is preferably such that it is at least g, more preferably at least 0.35 meq / g. The upper limit of the ion exchange capacity is preferably 3.0 meq / g or less, because if the ion exchange capacity becomes too large, hydrophilicity tends to increase and it tends to swell.

  The block copolymer used in the present invention can be obtained mainly by the following two production methods. That is, (1) a method in which a block copolymer having no ion conductive group is produced and then the ion conductive group is bonded; (2) a block copolymer using a monomer having an ion conductive group It is a method of manufacturing.

  First, the first manufacturing method will be described. When the block copolymer is a vinyl block copolymer, the polymer block (A), (A), (B) or (C) may be polymer block (A), ( The production method of B) or (C) is appropriately selected from a radical polymerization method, an anionic polymerization method, a cationic polymerization method, a coordination polymerization method and the like, but from the viewpoint of industrial ease, a radical polymerization method, an anionic polymerization or a cation. A polymerization method is preferably selected. In particular, a so-called living polymerization method is preferred from the viewpoint of molecular weight, molecular weight distribution, polymer structure, ease of bonding of polymer blocks (A), (B) and (C), and specifically, a living radical polymerization method or a living Anionic polymerization and living cationic polymerization are preferred.

  Specific examples of the production method include a polymer block (C) having an aromatic vinyl compound such as 4-tert-butylstyrene as a main repeating unit, a polymer block (A) comprising styrene or α-methylstyrene, and a conjugated alkadiene. A method for producing a block copolymer comprising a polymer block (B) comprising: In this case, it is preferable to produce by a living anionic polymerization method and a living cationic polymerization method from the viewpoint of industrial ease, molecular weight, molecular weight distribution, ease of bonding of polymer blocks (A), (B) and (C), etc. The following specific synthesis examples are shown.

In producing the block copolymer constituting the polymer electrolyte of the present invention by anionic polymerization,
(1) An anionic polymerization initiator is used in a cyclohexane solvent, and an aromatic vinyl compound such as 4-tert-butylstyrene is polymerized at a temperature of 10 to 100 ° C., and then a conjugated alkadiene and styrene are sequentially polymerized. And a method of obtaining an ABC type block copolymer,
(2) An anionic polymerization initiator is used in a cyclohexane solvent to polymerize an aromatic vinyl compound such as 4-tert-butylstyrene under a temperature condition of 10 to 100 ° C., and then sequentially polymerize styrene and a conjugated alkadiene. A method of obtaining a C-A-B-A-C type block copolymer by adding a coupling agent such as phenyl benzoate,
(3) Using an anionic polymerization initiator in a cyclohexane solvent, under a temperature condition of 10 to 100 ° C., aromatic vinyl compounds such as 4-tert-butylstyrene, conjugated alkadienes, 4-tert-butylstyrene, etc. Sequentially polymerize aromatic vinyl compounds to create a CBC block copolymer and add an anionic polymerization initiator system (anionic polymerization initiator / N, N, N ′, N′-tetramethylethylenediamine) And then lithiating the conjugated alkadiene unit and then polymerizing styrene to obtain a CB (-g-A) -C type block-graft copolymer,

(4) A concentration of 5 to 50% by mass at a temperature of −30 ° C. to 30 ° C. in the presence of a polar compound having a concentration of 0.1 to 10% by mass using an organolithium compound in a nonpolar solvent as an initiator. Α-methylstyrene is polymerized, and the resulting living polymer is sequentially polymerized with an aromatic vinyl compound such as conjugated alkadiene and 4-tert-butylstyrene to obtain an ABC type block copolymer,
(5) A concentration of 5 to 50% by mass at a temperature of −30 ° C. to 30 ° C. in the presence of a polar compound having a concentration of 0.1 to 10% by mass using an organolithium compound in a nonpolar solvent as an initiator. Α-methylstyrene is polymerized, and the resulting living polymer is polymerized with an aromatic vinyl compound such as 4-tert-butylstyrene and a conjugated alkadiene, and then added with a coupling agent such as phenyl benzoate. A method of obtaining a C—B—C—A type block copolymer can be employed / applied.

In producing the block copolymer constituting the polymer electrolyte of the present invention by cationic polymerization,
(6) Cationic polymerization of isobutene in the presence of Lewis acid using a bifunctional halogenated initiator at -78 ° C in a halogen / hydrocarbon mixed solvent, followed by styrene, 4-tert-butylstyrene A method of sequentially polymerizing styrene derivatives such as C-A-B-A-C type block copolymer can be employed / applied.

  Next, a method for bonding an ion conductive group to the resulting block copolymer will be described. First, a method for introducing a sulfonic acid group into the obtained block copolymer will be described. Sulfonation can be performed by a known sulfonation method. As such a method, an organic solvent solution or suspension of a block copolymer is prepared, a sulfonating agent is added and mixed, a method of adding a gaseous sulfonating agent directly to the block copolymer, etc. Is exemplified.

  Sulfonating agents used include sulfuric acid, a mixture of sulfuric acid and aliphatic acid anhydride, chlorosulfonic acid, a mixture of chlorosulfonic acid and trimethylsilyl chloride, sulfur trioxide, a mixture of sulfur trioxide and triethyl phosphate. Examples thereof include aromatic organic sulfonic acids represented by 2,4,6-trimethylbenzenesulfonic acid. Examples of the organic solvent to be used include halogenated hydrocarbons such as methylene chloride, linear aliphatic hydrocarbons such as hexane, cyclic aliphatic hydrocarbons such as cyclohexane, and the like. You may use it, selecting suitably from several combinations.

  A method for introducing phosphonic acid groups into the resulting block copolymer will be described. Phosphonation can be performed by a known phosphonation method. Specifically, for example, an organic solvent solution or suspension of a block copolymer is prepared, and the copolymer is reacted with chloromethyl ether or the like in the presence of anhydrous aluminum chloride to introduce a halomethyl group into the aromatic ring. Thereafter, there may be mentioned a method in which phosphorus trichloride and anhydrous aluminum chloride are added and reacted, followed by a hydrolysis reaction to introduce a phosphonic acid group. Alternatively, a method may be exemplified in which phosphorus trichloride and anhydrous aluminum chloride are added to the copolymer and reacted to introduce a phosphinic acid group into the aromatic ring, and then the phosphinic acid group is oxidized with nitric acid to form a phosphonic acid group.

As described above, the degree of sulfonation or phosphonation is such that the ion exchange capacity of the polymer electrolyte of the present invention is 0.30 meq / g or more, particularly 0.35 meq / g or more, but 3.00 meq. It is desirable to sulfonate or phosphonate so that it is less than / g. Thereby, practical ion conduction performance is obtained. The ion exchange capacity of the finally obtained polyelectrolyte, the ion exchange capacity of the sulfonated or phosphonated block copolymer, or the sulfonation rate or phosphonation rate in the polymer block (A) in the block copolymer Can be calculated using analytical means such as acid value titration method, infrared spectroscopic spectrum measurement, nuclear magnetic resonance spectrum ( ¹ H-NMR spectrum) measurement.

  The second production method of the block copolymer used in the present invention is a method for producing a block copolymer using at least one monomer having an ion conductive group. When the block copolymer is a vinyl block copolymer, the monomer having an ion conductive group is preferably a monomer in which an ion conductive group is bonded to an aromatic vinyl compound. Specifically, o, m or p-alkylstyrene sulfonic acid, α-alkyl-o-, m- or p-alkyl-styrenesulfonic acid, α-alkyl-vinylnaphthalenesulfonic acid, α-alkyl-vinylanthracenesulfone Acid, α-alkyl-vinylpyrenesulfonic acid, o-, m- or p-alkylstyrene phosphonic acid, α-alkyl-o-, m- or p-alkyl-styrenephosphonic acid, α-alkyl-vinylnaphthalenephosphonic acid , Α-alkyl-vinylanthracenephosphonic acid, α-alkyl-vinylpyrenephosphonic acid and the like.

  As the monomer containing an ion conductive group, a monomer in which an ion conductive group is bonded to a conjugated alkadiene compound can also be used. Specifically, 1,3-butadiene-1-sulfonic acid, 1,3-butadiene-2-sulfonic acid, isoprene-1-sulfonic acid, isoprene-2-sulfonic acid, 1,3-butadiene-1-phosphone Examples include acid, 1,3-butadiene-2-phosphonic acid, isoprene-1-phosphonic acid, and isoprene-2-phosphonic acid.

  Examples of the monomer containing an ion conductive group include vinyl sulfonic acid, α-alkyl-vinyl sulfonic acid, vinyl alkyl sulfonic acid, α-alkyl-vinyl alkyl sulfonic acid, vinyl phosphonic acid, α-alkyl-vinyl phosphone. Acid, vinyl alkyl phosphonic acid, α-alkyl-vinyl alkyl phosphonic acid and the like can also be used. As the monomer containing ion conductivity, a (meth) acrylic monomer to which an ion conductive group is bonded can also be used. Specific examples include methacrylic acid, acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, and the like.

  The ion conductive group may be introduced in the form of a salt neutralized with a suitable metal ion (for example, alkali metal ion) or counter ion (for example, ammonium ion). For example, by producing a polymer using sodium o-, m- or p-alkylstyrene sulfonate, or sodium α-methyl-o-, m- or p-alkylstyrene sulfonate, the desired ionic conductivity can be obtained. A group can be introduced. Moreover, the block copolymer which made the sulfonic acid group into the salt form can be obtained by ion-exchange by a suitable method.

The metal phosphate used in the present invention is, as a raw material, M (where M is one or more elements selected from the group consisting of elements of groups 4 and 14 of the long-period periodic table) And a compound containing J (where J is one or more elements selected from the group consisting of elements of Group 3, Group 13, Group 5 and Group 15 of the Long Periodic Periodic Table) And a compound containing P). The metal phosphate is preferably substantially represented by the following formula (1):
M _1-x J _x P ₂ O ₇ (1)
(In the formula, x represents a numerical value of 0.001 to 0.5, and M and J are as defined above).

  What is substantially represented by the formula (1) is the composition ratio of the formula (1), that is, the molar ratio of M: J: P: O (1-x): x: 2: 7. In the range which does not inhibit the effect by this metal phosphate in, it means that 2 and 7 which are the ratio of P and O may be slightly increased / decreased, respectively. Depending on the type of M and J used, the amount is usually within about ± 10%, that is, the molar ratio of phosphorus atoms is 1.8 to 2.2, and the molar ratio of oxygen atoms is 6.3 to 7 It means that it may vary independently within the range of .7. It is. However, the degree of increase / decrease is preferably as small as possible.

  Examples of M include Ti, Zr, Hf, etc. as metals belonging to Group 4, and Si, Ge, Sn, Pb, etc., as metals belonging to Group 14, and J, as metals belonging to Group 3 As metals belonging to Group 15, such as Sc, Y, La, Ce, Yb, etc., B, Al, Ga, In, etc. as metals belonging to Group 13, V, Nb, Ta, etc. as metals belonging to Group 5 Sb, Bi and the like. M is preferably Ti, Zr, Hf, Si, Ge, Sn and Pb, and J is preferably Al and In.

  The compound containing M may be appropriately selected depending on the kind of M, but an oxide is used, or decomposition and / or oxidation is performed at a high temperature such as hydroxide, carbonate, nitrate, halide, oxalate, etc. Thus, an oxide capable of becoming an oxide can be used. When Ti, Zr, Ge, or Sn is used as M, compounds containing M include titanium (IV) chloride, titanium (IV) iodide, titanium (IV) oxide, titanium (IV) ethoxide, zirconium bromide (IV ), Zirconium chloride (IV), zirconium oxide (IV), zirconium carbonate (IV), zirconium (IV) ethoxide, germanium bromide (IV), germanium iodide (IV), germanium oxide (IV), tin acetate (IV) ), Tin (IV) fluoride, tin (IV) chloride, tin (IV) bromide, tin (IV) iodide, tin (IV) oxide, and hydrates thereof. Among the above compounds, oxides or hydrates thereof can be preferably used from the viewpoint of cost and safety of by-products generated by decomposition and / or oxidation at high temperature.

  Examples of the compound containing P include phosphoric acid and phosphonic acid, and phosphoric acid is preferable from the viewpoint of reactivity with M and J. As the phosphoric acid supply source, a concentrated phosphoric acid aqueous solution of 50% or more is usually used, but an 80-90% concentrated phosphoric acid aqueous solution is preferable from the viewpoint of operability.

The compound containing J may be appropriately selected from known compounds. Specifically, an oxide is used, or a hydroxide, halide, nitrate, acetate, carbonate, alkoxide (ethoxide, Isopropoxide or the like), oxalate, or the like that can be decomposed and / or oxidized at high temperature to form an oxide may be used. When Sc, Y, La, Yb, B, Al, Ga, In, or Bi is used as J, compounds containing J include scandium (III) acetate, scandium (III) carbonate, scandium fluoride (III), Scandium chloride (III), scandium iodide (III), scandium nitrate (III), scandium oxide (III), yttrium acetate (III), yttrium fluoride (III), yttrium chloride (III), yttrium bromide (III) , Yttrium nitrate (III), yttrium oxalate (III), yttrium oxide (III), yttrium (III) isopropoxide, lanthanum acetate, lanthanum carbonate (III), lanthanum fluoride (III), lanthanum chloride (III), Lanthanum (III) bromide, lanthanum iodide (III), lanthanum nitrate (III), lanthanum oxalate (III), lanthanum oxide (III), ytterbium acetate, ytterbium carbonate (III), ytterbium fluoride, ytterbium chloride (III), ytterbium bromide (III), iodine Ytterbium (III), ytterbium nitrate (III), ytterbium oxalate (III), ytterbium oxide (III), boron fluoride (III), boron chloride (III), boron bromide (III), boron oxide (III) , Aluminum carbonate (III), aluminum fluoride (III), aluminum chloride (III), aluminum bromide (III), aluminum iodide (III), aluminum nitrate (III), aluminum oxalate (III), aluminum oxide ( III , Aluminum hydroxide (III), aluminum (III) ethoxide, aluminum (III) _{isopropoxide, α-Al 2 O 3,} γ-Al 2 O 3, fluorinated gallium (III), gallium chloride (III), odor Gallium (III) iodide, gallium nitrate (III), gallium oxide (III), indium (III) acetate, indium (III) chloride, indium (III) bromide, indium (III) iodide, indium (III) nitrate, Indium (III) oxide, indium (III) hydroxide, indium (III) isopropoxide, bismuth acetate (III), bismuth (III) fluoride, bismuth chloride (III), bismuth bromide (III), bismuth iodide (III), bismuth nitrate (III), bismuth oxide (III), and These hydrates can be exemplified. Among the above compounds, oxides, hydroxides, or hydrates thereof can be preferably used from the viewpoints of cost and safety of by-products generated by decomposition and / or oxidation at high temperature.

Using the above raw materials, a metal phosphate can be produced by including the following steps (a) and (b) in this order:
(A) a step of reacting a compound containing M, a compound containing J and a compound containing P, such as phosphoric acid, to obtain a reaction product,
(B) A step of heat-treating the reactant.

  In the step (a), the reaction temperature is appropriately selected depending on the composition of the metal phosphate to be synthesized, and is usually performed at a temperature in the range of 200 to 400 ° C. Preferably, the temperature is in the range of 250 to 350 ° C., M contains Ti, Zr, Ge, or Sn, and J contains Sc, Y, La, Yb, B, Al, Ga, In, or Bi When it does, 270-330 degreeC is more preferable. Further, during the reaction, it is preferable to sufficiently mix by stirring. From the viewpoint of the operability of the resulting reactant, it may be effective to add an appropriate amount of water during the reaction in order to maintain an appropriate viscosity of the reactant and prevent solidification. The reaction time is appropriately selected according to the composition of the metal phosphate to be synthesized, and should be as long as possible. However, considering productivity, it is preferably in the range of 1 to 50 hours, M contains Ti, Zr, Ce or Sn, and J is Sc, Y, La, Yb, B, Al, Ga, In the case of containing In or Bi, it is more preferably in the range of 1 to 20 hours.

  The reaction product obtained in the step (a) is in a paste form, and the metal phosphate can be obtained by heat-treating the reaction product in the step (b). The temperature of the heat treatment is appropriately selected depending on the composition of the metal phosphate to be synthesized, and is preferably performed in the range of 500 to 800 ° C., when M is Ti, Zr, Ge or Sn, and / or J is Sc. , Y, La, Yb, B, Al, Ga, In, or Bi, a range of 600 to 700 ° C is more preferable, and a range of 630 to 680 ° C is even more preferable. The heat treatment time is appropriately selected depending on the composition of the metal phosphate to be synthesized, and is preferably in the range of 1 to 20 hours. When M is Ti, Zr, Ge or Sn, and / or J is Sc, In the case of Y, La, Yb, B, Al, Ga, In or Bi, the range of 1 to 5 hours is more preferable, and the range of 2 to 5 hours is even more preferable.

  The mass ratio of the electrolyte constituting the first aspect of the present invention, and thus the copolymer constituting the electrolyte membrane and the metal phosphate, should be appropriately selected from the viewpoint of required performance such as film formability, membrane strength, ionic conductivity, and MCO. is important. When the mass ratio of the metal phosphate is too small, the effect of improving the ionic conductivity tends to be insufficient. On the other hand, when the mass ratio of the metal phosphate is too large, the membrane strength, dimensional stability, and morphological stability of the electrolyte membrane tend to decrease when wet. From the above viewpoint, the mass ratio of the copolymer and the metal phosphate in the electrolyte and thus the electrolyte membrane of Embodiment 1 of the present invention is preferably 99: 1 to 30:70, and 70:30 to 30:70 is More preferably, it is more preferable that it is 50: 50-30: 70.

  It is important that the mass ratio of the electrolyte constituting the second aspect of the present invention, that is, the copolymer constituting the electrolyte membrane and the metal phosphate is appropriately selected from the viewpoint of required performance such as film formability, membrane strength, and ionic conductivity. It is. When the mass ratio of the metal phosphate is too small, the effect of improving the ionic conductivity tends to be insufficient. On the other hand, when the mass ratio of the metal phosphate is too large, the membrane strength, dimensional stability, and morphological stability of the electrolyte membrane tend to decrease when wet. From the viewpoints described above and from the viewpoint specific to the present invention of Embodiment 2, that is, from the viewpoint of developing high proton conductivity even under conditions of high temperature, low humidity, or no humidification, the electrolyte of Embodiment 2 of the present invention and the electrolyte The mass ratio of the copolymer to the metal phosphate in the membrane is preferably 80:20 to 1:99, more preferably 70:30 to 5:95, and 50:50 to 10:90. Even more preferred.

  The mass ratio of the copolymer constituting the electrolyte of Embodiment 3 of the present invention and the electrolyte membrane to the metal phosphate is not limited to the required performance such as film formability, membrane strength, ionic conductivity, MCO, etc. It is important to select appropriately according to the operating conditions of the fuel cell to be used. If the mass ratio of the metal phosphate is too small, the effect of improving the ionic conductivity tends to be insufficient, and if the mass ratio of the metal phosphate is too large, the membrane strength of the electrolyte membrane when wet, Dimensional stability and form stability tend to decrease. From the above viewpoint, a fuel cell that operates at a temperature of 100 ° C. or less and supplies a humidified hydrogen or methanol aqueous solution as a fuel, and a fuel cell that operates at a temperature of 100 ° C. or less and supplies a low humidified hydrogen or methanol vapor as a fuel. When used in the present invention, the mass ratio of the copolymer and the metal phosphate in the electrolyte and thus the electrolyte membrane of aspect 3 of the present invention is preferably 99: 1 to 30:70, and 70:30 to 30:70. Is more preferable, and it is still more preferable that it is 50: 50-30: 70. When used in a fuel cell that operates at a temperature of 100 ° C. or higher and supplies low-humidified hydrogen, non-humidified hydrogen, or hydrocarbon as fuel, the copolymer and metal in the electrolyte and thus the electrolyte membrane of the third aspect of the present invention The mass ratio of the phosphate is preferably 80:20 to 1:99, more preferably 70:30 to 5:95, and still more preferably 50:50 to 10:90.

  The particle size of the metal phosphate constituting the electrolyte of aspect 3 of the present invention is desirably selected as appropriate from the viewpoints of film strength and moldability in addition to required performance such as ion conductivity and MCO. When the particle size of the metal phosphate is too large, the contact area with the ion channel of the copolymer is reduced, and the distance between the metal phosphate particles is increased, so that the ion conduction efficiency tends to be reduced. . In addition, since the roughness and unevenness of the electrolyte membrane surface are increased, the bondability with the electrode is lowered, and the contact resistance generated at the interface between the electrode and the electrolyte membrane is increased. On the other hand, when the particle size of the metal phosphate is too small, the viscosity of the mixed solution composed of the copolymer and the metal phosphate is reduced due to the interaction that occurs between the particles during the preparation of the composite film described later. It increases remarkably and film formation becomes difficult. Moreover, since it becomes difficult to maintain the crystal structure of the metal phosphate necessary for the expression of ion conductivity, the ion conduction efficiency tends to decrease. From the above viewpoint, the average particle size of the metal phosphate in the electrolyte of aspect 3 of the present invention needs to be 10 nm to 1 μm, preferably 20 nm to 500 nm, and preferably 30 nm to 300 nm. More preferred.

The average particle diameter of the metal phosphate contained in the electrolyte of the embodiment 3 of the present invention can be measured by the following exemplified method:
(1) In the electron microscope observation image of the electrolyte, a method of measuring the long diameter of 100 metal phosphate particles and setting the average value as the average particle diameter of the metal phosphate,
(2) In the electron microscopic observation image of the electrolyte, planimetric method (drawing a known circular area (A) on the electron microscope image, the number of particles applied to the particle number n _c and the circumference of the circle n _{i .N} Request particle number _{n G} per unit area by the following equation from _{G = (n c + 1 /} 2n i) / (a / m 2) here, m is the magnification of the electron microscope image .1 / since N _G is an area occupied by one particle, 2 / √ particle diameter particles having a circle equivalent diameter (πN _G), when the side of the square obtained in 1 / √N _G.) than the metal phosphate Techniques that use composite electrolytes as measurement data, such as techniques for measuring average particle diameter.

A solution containing a dissolved block polymer and an insoluble metal phosphate is prepared by mixing an electrolyte with a solvent that does not dissolve the metal phosphate but dissolves the block polymer contained in the electrolyte.
(3) Measured by static light scattering method, median diameter is average particle size of metal phosphate, (4) Measured by dynamic light scattering method, median diameter is averaged of metal phosphate (5) A method for measuring the average particle size of the metal phosphate from the particle size distribution calculated by laser diffraction, measured using a laser diffraction particle size distribution measuring device,
(6) Measured using an electrical detection method, and the volume average particle size measured is the average particle size of the metal phosphate,
(7) In the measurement methods (3) to (6) described above, in order to prevent the metal phosphate particles from aggregating or settling, a proper method is used to maintain a good dispersion state of the metal phosphate. A method in which measurement is performed after or while performing the treatment.
(8) Mixing a solvent that does not dissolve the metal phosphate but dissolves the block polymer contained in the electrolyte and the electrolyte, and obtains the metal phosphorus from the solution containing the dissolved block polymer and the metal phosphate that does not dissolve. After recovering only the acid salt, the metal phosphate is sieved, and the average particle size of the metal phosphate is determined from the obtained particle size distribution.
In aspect 3 of the present invention, among these methods, the median diameter of the metal phosphate measured by the static light scattering method of (3) is used as the average particle diameter of the metal phosphate. More specifically, the median diameter of the metal phosphate measured using a particle size measuring device (LA-950 manufactured by HORIBA Ltd.) was used as the average particle diameter of the metal phosphate.

  The electrolyte of the present invention and the electrolyte membrane are not limited to the effects of the present invention, and various additives such as softeners, stabilizers, light stabilizers, antistatic agents, mold release agents, flame retardants, foaming agents, pigments , Dyes, brighteners, carbon fibers, inorganic fillers and the like may be used alone or in combination of two or more.

Examples of the softener include petroleum softeners such as paraffinic, naphthenic or aromatic process oils, paraffin, vegetable oil softeners, plasticizers, and the like.
Stabilizers include phenol-based stabilizers, sulfur-based stabilizers, phosphorus-based stabilizers, and the like. Specific examples include 2,6-di-t-butyl-p-cresol, pentaerythryl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Benzene, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2, -thio-diethylenebi [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrodinamide), 3, 5-di-t-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 3,9-bis {2- [3 Phenolic compounds such as-(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane Stabilizer; pentaerythrityl tetrakis (3-lauryl thiopropionate), distearyl 3,3′-thiodipropionate, dilauryl 3,3′-thiodipropione And sulfur stabilizers such as dimyristyl 3,3′-thiodipropionate; trisnonylphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, diasterylpentaerythritol diphosphite, Examples thereof include phosphorus stabilizers such as bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite.
Specific examples of the inorganic filler include talc, calcium carbonate, silica, glass fiber, mica, kaolin, titanium oxide, montmorillonite, and alumina.

  From the viewpoint of ion conductivity, the total content of the block copolymer and the metal phosphate in the electrolyte of the present invention, and in the electrolyte membrane, is preferably 50% by mass or more, and more preferably 70% by mass or more. 90% by mass or more is even more preferable.

Examples of the method for preparing the polymer electrolyte membrane of the present invention using the block copolymer, metal phosphate and additive used in the present invention include the following (c) and (d): A method comprising the steps in this order can be illustrated:
(C) A step of obtaining a mixed solution containing a block copolymer, a metal phosphate and an additive when used, and (d) a step of obtaining an electrolyte membrane using the mixed solution.
In addition, it is also possible to obtain the polymer electrolyte of the present invention without forming a film. After the step (c), the polymer electrolyte of the present invention is obtained by performing an operation with reference to the step (d). An electrolyte can be obtained.

  In step (c), the block copolymer constituting the electrolyte of the present invention is mixed with an appropriate solvent to dissolve or suspend the block copolymer, and the solution or suspension is mixed with a metal phosphate and Add additives for use, mechanically stir and knead to break up metal phosphate agglomerates, and then use metal phosphate and copolymer in suspension or copolymer solution A mixed solution in which the additive is uniformly dispersed is prepared. The solvent used at this time is capable of preparing a solution having a viscosity capable of being cast or coated without destroying the structure of the block copolymer, the metal phosphate, and the additive used. If it is, it will not specifically limit. Specifically, halogenated hydrocarbons such as methylene chloride, aromatic hydrocarbons such as toluene, xylene, and benzene, linear aliphatic hydrocarbons such as hexane and heptane, and cyclic aliphatic carbonization such as cyclohexane. Examples thereof include ethers such as hydrogen and tetrahydrofuran, alcohols such as methanol, ethanol, propanol, isopropanol, butanol and isobutyl alcohol, and mixed solvents thereof. Depending on the configuration of the block copolymer, the molecular weight, the ion exchange capacity, etc., one or more of the solvents exemplified above can be appropriately selected and used. Here, as a method of crushing the metal phosphate by mechanical stirring and kneading, (1) a mixed solution containing the block copolymer and the metal phosphate is mixed with a stirrer, a ball mill, a bead mill, an emulsifier, A method of kneading using a sonicator, a thin-film rotary stirrer, a high-pressure collision type pulverizer, etc., (2) Block copolymer after pulverizing metal phosphate using a collision type pulverizer, a hammer type pulverizer, etc. And (3) block copolymer and metal phosphate kneader (mixing roll, kneader, intensive mixer, etc.), uniaxial kneader (single screw extruder, special single screw) An example is a method of preparing a mixed liquid after kneading using an extruder, etc.), a twin-screw kneader (same direction rotary extruder, different direction rotary extruder, rotor type extruder, screw type extruder, etc.) Can Processing may be performed in combination of two or more methods from the methods described above.

  In step (d), the mixture of the copolymer, metal phosphate and additive used in step (c) is cast into a plate-like body such as PET or glass, or a coater or applicator. Etc., and removing the solvent under appropriate conditions, a method for obtaining an electrolyte membrane having a desired thickness, and a known method such as hot press molding, roll molding, extrusion molding, etc. An electrolyte membrane can be obtained using a method for obtaining the electrolyte membrane. The conditions for removing the solvent can be arbitrarily selected as long as the conditions allow the solvent to be completely removed at a temperature equal to or lower than the temperature at which ion conductive groups such as sulfonic acid groups in the block copolymer are removed. In order to express desired physical properties, a plurality of temperatures may be arbitrarily combined, or a combination of ventilation and vacuum may be arbitrarily combined. Specifically, after preliminary drying for several hours under vacuum conditions of room temperature to 60 ° C., the solvent is removed under vacuum conditions of 100 ° C. or higher, preferably 100 to 120 ° C. for about 12 hours. A method of removing the solvent under drying conditions of about several minutes to several hours under a draft of 60 to 140 ° C. can be exemplified, but is not limited thereto. In addition, a solution or suspension containing the same or different block copolymer or a mixture containing such a block copolymer, a metal phosphate, and an additive when used is newly added on the obtained electrolyte membrane. You may make it laminate | stack by apply | coating a liquid and drying. Further, the same or different electrolyte membranes obtained as described above may be laminated by being pressure-bonded by hot roll molding or the like.

  The thickness of the membrane made of the electrolyte of the present invention is appropriately selected according to the application. For example, when the membrane is used as an electrolyte membrane for a polymer electrolyte fuel cell, the thickness is preferably about 5 to 200 μm from the viewpoint of required performance, membrane strength, handling properties, and the like. When the film thickness is less than 5 μm, the mechanical strength of the film and the barrier properties of fuels such as hydrogen gas and methanol tend to be insufficient. On the other hand, when the film thickness exceeds 200 μm, the electric resistance of the film increases and the power generation characteristics of the battery tend to decrease. Therefore, the film thickness is more preferably 10 to 100 μm, and still more preferably 20 to 60 μm.

  Next, a membrane-electrode assembly using the electrolyte membrane of the present invention will be described. The production of the membrane-electrode assembly is not particularly limited, and a known method can be applied. For example, a catalyst paste containing an ion conductive binder is applied on the gas diffusion layer by a printing method or a spray method and dried. A method of forming a joined body of the catalyst layer and the gas diffusion layer, and then joining a pair of joined bodies to each side of the electrolyte membrane by hot pressing, etc. Is applied to both sides of the electrolyte membrane by a printing method or a spray method, dried to form catalyst layers, and a gas diffusion layer is pressure-bonded to each catalyst layer by hot pressing or the like. As yet another production method, a solution or suspension containing an ion conductive binder is applied to both surfaces of the electrolyte membrane and / or the catalyst layer surface of the pair of gas diffusion electrodes, and the electrolyte membrane and the catalyst layer surface are bonded to each other, There is a method of joining by pressure bonding or the like. In this case, the solution or suspension may be applied to either the electrolyte membrane or the catalyst layer surface, or may be applied to both. As another manufacturing method, first, the catalyst paste is applied to a base film made of polytetrafluoroethylene (PTFE) and dried to form a catalyst layer, and then a pair of base films on the base film is formed. There is a method in which a catalyst layer is transferred to both sides of an electrolyte membrane by thermocompression bonding, a base film is peeled to obtain a joined body of the electrolyte membrane and the catalyst layer, and a gas diffusion layer is crimped to each catalyst layer by hot pressing. is there. In these methods, an ion conductive group may be in a salt state with a metal such as Na, and a treatment for returning to a proton type by acid treatment after bonding may be performed.

  Examples of the ion conductive binder constituting the membrane-electrode assembly include existing perfluorocarbon sulfones such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore). An ion conductive binder made of an acid polymer, an ion conductive binder made of sulfonated polyethersulfone or sulfonated polyetherketone, an ion conductive binder made of polybenzimidazole impregnated with phosphoric acid or sulfuric acid can be used. . Moreover, you may produce an ion conductive binder from the block copolymer which is a main component of the electrolyte of this invention. In order to further enhance the adhesion between the electrolyte membrane and the gas diffusion electrode, it is preferable to use an ion conductive binder having the same or similar structure as the electrolyte membrane in contact with the gas diffusion electrode.

  The constituent material of the catalyst layer of the membrane-electrode assembly is not particularly limited as the conductive material / catalyst support, and examples thereof include carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like. These may be used alone or in combination of two or more. The catalyst metal may be any metal that promotes the oxidation reaction of fuel such as hydrogen and methanol and the reduction reaction of oxygen, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Cobalt, nickel, chromium, tungsten, manganese, palladium, etc., or alloys thereof, for example, platinum-ruthenium alloys are mentioned. Of these, platinum and platinum alloys are often used. The particle size of the metal serving as a catalyst is usually 10 to 300 angstroms. It is more advantageous in terms of cost if these catalysts are supported on a conductive material such as carbon / catalyst support because the amount of catalyst used can be reduced. The catalyst layer may contain a water repellent as necessary. Examples of the water repellent include various thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene copolymer, and polyether ether ketone.

  The gas diffusion layer of the membrane-electrode assembly is made of a material having conductivity and gas permeability, and examples of such a material include porous materials made of carbon fibers such as carbon paper and carbon cloth. Moreover, in order to improve water repellency, this material may be subjected to water repellency treatment.

  A polymer electrolyte fuel obtained by inserting the membrane-electrode assembly obtained by the above-described method between a conductive separator material that also serves as a gas supply flow path to the electrode and the electrode chamber separation. A battery is obtained. The membrane-electrode assembly of the present invention uses a pure hydrogen type using hydrogen as a fuel gas, a methanol reforming type using hydrogen obtained by reforming methanol, and hydrogen obtained by reforming natural gas. Natural gas reforming type, gasoline reforming type using hydrogen obtained by reforming gasoline, direct methanol type using methanol directly, etc. can be used as a membrane-electrode assembly for polymer electrolyte fuel cells. is there. In the fuel cell using the electrolyte membrane of the present invention, it is possible to reduce the cell resistance and increase the output under the low humidity condition, and also to reduce the MCO and increase the output in the DMFC.

  Hereinafter, the present invention will be described in more detail with reference to reference examples, examples and comparative examples, performance tests as proton conductive electrolyte membranes for polymer electrolyte fuel cells, and the results thereof. It is not limited. In addition, although the following description is performed in order of the aspect 1, aspect 2, and aspect 3 of this invention, a table | surface is put together collectively at the end.

Reference example 1
Production of block copolymer (SEBS) consisting of polystyrene (polymer block (A)) and hydrogenated polybutadiene (polymer block (B)) In order to form polymer block (A), as an aromatic vinyl compound In order to form the polymer block (B) using styrene, polystyrene-b-polybutadiene-b-polystyrene (hereinafter referred to as SBS) was used in the same manner as the previously reported method (Japanese Patent Laid-Open No. 2005-281373) using butadiene. (Abbreviated) was synthesized. The number average molecular weight of the obtained SBS was 69700, the 1,4-bond content determined from ¹ H-NMR measurement was 60.4%, and the content of styrene units was 39.6% by mass. After preparing a cyclohexane solution of the synthesized SBS and charging it into a pressure-resistant vessel with sufficient nitrogen substitution, a hydrogenation reaction was performed at 50 ° C. for 7 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. To obtain polystyrene-b-hydrogenated polybutadiene-b-polystyrene (hereinafter abbreviated as SEBS). The hydrogenation proportion of the obtained SEBS was calculated by ¹ H-NMR spectrum measurement, it was 99.7%.

Reference example 2
Production of block copolymer consisting of polystyrene (polymer block (A)), hydrogenated polyisoprene (polymer block (B)) and poly (4-tert-butylstyrene) (polymer block (C)) 1000 mL eggplant A flask was charged with 576 ml of dehydrated cyclohexane and 1.6 ml of sec-butyllithium (1.3 M-cyclohexane solution), and then 28.7 ml of 4-tert-butylstyrene, 8.1 ml of styrene, 81.6 ml of isoprene, 8. Poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene-b-polystyrene-b- by sequentially adding 0 ml and 28.3 ml of 4-tert-butylstyrene sequentially and polymerizing at 50 ° C. Poly (4-tert-butylstyrene) (hereinafter tBSSIStBS If the abbreviated there) was synthesized. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 102800, the 1,4-bond content determined from ¹ H-NMR measurement is 93.7%, the content of styrene units is 11% by mass, The content of 4-tert-butylstyrene units was 42% by mass. A cyclohexane solution of synthesized tBSSIStBS was prepared, charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen, and then subjected to a hydrogenation reaction at 60 ° C. for 7 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. Poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter sometimes abbreviated as tBSSEPStBS) Got. The hydrogenation rate of the obtained tBSSEPStBS was calculated by ¹ H-NMR spectrum measurement and found to be 99.9%.

Reference example 3
Production of block copolymer consisting of polystyrene (polymer block (A)), hydrogenated polyisoprene (polymer block (B)) and poly (4-tert-butylstyrene) (polymer block (C)) 1000 mL eggplant A flask was charged with 576 ml of dehydrated cyclohexane and 1.9 ml of sec-butyllithium (1.3M-cyclohexane solution), and then 24.0 ml of 4-tert-butylstyrene, 19.8 ml of styrene, 101 ml of isoprene, 19.7 ml of styrene, TBSSIStBS was synthesized by sequentially adding 23.8 ml of 4-tert-butylstyrene and polymerizing the mixture at 50 ° C. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 102500, the 1,4-bond content determined from ¹ H-NMR measurement is 93.8%, the content of styrene units is 24% by mass, The content of 4-tert-butylstyrene units was 27% by mass. Prepare a synthesized cyclohexane solution of tBSSIStBS, charge it into a pressure vessel fully purged with nitrogen, and then use a Ni / Al Ziegler hydrogenation catalyst for 8 hours at 60 ° C. in a hydrogen atmosphere. To obtain tBSSEPStBS. The hydrogenation rate of the obtained tBSSEPStBS was calculated by ¹ H-NMR spectrum measurement and found to be 99.8%.

Reference example 4
Synthesis of Sulfonated SEBS A sulfonating reagent was prepared by reacting acetic anhydride 76.7 ml and sulfuric acid 34.3 ml at 0 ° C. in 153 ml of methylene chloride. On the other hand, 100 g of SEBS obtained in Reference Example 1 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer and then purged with nitrogen. Then, 960 ml of methylene chloride was added and dissolved by stirring at 35 ° C. for 4 hours. I let you. After dissolution, the sulfonation reagent was gradually added dropwise over 5 minutes. After stirring for 8 hours at 35 ° C., the polymer solution was poured into 2 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes, and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated SEBS. The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated SEBS was 36.1 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 0.96 meq / g.

Reference Example 5
Synthesis of Sulfonated SEBS A sulfonating reagent was prepared by reacting 18.9 ml of acetic anhydride and 8.5 ml of sulfuric acid at 0 ° C. in 37.8 ml of methylene chloride. On the other hand, 100 g of SEBS obtained in Reference Example 1 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer and then purged with nitrogen. Then, 960 ml of methylene chloride was added and dissolved by stirring at 35 ° C. for 4 hours. I let you. After dissolution, the sulfonation reagent was gradually added dropwise over 5 minutes. After stirring at 35 ° C. for 2 hours, the polymer solution was poured into 2 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes, and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated SEBS. The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated SEBS was 17.8 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 0.49 meq / g.

Reference Example 6
Synthesis of Sulfonated tBSSEPStBS 100 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 2 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer, and after replacing with nitrogen, 860 ml of methylene chloride was added. The mixture was stirred at 35 ° C. for 2 hours for dissolution. After dissolution, a sulfonation reagent obtained by reacting 50.7 ml of acetic anhydride and 22.7 ml of sulfuric acid at 0 ° C. in 101 ml of methylene chloride was gradually added dropwise over 5 minutes. After stirring at 35 ° C. for 14 hours, the polymer solution was poured into 1 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The 4-tert-butylstyrene unit of the obtained sulfonated tBSSEPStBS was not sulfonated, and only the styrene unit was sulfonated. The sulfonation rate of the benzene ring in the styrene unit was 100 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 0.97 meq / g.

Reference Example 7
Synthesis of Sulfonated tBSSEPStBS 100 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 3 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer, and after nitrogen substitution, 956 ml of methylene chloride was added, The mixture was stirred at 35 ° C. for 2 hours for dissolution. After dissolution, a sulfonation reagent obtained by reacting 113 ml of acetic anhydride and 50.4 ml of sulfuric acid at 0 ° C. in 226 ml of methylene chloride was gradually added dropwise over 5 minutes. After stirring for 12 hours at 35 ° C., the polymer solution was poured into 1 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The 4-tert-butylstyrene unit of the obtained sulfonated tBSSEPStBS was not sulfonated, and only the styrene unit was sulfonated. The sulfonation rate of the benzene ring in the styrene unit was 100 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.94 meq / g.

Reference Example 8
Synthesis of Sulfonated tBSSEPStBS 100 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 3 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer, and after nitrogen substitution, 956 ml of methylene chloride was added, The mixture was stirred at 35 ° C. for 2 hours for dissolution. After dissolution, a sulfonating reagent obtained by reacting 16.1 ml of acetic anhydride and 7.2 ml of sulfuric acid at 0 ° C. in 32.1 ml of methylene chloride was gradually added dropwise over 5 minutes. After stirring at 35 ° C. for 4 hours, the polymer solution was poured into 1 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The 4-tert-butylstyrene unit of the obtained sulfonated tBSSEPStBS was not sulfonated, and only the styrene unit was sulfonated. The sulfonation rate of the benzene ring in the styrene unit was 19.0 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 0.42 meq / g.

In Embodiment 1 of the present invention including each of the above reference examples, the ion exchange capacity was measured by the following method.
Using the block copolymer obtained in each Reference Example as a sample, the sample was weighed (a (g)) in a glass container capable of being sealed, and an excess amount of a saturated aqueous sodium chloride solution was added thereto and stirred overnight. . Hydrogen chloride generated in the system was titrated (b (ml)) with a 0.01N NaOH standard aqueous solution (titer f) using a phenolphthalein solution as an indicator. The ion exchange capacity was determined by the following formula.
Ion exchange capacity (meq / g) = (0.01 × b × f) / a
The ion exchange capacity of the block copolymer in Embodiments 2 and 3 of the present invention was also measured in the same manner as described above.

Reference Example 9
Preparation of Metal Phosphate SnO ₂ manufactured by Wako Pure Chemical Industries, Al (OH) ₃ manufactured by Wako Pure Chemical Industries, H ₃ PO ₄ manufactured by Wako Pure Chemical Industries, and pure water are mixed in a beaker and heated to about 300 ° C. until a paste is formed And stirred with a stirrer. The obtained paste was transferred to an alumina square sheath and subjected to a solid phase reaction at 650 ° C. for 2.5 hours in an electric furnace. Thereafter, the obtained calcined body was pulverized with a mortar and pestle to obtain Sn _0.95 Al _0.05 P ₂ O ₇ powder. The charge ratio of SnO ₂ and Al (OH) ₃ is 95: 5, and the charge amount of H ₃ PO ₄ is determined by quantifying the cation species and phosphorus by fluorescent X-ray diffractometry (XRF). The molar ratio (P / (Sn + Al)) was adjusted to 2.0.

Reference Example 10
Production of block copolymer consisting of polystyrene (polymer block (A)) and poly (4-tert-butylstyrene) (polymer block (C)) Into a 1000 mL eggplant flask, 448 ml of dehydrated cyclohexane and sec-butyllithium (1 .3M-cyclohexane solution) 2.1 ml was charged, and then 33.4 ml of 4-tert-butylstyrene, 62.3 ml of styrene, and 31.8 ml of 4-tert-butylstyrene were sequentially added and polymerized at 50 ° C., respectively. Thus, poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter abbreviated as tBSStBS) was synthesized. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSStBS is 72000, the content of styrene units determined from ¹ H-NMR measurement is 49% by mass, and the content of 4-tert-butylstyrene units is 51. It was mass%.

Reference Example 11
Synthesis of Sulfonated tBSStBS 100 g of the block copolymer (tBSStBS) obtained in Reference Example 10 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour, and then purged with nitrogen, after which 953 ml of methylene chloride was added, The mixture was stirred at 35 ° C. for 2 hours for dissolution. After dissolution, a sulfonating reagent obtained by reacting 29.3 ml of acetic anhydride and 13.1 ml of sulfuric acid at 0 ° C. in 58.5 ml of methylene chloride was gradually added dropwise over 5 minutes. After stirring at 35 ° C. for 6 hours, the polymer solution was poured into 1 L of distilled water while stirring to coagulate and precipitate the polymer. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSStBS. The 4-tert-butylstyrene unit of the obtained sulfonated tBSStBS was not sulfonated, and only the styrene unit was sulfonated. The sulfonation rate of the benzene ring in the styrene unit was 50.0 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.99 meq / g.

Reference Example 12
Synthesis of Sulfonated Polyether Ether Ketone (S-PEEK) 30 g of polyether ether ketone (Victrex 450P AB7572 manufactured by Victrex) was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer, and then purged with nitrogen. 300 ml of concentrated sulfuric acid was added and reacted at 30 ° C. for 120 hours. After the reaction, the polymer solution was poured into 2 L of ice-cold water with stirring, and the polymer was solidified and precipitated. The precipitated solid was washed with distilled water at 90 ° C. for 30 minutes and then filtered. This washing and filtration operation was repeated until there was no change in the pH of the washing water. Finally, the polymer collected by filtration was vacuum dried to obtain S-PEEK. The sulfonation rate of the obtained S-PEEK was 65.0 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.83 meq / g.

Example 1-1
Preparation of sulfonated SEBS / metal phosphate mixed solution and production of composite membrane 10% by mass of toluene / isobutyl alcohol of sulfonated SEBS (IEC (ion exchange capacity) = 0.96 meq / g) obtained in Reference Example 4 (Mass ratio 8/2) A solution was prepared, and the metal phosphate obtained in Reference Example 9 was added to the solution so that the mass ratio of sulfonated SEBS / metal phosphate was 90/10. The sulfonated SEBS / metal phosphate mixed solution described above was stirred for 30 minutes using a magnetic stirrer, and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the sulfonated SEBS / metal phosphate mixture was applied to a release-treated PET film ["Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd.] The film was coated with a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently dried under vacuum to obtain a film having a thickness of 40 μm. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.44 μm and the mode diameter was 1.36 μm.

Example 1-2
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane The mass ratio of sulfonated SEBS (IEC = 0.96 meq / g) obtained in Reference Example 4 to metal phosphate was 50/50. A film having a thickness of 35 μm was obtained by the same operation as in Example 1-1 except that. As a result of particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.53 μm, and the mode diameter was 1.38 μm.
Example 1-3
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane Using sulfonated SEBS (IEC = 0.49 meq / g) obtained in Reference Example 5, the sulfonated SEBS and metal phosphate were used. A film with a thickness of 30 μm was obtained by the same operation as in Example 1-1 except that the mass ratio of was 50/50. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.24 μm, and the mode diameter was 1.32 μm.

Example 1-4
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane 14% by mass of toluene / isobutyl alcohol (mass ratio 8 /%) of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 2) A solution was prepared, and the metal phosphate obtained in Reference Example 9 was added to this solution so that the mass ratio of sulfonated tBSSEPStBS / metal phosphate was 90/10. The obtained sulfonated tBSSEPStBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the sulfonated SEBS / metal phosphate mixture was coated on the Toyobo Ester Film K1504 to a thickness of about 350 μm and sufficiently dried at room temperature. By sufficiently vacuum drying, a film having a thickness of 32 μm was obtained. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.38 μm, and the mode diameter was 1.32 μm.

Example 1-5
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane Mass ratio of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 to metal phosphate was 80/20 A film having a thickness of 34 μm was obtained by the same operation as in Example 1-1 except that. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.34 μm, and the mode diameter was 1.32 μm.
Example 1-6
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane Mass ratio of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 to metal phosphate was 70/30 A film having a thickness of 35 μm was obtained by the same operation as in Example 1-1 except that. As a result of particle size measurement by static light scattering (LA-950 manufactured by HORIBA was used), the median diameter of the metal phosphate was 3.36 μm, and the mode diameter was 1.32 μm.

Example 1-7
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane Mass ratio of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 and metal phosphate was 50/50 Except for the above, a film having a thickness of 38 μm was obtained by the same operation as in Example 1-1. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.28 μm, and the mode diameter was 1.33 μm.
Example 1-8
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane Mass ratio of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 to metal phosphate was 30/70 Except for the above, a film having a thickness of 36 μm was obtained by the same operation as in Example 1-1. As a result of particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.26 μm, and the mode diameter was 1.27 μm.

Example 1-9
Preparation of Sulfonated tBSSEPStBS / Metal Phosphate Mixed Solution and Preparation of Composite Membrane 12% by mass of toluene / isobutyl alcohol (mass ratio: 7 /%) of sulfonated tBSSEPStBS (IEC = 1.94 meq / g) obtained in Reference Example 7. 3) A solution was prepared, and the metal phosphate obtained in Reference Example 9 was added to this solution so that the mass ratio of sulfonated tBSSEPStBS / metal phosphate was 90/10. The obtained sulfonated tBSSEPStBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the sulfonated SEBS / metal phosphate mixture was coated on the Toyobo Ester Film K1504 to a thickness of about 350 μm and sufficiently dried at room temperature. By sufficiently vacuum drying, a film having a thickness of 34 μm was obtained. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.24 μm, and the mode diameter was 1.31 μm.

Example 1-10
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane Mass ratio of sulfonated tBSSEPStBS (IEC = 1.94 meq / g) obtained in Reference Example 7 and metal phosphate was 50/50 A film having a thickness of 43 μm was obtained by the same operation as in Example 1-1 except that. As a result of particle size measurement by static light scattering (LA-950 manufactured by HORIBA was used), the median diameter of the metal phosphate was 3.25 μm, and the mode diameter was 1.24 μm.

Example 1-11
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane 16% by mass of toluene / isobutyl alcohol (mass ratio 8 / 2) A solution was prepared, and the metal phosphate obtained in Reference Example 9 was added to this solution so that the mass ratio of sulfonated tBSSEPStBS / metal phosphate was 90/10. The obtained sulfonated tBSSEPStBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the sulfonated SEBS / metal phosphate mixture was coated on the Toyobo Ester Film K1504 to a thickness of about 350 μm and sufficiently dried at room temperature. By sufficiently vacuum drying, a film having a thickness of 34 μm was obtained. As a result of particle size measurement by static light scattering (LA-950 manufactured by HORIBA was used), the median diameter of the metal phosphate was 3.42 μm and the mode diameter was 1.31 μm.

Comparative Example 1-1
Preparation of PTFE / metal phosphate composite membrane and preparation of composite membrane The metal phosphate obtained in Reference Example 9 and PTFE (polytetrafluoroethylene) powder (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., Teflon 6-6) J) is kneaded well with a mortar at a ratio of PTFE powder / metal phosphate of 90/10 until it becomes a lump, and rolled using a roller stretcher to obtain a film having a thickness of 30 μm. It was.
Comparative Example 1-2
Preparation of PTFE / metal phosphate composite membrane and preparation of composite membrane A thickness of 30 μm was obtained in the same manner as in Comparative Example 1-1 except that the mass ratio of PTFE powder / metal phosphate was 50/50. A membrane was obtained.
Comparative Example 1-3
Preparation of PTFE / metal phosphate composite membrane and preparation of composite membrane A thickness of 30 μm was obtained in the same manner as in Comparative Example 1-1 except that the mass ratio of PTFE powder / metal phosphate was 30/70. A membrane was obtained.

Comparative Example 1-4
Preparation of SEBS / metal phosphate composite membrane and preparation of composite membrane A 10% by weight toluene / isobutyl alcohol (mass ratio 8/2) solution of SEBS obtained in Reference Example 1 was prepared. The metal phosphate obtained in 9 was added so that the mass ratio of SEBS / metal phosphate was 30/70. The above-mentioned SEBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication eight times, the SEBS / metal phosphate mixed solution was coated on the Toyobo Ester Film K1504 with a thickness of about 350 μm, and sufficiently dried at room temperature. A film having a thickness of 42 μm was obtained by vacuum drying. As a result of particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.68 μm, and the mode diameter was 1.44 μm.

Comparative Example 1-5
Preparation of tBSSEPStBS / metal phosphate composite membrane and preparation of composite membrane A 14% by weight toluene / isobutyl alcohol (mass ratio 8/2) solution of tBSSEPStBS obtained in Reference Example 2 was prepared. The metal phosphate obtained in 9 was added so that the mass ratio of tBSSEPStBS / metal phosphate was 30/70. The obtained tBSSEPStBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and ultrasonic treatment 8 times, a tBS SEPStBS / metal phosphate mixed solution was coated on a Toyobo Ester film K1504 with a thickness of about 350 μm and sufficiently dried at room temperature. A film having a thickness of 35 μm was obtained by vacuum drying. As a result of particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.53 μm, and the mode diameter was 1.41 μm.

Comparative Example 1-6
Sulfonated SEBS of film in Reference Example 4 obtained sulfonated SEBS (IEC = 0.96meq / g) of 10 wt% toluene / isobutyl alcohol (mass ratio 8/2) was prepared, Toyobo ester film above K1504 The film was coated with a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently dried under vacuum to obtain a film having a thickness of 35 μm.
Comparative Example 1-7
Except for using the film obtained in Reference Example 5 sulfonated SEBS sulfonated SEBS (IEC = 0.49meq / g) is the same manner as in Comparative Example 1-8, to obtain a film having a thickness of 30μm .

Comparative Example 1-8
A 14% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 for film formation of sulfonated tBSSEPStBS was prepared on Toyobo Ester Film K1504. The film was coated with a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently dried under vacuum to obtain a film having a thickness of 31 μm.
Comparative Example 1-9
A 12% by mass toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated tBSSEPStBS (IEC = 1.94 meq / g) obtained in Reference Example 7 for film formation of sulfonated tBSSEPStBS was prepared on Toyobo Ester Film K1504. The film was coated with a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently dried under vacuum to obtain a film having a thickness of 29 μm.

Comparative Example 1-10
A 16% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of sulfonated tBSSEPStBS (IEC = 0.42 meq / g) obtained in Reference Example 8 for film formation of sulfonated tBSSEPStBS was prepared on Toyobo Ester Film K1504. The film was coated with a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently dried under vacuum to obtain a film with a thickness of 30 μm.
Comparative Example 1-11
As a perfluorocarbon sulfonic acid polymer electrolyte membrane, a DuPont Nafion film (Nafion 117) was selected.

Comparative Example 1-12
Preparation of sulfonated tBSStBS / metal phosphate mixed solution and production of composite membrane Prepared 15% by weight toluene / isobutyl alcohol (mass ratio 7/3) solution of sulfonated tBSStBS obtained in Reference Example 11. To this solution, the metal phosphate obtained in Reference Example 9 was added so that the mass ratio of sulfonated tBSStBS / metal phosphate was 30/70. The obtained sulfonated tBSStBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication eight times, a sulfonated tBSStBS / metal phosphate mixed solution was coated on Toyobo Ester Film K1504 at a thickness of about 200 μm and sufficiently dried at room temperature. By sufficiently vacuum drying, a film having a thickness of 38 μm was obtained. The produced sulfonated tBSStBS / metal phosphate composite membrane had such a low membrane strength that it was broken when peeled off from the substrate. Since peeling from the substrate was impossible, an electrode was placed on the surface opposite to the substrate while the substrate was attached, and the ionic conductivity was measured by the AC impedance method. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 3.62 μm, and the mode diameter was 1.55 μm.

Comparative Example 1-13
Preparation of Sulfonated tBSStBS / Metal Phosphate-PTFE Composite Membrane The sulfonated tBSStBS / metal phosphate composite electrolyte obtained in Comparative Example 1-12 and PTFE (Teflon 6-J manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) Film formation was attempted by rolling after kneading in a mortar. A film having a thickness of 565 μm was obtained by setting the mass% of PTFE to 23%.

Comparative Example 1-14
Preparation of S-PEEK / metal phosphate mixed solution and preparation of composite membrane A 20% by mass dimethyl sulfoxide solution of S-PEEK obtained in Reference Example 12 was prepared, and this solution was obtained in Reference Example 9. The metal phosphate was added so that the mass ratio of S-PEEK / metal phosphate was 30/70. The obtained S-PEEK / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring the magnetic stirrer and sonication eight times, the S-PEEK / metal phosphate mixture was coated on the Toyobo Ester film K1504 to a thickness of about 200 μm and sufficiently dried at 100 ° C. Thereafter, the film was sufficiently vacuum-dried to obtain a film having a thickness of 60 μm. The produced S-PEEL / metal phosphate composite film had such a low film strength that it was broken when peeled off from the substrate. Since peeling from the substrate was impossible, an electrode was placed on the surface opposite to the substrate while the substrate was attached, and the ionic conductivity was measured by the AC impedance method. As a result of the particle size measurement by static light scattering (using LA-950 manufactured by HORIBA), the median diameter of the metal phosphate was 5.51 μm, and the mode diameter was 6.28 μm.

Comparative Example 1-15
Preparation of S-PEEK / Metal Phosphate-PTFE Composite Membrane S-PEEK / Metal Phosphate Composite Electrolyte obtained in Comparative Example 1-14 and PTFE (Teflon 6-J manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) Film formation was attempted by rolling after kneading in a mortar. A film having a thickness of 2 mm was obtained by setting the mass% of PTFE to 58%.

Performance test of electrolyte membranes of Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-11 as electrolyte membranes for polymer electrolyte fuel cells The electrolyte membrane obtained in each example or comparative example was used.

1) Measurement of ion conductivity of membrane A sample of 1 cm × 4 cm was sandwiched between a pair of platinum electrodes and attached to an open cell. Place the measurement cell in a constant temperature and humidity chamber adjusted to a temperature of 40 ° C or 65 ° C and a relative humidity of 30, 50, 70 or 90%, or in water at a temperature of 40 ° C, and measure the ionic conductivity of the membrane by the AC impedance method. It was measured.
2) Measurement of methanol permeation rate Methanol permeation rate was determined by setting the electrolyte membrane in the center of the H-shaped cell, 55 ml of 3M (mol / liter) aqueous methanol solution on one side of the two spaces, and 55 ml on the other space. Was calculated by measuring the amount of methanol diffusing into the pure water through the electrolyte membrane using gas chromatography while stirring at 25 ° C. (the area of the electrolyte membrane was 4). .5 cm ² ).

3) Production of single cell for polymer electrolyte fuel cell An electrode for a polymer electrolyte fuel cell was produced by the following procedure. A 5% by mass methanol solution of Nafion was added to and mixed with the Pt—Ru alloy catalyst-supporting carbon so that the mass ratio of the Pt—Ru alloy to Nafion was 2: 1 to prepare a uniformly dispersed paste. This paste was applied to a transfer sheet and dried for 24 hours to prepare an anode side catalyst sheet. Also, a 5% by mass solution of Nafion in a mixed solvent of lower alcohol and water was added to and mixed with Pt catalyst-supported carbon so that the mass ratio of Pt catalyst to Nafion was 2: 1, and dispersed uniformly. The prepared paste was prepared, and a cathode side catalyst sheet was prepared in the same manner as the anode side. The electrolyte membrane produced in the first aspect of the present invention is sandwiched between the two types of catalyst sheets so that the membrane and the catalyst surface face each other, and the outside is sandwiched between two heat resistant films and two stainless steel plates in order. The membrane and the catalyst sheet were joined by hot pressing (130 ° C., 1.5 MPa, 8 min). Finally, the stainless steel plate and the heat resistant film were removed, and the transfer sheet was peeled off to produce a membrane-electrode assembly. Next, the membrane-electrode assembly produced was sandwiched between two sheets of carbon paper, the outside was sandwiched between two conductive separators that also function as gas supply channels, and the outside of the two collector plates And an evaluation cell for a polymer electrolyte fuel cell was produced by sandwiching the two clamp plates.

4) Performance evaluation of single cell for fuel cell using hydrogen under low-humidity conditions Solid polymer fuel prepared using the electrolyte membranes obtained in Example 1-7, Example 1-8 and Comparative Example 1-10 The output performance of the single cell for battery was evaluated. Hydrogen was used as the fuel and oxygen was used as the oxidant. The cell temperature was 65 ° C., the bubbler temperature was set so that the gas phase temperature of both hydrogen and oxygen was 40 ° C., and the relative humidity to which the electrolyte membrane was exposed was adjusted to 30%. The test was conducted under the conditions of hydrogen: 250 ml / min and oxygen: 250 ml / min.
5) Performance Evaluation of Single Cell for Fuel Cell Using Methanol Output performance of the single cell for polymer electrolyte fuel cell prepared using the electrolyte membranes obtained in Example 1-10 and Comparative Example 1-11 evaluated. A 3M aqueous methanol solution was used as the fuel, and oxygen was used as the oxidant. The test was conducted at a cell temperature of 40 ° C. under the conditions of MeOH: 1.0 ml / min and oxygen: 174 ml / min.

Results of Performance Test as Polymer Electrolyte Membrane- Ionic Conduction of Electrolyte Membranes Prepared in Examples 1-3 to 1-6, 1-9 and 1-11 and Comparative Examples 1-1 to 1-10 in 40 ° C. Water Degrees in Table 1
Table 2 shows the ionic conductivity of the films produced in Examples 1-1 and 1-2 and Comparative Example 1-8 at 40 ° C. and a relative humidity of 30 to 90%.
-Ionic conductivity at 30-90% relative humidity of 65 ° C relative to membranes prepared in Examples 1-7, 1-8 and 1-10 and Comparative Examples 1-8 and 1-9, and Nafion 117 of Comparative Example 1-11 In Table 3 and FIG.
-Cell temperature of a single cell for a polymer electrolyte fuel cell produced using the membranes produced in Examples 1-7 and 1-8 and Comparative Example 1-8 and Nafion 117 of Comparative Example 1-11, respectively. Table 4 and FIG. 2 show the results of the fuel cell power generation performance test using hydrogen at a relative humidity of 30%.
The methanol permeation rate (μmol / cm ² min of the membranes produced in Examples 1-2, 1-4 to 1-9 and 1-11 and Comparative Examples 1-1 to 1-6 and 1-8 to 1-10 In Table 5
A fuel cell power generation performance test using a 3M methanol aqueous solution at a cell temperature of 40 ° C. for a single cell for a polymer electrolyte fuel cell produced using the membrane produced in each of Examples 1-10 and Comparative Example 1-9 The results are shown in Table 6 and FIG.
The ion conductivity at 65 ° C. and a relative humidity of 30 to 90% of the membranes prepared in Examples 1-8 and 1-10 is 65 ° C. and the relative humidity of 30 of the membranes manufactured in Comparative Examples 1-12 to 1-15. Table 7 and FIG. 4 show the ionic conductivity at ˜90%.
In addition, regarding the evaluated fuel cell performance, the cell resistance at 1.25 A was measured, and the MCO at 5 A was measured.

  In Table 1, from the comparison between Example 1-3 and Comparative Example 1-7, and Example 1-11 and Comparative Example 1-10, 10% by mass of metal phosphate was combined to form an electrolyte membrane. It was confirmed that the ionic conductivity was improved. Further, from comparison between Examples 1-1 and 1-2 and Comparative Example 1-6, Examples 1-4 to 1-6 and Comparative Example 1-8, and Examples 1-9 and Comparative Example 1-9, It was found that when the block copolymer has a large number of ion conductive groups, the ionic conductivity in water does not tend to increase or decrease significantly. On the other hand, PTFE (Comparative Examples 1-1 to 1-3), which is conventionally suitable as a binder, contains 70 mass% or more of metal phosphate in order to express ionic conductivity of 0.01 S / cm or more. It was necessary to add. Moreover, also when the copolymer which does not have an ion conductive group was used, it became the tendency similar to PTFE (Comparative Examples 1-4 and 1-5).

  From Table 2, from the comparison between Examples 1-1 and 1-2 and Comparative Example 1-6, by using the electrolyte membrane obtained from the electrolyte of aspect 1 of the present invention, the ionic conductivity under low humidity conditions is It was confirmed that it could be improved. Moreover, from Table 3, the ion conductivity is increased by increasing the mass ratio of the metal phosphate from 50 mass% to 70 mass% from the comparison between Examples 1-7 and 1-8 and Comparative Example 1-8. Confirmed to improve. The improvement in ionic conductivity is significant when the relative humidity is low, and the comparison between Example 1-10 and Comparative Example 1-11 shows that the electrolyte membrane of aspect 1 of the present invention generally has ionic conductivity under low humidity conditions. It was revealed that the ionic conductivity is higher than that of Nafion 117 (Comparative Example 1-11), which is considered to be excellent in temperature. From the above description, it is clear that the electrolyte of aspect 1 of the present invention can reduce resistance under low humidity conditions.

  From Table 4, with respect to the electrolyte membrane obtained in Comparative Example 1-8, the electrolyte membranes obtained in Examples 1-7 and 1-8 were used in fuel cell power generation using hydrogen under low humidity conditions. It is clear that the metal phosphate compensates for the ionic conductivity of the electrolyte membrane, so that the cell resistance is reduced and the maximum power density is improved. From the above description, it has been clarified that the power generation performance of a fuel cell that operates using hydrogen as a fuel under low humidity conditions can be improved by using the electrolyte membrane obtained from the electrolyte of aspect 1 of the present invention. In addition, when the single cell after the power generation test was disassembled, the membrane-electrode assembly using the electrolyte membrane obtained by using the electrolyte according to aspect 1 of the present invention did not show any peeling or the like, and had excellent bondability. It became clear that.

  In Table 5, Example 1-2 and Comparative Example 1-6, Examples 1-4 to 1-8, Comparative Example 1-8, Example 1-9, Comparative Example 1-9, and Example 1-11 From the comparison with Comparative Example 1-10, there was no significant increase in methanol permeation rate (MCO) due to complexation with metal phosphate. In addition, from the comparison between Example 1-2 and Comparative Example 1-6 in Table 2, and the comparison between Examples 1-7 and 1-8 and Comparative Example 1-8 in Table 3, the metal phosphate and Since the ionic conductivity under low humidity conditions is improved by the composite, the electrolyte of aspect 1 of the present invention improves the ionic conductivity under low humidity conditions while maintaining the same MCO value. It was found that it can be made. On the other hand, in Comparative Examples 1-1 and 1-2 using PTFE, which is considered to be suitable as a conventional binder, the MCO has a large value (Table 5) despite the low ionic conductivity (Table 1). ). Regarding Comparative Example 1-1, although the MCO value is small (Table 5), the ionic conductivity is remarkably lower than those of Examples 1-11 and Comparative Examples 1-10, which have comparable MCO values (Table 1). ), Does not exhibit sufficient function as an electrolyte membrane. In addition, SEBS and tBSSEPEtBS (Comparative Examples 1-4 and 1-5) having no ion conductive group showed the same tendency (Tables 1 and 5), but formed a dense electrolyte membrane as compared with PTFE. Therefore, even when it had the metal phosphate of the same mass ratio, MCO became low (Comparison with Comparative Examples 1-4 and 1-5 in Table 5 and Comparative Example 1-3). In addition, from the comparison between Example 1-8 and Comparative Example 1-5, even if the metal phosphate mass ratio is the same, the copolymer has an ion conductive group, so that Since an interaction such as hydrogen bonding is expressed between the phosphate group and the ion conductive group of the copolymer, a denser electrolyte membrane can be formed and the MCO is reduced (Table 5). From the above description, it is clear that the electrolyte membrane of aspect 1 of the present invention can achieve both high ionic conductivity under low humidity conditions and MCO suppression.

  From Table 6, by comparing Example 1-10 with Comparative Example 1-9, the electrolyte membrane obtained from the electrolyte of aspect 1 of the present invention maintains the cell resistance at the same time during DMFC power generation, and has an MCO. It is clear that the maximum power density can be improved. In MCO reduction, the metal phosphate in the electrolyte membrane is also responsible for proton conduction, so the electroosmosis phenomenon that occurs when proton conduction through water occurs in conventional polymer electrolyte membranes can be suppressed. It is understood that this is an effect obtained by reducing the amount of methanol dragged by the moving water. In addition to the reduction in MCO, the increase in the maximum power density is attributed to the suppression of the above-described electroosmosis phenomenon, which suppresses the flooding phenomenon that inhibits the oxygen diffusion of the cathode and consequently reduces the output. It is understood. Further, when the single cell after the power generation test was disassembled, the membrane-electrode assembly using the electrolyte membrane obtained by using the electrolyte of aspect 1 of the present invention did not show any peeling and excellent bonding properties. It became clear that.

    In Table 7, from the comparison between Example 1-8 and Comparative Examples 1-12 and 1-14, when the mass ratio of the metal phosphate was the same, despite the low ion exchange capacity of the polymer It was confirmed that the composite membrane of Example 1-8 had high ionic conductivity under low humidity conditions. Further, from the comparison between Example 1-10 and Comparative Examples 1-12 and 1-14, when the ion exchange capacity of the polymer was the same, it was wide although the mass% of the metal phosphate was low. It was confirmed that the ionic conductivity of the composite membrane of Example 1-10 was high in the humidity range. In addition to increasing the film strength by having a flexible phase that does not have an ion conductive group, it is possible to obtain a composite film that is dense without cracks and voids and in which metal phosphates are uniformly dispersed. is there. In Comparative Examples 1-13 and 1-15, PTFE was added to obtain a free-standing film, and the ionic conductivity was greatly reduced. Therefore, a dense and high-strength free-standing film without the need for a binder was obtained. It was revealed that the obtained electrolyte of the present invention and the electrolyte membrane are useful.

Example 2-1
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane-1
A 10% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated SEBS (ion exchange capacity = 0.96 meq / g) obtained in Reference Example 4 was prepared, and this solution was obtained in Reference Example 9. The resulting metal phosphate was added so that the mass ratio of sulfonated SEBS / metal phosphate was 10/90. The above sulfonated SEBS / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer, and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and ultrasonic treatment four times, the sulfonated SEBS / metal phosphate mixed solution was subjected to a release-treated PET film ["Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd .; The film was obtained by sufficiently drying at room temperature and then vacuum drying. As a result of particle size measurement (particle size measurement by static light scattering, LA-950 made by HORIBA; the same applies hereinafter), the median diameter of the metal phosphate was 3.44 μm and the mode diameter was 1.36 μm.

Example 2-2
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane-2
A membrane was obtained by the same operation as in Example 2-1, except that the mass ratio of sulfonated SEBS / metal phosphate was 20/80. As a result of the particle size measurement, the median diameter of the metal phosphate was 3.53 μm, and the mode diameter was 1.38 μm.
Example 2-3
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane-3
A membrane was obtained by the same operation as in Example 2-1, except that the mass ratio of sulfonated SEBS / metal phosphate was 30/70. As a result of the particle size measurement, the median diameter of the metal phosphate was 3.24 μm, and the mode diameter was 1.32 μm.

Example 2-4
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane-4
A membrane was obtained by the same operation as in Example 2-1, except that the mass ratio of sulfonated SEBS / metal phosphate was 50/50. As a result of the particle size measurement, the median diameter of the metal phosphate was 3.26 μm, and the mode diameter was 1.27 μm.
Example 2-5
Preparation of sulfonated SEBS / metal phosphate mixed solution and preparation of composite membrane-5
A membrane was obtained in the same manner as in Example 2-1, except that the mass ratio of sulfonated SEBS / metal phosphate was 75/25. As a result of the particle size measurement, the median diameter of the metal phosphate was 3.38 μm, and the mode diameter was 1.32 μm.

Comparative Example 2-1
Preparation of PTFE / metal phosphate composite membrane-1
The metal phosphate obtained in Reference Example 9 and PTFE powder (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., Teflon 6-J) were used at a ratio where the mass ratio of PTFE powder / metal phosphate was 10/90. It kneaded well until it became a lump using a mortar, and it rolled using the roller stretcher, and obtained the film | membrane.
Comparative Example 2-2
Preparation of PTFE / metal phosphate composite membrane-2
A membrane was obtained by the same operation as in Comparative Example 2-1, except that the mass ratio of PTFE powder / metal phosphate was 20/80.

Comparative Example 2-3
Preparation of PTFE / metal phosphate composite membrane-3
A membrane was obtained by the same operation as in Comparative Example 2-1, except that the mass ratio of PTFE powder / metal phosphate was 30/70.
Comparative Example 2-4
Preparation of PTFE / metal phosphate composite membrane -4
A membrane was obtained by the same operation as in Comparative Example 2-1, except that the mass ratio of PTFE powder / metal phosphate was 50/50.
Comparative Example 2-5
Preparation of PTFE / metal phosphate composite membrane-5
A membrane was obtained in the same manner as in Comparative Example 2-1, except that the mass ratio of PTFE powder / metal phosphate was 75/25.

Comparative Example 2-6
Preparation of PTFE film PTFE powder was well kneaded into a lump using a mortar and rolled using a roller stretcher to obtain a film.
Comparative Example 2-7
Sulfonated SEBS of film in Reference Example 4 obtained sulfonated SEBS (ion exchange capacity = 0.96meq / g) 10 wt% toluene / isobutyl alcohol (mass ratio 8/2) was prepared and releasing process The coated film was coated on a used PET film, sufficiently dried at room temperature, and then sufficiently vacuum dried to obtain a film.

Performance Test of Membranes Obtained in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-7 as an Electrolyte Membrane for a Polymer Electrolyte Fuel Cell In the following tests, a sample is an aspect of the present invention. The electrolyte membrane obtained in each Example 2 or Comparative Example 2 was used.
1) Measurement of film strength For the films obtained in Examples 2-1 to 2-5 and Comparative Examples 2-1, 2-2, 2-4 to 2-7, the sample was formed into a dumbbell shape, Tensile strength and elongation at break were measured under conditions of a tensile speed of 500 mm / min.
2) Measurement of ion conductivity of membrane Regarding the membranes obtained in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 and 2-7, a sample of 1 cm × 4 cm was paired with a pair of platinum electrodes. The membrane was attached to an open cell, and the ionic conductivity of the membrane was measured by the AC impedance method under a non-humidified condition at 150 ° C.

3) Manufacture of a single cell for a polymer electrolyte fuel cell The present invention except that the single cell as an evaluation cell for a polymer electrolyte fuel cell is the electrolyte membrane prepared in the above-described aspect 2 of the present invention as an electrolyte membrane. It was produced in the same manner as the production of the single cell for the polymer electrolyte fuel cell in Embodiment 1.
4) Measurement of open circuit voltage (OCV) under non-humidified conditions at 150 ° C. and membrane resistance A fuel cell single cell was assembled using the electrolyte membranes obtained in Example 2-2 and Comparative Example 2-2. The film thickness dependence of OCV and film resistance under the condition of 0 ° C. and no humidification was measured. The OCV measurement was performed under the conditions of hydrogen: 250 ml / min and oxygen: 250 ml / min.

As a result of the performance test as a polymer electrolyte membrane, the tensile strength and elongation at break of the membranes produced in Examples 2-1 to 2-5 and Comparative Examples 2-1, 2-2, 2-4 to 2-7 are shown. In Table 8,
Table 9 and FIG. 5 show the ionic conductivity of the films prepared in Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 and 2-7 at 150 ° C. and no humidification.
Table 10 and FIG. 6 show the film thickness dependence of the open circuit voltage (OCV) and the film resistance value of the films prepared in Example 2-2 and Comparative Example 2-2 at 150 ° C. and no humidification, respectively. Show.

  In Table 8, a composite using PTFE, which is considered to be suitable as a conventional binder from the comparison between Examples 2-1 to 2-5 and Comparative Examples 2-1, 2-2, 2-4 to 2-7 As compared with the membrane, it is clear that the composite electrolyte membrane of aspect 2 of the present invention has high tensile strength and elongation at break in a wide range of metal phosphate mass ratios.

In Table 9, from the comparison between Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5, the composite membrane of aspect 2 of the present invention is a polymer block (A) containing an ion conductive group. Since the ion channel formed from the above compensates ionic conduction between the metal phosphates even at 150 ° C. and without humidification, the metal phosphate mass ratio is particularly 70 as compared with the composite membrane using PTFE as a binder. When it was less than%, high ionic conductivity was exhibited. Also from the membrane strength shown in Table 8, it was clarified that the composite electrolyte membrane of aspect 2 of the present invention can achieve both membrane strength and ionic conductivity and is excellent as an electrolyte membrane for fuel cells.

  In Table 10, from the comparison between Example 2-2 and Comparative Example 2-2, the composite electrolyte membrane of aspect 2 of the present invention contains an ion conductive group in addition to excellent membrane strength and excellent moldability. Since ion conduction between metal phosphates can be compensated by ion channels formed from the polymer block (A), pinholes, defects, cracks, etc. do not occur even when the electrolyte membrane thickness is reduced. As a result, the open circuit voltage (OCV) was maintained high even when the film thickness was small. In addition, the film resistance could be reduced by reducing the film thickness. Therefore, the composite electrolyte membrane of aspect 2 of the present invention is an excellent electrolyte membrane that can maintain a high cell voltage and has low resistance, and the fuel cell using the electrolyte membrane of aspect 2 of the present invention achieves high output. Obviously it can.

Reference Example 13
Preparation of metal phosphate-2 ( Synthesis of Sn _0.95 Al _0.05 P ₂ O ₇ powder using SnO ₂ manufactured by Nanotech )
Sn _0.95 Al _0.05 P ₂ O ₇ powder was obtained in the same manner as in Reference Example 9 except that Nanotech SnO ₂ was used.

Example 3-1
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane-1
A 14% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated tBSSEPStBS (IEC (ion exchange capacity) = 0.97 meq / g) obtained in Reference Example 6 was prepared. The metal phosphate obtained in 13 was added so that the mass ratio of sulfonated tBSSEPStBS / metal phosphate was 50/50. The sulfonated tBSSEPStBS / metal phosphate mixed solution described above was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and ultrasonic treatment four times, the sulfonated tBSSEPStBS / metal phosphate mixed solution was subjected to a release-treated PET film ["Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd .; The film was coated to a thickness of about 350 μm, sufficiently dried at room temperature, and then sufficiently vacuum-dried to obtain a film having a thickness of 30 μm. The obtained electrolyte membrane was put in toluene / isobutyl alcohol (mass ratio 8/2) to dissolve sulfonated tBSSEPStBS, and particle size measurement by static light scattering (LA-950 made by HORIBA) was performed using the resulting suspension. When used, the same applies hereinafter), the median diameter of the metal phosphate was 92 nm, and the mode diameter was 85 nm.

Example 3-2
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane-2
A 12% by mass toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated tBSSEPStBS (IEC = 1.94 meq / g) obtained in Reference Example 7 was prepared, and this solution was obtained in Reference Example 13. The metal phosphate was added so that the mass ratio of sulfonated tBSSEPStBS / metal phosphate was 50/50. The sulfonated tBSSEPStBS / metal phosphate mixed solution described above was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the sulfonated tBSSEPStBS / metal phosphate mixed solution was coated on the release-treated PET film to a thickness of about 350 μm and allowed to dry sufficiently at room temperature. After that, the film was sufficiently vacuum-dried to obtain a film having a thickness of 34 μm. The obtained electrolyte membrane was put in toluene / isobutyl alcohol (mass ratio 7/3) to dissolve sulfonated tBSSEPStBS, and the particle size was measured by static light scattering using the resulting suspension. The median diameter of the phosphate was 71 nm, and the mode diameter was 69 nm.

Example 1-12
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane-3
A film having a thickness of 38 μm was obtained in the same manner as in Example 3-1, except that the metal phosphate obtained in Reference Example 9 was used. The obtained electrolyte membrane was put in toluene / isobutyl alcohol (mass ratio 8/2) to dissolve sulfonated tBSSEPStBS, and the particle size was measured by static light scattering using the resulting suspension. The median diameter of the phosphate was 3.26 μm, and the mode diameter was 1.27 μm.
Example 1-13
Preparation of sulfonated tBSSEPStBS / metal phosphate mixed solution and preparation of composite membrane-4
A film having a thickness of 34 μm was obtained in the same manner as in Example 3-2 except that the metal phosphate obtained in Reference Example 9 was used. The obtained electrolyte membrane was put in toluene / isobutyl alcohol (mass ratio 7/3) to dissolve sulfonated tBSSEPStBS, and the particle size was measured by static light scattering using the resulting suspension. The median diameter of the phosphate was 3.24 μm, and the mode diameter was 1.31 μm.

Comparative Example 3-1
Film formation-1 of sulfonated tBSSEPStBS
A 14% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated tBSSEPStBS (IEC = 0.97 meq / g) obtained in Reference Example 6 was prepared, and about 350 μm of the release-treated PET film was prepared. The film was coated with a thickness, sufficiently dried at room temperature, and then sufficiently vacuum-dried to obtain a film having a thickness of 31 μm.
Comparative Example 3-2
Film formation of sulfonated tBSSEPStBS-2
A 12% by mass toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated tBSSEPStBS (IEC = 1.94 meq / g) obtained in Reference Example 7 was prepared, and about 350 μm of the release-treated PET film was prepared. The film was coated with a thickness, sufficiently dried at room temperature, and then sufficiently vacuum-dried to obtain a film having a thickness of 29 μm.

Comparative Example 3-3
Preparation of Nafion / metal phosphate mixed solution and preparation of composite membrane-1
To the dispersion of Nafion manufactured by DuPont, the metal phosphate obtained in Reference Example 9 was added so that the mass ratio of Nafion / metal phosphate was 50/50. The obtained Nafion / metal phosphate mixed solution was stirred for 30 minutes using a magnetic stirrer and subjected to ultrasonic treatment for 30 minutes. After stirring with a magnetic stirrer and sonication four times, the Nafion / metal phosphate mixture was coated on the release-treated PET film to a thickness of about 350 μm and sufficiently dried at room temperature. Although it was sufficiently vacuum-dried, many cracks were generated and a self-supporting film could not be obtained. In addition, when the particle size measurement by static light scattering was performed using the Nafion / metal phosphate mixed solution, the median diameter of the metal phosphate was 3.14 μm and the mode diameter was 1.41 μm.

Comparative Example 3-4
Preparation of Nafion / metal phosphate mixed solution and preparation of composite membrane-2
Except for using the metal phosphate obtained in Reference Example 13, an attempt was made to produce a composite film by the same operation as in Comparative Example 3-3, but many cracks occurred and a self-supporting film could not be obtained. . In addition, when the particle size measurement by static light scattering was performed using the Nafion / metal phosphate mixed solution, the median diameter of the metal phosphate was 75 nm and the mode diameter was 71 nm.

Performance tests of the electrolyte membranes of Examples 3-1 and 3-2 and Examples 1-12 to 1-13 and Comparative Examples 3-1 to 3-2 as electrolyte membranes for polymer electrolyte fuel cells In the following tests The sample used was the electrolyte membrane obtained in each example or comparative example of aspect 3 of the present invention.

1) Measurement of phosphoric acid elution amount from membrane The electrolyte membrane 0.1 g produced in Example 3-2 and Example 1-13 was immersed in distilled water of 50 ml and 80 ° C. for 24 hours. Phosphate ions in the liquid in which the electrolyte membrane was immersed were quantified by ion chromatography (DX-320, DIONEX).
2) Measurement of ion conductivity of membrane A sample of 1 cm × 4 cm was sandwiched between a pair of platinum electrodes and attached to an open cell. The measurement cell was installed in a constant temperature and humidity chamber adjusted to a temperature of 65 ° C. and a relative humidity of 30, 50, 70, or 90%, and the ionic conductivity of the membrane was measured by an AC impedance method.
3) Measurement of methanol permeation rate Methanol permeation rate was determined by placing the electrolyte membrane in the center of the H-shaped cell, 55 ml of 3M (mol / liter) aqueous methanol solution on one side of the two spaces, and 55 ml on the other space. Was calculated by measuring the amount of methanol diffusing through the electrolyte membrane into the pure water using gas chromatography while stirring at 25 ° C. (area of the electrolyte membrane: 4. 5 cm ² ).

4) Manufacture of a single cell for a polymer electrolyte fuel cell The present invention except that the single cell as an evaluation cell for a polymer electrolyte fuel cell is the electrolyte membrane prepared in the third aspect of the present invention as an electrolyte membrane. It was produced in the same manner as the production of the single cell for the polymer electrolyte fuel cell in Embodiment 1.
5) Performance evaluation of single cell for fuel cell using hydrogen under low humidity conditions Solid polymer type prepared using the electrolyte membranes obtained in Example 3-1, Example 1-12 and Comparative Example 3-1, respectively. The output performance of the single cell for fuel cell was evaluated. Hydrogen was used as the fuel and oxygen was used as the oxidant. The cell temperature was 65 ° C., the bubbler temperature was set so that the gas phase temperature for both hydrogen and oxygen was 40 ° C., and the relative humidity to which the electrolyte membrane was exposed was adjusted to 30%. The test was conducted under the conditions of hydrogen: 250 ml / min and oxygen: 250 ml / min.
6) Performance evaluation of single cell for fuel cell using methanol Single unit for polymer electrolyte fuel cell produced using electrolyte membrane obtained in Example 3-2, Example 1-13 and Comparative Example 3-2 The output performance of the cell was evaluated. A 3M aqueous methanol solution was used as the fuel, and oxygen was used as the oxidant. The test was conducted at a cell temperature of 40 ° C. under the conditions of MeOH: 1.0 ml / min and oxygen: 174 ml / min.

As a result of the performance test as a polymer electrolyte membrane- Example 3-2 The phosphate elution amount of the electrolyte membrane produced in Example 1-13 is shown in Table 11.
Table 12 shows the ionic conductivity of the electrolyte membranes prepared in Example 3-2, Example 1-13, and Comparative Example 3-2 at 65 ° C. and 30 to 90% relative humidity.
Table 13 shows the methanol permeation rate (converted to μmol / cm ² min) of the electrolyte membranes prepared in Example 3-2, Example 1-13, and Comparative Example 3-2.
-A single cell for a polymer electrolyte fuel cell produced using the electrolyte membrane produced in Example 3-1, Example 1-12 and Comparative Example 3-1, respectively, at a cell temperature of 65 ° C and a relative humidity of 30%. Table 14 and FIG. 7 show the results of the fuel cell power generation performance test using hydrogen of
A 3M methanol aqueous solution at a cell temperature of 40 ° C. of a single cell for a polymer electrolyte fuel cell produced using the membrane produced in Example 3-2, Example 1-13 and Comparative Example 3-2, respectively. The results of the fuel cell power generation performance test are shown in Table 15 and FIG.
In addition, regarding the evaluated fuel cell performance, the cell resistance at 1.25 A was measured, and the MCO at 5 A was measured.

  In Table 11, from the comparison between Example 3-2 and Example 1-13, when the same mass% of metal phosphate was combined, the particle size of the metal phosphate (measured by static light scattering) It was confirmed that the elution amount of phosphoric acid was reduced by reducing the median diameter from 3.24 μm to 71 nm. When the particle size of the metal phosphate is reduced, the area in contact with the ion conductive group site of the block copolymer increases, the composite membrane becomes dense, and the ion conductive group of the metal phosphate and the block copolymer is increased. It is presumed that a hydrogen bond is formed between the phosphoric acid and the phosphoric acid.

  From the comparison between Example 3-2, Example 1-13 and Comparative Example 3-2 in Table 12, the effect of improving the ionic conductivity due to the use of the metal phosphate is obtained when the metal phosphate is reduced in particle size. However, it can be said that the same level is maintained.

  From the comparison between Example 3-2, Example 1-13, and Comparative Example 3-2 in Table 13, it is clear that methanol crossover is reduced by reducing the particle size of the metal phosphate. This is presumably because a hydrogen bond was formed between the ion conductive group of the block copolymer and the metal phosphate, and the composite membrane became dense.

  From the comparison between Example 3-1 and Example 1-12 and Comparative Example 3-1 in Table 14, the effect of reducing cell resistance under low humidity conditions is increased by reducing the particle size of the metal phosphate. It is clear that the power density is improved. Further, when the single cell after the power generation test was disassembled, no peeling or the like was observed in the membrane-electrode assembly using the electrolyte membrane obtained by using the electrolyte of aspect 3 of the present invention. It became clear that the bondability was also excellent.

  From the comparison between Example 3-2, Example 1-13 and Comparative Example 3-2 in Table 15, by reducing the particle size of the metal phosphate, the methanol resistance during power generation is maintained while maintaining the same cell resistance. It is clear that over (MCO) is reduced and maximum power density is improved. The reduction in MCO can suppress the electroosmosis phenomenon that occurs when proton conduction through water occurs in the conventional polymer electrolyte membrane because the metal phosphate in the electrolyte membrane is also responsible for proton conduction. It is estimated that this is an effect obtained by reducing the amount of methanol dragged by the moving water. In addition to the reduction in MCO, the increase in the maximum power density is attributed to the suppression of the above-described electroosmosis phenomenon, which suppresses the flooding phenomenon that inhibits the oxygen diffusion of the cathode and consequently reduces the output. Presumed. Since the above-described effects are further manifested by reducing the particle size of the metal phosphate, the DMFC power generation performance is improved. In addition, when the single cell after the power generation test was disassembled, no peeling or the like was observed in the membrane-electrode assembly using the electrolyte membrane obtained by using the electrolyte of aspect 3 of the present invention. It became clear that it was excellent also in the property.

It is a figure which shows the ionic conductivity in low humidity conditions of the electrolyte membrane of aspect 1 of this invention (Examples 1-7, 1-8, and 1-10, and Comparative Examples 1-8, 1-9, and 1-11) ). It is a figure which shows the electric current-cell voltage of the single cell for fuel cells of the aspect 1 of this invention which used hydrogen adjusted so that the environment which a membrane-electrode assembly is exposed to 65 degreeC relative humidity 30% was used as a fuel. (Examples 1-7 and 1-8, and Comparative Examples 1-8 and 1-11). It is a figure which shows the electric current-power density of the fuel cell single cell of the aspect 1 of this invention which used cell temperature as 40 degreeC, used 3M methanol aqueous solution as a fuel, and oxygen as an oxidizing agent (Example 1-10 and Comparative Example 1-9). It is a figure which shows the ionic conductivity in 40 degreeC and 30-90% of relative humidity of the electrolyte membrane of aspect 1 of this invention (Example 1-8, Example 1-10, and Comparative Examples 1-12 to 1-15) ).

The ion conductivity in 150 degreeC and non-humidification conditions, and the metal phosphate mass ratio (= metal phosphate / (block copolymer or PTFE) mass ratio) contained in the electrolyte membrane of the aspect 2 of this invention It is a figure which shows a relationship (Examples 2-1 to 2-5, and Comparative Examples 2-1 to 2-5, and 2-7). It is a figure which shows the relationship between the open circuit voltage (OCV) in 150 degreeC and non-humidification conditions, and membrane resistance, and the electrolyte membrane film thickness of the aspect 2 of this invention (Example 2-2 and Comparative Example 2-2). ). Current of the single cell for a fuel cell according to the third aspect of the present invention using hydrogen adjusted as an environment in which the membrane-electrode assembly is exposed to 65 ° C. and a relative humidity of 30%, and oxygen as an oxidant— It is a figure which shows a cell voltage (Example 3-1, Example 1-12, and Comparative Example 3-1). It is a figure which shows the electric current-power density of the fuel cell single cell of aspect 3 of this invention which used cell temperature as 40 degreeC, 3M methanol aqueous solution as a fuel, and oxygen as an oxidizing agent (Example 3-2, Example 1-13 and Comparative Example 3-2).

Claims (16)

  A block copolymer comprising polymer blocks (A) and (B) that are phase-separated from each other, wherein the polymer block (A) has an ion conductive group and the polymer block (B) is flexible. An electrolyte comprising a composition comprising a block copolymer which forms a phase and the ion conductive group is substantially present only in the polymer block (A), and a metal phosphate having ion conductivity.   The electrolyte according to claim 1, wherein the mass ratio of the block copolymer / the metal phosphate is 99/1 to 30/70.   The electrolyte according to claim 1, wherein the mass ratio of the block copolymer / the metal phosphate is 80/20 to 1/99.   The electrolyte according to claim 1, wherein the metal phosphate has an average particle size of 10 nm to 1 μm.   The electrolyte according to claim 4, wherein a mass ratio of the block copolymer / the metal phosphate is 99/1 to 30/70.   A metal phosphate having ionic conductivity is M (wherein M is at least one element selected from the group consisting of Group 4 and Group 14 elements of the Long Periodic Table), P and A compound containing O, wherein a part of M is a doping element J (where J is a group consisting of elements of Group 3, Group 13, Group 5 and Group 15 of the long-period periodic table) 2. The electrolyte according to claim 1, which is a compound substituted with at least one selected element. A metal phosphate having ionic conductivity is substantially of formula (1)
M _1-x J _x P ₂ O ₇ (1)
(Wherein M is at least one element selected from the group consisting of Sn, Ti, Si, Ge, Pb, Zr and Hf, J is at least one element selected from Al and In, and x Represents an integer of 0.001 to 0.5).   In the composition ratio of the formula (1), that is, the molar ratio of M: J: P: O (1-x): x: 2: 7, the ratios of P and O are 2 and 7 within 10%, respectively. The electrolyte according to claim 7, wherein the electrolyte is increased or decreased.   The electrolyte according to claim 1, wherein the block copolymer is a vinyl block copolymer.   The polymer block (A) is an aromatic vinyl polymer block (Aa), the polymer block (B) is a vinyl polymer block (Ba) forming a flexible phase, and the vinyl polymer block ( Ba) is an alkene unit having 2 to 8 carbon atoms, a cycloalkene unit having 5 to 8 carbon atoms, a vinylcycloalkene unit having 7 to 10 carbon atoms, a conjugated alkadiene unit having 4 to 8 carbon atoms, and a conjugate having 5 to 8 carbon atoms. A cycloalkadiene unit, a vinylcycloalkene unit having 7 to 10 carbon atoms in which some or all of the carbon-carbon double bonds are hydrogenated, a conjugated alkadiene unit having 4 to 8 carbon atoms, and a conjugate having 5 to 8 carbon atoms 10. The electrolyte according to claim 9, which is a polymer block having at least one unit selected from the group consisting of cycloalkadiene units as a main repeating unit.   The block copolymer is a polymer block which is different from the polymer block (A) and the polymer block (B), and phase-separates from these and has substantially no ion conductive group, The electrolyte according to claim 1, comprising a polymer block (C) functioning as a further constituent component. The polymer block (C) is represented by the following general formula (II)

(In the formula, R ^{2 to} R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, but at least one is an alkyl group having 1 to 8 carbon atoms, and R ⁵ is a hydrogen atom or carbon. 12. The electrolyte according to claim 11, which is a polymer block having a main repeating unit of at least one unit selected from aromatic vinyl compound units represented by formula (1-4). Ion-conducting group is _-SO 3 M, (wherein, M represents a hydrogen atom, an ammonium ion or an alkali metal ion) -COOM or _-PO 3 HM electrolyte according to claim 1, wherein the group represented by.   The electrolyte membrane for fuel cells which consists of an electrolyte of any one of Claims 1-13.   A membrane-electrode assembly using the electrolyte membrane according to claim 14. A polymer electrolyte fuel cell using the membrane-electrode assembly according to claim 15.

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