JP2006318663A - Proton conductive electrolyte film, its process of manufacture, and solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductive electrolyte film of high proton conductivity, low methanol permeability, and good jointing property with an electrocatalyst layer, along with its manufacturing method and a solid polymer fuel cell that uses the proton conductive electrolyte film 1. <P>SOLUTION: The proton conductive electrolyte film contains proton conductive polymer in fine pores of a porous film. The proton conductive electrolyte film 1 features 0.5-10.0 μm of arithmetic average roughness Ra on the surface of electrolyte film by JIS B 0601. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a proton conductive electrolyte membrane and a method for producing the proton conductive electrolyte membrane, and more particularly to a polymer electrolyte fuel cell using the proton conductive electrolyte membrane as an electrolyte membrane for a fuel cell.

  A fuel cell is a power generation device that generates electricity by reacting hydrogen and oxygen, and has the excellent property that only water is generated by the power generation reaction, thus addressing global environmental problems such as global warming and ozone layer destruction. It is attracting attention as an energy-saving technology.

  There are four types of fuel cells: solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. Among these, the polymer electrolyte fuel cell has an advantage that the operating temperature is low. The polymer electrolyte fuel cell includes a direct hydrogen type that uses hydrogen directly, a reformed type that converts methanol into hydrogen using a reformer, and a direct methanol type that uses methanol directly without using a reformer (DMFC, (Direct Methanol Fuel Cell). Since DMFC does not require a reformer, it can be reduced in size and weight, and its practical application as a battery or a dedicated battery for personal digital assistants (PDAs) for the future ubiquitous society. Is expected.

  Main components of the polymer electrolyte fuel cell are an electrode, a catalyst, an electrolyte, and a separator. A polymer proton-conducting electrolyte membrane is used as the electrolyte. Proton conductive electrolyte membranes are used for applications such as ion exchange membranes and humidity sensors, but in recent years, they are also attracting attention for applications as electrolytes in polymer electrolyte fuel cells. For example, use of a sulfonic acid group-containing fluororesin membrane represented by Nafion (registered trademark) of DuPont as an electrolyte in a portable fuel cell is under study.

  These conventionally known fluororesin proton conductive membranes have a drawback of high methanol permeability. In order to put the proton conductive membrane into practical use in a new application of a polymer electrolyte fuel cell such as DMFC, it is indispensable to develop a membrane having high proton conductivity and low methanol permeability. In particular, in order to improve the performance as DMFC, it is essential to reduce the film thickness, and the physical strength of the film is also required.

  Therefore, for the purpose of providing an electrolyte membrane that suppresses methanol permeation (crossover) as much as possible and can withstand use in a high-temperature (about 130 degrees Celsius) environment, it is substantially less than methanol and water. An electrolyte membrane in which pores of a porous substrate that does not swell are filled with a polymer having proton conductivity is disclosed (for example, see Patent Document 1). As the porous substrate, it is described that ceramic inorganic materials such as glass and alumina, polytetrafluoroethylene, polyimide and the like may be used. Furthermore, for the purpose of suppressing methanol permeation (crossover) as much as possible, an electrolyte membrane in which pores of an inorganic porous substrate are filled with a polymer having proton conductivity is disclosed (for example, Non-Patent Document 1). reference.).

Further, as a major problem when a fuel cell is configured, a poor bonding property between the electrode catalyst layer and the electrolyte membrane is a problem. If the bondability between the electrode catalyst layer and the electrolyte membrane is poor, the resistance at the interface increases, which causes a decrease in power generation efficiency. Therefore, a catalyst layer-electrolyte membrane laminate is disclosed in which the surface roughness of the electrolyte membrane is roughened to about 1 to 10 μm for the purpose of reducing the resistance at the interface between the electrode catalyst layer and the electrolyte membrane and improving the output. (For example, refer to Patent Document 2). Furthermore, a membrane electrode assembly in which the surface roughness of the electrolyte membrane is 0.1 to 10 μm is also disclosed for the purpose of improving gas sealing properties and output (see, for example, Patent Document 3). These electrolyte membranes are merely electrolyte membranes such as a Nafion membrane manufactured by DuPont, and are different from electrolyte membranes in which the pores of the porous membrane of the present invention are filled with a proton conductive polymer.
International Publication No. 00/54351 Pamphlet JP 2005-63832 A JP 2003-282094 A Electrochemistry, 70, 934 (2002)

  In order to withstand the practical use of the proton conductive electrolyte membrane as an electrolyte of a polymer electrolyte fuel cell, it is also an important factor that at least the proton conductivity is sufficiently high and the methanol permeability is sufficiently low. Furthermore, the bondability with the electrode catalyst layer is an important factor for improving the output.

  Accordingly, the first object of the present invention is to provide an excellent performance with high proton conductivity and low methanol permeability by forming a composite membrane of the electrolyte membrane, and at the same time, by optimizing the surface roughness of the electrolyte membrane. It is to provide a proton conductive electrolyte membrane having a good bonding property to the substrate and a method for producing a proton conductive electrolyte membrane having such excellent performance.

  A second object of the present invention is to provide a polymer electrolyte fuel cell having a proton conductive electrolyte membrane having excellent performance as described above as an electrolyte.

  The above object of the present invention has been achieved by the following constitution.

(Claim 1)
A proton conductive electrolyte membrane containing a proton conductive polymer in the pores of the porous membrane, wherein an arithmetic average roughness Ra according to JIS B 0601 of the electrolyte membrane surface is 0.5 to 10.0 μm A proton conductive electrolyte membrane.

(Claim 2)
The proton conductive electrolyte membrane according to claim 1, wherein the porous membrane is an inorganic porous membrane.

(Claim 3)
The proton conductive electrolyte membrane according to claim 1, wherein the porous membrane is an organic porous membrane containing inorganic particles.

(Claim 4)
A polymer electrolyte fuel cell comprising a cathode electrode, an anode electrode, and an electrolyte sandwiched between the electrodes, wherein the proton conductive electrolyte membrane according to any one of claims 1 to 3 is used as the electrolyte. Solid polymer fuel cell.

(Claim 5)
A method for producing a proton conductive electrolyte membrane containing a proton conductive polymer in the pores of a porous membrane, wherein the arithmetic average roughness Ra of the electrolyte membrane surface according to JIS B 0601 is 0.5 to 10.0 μm A method for producing a proton conductive electrolyte membrane, characterized by comprising:

(Claim 6)
The proton conductive polymer in the pores is produced by containing a monomer containing one or more proton dissociable groups in at least a molecule in the pores, and then in-situ polymerization. The method for producing a proton conductive electrolyte membrane according to claim 5.

(Claim 7)
The proton conductive polymer in the pore contains a monomer containing at least one proton dissociable group in the pore and a compound represented by the following general formula (1), and then In 6. The method for producing a proton-conducting electrolyte membrane according to claim 5, wherein the method is produced by -situ polymerization.

(In the formula, R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents a copolymerizable or reactive organic group, and m and n are each an integer of 1 to 3, provided that m + n = 4. And when m is 2 or 3, R ² may be the same or different.)

  According to the present invention, a proton conductive electrolyte membrane having a sufficiently high proton conductivity, a sufficiently low methanol permeability, and a good bonding property with an electrode catalyst layer, a method for producing the same, and the proton conductive electrolyte membrane are used. A polymer electrolyte fuel cell could be provided.

  Hereinafter, the present invention will be described in detail.

  The proton conductive electrolyte membrane of the present invention is a proton conductive electrolyte membrane containing a proton conductive polymer in the pores of the porous membrane, and the arithmetic average roughness Ra according to JIS B 0601 on the surface of the electrolyte membrane is 0. .5 to 10.0 μm. The arithmetic average roughness Ra according to JIS B 0601 is a parameter representing the surface roughness at each portion randomly extracted from the surface of the object, and is defined in JIS B 0601. In the present invention, the arithmetic average roughness Ra when measured with a reference length of 2.5 mm and a cut-off value of 0.8 mm is 0.5 to 10.0 μm.

  Ra obtained by measuring under the above conditions is related to the average surface roughness and height, and by setting Ra to a specific range, the fuel cell is formed using the proton conductive electrolyte membrane of the present invention. When configured, the bondability between the electrolyte membrane and the electrode catalyst layer is improved, the interface resistance is lowered, and the output of the fuel cell can be improved. If Ra is less than 0.5 μm, the effect is small, and if it exceeds 10.0 μm, the bondability is adversely reduced, which is not preferable. The particularly preferable range of Ra is 1.0 to 5.0 μm.

  In adjusting Ra, there are various methods, for example, the following methods, and these can be adjusted by using them alone or in combination of two or more.

(1) Method of manufacturing by sandwiching between sheets having irregularities of regular or irregular shape Manufacture by pressurizing by sandwiching a porous film with a polymer whose surface is previously roughened. it can. The sheet preferably used in this method is a sheet in which irregularities are previously molded on the surface of the polyolefin resin. A typical method for producing such a sheet is performed by extruding and coating a molten polyolefin resin on a substrate, and then press-contacting a mold roller to form a fine uneven pattern. This patterning method includes a method of embossing calendering the sheet obtained by melt extrusion near room temperature, and a cooling roll engraved with a pattern on the roll surface during extrusion coating of polyolefin resin while cooling and However, the latter is preferable because it can be molded at a relatively low pressure and can be more accurately and homogeneously molded.

  In addition, the method of containing the proton conductive polymer in the pores of the porous membrane in the present invention is not particularly limited. For example, the method of applying the proton conductive polymer solution to the porous membrane, the porous membrane The proton conductive polymer can be contained in the pores of the porous membrane by, for example, a method of immersing in a proton conductive polymer solution.

  Preferably, a proton conductive polymer precursor solution is contained in the pores of the porous membrane, and the surface is sandwiched between the roughened sheets and pressed, and heat polymerization, photopolymerization, and the like are conventionally known. This is a method for producing a proton conductive polymer by in-situ polymerization or in-situ reaction by an appropriate method. The polymer precursor liquid means a monomer or the like that can be converted into a polymer by performing a treatment such as polymerization.

(2) Method of adding matting agent to proton conductive polymer When the porous membrane contains a polymer, it can be produced by adding a matting agent to the proton conductive polymer. The matting agent is preferably organic or inorganic fine particles having an average particle size of 0.01 to 10 μm. For example, titanium oxide, silica, glass powder, barium sulfate, polystyrene resin, polymethyl methacrylate resin, polycarbonate resin, polyacrylate copolymer resin. Etc. The matting agent may be monodispersed or polydispersed, and those having a dispersion degree (standard deviation / average particle diameter) of 0.2 to 10 can be preferably used.

(3) Method of engraving fine irregularities on the surface of the electrolyte membrane After forming the electrolyte membrane, a method of forming irregularities on the surface by sandblasting, atmospheric pressure plasma treatment, etching treatment, atmospheric pressure corona discharge treatment, calendar treatment, etc. It is done.

  The method for containing the proton conductive polymer in the pores of the porous membrane in the present invention is not particularly limited, and the same method as the above (1) can be used.

  The porous membrane in the present invention is not particularly limited, and examples thereof include inorganic porous membranes such as glass, silica, and alumina, and organic porous membranes such as polyethylene, tetrafluoroethylene, and polyimide. Particularly preferred are inorganic particles and It is an inorganic porous film obtained by the process of laminating and baking a dispersion containing organic particles, or an organic porous film containing inorganic particles.

  The inorganic porous film obtained by laminating and baking the dispersion liquid containing inorganic particles and organic particles is obtained by laminating the dispersion liquid containing inorganic particles and organic particles, and laminating the dispersion liquid. It is an inorganic porous film obtained by the process of baking. In the laminating step, a support may be used. As the support, a support made of any material can be used as long as it is eventually burned out or melted away, or can be peeled off, such as filter paper. A support made of any material such as paper, non-woven fabric, polymer film such as polyethylene terephthalate can be used.

  The surface of the support is preferably a rough surface, and if it is a rough surface, the surface of the proton conductive electrolyte membrane obtained is also a rough surface.

  The surface roughness of the support is not particularly limited, but the surface roughness Ra of the surface on which the dispersion liquid containing inorganic particles and organic particles is laminated is preferably 10.0 μm or less. Further, in order to prevent warping (curl), deflection, etc. of the support due to laminating a dispersion containing inorganic particles and organic particles, it is preferable to provide a backing layer on the surface opposite to the surface on which the dispersion is laminated. In some cases.

Examples of the inorganic particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), boron oxide (B ₂ O ₃ ), titania (TiO ₂ ), Ti, Al, B, Zr hydroxide is exemplified. These may be used alone or in combination of several kinds. In the present invention, silica (SiO ₂ ) is preferable. Further, among silica (SiO ₂ ), amorphous silica is preferable, and any of a dry method, a wet method, and an airgel method may be used, but a wet method of colloidal silica is more preferable.

  In the present invention, the average particle diameter of the inorganic particles is preferably 10 nm or more, more preferably 10 to 100 nm, still more preferably 10 to 50 nm. The average particle diameter of the inorganic particles can be determined by, for example, observing with a scanning electron microscope and measuring the long diameter of 200 particles randomly.

  As organic particles, organic particles of any material can be used as long as they finally disappear or disappear, but those that do not swell in a solvent as a dispersion medium used in the dispersion are preferable. In the present invention, an aqueous solvent is preferable as the dispersion medium, and examples of the organic particles include polymers such as acrylic resins, styrene resins, styrene / acrylic resins, styrene / divinylbenzene resins, polyester resins, and urethane resins. Beads can be used. In the present invention, the average particle size of the organic particles is preferably 10 to 450 nm, more preferably 100 to 300 nm.

  The inorganic porous film in the present invention is formed through a process of laminating a dispersion containing inorganic particles and organic particles and then firing, so that the inorganic particles are fixed and sintered to form a thin film at the same time. Primarily, the portion occupied by the organic particles forms pores in the thin film. In the present invention, the average pore diameter of the inorganic porous membrane is preferably 10 to 450 nm, and more preferably the average pore diameter is 100 to 300 nm. The average pore diameter can be determined by mercury porosimetry using, for example, a pore sizer 9320 manufactured by Shimadzu Corporation.

  In the present invention, the porosity of the inorganic porous membrane is preferably 40 to 95%, more preferably 50 to 80%.

The porosity can be calculated from the mass W (g) per unit area S (cm ² ), average thickness t (μm), and density d (g / cm ³ ) of the porous membrane by the following formula.

Porosity (%) = (1- (10 ⁴ · W / (S · t · d))) × 100
The porosity of the porous film is adjusted to the above range by using 5 to 60% by volume of inorganic particles and 40 to 95% by volume of organic particles (the sum of the volume of inorganic particles and organic particles is 1). can do.

  Next, a method for preparing a dispersion containing the inorganic particles and organic particles will be described.

  The use ratio of the inorganic particles and the organic particles is as described above, but the concentration of the dispersion is 5 to 80% by mass, preferably 10 to 40% by mass as the solid content concentration.

  As the dispersion medium, an aqueous solvent is preferable. Various known solvents such as water and alcohols can be used as the aqueous solvent, but water or a mixed solvent containing water as a main component is preferably used.

  Dispersing aids for dispersing inorganic particles and organic particles include, for example, higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxy Various surfactants such as alkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, and amine oxide can be used.

  Examples of the dispersion method include a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, and the like. be able to.

  In the step of laminating the dispersion liquid containing inorganic particles and organic particles, the dispersion liquid is filtered with a membrane filter using a vacuum suction filter, and a layer containing inorganic particles and organic particles is deposited on the membrane filter and dried. There are a method of stripping a membrane filter, a method of applying a dispersion to a support and drying. In the present invention, a method in which the dispersion is applied to a support is preferred. As a coating method, conventionally known coating methods such as a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, and an extrusion method can be employed.

  In order to form an inorganic porous film, a dispersion containing inorganic particles and organic particles is laminated and dried, or if the support is burnt out or melted away, the support is laminated on a support in a nitrogen atmosphere. What is necessary is just to heat-process in an electric furnace in inside. The heat treatment can be performed using, for example, an electric furnace including a heating element such as molybdenum silicide, and is performed at 1500 ° C. or less, more preferably at 400 to 1300 ° C. The time for heating can be appropriately set depending on the size of the target porous membrane. Specifically, for example, a heating time of about 5 to 24 hours can be used. When the heating time is long, the sintering proceeds and the average pore diameter may become small. The temperature increase rate and the temperature decrease rate in the heat treatment for obtaining the porous film can be appropriately set. It is preferable to set it as 100-300 degreeC / hour about both the temperature increase rate and temperature decrease rate. Moreover, it is also preferable to heat-process by dividing into temporary baking and main baking twice.

  The organic porous film containing the inorganic particles can be produced by the following method. First, the inorganic particles are sufficiently mixed with the organic film material and then made porous simultaneously with the film formation. The method for making the membrane porous is roughly classified into a stretching method (dry method) and an extraction method (wet method). In the extraction method, for example, a resin composition containing inorganic particles mixed with a filler or a plasticizer is extruded into a film shape, and then the filler and the plasticizer are extracted from the film to make the film porous. On the other hand, in the stretching method, the crystal structure is controlled in the process of melting and extruding a resin composition containing inorganic particles, and thereafter, pore formation is performed by generation and growth of craze accompanying stretching. Here, there is no restriction | limiting in particular regarding the porosity forming method in the manufacturing process of the organic porous membrane containing the inorganic particle which concerns on this invention, A porous membrane can be manufactured by any method.

  Examples of the resin used in the resin composition constituting the organic porous film containing inorganic particles include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4- Polyolefin resins such as homopolymers or copolymers of α-olefins such as methyl-1-pentene and 5-methyl-1-heptene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride Polymers, vinyl chloride resins such as vinyl chloride-olefin copolymers, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-perfluoro Oroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer Fluorine resin such as body, polyamide resin such as nylon 6 and nylon 66, etc. are used without limitation, but excellent in mechanical strength, chemical stability and chemical resistance, and familiar with proton conductive polymer It is preferable to use a polyolefin resin. As the polyolefin resin, polyethylene and polypropylene are particularly preferable.

  The inorganic particles contained in the organic porous membrane preferably have a portion of a large number of inorganic particles exposed on the surface that communicates with the outside air of the porous membrane pores. And the effect of suppressing the swelling of the proton conductive polymer contained in the pores can be imparted. Alternatively, when the exposed inorganic particle surface and the functional group in the polymer structure contained in the pore are physically or chemically bonded, an effect of suppressing the swelling of the proton conductive polymer contained in the pore can be imparted. Furthermore, in the case where a porous film is produced by forming the resin composition into a sheet shape and then uniaxially or biaxially stretching, peeling occurs at the interface between the matrix resin and the inorganic particles during the stretching. Therefore, it has an effect of controlling the properties of the formed holes.

  The inorganic particles contained in the resin composition are not particularly limited and are known inorganic particles, for example, at least one selected from the group consisting of Group IIA, Group IVA, Group IIIB, and Group IVB of the periodic table. Powders such as seed metal oxides, composite oxides, hydroxides, carbonates, sulfates, silicates, or mixtures thereof can be used.

Inorganic particles that can be suitably used in the present invention include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), boron oxide (B ₂ O ₃ ), titania (TiO ₂ ) and the like. Examples thereof include oxides and composite oxides thereof. These may be used alone or in combination of several kinds. In the present invention, silica (SiO ₂ ) is particularly preferable. Of the silica (SiO ₂ ), amorphous silica is preferable, and any of a dry method, a wet method, and an airgel method may be used, but a wet method of colloidal silica is more preferable.

  The particle size of the inorganic particles is preferably an average particle size of 10 nm or more, more preferably 10 to 100 nm, as a primary average particle size. The average particle diameter of the inorganic particles can be determined by, for example, observing with a scanning electron microscope and measuring the long diameter of 200 particles randomly.

  The compounding amount of the inorganic particles contained in the resin composition is preferably 1 to 50% by mass, expressed as mass% of the inorganic particles based on the total mass of the resin and the inorganic particles.

  The average pore diameter of the organic porous membrane containing the inorganic particles is preferably 10 to 1000 nm, more preferably the average pore diameter is 10 to 500 nm. More preferably, the average pore diameter is 10 to 100 nm. The average pore diameter can be determined by mercury porosimetry using, for example, a pore sizer 9320 manufactured by Shimadzu Corporation.

The porosity of the organic porous membrane containing the inorganic particles is preferably 40 to 95%, more preferably 50 to 80%. The porosity can be calculated from the mass W (g) per unit area S (cm ² ), average thickness t (μm), and density d (g / cm ³ ) of the porous membrane by the following formula.

Porosity (%) = (1- (10 ⁴ · W / (S · t · d))) × 100
The water absorption rate of the organic porous film containing the inorganic particles is preferably 200% or more. The water absorption means the amount of water absorption per dry mass of the sheet or film, and after immersing the sheet or film in ion-exchanged water for 4 hours or more, wipe the surface moisture with tissue paper etc., and the mass at the time of water absorption And then dried under reduced pressure at 60 ° C. for 5 hours, and the mass is determined by the formula of water absorption (%) = [(mass upon absorption−dry mass) / dry mass] × 100.

  The proton conductive polymer contained in the pores of the porous membrane in the present invention is not particularly limited. For example, (A) a polymer having a main chain composed of aliphatic hydrocarbon is added to a sulfonic acid group and / or phosphone. A polymer electrolyte into which an acid group has been introduced; (B) a polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group have been introduced into a polymer comprising an aliphatic hydrocarbon whose main chain is substituted with fluorine; and (C) a main chain. A polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group are introduced into a polymer having an aromatic ring, (D) a polymer such as polysiloxane or polyphosphazene substantially free of carbon atoms in the main chain, A polyelectrolyte having a sulfonic acid group and / or a phosphonic acid group introduced, and (E) selected from repeating units constituting the polymer before introduction of the sulfonic acid group and / or phosphonic acid group of (A) to (D). Any sulfonic acid group and / or a polymer electrolyte or the like by introducing a phosphonic acid group into two or more of a repeating unit copolymer.

  Here, “the sulfonic acid group and / or phosphonic acid group is introduced into the polymer” means “the sulfonic acid group and / or phosphonic acid group is introduced into the polymer skeleton via a chemical bond”.

  Examples of the polymer electrolyte (A) include polyvinyl sulfonic acid, polystyrene sulfonic acid, poly (α-methylstyrene) sulfonic acid, and the like.

  Examples of the polymer electrolyte (B) include perfluorocarbon sulfonic acid, perfluoroalkyl polymer having a phosphonic acid group (for example, J. Fluorine Chem., 82, 13 (1997)), polytrifluorostyrene sulfonic acid. And polytrifluorostyrenephosphonic acid (for example, J. New. Mater. Electrochem. Syst., 3, 43 (2000)).

  The polymer electrolyte (C) may be one in which the main chain is interrupted by a hetero atom such as an oxygen atom. For example, polyether ether ketone, polysulfone, polyether sulfone, poly (arylene ether) ), Polyphosphazene, polyimide, poly (4-phenoxybenzoyl-1,4-phenylene), polyphenylene sulfide, polyphenylquinoxalen, and other homopolymers introduced with sulfonic acid groups, aryl sulfonation Polybenzimidazole, alkylsulfonated polybenzimidazole, alkylphosphonated polybenzimidazole (for example, JP-A-9-110882), phosphonated poly (phenylene ether) (for example, J. Appl. Polym. Sci., 18, 1969 (1974) Etc. The.

  Examples of the polymer electrolyte of (D) above include Polymer Prep. , 41, no. Examples include polysiloxane having a phosphonic acid group described in 1,70 (2000).

  As the polymer electrolyte of the above (E), a sulfonic acid group and / or a phosphonic acid group is introduced into a random copolymer, but a sulfonic acid group and / or a phosphonic acid group is introduced into an alternating copolymer. Those having a sulfonic acid group and / or phosphonic acid group introduced into the block copolymer may be used. Examples of the sulfonic acid group introduced into the random copolymer include a sulfonated polyethersulfone-dihydroxybiphenyl copolymer (for example, JP-A-11-116679). An acid group and / or a phosphonic acid group is introduced as a block copolymer in which the main chain of all blocks is composed of an aliphatic hydrocarbon, for example, a styrene- (ethylene-butylene) -styrene triblock copolymer. Examples thereof include those obtained by introducing a sulfonic acid group and / or a phosphonic acid group into a polymer.

  Preferably, the polymer is an in-situ polymerized polymer after containing a monomer containing at least one proton dissociable group in the molecule in the porous membrane. More preferably, (a) a monomer having one or more proton dissociable groups in the molecule, and (b) a polymer obtained by copolymerization or reaction with a compound represented by the following general formula (1) as an essential constituent. is there. Further, it may be copolymerized with other unsaturated compounds that can be copolymerized therewith, and it is also a preferred embodiment that it is a polymer obtained by copolymerization by adding a reactive emulsifier in addition to the above essential components. One.

Here, the “proton dissociable group” means a functional group from which protons can be separated by ionization, the dissociable group is represented by the formula —XH, and X is an arbitrary group having a divalent bond. Any atom or atomic group may be used. Specifically, —OH, —OSO ₃ H, —COOH, —SO ₃ H, —OPO (OH) ₂ , —PO (OH) ₂ , —PH (OH) and the like can be mentioned. Particularly preferably _{-SO 3 H, -OPO (OH)} 2.

In the general formula (1), R ¹ represents an alkyl group having 4 or less carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, and a butyl group. R ² of the compound represented by the general formula (1) represents an organic group that can be copolymerized or reacted, and preferably at least one of an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an aminoalkyl group, or a vinyl group. An organic group containing seeds. m and n are both integers of 1 to 3. However, when m + n = 4 and m is 2 or 3, R ² may be the same or different.

  Specific examples of the compound represented by the general formula (1) include vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacrylic Loxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopro Rutrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane and the like. .

  The alkoxysilyl group of the compound represented by the general formula (1) reacts to form a crosslinked structure, or can be adsorbed or bonded to the surface of the inorganic particles contained in the porous film.

  The monomer having one or more proton dissociable groups in the molecule is preferably a compound having one or more sulfonic acid groups and one or more ethylenically unsaturated bonds in the molecule, such as allyl sulfonic acid, Methallylsulfonic acid, vinylsulfonic acid, p-styrenesulfonic acid, (meth) acrylic acid butyl-4-sulfonic acid, (meth) acryloxybenzenesulfonic acid, t-butylacrylamidesulfonic acid, 2-acrylamido-2-methyl Examples include propane sulfonic acid and isoprene sulfonic acid. The compounds having one or more sulfonic acid groups and one or more ethylenically unsaturated bonds in these molecules may be used alone or in combination of two or more.

Further, as the compound having one or more proton dissociable groups in the molecule, a haloalkylated and sulfonated polymer compound is preferable, and a polymer having an aromatic ring in the molecule is haloalkylated and sulfonated. Those are preferred. More preferably, a polymer compound known as an engineering plastic is haloalkylated and sulfonated. Engineering plastic has no general definition, and refers to a plastic with high elasticity and high strength that can be used as a structural material like metal. As an approximate concept, it is said that the elastic modulus is 2.45 × 10 ⁹ Pa or more and the thermal deformation temperature is 100 ° C. or more (see, for example, “Engineering Plastic” by Kazuo Kobayashi and Makio). However, natural resins such as polycarbonate and polyarylate have a modulus of elasticity of 1.96 × 10 ^{9 to} 2.45 × 10 ⁹ Pa, but they are treated as engineering plastic (“Engineering Plastics Handbook” edited by Suzuki Technical Office). reference).

Preferred examples of the polymer compound include polybenzazole (PBZ), polyaramid (PAR or Kevlar (registered trademark)), polybenzoxazole (PBO), polybenzothiazole (PBT), and polybenzimidazole (PBI). ), Polyparaphenylene terephthalimide (PPTA), polysulfone (PSU), polyimide (PI), polyphenylene oxide (PPO), polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO ₂ ), poly Paraphenylene (PPP), polyphenylquinoxaline (PPQ), polyaryl ketone (PK), polyether ketone (PEK), polyether sulfone (PES), polyether ether Sulfone (PEES), poly aryl sulfone, polyaryl ether sulfone (PAS), polyphenylsulfone (PPSU), polyphenylene sulfone (PPSO _2), polyetherimide, fluorinated polyimide, polyether ether ketone (PEEK), polyether ketone -Ketone (PEKK), polyetheretherketone-ketone (PEEKK), polyetherketoneetherketone-ketone (PEKEKK), and polystyrene (PS).

  These polymer compounds may be used alone or in combination of two or more. Particularly preferred is at least one selected from polyether ketone, polyether ether ketone, polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide, polyparaphenylene, polyphenylene oxide, polyimide, and polybenzimidazole.

  The polymer compound preferably has a molecular weight of 10,000 to 100,000, and any conventional compound can be used without any limitation.

  The method of haloalkylation and sulfonation of a polymer compound is, for example, by first dissolving the polymer compound in 90% or more, preferably 95% or more of sulfuric acid with stirring, and then adding a haloalkylation reagent thereto to sulfonate the polymer compound. And haloalkylation. In order to control the introduction of the sulfonic acid group into the polymer compound, it is generally preferable to dissolve it uniformly in the range of 0 to 100 ° C. When the temperature is high, the introduction ratio of the sulfonic acid group is high and the introduction ratio of the haloalkyl group is low. Conversely, when the temperature is low, the introduction of the sulfonic acid group is limited and the introduction ratio of the haloalkyl group is increased.

  Examples of the haloalkylating reagent used include chloromethyl methyl ether, bromomethyl methyl ether, iodomethyl methyl ether, chloroethyl ethyl ether, chloroethyl methyl ether, and the like. This method is a reaction in which sulfuric acid as a solvent is present in a large excess as a solvent, and the reaction rate is extremely fast. Therefore, while sufficiently stirring the sulfuric acid solution of the polymer compound sufficiently, the haloalkylating reagent is used. It is necessary to add. The amount of the haloalkyl group introduced into the polymer compound can also be controlled by the ratio between the number of moles of the haloalkylating reagent to be added and the number of moles of the unit into which the haloalkyl group of the polymer compound is introduced. Although the reaction proceeds very quickly, the reaction time is usually selected between 10 minutes and 16 hours. After the reaction, the remaining haloalkylating reagent is removed and removed by a nitrogen stream, and then poured into a large amount of water, precipitated, and washed thoroughly with water to obtain a haloalkylated and sulfonated polymer compound. be able to. The presence of haloalkyl groups and sulfonic acid groups can be confirmed by NMR analysis, elemental analysis, and the like.

  The reactive haloalkyl group can react with the compound represented by the general formula (1), and can form a crosslinked structure between the same kind of haloalkylated and sulfonated polymer compounds. Two or more haloalkylated and sulfonated polymer compounds may form a crosslinked structure. Such a polymer can improve the performance of the proton conducting polymer.

  Further, the monomer having one or more proton dissociable groups in the molecule is preferably a compound having one or more phosphate groups and one or more ethylenically unsaturated bonds in the molecule, and more preferably The compound represented by Formula (2) can be mentioned.

In the formula, R ³ represents a hydrogen atom or a methyl group, X represents a divalent organic group, and preferably an ethylene group or a propylene group. p represents an integer of 1 or more, preferably an integer of 1 to 10.

  Specific examples of the compound represented by the general formula (2) include methacryloyloxyethyl phosphate, methacryloyl di (oxyethylene) phosphate, methacryloyl tri (oxyethylene) phosphate, methacryloyl tetra (oxyethylene) phosphate, methacryloyl penta (oxyethylene). ) Phosphate, methacryloyl hexa (oxyethylene) phosphate, methacryloyloxypropyl phosphate, methacryloyl di (oxypropyl) phosphate, methacryloyl tri (oxypropyl) phosphate, methacryloyl tetra (oxypropyl) phosphate, methacryloyl penta (oxypropyl) phosphate, methacryloyl hexa (Oxypropyl) phosphate, acryloyloxyethyl phosphate , Acryloyl di (oxyethylene) phosphate, acryloyl tri (oxyethylene) phosphate, acryloyl tetra (oxyethylene) phosphate, acryloyl penta (oxyethylene) phosphate, acryloyl hexa (oxyethylene) phosphate, acryloyloxypropyl phosphate, acryloyl di (Oxypropyl) phosphate, acryloyl tri (oxypropyl) phosphate, acryloyl tetra (oxypropyl) phosphate, acryloyl penta (oxypropyl) phosphate, acryloyl hexa (oxypropyl) phosphate, 4-styrylmethoxybutyl phosphate .

  Specific examples include “PhosmerM”, “PhosmerCL”, “PhosmerA”, “PhosmerPE”, “PhosmerPP” (manufactured by Unichemical Co., Ltd.) and the like, but are not limited thereto. These compounds may be used alone or in combination of two or more.

  Examples of other unsaturated compounds that can be copolymerized include unsaturated compounds having one or more ethylenically unsaturated bonds in the molecule. Among them, (meth) acrylonitrile, (meth) Acrylic esters and substituted or unsubstituted styrenes are preferred. Furthermore, ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, hexamethylenediol di (meth) acrylate, divinylbenzene, N, N, which contains a plurality of ethylenically unsaturated bonds in one molecule. -Methylenebisacrylamide or the like preferably forms a cross-linked structure and is used for improving the durability of the electrolyte membrane.

  As the reactive emulsifier, an anionic and / or nonionic emulsifier having at least one unsaturated double bond in the molecule is preferably used. The reactive emulsifier is preferably a compound having at least one hydrophobic group, hydrophilic group and reactive group in the molecule. The hydrophobic group comprises an aliphatic or aromatic hydrocarbon group. Contains nonionic groups typified by oxyalkylene ether groups, anionic groups typified by sulfonates, carboxylates and phosphates, the reactive groups are vinyl ether groups, allyl ether groups, vinyl phenyl groups, Those containing an allylphenyl group, an ester or amide group of acrylic acid or methacrylic acid, or an ester or amide group of an unsaturated dibasic acid such as maleic acid are preferred.

  Examples of the reactive emulsifier include, for example, JP-A-62-22803, JP-A-62-2104802, JP-A-62-2104803, JP-A-62-221431, JP-A-62-221432, and JP-A-62-2225237. Nos. 62-244430, 62-286528, 62-289228, 62-289229, 63-12334, 63-54930, 63-77530 Gazette, 63-77531, 63-77532, 63-84624, 63-84625, 63-126535, 63-126536, 63-147530 63-139035, JP-A-1-11630, 1-222338, 1 No. 22627, No. 1-2628, No. 1-33062, No. 1-334430, No. 1-33441, No. 1-34342, No. 1-99638, No. 1-99639 No. 4-50204, No. 4-53802, and No. 4-55401.

  Examples of the reactive emulsifier compound include, for example, 1- (meth) allyloxy-2-hydroxypropane, (meth) acryloyloxy-2-hydroxypropane, (meth) allyloxycarbonylmethyl-3-alkoxy (polyoxy) Alkylenoxy) -2-hydroxypropane, alkylphenoxy (polyoxyalkylenoxy) -2-hydroxypropane or acyloxy (polyoxyalkylenoxy) -2-hydroxypropane or an alkylene oxide adduct thereof, or sulfuric acid or phosphorus thereof. Alkylene oxide adducts of acid esters or salts thereof, bisphenol compounds or glycol compounds or sulfuric acid or phosphate esters or salts thereof, alkylene oxide adducts of vinyl or allylphenol compounds, or These sulfuric acid or phosphoric acid ester or a salt thereof, monoallyl of sulfosuccinic acid - mono alkyl ester or a salt thereof, the sulfosuccinic acid mono (3-allyloxy-2-hydroxypropyl) - monoalkyl esters or salts thereof.

  Specifically, “Adekaria soap NE”, “Adekaria soap SE”, “Adekaria soap ER”, “Adekaria soap SR”, “Adekaria soap PP”, “Adekaria soap PPE” (Asahi Denka ( Co., Ltd.), “AQUALON KH”, “AQUALON HS”, “AQUALON BC”, “AQUALON RN”, “NEW FRONTIER” (Daiichi Kogyo Seiyaku Co., Ltd.), “ELEMINOL ES”, “ELEMINOL JS”, Examples thereof include, but are not limited to, “Eleminol RS”, “Eleminol MON”, “Eleminol HA” (manufactured by Sanyo Chemical Industries), “Latemuru” (manufactured by Kao Corporation), and the like. These reactive emulsifiers may be used alone or in combination of two or more.

  The method of containing the proton conductive polymer in the pores of the porous membrane in the present invention is not particularly limited. For example, the method of applying the proton conductive polymer solution to the porous membrane, The proton conductive polymer can be contained in the pores of the porous membrane by a method of immersing in a proton conductive polymer solution. At that time, the proton conductive polymer can be easily contained in the pores by using ultrasonic waves or reducing the pressure.

  Preferably, a precursor of a proton conductive polymer ((a) a monomer having one or more proton dissociable groups in the molecule, (b) a compound represented by the general formula (1), and other copolymerizable compounds Of the unsaturated compound, reactive emulsifier, and the like) and a polymerization initiator in the pores of the porous membrane, and by a suitable method conventionally known such as thermal polymerization or photopolymerization, In— This is a method of forming a proton conductive polymer by in situ polymerization or in-situ reaction.

  At that time, the solution containing the precursor of the proton conductive polymer and the polymerization initiator can be easily contained in the pores by using ultrasonic waves or reducing the pressure. After hydrophilizing the pore surface of the porous membrane, a solution containing the precursor of the proton conductive polymer and the polymerization initiator is contained in the pores of the porous membrane, and in-situ polymerization or in-situ polymerization is performed. A method of reacting is also preferred. It is also preferable to adjust the viscosity of the solution containing the proton conductive polymer precursor and the polymerization initiator as appropriate so that the solution is easily contained in the pores. That is, in order to increase the viscosity, a part of the monomer may be prepolymerized, or a small amount of an appropriate polymer may be added and dissolved. On the contrary, in order to lower the viscosity, a suitable solvent may be added for dilution.

As a method of reacting the haloalkylated and sulfonated polymer compound, the compound represented by the general formula (1), the reactive emulsifier, etc., a method of cleaving haloalkyl to react, a polymerization initiator is used. A method of reacting an unsaturated bond, a method of reacting a silyl group, and the like are preferably used. As a method of cleaving and reacting a haloalkyl group, a method of ionically cleaving with a protonic acid such as Lewis acid, HF, H ₂ SO ₄ , H ₃ PO ₄ , or a radical by light such as ultraviolet rays or electron beams, or heat. A method of cleaving is used, but a method using light or heat is preferred.

  What is necessary is just to use what is conventionally known as said polymerization initiator suitably. A thermal polymerization initiator or a photopolymerization initiator is preferable, and the thermal polymerization initiator is a compound capable of generating a polymerizable radical by applying thermal energy. Examples of such compounds include azobisnitrile compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobispropionitrile, benzoyl peroxide, lauroyl peroxide, and acetyl peroxide. , T-butyl perbenzoate, α-cumyl hydroperoxide, di-t-butyl peroxide, diisopropyl peroxydicarbonate, t-butyl peroxyisopropyl carbonate, peracids, alkyl peroxycarbamates, nitrosoaryl acyl Organic peroxides such as amines, inorganic peroxides such as potassium persulfate, ammonium persulfate and potassium perchlorate, diazoaminobenzene, p-nitrobenzenediazonium, azobis-substituted alkanes, diazothioethers, arylazosulfones, etc. Of azo or diazo Nitrosophenylurea, tetramethylthiuram disulfide, diaryl disulfides, dibenzoyl disulfide, tetraalkylthiuram disulfides, dialkylxanthogenic disulfides, arylsulfinic acids, arylalkylsulfones, 1-alkanesulfinic acids, etc. it can.

  Among these, particularly preferred are compounds that are excellent in stability at normal temperature and have a fast decomposition rate during heating, and the initiator is preferably 0.1 to 30% by mass in the total polymerizable composition. The range of 0.5-20 mass% is more preferable.

As photopolymerization initiators, adjacent polyketone compounds represented by R— (CO) _x —R ′ (R, R ′ = hydrogen or hydrocarbon group, x = 2 to 3) (for example, diacetyl, dibenzyl, etc.) , Carbonyl alcohols represented by R—CO—CHOH—R ′ (R, R ′ = hydrogen or hydrocarbon group) (for example, benzoin etc.), R—CH (OR ″) — CO—R ′ (R, R ', R ″ = hydrocarbon group) represented by acyloin ethers (for example, benzoin methyl ether), Ar—CR (OH) —CO—Ar (Ar = aryl group, R = hydrocarbon group) Examples thereof include substituted acyloins (for example, α-alkylbenzoin) and polynuclear quinones (for example, 9,10-anthraquinone). These photopolymerization initiators can be used alone or in combination.

  The usage-amount of a photoinitiator is the range of 0.5-5 mass% with respect to the total mass of an unsaturated compound, Preferably it is the range of 1-3 mass%.

  The ion exchange capacity of the proton conducting polymer according to the present invention is preferably 0.5 to 5.0 meq / g dry resin, more preferably 1.0 to 4.5 meq / g dry resin. is there. When the ion exchange capacity is smaller than 0.5 meq / g dry resin, the ion conduction resistance increases, and when it is greater than 4.5 meq / g dry resin, the ion exchange capacity is easily dissolved in water.

The ion exchange capacity can be determined by the following measurement method. First, the proton conductive polymer is immersed in a 2 mol / L sodium chloride aqueous solution for about 5 minutes to replace the proton of the acidic group with sodium. Neutralization titration with sodium hydroxide of known concentration is performed on protons liberated in the solution by sodium substitution. Then, the amount of protons (H ⁺ ) is calculated from the dry mass (W) of the proton conductive polymer and the volume (V) of sodium hydroxide required for neutralization titration, and the ion exchange capacity (meq / g) according to the following formula: ) The following formula shows an example when neutralization titration is performed with a 0.05 mol / L NaOH aqueous solution.

Ion exchange capacity (meq / g) = H ⁺ /W=(0.05 V × 10 ⁻³ / W) × 10 ³
The average film thickness of the proton conductive electrolyte membrane of the present invention is not particularly limited, but is usually 500 μm or less, preferably 300 μm or less, more preferably 50 to 200 μm. The film thickness can be measured with a 1/10000 thickness gauge. The average film thickness can be obtained by measuring five points at arbitrary locations and calculating the average.

  The proton conductive electrolyte membrane of the present invention can be used for a fuel cell. Among the fuel cells, a methanol fuel cell is preferable, and a direct methanol fuel cell is particularly preferable.

  Next, a direct methanol fuel cell will be described with reference to FIG. FIG. 1 is a schematic view showing an embodiment of a direct methanol fuel cell using the proton conductive electrolyte membrane of the present invention as an electrolyte membrane.

  In FIG. 1, reference numeral 1 denotes an electrolyte membrane, reference numeral 2 denotes an anode electrode (fuel electrode), reference numeral 3 denotes a cathode electrode (air electrode), and reference numeral 4 denotes an external circuit. A methanol aqueous solution A is used as the fuel.

At the anode 2, methanol reacts with water to generate carbon dioxide and hydrogen ions (H ⁺ ) and release electrons (e ⁻ ). Hydrogen ions (H ⁺ ) pass through the electrolyte 1 to the cathode electrode 3, and electrons (e ⁻ ) flow to the external circuit 4. On the other hand, the aqueous solution A ′ in which the methanol component containing carbon dioxide is reduced is discharged out of the system. The reaction at the anode 2 is represented by the following formula.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
At the cathode 3, oxygen in the air B reacts with hydrogen ions (H ⁺ ) that have passed through the electrolytic membrane 1 and electrons (e ⁻ ) that have come from the external circuit 4 to generate water. On the other hand, the air B ′ in which oxygen containing water is reduced is discharged out of the system. The reaction at the cathode electrode 3 is represented by the following formula.

3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
The overall reaction of the fuel cell is as follows:

CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O
The structure of the anode 2 can be a conventionally known structure. For example, it is comprised from the support body which supports a catalyst layer and a catalyst layer from the electrolyte 1 side. The structure of the cathode electrode 3 can also be a conventionally known structure. For example, it is comprised from the support body which supports a catalyst layer and a catalyst layer from the electrolyte 1 side.

  As the catalyst for the anode electrode 2 and the cathode electrode 3, known catalysts can be used. For example, a noble metal catalyst such as platinum, palladium, ruthenium, iridium, gold, or an alloy such as platinum-ruthenium, iron-nickel-cobalt-molybdenum-platinum, or the like is used.

  The catalyst layer preferably contains an electron conductor (conductive material) material for the purpose of improving conductivity. The electron conductor (conductive material) is not particularly limited, but an inorganic conductive material is preferably used from the viewpoints of electron conductivity and touch resistance. Among these, carbon black, graphite and carbonaceous carbon materials, metals and metalloids are mentioned. Here, as the carbon material, carbon black such as channel black, thermal black, furnace black, and acetylene black is preferably used in view of electron conductivity and specific surface area. In particular, an electron conductor (conductive material) that supports a catalyst such as platinum-supported carbon is preferably used.

  As a method for producing a membrane-electrode assembly (MEA) by joining a solid polymer electrolyte membrane and an electrode, for example, a polytetrafluoroethylene suspension of platinum catalyst powder supported on carbon particles is used. There is a method in which a catalyst layer is formed by mixing with a carbon paper, heat-treating to form a catalyst layer, applying the same electrolyte solution as the electrolyte membrane to the catalyst layer, and hot-pressing with the electrolyte membrane for integration. In addition, a method in which the same electrolyte solution as the electrolyte membrane is coated on platinum catalyst powder in advance, a method in which a catalyst paste is applied to the electrolyte membrane, a method in which an electrode is electrolessly plated on the electrolyte membrane, and a metal complex ion of white metal on the electrolyte membrane There is a method of reducing after adsorbing.

  A fuel distribution plate (separator) as a current collector in which grooves for forming a fuel flow path and an oxidant flow path are formed outside the joined body of the electrolyte membrane and the electrode produced as described above, and an oxidant A fuel cell by arranging a single cell with a flow distribution plate (separator) and laminating a plurality of single cells via a cooling plate or arranging a plurality of single cells on a plane (planar lamination). Is configured.

  The present invention will be described in more detail based on examples, but the present invention is not limited to the examples.

Example 1
<Preparation of porous membrane>
<Porous membrane no. 1 production>
A mixture of polystyrene fine particles (Molytex 5008B, average particle size 80 nm) and colloidal silica (Nissan Chemical Snowtex 50, primary average particle size 20 nm) (polystyrene fine particles 80% by mass, colloidal silica 20% by mass) is diluted with a diluted interface. The mixture was stirred and dispersed in the aqueous activator solution using a high-speed homogenizer. The concentration of the dispersion was set to 20% by mass. Each dispersion was applied onto a polyethylene terephthalate support using a bar coater so that the film thickness after drying was 150 μm, dried, and after drying, the polyethylene terephthalate support was peeled off, and the temperature increase rate was 60 ° C. / The temperature was raised to 600 ° C. for 3 hours, and after preliminary firing at 600 ° C. for 3 hours, the temperature was raised to 1000 ° C. at a heating rate of 120 ° C./hour and then fired at 1000 ° C. for 3 hours. 1 was produced.

<Porous membrane no. Preparation of 2, 3>
Porous membrane no. 1 except that the polystyrene fine particles and colloidal silica were replaced as shown in Table 1. In the same manner as in No. 1, the inorganic porous membrane No. 1 2 and 3 were produced.

  However, when the average particle diameter of polystyrene fine particles was 220 nm and 430 nm, 5022B and 5043B manufactured by Moritex Corporation were used, respectively. Moreover, the ones with colloidal silica primary average particle diameters of 50 nm and 100 nm used Snowtex YL and Snowtex MP manufactured by Nissan Chemical Co., respectively.

<Porous membrane no. Preparation of 4>
Organic porous material containing inorganic particles obtained by making a resin composition obtained by mixing colloidal silica (Snowtex 50, Nissan Chemical Co., Ltd., primary average particle size 20 nm) with polyethylene (weight average molecular weight 300,000) as inorganic particles with polyethylene (weight average molecular weight 300,000). Membrane No. 4 was produced.

<Porous membrane no. Preparation of 5, 6>
Porous membrane no. 4 except that the colloidal silica was changed as shown in Table 1, the porous membrane No. In the same manner as in No. 4, the organic porous membrane no. 5 and 6 were produced.

  However, silica having a primary average particle diameter of 50 nm and 100 nm were taken out from Snowtex YL and Snowtex MP manufactured by Nissan Chemical Co., respectively.

Porous membrane no. Table 1 shows the average pore diameter and porosity of 1-6. The porosity was calculated by the following equation from the mass W (g) per unit area S (cm ² ), the average thickness t (μm), and the density d (g / cm ³ ).

Porosity (%) = (1- (10 ⁴ · W / (S · t · d))) × 100
The average pore diameter was measured by a mercury intrusion method using a pore sizer 9320 manufactured by Shimadzu Corporation.

[Production of proton conducting electrolyte membrane]
[Proton conducting electrolyte membrane No. Production of 1]
Porous membrane No. produced above. 1 contained a proton conducting polymer by the following method to produce a proton conducting electrolyte membrane (electrolyte membrane No. 1).

  In isopropyl alcohol: water = 2: 1, acrylic acid, 3-glycidoxypropyltrimethoxysilane, “Aqualon KH-05” (Daiichi Kogyo Seiyaku Co., Ltd.), and N, N-methylene as a cross-linking agent Bisacrylamide and AIBN (2,2′-azobisisobutyronitrile) as a polymerization initiator are mixed at a mass ratio of 100: 20: 20: 5: 1, and the mixture is porous under reduced pressure. The membrane was immersed. The porous membrane thus treated was sandwiched and heated between roughened polyethylene terephthalate films, held at 60 ° C. for 2 hours, and further held at 80 ° C. for 2 hours to produce a proton conductive electrolyte membrane. . The average film thickness of the proton conductive electrolyte membrane was 150 μm. The average film thickness was obtained by measuring five arbitrary points with a thickness gauge and calculating the average.

  The surface roughness Ra of the proton conductive electrolyte membrane was measured with a laser microscope (VK-8500) manufactured by Keyence Corporation with a reference length of 2.5 mm and a cutoff value of 0.8 mm. The results are shown in Table 2.

[Proton conducting electrolyte membrane No. Production of 2, 3]
Proton conductive electrolyte membrane No. 1 except that the composition of the porous membrane and the proton conducting polymer was changed as shown in Table 2, and the surface-roughened polyethylene terephthalate film used for the sandwiching was different, and the surface roughness of the electrolyte membrane was controlled. , Proton conductive electrolyte membrane No. In the same manner as in No. 1, proton conductive electrolyte membrane No. 1 2 and 3 were produced. Table 2 shows the measured surface roughness Ra of the proton conductive electrolyte membrane.

[Proton conducting electrolyte membrane No. Production of 4]
Porous membrane No. produced above. 2 contained a proton conductive polymer by the following method to produce a proton conductive electrolyte membrane (electrolyte membrane No. 4).

  In isopropyl alcohol: water = 2: 1, 2-acrylamido-2-methylpropanesulfonic acid, 3-glycidoxypropyltrimethoxysilane, “Aqualon KH-05” (Daiichi Kogyo Seiyaku Co., Ltd.), and N, N-methylenebisacrylamide as a cross-linking agent and AIBN (2,2'-azobisisobutyronitrile) as a polymerization initiator are mixed at a mass ratio of 100: 15: 5: 5: 1, and the pressure is reduced. Below, the porous membrane was immersed in the mixed solution. The porous membrane thus treated was sandwiched and heated between roughened polyethylene terephthalate films, held at 60 ° C. for 2 hours, and further held at 80 ° C. for 2 hours to produce a proton conductive electrolyte membrane. . The average film thickness of the proton conductive electrolyte membrane was 150 μm. The average film thickness was obtained by measuring five arbitrary points with a thickness gauge and calculating the average. The surface roughness Ra of the proton conductive electrolyte membrane is the same as that of the electrolyte membrane No. Measurement was performed in the same manner as in 1. The results are shown in Table 3.

[Proton conducting electrolyte membrane No. Production of 5, 6]
Proton conductive electrolyte membrane No. 4 except that the composition of the porous membrane and the proton conducting polymer was changed as shown in Table 3, and the surface-roughened polyethylene terephthalate film used for the sandwiching was different and the surface roughness of the electrolyte membrane was controlled. , Proton conductive electrolyte membrane No. In the same manner as in No. 4, the proton conductive membrane No. 5 and 6 were produced. Table 3 shows the measured surface roughness Ra of the proton conductive electrolyte membrane.

[Proton conducting electrolyte membrane No. 7)
Porous membrane No. produced above. A proton conducting polymer was contained in the porous membrane 1 by the following method to produce a proton conducting electrolyte membrane (electrolyte membrane No. 7).

  In N, N-dimethylacetamide, chloromethylated and sulfonated polyetheretherketone and 3-glycidoxypropyltrimethoxysilane are mixed at a mass ratio of 100: 15, and the mixture is mixed under reduced pressure. The porous membrane was immersed. The porous membrane thus treated was sandwiched and heated between roughened polyethylene terephthalate films, and held at 100 ° C. for 5 hours to produce a proton conductive electrolyte membrane. The average film thickness of the proton conductive electrolyte membrane was 150 μm. The average film thickness was obtained by measuring five arbitrary points with a thickness gauge and calculating the average. The surface roughness Ra of the proton conductive electrolyte membrane is the same as that of the electrolyte membrane No. Measurement was performed in the same manner as in 1. The results are shown in Table 4.

[Proton conducting electrolyte membrane No. Production of 8, 9]
Proton conductive electrolyte membrane No. 7 except that the composition of the porous membrane and the proton conductive polymer was changed as shown in Table 4, and the surface-roughened polyethylene terephthalate film used for the sandwiching was different, and the surface roughness of the electrolyte membrane was controlled. , Proton conductive electrolyte membrane No. In the same manner as in FIG. 8 and 9 were produced. Table 4 shows the measured surface roughness Ra of the proton conductive electrolyte membrane.

[Proton conducting electrolyte membrane No. 10 production)
Porous membrane No. produced above. A proton conductive polymer was contained in the porous membrane 1 by the following method to produce a proton conductive electrolyte membrane (electrolyte membrane No. 10).

  In isopropyl alcohol: water = 2: 1, “Phosmer M” (manufactured by Unichemical Co., Ltd.), 3-glycidoxypropyltrimethoxysilane, 2-acrylamido-2-methylpropanesulfonic acid, “AQUALON KH-05” (By Daiichi Kogyo Seiyaku Co., Ltd.), and N, N-methylenebisacrylamide as a crosslinking agent and AIBN (2,2′-azobisisobutyronitrile) as a polymerization initiator in a mass ratio of 100: 15: It mixed so that it might become 100: 5: 5: 1, and the porous membrane was immersed in the liquid mixture under pressure reduction. The porous membrane thus treated was sandwiched and heated between roughened polyethylene terephthalate films, held at 60 ° C. for 2 hours, and further held at 80 ° C. for 2 hours to produce a proton conductive electrolyte membrane. . The average film thickness of the proton conductive electrolyte membrane was 150 μm. The average film thickness was obtained by measuring five arbitrary points with a thickness gauge and calculating the average. The surface roughness Ra of the proton conductive electrolyte membrane is the same as that of the electrolyte membrane No. Measurement was performed in the same manner as in 1. The results are shown in Table 5.

[Proton conducting electrolyte membrane No. 11, 12)
Proton conductive electrolyte membrane No. 10 except that the composition of the porous membrane and the proton conductive polymer was changed as shown in Table 5, and the surface-roughened polyethylene terephthalate film used for the sandwiching was different and the surface roughness of the electrolyte membrane was controlled. , Proton conductive electrolyte membrane No. In the same manner as in No. 10, the proton conductive membrane No. 11 and 12 were produced. Table 5 shows the measured surface roughness Ra of the proton conductive electrolyte membrane.

[Proton conducting electrolyte membrane No. Production of 13-16]
As a comparison, the proton conductive electrolyte membrane No. 1, the presence or absence of inclusion in the porous membrane and the composition of the proton conductive polymer were changed as shown in Table 6, and the roughened polyethylene terephthalate films used for sandwiching were different from each other, and the surface of the electrolyte membrane was used. Except for controlling the roughness, the proton conductive electrolyte membrane No. In the same manner as in No. 1, proton conductive electrolyte membrane No. 1 13-16 were produced. Table 6 shows the measured surface roughness Ra of the proton conductive electrolyte membrane.

[Evaluation of proton conducting electrolyte membrane]
<Proton conductivity>
The produced proton conductive electrolyte membrane No. 1-12, comparative proton conductive electrolyte membrane No. 13 to 16 were water-containing in water (25 ° C.), and then sandwiched between two platinum electrodes. Impedance was measured using an LCR meter HP4284A manufactured by Hewlett-Packard, and proton conductivity was calculated.

<Methanol permeability>
The proton conductive electrolyte membrane No. 1 prepared in the H-type cell of FIG. 1 to 12 and a proton conductive electrolyte membrane No. 1 as a comparative sample. The amount of methanol permeated into the pure water of the B cell from the 2 mol / L aqueous methanol solution placed in the A cell by sandwiching an arbitrary porous membrane of 13 to 16 by gas chromatography (GC-14B) manufactured by Shimadzu Corporation It was measured. The results are shown in Table 7.

  From the results in Table 7, it can be seen that the proton conductive electrolyte membranes (Nos. 1 to 12) of the present invention have high proton conductivity and low methanol permeability. Among the comparative proton conductive electrolyte membranes (Nos. 13 to 16), No. It can be seen that 14 to 16 have high proton conductivity but have a drawback of high methanol permeability.

[Fabrication and evaluation of fuel cells]
The produced proton conductive electrolyte membrane No. 1-12, comparative proton conductive electrolyte membrane No. Membrane-electrode assemblies (MEA) using 13 to 16 were prepared and evaluated by the following methods.

<Production of electrode>
The carbon fiber cloth substrate was subjected to water repellent treatment with polytetrafluoroethylene (PTFE), and then a carbon black dispersion containing 20% by mass of PTFE was applied and baked to prepare an electrode substrate. On this electrode substrate, an anode electrode catalyst coating solution composed of Pt—Ru-supported carbon and Nafion (DuPont) solution is applied and dried to form an anode electrode, and Pt-supported carbon and Nafion (DuPont) solution. A cathode electrode catalyst coating liquid consisting of was applied and dried to produce a cathode electrode.

<Production of membrane-electrode assembly (MEA)>
The produced proton conductive electrolyte membrane No. 1-12, comparative proton conductive electrolyte membrane No. 13 to 16 are respectively held by an anode electrode and a cathode electrode and heated and pressed to form a membrane-electrode assembly (MEA) MEA-No. 1-16 were produced.

<Evaluation of current-voltage characteristics>
The produced membrane-electrode assembly (MEA) was sandwiched between separators, and a fuel cell was operated by flowing a 3% methanol aqueous solution on the anode side and air on the cathode side, and current-voltage characteristics were evaluated. Table 8 shows the current density at a voltage of 0.4V.

<Evaluation of bondability>
After the evaluation of the current-voltage characteristics, a continuous power generation test for 250 hours was performed under the same conditions, the fuel cell was disassembled, and the membrane-electrode assembly (MEA) was visually observed. No peeling or the like was observed, and good bondability (◯), partial peeling was observed (Δ), and peeling was observed in several places, which were evaluated as poor bonding (x). The results are shown in Table 8.

  From the results in Table 8, it can be seen that the membrane-electrode assembly (MEA) according to the present invention has a higher current density than the comparative membrane-electrode assembly (MEA). Furthermore, it turns out that bondability is favorable.

It is the schematic which shows one Embodiment of the direct methanol type solid polymer fuel cell of this invention. It is the schematic of the H-type cell for evaluating methanol permeability.

Explanation of symbols

1 Electrolyte membrane 2 Anode electrode (fuel electrode)
3 Cathode electrode (air electrode)
4 External circuit

Claims (7)

A proton conductive electrolyte membrane containing a proton conductive polymer in the pores of the porous membrane, wherein an arithmetic average roughness Ra according to JIS B 0601 of the electrolyte membrane surface is 0.5 to 10.0 μm A proton conductive electrolyte membrane. The proton conductive electrolyte membrane according to claim 1, wherein the porous membrane is an inorganic porous membrane. The proton conductive electrolyte membrane according to claim 1, wherein the porous membrane is an organic porous membrane containing inorganic particles. A polymer electrolyte fuel cell comprising a cathode electrode, an anode electrode, and an electrolyte sandwiched between the electrodes, wherein the proton conductive electrolyte membrane according to any one of claims 1 to 3 is used as the electrolyte. Solid polymer fuel cell. A method for producing a proton conductive electrolyte membrane containing a proton conductive polymer in the pores of a porous membrane, wherein the arithmetic average roughness Ra of the electrolyte membrane surface according to JIS B 0601 is 0.5 to 10.0 μm A method for producing a proton conductive electrolyte membrane, characterized by comprising: The proton conductive polymer in the pores is produced by containing a monomer containing one or more proton dissociable groups in at least a molecule in the pores, and then in-situ polymerization. The method for producing a proton conductive electrolyte membrane according to claim 5. The proton conductive polymer in the pore contains a monomer containing at least one proton dissociable group in the pore and a compound represented by the following general formula (1), and then In 6. The method for producing a proton-conducting electrolyte membrane according to claim 5, wherein the method is produced by -situ polymerization.

(In the formula, R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents a copolymerizable or reactive organic group, and m and n are each an integer of 1 to 3, provided that m + n = 4. And when m is 2 or 3, R ² may be the same or different.)

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