JPWO2006051943A1 - Proton-conducting electrolyte membrane, method for producing proton-conducting electrolyte membrane, and polymer electrolyte fuel cell - Google Patents

Abstract

A proton conductive electrolyte membrane having a pore-containing inorganic porous membrane filled with a proton conductive polymer, wherein the proton conductive polymer is a haloalkylated and sulfonated polymer compound and the following general formula: A proton conductive electrolyte membrane which is a reaction product with the compound represented by (1). It is possible to provide a proton conductive electrolyte membrane having a sufficiently high proton conductivity and a sufficiently low methanol permeability, a method for producing the same, and a polymer electrolyte fuel cell using the proton conductive electrolyte membrane. Wherein R 1 represents an alkyl group having 4 or less carbon atoms, R 2 represents an arbitrary organic group, and m and n are all integers of 1 to 3, provided that m + n = 4 , When m is 2 or 3, R2 may be a different organic group.)

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 and the electrolyte is solid (polymer thin film). The polymer electrolyte fuel cell includes a hydrogen fuel 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 Polymer 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 conductive 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, a sulfonic acid group-containing fluororesin membrane represented by Nafion (registered trademark) manufactured by DuPont has been studied for use as an electrolyte in a portable fuel cell.

  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, various methods for obtaining a proton conductive membrane by impregnating a porous membrane having pores with a proton conductive polymer have been proposed.

  Improved dimensional stability, handleability, and uncompromised ion conductivity and reactant gas crossover compared to conventional unreinforced ion exchange membranes of the same polymer and comparable thickness For the purpose of providing an ion exchange membrane, a composite membrane is disclosed in which an ion conductive polymer is embedded in a porous support formed of randomly oriented individual fibers (see, for example, Patent Document 1). .)

  In addition, 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 free from methanol and water. An electrolyte membrane is disclosed in which pores of a porous base material that does not swell are filled with a polymer having proton conductivity (see, for example, Patent Document 2). As the porous substrate, an inorganic material such as ceramic, glass or alumina, or a heat resistant polymer such as polytetrafluoroethylene or polyimide is used. It is described that the porosity of the porous substrate is preferably 10 to 95%, the average pore diameter is 0.001 to 100 μm, and the thickness is preferably on the order of several μm.

  In addition, for the purpose of providing a proton conductive membrane having durability and mechanical strength, a polymer having a phosphoric acid group, a phosphonic acid group or a phosphinic acid group in the side chain is supported in the pores of the porous membrane. A proton conductive membrane is disclosed (for example, see Patent Document 3). Examples of the porous membrane include ultra high molecular weight polyolefin resin and fluororesin. It is described that the porosity of the porous film is preferably 30 to 85%, the average pore diameter is preferably 0.005 to 10 μm, and the thickness is preferably 5 to 500 μm.

Further, for the purpose of suppressing the permeation (crossover) of methanol as much as possible, an electrolyte membrane in which regularly arranged pores of an inorganic porous substrate are filled with a polymer having proton conductivity is disclosed (for example, non-porous). (See Patent Document 1).
Japanese Patent Laid-Open No. 10-312815 International Publication No. 00/54351 Pamphlet JP 2002-83514 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 important that at least the proton conductivity is sufficiently high and the methanol permeability is sufficiently low.

  Accordingly, a first object of the present invention is to provide a proton conductive electrolyte membrane having sufficiently high proton conductivity and sufficiently low methanol permeability, and a proton conductive electrolyte membrane having such excellent performance. It is in providing the manufacturing method of.

  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.
1. A proton conductive electrolyte membrane having a pore-containing inorganic porous membrane filled with a proton conductive polymer, wherein the proton conductive polymer is a haloalkylated and sulfonated polymer compound and the following general formula: A proton conductive electrolyte membrane which is a reaction product with the compound represented by (1).

(Wherein R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents an arbitrary organic group, and m and n are each an integer of 1 to 3, provided that m + n = 4, m When R is 2 or 3, R ² may be a different organic group.)
2. The proton conductive polymer is a reaction product of the haloalkylated and sulfonated polymer compound, the compound represented by the general formula (1) according to claim 1, and a reactive emulsifier. 2. The proton-conducting electrolyte membrane according to 1, wherein
3. A step of holding the inorganic particles and the organic particles on a support using a dispersion liquid containing inorganic particles and organic particles, and the inorganic particles, the organic particles and the support after the steps; 3. The proton conductive electrolyte membrane according to 1 or 2, which is an inorganic porous membrane obtained through a step of firing the body.
4). 4. The proton conductive electrolyte membrane according to 3, wherein the inorganic particles have a primary average particle size of 10 to 100 nm.
5. The polymer compound is at least one selected from polyether ketone, polyether ether ketone, polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide, polyparaphenylene, polyphenylene oxide, and polyimide. 5. The proton conductive electrolyte membrane according to any one of 1 to 4.
6). 6. The proton conductive electrolyte membrane according to any one of 1 to 5, wherein the proton conductive polymer has a crosslinked structure.
7). R ^{2 of the} compound represented by the general formula (1) is an organic group having at least one of an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an aminoalkyl group, and a vinyl group. The proton conductive electrolyte membrane according to any one of 1 to 6.
8). 8. The proton conductive electrolyte membrane according to any one of 1 to 7, wherein the inorganic porous membrane has an average pore diameter of 10 to 450 nm.
9. 9. The proton conductive electrolyte membrane according to any one of 1 to 8, wherein the porosity of the inorganic porous membrane is 40 to 95%.
10. 2. The proton conductive electrolyte membrane according to 1, wherein the reaction product is a reaction product produced by a reaction in the pores.
11. 3. The proton conductive electrolyte membrane according to 2, wherein the reaction product is a reaction product generated by a reaction in the pores.
12 The proton conductive electrolyte membrane according to any one of 3 to 11, wherein the inorganic particles are used in a proportion of 5 to 60% by volume and the organic particles are used in a proportion of 40 to 95% by volume.
13. 13. The method according to any one of 3 to 12, wherein the step of holding the inorganic particles and the organic particles on a support using the dispersion liquid containing the inorganic particles and the organic particles is a coating step. Proton conductive electrolyte membrane.
14 14. A polymer electrolyte fuel cell comprising a cathode electrode, an anode electrode and an electrolyte sandwiched between the two electrodes, wherein the proton conductive electrolyte membrane according to any one of 1 to 13 is used as the electrolyte. Solid polymer fuel cell.
15. A production method for producing a proton-conducting electrolyte membrane according to 15.10, wherein a polymer compound haloalkylated and sulfonated in the pores of an inorganic porous membrane having pores and A method for producing a proton-conducting electrolyte membrane, wherein the compound represented by formula (1) is charged and reacted.
16. A production method for producing a proton-conducting electrolyte membrane according to 16.11, comprising a polymer compound haloalkylated and sulfonated in the pores of an inorganic porous membrane having pores and A method for producing a proton-conducting electrolyte membrane, comprising filling a compound represented by the formula (1) and a reactive emulsifier and allowing them to react.

  According to the present invention, it is possible to provide a proton conductive electrolyte membrane having sufficiently high proton conductivity and sufficiently low methanol permeability, a method for producing the same, and a polymer electrolyte fuel cell using the proton conductive electrolyte membrane. It was.

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

  Hereinafter, the present invention will be described in detail.

The proton conductive electrolyte membrane of the present invention is a proton conductive electrolyte membrane in which an inorganic porous membrane having pores is filled with a proton conductive polymer, and the proton conductive polymer is a haloalkylated and sulfone polymer. It is a reaction product of the polymerized polymer and the compound represented by the general formula (1).
The inorganic porous membrane having pores according to the present invention includes a step of holding the inorganic particles and the organic particles on a support using a dispersion containing inorganic particles and organic particles, and after this step, It is preferable to use an inorganic porous membrane obtained by obtaining a step of firing inorganic particles, organic particles, and a support.
The proton conductive electrolyte membrane of the present invention can be obtained by filling the inorganic porous membrane having the pores with a proton conductive polymer.
As the support, a support made of any material can be used as long as it eventually burns out or melts away, or can be peeled off. For example, paper such as filter paper, cloth such as nonwoven fabric, polyethylene terephthalate, etc. A support formed of an arbitrary material such as a polymer film can be used. The surface of the support is preferably smooth, and if it is smooth, the surface of the proton conductive electrolyte membrane obtained is also smooth. When used as an electrolyte for a polymer electrolyte fuel cell, the electrode, the proton conductive electrolyte membrane, The contact at the interface becomes dense. The surface roughness of the support is not particularly limited, but the surface roughness Rz of the surface on which the dispersion liquid containing inorganic particles and organic particles is laminated is preferably 3 μm or less. The surface roughness Rz refers to the JIS ten-point average surface roughness Rz. For the measurement, for example, a stylus type three-dimensional roughness meter (Surfcom 570A) manufactured by Tokyo Seimitsu Co., Ltd. can be used. 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 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, and Zr. The hydroxide is mentioned. These may be used alone or in combination of several kinds. In the present invention, silica (SiO ₂ ) is 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.

  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. In addition, the primary average particle diameter here refers to an average value of the long diameters of 200 particles measured randomly by observation with a scanning electron microscope.

  As the organic particles, organic particles of any material can be used as long as they are eventually burned out or dissolved, but those that do not swell in the 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 step of firing after laminating a dispersion liquid containing inorganic particles and organic particles, so that the inorganic particles are fixed and sintered to form a thin film. At the same time, the portion mainly occupied by the organic particles forms pores in the thin film. In the present invention, the average pore diameter of the pores 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. The proton conductive electrolyte membrane obtained by filling the thus formed inorganic porous membrane with a proton conductive polymer was found to have high proton conductivity and low methanol permeability.

  In the present invention, the porosity of the porous membrane is preferably 40 to 95%, more preferably 50 to 70%.

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
By using inorganic particles at 5 to 60% by volume and organic particles at 40 to 95% by volume, the porosity of the porous film can be adjusted to the above range. The volume% expresses the ratio of the volume of each particle to the sum of the volume of the inorganic particles and the volume of the organic particles as a percentage.

  Next, a method for preparing a dispersion containing inorganic particles and organic particles according to the present invention 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, and a paint shaker. These may be used alone or in appropriate combination. be able to.

  As a step of laminating a 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.

The inorganic porous film can be formed by holding a dispersion containing inorganic particles and organic particles in a layered form and firing the dried one. In order to sinter dried and dried layers, if the support is burnt out or melts away, hold the dispersion on the support in layers and dry to support inorganic and organic particles What is necessary is just to heat-process with an electric furnace in nitrogen atmosphere, and to sinter it, hold | maintain on a body.
As a state where the inorganic particles and the organic particles are held on the support, it is preferable that the inorganic particles and the organic particles are uniformly dispersed.
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 10-300 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 proton conductive polymer filled in the pores of the inorganic porous membrane according to the present invention is a polymer obtained by reacting a haloalkylated and sulfonated polymer compound with a compound represented by the general formula (1), Alternatively, it is a polymer obtained by reacting a haloalkylated and sulfonated polymer compound, a compound represented by the general formula (1), and a reactive emulsifier.

The haloalkylated and sulfonated polymer compound is preferably a haloalkylated and sulfonated polymer having an aromatic ring in the molecule. In addition, it is preferable to use a haloalkylated and sulfonated polymer compound known as an engineering plastic for improving durability. Engineering plastic has no general definition, and refers to a high-elasticity, high-strength plastic that can be used as a structural material, such as 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 an elastic modulus 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 / SO2), polyparaphenylene (PPP), polyphenylquinoxaline (PPQ), polyarylketone (PK), polyetherketone (PEK), polyethersulfone (PES), polyetherethersulfur (PEES), polyarylsulfone, polyarylethersulfone (PAS), polyphenylsulfone (PPSU), polyphenylenesulfone (PPSO2), polyetherimide, fluorinated polyimide, polyetheretherketone (PEEK), polyetherketone 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, and polyimide.

  The polymer compound is used without any limitation as long as it has a molecular weight of 10,000 to 100,000 and is conventionally known.

  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 a state where sulfuric acid as a solvent is present in a large excess as a solvent, and since the reaction rate is extremely fast, the haloalkylating reagent is sufficiently stirred while sufficiently stirring the sulfuric acid solution of the polymer compound sufficiently. It is necessary to add. The amount of haloalkyl group introduced into the polymer compound can also be controlled by the ratio between the number of moles of haloalkylating reagent to be added and the number of moles of units into which the haloalkyl group of the polymer compound is introduced. The reaction proceeds very quickly, but the reaction time is 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) described later, and can form a crosslinked structure with the same kind of haloalkylated and sulfonated polymer compounds. In addition, two or more haloalkylated and sulfonated polymer compounds can form a crosslinked structure. Such a polymer can improve the performance of the proton conducting polymer.

R ¹ of the compound represented by the general formula (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 arbitrary organic group, but is preferably a copolymerizable group, and further capable of reacting with a haloalkylated and sulfonated polymer compound or a reactive emulsifier. An organic group is preferable, and an organic group containing at least one of an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an aminoalkyl group, and a vinyl group is particularly preferable.

  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. .

  In the compound represented by the general formula (1), a silyl group can react to form a crosslinked structure. Furthermore, it is also one of preferable embodiments that the silyl group of the compound represented by the general formula (1) reacts with and binds to the inorganic porous surface silanol group.

  The reactive emulsifier is a surfactant having a group capable of reacting with a haloalkylated and sulfonated polymer compound or the compound represented by the general formula (1). An anionic and / or nonionic emulsifier having at least one unsaturated double bond is preferably used. The reactive emulsifier is preferably a compound having at least one hydrophobic group, hydrophilic group and reactive group in the molecule, and the hydrophobic group is composed of an aliphatic or aromatic hydrocarbon group, and the hydrophilic group is Contains a nonionic group typified by a polyoxyalkylene ether group, an anionic group typified by a sulfonate, a carboxylate, and a phosphate, and the reactive group includes a vinyl ether group, an allyl ether group, a vinyl phenyl group, 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.

  Specific examples of the reactive emulsifier include, for example, 1- (meth) allyloxy-2-hydroxypropane, (meth) acryloyloxy-2-hydroxypropane, (meth) allyloxycarbonylmethyl-3-alkoxy (poly Oxyalkylenoxy) -2-hydroxypropane, alkylphenoxy (polyoxyalkylenoxy) -2-hydroxypropane, or acyloxy (polyoxyalkylenoxy) -2-hydroxypropane or an alkylene oxide adduct thereof, or a sulfuric acid thereof. An alkylene oxide adduct of a phosphoric acid ester or salt thereof, a bisphenol compound or a glycol compound, or a sulfuric acid or phosphoric acid ester or salt thereof, an alkylene oxide adduct of a vinyl or allyl phenol compound or Et sulfuric 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” (trade name, Asahi Denka Co., Ltd.), “Aqualon KH”, “Aquaron HS”, “Aquaron BC”, “Aquaron RN”, “New Frontier” (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), “Eleminol ES” , “Eleminol JS”, “Eleminol RS”, “Eleminol MON”, “Eleminol HA” (trade name, manufactured by Sanyo Chemical Industries), “Latemuru” (trade name, manufactured by Kao Corp.), etc. However, it is not limited to these. These reactive emulsifiers may be used alone or in combination of two or more.

  The method of filling the proton conductive polymer into the pores of the inorganic porous membrane 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 filled into the pores of the porous membrane by a method of immersing in a conductive polymer solution. At that time, it is possible to easily fill the pores with the proton conductive polymer by using ultrasonic waves or reducing the pressure.

  Preferably, it contains a precursor of a proton conductive polymer (the haloalkylated and sulfonated polymer compound, the compound represented by the general formula (1), the reactive emulsifier, etc.), a catalyst, a polymerization initiator, and the like. In this method, the solution is filled in the pores of the porous membrane and subjected to an in-situ reaction by an appropriate method known in the art such as thermal reaction or photoreaction to form a proton conductive polymer. At that time, it is possible to easily fill the pores with a solution containing the precursor of the proton conductive polymer or the like by using ultrasonic waves or reducing the pressure. A method is also preferred in which after the surface of the pores of the inorganic porous membrane is hydrophilized, a solution containing the proton conductive polymer precursor or the like is filled in the pores of the porous membrane and subjected to in-situ reaction. It is also preferable to adjust the viscosity of the solution containing the proton conductive polymer precursor, the catalyst, and the like as appropriate so that the pores can be easily filled.

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. For example, as a thermal polymerization initiator, azobisnitrile compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobispropionitrile, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, T-Butyl perbenzoate, α-cumyl hydroperoxide, di-t-butyl peroxide, diisopropyl peroxydicarbonate, t-butyl peroxyisopropyl carbonate, peracids, alkyl peroxycarbamates, nitrosoaryl acylamines Such as organic peroxides, inorganic peroxides such as potassium persulfate, ammonium persulfate, potassium perchlorate, diazoaminobenzene, p-nitrobenzenediazonium, azobis-substituted alkanes, diazothioethers, arylazosulfones, etc. Azo or diazo compounds, Torosofeniru urea, tetramethyl thiuram disulfide, diaryl disulfides, dibenzoyl disulfide, tetraalkyl thiuram disulfides, dialkyl xanthate disulfides, aryl sulfinic acids, arylalkyl sulfonic acids, may be mentioned 1-alkanoic sulfinic acids and the like.

  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 atom 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), acyloin ethers (eg, benzoin methyl ether), Ar—CR (OH) —CO—Ar (Ar = aryl group, R = hydrocarbon group) And substituted acyloins represented by the formula (for example, α-alkylbenzoin and the like) and polynuclear quinones (for example, 9,10-anthraquinone and the like).

  The amount of the photopolymerization initiator used is preferably in the range of 0.5 to 5% by mass, more preferably in the range of 1 to 3% by mass with respect to the total mass of the unsaturated compounds. The catalyst and the polymerization initiator can be used alone or in combination.

  The mass ratio between the haloalkylated and sulfonated polymer compound and the compound represented by the general formula (1) is preferably in the range of 100: 0.1 to 1: 1. The mass ratio between the polymer compound and the reactive emulsifier is preferably in the range of 100: 0.1 to 1: 1.

  The ion exchange capacity of the proton conductive polymer is 0.5 to 5.0 meq / g dry resin, preferably 1.0 to 4.5 meq / g dry resin. When the ion exchange capacity is smaller than 0.5 meq / g dry resin, the ion conduction resistance is increased, and when the ion exchange capacity is greater than 4.5 meq / g dry resin, it 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, to calculate the amount of protons from the dry weight of the proton conductive polymer (W) and volume of sodium hydroxide required for neutralization titration (V) (H ^+), ion-exchange capacity by the following equation (meq / g ) 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 solid polymer fuel cell is particularly preferable.

  Next, a direct methanol solid polymer fuel cell will be described with reference to FIG. FIG. 1 is a schematic view showing an embodiment of a direct methanol type solid polymer 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.

In the anode 2, methanol electrons to generate by reacting with water the carbon dioxide and hydrogen ions (H ^{+) -} releasing (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 is formed by stacking a plurality of single cells via a cooling plate or the like, with a single cell provided with a flow distribution plate (separator).

  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 70% by volume, colloidal silica 30% by volume) is diluted with 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 fired at 1000 ° C. for 3 hours. 1 was produced.

<Porous membrane no. Preparation of 2 to 4>
Porous membrane no. 1 except that the polystyrene fine particles and colloidal silica were replaced as shown in Table 1. As in the case of porous membrane No. 1 2 to 4 were produced.

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

Porous membrane no. The pore diameters and porosity of 1-4 are shown in Table 1. The porosity was calculated by the following formula 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, for example, 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 was filled with a proton conductive polymer by the following method to produce a proton conductive electrolyte membrane (electrolyte membrane No. 1).

  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 between polyethylene terephthalate films, heated, and dried 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.

[Proton conducting electrolyte membrane No. Production of 2-12]
Proton conductive electrolyte membrane No. 1 except that the chloromethylated and sulfonated polymer compound, the compound represented by the general formula (1) and the reactive emulsifier were changed as shown in Table 2. In the same manner as in No. 1, proton conductive electrolyte membrane No. 1 2 to 12 were produced.

[Evaluation of proton conducting electrolyte membrane]
For comparison, Nafion 117 (manufactured by DuPont) was also prepared.

(Proton conductivity)
The proton-conducting electrolyte membrane was swollen in water (25 ° C.), and then sandwiched between two platinum electrodes. Impedance was measured using an LCR meter HP4284A manufactured by Hewlett-Packard Co., and proton conductivity was calculated.

(Methanol permeability)
A proton-conducting electrolyte membrane is sandwiched between the H-type cell of FIG. 2, and the amount of methanol permeating from the 2 mol / L aqueous methanol solution in the A cell into the pure water of the B cell is measured by gas chromatography (GC -14B). The results are shown in Table 3.

  From the results of Table 3, it can be seen that the proton conductive electrolyte membranes (electrolyte membranes No. 1 to 10) of the present invention have high proton conductivity and low methanol permeability. It can be seen that the comparative proton conductive electrolyte membranes (electrolyte membranes No. 11 and 12) have high proton conductivity as well as Nafion 117, but have the disadvantage of high methanol permeability.

[Fabrication and evaluation of fuel cells]
A membrane-electrode assembly (MEA) was produced and evaluated by the following method using the produced proton conductive electrolyte membrane (electrolyte membrane Nos. 1 to 12) and Nafion 117 as a comparative sample.

<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 base material, 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 membranes (electrolyte membranes No. 1 to 12) and Nafion 117 were each held between an anode electrode and a cathode electrode, and heated and pressed to thereby form a membrane-electrode assembly (MEA) (MEA-No. 1-12) and MEA-Nafion 117 were prepared. This membrane-electrode assembly (MEA) was sandwiched between separators, and a fuel cell was operated by flowing a 3% aqueous methanol solution on the anode side and air on the cathode side, and the current-voltage characteristics were evaluated. Table 4 shows the current density at a voltage of 0.4V.

  From the results of Table 4, the membrane-electrode assembly (MEA) (MEA-No. 1 to 10) according to the present invention is a comparative membrane-electrode assembly (MEA) (MEA-No. 11, 12) and MEA. -It can be seen that the current density is higher than that of Nafion 117.

Claims (16)

A proton conductive electrolyte membrane having a pore-containing inorganic porous membrane filled with a proton conductive polymer, wherein the proton conductive polymer is a haloalkylated and sulfonated polymer compound and the following general formula: A proton conductive electrolyte membrane which is a reaction product with the compound represented by (1).
(Wherein R ¹ represents an alkyl group having 4 or less carbon atoms, R ² represents an arbitrary organic group, and m and n are each an integer of 1 to 3, provided that m + n = 4, m When R is 2 or 3, R ² may be a different organic group.) The proton conductive polymer is a reaction product of the haloalkylated and sulfonated polymer compound, the compound represented by the general formula (1) according to claim 1, and a reactive emulsifier. The proton conductive electrolyte membrane according to claim 1, wherein: A step of holding the inorganic particles and the organic particles on a support using a dispersion liquid containing inorganic particles and organic particles, and the inorganic particles, the organic particles and the support after the steps; The proton conductive electrolyte membrane according to claim 1 or 2, which is an inorganic porous membrane obtained through a step of firing the body. 4. The proton conductive electrolyte membrane according to claim 3, wherein the inorganic particles have a primary average particle size of 10 to 100 nm. The polymer compound is at least one selected from polyether ketone, polyether ether ketone, polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide, polyparaphenylene, polyphenylene oxide, and polyimide. The proton conductive electrolyte membrane according to any one of claims 1 to 4. The proton conductive electrolyte membrane according to any one of claims 1 to 5, wherein the proton conductive polymer has a crosslinked structure. R ^{2 of the} compound represented by the general formula (1) is an organic group having at least one of an epoxy group, a styryl group, a methacryloxy group, an acryloxy group, an aminoalkyl group, and a vinyl group. The proton conductive electrolyte membrane according to any one of claims 1 to 6. The proton conductive electrolyte membrane according to any one of claims 1 to 7, wherein the inorganic porous membrane has an average pore diameter of 10 to 450 nm. The proton conductive electrolyte membrane according to any one of claims 1 to 8, wherein the porosity of the inorganic porous membrane is 40 to 95%. The proton conductive electrolyte membrane according to claim 1, wherein the reaction product is a reaction product generated by a reaction in the pores. 3. The proton conductive electrolyte membrane according to claim 2, wherein the reaction product is a reaction product generated by a reaction in the pores. The proton conductive electrolyte membrane according to any one of claims 3 to 11, wherein the inorganic particles are used in a proportion of 5 to 60% by volume and the organic particles are used in a proportion of 40 to 95% by volume. The step of holding the inorganic particles and the organic particles on a support using the dispersion liquid containing the inorganic particles and the organic particles is a coating step, and any one of claims 3 to 12 2. The proton conductive electrolyte membrane according to item 1. 14. A polymer electrolyte fuel cell comprising a cathode electrode, an anode electrode, and an electrolyte sandwiched between the two electrodes, wherein the proton conductive electrolyte membrane according to any one of claims 1 to 13 is used as the electrolyte. A polymer electrolyte fuel cell using A method for producing the proton-conducting electrolyte membrane according to claim 10, comprising: a polymer compound haloalkylated and sulfonated in the pores of the inorganic porous membrane having pores; A method for producing a proton-conducting electrolyte membrane, comprising filling and reacting the compound represented by the general formula (1) described in the first item of the range. A method for producing a proton conducting electrolyte membrane according to claim 11, comprising a polymer compound haloalkylated and sulfonated in the pores of an inorganic porous membrane having pores. A method for producing a proton-conducting electrolyte membrane, comprising filling and reacting a compound represented by the general formula (1) according to the first aspect of the range and a reactive emulsifier.