Electrolyte membrane electrode gas diffusion layer assembly for fuel cell and method for manufacturing the same

Abstract

The present invention provides a method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly in which a water-repellent layer in the gas diffusion layer and a catalyst layer in the electrolyte membrane electrode assembly are bonded with high bonding strength. [Solution] A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell, comprising: a film formation step of forming a mixed powder layer on the surface of a porous substrate 4 by a dry film formation method using a mixed powder containing a specific carbon particle powder (A) and a specific fluoropolymer resin particle powder (B) or a specific thermosetting resin raw material particle powder (C); a compaction step of pressurizing and compacting the mixed powder layer; a water-repellent layer formation step of firing the compacted mixed powder layer to obtain a gas diffusion layer 6 in which a water-repellent layer 5 is laminated on the surface of the porous substrate 4; and a joining step of joining the water-repellent layer 5 in the gas diffusion layer 6 and the catalyst layer 2a in the electrolyte membrane electrode assembly 3 via a fluoropolymer surfactant 7 to obtain an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte membrane electrode gas diffusion layer assembly for fuel cells and a method for manufacturing the same. [Background technology]

[0002] Fuel cells typically have a membrane electrode assembly (MEA) as their basic unit, in which electrodes containing catalyst layers are bonded to both sides of an electrolyte membrane. In this assembly, the electrodes generally have a two-layer structure consisting of a gas diffusion layer and a catalyst layer. Since such a gas diffusion layer is used to supply reaction gases and electrons to the catalyst layer, which is the reaction field for the electrode reaction, it has traditionally been required to have gas permeability and properties that allow for water management (e.g., water repellency). For this reason, gas diffusion layers generally utilize a porous substrate such as carbon paper or carbon cloth, and a water-repellent layer laminated on the surface of such a porous substrate.

[0003] As a method for manufacturing a water-repellent layer for such fuel cells, for example, Japanese Patent Application Publication No. 2021-2444 (Patent Document 1) discloses a method comprising the steps of: preparing a granule comprising first particles made of spheroidized graphite, second particles containing fine carbon having a smaller particle size than the first particles, and a water-repellent polymer such as polytetrafluoroethylene, wherein the second particles are bonded to the surface of the first particles via the water-repellent polymer; coating the granule onto a substrate surface using a powder coating apparatus; and heat-treating the obtained coating film. Typically, by such a method, a water-repellent layer is laminated on the surface of a porous substrate to form a gas diffusion layer, and further, the water-repellent layer in the gas diffusion layer is bonded to the catalyst layer of the electrolyte membrane electrode assembly to form an electrolyte membrane electrode gas diffusion layer assembly. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-2444 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in conventional electrolyte membrane electrode gas diffusion layer assemblies, the bonding strength between the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assemblies was not always sufficiently high.

[0006] The present invention has been made in view of the problems of the above-mentioned prior art, and aims to provide an electrolyte membrane electrode gas diffusion layer assembly in which a water-repellent layer in a gas diffusion layer and a catalyst layer in an electrolyte membrane electrode assembly are bonded with high bonding strength, and a method for manufacturing the same. [Means for solving the problem]

[0007] As a result of diligent research to achieve the above objective, the inventors have discovered that by bonding the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly using a fluorine-based surfactant, the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly can be bonded with high bonding strength, thus completing the present invention.

[0008] In other words, the present invention provides the following embodiments. [1] A film formation step in which a mixed powder containing a powder of carbon particles (A) with an average particle diameter of 0.002 to 50 μm and a powder of fluoropolymer-based thermoplastic resin particles (B) with an average particle diameter of 0.01 to 50 μm or a powder of thermosetting resin raw material particles (C) with an average particle diameter of 0.01 to 50 μm is formed on the surface of a porous substrate by a dry film formation method to form a mixed powder layer, A compaction step is performed by pressurizing the mixed powder layer under conditions of 0.2 to 5 MPa, A water-repellent layer formation step is obtained in which a water-repellent layer for a fuel cell is laminated on the surface of the porous substrate by firing the compacted mixed powder layer to obtain a gas diffusion layer in which a water-repellent layer for a fuel cell is laminated on the surface of the porous substrate, the water-repellent layer being made of a mixed bond of the carbon particle powder (A) and the fluoropolymer resin powder (B), or a mixed bond of the carbon particle powder (A) and a water-resistant resin (C) made of a thermosetting resin which is a polycondensate of the raw materials. A bonding step to obtain an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell comprising the gas diffusion layer and the electrolyte membrane electrode assembly, by bonding the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly via a fluorine-based surfactant. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for fuel cells, including the above. [2] If the mixed powder is a mixed powder of powder (A) and powder (B), the content of powder (B) is 17 to 40% by mass of the total amount of powder (A) and powder (B). The method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to [1], wherein, when the mixed powder is a mixed powder of powder (A) and powder (C), the content of powder (C) is 15 to 60% by mass relative to the total amount of powder (A) and powder (C). [3] The firing temperature in the water-repellent layer formation step is If the mixed powder is a mixed powder of powder (A) and powder (B), then the temperature is within the range of -60°C to +85°C relative to the melting point of the fluoropolymer resin. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to [1] or [2], wherein the mixed powder is a mixed powder of powder (A) and powder (C), the temperature is 10 to 130°C lower than the decomposition temperature of the thermosetting resin. [4] A method for producing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to any one of [1] to [3], without using a dispersant. [5] The fluoropolymer is at least one resin selected from the group consisting of polytetrafluoroethylene, perfluoroethylenepropene copolymer and polyvinylidene fluorite. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to any one of [1] to [4], wherein the water-resistant resin (C) is at least one resin selected from the group consisting of phenolic resin, silicone resin, polyurethane resin, urea resin, melamine resin, and acrylic resin. [6] In the film formation process, If the mixed powder is a mixed powder of powder (A) and powder (B), the mixed powder is formed as a film on the surface of the porous substrate having at least the same resin as the resin constituting the fluoropolymer resin particles on its surface. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to any one of [1] to [5], wherein the mixed powder is a mixed powder of powder (A) and powder (C), the mixed powder is formed on the surface of the porous substrate having at least one of the same raw materials as the resin constituting the thermosetting resin and / or the same resin as the resin constituting the thermosetting resin on at least one of its surfaces. [7] A gas diffusion layer comprising a porous substrate and a gas diffusion layer comprising a gas diffusion layer comprising a gas diffusion layer comprising a gas comprising a porous substrate and a gas comprising a gas comprising a gas comprising a mixed powder comprising a gas comprising a mixed bond of the carbon particle powder (A) having an average particle diameter of 0.002 to 50 μm and a gas comprising a gas comprising a mixed bond of the carbon particle powder (A) and the gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a mixed bond of the gas comprising the carbon particle powder (A) and the gas comprising the gas comprising the gas comprising the gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a porous substrate and a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a gas comprising a porous substrate and It comprises an electrolyte membrane electrode assembly, A fuel cell electrolyte membrane electrode gas diffusion layer assembly, wherein the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly are joined via a fluorine-based surfactant. [8] If the mixed powder is a mixed powder of powder (A) and powder (B), the content of powder (B) is 17 to 40% by mass of the total amount of powder (A) and powder (B), The electrolyte membrane electrode gas diffusion layer assembly for fuel cell according to [7], wherein the mixed powder is a mixed powder of powder (A) and powder (C), and the content of powder (C) is 15 to 60% by mass of the total amount of powder (A) and powder (C). [9] The fluorine-based thermoplastic resin is at least one resin selected from the group consisting of polytetrafluoroethylene, perfluoroethylene propene copolymer, and polyvinylidene fluoride, The fuel cell electrolyte membrane electrode gas diffusion layer laminate according to [7] or [8], wherein the thermosetting resin is at least one resin selected from the group consisting of phenolic resin, silicone resin, polyurethane resin, urea resin, melamine resin, and acrylic resin.

[10] When the mixed powder is a mixed powder of the powder (A) and the powder (B), the water-repellent layer is laminated on the surface of the porous substrate having at least the same resin as the resin constituting the fluorine-based thermoplastic resin particles on the surface, The fuel cell electrolyte membrane electrode gas diffusion layer laminate according to any one of [7] to [9], wherein when the mixed powder is a mixed powder of the powder (A) and the powder (C), the water-repellent layer is laminated on the surface of the porous substrate having at least one raw material of at least one resin constituting the thermosetting resin and / or at least one resin constituting the thermosetting resin on the surface.

Advantages of the Invention

[0009] According to the present invention, it is possible to obtain an electrolyte membrane electrode gas diffusion layer laminate in which the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly are joined with high joining strength.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram showing a cross section of an embodiment of the electrolyte membrane electrode gas diffusion layer laminate of the present invention. [Figure 2] It is a photograph showing the dispersion state when hydrophilic carbon particles and hydrophobic carbon particles used in Examples and Comparative Examples were added to water (methanol concentration: 0% by mass), respectively. [Figure 3] It is a graph showing the joining strength of the electrolyte membrane electrode gas diffusion layer laminates produced in Examples 1 to 4 and Comparative Examples 1 to 8. [Figure 4]It is an electron micrograph showing the SEM-EDS image (element mapping image) of the water-repellent layer surface obtained in Example 2. [Figure 5] It is an electron micrograph showing the SEM-EDS image (element mapping image) of the water-repellent layer surface obtained in Comparative Example 3.

Mode for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail according to its preferred embodiments.

[0012] 〔Method for Manufacturing an Electrolyte Membrane Electrode Gas Diffusion Layer Assembly for Fuel Cells〕 The method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to the present invention is A film-forming step of forming a mixed powder layer by forming a mixed powder containing powder (A) of carbon particles having an average particle diameter of 0.002 to 50 μm and powder (B) of fluorine-based thermoplastic resin particles having an average particle diameter of 0.01 to 50 μm or powder (C) of thermosetting resin raw material particles having an average particle diameter of 0.01 to 50 μm on the surface of a porous substrate by a dry film-forming method; A consolidation step of pressurizing and consolidating the mixed powder layer under the condition of 0.2 to 50 MPa; By firing the consolidated mixed powder layer, a water-repellent layer for a fuel cell composed of a mixed joint body of the powder (A) of the carbon particles and the powder (B) of the fluorine-based thermoplastic resin particles or a mixed joint body of the powder (A) of the carbon particles and a water-resistant resin (C) composed of a thermosetting resin which is a polycondensate of the raw material is laminated on the surface of the porous substrate to obtain a gas diffusion layer; a water-repellent layer forming step; A joining step of joining the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly via a fluorine-based surfactant to obtain an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell including the gas diffusion layer and the electrolyte membrane electrode assembly. It is a method including the above steps. Hereinafter, it will be described separately for each step.

[0013] (Film-forming step) The film-forming step according to the present invention is a step of forming a mixed powder containing powder (A) and powder (B) or powder (C) on the surface of a porous substrate by a dry film-forming method, thereby forming a mixed powder layer.

[0014] The aforementioned powder (A) is a powder composed of carbon particles with an average particle size of 0.002 to 50 μm. Such carbon particles may be hydrophilic or hydrophobic. Examples of hydrophilic carbon particles include those having hydrophilic groups such as hydroxyl groups or carboxyl groups on the surface of the carbon particles, which can be obtained by subjecting the carbon particles to known hydrophilic treatments (open corona discharge treatment, steam oxidation treatment, acid treatment, etc.). Examples of hydrophobic carbon particles include carbon black such as furnace black obtained by blowing petroleum-based or coal-based oil as a raw material into a high-temperature gas and causing incomplete combustion, or acetylene black obtained by the thermal decomposition of acetylene gas, in which the particle surface has not been subjected to a hydrophilic treatment, i.e., carbon particles as they are obtained by incomplete combustion or thermal decomposition.

[0015] Furthermore, the properties of carbon particles, such as "hydrophilicity" and "hydrophobicity," can be evaluated using the so-called Methanol Wettability method (see Mitsuru Ochiai, Aerosol Research, published in 1990, vol. 5, pp. 32-43). Specifically, water (methanol concentration: 0 mass%) and methanol aqueous solutions of different methanol concentrations are prepared. Carbon particles are gently added to the water and methanol aqueous solutions of each concentration and shaken lightly several dozen times. The methanol concentration at which the carbon particles disperse in the water or methanol aqueous solution (the methanol concentration in the aqueous solution with the lowest methanol concentration where the carbon particles are dispersed: this is 0 in the case of water) is determined. If this methanol concentration is less than 2 mass%, the carbon particles are evaluated as "hydrophilic." On the other hand, if the methanol concentration is 2 mass% or more (when carbon particles are added to a methanol aqueous solution with a methanol concentration of 2 mass% or more and the carbon particles disperse in the methanol aqueous solution), the carbon particles are evaluated as "hydrophobic."

[0016] The average particle diameter of the carbon particles must be between 0.002 and 50 μm, preferably between 0.002 and 30 μm, more preferably between 0.002 and 10 μm, and even more preferably between 0.002 and 1 μm. When the average particle diameter of the hydrophilic carbon particles is above the lower limit, the gas diffusion is improved compared to when it is below the lower limit, thus improving power generation performance. On the other hand, when the average particle diameter of the hydrophilic carbon particles is below the upper limit, the electronic resistance is reduced compared to when it exceeds the upper limit, thus improving power generation performance. The average particle diameter of the carbon particles can be determined by measuring it using a particle size distribution analyzer or by measuring the particle diameter of 500 randomly selected particles using an electron microscope and averaging the results. In addition, in this invention, commercially available carbon particles with an average particle diameter within the above range can be used.

[0017] The powder (B) is composed of fluoropolymer resin particles with an average particle size of 0.01 to 50 μm. Examples of such fluoropolymer resin particles include polytetrafluoroethylene (PTFE, melting point: 327°C), perfluoroethylene propene copolymer (FEP, melting point: 260°C), and polyvinylidene fluoride (PVDF, melting point: 151 to 178°C). These fluoropolymer resin particles may be used individually or in combination of two or more. Among these fluoropolymer resin particles, PTFE particles and FEP particles are preferred from the viewpoint that the strength of the water-repellent layer itself is improved through some interaction with the surface functional groups of carbon black.

[0018] The average particle diameter of the fluoropolymer-based thermoplastic resin particles must be between 0.01 and 50 μm, preferably between 0.01 and 40 μm, and more preferably between 0.01 and 30 μm. When the average particle diameter of the fluoropolymer-based thermoplastic resin particles is below the upper limit, the dispersibility of the resin particles in the mixed powder is higher compared to when it exceeds the upper limit, and the carbon particles and the fluoropolymer-based thermoplastic resin particles are more uniformly dispersed in the final water-repellent layer, thereby improving the power generation performance of the fuel cell. The average particle diameter of the fluoropolymer-based thermoplastic resin particles can be determined by measuring it using a particle size distribution analyzer or by measuring the particle diameter of 500 randomly selected particles using an electron microscope and averaging the results. In addition, in this invention, commercially available fluoropolymer-based thermoplastic resin particles with an average particle diameter within the above range can be used.

[0019] The aforementioned powder (C) is a powder composed of thermosetting resin raw material particles with an average particle size of 0.01 to 50 μm. By using such thermosetting resin raw material particles, the firing temperature during heat treatment can be reduced, thereby enabling the formation of a water-repellent layer with energy efficiency and reducing manufacturing costs.

[0020] The thermosetting resin raw material particles can be any thermosetting resin obtained by polycondensation (curing by heat treatment) of the thermosetting resin raw material that exhibits water resistance. For example, particles of raw material monomers and their low condensates for water-resistant thermosetting resins (water-resistant resins) can be used. More specifically, from the viewpoint of having a relatively low polymerization temperature and high affinity with carbon particles, particles of raw material monomers and their low condensates for thermosetting resins such as phenol resins, silicone resins, polyurethane resins, urea resins, melamine resins, and acrylic resins are preferred. Furthermore, from the viewpoint of cost advantages, particles of raw material monomers and their low condensates for melamine resins are even more preferred. The phenolic resin, silicone resin, polyurethane resin, urea resin, melamine resin, and acrylic resin are thermosetting resins that exhibit water resistance. These thermosetting resin raw material particles may be used individually or in combination of two or more types. Furthermore, in the present invention, commercially available products can be used as the thermosetting resin raw material particles.

[0021] As the raw material monomers and low-condensate particles of the melamine resin, particles of methylolmelamine and its low-condensate (low-condensate of methylolmelamine and formaldehyde) and methylated melamine particles are preferred, and particles of methylolmelamine and its low-condensate are more preferred, from the viewpoint of having a relatively low polymerization temperature, high affinity with carbon particles, cost advantages, and good workability. As the low-condensate of methylolmelamine, a low-condensate of methylolmelamine having an amino group, an imino group, a methylol group, and an alkyl ether group is preferred. Furthermore, as the methylated melamine particles, methylated melamine particles having an amino group, an imino group, a methylol group, and an alkyl ether group are preferred. Particles of raw material monomers and their low condensates for melamine resins having amino groups, imino groups, methylol groups, and alkyl ether groups can be reacted with raw material monomers and their low condensates for other thermosetting resins having functional groups (e.g., amino groups, amide groups, carboxyl groups, hydroxyl groups, etc.) that can react with amino groups, imino groups, methylol groups, and alkyl ether groups to form a water-resistant thermosetting resin (water-resistant resin). In addition, in the present invention, commercially available products can be used as such methylolmelamine and its low condensate particles or methylated melamine particles.

[0022] Furthermore, it is preferable to use the melamine resin raw material monomer and its low-condensate particles in combination with the acrylic resin raw material monomer and its low-condensate. This improves durability such as weather resistance, corrosion resistance, stain resistance, and chemical resistance.

[0023] If the raw material monomers for the thermosetting resin and their low condensates are commercially available in liquid or aqueous solution form, they can be dried and then pulverized or otherwise processed into powder for use as thermosetting resin raw material particles. Furthermore, when using the raw material monomers for the thermosetting resin and their low condensates in liquid or aqueous solution form, for example, the raw material monomers or their low condensates may be attached to the surface of the carbon particles and dried, thereby coating at least a portion of the surface of the carbon particles with the raw material monomers or their low condensates, and these can be used as thermosetting resin raw material coated carbon particles. In such thermosetting resin raw material coated carbon particles, the raw material monomers or their low condensates may cover the entire surface of the carbon particles or only a portion of it. When using the thermosetting resin raw material coated carbon particles, the core portion (carbon particles) of the thermosetting resin raw material coated carbon particles can be considered as the carbon particles constituting powder (A), and the thermosetting resin raw material coated carbon particles can be considered as the thermosetting resin raw material particles constituting powder (C). Therefore, the carbon particles coated with the thermosetting resin raw material can be considered to be a mixed powder containing powder (A) and powder (C).

[0024] The average particle size of the thermosetting resin raw material particles must be 0.01 to 50 μm, preferably 0.01 to 40 μm, and more preferably 0.01 to 30 μm. When the average particle size of the thermosetting resin raw material particles is below the upper limit, the dispersibility of the resin particles in the mixed powder is higher compared to when it exceeds the upper limit, and the carbon particles and water-resistant resin are more uniformly dispersed in the final water-repellent layer, thereby improving the power generation performance of the fuel cell. The average particle size of the thermosetting resin raw material particles can be determined by measuring it using a particle size distribution analyzer or by measuring the particle size of 500 randomly selected particles using an electron microscope and averaging the results. Furthermore, when using the thermosetting resin raw material coated carbon particles as a mixed powder containing powder (A) and powder (C), the average particle diameter of the core portion (carbon particles) of the thermosetting resin raw material coated carbon particles can be considered as the average particle diameter of the carbon particles constituting powder (A), and the average particle diameter of the thermosetting resin raw material coated carbon particles can be considered as the average particle diameter of the thermosetting resin raw material particles constituting powder (C).

[0025] The mixed powder comprises either powder (A) and powder (B), or powder (A) and powder (C).

[0026] When the mixed powder is a mixture of powder (A) and powder (B), the content of powder (B) is preferably 17 to 40% by mass, and more preferably 20 to 30% by mass, relative to the total amount of powder (A) and powder (B). When the content of powder (B) is above the lower limit, the strength of the water-repellent layer itself is improved compared to when it is below the lower limit. On the other hand, when the content of powder (B) is below the upper limit, the strength of the water-repellent layer itself is improved compared to when it exceeds the upper limit, and the electronic resistance of the water-repellent layer does not increase to such an extent that it becomes difficult to use for fuel cell applications, making it possible to form a more convenient water-repellent layer.

[0027] Furthermore, if the mixed powder is a mixed powder of powder (A) and powder (C), the content of powder (C) is preferably 15 to 60% by mass, more preferably 15 to 50% by mass, and even more preferably 25 to 35% by mass, relative to the total amount of powder (A) and powder (C). When the content of powder (C) is above the lower limit, the strength of the water-repellent layer itself is improved compared to when it is below the lower limit. On the other hand, when the content of powder (B) is below the upper limit, the strength of the water-repellent layer itself is improved compared to when it exceeds the upper limit, and the electronic resistance of the water-repellent layer does not increase to such an extent that it becomes difficult to use for fuel cell applications, making it possible to form a more convenient water-repellent layer. Furthermore, when the thermosetting resin raw material coated carbon particles are used alone as a mixed powder containing powder (A) and powder (C), the content of the coating portion (thermosetting resin raw material) of the thermosetting resin raw material coated carbon particles can be considered as the content of powder (C). When the thermosetting resin raw material coated carbon particles are used in combination with other thermosetting resin raw material particles, the sum of the content of the coating portion (thermosetting resin raw material) of the thermosetting resin raw material coated carbon particles and the content of the other thermosetting resin raw material particles can be considered as the content of powder (C).

[0028] Furthermore, the mixed powder may also contain powders consisting of other components besides powder (A), powder (B), and powder (C), to the extent that they do not impede the function of the resulting water-repellent layer and the effects of the present invention.

[0029] Furthermore, in the mixed powder, the ratio of the average particle diameter of powder (B) to the average particle diameter of powder (A) ([average particle diameter of powder (B)] / [average particle diameter of powder (A)]) and the ratio of the average particle diameter of powder (C) to the average particle diameter of powder (A) ([average particle diameter of powder (C)] / [average particle diameter of powder (A)]) are preferably 0.01 / 0.002 to 50 / 50, and more preferably 0.01 / 0.002 to 40 / 30. When the ratio of average particle diameters is above the lower limit, the strength of the water-repellent layer itself tends to improve more than when it is below the lower limit, while when the ratio of average particle diameters is below the upper limit, the strength of the water-repellent layer itself tends to improve more than when it exceeds the upper limit.

[0030] The mixed powder can be obtained by mixing powder (A) and powder (B), or powder (A) and powder (C), and powders consisting of other components as needed, in a predetermined ratio. There are no particular restrictions on the method of mixing these powders; for example, a known method that allows for sufficiently uniform dispersion and mixing of powder (A) and powder (B), or powder (A) and powder (C), and powders consisting of other components as needed, can be appropriately employed, such as a method of stirring and mixing using a commercially available stirrer. There are also no particular restrictions on the stirring conditions, and they can be set as appropriate. Furthermore, the mixed powder may be prepared by mixing (stirring) and grinding powder (A) and the fluoropolymer-based thermoplastic resin in a non-granular form (e.g., lump form, film form, etc.), or powder (A) and the thermosetting resin raw material in a non-granular form (e.g., lump form, film form, etc.), and powders consisting of other components as needed, using a commercially available stirrer that can also be used as a grinder, in order to satisfy the conditions for the mixed powder. Furthermore, the powder (A) may be added to the thermosetting resin raw material in a liquid or aqueous solution state, dispersed, and then dried to prepare the thermosetting resin raw material coated carbon particles. The mixed powder may also be prepared by adding and mixing other thermosetting resin raw material particles as needed.

[0031] In the film-forming process according to the present invention, the mixed powder is deposited on the surface of a porous substrate by a dry film-forming method to form a layer (mixed powder layer) consisting of the mixed powder. By depositing the mixed powder by a dry film-forming method, the resulting mixed powder layer maintains a uniform dispersion state between powder (A) and powder (B), or between powder (A) and powder (B), in the mixed powder before film formation.

[0032] There are no particular restrictions on the dry film formation method, and known dry film formation methods such as electrostatic screen printing and electrostatic coating can be used as appropriate. However, electrostatic screen printing is preferred because it allows for easier coating (film formation) of mixed powder having a desired particle size, and the thickness of the mixed powder layer obtained after coating can be adjusted to a desired thickness. Therefore, electrostatic screen printing is preferred in which a screen is placed above a porous substrate (such as a porous substrate for a gas diffusion layer) on which the coating film is to be formed, the mixed powder is placed on the screen, and then the mixed powder is rubbed onto the screen using a pressing member (such as a squeegee) to coat and form a film of the mixed powder. When electrostatic screen printing is used as the dry film formation method, various film formation conditions such as the type of screen (mesh) and the magnitude of the voltage can be set as appropriate according to the design of the water-repellent layer to be manufactured, and conditions used in known electrostatic screen printing methods can be used as appropriate.

[0033] In the aforementioned film formation process, the porous substrate on which the mixed powder is formed is not particularly limited as long as it is used for gas diffusion layers in fuel cells, and examples include carbon paper and carbon cloth. Furthermore, the thickness of the porous substrate is not particularly limited as long as it is a thickness that can be used in fuel cells, and can be set as appropriate, and is usually 100 to 300 μm.

[0034] Furthermore, in the film formation process, if the mixed powder is a mixture of powder (A) and powder (B), it is preferable to use a porous substrate as the porous substrate having at least the same resin as the resin constituting the fluoropolymer resin particles on its surface (for example, carbon paper surface-treated with the same resin as the resin constituting the fluoropolymer resin particles), and to form the mixed powder film on the surface of this porous substrate. This makes it possible to match the firing temperature at which the strength of the resulting water-repellent layer itself is highest with the firing temperature at which the interfacial strength between the water-repellent layer and the porous substrate is highest, thereby significantly improving the bonding strength between the final water-repellent layer and the porous substrate.

[0035] In a porous substrate having at least the same resin as that constituting the fluoropolymer resin particles on its surface, the amount of resin coating is preferably 1 to 20% by mass, and more preferably 3 to 10% by mass, relative to the entire porous substrate (including the amount of coated resin). If the amount of resin coating falls below the lower limit, the effect of using a porous substrate having at least the same resin as that constituting the fluoropolymer resin particles on its surface tends not to be fully obtained, while if the amount of resin coating exceeds the upper limit, the electronic resistance tends to increase.

[0036] The method for producing a porous substrate having at least one surface of the same resin as that which constitutes the fluoropolymer thermoplastic resin particles is not particularly limited as long as it is a method that can adhere the same resin as that which constitutes the fluoropolymer thermoplastic resin particles to at least one surface of the porous substrate. For example, a method can be employed in which the surface of the porous substrate is brought into contact with the same resin as that which constitutes the fluoropolymer thermoplastic resin particles in liquid, aqueous, or dispersion form, and then dried.

[0037] Furthermore, in the film-forming step, if the mixed powder is a mixed powder of powder (A) and powder (C), it is preferable to use a porous substrate as the porous substrate having at least one of the same raw materials and / or the same resin as at least one of the resins constituting the thermosetting resin on at least its surface (for example, carbon paper surface-treated with the same raw materials and / or the same resin as at least one of the resins constituting the thermosetting resin), and to form the mixed powder film on the surface of this porous substrate. This makes it possible to match the firing temperature at which the strength of the resulting water-repellent layer itself is highest with the firing temperature at which the interfacial strength between the water-repellent layer and the porous substrate is highest, thereby significantly improving the bonding strength between the final water-repellent layer and the porous substrate.

[0038] In a porous substrate having at least one of the same raw materials as the resin constituting the thermosetting resin and / or the same resin as the resin constituting the thermosetting resin on at least one surface, the amount of coating of the raw materials and / or the resin is preferably such that the amount of coating of the thermosetting resin (water-resistant resin) obtained by polycondensation (curing by heat treatment) on the entire porous substrate (including the amount of coating resin) is 13 to 23% by mass, and more preferably 13 to 21% by mass. If the amount of coating of the raw materials and / or the resin falls below the lower limit, the effect of using a porous substrate having at least one of the same raw materials as the resin constituting the thermosetting resin and / or the same resin as the resin constituting the thermosetting resin on at least one surface tends not to be fully obtained, on the other hand, if the amount of coating of the resin exceeds the upper limit, the electronic resistance tends to increase.

[0039] As a method for producing a porous substrate having at least one of the same raw materials as the resin constituting the thermosetting resin and / or the same resin as the resin constituting the thermosetting resin on at least one surface, there are no particular limitations as long as the method can be used to adhere the same raw materials as the resin constituting the thermosetting resin and / or the same resin as the resin constituting the thermosetting resin to at least one surface of the porous substrate. For example, a method can be employed in which the surface of the porous substrate is brought into contact with the same raw materials and / or the same resin in liquid, aqueous solution, or dispersion form, and then dried.

[0040] Furthermore, in the film formation process, the thickness of the resulting mixed powder layer is preferably 5 to 100 μm, and more preferably 5 to 50 μm. When the thickness of the mixed powder layer is above the lower limit, the drainage performance of the final water-repellent layer is further improved compared to when it is below the lower limit, and the power generation performance of the fuel cell tends to be further improved. On the other hand, when the thickness of the mixed powder layer is below the upper limit, the electronic resistance of the final water-repellent layer is reduced compared to when it exceeds the upper limit, and the power generation performance of the fuel cell tends to be further improved.

[0041] (consolidation process) The compaction process according to the present invention is a process of compacting the mixed powder layer by pressurizing it under conditions of 0.2 to 5 MPa (preferably 0.3 to 4.5 MPa, more preferably 0.4 to 4 MPa, and even more preferably 0.5 to 3.5 MPa). When the pressure is above the lower limit, compaction can be performed more efficiently than when it is below the lower limit, and the contact between the carbon particles is improved, further lowering the electronic resistance and making it possible to manufacture a structure of the desired design. On the other hand, when the pressure is below the upper limit, the destruction of the carbon fibers constituting the porous substrate can be sufficiently prevented compared to when it exceeds the upper limit, and the properties of the structure are sufficiently maintained during compaction, so the bonding strength between the porous substrate and the water-repellent layer, the strength of the water-repellent layer itself, and the power generation performance of the fuel cell are further improved. Furthermore, by compacting at a pressure below the upper limit, the uniform dispersion state of powder (A) and powder (B), or powder (A) and powder (C) in the mixed powder layer before compaction is maintained in the compacted mixed powder layer. Furthermore, the carbon particles constituting powder (A), the fluoropolymer resin particles constituting powder (B), and the thermosetting resin raw material particles constituting powder (C) maintain the average particle size of the particles used as raw materials.

[0042] The pressurization time when pressurizing the mixed powder layer is preferably 10 to 600 seconds, and more preferably 20 to 300 seconds. When the pressurization time is above the lower limit, the contact between the carbon particles is further improved compared to when it is below the lower limit, resulting in even lower electronic resistance, and the bonding strength between the water-repellent layer and the porous substrate, the strength of the water-repellent layer itself, and the power generation performance of the fuel cell tend to be further improved. On the other hand, when the pressurization time is below the upper limit, the destruction of the carbon fibers constituting the porous substrate can be sufficiently prevented compared to when it exceeds the upper limit, and the properties of the structure are sufficiently maintained during compaction, so the bonding strength between the water-repellent layer and the porous substrate, the strength of the water-repellent layer itself, and the power generation performance of the fuel cell tend to be further improved. Furthermore, by compacting with a pressurization time below the upper limit, the mixed powder layer after compaction tends to maintain a uniform dispersion state between powder (A) and powder (B), or between powder (A) and powder (C), in the mixed powder layer before compaction. Furthermore, the carbon particles constituting powder (A), the fluoropolymer resin particles constituting powder (B), and the thermosetting resin raw material particles constituting powder (C) tend to maintain the average particle size of the particles used as raw materials.

[0043] There are no particular restrictions on the method of pressurizing the mixed powder layer, and known pressurizing methods (pressing methods) such as flat plate presses and roll presses can be used as appropriate. There are also no particular restrictions on the temperature conditions when pressurizing the mixed powder layer, but from the viewpoint of energy efficiency, room temperature is preferred. Furthermore, in the present invention, a hot press, in which the mixed powder layer is pressed while being heated, may be used as the method of pressurizing the mixed powder layer.

[0044] The thickness, porosity, and other conditions of the compacted mixed powder layer are set such that the final water-repellent layer has the desired properties (for example, a BET specific surface area of ​​5 m²). 2 / g~50m 2 The amount of powder (A), powder (B), and powder (C) can be appropriately set according to the type of powder (A), powder (B), and powder (C), and the pressurizing conditions such as the pressure, pressurizing time, and pressurizing temperature during compaction can be appropriately adjusted accordingly.

[0045] (Water-repellent layer formation process) The water-repellent layer formation step according to the present invention is a step of firing the compacted mixed powder layer, thereby obtaining a gas diffusion layer on the surface of the porous substrate in which a water-repellent layer for a fuel cell is laminated, the water-repellent layer being made of a mixed bond of the carbon particle powder (A) and the fluoropolymer resin particle powder (B), or a mixed bond of the carbon particle powder (A) and a water-resistant resin (C) made of a thermosetting resin which is a polycondensate of the thermosetting resin raw material.

[0046] In the water-repellent layer formation step, when the mixed powder is a mixed powder of powder (A) and powder (B), the firing temperature is preferably within the range of -60°C to +85°C (more preferably -45°C to +85°C, even more preferably -30°C to +80°C, particularly preferably +10°C to +75°C, and most preferably +30°C to +70°C) relative to the melting point of the fluoropolymer resin. When the firing temperature is above the lower limit, compared to when it is below the lower limit, some interaction is formed between the resin and the surface functional groups of the carbon particles due to the melting or softening of the resin, thereby improving the strength of the water-repellent layer itself. In particular, when a porous substrate is used as the porous substrate, having at least the same resin on its surface as the resin constituting the fluoropolymer resin particles, the resin constituting the fluoropolymer resin particles and the resin on the surface of the porous substrate melt or soften at the same firing temperature, so the bonding strength between the water-repellent layer and the porous substrate is greatly increased. On the other hand, when the firing temperature is below the upper limit, structural collapse accompanied by a weight reduction of the water-repellent layer due to volatilization or decomposition of the carbon particles and the fluoropolymer resin particles is prevented more reliably than when the temperature exceeds the upper limit, thus improving the strength of the water-repellent layer itself. Furthermore, by firing at a temperature below the upper limit, the uniform dispersion state of powder (A) and powder (B) in the mixed powder layer before firing is maintained in the mixed bond, and the carbon particles constituting powder (A) and the fluoropolymer resin particles constituting powder (B) maintain the average particle size of the particles used as raw materials.

[0047] Furthermore, in the water-repellent layer formation step, when the mixed powder is a mixed powder of powder (A) and powder (C), the firing temperature is preferably 10 to 130°C lower (more preferably 20 to 130°C, and even more preferably 30 to 130°C lower) than the decomposition temperature of the thermosetting resin (water-resistant resin (C)), which is a polycondensate of the thermosetting resin raw materials. When the firing temperature is above the lower limit, the polycondensation reaction proceeds sufficiently, and the strength of the water-repellent layer itself is improved compared to when it is below the lower limit. When the firing temperature is below the upper limit, the bonding strength between the water-repellent layer and the porous substrate is improved compared to when it exceeds the upper limit. Furthermore, from the viewpoint of more reliably preventing structural collapse accompanied by a decrease in the weight of the water-repellent layer due to the volatilization or decomposition of the carbon particles or the thermosetting resin raw materials, and improving the strength of the water-repellent layer itself, the firing temperature is preferably 50 to 110°C lower (more preferably 50 to 90°C lower, and even more preferably 50 to 70°C lower) than the decomposition temperature of the water-resistant resin (C).

[0048] The decomposition temperature of the water-resistant resin (C) can be determined by measuring the thermogravimetric change using a known thermal analyzer, and from the resulting TG curve, it can be found as the temperature at which the weight changes from a rapid decrease to a gradual decrease in a temperature range above the temperature at which the thermosetting resin raw material is likely to have undergone sufficient polycondensation (reaction).

[0049] There are no particular restrictions on the firing time during the firing process, but for example, 1 to 120 minutes is preferred, and 1 to 60 minutes is more preferred. When the firing time is above the lower limit, the strength of the water-repellent layer tends to improve compared to when it is below the lower limit, because some interaction is formed between the surface functional groups of the carbon particles due to the melting or softening of the fluoropolymer resin, or the polycondensation reaction of the thermosetting resin raw material proceeds sufficiently. In particular, when a porous substrate is used as the porous substrate, having at least the same resin on its surface as the resin constituting the fluoropolymer resin particles, the bonding strength between the water-repellent layer and the porous substrate tends to increase significantly because the resin constituting the fluoropolymer resin particles and the resin on the surface of the porous substrate melt or soften at the same firing time. On the other hand, when the firing time is below the upper limit, the energy efficiency during the production of the water-repellent layer tends to improve further compared to when it exceeds the upper limit. Furthermore, when the mixed powder is a mixture of powder (A) and powder (B), firing for a time less than or equal to the upper limit tends to maintain a uniform dispersion state of powder (A) and powder (B) in the mixed powder layer before firing, without the powder (B) being thermally decomposed in the mixed bond, and the carbon particles constituting powder (A) and the fluorine-based thermoplastic resin particles constituting powder (B) tend to maintain the average particle size of the particles used as raw materials.

[0050] There are no particular restrictions on the gas atmosphere during firing; for example, it may be an oxidizing gas atmosphere containing oxygen or an inert gas atmosphere such as nitrogen. However, from the viewpoint of reducing costs and improving work efficiency, an air atmosphere is preferred. Similarly, there are no particular restrictions on the pressure conditions during firing, but from the viewpoint of reducing costs and improving work efficiency, atmospheric pressure (normal pressure) is preferred. Furthermore, there are no particular restrictions on the heating means used for firing; for example, known heating furnaces such as hot air furnaces and electric furnaces can be used.

[0051] In this way, by firing the compacted mixed powder layer, a water-repellent layer is formed consisting of a mixed bond in which powder (A) and powder (B) are bonded to each other, or a mixed bond in which powder (A) and a thermosetting resin (water-resistant resin (C)), which is a polycondensate of the thermosetting resin raw material, are bonded to each other, and a gas diffusion layer is obtained in which this water-repellent layer is laminated on the surface of the porous substrate.

[0052] In the mixed bond of powder (A) and powder (B), the uniform dispersion state of powder (A) and powder (B) in the mixed powder layer before firing is maintained, and the carbon particles constituting powder (A) and the fluoropolymer resin particles constituting powder (B) maintain the average particle size of the particles used as raw materials. Furthermore, in the mixed bond of powder (A) and water-resistant resin (C), powder (A) is uniformly dispersed in the water-resistant resin (C), and the carbon particles constituting powder (A) maintain the average particle size of the particles used as raw materials.

[0053] Furthermore, in a mixed bond of the powder (A) and the water-resistant resin (C), the water-resistant resin (C) is preferably a phenolic resin, silicone resin, polyurethane resin, urea resin, melamine resin, or acrylic resin, more preferably a melamine resin or a composite resin of melamine resin and acrylic resin, even more preferably a melamine resin from the viewpoint of energy efficiency during manufacturing, and particularly preferably a composite resin of melamine resin and acrylic resin from the viewpoint of improving the strength of the water-repellent layer itself. A water-repellent layer containing such a water-resistant resin (C) exhibits water resistance.

[0054] There are no particular restrictions on the thickness of the water-repellent layer, but 5 to 100 μm is preferred, and 5 to 50 μm is more preferred. When the thickness of the water-repellent layer is above the lower limit, the water-repellent layer can be more securely sandwiched between the catalyst layer and the substrate compared to when it is below the lower limit, so the strength of the water-repellent layer itself tends to improve further, and the electronic resistance is reduced, so the power generation performance tends to improve further. On the other hand, when the thickness of the water-repellent layer is below the upper limit, the electronic resistance is further reduced compared to when it exceeds the upper limit, so the power generation performance tends to improve further.

[0055] (Joining process) The bonding step according to the present invention is a step of bonding the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly via a fluorine-based surfactant, thereby obtaining an electrolyte membrane electrode gas diffusion layer assembly comprising the gas diffusion layer and the electrolyte membrane electrode assembly.

[0056] There are no particular restrictions on the fluorinated surfactant; for example, known fluorinated surfactants having a perfluoroalkyl group and a hydrophilic group such as a carboxyl group or a sulfonic acid group in their molecule, such as perfluorooctanoic acid and perfluorooctanesulfonic acid, can be used.

[0057] There are no particular restrictions on the electrolyte membrane electrode assembly (MEA), and conventionally known electrolyte membrane electrode assemblies used in fuel cells can be used. For example, an electrolyte membrane electrode assembly 3 having a structure in which an electrolyte membrane 1 is sandwiched between two catalyst layers (electrodes) 2a and 2b, as shown in Figure 1, can be used. There are no particular restrictions on the electrolyte membrane, and for example, a solid electrolyte membrane made of a fluororesin having sulfonic acid groups at its ends can be used. There are no particular restrictions on the catalyst layer, and for example, a catalyst layer on which a precious metal such as platinum is supported can be used.

[0058] The bonding step is a step of bonding the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly via a fluorine-based surfactant. In this bonding step, first, the surface of the water-repellent layer in the gas diffusion layer is surface-treated with the fluorine-based surfactant to adhere the fluorine-based surfactant to the surface of the water-repellent layer. There are no particular restrictions on the surface treatment method; for example, a method of applying or spraying the fluorine-based surfactant onto the surface of the water-repellent layer in the gas diffusion layer and drying it can be used. Alternatively, the gas diffusion layer may be floated in the fluorine-based surfactant so that the surface of the water-repellent layer is in contact with the liquid surface of the fluorine-based surfactant, and then dried. At this time, by surface-treating the water-repellent layer with the fluorine-based surfactant (especially the fluorine-based surfactant in liquid or solution form) so that the fluorine-based surfactant penetrates into the interior of the water-repellent layer, not only the bonding strength between the water-repellent layer and the catalyst layer can be improved, but also the strength of the water-repellent layer itself and the bonding strength between the water-repellent layer and the porous substrate can be improved.

[0059] The ratio of the amount of the surfactant supported to the mass of the gas diffusion layer (the loading rate of the fluorine-based surfactant) is preferably 5 to 50% by mass, and more preferably 15 to 40% by mass. If the loading rate of the fluorine-based surfactant falls below the lower limit, sufficient bonding strength tends not to be obtained, while if the loading rate of the fluorine-based surfactant exceeds the upper limit, costs tend to increase.

[0060] Furthermore, the amount of the fluorine-based surfactant supported per unit area of ​​the water-repellent layer surface is 1.5 to 10 mg / cm². 2 Preferably, 2-7 mg / cm³ 2 This is more preferable. If the amount of the fluorine-based surfactant supported falls below the lower limit, sufficient bonding strength tends not to be obtained, while if the amount of the fluorine-based surfactant supported exceeds the upper limit, costs tend to increase.

[0061] Next, the gas diffusion layer, which has been surface-treated with the fluorine-based surfactant, and the electrolyte membrane electrode assembly are superimposed such that the surface of the water-repellent layer in the gas diffusion layer treated with the fluorine-based surfactant and the surface of one of the catalyst layers (electrodes) of the electrolyte membrane electrode assembly come into contact, and if necessary, are pressed and compacted to obtain an electrolyte membrane electrode gas diffusion layer assembly in which the gas diffusion layer and the electrolyte membrane electrode assembly are joined.

[0062] There are no particular restrictions on the pressurization method; for example, known pressurization methods (pressing methods) such as flat plate presses and roll presses can be used as appropriate. Alternatively, a hot press, which involves heating while applying pressure, may also be used.

[0063] There are no particular restrictions on the pressurization conditions, but for example, the pressure is preferably 0.2 to 5 MPa, more preferably 1 to 4 MPa; the pressurization time is preferably 1 to 15 minutes, more preferably 0.1 to 10 minutes; and the temperature is preferably 60 to 200°C, more preferably 80 to 180°C. By pressurizing under these conditions, it is possible to bond the gas diffusion layer and the electrolyte membrane electrode assembly with a higher bonding strength.

[0064] [Electrolyte membrane electrode gas diffusion layer assembly for fuel cells] The electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention is A gas diffusion layer comprising a porous substrate and a gas diffusion layer comprising a gas diffusion layer comprising a gas diffusion layer comprising a gas diffusion layer having a porous substrate and a gas diffusion layer having It comprises an electrolyte membrane electrode assembly, The water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly are bonded together via a fluorine-based surfactant.

[0065] Here, the "porous substrate," "carbon particles," "powder (A)," "fluoropolymer-based thermoplastic resin particles," "powder (B)," "thermosetting resin raw material particles," "powder (C)," "mixed powder," "water-resistant resin (C)," "mixed assembly," "water-repellent layer," "gas diffusion layer," "electrolyte membrane electrode assembly," "catalyst layer," and "fluoropolymer-based surfactant" that constitute the electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention are the same as those described in the method for manufacturing the electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention (the preferred conditions are also the same).

[0066] The electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention comprises the porous substrate, a water-repellent layer laminated on the surface of the porous substrate, and the electrolyte membrane electrode assembly. The water-repellent layer consists of a calcined product of a mixed powder containing powder (A) and powder (B), or a calcined product of a mixed powder containing powder (A) and powder (C), wherein the calcined product consists of a mixed bond of powder (A) and powder (B), or a mixed bond of powder (A) and the water-resistant resin (C). The water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly are bonded together via a fluorine-based surfactant.

[0067] In the aforementioned water-repellent layer, the BET specific surface area is 5 m². 2 / g~100m 2 It is preferable that the amount be / g, and the amount is 10-50m 2 It is more preferable that the BET specific surface area is / g. When the BET specific surface area is above the lower limit, gas diffusion is improved and power generation performance tends to be further improved compared to when it is below the lower limit. On the other hand, when the BET specific surface area is below the upper limit, the strength of the structure is higher and the strength of the water-repellent layer itself tends to be further improved compared to when it exceeds the upper limit.

[0068] In addition, in the water-repellent layer, the pore volume is preferably 0.01 to 0.2 cm 2 / g, and more preferably 0.01 to 0.1 cm 2 / g. When the pore volume is at least the lower limit, the gas diffusivity is improved and the power generation performance tends to be further improved as compared with the case where it is less than the lower limit. On the other hand, when the pore volume is at most the upper limit, the strength of the structure is increased and the strength of the water-repellent layer itself tends to be further improved as compared with the case where it exceeds the upper limit.

[0069] The BET specific surface area and pore volume of the water-repellent layer can be determined by the following method. That is, first, the water-repellent layer to be measured is cooled to the liquid nitrogen temperature (-196°C), nitrogen gas is introduced at a predetermined pressure, and the nitrogen adsorption amount at the equilibrium pressure is determined by a constant volume gas adsorption method or a gravimetric method. Next, the pressure of the introduced nitrogen gas is gradually increased, and the nitrogen adsorption amount at each equilibrium pressure is determined. Then, a nitrogen adsorption isotherm is obtained by plotting the obtained nitrogen adsorption amount against the equilibrium pressure. Thereafter, the specific surface area of the water-repellent layer is determined from the obtained nitrogen adsorption isotherm by the BET isothermal adsorption equation. Further, the pore volume of the water-repellent layer is determined by calculating from the nitrogen adsorption amount at P (adsorption equilibrium pressure) / P0 (saturated vapor pressure) = 0.95 of the nitrogen adsorption isotherm. When the water-repellent layer to be measured is in a state laminated on a porous substrate or the like, the BET specific surface area and pore volume can be determined by scraping out the water-repellent layer from the laminate and measuring it.

[0070] The structure of the electrolyte membrane electrode gas diffusion layer laminate for a fuel cell of the present invention is not particularly limited. For example, as shown in FIG. 1, an electrolyte membrane electrode laminate 3 having a structure in which two electrolyte membranes 1 are sandwiched between two catalyst layers (electrodes) 2a and 2b, and a gas diffusion layer 6 in which a porous substrate 4 and a water-repellent layer 5 are laminated, and a structure in which the catalyst layer 2a and the water-repellent layer 5 are joined via a fluorine-based surfactant layer 7 can be mentioned.

[0071] Furthermore, in the electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention, it is preferable that the fluorine-based surfactant penetrates the water-repellent layer 5. This improves the strength of the water-repellent layer 5 itself. Moreover, it is preferable that the fluorine-based surfactant is present at the interface between the water-repellent layer 5 and the porous substrate 4. This tends to improve the bonding strength between the water-repellent layer 5 and the porous substrate 4. In Figure 1, region S indicates a region where the fluorine-based surfactant may be present, and includes the fluorine-based surfactant layer 7, the water-repellent layer 5, the vicinity of the surface of the porous substrate 4 on the water-repellent layer 5 side, and the vicinity of the surface of the catalyst layer 2a on the fluorine-based surfactant layer 7 side.

[0072] Furthermore, the electrolyte membrane electrode gas diffusion layer assembly for fuel cells of the present invention comprises the porous substrate, a water-repellent layer laminated on the surface of the porous substrate, and the electrolyte membrane electrode assembly. Other components (for example, other layers besides the porous substrate, the water-repellent layer, and the electrolyte membrane electrode assembly) and characteristics (for example, conditions such as the BET surface area and pore capacity of the gas diffusion layer as a whole) are not particularly limited. [Examples]

[0073] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples. The carbon particles (hereinafter also referred to as "CB particles"), fluoropolymer resin particles, thermosetting resin raw material particles, porous substrate, surfactant, and electrolyte membrane electrode assembly used in the examples and comparative examples are shown below.

[0074] (CB particles) • Hydrophilic carbon particles (manufactured by Nishimura Graphite Co., Ltd., product name: Hydrophilic Graphite MC2, average primary particle diameter: 46 nm (0.046 μm), in Table 1, the type of CB particle is simply referred to as "hydrophilic"). • Hydrophobic carbon particles (manufactured by Denka Co., Ltd., product name: Denka Black Li400, average primary particle diameter: 48 nm (0.048 μm), in Table 1, the type of CB particle is simply referred to as "hydrophobic").

[0075] The "hydrophilicity" and "hydrophobicity" of the CB particles were evaluated using the so-called Methanol Wettability method (see Mitsuru Ochiai, Aerosol Research, 1990, vol. 5, pp. 32-43). Specifically, water (methanol concentration: 0 mass%) and methanol aqueous solutions of different methanol concentrations were prepared. The CB particles used in each example were gently added to the water and methanol aqueous solutions of each concentration and shaken lightly several dozen times. The presence or absence of dispersion of the CB particles was visually confirmed, and the methanol concentration at which the CB particles dispersed was determined (confirming dispersibility in water or methanol aqueous solutions). (The methanol concentration (mass%) required to completely wet the CB particles floating on the surface of the water or methanol aqueous solution was used as a scale to evaluate properties such as hydrophilicity or hydrophobicity. Note that the lower the methanol concentration at which the CB particles disperse, the higher the hydrophilicity). In the evaluation, if the methanol concentration in the aqueous solution in which the CB particles were dispersed was less than 2% by mass (Methanol Wettability: <2), the CB particles were evaluated as "hydrophilic" particles. On the other hand, if the CB particles did not disperse in methanol aqueous solutions with a methanol concentration of less than 2% by mass, but dispersed in methanol aqueous solutions with a methanol concentration of 2% by mass or more (Methanol Wettability: ≥2), the CB particles were evaluated as "hydrophobic" particles. When this evaluation method was adopted, the hydrophilic carbon particles dispersed in water with a methanol concentration of 0% by mass. On the other hand, the hydrophobic carbon particles did not disperse in methanol aqueous solutions with a methanol concentration of less than 2% by mass, but dispersed in methanol aqueous solutions with a methanol concentration of 2% by mass. As a result of this evaluation, Figure 2 shows photographs of the state when the hydrophilic carbon particles and the hydrophobic carbon particles were added to water (methanol concentration: 0% by mass), respectively. The left side of the photograph in Figure 2 shows the state when the hydrophilic carbon particles were added to water, confirming that the hydrophilic carbon particles were dispersed in water. In contrast, the right side of the photograph in Figure 2 shows the result when hydrophobic carbon particles are added to water. In this case, it can be seen that the particles float on the water and are not dispersed at all.

[0076] (Fluorine-based thermoplastic resin particles) • Perfluoroethylene propene copolymer (manufactured by Daikin Industries, Ltd., product name: Neoflon FEP NCX-11, average particle size: 15 μm, melting point: 260°C. Hereinafter referred to as "FEP"). • Polytetrafluoroethylene (manufactured by Kitamura Co., Ltd., product name: KTL-500F, average particle size: 0.2 μm, melting point: 327°C. Hereinafter referred to as "PTFE").

[0077] (Thermosetting resin raw material particles) • Low-condensate of methylolmelamine (raw material for melamine resin (melamine resin having amino groups, imino groups, methylol groups and alkyl ether groups), manufactured by Nippon Carbide Industries Co., Ltd., product name: Nikarezin S260, average primary particle size: 20 μm, decomposition temperature of resin (melamine resin) after polycondensation: 280°C). Methylated melamine (a raw material for melamine resin (melamine resin having amino groups, imino groups, methylol groups, and alkyl ether groups)) and methylated melamine aqueous solution manufactured by Nippon Carbide Industries, Ltd. (product name: Nikalac MX035, colorless transparent liquid) were used to prepare methylated melamine-coated CB particles). • Acrylic resin (dried acrylic resin aqueous solution (manufactured by Nippon Carbide Industries Co., Ltd., product name: Nikazol RX1033) (aggregate of primary particles) pulverized using a stirrer, average primary particle diameter: 0.1 μm, average secondary particle diameter: 30 μm or less).

[0078] (Porous base material) • Carbon paper surface-treated with FEP (manufactured by Chemix Co., Ltd., product name: TGP-H-060H, FEP content: 5% by mass, film thickness: approximately 200 μm. Hereafter referred to as "FEP-CP"). • Carbon paper surface-treated with PTFE (manufactured by Chemix Co., Ltd., product name: TGP-H-060H, PTFE content: 5% by mass, film thickness: approximately 200 μm. Hereafter referred to as "PTFE-CP"). • Carbon paper surface-treated with methylolmelamine (untreated carbon paper (Chemix Co., Ltd., product name: TGP-H-060) was floated on the surface of an approximately 30% by mass aqueous solution of methylolmelamine (Nippon Carbide Industries Co., Ltd., product name: Nikarezin S260) for 5 minutes, and then dried. Hereinafter referred to as "methylolmelamine-CP").

[0079] (Surfactants) • Fluorine-based surfactant (manufactured by AGC Seimi Chemical Co., Ltd., product name: Surflon S-231, properties: liquid, active ingredient concentration: 30%). • Non-fluorinated surfactant (manufactured by AGC Seimi Chemical Co., Ltd., properties: liquid, active ingredient concentration: 100%).

[0080] (Electrolyte membrane electrode assembly) • Electrolyte membrane electrode assembly (Electrolyte membrane material: fluororesin-based polymer membrane such as Nafion; Catalyst layer (electrode) material: Platinum-supported carbon, where a platinum catalyst mainly of several nanometers in diameter is supported on carbon particles of about 50 nm in diameter).

[0081] (Examples 1-3) [Fabrication of gas diffusion layers for fuel cells] The types of carbon dioxide (CB) particles shown in Table 1 and the types of fluoropolymer resin particles or thermosetting resin raw material particles shown in Table 1 were mixed at the mixing ratio (by mass) shown in Table 1 using a stirrer (manufactured by Tescom Electric Co., Ltd., product name: OML-2) at 20,000 rpm for 5 minutes to obtain a mixed powder. The obtained mixed powder was coated onto the surface of the porous substrate (carbon paper) of the type shown in Table 1 by electrostatic screen printing (dry film formation method) to form a mixed powder layer. For the electrostatic screen printing method, an electrostatic screen printing apparatus (manufactured by Berg Industries Co., Ltd., product name: T-1) and a screen mesh (manufactured by Berg Industries Co., Ltd., product name: Electrostatic Screen, mesh opening: 72 μm) were used. A voltage of 1.75 kV was applied between the carbon paper and the screen mesh, and the mixed powder was placed on the screen mesh and rubbed with a squeegee to cause the mixed powder to fall from the mesh onto the carbon paper and form a film.

[0082] Next, the mixed powder layer laminated on the surface of the carbon paper was compacted by pressurizing it at a pressure of 3 MPa for 1 minute using a flat plate press. The compacted mixed powder layer was then fired in an electric furnace at atmospheric pressure and the temperature shown in Table 1 for 30 minutes to form a water-repellent layer on the carbon paper, consisting of CB particles and fluoropolymer resin particles or a thermosetting resin which is a polycondensate of the thermosetting resin raw material. A laminate of carbon paper and the water-repellent layer (gas diffusion layer for fuel cell) was obtained.

[0083] Furthermore, the thermosetting resin formed in Example 3, which is a polycondensate of the thermosetting resin raw materials, is clearly a water-resistant resin because, given the resin raw materials (low-condensate of methylolmelamine) and the firing conditions (heating temperature and heating time), it is clear that the polycondensation reaction of the resin raw materials proceeded sufficiently and a melamine resin was obtained.

[0084] [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] A fluorinated surfactant aqueous solution with an active ingredient concentration of 15% was prepared by adding water to a fluorinated surfactant. The fuel cell gas diffusion layer was floated in this fluorinated surfactant aqueous solution for about 20 seconds so that the surface of the water-repellent layer in the gas diffusion layer was in contact with the surface of the fluorinated surfactant solution. After that, the gas diffusion layer was removed, air-dried overnight, and then vacuum-dried at 25°C for 2 hours to obtain a gas diffusion layer in which the surface of the water-repellent layer was treated with the fluorinated surfactant.

[0085] The surfactant loading rate in the gas diffusion layer surface-treated with this fluorine-based surfactant and the amount of surfactant loaded per unit area on the surface of the water-repellent layer were determined as follows. Specifically, the mass of the gas diffusion layer was measured before and after surface treatment with the surfactant, and the difference in mass of the gas diffusion layer before and after surface treatment was taken as the amount of surfactant loaded. This was divided by the mass of the gas diffusion layer before surface treatment to obtain the ratio of the amount of surfactant loaded to the mass of the gas diffusion layer (surfactant loading rate) [unit: mass %]. Furthermore, the difference in mass of the gas diffusion layer before and after surface treatment (amount of surfactant loaded) was divided by the surface area of ​​the water-repellent layer in the gas diffusion layer to obtain the amount of surfactant loaded per unit area on the surface of the water-repellent layer [unit: g / m2 We calculated the following. The results are shown in Table 1.

[0086] Next, the gas diffusion layer surface-treated with the fluorine-based surfactant and the electrolyte membrane electrode assembly were superimposed so that the surface of the water-repellent layer in the gas diffusion layer treated with the fluorine-based surfactant and the surface of one of the catalyst layers (electrodes) of the electrolyte membrane electrode assembly were in contact. Then, the assembly was compacted by pressurizing it with a flat plate press at a pressure of 3 MPa and a temperature of 130°C for 5 minutes to obtain an electrolyte membrane electrode gas diffusion layer assembly.

[0087] (Example 4) [Fabrication of gas diffusion layers for fuel cells] The types of CB particles shown in Table 1 were dispersed in an aqueous solution of methylated melamine so that the mass ratio of CB particles to methylated melamine on a solid content basis (CB particles / methylated melamine) was 83 / 17. After drying, the CB particles were coated with methylated melamine to obtain a powder of resin-coated CB particles. This powder of resin-coated CB particles and acrylic resin particles were mixed using a stirrer (manufactured by Tescom Electric Co., Ltd., product name: OML-2) at 20,000 rpm for 5 minutes so that the mass ratio of CB particles to methylated melamine to acrylic resin particles (CB particles / methylated melamine / acrylic resin particles) was 70 / 7.5 / 22.5 to obtain a mixed powder.

[0088] In the resulting mixed powder, the core of the resin-coated CB particles is considered to be the carbon particles contained in the mixed powder, and the resin-coated CB particles and acrylic resin particles are considered to be the thermosetting resin raw material particles contained in the mixed powder. Furthermore, in the electrostatic screen printing described later, a screen mesh with a mesh opening of 30 μm is used to form the mixed powder layer, so it is clear that the average particle diameter of the resin-coated CB particles considered to be thermosetting resin raw material particles is 30 μm or less. Also, since the average primary particle diameter of the CB particles is 46 nm, it is clear that the average particle diameter of the resin-coated CB particles considered to be thermosetting resin raw material particles is 46 nm or more.

[0089] Next, in the same manner as in Example 1, except that a screen mesh with a mesh opening of 30 μm (manufactured by Berg Industries Co., Ltd., product name: electrostatic screen) was used, the obtained mixed powder was coated onto the surface of a porous substrate (carbon paper) of the type shown in Table 1 by electrostatic screen printing (dry film formation method) to form a mixed powder layer. Furthermore, the mixed powder layer was compacted, and the compacted mixed powder layer was fired to form a water-repellent layer on the carbon paper consisting of CB particles and a thermosetting resin which is a polycondensate of the thermosetting resin raw material, thereby obtaining a laminate of carbon paper and the water-repellent layer (gas diffusion layer for fuel cell).

[0090] Furthermore, it is clear from the resin raw materials (methylated melamine and acrylic resin) and firing conditions (heating temperature and heating time) that the polycondensation reaction of the resin raw materials has proceeded sufficiently, and a composite resin of melamine resin and acrylic resin has been obtained, thus it is clear that the thermosetting resin is a water-resistant resin.

[0091] [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] The surface of the water-repellent layer of the obtained fuel cell gas diffusion layer was treated with a fluorine-based surfactant in the same manner as in Example 1, and an electrolyte membrane electrode gas diffusion layer assembly was then fabricated. The loading rate of the surfactant in the gas diffusion layer surface-treated with the fluorine-based surfactant and the amount of surfactant loaded per unit area on the surface of the water-repellent layer were determined in the same manner as in Example 1. These results are shown in Table 1.

[0092] (Comparative Example 1) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] A non-fluorinated surfactant was used instead of a fluorinated surfactant, and an aqueous solution of the non-fluorinated surfactant with an active ingredient concentration of 25% was prepared. The gas diffusion layer for the fuel cell was floated in this aqueous solution of the non-fluorinated surfactant for approximately 300 seconds. Except for these steps, a gas diffusion layer with a water-repellent layer surface treated with the non-fluorinated surfactant was fabricated in the same manner as in Example 1, and an electrolyte membrane electrode gas diffusion layer assembly was then fabricated. The loading rate of the surfactant in the gas diffusion layer surface-treated with the non-fluorinated surfactant and the amount of surfactant loaded per unit area on the surface of the water-repellent layer were determined in the same manner as in Example 1. These results are shown in Table 1.

[0093] (Comparative Example 2) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] An electrolyte membrane electrode gas diffusion layer assembly was fabricated in the same manner as in Example 1, except that the surface of the water-repellent layer of the fuel cell gas diffusion layer was not treated with a surfactant.

[0094] (Comparative Example 3) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] An electrolyte membrane electrode gas diffusion layer assembly was fabricated in the same manner as in Example 2, except that the surface of the water-repellent layer of the fuel cell gas diffusion layer was not treated with a surfactant.

[0095] (Comparative Example 4) [Fabrication of gas diffusion layers for fuel cells] The types of carbon dioxide particles shown in Table 1, the types of fluoropolymer resin particles shown in Table 1, and water were mixed at the mixing ratio (by mass) shown in Table 1 using a stirrer (manufactured by Thinky Co., Ltd., product name: Awatori Rentaro ARE310) at 2000 rpm for 1 minute to obtain a paste containing hydrophilic carbon dioxide particles and PTFE particles. The obtained paste was applied to the surface of the porous substrate (carbon paper) of the type shown in Table 1 using an applicator (manufactured by BEVS INDUSTRIAL Co., Ltd., product name: BEVS) to form a paste layer.

[0096] Next, the paste layer laminated on the surface of the carbon paper was air-dried at room temperature for about one day, and then fired in an electric furnace at atmospheric pressure and the temperature shown in Table 1 for 30 minutes. A water-repellent layer consisting of CB particles and fluoropolymer resin particles was formed on the carbon paper, and a laminate of carbon paper and the water-repellent layer (gas diffusion layer for fuel cell) was obtained.

[0097] [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] An electrolyte membrane electrode gas diffusion layer assembly was fabricated in the same manner as in Example 2, except that the surface of the water-repellent layer of the fuel cell gas diffusion layer was not treated with a surfactant.

[0098] (Comparative Example 5) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] A gas diffusion layer with a non-fluorinated surfactant surface was prepared in the same manner as in Example 3, except that a non-fluorinated surfactant was used instead of a fluorinated surfactant, an aqueous solution of the non-fluorinated surfactant with an active ingredient concentration of 25%, and the fuel cell gas diffusion layer was floated in this aqueous solution for approximately 300 seconds. Furthermore, an electrolyte membrane electrode gas diffusion layer assembly was fabricated. The surfactant loading rate in the gas diffusion layer surface-treated with the non-fluorinated surfactant and the amount of surfactant loaded per unit area on the surface of the water-repellent layer were determined in the same manner as in Example 1. The results are shown in Table 1.

[0099] (Comparative Example 6) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] An electrolyte membrane electrode gas diffusion layer assembly was fabricated in the same manner as in Example 3, except that the surface of the water-repellent layer of the fuel cell gas diffusion layer was not treated with a surfactant.

[0100] (Comparative Example 7) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] A non-fluorinated surfactant was used instead of a fluorinated surfactant, and an aqueous solution of the non-fluorinated surfactant with an active ingredient concentration of 25% was prepared. The gas diffusion layer for the fuel cell was floated in this aqueous solution of the non-fluorinated surfactant for approximately 300 seconds. Except for these steps, a gas diffusion layer with a water-repellent surface treated with the non-fluorinated surfactant was fabricated in the same manner as in Example 4, and an electrolyte membrane electrode gas diffusion layer assembly was then fabricated. The surfactant loading rate in the gas diffusion layer surface-treated with the non-fluorinated surfactant and the amount of surfactant loaded per unit area on the surface of the water-repellent layer were determined in the same manner as in Example 1. These results are shown in Table 1.

[0101] (Comparative Example 8) [Fabrication of electrolyte membrane electrode gas diffusion layer assembly] An electrolyte membrane electrode gas diffusion layer assembly was fabricated in the same manner as in Example 4, except that the surface of the water-repellent layer of the fuel cell gas diffusion layer was not treated with a surfactant.

[0102] <Joining strength> The electrolyte membrane electrode gas diffusion layer assemblies obtained in the examples and comparative examples were subjected to a 90-degree peel test using an electric measuring stand (manufactured by IMADA Co., Ltd., product name: MX2-500N-L-FA), and the peel strength (unit: N / m) was measured and defined as the bonding strength. The results are shown in Table 1 and Figure 3.

[0103] [Table 1]

[0104] As shown in Table 1 and Figure 3, when the surface of the water-repellent layer produced by dry deposition was surface-treated with a fluorine-based surfactant (Examples 1-4), the bonding strength between the water-repellent layer in the gas diffusion layer and the catalyst layer of the electrolyte membrane electrode assembly was found to be higher compared to when the water-repellent layer was produced by paste coating and no surface treatment with a surfactant was performed (Comparative Example 4). On the other hand, when the surface of the water-repellent layer produced by dry deposition was surface-treated with a non-fluorine-based surfactant (Comparative Examples 1, 5, and 7), the bonding strength between the water-repellent layer in the gas diffusion layer and the catalyst layer of the electrolyte membrane electrode assembly was found to be lower compared to when the water-repellent layer was produced by paste coating and no surface treatment with a surfactant was performed (Comparative Example 4).

[0105] Furthermore, it was found that when the surface of the water-repellent layer produced by dry film deposition was surface-treated with a fluorine-based surfactant (Examples 1-4), the bonding strength between the water-repellent layer in the gas diffusion layer and the catalyst layer of the electrolyte membrane electrode assembly was significantly higher compared to when the water-repellent layer was produced by dry film deposition and no surface treatment with a surfactant was performed (Comparative Examples 2, 3, 6, 8).

[0106] <Electron microscopy and elemental mapping> The cross-sections of the water-repellent layers of the electrolyte membrane electrode gas diffusion layer assemblies fabricated in Example 2 and Comparative Example 3 were observed using a scanning electron microscope (SEM, Hitachi High-Tech Corporation, product name: Regulus8230) at an acceleration voltage of 3kV. Elemental mapping was performed using an elemental detector (EDS, Bruker, product name: QUANTAXFlatQUAD) to obtain SEM-EDS images (elemental mapping images). Figure 4 shows the SEM-EDS image of the cross-section of the water-repellent layer obtained in Example 2, and Figure 5 shows the SEM-EDS image of the cross-section of the water-repellent layer obtained in Comparative Example 3. In Figures 4 and 5, carbon atoms are shown in blue (black in black and white images), and fluorine atoms are shown in red (dark gray in black and white images).

[0107] As shown in Figures 4 and 5, it was found that fluorine atoms were uniformly distributed in both the water-repellent layer obtained in Example 2 and the water-repellent layer obtained in Comparative Example 3. However, when the fluorine atom content was determined based on the SEM-EDS images shown in Figures 4 and 5, it was found to be 5.6 mass% in the water-repellent layer obtained in Example 2 and 3.5 mass% in the water-repellent layer obtained in Comparative Example 3. The water-repellent layer obtained in Example 2 had 1.6 times more fluorine content than the water-repellent layer obtained in Comparative Example 3. This indicates that treating the surface of a water-repellent layer produced by dry deposition with a fluorine-based surfactant not only treats the surface of the water-repellent layer, but also allows the fluorine-based surfactant to penetrate into the interior of the water-repellent layer.

[0108] Based on these results, it is considered that when the surface of a water-repellent layer fabricated by dry deposition is treated with a fluorine-based surfactant, not only is the surface of the water-repellent layer treated with the fluorine-based surfactant, but the fluorine-based surfactant also penetrates into the interior of the water-repellent layer. As a result, the strength of the water-repellent layer itself is improved, and the bonding strength between the water-repellent layer and the catalyst layer becomes significantly higher compared to when the surface of the water-repellent layer fabricated by dry deposition is not treated with a surfactant. [Industrial applicability]

[0109] As described above, according to the present invention, by using a fluorine-based surfactant when joining the gas diffusion layer for fuel cells and the electrolyte membrane electrode assembly, it is possible to achieve a high bonding strength between the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly.

[0110] Therefore, the method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly of the present invention is useful as a method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly used in fuel cells and the like. [Explanation of Symbols]

[0111] 1: Electrolyte membrane 2a and 2b: Catalyst layer (electrode) 3: Electrolyte membrane electrode assembly 4: Porous base material 5: Water-repellent layer 6: Gas diffusion layer 7: Fluorine-based surfactant layer S: Region where fluorinated surfactants may be present

Claims

1. A film formation step in which a mixed powder containing carbon particle powder (A) with an average particle diameter of 0.002 to 50 μm and fluoropolymer thermoplastic resin particle powder (B) with an average particle diameter of 0.01 to 50 μm or thermosetting resin raw material particle powder (C) with an average particle diameter of 0.01 to 50 μm is deposited on the surface of a porous substrate by a dry film formation method to form a mixed powder layer, A compaction step in which the mixed powder layer is pressurized under conditions of 0.2 to 5 MPa to compact it, A water-repellent layer formation step is performed to obtain a gas diffusion layer in which a water-repellent layer for a fuel cell is laminated on the surface of the porous substrate by firing the compacted mixed powder layer, the water-repellent layer being made of a mixed bond of the carbon particle powder (A) and the fluoropolymer resin powder (B), or a mixed bond of the carbon particle powder (A) and a water-resistant resin (C) made of a thermosetting resin which is a polycondensate of the raw materials, A bonding step to obtain an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell comprising the gas diffusion layer and the electrolyte membrane electrode assembly, by bonding the water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly via a fluorine-based surfactant. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for fuel cells, characterized by containing the following:

2. If the mixed powder is a mixed powder of powder (A) and powder (B), the content of powder (B) is 17 to 40% by mass relative to the total amount of powder (A) and powder (B). If the mixed powder is a mixture of powder (A) and powder (C), the content of powder (C) is 15 to 60% by mass of the total amount of powder (A) and powder (C). A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to feature 1.

3. The firing temperature in the water-repellent layer formation step is If the mixed powder is a mixed powder of powder (A) and powder (B), then the temperature is within the range of -60°C to +85°C relative to the melting point of the fluoropolymer resin. If the mixed powder is a mixture of powder (A) and powder (C), the temperature is 10 to 130°C lower than the decomposition temperature of the thermosetting resin. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to feature 1.

4. A method for producing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to claim 1, characterized in that no dispersant is used.

5. The fluoropolymer is at least one resin selected from the group consisting of polytetrafluoroethylene, perfluoroethylene propene copolymer, and polyvinylidene fluorite. The water-resistant resin (C) is at least one resin selected from the group consisting of phenolic resin, silicone resin, polyurethane resin, urea resin, melamine resin, and acrylic resin. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to feature 1.

6. In the aforementioned film formation process, If the mixed powder is a mixed powder of powder (A) and powder (B), the mixed powder is formed as a film on the surface of the porous substrate having at least the same resin as the resin constituting the fluoropolymer resin particles on its surface. If the mixed powder is a mixed powder of powder (A) and powder (C), the mixed powder is formed on the surface of the porous substrate having at least one of the same raw materials and / or the same resin as at least one of the resins constituting the thermosetting resin on its surface. A method for manufacturing an electrolyte membrane electrode gas diffusion layer assembly for a fuel cell according to feature 1.

7. A gas diffusion layer comprising a porous substrate and a gas diffusion layer comprising a gas diffusion layer comprising a gas diffusion layer comprising a gas diffusion layer comprising a porous substrate and a gas diffusion layer comprising a gas diffusion layer made of a mixed powder containing a powder of carbon particles (A) with an average particle diameter of 0.002 to 50 μm and a powder of fluoropolymer thermoplastic resin particles (B) with an average particle diameter of 0.01 to 50 μm or a powder of thermosetting resin raw material particles (C) with an average particle diameter of 0.01 to 50 μm, wherein the gas diffusion layer comprises a gas diffusion layer made of a mixed bond of the carbon particle powder (A) and the fluoropolymer thermoplastic resin powder (B), or a gas diffusion layer made of a mixed bond of the carbon particle powder (A) and a water-resistant resin (C) which is a thermosetting resin that is a polycondensate of the raw materials, It comprises an electrolyte membrane electrode assembly, The water-repellent layer in the gas diffusion layer and the catalyst layer in the electrolyte membrane electrode assembly are joined via a fluorine-based surfactant. A fuel cell electrolyte membrane electrode gas diffusion layer assembly characterized by the following features.

8. If the mixed powder is a mixed powder of powder (A) and powder (B), the content of powder (B) is 17 to 40% by mass relative to the total amount of powder (A) and powder (B). If the mixed powder is a mixture of powder (A) and powder (C), the content of powder (C) is 15 to 60% by mass of the total amount of powder (A) and powder (C). The electrolyte membrane electrode gas diffusion layer assembly for fuel cell according to feature 7.

9. The fluoropolymer is at least one resin selected from the group consisting of polytetrafluoroethylene, perfluoroethylene propene copolymer, and polyvinylidene fluorite. The thermosetting resin is at least one resin selected from the group consisting of phenolic resins, silicone resins, polyurethane resins, urea resins, melamine resins, and acrylic resins. The electrolyte membrane electrode gas diffusion layer assembly for fuel cell according to feature 7.

10. When the mixed powder is a mixed powder of powder (A) and powder (B), the water-repellent layer is laminated on the surface of the porous substrate having at least the same resin as the resin constituting the fluoropolymer resin particles on its surface. If the mixed powder is a mixed powder of powder (A) and powder (C), the water-repellent layer is laminated on the surface of the porous substrate having at least one raw material of the resin constituting the thermosetting resin and / or at least one of the resin constituting the thermosetting resin on its surface. The electrolyte membrane electrode gas diffusion layer assembly for fuel cell according to feature 7.

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