JP4437663B2 - Proton conducting polymer electrolyte, proton conducting polymer electrolyte membrane and membrane-electrode assembly, and solid polymer fuel cell - Google Patents

Description

  The present invention relates to a proton conductive polymer electrolyte, a proton conductive polymer electrolyte membrane and a membrane-electrode assembly, and a solid polymer fuel cell.

  Polymer compounds containing proton conductive substituents such as sulfonic acid groups are used as raw materials for electrochemical devices such as solid polymer fuel cells, humidity sensors, gas sensors, and electrochromic display devices. Among these, the polymer electrolyte fuel cell is expected as one of the pillars of new energy technology. A polymer electrolyte fuel cell that uses an electrolyte membrane made of a polymer compound having a proton-conducting substituent can be operated at low temperatures and can be reduced in size and weight. , And application to small portable devices for consumer use. In particular, direct methanol fuel cells that use methanol directly as fuel have a simple structure, ease of fuel supply and maintenance, and high energy density. It is expected to be applied to consumer portable devices such as laptop computers and notebook computers.

  As a proton conductive electrolyte membrane used in a polymer electrolyte fuel cell, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. The perfluorocarbon sulfonic acid membrane has high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, since the raw materials used are high and the manufacturing process is complicated, there is a disadvantage that it is very expensive. Furthermore, permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol is large, and a so-called chemical short reaction occurs. As a result, the cathode potential, fuel efficiency, cell characteristics and the like are lowered, and it is difficult to directly use as an electrolyte membrane of a methanol fuel cell. Moreover, there is a concern that fuel may be lost due to crossover even when power is not generated.

  Against this background, various proton-conductive polymer electrolyte membranes have been proposed.

  For example, Patent Document 1 proposes a sulfonic acid group-containing polyphenylene sulfide that is soluble in an aprotic polar solvent. It is disclosed that by introducing a sulfonic acid group in a solution of polyphenylene sulfide in a chlorosulfonic acid homogeneous solution, solubility in an aprotic polar solvent can be imparted and the film can be easily processed into a film. However, in the method disclosed herein, there is a possibility that solubility in methanol, which is considered as a fuel for fuel cells, may be imparted at the same time, and the range of use thereof is significantly limited. Further, since chlorosulfonic acid is used as a solvent and a sulfonating agent, it may be difficult to control the amount of sulfonic acid group introduced, or the polyphenylene sulfide may be deteriorated. Further, a large amount of acid waste liquid is discharged during reaction, resin recovery, and washing. Further, there is no mention of the effect of suppressing permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol.

  Patent Document 2 discloses a method for producing a proton conductive polymer membrane made of sulfonic acid group-containing polyphenylene sulfide. According to this method, an electrolyte membrane composed of a solvent-insoluble sulfonic acid group-containing polyphenylene sulfide can be obtained, but there is no mention of the effect of suppressing permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol.

  For example, Patent Document 3 discloses a polymer electrolyte membrane in which a polymer porous support is filled with an electrolyte monomer to increase the molecular weight. In order to suppress swelling with respect to methanol and water used as fuel by the porous support, it is said that permeation (crossover) thereof is suppressed. However, since the manufacturing process is complicated, there is a problem in terms of manufacturing cost. In addition, in order to develop sufficient proton conductivity, it is necessary to set the content of the proton conductive substituent in the electrolyte part to be high, and durability in this part and durability of the electrolyte / support interface are required. There are concerns.

Patent Document 4 discloses an electrolyte membrane comprising a fluorinated polymer having a sulfonic acid group and a fibrillar fluorocarbon polymer. These are said to improve the durability of the electrolyte membrane, but do not mention the effect of suppressing permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol.
Japanese National Patent Publication No. 11-510198 International Publication No. 02/062896 Pamphlet Republished WO00 / 54531 JP 2003-51220 A

  The object of the present invention has been made in view of the above problems, and is useful as a constituent material of a polymer electrolyte fuel cell or a direct methanol fuel cell, and has excellent proton conductivity and high proton barrier property. It is to provide a conductive polymer electrolyte and a proton conductive polymer electrolyte membrane comprising the same.

  That is, the proton conductive polymer electrolyte of the present invention comprises an aromatic polymer compound containing a proton conductive substituent and a non-aromatic polymer compound, and has excellent proton conductivity and high methanol blocking properties.

  At this time, it is preferable that the content of the non-aromatic polymer compound in the proton conductive polymer electrolyte is 0.01 to 30% by weight because particularly excellent proton conductivity and high methanol blocking properties are compatible. .

  Further, when the aromatic polymer compound is polyphenylene sulfide, the chemical and thermal stability is high, and proton conductive substituents can be easily introduced, so that high proton conductivity, and further proton conductive polymer electrolyte membrane. In this case, it is preferable because the film has a high methanol barrier property.

  Furthermore, when the non-aromatic polymer compound is at least one selected from the group consisting of polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl fluoride, chemical and thermal stability, It is preferable because it is excellent in processability and miscibility with an aromatic polymer compound and is industrially available at a low cost.

  Further, the non-aromatic polymer compound is preferably fiberized by a shearing force during mixing and / or kneading with the aromatic polymer compound, and has higher proton conductivity and higher methanol barrier properties and durability. It becomes a molecular electrolyte. In particular, fiberized polytetrafluoroethylene is preferred because of its high chemical stability and easy fiberization.

  The proton conductive substituent is preferably a sulfonic acid group from the viewpoint of ease of introduction of the proton conductive substituent and proton conductivity of the resulting proton conductive polymer electrolyte.

  The proton conductive polymer electrolyte of the present invention can be easily formed as a membrane, and is usually used as a proton conductive polymer electrolyte membrane.

  The proton conductive polymer electrolyte membrane of the present invention is used as a membrane-electrode assembly. The membrane-electrode assembly of the present invention is preferably used mainly for solid polymer fuel cells, particularly for direct methanol fuel cells.

  INDUSTRIAL APPLICABILITY According to the present invention, a proton conductive polymer electrolyte having excellent proton conductivity and high methanol barrier property, and useful as a constituent material of a solid polymer fuel cell or a direct methanol fuel cell, and a proton conductivity comprising the same A conductive polymer electrolyte membrane can be obtained.

  The proton conductive polymer electrolyte of the present invention comprises an aromatic polymer compound containing a proton conductive substituent and a non-aromatic polymer compound.

  Examples of the aromatic polymer compound used in the proton conductive polymer electrolyte of the present invention include polyaryl ether sulfone, polyether ether sulfone, polyether ketone, polyether ketone ketone, polysulfone, polyparaphenylene, and polyphenylene oxide. , Polyphenylene sulfoxide, polyphenylene sulfide sulfone, polyphenylene sulfone, polybenzimidazole, polybenzoxazole, polybenzothiazole, polystyrene, syndiotactic polystyrene, styrene- (ethylene-butylene) styrene copolymer, styrene- (polyisobutylene) -styrene Copolymer, poly 1,4-biphenylene ether ether sulfone, polyarylene ether sulfone, polyimide, polyether imide, shear Ester resin, polyphenylene sulfide, polyether ether ketone, or the like can be exemplified. In particular, chemical and thermal stability, ease of introduction of proton-conductive substituents, proton conductivity of the resulting proton-conductive polymer electrolyte, and high proton conductivity of the proton-conductive polymer electrolyte. In view of the methanol barrier property of the molecular electrolyte membrane, polyphenylene sulfide is preferable. Specifically, the polyphenylene sulfide is composed of a repeating structural unit represented by the following formula (1).

-[Ar-S] _n- (1)
[Wherein Ar is a divalent aromatic unit represented by the following formulas (2) to (4), and n is an integer of 1 or more]

また前記Ａｒの一部に、必要に応じて下記（１）〜（３）の構造単位を含有してもよい。
（１）芳香族単位の水素原子の一部がアルキル基、フェニル基、アルコキシル基、ニトロ基およびハロゲン基からなる群から選択される少なくとも１つの置換基で置換されたもの。
（２）３官能フェニルスルフィド単位。
（３）架橋または分岐単位。

Moreover, you may contain the structural unit of following (1)-(3) in a part of said Ar as needed.
(1) A part of hydrogen atoms of an aromatic unit is substituted with at least one substituent selected from the group consisting of an alkyl group, a phenyl group, an alkoxyl group, a nitro group and a halogen group.
(2) Trifunctional phenyl sulfide unit.
(3) Cross-linked or branched units.

  As a result, in addition to proton conductivity, chemical and thermal stability, handling properties, productivity, etc., which are necessary properties of proton conducting polymer electrolytes, methanol blocking properties of polymer electrolyte membranes composed of the above polymer electrolytes Is excellent and preferable.

  The non-aromatic polymer compound in the present invention refers to a compound that does not have an aromatic unit in its structural unit, and constitutes a structural unit that does not contain a proton conductive substituent when a polymer electrolyte membrane is formed. Examples of such non-aromatic polymer compounds include polyethylene such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, polypropylene, poly-1-butene, polyisobutylene, polytetrafluoroethylene, and polyvinylidene fluoride. Ride, polyvinyl fluoride, etc. can be listed. These may be used alone or in admixture of two or more, or random or block copolymers of any ratio may be used. In particular, among these, considering chemical and thermal stability, processability, miscibility with aromatic polymer compounds, industrial availability, price, etc., polyethylene, polypropylene, polytetrafluoroethylene, It is preferably at least one selected from the group consisting of polyvinylidene fluoride and polyvinyl fluoride.

  In the present invention, the non-aromatic polymer compound is preferably fiberized by shearing force during mixing and / or kneading with the aromatic polymer compound, and more preferably fiberized polytetrafluoroethylene. . Specifically, the non-aromatic polymer compound is mixed with a non-aromatic polymer compound powder and a non-aromatic polymer compound powder by a powder mixing method using a Henschel mixer in advance. For example, a method of melt-mixing with an aromatic polymer compound so as to obtain a predetermined mixing ratio can be applied. In addition, a method of making the non-aromatic polymer compound into a fiber by a shearing force when kneading the aromatic polymer compound and the non-aromatic polymer compound by a melt extrusion method can also be applied.

  The non-aromatic polymer compound used in the present invention is not particularly limited as long as it is a non-aromatic polymer compound that is made into a fiber by applying a shearing force. Examples include powders produced by agglomerating emulsion dispersions of high molecular weight polytetrafluoroethylene obtained by emulsion polymerization methods, powders produced from high molecular weight polytetrafluoroethylene obtained by suspension polymerization methods, etc. It is done. In particular, among the polytetrafluoroethylene, a powder produced by agglomerating an emulsified dispersion of a high molecular weight polytetrafluoroethylene obtained by an emulsion polymerization method is preferable because it is easily fiberized by shearing force.

  In the proton conductive polymer electrolyte of the present invention, the content of the non-aromatic polymer compound in the proton conductive polymer electrolyte is preferably 0.01 to 30 parts by weight. When the content of the non-aromatic polymer compound is smaller than the above range, the content effect of the non-aromatic polymer compound may be unclear. On the other hand, when the content of the non-aromatic polymer compound is larger than the above range, the proton conductivity may be difficult to express. In addition, it is necessary to set the content of the proton-conductive substituent in the aromatic polymer compound high, and the durability of the proton-conductive polymer electrolyte may be reduced.

  The proton conductive substituent contained in the proton conductive polymer electrolyte of the present invention can be used as long as it dissociates protons in a water-containing state. For example, a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a phenolic hydroxyl group, etc. can be exemplified. In particular, considering the ease of introduction of a proton conductive substituent and the proton conductivity of the resulting proton conductive polymer electrolyte, etc. A sulfonic acid group is preferred. The ion exchange capacity of the proton conductive polymer electrolyte derived from the content of the proton conductive substituent is preferably 0.3 meq / g or more, more preferably 0.5 meq / g or more. More preferably, it is 1.0 meq / g or more. If the ion exchange capacity is lower than 0.3 meq / g, the desired proton conductivity may not be exhibited, which is not preferable.

  The proton conductive polymer electrolyte of the present invention has excellent proton conductivity and high durability, and is useful as a constituent material for solid polymer fuel cells and direct methanol fuel cells. Specifically, it is useful as a constituent material for forming a catalyst layer on a diffusion electrode made of a conductive porous material such as carbon paper or carbon cloth. As a material for forming a catalyst layer, a noble metal catalyst such as platinum or platinum-ruthenium is supported on a conductive high specific surface area carrier such as carbon black, activated carbon, or carbon nanohorn, and is immobilized on a diffusion electrode. Is preferred.

  Further, if the polymer electrolyte is processed into a membrane, a proton conductive polymer electrolyte membrane having excellent proton conductivity, high methanol blocking property, and higher durability can be obtained, which is preferable. Since these have the above-mentioned properties, they are useful as proton conductive polymer electrolyte membranes for solid polymer fuel cells and direct methanol fuel cells. Specifically, when the proton conductive polymer electrolyte described above has solvent solubility, it can be processed into a membrane by a solution casting method or the like to obtain a proton conductive polymer electrolyte membrane. Further, when the proton conductive polymer electrolyte is thermoplastic and can be melted at a temperature lower than the temperature at which the proton conductive substituent is deteriorated, the proton conductive polymer electrolyte is processed into a film by a hot press molding method, a melt extrusion method, or the like. A conductive polymer electrolyte membrane can be obtained.

  On the other hand, when the proton conductive polymer electrolyte is derived from the constituent material to be used and does not exhibit solvent solubility or thermoplasticity, a polymer film composed of an aromatic polymer compound and a non-aromatic polymer compound is used. It is preferable to introduce a proton conductive substituent such as a sulfonic acid group after the production. Specifically, the proton conductive substituent can be introduced into the aromatic unit in the aromatic polymer compound by bringing the polymer film into contact with a proton conductive substituent introducing agent such as a sulfonating agent. . Hereinafter, the case of introducing a sulfonic acid group as a proton conductive substituent will be described in more detail.

  The polymer film is obtained by obtaining a resin composition containing these from an aromatic polymer compound such as polyphenylene sulfide and a non-aromatic polymer compound such as polytetrafluoroethylene by a melt extrusion method. A polymer film can be obtained by a die method or the like. At this time, as described above, in the process of obtaining the resin composition, the non-aromatic polymer compound is fibrillated by the shearing force when the aromatic polymer compound and the non-aromatic polymer compound are mixed and / or kneaded. it can. Subsequently, a sulfonic acid group can be introduce | transduced into the aromatic unit of the aromatic polymer compound in the said polymer film by making the said polymer film and a sulfonating agent contact in a solvent as needed.

  Here, as the sulfonating agent, known sulfonating agents such as chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, sulfur trioxide-triethyl phosphate, concentrated sulfuric acid, trimethylsilyl chlorosulfate, and trimethylbenzenesulfonic acid can be used. . In view of industrial availability, ease of introduction of sulfonic acid groups and characteristics of the resulting proton conducting polymer membrane, at least one selected from the group consisting of chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, and concentrated sulfuric acid. Preferably it is a seed. In particular, chlorosulfonic acid is more preferably used from the viewpoint of easy introduction of sulfonic acid groups, characteristics of the obtained membrane, industrial availability, and the like. Here, the amount of the sulfonating agent used is 0.5 to 30 equivalents, more preferably 0.5 to 15 equivalents, with respect to the aromatic units in the aromatic polymer compound contained in the polymer film. Is preferred. When the amount of the sulfonating agent used is less than 0.5 equivalent, the amount of sulfonic acid group introduced tends to decrease, or the time required for introduction tends to increase. On the other hand, when it exceeds 30 equivalents, the polymer film is chemically deteriorated, the mechanical strength of the resulting polymer electrolyte membrane is lowered, handling becomes difficult, and the amount of sulfonic acid groups introduced increases. However, the practical properties of the polymer electrolyte membrane tend to be impaired, for example, the methanol barrier property is lowered.

  In addition, by optimizing the reaction system, according to the Friedel-Crafts reaction, in the presence of a catalyst such as aluminum chloride, cyclic sulfur-containing compounds such as propane sultone and 1,4-butane sultone and aromatic polymer compounds A method of introducing a substituent containing a sulfonic acid group such as a sulfopropyl group or a sulfobutyl group by bringing the aromatic unit into contact with each other can also be used.

  The solvent may be any solvent that can be mixed with a sulfonating agent and does not inhibit the sulfonation reaction. In particular, in view of ease of mixing with a sulfonating agent and ease of introduction of a sulfonic acid group, a halogenated hydrocarbon solvent is preferable. As the halogenated hydrocarbon solvent, various solvents can be used. For example, 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, dichloromethane, chloroform, 1-chloropropane, 1-bromopropane, 1-iodopropane, 1-chlorobutane, 2-chlorobutane, 1,4-dichlorobutane, 1-chloro-2- Methylpropane, 1-bromobutane, 2-bromobutane, 1-bromo-2-methylpropane, 1-iodobutane, 2-iodobutane, 1-iodo-2-methylpropane, 1-chloropentane, 1-bromopentane, 1-iodo Pentane, 1-chlorohexane, 1-bromohexane, 1-iodine Dohekisan, chloro cyclohexane, bromo cyclohexane, iodo cyclohexane enumerable. In particular, considering the ease of handling of the solvent to be used, industrial availability, etc., it is preferable to use a halide having 3 or more carbon atoms, more preferably 1-chlorobutane.

  The concentration of the sulfonating agent in the mixed solution composed of the sulfonating agent and the solvent may be appropriately set in consideration of the target introduction amount of sulfonic acid groups and reaction conditions (temperature / time). Specifically, it is preferably 0.1 to 10% by weight, and a more preferable range is 0.2 to 5% by weight. If it is lower than 0.1% by weight, the desired sulfonic acid group tends not to be introduced or it takes too much time to introduce. On the other hand, when the content exceeds 10% by weight, the introduction of sulfonic acid groups tends to be non-uniform or the mechanical properties of the resulting polymer electrolyte membrane tend to be impaired.

  The reaction temperature and reaction time for contacting are not particularly limited, but are set within the range of 0 to 100 ° C., further 10 to 30 ° C., 0.5 hour or more, and further 2 to 100 hours. preferable. When the reaction temperature is lower than 0 ° C, measures such as cooling on the equipment are necessary, and the reaction tends to take more time than necessary. When the reaction temperature exceeds 100 ° C, the reaction proceeds excessively or side reactions occur. Or the like, and the film characteristics tend to be deteriorated. When the reaction temperature is higher than the boiling point of the sulfonating agent or the solvent, additional equipment is required, and therefore, the reaction is preferably carried out at a temperature not higher than the boiling point of the solvent. In addition, when the reaction time is shorter than 0.5 hours, the contact between the sulfonating agent and the aromatic unit in the polymer compound becomes insufficient, and the desired sulfonic acid group tends to be difficult to be introduced. When the time exceeds 100 hours, productivity tends to be remarkably lowered, and a great improvement in film properties tends not to be expected. In actuality, if the setting is made so that a polymer electrolyte membrane having desired characteristics can be efficiently produced in consideration of a reaction system such as a sulfonating agent and a solvent to be used and a target production amount. Good.

  It is preferable to wash with water in order to remove the unreacted sulfonating agent and the solvent after the step of introducing the sulfonic acid group. At this time, it is preferable that the polymer electrolyte membrane is obtained by continuously washing with water and drying under appropriate conditions without recovering the polymer electrolyte membrane after the sulfonic acid group introduction step. Further, instead of washing with water, the polymer electrolyte membrane may be obtained by performing neutralization washing with a sodium hydroxide aqueous solution or the like and then performing acid treatment.

  Moreover, you may implement the manufacturing method of the polymer electrolyte membrane by the said method continuously. That is, a polymer film composed of an aromatic polymer compound and a non-aromatic polymer, which is an object to be treated, is continuously supplied to a reaction vessel with a sulfonating agent, and a washing process and a drying process are further performed as necessary. It may be carried out continuously, and it is not necessary to purify or collect the polymer electrolyte membrane in the middle of the process. This method improves productivity.

  In the above method, sulfonic acid groups can be introduced in the form of a film (membrane) by bringing the polymer film into contact with a sulfonating agent in a reaction vessel. Therefore, after introducing sulfonic acid groups into the polymer compound in the conventional homogeneous reaction system, compared to the method of processing into a membrane shape, the process of recovery / purification / drying of reactants, sulfonic acid group inclusion in the solvent It is preferable because steps such as dissolution of the polymer compound, application to the support, and solvent removal can be omitted. Furthermore, since the film is continuously supplied, the productivity is remarkably improved.

  In addition, by continuously removing and washing the sulfonating agent attached to and / or contained in the film immersed in the reaction vessel, it is possible to prevent corrosion of peripheral equipment by the sulfonating agent and to handle the film. Improve. The conditions for removal / washing may be set as appropriate in consideration of the sulfonating agent used and the structure of the polymer film, but the remaining sulfonating agent is inactivated by washing with water or neutralized using alkali. It may be processed.

  Furthermore, by continuously drying the obtained polymer electrolyte membrane, the polymer electrolyte membrane can be recovered in a practically usable form. What is necessary is just to set drying conditions suitably in consideration of the kind of polymer film to be used and the characteristic of the polymer electrolyte membrane obtained. Since the sulfonic acid group has strong hydrophilicity, it may be swelled with water during the washing process. Therefore, it shrinks at the time of drying, and there is a possibility that irregularities such as wrinkles and swelling occur. Therefore, at the time of drying, it is preferable to dry by applying an appropriate tension in the surface direction of the polymer electrolyte membrane. Moreover, in order to suppress rapid drying, you may dry gradually under adjustment of humidity.

Depending on the sulfonating agent used and the reaction conditions for sulfonation, for example, when polyphenylene sulfide is used as the aromatic polymer compound, the sulfide unit (—S—) in the polymer film may be converted to a sulfoxide unit (—SO—). ) Or a sulfone unit (—SO ₂ —), a sulfoxide unit (—SO—) is oxidized to a sulfone unit (—SO ₂ —), or hydrogen of a phenylene unit is substituted with —Cl or the like. Side reactions that are substituted with groups can occur. However, as long as the properties of the obtained polymer electrolyte membrane are not significantly reduced, a structural unit resulting from the side reaction may be included.

  Furthermore, it is preferable to irradiate the polymer electrolyte membrane obtained by the above method with at least one kind of radiation selected from the group consisting of γ rays, electron beams and ion beams, and the irradiation amount is 10 to 1000 kGy. It is preferable.

  The polymer electrolyte membrane may contain an appropriate amount of additives such as a plasticizer, an antioxidant, an antistatic agent, an antibacterial agent, a lubricant, a surfactant, and various fillers.

  Next, the membrane-electrode assembly of the present invention will be described with reference to the drawings as an example. FIG. 1 is a cross-sectional view of an essential part of a solid polymer fuel cell (direct methanol fuel cell) using the polymer electrolyte membrane of the present invention. This is a catalyst-supporting gas in which the binder layers 2 and 3 are formed on both sides of the polymer electrolyte membrane 1 and 1 as necessary, and the catalyst layers 4 and 5 and the diffusion layers 6 and 7 are provided on the outer sides thereof. Diffusion electrodes 8 and 9 are arranged to form a membrane-electrode assembly 10. Examples of the catalyst-carrying gas diffusion electrodes 8 and 9 include a method using a commercially available catalyst-carrying gas diffusion electrode (manufactured by E-TEK, Inc., USA), but are not limited thereto.

  In the present invention, the polymer electrolyte membrane 1 is the polymer electrolyte membrane of the present invention described above.

  The binder layers 2 and 3 may be the same or different, and may be formed as necessary, or may not be formed. In general, perfluorocarbon sulfonic acid-based polymer compounds represented by Nafion, known proton-conducting polymer compounds with solvent solubility such as sulfonated polyetheretherketone, sulfonated polyethersulfone, and sulfonated polyimide are used. used. These are used for joining (adhering) the polymer electrolyte membrane 1 and the catalyst layer 4.5. These materials are required to have proton conductivity, chemical stability, and the like in the same manner as the polymer electrolyte membrane, in addition to the bonding properties to the different materials.

  The catalyst layers 4 and 5 may be the same or different, and a catalyst having the ability to oxidize the fuel (hydrogen, methanol, etc.) to be used is used on one side. On the other hand, a catalyst having the reducing ability of the oxidizing agent (oxygen, air, etc.) used is used. Specifically, a material in which a noble metal catalyst such as platinum is supported on a conductive material having a high surface area such as carbon black, activated carbon, carbon nanohorn, or carbon nanotube is used. When a fuel other than pure hydrogen is used, a composite or alloy catalyst made of platinum and ruthenium is used instead of platinum in order to suppress poisoning of the catalyst.

  The diffusion layers 6 and 7 may be the same or different, and a porous conductive material such as carbon paper or carbon cloth is used. These are supplied water or water generated by an electrochemical reaction and may be subjected to water repellent treatment with a fluorine-based compound such as polytetrafluoroethylene as necessary in order to prevent pores from being blocked. . Generally, on these diffusion layers 6 and 7, the catalyst layers 4 and 5 are perfluorocarbon sulfonic acid polymer compounds represented by Nafion, sulfonated polyetheretherketone, sulfonated polyethersulfone, The catalyst-supported gas diffusion electrodes 8 and 9 are prepared and used by using a known proton-conductive polymer compound having a solvent solubility such as sulfonated polyimide as a binder.

  In the membrane-electrode assembly 10 of the present invention, at least one of the catalyst layers 4 and 5 is preferably made of platinum and a ruthenium catalyst. In the present invention, since a material having a high methanol barrier property is used as the polymer electrolyte membrane 1, unreacted methanol in one catalyst layer 4 permeates the polymer electrolyte membrane 1, and the other catalyst layer. It is possible to suppress poisoning of the catalyst No. 5, which is preferable.

  The manufacturing method of the membrane-electrode assembly 10 of the present invention can be selected from known or arbitrary methods. As an example, after applying an organic solvent solution of the constituent materials of the binders 2 and 3 onto the catalyst layers 4 and 5 of the catalyst-carrying gas diffusion electrodes 8 and 9, the solvent is removed and the polymer electrolyte membrane 1 is removed. Place on both sides. Thereafter, using a press machine such as a hot press machine or a roll press machine, the membrane-electrode assembly 10 can be prepared by hot pressing generally at a press temperature of about 120 to 250 ° C. If necessary, the membrane-electrode assembly 10 may be prepared without using the binders 2 and 3. From the fuel gas or liquid formed in the separators 11 and 12 disposed outside the membrane-electrode assembly 10 and the flow paths 13 and 14 for feeding the oxidant, the polymer electrolyte fuel cell of the present invention ( A direct methanol fuel cell) 15 is configured. The separators 11 and 12 are made of carbon graphite or metal plate having electrical conductivity and chemical stability, and fuel and oxidant blocking properties. Further, these may be subjected to water repellent treatment or corrosion resistance treatment as necessary. On the surfaces of the separators 11 and 13, flow paths 13 and 14 for feeding the fuel gas or liquid and the oxidant are formed. A gas containing hydrogen as a main component or a gas or liquid containing methanol as a main component is supplied to one channel 13 as a fuel gas or liquid, and a gas containing oxygen (oxygen or air) as the oxidant is supplied to the other channel. The polymer electrolyte fuel cell of the present invention operates by supplying each to the flow path 14. At this time, when methanol is used as the fuel, a direct methanol fuel cell is obtained.

  The polymer electrolyte fuel cell (direct methanol fuel cell) of the present invention can be used alone or in a stack to form a stack, or a fuel cell system incorporating them.

  Furthermore, a direct methanol fuel cell using the proton conductive polymer electrolyte membrane of the present invention will be described with reference to the drawings as an example.

  FIG. 2 is a cross-sectional view of an essential part of the direct methanol fuel cell of the present invention. The required number of membrane-electrode assemblies 10 are arranged in a plane on both sides of a fuel (methanol or methanol aqueous solution) tank 16 having a function of filling and supplying fuel (methanol or methanol aqueous solution). Further, a support 18 having an oxidant flow path 17 formed thereon is disposed on the outside thereof, and a cell and a stack of a direct methanol fuel cell are configured by being sandwiched between them.

  In addition to the above examples, the polymer electrolyte membrane and membrane-electrode assembly of the present invention are disclosed in JP 2001-313046 A, JP 2001-313047 A, JP 2001-93551 A, and JP 2001-2001 A. 93,558, JP-A 2001-93561, JP-A 2001-102069, JP-A 2001-102070, JP-A 2001-283888, JP-A 2000-268835, JP-A 2000-268836 It can be used as a polymer electrolyte membrane or membrane-electrode assembly of a direct methanol fuel cell, which is publicly known in Japanese Patent Laid-Open No. 2001-283892.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

Example 1
<Preparation of polymer film comprising aromatic polymer compound and non-aromatic polymer compound>
As a resin composition comprising an aromatic polymer compound and a non-aromatic polymer compound, a resin composition comprising polyphenylene sulfide and polytetrafluoroethylene (Dainippon Ink Industries, Ltd., DIC-PPS ZL-130, polytetrafluoroethylene) Fluoroethylene content: 30% by weight) was used.

A polymer comprising an aromatic polymer compound and a non-aromatic polymer compound obtained by hot press molding the resin composition under the conditions of a press temperature: 300 ° C., a press pressure: 50 kgf / cm ² , and a press time: 5 minutes. A film was obtained.
<Preparation of proton conductive polymer electrolyte membrane>
In a glass container, 267 g of 1-chlorobutane and 3.3 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. 0.88 g of the polymer film was weighed, immersed in a chlorosulfonic acid solution, and allowed to stand at room temperature for 20 hours (the amount of chlorosulfonic acid added was 5 equivalents relative to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polymer film was recovered and washed with ion-exchanged water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, A proton conducting polymer electrolyte membrane of the present invention was obtained.

<Measurement method of ion exchange capacity>
A proton conductive polymer electrolyte membrane (about 10 mm × 40 mm) was immersed in 20 mL of a saturated aqueous sodium chloride solution at 25 ° C., and reacted in a water bath at 60 ° C. for 3 hours. After cooling to 25 ° C., the membrane was thoroughly washed with ion exchanged water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this recovered solution, a phenolphthalein solution was added as an indicator, and neutralization titration with a 0.01N sodium hydroxide aqueous solution was performed to calculate the ion exchange capacity.

  The results are shown in Table 1.

<Measurement method of proton conductivity>
A polymer electrolyte membrane (about 10 mm × 40 mm) stored in ion-exchanged water was taken out, and water on the membrane surface was wiped off with a filter paper. The membrane was installed in a cell made of Teflon (registered trademark) in a bipolar non-sealing system, and a platinum electrode was further installed on the membrane surface (on the same side) so that the distance between the electrodes was 30 mm. The membrane resistance at 23 ° C. was measured by an AC impedance method (frequency: 42 Hz to 5 MHz, applied voltage: 0.2 V), and proton conductivity was calculated.

  The results are shown in Table 1.

<Measurement method of methanol barrier properties>
In an environment of 25 ° C., a membrane transmission experiment apparatus manufactured by Beadrex was used. Ion exchange water and a methanol aqueous solution having a predetermined concentration were separated by a polymer electrolyte membrane, a solution containing methanol permeated to the ion exchange water side after a lapse of a predetermined time was collected, and the amount of methanol permeated by gas chromatography was quantified. From this quantification result, the methanol permeation rate was determined, and the methanol permeation coefficient and the methanol cutoff coefficient were calculated. The methanol permeability coefficient and the methanol cutoff coefficient were calculated according to the following formulas 1 and 2.

  The results are shown in Table 1.

（実施例２）
１−クロロブタン量を２３７ｇ、クロロスルホン酸量を３．６ｇ、高分子フィルム量を０．７８ｇとした以外は、実施例１と同様にしてプロトン伝導性高分子電解質膜を得た（クロロスルホン酸添加量は、ポリフェニレンサルファイドの芳香族単位に対して６当量）。

(Example 2)
A proton conductive polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the amount of 1-chlorobutane was 237 g, the amount of chlorosulfonic acid was 3.6 g, and the amount of polymer film was 0.78 g (chlorosulfonic acid The addition amount is 6 equivalents with respect to the aromatic unit of polyphenylene sulfide).

  The results are shown in Table 1.

Example 3
A proton conductive polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the amount of 1-chlorobutane was 259 g, the amount of chlorosulfonic acid was 5.2 g, and the amount of the polymer film was 0.85 g (chlorosulfonic acid The addition amount is 8 equivalents with respect to the aromatic unit of polyphenylene sulfide).

  The results are shown in Table 1.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that Nafion (registered trademark) 115 manufactured by DuPont, which is a non-hydrocarbon polymer electrolyte membrane, was used as the proton conductive polymer electrolyte membrane.

  The results are shown in Table 1.

(Comparative Example 2)
A proton conducting polymer electrolyte membrane was prepared in the same manner as in Example 1 except that it was prepared according to the following method.
<Preparation of proton conductive polymer electrolyte membrane>
In a glass container, 431 g of dichloromethane and 2.2 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. As a polymer film, 1.0 g of polyphenylene sulfide film (trade name: Torelina, thickness: 50 μm, manufactured by Toray Industries, Inc.) was weighed, immersed in a chlorosulfonic acid solution, and left at room temperature for 20 hours (chlorosulfone). The acid addition amount is 2 equivalents with respect to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polymer film was recovered and washed with ion-exchanged water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, A proton conducting polymer electrolyte membrane was obtained.

表１の実施例１〜３と比較例１，２との比較から、本発明のプロトン伝導性高分子電解質膜は、従来のプロトン伝導性高分子電解質膜と同オーダーのプロトン伝導度を有し、プロトン伝導性高分子電解質膜として有用であることが明らかとなった。

From comparison between Examples 1 to 3 and Comparative Examples 1 and 2 in Table 1, the proton conductive polymer electrolyte membrane of the present invention has proton conductivity in the same order as that of the conventional proton conductive polymer electrolyte membrane. This proved useful as a proton conductive polymer electrolyte membrane.

  From comparison between Examples 1 to 3 and Comparative Examples 1 and 2 in Table 1, the proton conductive polymer electrolyte membrane of the present invention has a lower methanol permeability coefficient and higher methanol than the conventional proton conductive polymer electrolyte membrane. It became clear that it showed a cutoff coefficient, and it was shown that it is useful as a polymer electrolyte membrane for direct methanol fuel cells.

Cross-sectional view of the main part of the polymer electrolyte fuel cell (direct methanol fuel cell) of the present invention Cross-sectional view of essential parts of the direct methanol fuel cell of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2,3 Binder 4,5 Catalyst layer 6,7 Diffusion layer 8,9 Catalyst carrying | support gas diffusion electrode 10 Membrane-electrode assembly 11,12 Separator 13 Fuel flow path 14 Oxidant flow path 15 Solid Polymer fuel cell (direct methanol fuel cell)
16 Fuel tank 17 Oxidant flow path 18 Support

Claims (8)

(1) an aromatic polymer compound and at least one non-aromatic polymer compound selected from polyethylene, polypropylene, poly-1-butene, polyisobutylene, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl fluoride ; A step of forming a polymer composition by molding a resin composition containing a hydrogen atom, and (2) contacting the polymer film with a proton conductive substituent-introducing agent to form protons on the aromatic units in the aromatic polymer compound. step you introducing conductivity substituent,
including,
A method for producing a proton conductive polymer electrolyte membrane. The polymer film is molded by a hot press molding method or a melt extrusion method,
The method for producing a proton conductive polymer electrolyte membrane according to claim 1. The method for producing a proton conductive polymer electrolyte membrane according to claim 1 or 2, wherein the content of the non-aromatic polymer compound in the proton conductive polymer electrolyte is 0.01 to 30% by weight. . The method for producing a proton conductive polymer electrolyte membrane according to any one of claims 1 to 3, wherein the aromatic polymer compound is polyphenylene sulfide. The non-aromatic polymer compound is at least one selected from the group consisting of polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl fluoride. A method for producing a proton conductive polymer electrolyte membrane according to claim 1. 6. The proton-conductive polymer according to claim 1, wherein the non-aromatic polymer compound is fiberized by a shearing force during mixing and / or kneading with the aromatic polymer compound. A method for producing a molecular electrolyte membrane. The method for producing a proton conductive polymer electrolyte membrane according to any one of claims 1 to 6, wherein the non-aromatic polymer compound is fiberized polytetrafluoroethylene. The method for producing a proton conductive polymer electrolyte membrane according to claim 1, wherein the proton conductive substituent is a sulfonic acid group.

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