JP2018152270A - Gas diffusion layer for fuel cell and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to simplify a manufacturing process, obtain high water repellency even if a load of drying and firing is reduced, and reduce manufacturing cost.SOLUTION: With respect to a base material precursor 15 in which the conductive fibres 11 are accumulated and in which a first carbon precursor resin 14A is contained, a paste-like coating liquid 24 for forming a microporous layer containing a conductive material 21 and a second carbon precursor resin 14B is applied. Then, the base material precursor is baked under a non-oxidizing atmosphere at a temperature of 1,000 to 3,500°C, is impregnated with a water repellent resin 31, and is dried and baked.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a fuel cell gas diffusion layer for diffusing a reaction fluid used in a power generation reaction of a fuel cell and a method for manufacturing the same, and in particular, a fuel that can reduce energy costs by reducing a load in a drying and firing process. The present invention relates to a gas diffusion layer for a battery and a method for producing the same.

  2. Description of the Related Art A fuel cell, in particular, a polymer electrolyte fuel cell whose use as a power source for automobiles and the like has been expanded, is configured by stacking a plurality of fuel cells via a separator, and a single cell. In general, a conductive material such as carbon and an ion exchange resin carrying a catalyst such as platinum on both sides of a polymer electrolyte membrane (ion conductive solid polymer electrolyte membrane) that selectively transmits specific ions. A cathode (+) side electrode and an anode (−) side electrode, which are constituted by an electrode catalyst layer comprising a porous gas diffusion layer (GDL) disposed outside the electrode catalyst layer, and a membrane / electrode A joined body (MEGA; Membrane-Electrode-Gas Diffusion Layer Assembly) is formed. A gas flow path for supplying fuel gas (anode gas) or oxidizing gas (cathode gas) and discharging generated gas and excess gas is formed outside the gas diffusion layer constituting the membrane / electrode assembly. And a membrane / electrode assembly is sandwiched between the separators.

  In the polymer electrolyte fuel cell having such a configuration, the gas diffusion layer constituting the electrode of the single cell battery is formed to enhance the diffusibility of the reaction gas, and is supplied from the gas flow path of the separator. Since it plays a role of diffusing gas or oxidizing gas to the catalyst layer adjacent to the gas diffusion layer (gas diffusibility), gas permeability is required, and it is a collection that efficiently moves electrons for electrochemical reaction. Electrical conductivity as an electric function is also required. In addition, the polymer electrolyte membrane and the catalyst layer are always kept in an optimum wet state, while the flooding phenomenon (a phenomenon in which the pores of the gas diffusion layer are blocked with water) is suppressed to maintain the stable power generation performance of the battery. Therefore, water repellency (drainage) is also required to discharge excess reaction product water and dew condensation water generated by the electrochemical reaction of hydrogen and oxygen during power generation.

  Such a gas diffusion layer is known to be formed by a base material (conductive porous base material) made of a conductive porous material such as carbon paper, carbon cloth, carbon felt, etc. In recent years, By coating the surface of such a substrate with a microporous layer (also called a microporous layer, a carbon layer, or a sealing layer) having pores (voids) smaller than that of the substrate, moisture management (moisture content control) is achieved. And improving the function of the gas diffusion layer and the power generation performance of the fuel cell by reducing the non-uniformity of the conductive porous substrate and improving the bondability with the catalyst layer. Yes.

  For example, in Patent Document 1, a coating liquid containing carbon black, polytetrafluoroethylene and a specific nonionic surfactant is applied to a gas diffusion layer substrate (conductive porous substrate) such as carbon paper. And the technique of forming a water-repellent carbon layer (microporous layer) on the surface of a gas diffusion layer base material by baking is disclosed.

  In Patent Document 2, a coating composition for forming a microporous layer comprising a conductive substance, a fluorine series resin and a specific thickener is coated on a gas diffusion layer (gas diffusion layer base material) such as carbon paper. It is described that a fine pore layer (microporous layer) is formed on a gas diffusion layer (gas diffusion layer base material) such as carbon paper.

  Further, in Patent Document 3, after carbon paper is immersed in a polymer solution in which a pore-forming agent such as polyvinyl alcohol is dissolved, a conductive paste (carbon) including a conductive material such as carbon black paste and a water repellent material such as PTFE. A gas diffusion layer is disclosed in which a conductive layer is coated on both sides of a substrate made of carbon paper by applying and baking a paste-like mixture).

JP 2007-194004 A JP 2006-019300 A Japanese Patent Laid-Open No. 2005-267981

  Thus, conventionally, a conductive material such as carbon particles for imparting conductivity and PTFE for imparting water repellency to a gas diffusion layer substrate composed of a conductive porous substrate such as carbon paper. A gas diffusion layer with a microporous layer is manufactured by applying a paste-like mixture for forming a microporous layer containing a water-repellent resin such as a main component.

Here, as described in Patent Document 1 and Patent Document 2, conventionally, a paste-like mixture for forming a microporous layer on a gas diffusion layer base material includes conductive materials such as carbon particles, PTFE particles, and the like. In addition to the water-repellent resin, a surfactant for uniformly dispersing the conductive material and the water-repellent resin in a dispersion medium such as water, and a thickening agent for improving coating properties and storage properties. A dispersant such as an agent is blended.
If such a surfactant or thickener is not blended, the conductive material and the water-repellent resin are agglomerated, resulting in poor dispersion and low paste stability. . In addition, clogging of piping and pumps of the coating apparatus during application, and concentration change of the paste component may occur, resulting in poor film formation and uniformity of the microporous layer, and characteristics of the gas diffusion layer. Or the output of the fuel cell will be adversely affected.

  However, in order to express the water repellency of the microporous layer by blending such a dispersant as a surfactant or a thickener, conventionally, a paste-like mixture for forming the microporous layer on the gas diffusion layer substrate is used. It was necessary to raise the temperature to a high temperature at the time of drying and baking after coating, and a great energy cost was required. For example, Patent Document 1 and Patent Document 3 have a description of applying a paste-like mixture mainly composed of carbon black and PTFE to a gas diffusion layer base material, followed by drying and baking at 300 ° C. to 390 ° C., The energy cost at the time of drying and baking is high.

  That is, in the drying and firing step performed after the paste-like mixture for forming the microporous layer is applied to the gas diffusion layer base material, a dispersant such as a surfactant or a thickener added to the paste-like mixture is added. If it is not pyrolyzed and sufficiently removed (disappeared), water is trapped by the hydrophilic group of the dispersant such as a surfactant or a thickener, so that water repellency cannot be ensured in the microporous layer. For this reason, conventionally, it is necessary to raise the temperature during drying and baking to 300 ° C. to 390 ° C. in order to sufficiently remove the dispersant such as the surfactant and the thickener in the drying and baking treatment, and the energy cost becomes high. There was a problem.

  In addition, as described in Patent Document 1 and Patent Document 2, the production of a conventional gas diffusion layer with a microporous layer can be performed independently by using a gas such as independently formed carbon paper that can form the gas diffusion layer. This is a design in which a paste-like mixture for forming a microporous layer is applied to a diffusion layer substrate. That is, it is a manufacturing method in which a paste-like mixture for forming a microporous layer is applied to a gas diffusion layer substrate that has been made porous by high-temperature heat treatment. Thus, in the design in which the paste mixture for forming the microporous layer is applied to the porous gas diffusion layer substrate obtained by the high-temperature heat treatment, the microporous layer forming material is applied to the porous gas diffusion layer substrate. If the components of the paste-like mixture are soaked, the pores (spaces) of the gas diffusion layer substrate may be clogged, and the moisture and gas permeability may be reduced. Therefore, the paste-like mixture for forming the microporous layer Before applying the coating, it is necessary to apply a water-repellent treatment to the porous gas diffusion layer substrate and dry it, or use a thickener to increase the viscosity of the paste-like mixture for forming the microporous layer. It was necessary to devise. For this reason, the total number of work steps for producing the gas diffusion layer is complicated and the load during drying and baking is increased due to the incorporation of a large amount of thickener, making the production process complicated and taking production time. Manufacturing cost has increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a gas diffusion layer capable of simplifying the production process, obtaining high water repellency even when the drying and firing load is reduced, and reducing the production cost, and a production method thereof. Is.

  In the method for producing a gas diffusion layer for a fuel cell according to the first aspect of the present invention, in the base material precursor forming step, the conductive fibers are integrated and the gas diffusion containing the first carbon precursor resin. Forming a precursor of the layer base material, and subsequently, in the gas diffusion layer precursor forming step, the conductive material for forming the microporous layer with respect to the base material precursor formed in the base material precursor forming step. The gas diffusion layer precursor formed in the gas diffusion layer precursor formation step by applying a coating solution containing a functional material to form a precursor of the gas diffusion layer, followed by a carbonization / graphitization step Is calcined and graphitized in a non-oxidizing atmosphere at a temperature of 1000 to 3500 ° C. to carbonize and graphitize the first carbon precursor resin. The gas diffusion layer precursor is impregnated with a water-repellent resin and dried and fired At extent, the water-repellent resin is one which drying and firing the gas diffusion layer precursor impregnated.

  The base material precursor forming step is a step of forming a gas diffusion layer base material precursor in which the first carbon precursor resin is attached to the accumulated conductive fibers, and the conductive fiber and the first carbon precursor. The gas diffusion layer base material precursor may be formed by accumulating the body resin together by papermaking or the like, or the gas diffusion layer base material is impregnated by impregnating the accumulated conductive fibers with the first carbon precursor resin. May be formed. The accumulation of the conductive fibers may be by papermaking, by woven fabric, or by needle punching (felting). In addition, a binder may be added when forming the gas diffusion layer base material precursor. This binder has a function of binding conductive fibers, and preferably disappears (burned out) by heating and baking in the subsequent carbonization / graphitization step, and the disappeared trace is a gas or moisture flow path of the gas diffusion layer base material. For example, polyvinyl alcohol, polylactic acid, pulp or the like is used.

  As the conductive fiber forming the gas diffusion layer base material precursor, for example, carbon fiber such as carbon black or graphite is used, and as the first carbon precursor resin, the subsequent carbonization / graphitization is performed. As a resin carbide that is carbonized and graphitized by heating and baking in a non-oxidizing atmosphere in the process and has a function of binding conductive fibers, for example, a phenol resin having a high residual carbon ratio used.

The gas diffusion layer precursor forming step is performed by applying a paste-like coating liquid containing a conductive material for forming a microporous layer on one side or both sides in the thickness direction of the base material precursor. In this step, a microporous layer precursor is formed on one or both sides in the thickness direction of the base material precursor to obtain a gas diffusion layer precursor composed of the base material precursor and the microporous layer precursor.
As the conductive material contained in the coating solution, carbon particles such as carbon black and graphite are used.

In the carbonization / graphitization step, the gas diffusion layer precursor is heated and fired at a temperature of 1000 to 3500 ° C. in a non-acidic atmosphere, whereby the first base in the base material precursor in the gas diffusion layer precursor. This is a step of carbonizing and graphitizing the carbon precursor resin.
In the carbonization / graphitization, the temperature condition of heating and firing is set according to the purpose of the gas diffusion layer, desired characteristics, resin characteristics, etc., and it does not matter whether carbonization or graphitization is distinguished.
In addition, the non-oxidizing atmosphere means an atmosphere that is not widely oxidizable, and usually in an inert gas such as nitrogen (N ₂ ) gas, argon (Ar) gas, helium (He) gas, or the like. However, carbon powder such as activated carbon in a reducing atmosphere such as carbon monoxide (CO) gas, hydrogen (H ₂ ) gas, in a vacuum, in an atmosphere such as carbon dioxide gas, or in a sealed space. Including the method of filling in.

  The water-repellent resin impregnation step is a step of impregnating the gas diffusion layer precursor after the heating and baking with a water-repellent resin and attaching the water-repellent resin to the gas diffusion layer precursor. The impregnation of the water-repellent resin is usually performed by supplying the gas diffusion layer precursor after the heating and baking in the form of a resin dispersion (resin solution) or a resin film. A water repellent resin is added to the gas diffusion layer precursor. As the water repellent resin, a fluorine resin such as polytetrafluoroethylene (PTFE) is used.

The drying and baking step is a step of drying and baking the gas diffusion layer precursor impregnated with the water-repellent resin. By this drying and baking, moisture (including a dispersion medium) in the gas diffusion layer precursor or Remove components that inhibit water repellency (such as dispersants).
The form of the gas diffusion layer substrate may be a paper shape, a cloth shape, a felt shape, a mat shape, or the like.

In the base material precursor forming step in the method for producing a gas diffusion layer for a fuel cell of the invention of claim 2, a paper base material is formed by papermaking the conductive fibers in a papermaking step, and a carbon precursor resin impregnation step The base material precursor is formed by impregnating the first carbon precursor resin into the papermaking base material.
The papermaking step is a step of forming a papermaking substrate such as a sheet (paper shape) by papermaking conductive fibers.
In the carbon precursor resin impregnation step, the first carbon precursor resin that is carbonized and graphitized by heating and baking in a non-oxidizing atmosphere in the subsequent carbonization and graphitization step is applied to the papermaking substrate. It is the process of making it adhere. The impregnation of the first carbon precursor resin is usually performed by supplying the paper base material in the form of a resin dispersion (resin solution) or a resin film. The carbon precursor resin is added.

4. The method for producing a gas diffusion layer for a fuel cell according to claim 3, wherein the coating liquid applied to the substrate precursor in the gas diffusion layer precursor forming step is carbonized by heating and baking in the carbonization / graphitization step. -It contains the 2nd carbon precursor resin which is graphitized and becomes resin carbide.
As the second carbon precursor resin, carbonized and graphitized by heating and baking at 1000 to 3500 ° C. in a non-acidic atmosphere in the carbonization / graphitization step to become a resin carbide, and the conductive carbon As what has a function to bind, a phenol resin etc. with a high residual carbon rate are used, for example.

  The method for producing a gas diffusion layer for a fuel cell according to a fourth aspect of the present invention includes forming a papermaking substrate in which conductive fibers are integrated in a papermaking process, and subsequently, in a gas diffusion layer precursor forming process, A mixed liquid containing a carbon precursor resin and a conductive material for forming a microporous layer is added to the papermaking substrate to form a precursor of the gas diffusion layer, followed by a carbonization / graphitization step. Then, the gas diffusion layer precursor formed in the gas diffusion layer precursor formation step is heated and fired at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere to carbonize and graphitize the carbon precursor resin. Further, in the water repellent resin impregnation step, the gas diffusion layer precursor after carbonization / graphitization is impregnated with a water repellent resin, and in the drying and firing step, the gas impregnated with the water repellent resin. The diffusion layer precursor is dried and fired.

  The papermaking step is a step of forming a papermaking substrate such as a sheet (paper shape) by papermaking conductive fibers. As the conductive fiber forming the papermaking substrate, for example, carbon fiber such as carbon black or graphite is used. When forming the papermaking substrate, a binder may be added. This binder has a function of binding conductive fibers, and preferably disappears (burned out) by heating and baking in the subsequent carbonization / graphitization step, and the disappeared trace is a gas or moisture flow path of the gas diffusion layer base material. For example, polyvinyl alcohol, polylactic acid, pulp or the like is used.

In the gas diffusion layer precursor forming step, a paste-like mixed liquid containing a carbon precursor resin and a conductive material for forming a microporous layer is added to the papermaking base material, thereby adding to the papermaking base material. A base precursor is formed by impregnating a carbon precursor resin, and a microporous layer precursor composed of a carbon precursor resin and a conductive material is formed on one or both sides of the papermaking base. This is a step of obtaining a gas diffusion layer precursor comprising a body and a microporous layer precursor.
Here, the addition is performed by applying a paste-like mixed liquid containing a carbon precursor resin and a conductive material for forming a microporous layer on one side or both sides in the thickness direction of the papermaking substrate. Alternatively, the papermaking substrate is immersed in a paste-like mixed liquid containing a carbon precursor resin and a conductive material for forming a microporous layer.
As the conductive material contained in the liquid mixture, carbon particles such as carbon black and graphite are used, and as the carbon precursor resin, by heating and firing in a non-oxidizing atmosphere in the subsequent carbonization / graphitization step. For example, a phenol resin having a high residual carbon ratio is used as a resin carbide that is carbonized and graphitized and has a function of binding conductive fibers.

The carbonization / graphitization step carbonizes and graphitizes the carbon precursor resin in the gas diffusion layer precursor by heating and baking the gas diffusion layer precursor at a temperature of 1000 to 3500 ° C. in a non-acidic atmosphere. It is a process.
In the carbonization / graphitization, the temperature condition of heating and firing is set according to the purpose of the gas diffusion layer, desired characteristics, resin characteristics, etc., and it does not matter whether carbonization or graphitization is distinguished.
In addition, the non-oxidizing atmosphere means an atmosphere that is not widely oxidizable, and usually in an inert gas such as nitrogen (N ₂ ) gas, argon (Ar) gas, helium (He) gas, or the like. However, carbon powder such as activated carbon in a reducing atmosphere such as carbon monoxide (CO) gas, hydrogen (H ₂ ) gas, in a vacuum, in an atmosphere such as carbon dioxide gas, or in a sealed space. Including the method of filling in.

  The water-repellent resin impregnation step is a step of impregnating the gas diffusion layer precursor after the heating and baking with a water-repellent resin and attaching the water-repellent resin to the gas diffusion layer precursor. The impregnation of the water-repellent resin is usually performed by supplying the gas diffusion layer precursor after the heating and baking in the form of a resin dispersion (resin solution) or a resin film. A water repellent resin is added to the gas diffusion layer precursor. Examples of the water repellent resin include fluorine resins such as polytetrafluoroethylene (PTFE).

The drying and baking step is a step of drying and baking the gas diffusion layer precursor impregnated with the water-repellent resin. By this drying and baking, moisture (including a dispersion medium) in the gas diffusion layer precursor or Remove components that inhibit water repellency (such as dispersants).
The form of the gas diffusion layer substrate may be a paper shape, a cloth shape, a felt shape, a mat shape, or the like.

According to a fifth aspect of the present invention, there is provided a method for producing a gas diffusion layer for a fuel cell, wherein the accumulation of the conductive fibers is performed by paper making together with a binder that binds the conductive fibers.
Here, the binder has a function of binding conductive fibers, and is preferably lost (burned out) by heating in the carbonization / graphitization step, and the disappearance trace is a gas or moisture flow path of the gas diffusion layer base material. For example, polyvinyl alcohol, polylactic acid, pulp or the like is used.

  In the method for producing a gas diffusion layer for a fuel cell according to a sixth aspect of the invention, the temperature at which the gas diffusion layer precursor is dried and fired in the drying and firing step is in the range of 200 to 250 ° C.

8. The method for producing a gas diffusion layer for a fuel cell according to claim 7, wherein the conductive material for forming the microporous layer is carbon black having a particle size in a range of a median diameter of 30 nm or more and 100 nm or less. It is.
Here, “medium diameter” means the number larger than a certain particle diameter in the particle size distribution of the powder according to the definition of the term in the text and explanation of JIS Z 8901 “Test Powder and Test Particles”. The particle diameter (diameter) when (or mass) occupies 50% of that of the whole powder, that is, the particle size of 50% oversize, usually referred to as the median diameter or 50% particle diameter and D ₅₀ Represented. By definition, the size of the particle group is expressed by the average particle diameter and the median diameter, but here, it is a value measured by the display of the product description and the laser diffraction / scattering method. The “median diameter measured by the laser diffraction / scattering method” is a particle whose cumulative weight part is 50% in the particle size distribution obtained by the laser diffraction / scattering method using a laser diffraction particle size distribution measuring apparatus. This refers to the diameter (D ₅₀ ). In addition, the above numerical values are not strict, and there is an error for each product. If an error due to measurement or the like is included, mixing of an error of about 10% or less is not denied. From the point of view of this error, it shows a normal distribution, and the particle size shows a normal distribution, so even if it is considered that the median diameter ≈ the average particle diameter, the difference between the two is within a few percent, It is a level considered as an error.

  9. The method for producing a gas diffusion layer for a fuel cell according to claim 8, wherein the conductive material for forming the microporous layer is graphite having a particle size in a range of a median diameter of 3 μm or more and 20 μm or less. is there.

  The gas diffusion layer for a fuel cell of the invention of claim 9 is formed of a microporous layer with respect to the gas diffusion layer base material precursor in which conductive fibers are integrated and the first carbon precursor resin is contained. Conductivity for forming a microporous layer on a papermaking substrate on which a conductive fiber and a second carbon precursor resin are applied or a conductive paper is accumulated By adding a paste-like mixed liquid containing the material and the carbon precursor resin, and performing carbonization / graphitization by heating and baking at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere, a gas diffusion layer base In the microporous layer disposed on one side or both sides of the material, the conductive material is bound by the resin carbide that is the carbide of the carbon precursor resin.

  Here, the resin carbide is obtained by carbonizing and graphitizing carbon precursor resin such as phenol resin by heating and baking at 1000 to 3500 ° C. in a non-oxidizing atmosphere (carbon precursor resin such as phenol resin). Is formed by carbonization and graphitization), and is a substance that binds a conductive material. As the carbon precursor resin, a phenol resin or the like is preferable because it has a strong binding force with a conductive material such as carbon particles and has a large residual weight during carbonization.

  According to the method for manufacturing a gas diffusion layer for a fuel cell according to the first aspect of the invention, first, a gas diffusion layer base material precursor in which conductive fibers are integrated and the first carbon precursor resin is contained. After applying a paste-like coating liquid containing a conductive material for forming a microporous layer to the body to form a gas diffusion layer precursor, in the carbonization / graphitization step, the gas diffusion layer precursor is Baking is performed at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere.

  Here, in the gas diffusion layer base material precursor before carbonization / graphitization, since the first carbon precursor resin is attached to an aggregate of conductive fibers such as carbon fibers, carbonization / graphite Since there are few voids because it is before conversion, when a paste-like coating liquid containing a conductive material for forming a microporous layer is applied to such a substrate precursor, the surface of the substrate precursor is made of a conductive material. A porous layer precursor is formed.

  Then, a paste-like coating liquid containing a conductive material for forming a microporous layer is applied to the base material precursor before carbonization / graphitization in this way, and formed on the base material precursor together with the base material precursor. When the prepared microporous layer precursor is heated and fired at 1000 to 3500 ° C. in a non-oxidizing atmosphere, the first carbon precursor resin in the substrate precursor is carbonized and graphitized to form a resin carbide. The conductive fiber is bound by the resin carbide.

In addition, when 2nd carbon precursor resin is mix | blended with the said paste-form coating liquid, the microporous layer precursor formed on the base-material precursor is 1000-3500 degreeC temperature in non-oxidizing atmosphere. The second carbon precursor resin in the microporous layer precursor is also carbonized and graphitized to form a resin carbide, and the conductive material is also bound by the resin carbide. .
In addition, when a binder such as polyvinyl alcohol or pulp that captures conductive fibers is contained in the base material precursor, by heating and baking under a high temperature condition for carbonizing and graphitizing the first carbon precursor resin. The binder is thermally decomposed and disappears. The disappearance trace becomes pores (pores, pores) that serve as gas and water passages in the gas diffusion layer.
Furthermore, even when a dispersing agent such as a surfactant for dispersing the conductive material is contained in the paste-like coating liquid, heating under high temperature conditions for carbonizing and graphitizing the first carbon precursor resin is performed. By calcination, the dispersant is thermally decomposed and removed.

  Subsequently, the gas diffusion layer precursor heated and fired in the carbonization / graphitization step is impregnated with the water-repellent resin in the water-repellent resin impregnation step, and then dried and fired in the drying and firing step. Thereby, the gas diffusion layer which consists of a gas diffusion layer base material and the microporous layer arrange | positioned on the one or both surfaces of the thickness direction is obtained.

  The gas diffusion layer precursor heated and fired in the carbonization / graphitization process has a microporous layer precursor made of a conductive material formed on the surface of the base material precursor, so it is processed at a high temperature as in the past. It is not necessary to apply a paste-like mixture for forming a microporous layer comprising a conductive material, a water repellent resin, and a dispersant after the water repellent treatment is performed on the porous gas diffusion layer substrate. Therefore, the amount of the dispersant present in the gas diffusion layer precursor to be dried and fired is small. For this reason, in drying and baking after impregnating the water-repellent resin, the dispersant that inhibits the water repellency is completely removed even under a low temperature condition of 200 to 250 ° C., and the resulting gas diffusion layer exhibits high water repellency. To do.

  Thus, according to the method for producing a gas diffusion layer for a fuel cell according to the first aspect of the present invention, a paste-like coating liquid containing a conductive material for forming a microporous layer in a substrate precursor before carbonization / graphitization Is applied to form a microporous layer precursor made of a conductive material on the surface of the substrate precursor. Then, the microporous layer precursor is fired at a high temperature together with the substrate precursor, and then the entire substrate precursor and the microporous layer precursor are subjected to water repellent treatment, followed by drying and firing. Next, a porous gas diffusion layer base material fired at high temperature is subjected to a water repellent treatment, and then a microporous layer forming paste mixture containing a conductive material, a water repellent resin and a dispersant is applied. Since the drying and firing is not performed, the gas diffusion layer precursor to be dried and fired has few dispersants that inhibit water repellency. In particular, in the drying and firing process, it is not necessary to remove a dispersant such as a nonionic surfactant for dispersing the conductive material contained in the conventional paste mixture for forming a microporous layer. High water repellency can be ensured without the dispersant remaining by drying and baking at a temperature lower than the temperature condition necessary for removing the dispersant in the paste mixture for forming the microporous layer. In addition, the time required for the drying and firing treatment can be shortened.

  Conventionally, when a microporous layer forming paste containing a conductive material, a water-repellent resin and a dispersant is applied to a porous gas diffusion layer base material after high-temperature firing, a gas having a large pore porosity. In order to prevent the components of the microporous layer forming paste from penetrating into the diffusion layer substrate (infiltration), and to fix the paste component to the surface of the gas diffusion layer substrate, the water diffusion resin is applied to the gas diffusion layer substrate. In the method for producing a gas diffusion layer for a fuel cell according to the present invention, carbonized / graphite was prepared by applying a microporous layer-forming paste-like mixture and drying and firing. A paste-like coating liquid containing a conductive material for forming a microporous layer is applied to a base precursor before conversion, and the base precursor has a small gap, and the first carbon precursor resin But Therefore, the microporous material can be applied to the surface of the substrate precursor simply by applying the coating solution to the substrate precursor without performing water-repellent treatment or moisture drying before applying the paste-like coating solution. The conductive material for layer formation can be fixed. Therefore, manufacturing workability and a manufacturing process can be simplified.

  In this way, the temperature for drying and firing can be reduced, the time required for drying and firing can be shortened, and the workability of the production and the production process can be simplified, so that the production cost and the environmental load can be reduced. Is possible.

  Furthermore, in the carbonization / graphitization step, the microporous layer precursor is calcined at a high temperature together with the substrate precursor, and the first carbon precursor resin in the substrate precursor is carbonized, whereby the first carbon precursor is obtained. The resin carbide formed by carbonizing the resin binds the conductive fiber of the substrate precursor and the conductive material of the microporous layer precursor at the boundary between the substrate precursor and the microporous layer precursor. Even if the amount of the binder component due to the water-repellent resin is reduced by reducing the firing load, the bonding properties of the gas diffusion layer substrate and the microporous layer are strong and the microporous layer is difficult to peel off from the gas diffusion layer substrate. The joint strength of the porous layer and the gas diffusion layer base material is high.

  In this way, the manufacturing process can be simplified, a high water repellency can be obtained even if the drying and firing load is reduced, and the manufacturing method of the gas diffusion layer can be reduced in manufacturing cost and environmental load.

  According to the method for producing a gas diffusion layer for a fuel cell according to the invention of claim 2, the base material precursor forming step includes a paper making step of forming the paper making base material by paper making the conductive fiber, and the paper making base. Since it comprises a carbon precursor resin impregnation step of impregnating the material with the first carbon precursor resin, in addition to the effect of claim 1, the first carbon is added to the paper body of the conductive fiber. It is easy to deposit the precursor resin in a desired distribution.

  According to the method for producing a gas diffusion layer for a fuel cell according to the invention of claim 3, the coating liquid applied to the base material precursor in the gas diffusion layer precursor forming step is heated and fired in the carbonization / graphitization step. In the obtained microporous layer, the conductive material is bound by the resin carbide obtained by carbonizing the second carbon precursor resin. To form a conductive path. Therefore, in addition to the effect of the first or second aspect, the conductivity and the layer strength of the microporous layer can be improved. Furthermore, a conductive path is formed by binding a conductive material to a conductive fiber of the gas diffusion layer base material by a resin carbide obtained by carbonizing the second carbon precursor resin, thereby gas diffusion. The contact resistance between the layer substrate and the microporous layer is also small, the conductivity of the entire gas diffusion layer can be increased, and the fixing power of the microporous layer to the gas diffusion layer substrate is improved.

  According to the method for manufacturing a gas diffusion layer for a fuel cell according to the invention of claim 4, first, the carbon precursor resin and the conductivity for forming the microporous layer are formed on the papermaking substrate on which the conductive fibers are integrated. After adding the paste-like mixed liquid containing the material to form the gas diffusion layer precursor, in the carbonization / graphitization step, the gas diffusion layer precursor is heated to 1000 to 3500 ° C. in a non-oxidizing atmosphere. Bake with heat.

  Here, in the papermaking substrate before carbonization / graphitization, since there are few voids because it is before carbonization / graphitization, a carbon precursor resin and a conductive material for forming a microporous layer are added to the substrate precursor. When the paste-form mixed liquid is added, the paper precursor is impregnated with the carbon precursor resin to form a base precursor, and the surface of the base precursor is made of a conductive material and a carbon precursor resin. A microporous layer precursor is formed.

  When the microporous layer precursor formed on the base material precursor is heated and fired at 1000 to 3500 ° C. in a non-oxidizing atmosphere together with such a base material precursor, the carbon precursor resin is carbonized. -Graphite is formed to form a resin carbide, and the conductive fiber and the conductive material are bound by the resin carbide.

In the case where a binder such as polyvinyl alcohol or pulp that captures conductive fibers is contained in the base material precursor, the binder is obtained by heating and baking under high temperature conditions for carbonizing and graphitizing such a carbon precursor resin. Dissipates by thermal decomposition. The disappearance trace becomes pores (pores, pores) that serve as gas and water passages in the gas diffusion layer.
Furthermore, even when a dispersing agent such as a surfactant for dispersing the conductive material is contained in the paste-like mixed liquid, by heating and baking under a high temperature condition for carbonizing and graphitizing such a carbon precursor resin, The dispersant is removed by thermal decomposition.

  Subsequently, the gas diffusion layer precursor heated and fired in the carbonization / graphitization step is impregnated with the water-repellent resin in the water-repellent resin impregnation step, and then dried and fired in the drying and firing step. Thereby, the gas diffusion layer which consists of a gas diffusion layer base material and the microporous layer arrange | positioned on the one or both surfaces of the thickness direction is obtained.

  The gas diffusion layer precursor heated and fired in the carbonization / graphitization process has a microporous layer precursor made of a conductive material formed on the surface of the base material precursor, so it is processed at a high temperature as in the past. It is not necessary to apply a paste-like mixture for forming a microporous layer comprising a conductive material, a water repellent resin, and a dispersant after the water repellent treatment is performed on the porous gas diffusion layer substrate. Therefore, the amount of the dispersant present in the gas diffusion layer precursor to be dried and fired is small. For this reason, in drying and baking after impregnating the water-repellent resin, the dispersant that inhibits the water repellency is completely removed even under a low temperature condition of 200 to 250 ° C., and the resulting gas diffusion layer exhibits high water repellency. To do.

  Thus, according to the method for producing a gas diffusion layer for a fuel cell of the invention of claim 4, the papermaking base material before carbonization / graphitization contains the conductive material for forming the microporous layer and the carbon precursor resin. A paste mixture is added to impregnate a paper precursor with a carbon precursor resin to form a substrate precursor, and a microporous layer precursor made of a conductive material and a carbon precursor resin is formed on the surface. To do. And, the microporous layer precursor is fired at a high temperature together with such a base material precursor, and then subjected to water repellent treatment on the whole base material precursor and the microporous layer precursor, and then dried and fired. A porous mixture for forming a microporous layer in which a porous gas diffusion layer base material fired at a high temperature is treated with water repellency, and then a conductive material, a water-repellent resin and a dispersant are blended. The gas diffusion layer precursor to be dried and baked has few dispersants that inhibit water repellency. In the drying and firing process, it is not necessary to remove a dispersant such as a nonionic surfactant for dispersing the conductive material contained in the conventional paste-form mixture for forming the microporous layer. High water repellency can be ensured without the dispersant remaining by drying and baking at a temperature lower than the temperature condition necessary for removing the dispersant in the layer-forming paste-like mixture. In addition, the time required for the drying and firing treatment can be shortened.

  In particular, since the microporous layer precursor made of the conductive material and the carbon precursor resin is formed at the same time that the paper precursor is impregnated with the carbon precursor resin, the number of manufacturing steps is reduced. Conventionally, when a microporous layer forming paste containing a conductive material, a water-repellent resin, and a dispersant is applied to a porous gas diffusion layer substrate after high-temperature firing, a gas having a large pore porosity In order to prevent the components of the microporous layer forming paste from penetrating into the diffusion layer substrate (infiltration), and to fix the paste component to the surface of the gas diffusion layer substrate, the water diffusion resin is applied to the gas diffusion layer substrate. In the method for producing a gas diffusion layer for a fuel cell according to the present invention, carbonized / graphite was prepared by applying a microporous layer-forming paste-like mixture and drying and firing. A paste-like mixed solution containing a conductive material for forming a microporous layer and a carbon precursor resin is added to the papermaking base before forming, and the papermaking base has a small gap, and the papermaking base Since the raw precursor resin is infiltrated, the surface of the substrate precursor can be simply added to the papermaking substrate without performing water repellency treatment or moisture drying before adding the paste mixture. In addition, a conductive material for forming a microporous layer can be fixed. Therefore, manufacturing workability and a manufacturing process can be simplified.

  In this way, the temperature for drying and firing can be reduced, the time required for drying and firing can be shortened, and the workability of the production and the production process can be simplified, so that the production cost and the environmental load can be reduced. Is possible.

  Further, in the carbonization / graphitization step, the microporous layer precursor is calcined at a high temperature together with the base material precursor, and the carbon precursor resin is carbonized, whereby the carbon precursor resin is carbonized, thereby forming a gas diffusion layer. And the microporous layer, the conductive material is bound by the resin carbide obtained by carbonizing the carbon precursor resin, thereby forming a conductive path. Therefore, conductivity and layer strength can be improved. Furthermore, since the conductive fiber of the substrate precursor and the conductive material of the microporous layer precursor are bound at the boundary between the substrate precursor and the microporous layer precursor, the water repellency is reduced by reducing the load of drying and firing. Even if the amount of the binder component due to the resin decreases, the bonding properties of the gas diffusion layer substrate and the microporous layer are strong, and the microporous layer is difficult to peel from the gas diffusion layer substrate. The integral joint strength of is high. Conductivity and layer strength can be improved.

  In this way, the manufacturing process can be simplified, a high water repellency can be obtained even if the drying and firing load is reduced, and the manufacturing method of the gas diffusion layer can be reduced in manufacturing cost and environmental load.

  According to the method for producing a gas diffusion layer for a fuel cell according to the invention of claim 5, since the conductive fiber and the binder that binds the conductive fiber are made together, any one of claims 1 to 4 is made. In addition to the effects described above, it is possible to increase the capture of conductive fibers and the paper yield during paper making to facilitate paper making, and to increase the dispersibility of conductive fibers to prevent re-convergence. In addition, the entanglement and reinforcing properties of the conductive fibers can be improved. Furthermore, the conductive fibers after papermaking can be prevented from falling off and peeling off to enhance shape retention and handleability. In particular, the binder disappears by heating in the carbonization / graphitization step (burnt), and the disappeared traces form pores (pores, pores) that serve as gas and moisture channels of the gas diffusion layer base material. If it exists, the permeability | transmittance of a water | moisture content or gas can be improved, and control of the air permeability of a gas diffusion layer base material becomes easy by the addition amount etc. of a binder.

  According to the method for producing a gas diffusion layer for a fuel cell according to the invention of claim 6, the temperature at which the gas diffusion layer precursor is dried and fired in the drying and firing step is in the range of 200 to 280 ° C. In addition to the effect described in any one of Items 1 to 5, the electric power required for drying and baking is low, the manufacturing cost is suppressed, and the amount of carbon dioxide emission in the drying and baking process is small and the environmental load is more. It is reduced.

According to the method for producing a gas diffusion layer for a fuel cell of the invention of claim 7, the conductive material for forming the microporous layer is a carbon black having a median diameter in the range of 30 nm or more and 100 nm or less. It is.
As a result of accumulating earnest experimental research, the present inventors have used carbon black as the conductive material for forming the microporous layer, and if the particle diameter is in the range of the median diameter of 30 to 100 nm, Even without a dispersant, the gas diffusion layer has good dispersibility and storability, good coating efficiency, few irregularities on the surface of the microporous layer, excellent smoothness, and high gas and moisture permeability. Based on this finding, the present invention has been completed.
Therefore, if the particle size of carbon black as the conductive material for forming the microporous layer is within the range of the median diameter of 30 to 100 nm, the effect according to any one of claims 1 to 6 is achieved. In addition, the output of the fuel cell can be stably improved.

According to the method for producing a gas diffusion layer for a fuel cell of an eighth aspect of the present invention, the conductive material for forming the microporous layer has a graphite particle diameter within a range of a median diameter of 3 μm to 20 μm. Graphite).
As a result of accumulating earnest experimental research, the present inventors have found that when graphite is used as the conductive material for forming the microporous layer, if the particle diameter is within the range of the median diameter of 3 to 20 μm, the dispersion A gas diffusion layer with good dispersibility, good coating efficiency, few irregularities on the surface of the microporous layer, excellent smoothness, and high gas and moisture permeability and conductivity without the use of an agent. And the present invention has been completed based on this finding.
Therefore, if the particle diameter of graphite as the conductive material for forming the microporous layer is in the range of the median diameter of 3 to 20 μm, the effect according to any one of claims 1 to 6 is achieved. In addition, the output of the fuel cell can be stably improved.

  According to the gas diffusion layer for a fuel cell according to the ninth aspect of the present invention, the microporous layer disposed on one or both sides in the thickness direction of the gas diffusion layer base material is 1000 to 3500 ° C. in a non-oxidizing atmosphere. The conductive material is bound by the resin carbide formed by carbonizing the carbon precursor resin at the temperature.

  As a result of the inventors' diligent experimental research, the conductive fiber is accumulated by papermaking or the like, and the conductive material and the gas diffusion layer substrate precursor containing the first carbon precursor resin A conductive material and a carbon precursor are applied to a papermaking substrate obtained by applying a paste-like mixture for forming a microporous layer containing the second carbon precursor resin, or by collecting conductive fibers by papermaking or the like. After adding the resinous microporous layer-forming paste-like mixture, it is heated and fired at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere to carbonize and graphitize the carbon precursor resin. It has been found that a gas diffusion layer for a fuel cell produced by impregnating a resin and then performing drying and baking exhibits high water repellency even if the temperature condition during drying and baking is low.

  This is present in the gas diffusion layer precursor that is dried and fired after the water repellent treatment in the design in which the paste for forming the microporous layer containing the conductive material and the carbon precursor resin is applied before carbonization / graphitization. Thus, there are few dispersants that inhibit water repellency, and in particular, the dispersants such as nonionic surfactants for dispersing the conductive material contained in the conventional paste mixture for forming the microporous layer are removed. This is because it is not necessary, and the dispersing agent inhibiting water repellency is sufficiently removed in the gas diffusion layer and does not remain even in the drying and baking at a temperature lower than the conventional temperature condition. Further, since there are few dispersants present in the gas diffusion layer precursor to be dried and fired to inhibit water repellency, the time required for the drying and firing treatment can be shortened.

  In the case where a gas diffusion layer precursor is formed by applying a paste containing a conductive material and a carbon precursor resin before carbonization / graphitization, the microporous layer precursor is non-oxidizing together with the base material precursor. By being heated and fired at a temperature of 1000 to 3500 ° C. in an atmosphere, the carbon precursor resin in the microporous layer precursor is carbonized to become a resin carbide and binds the conductive material.

  That is, the microporous material containing the conductive material and the second carbon precursor resin is formed with respect to the gas diffusion layer base material precursor in which the conductive fibers are integrated and the first carbon precursor resin is contained. A microporous layer-forming paste mixture containing a conductive material and a carbon precursor resin after applying the layer-forming paste-like mixture or to a papermaking substrate in which conductive fibers are accumulated by papermaking or the like Gas diffusion layer for a fuel cell produced by heating and baking at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere, and further impregnating with a water-repellent resin, followed by drying and baking. The microporous layer is formed by binding a conductive material with a resin carbide formed by carbonizing a carbon precursor resin at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere.

  Thus, the manufacturing process can be simplified, and even if the drying and firing load is reduced, high water repellency can be obtained, resulting in a gas diffusion layer that can reduce manufacturing costs and environmental burdens.

FIG. 1 is a schematic diagram showing a schematic configuration of a polymer electrolyte fuel cell to which a fuel cell gas diffusion layer according to Embodiment 1 of the present invention is applied. FIG. 2 is a flowchart showing a method of manufacturing a fuel cell gas diffusion layer according to Embodiment 1 of the present invention. FIG. 3 is a flowchart showing a method of manufacturing a fuel cell gas diffusion layer according to Embodiment 2 of the present invention. FIG. 4 is a flowchart showing a conventional method for producing a fuel cell gas diffusion layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In each embodiment, the same symbol and the same reference sign mean the same or corresponding functional part, and the same sign and the same reference sign in the respective embodiments are the functional parts common to those embodiments. Therefore, the detailed description which overlaps is abbreviate | omitted here.

  First, the structure of a polymer electrolyte fuel cell (single cell) in which a fuel cell gas diffusion layer according to Embodiments 1 and 2 of the present invention is incorporated will be described with reference to the schematic configuration diagram of FIG. In the figure, the anode side is A and the cathode side is K.

As illustrated, the fuel cell gas diffusion layer 100 (cathode side gas diffusion layer 100K, anode side gas diffusion layer 100A) is joined to the catalyst layer 110 (cathode side catalyst layer 110K, anode side catalyst layer 110A), The electrode 130 (cathode electrode 130K, anode electrode 130A) is integrally formed, and is disposed together with the catalyst layer 110 on both surfaces of the polymer electrolyte membrane 120 (single cell core) that selectively transmits specific ions. A membrane / electrode assembly (MEGA) 150 is formed.
The membrane / electrode assembly 150 includes a cathode-side separator 140K provided with an oxidizing gas channel 141K that supplies an oxidizing gas as an oxidizing agent outside the cathode-side gas diffusion layer 100K, and an anode-side gas diffusion layer 100A. The fuel cell 200 is sandwiched between anode-side separators 140A provided with fuel gas passages 141A for supplying fuel gas, thereby forming a single cell of the fuel cell 200.

  That is, the single cell of the fuel cell 200 to which the fuel cell gas diffusion layer 100 according to the first and second embodiments is applied is a cathode-side catalyst in which an oxidizing gas such as oxygen gas reacts on one surface of the electrolyte membrane 120. The cathode electrode 130K constituted by the layer 110K and the cathode side gas diffusion layer 100K is disposed, and the other surface is constituted by the anode side catalyst layer 110A and the anode side gas diffusion layer 100A on which the fuel gas such as hydrogen gas reacts. Membrane / electrode assembly 150 that constitutes a power generation unit by disposing anode electrode 130A, cathode separator 140K disposed on the surface of cathode electrode 130K of membrane / electrode assembly 150, and anode of membrane / electrode assembly 150 The anode separator 140A is disposed on the surface of the electrode 130A.

Here, the electrolyte membrane 120 made of a polymer membrane serving as an ion exchange group has a property of binding firmly to specific ions and selectively transmitting cations or anions.
Further, the catalyst layer 110 (cathode side catalyst layer 110K, anode side catalyst layer 110A) is composed of catalyst-supported carbon and ion-exchange resin in which a noble metal catalyst such as platinum, gold, and palladium is supported by carbon, and an oxidizing gas or a fuel gas reacts. To do.

  The fuel cell gas diffusion layer 100 (cathode side gas diffusion layer 100K, anode side gas diffusion layer 100A) according to the first and second embodiments is the same as the gas diffusion layer base material 10 (cathode side base material 10K, anode side). 10A) and a microporous layer (microporous layer) 20 (cathode side microporous layer 20K, anode side microporous layer 20A), the microporous layer 20 side being disposed on the catalyst layer 110 side, and gas It is incorporated so that the diffusion layer substrate 10 side is disposed on the separator 140 side.

With such a configuration, when an oxidizing gas is supplied from the outside to the oxidizing gas channel 141K of the cathode separator 140K, a part of the oxidizing gas flowing along the oxidizing gas channel 141K is part of the cathode gas diffusion layer 100K. The gas diffusion layer base material 10K enters the inside from the surface. Other unreacted oxidizing gas flows along the oxidizing gas channel 141K and is discharged to the outside of the fuel cell 200.
Similarly, when fuel gas is supplied from the outside to the fuel gas channel 141A of the anode separator 140A, a part of the fuel gas flowing along the fuel gas channel 141A is diffused in the anode gas diffusion layer 100A. It penetrates into the inside from the surface of the layer base material 10A. Other unreacted fuel gas flows along the fuel gas flow path 141A as it is, and is discharged to the outside of the fuel cell 200.
Then, when the oxidizing gas and the fuel gas react, electric power is taken out between the cathode side separator 140K and the anode side separator 140A.

[Embodiment 1]
Next, a manufacturing method of the fuel cell gas diffusion layer 100 (cathode side gas diffusion layer 100K, anode side gas diffusion layer 100A) of the first embodiment incorporated in the fuel cell 200 having such a configuration is shown in FIG. Will be described with reference to FIG.

  In the first embodiment, as shown in the flowchart of FIG. 2, first, in the paper making process (step S <b> 11), the conductive fibers 11 that form the gas diffusion layer base material 10 and the conductive fibers 11. A papermaking base 13 is formed by making paper together with the binder 12 to be bound.

  The conductive fiber 11 includes carbon-based, metal-based, etc., but in consideration of thermal and chemical stability (corrosion resistance, conductivity, etc.), preferably carbon fiber (also called carbon-based fiber or carbon-based fiber). It is. As the carbon fiber, polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, phenol-based carbon fiber, etc. are used, and one kind may be used alone, or two or more kinds may be used in combination. The gas diffusion layer base material 10 may be selected according to desired characteristics. From the viewpoint of strength and the like, polyacrylonitrile-based carbon fiber and pitch-based carbon fiber are preferable. And when only a polyacrylonitrile-type carbon fiber is used independently, the intensity | strength of the gas diffusion layer base material 10 obtained becomes very high. On the other hand, when polyacrylonitrile-based carbon fiber and pitch-based carbon fiber are used in combination, the elasticity and flexibility of the obtained gas diffusion layer base material 10 can be ensured. Carbon fiber includes graphite fiber.

  The conductive fibers 11 such as carbon fibers may be short fibers or long fibers, but short fibers are preferable in consideration of dispersibility, ease of papermaking (papermaking properties), and the like. In addition, when the fiber length is short, it is possible to suppress the length of the passages (holes, pores, pores) serving as gas permeation paths and water discharge paths in the obtained gas diffusion layer base material 10 from being excessively long. In addition, you can acquire various directions of the passage. As a result, it is advantageous for allowing gas and moisture to permeate in a direction in which it is easy to escape, and it becomes possible to increase the permeability of gas and moisture. In addition, it is advantageous for moderate moisture retention. As short fibers, short fibers obtained by cutting continuous long fibers may be used, or continuous long fibers in a dispersion medium such as water are stirred by a stirrer (for example, a mixer, a slashfiner) or the like. It may be obtained by shortening the fiber.

  The length and diameter of the conductive fiber 11 such as carbon fiber can be appropriately selected. The average fiber length of the conductive fiber 11 such as carbon fiber is, for example, 0.2 to 50 mm, preferably 1 to 30 mm, and more The short fiber is preferably 3 to 25 mm, more preferably 5 to 15 mm. In particular, 2 to 12 mm is preferable, and more preferably in the range of 3 to 9 mm from the viewpoints of capture properties by the binder 12 during paper making and binding properties by the resin carbide described later. Further, if the fiber length is in the range of 3 to 20 mm, more preferably in the range of 4 to 10 mm, the dispersibility during paper making is good, and the conductive fibers 11 are less likely to slip through the paper making body. Adjustment and control are easy and the papermaking property is good. Furthermore, the unevenness of the basis weight of the papermaking substrate 13 is small and uniform, and the strength and the like of the obtained gas diffusion layer substrate 10 can be increased.

The average fiber diameter of the conductive fibers 11 such as carbon fibers is, for example, 1 to 60 μm, preferably 3 to 30 μm, more preferably 4 to 4 in consideration of dispersibility and the strength of the obtained gas diffusion layer base material 10. It is in the range of 20 μm. In particular, when the average fiber diameter is in the range of 4 to 20 μm, more preferably in the range of 5 to 15 μm, the gas diffusion layer substrate 10 to be obtained can ensure high gas and moisture permeability. Furthermore, 3 to 9 μm is preferable from the viewpoint of production cost and dispersibility, and 4 to 8 μm is preferable from the viewpoint of smoothness and conductivity of the obtained gas diffusion layer substrate 10. In the case of carbon fibers having a flat cross section, the average of the major axis and the minor axis is defined as the fiber diameter.
In addition, by using two or more kinds of fibers having different average diameters and average lengths, it becomes easy to adjust and control characteristics such as surface smoothness, conductivity, strength, etc. of the gas diffusion layer base material 10, but one kind alone. May be used.

The binder 12 that is made together with the conductive fibers 11 may be any one that functions as a binder that binds the conductive fibers 11 during paper making. Preferably, the binder 12 decomposes and disappears by subsequent heating. The disappeared traces become pores (pores, pores) that serve as gas and water passages of the gas diffusion layer base material 10. For example, pulp (vegetable fiber) such as wood, cellulose, cotton, bamboo and hemp, animal fibers such as wool, polylactic acid, polyvinyl alcohol (PVA), polyethylene, polypropylene, polyolefin, polyurethane, polyester, nylon, vinylon Resin fibers such as acrylic, aramid, polyacetal, and novoloid are used. These may be used individually by 1 type and may use 2 or more types together. In the case of wet papermaking, one that does not dissolve in a dispersion medium (papermaking medium) such as water described later is selected.
Further, the shape of the binder 12 may be particulate or massive, but is preferably a fibrous organic substance. If it is fibrous, the capture property of the conductive fibers 11 is good and the papermaking yield can be increased to facilitate papermaking. Furthermore, the conductive fibers 11 can be made in the papermaking substrate 13 by papermaking with the conductive fibers 11. Can improve the entanglement and reinforcement.

  In particular, pulp fibers such as wood, polyvinyl alcohol fibers, and polylactic acid fibers are suitable as the binder 12. These are good in handling properties, inexpensive, have high affinity with the carbon fibers as the conductive fibers 11, and are advantageous for appropriate dispersibility, capture, entanglement, and contact properties of the conductive fibers 11. The papermaking property can be improved and the yield can be increased. In addition, it can be eliminated by thermal decomposition at a relatively low temperature of 500 ° C. or less, the residue is hardly left behind, and vacancies serving as gas and water passages can be stably formed. In particular, it is advantageous for forming the communication hole. The blending amount of the binder 12 is, for example, in the range of 50 to 200 parts by weight, and preferably in the range of 100 to 180 parts by weight with respect to 100 parts by weight of the conductive fiber 11.

In the first embodiment, the paper-making base 13 is formed by making paper together with such conductive fibers 11 and the binder 12.
As a method for papermaking the conductive fiber 11 and the binder 12, a wet papermaking method in which the conductive fiber 11 and the binder 12 are dispersed in a dispersion medium or paper is dispersed, and the conductive fiber 11 and the binder 12 are dispersed in the air to descend. Paper making can be performed by a dry paper making method or the like, but a wet paper making method is preferred from the viewpoint of uniformity, strength, productivity, controllability of basis weight, and the like.

In the wet papermaking method, the conductive fibers 11 and the binder 12 are dispersed in a dispersion medium (papermaking medium), and papermaking is performed. As the papermaking process at this time, a known method can be adopted. For example, by mixing a mixture (slurry) in which the conductive fibers 11 and the binder 12 are dispersed in a dispersion medium using a separating member such as a mesh member, or by sucking or drying under reduced pressure, The papermaking substrate 13 can be obtained by separating the (conductive fibers 11 and the binders 12) and the dispersion medium and accumulating (aggregating) the conductive fibers 11 and the binders 12 in a solid content. More specifically, for example, the slurry-like mixture is supplied to a wet paper machine having a wire such as a long net, a short net, a circular net, etc., dehydrated in a dehydration part, pressurized and squeezed to conduct electricity. A papermaking substrate 13 composed of the fibers 11 and the binder 12 can be obtained.
As the dispersion medium at this time, water is generally employed, but an organic solvent such as toluene, xylene, cyclohexane, alcohol, or the like may be used depending on the type of material used for papermaking.
Moreover, the preparation method of the said mixture is not ask | required in particular, For example, it is also possible to mix and disperse a papermaking component using rotary apparatuses, such as a pulper.

  In addition, it is preferable that the density | concentration of the conductive fiber 11 and the binder 12 is in the range of 1-50 g / L in the said slurry-like mixture. Within this concentration range, the yield of papermaking is good, and furthermore, the dispersibility of the conductive fibers 11 and the binder 12 is good and aggregation does not easily occur. can get.

Thus, in the first embodiment, in the paper making process (step S11), the paper making base 13 is formed by paper making the conductive fibers 11 and the binder 12 together.
At this time, the paper making base material 13 has a basis weight (weighing) in the range of 10 to ²⁰⁰ g / m ^{2 and} a thickness in the range of ^{20 to} 400 μm, for example.

In the case of carrying out the present invention, in addition to the conductive fibers 11 and the binder 12, depending on the desired properties of the gas diffusion layer base material 10, a conductive material such as carbon particles (carbon particles) or metal particles is appropriately used. It is also possible to form a papermaking base 13 by blending substances and making paper together with the conductive fibers 11 and the binder 12. That is, the papermaking substrate 13 may be formed of a composite material of carbon fibers and carbon particles.
Further, as with the first carbon precursor resin 14A such as a phenol resin described later, fibers that can be carbonized and become carbon sources, such as acrylic polymers (acrylic fibers such as polyacrylonitrile fibers), cellulose polymers (cellulose) Paper such as rayon, polynosic fiber, etc.), phenolic polymer (phenolic fiber) and the like may be made together with the conductive fiber 11 and the binder 12.

  In addition, binders (glue agent, paper strength enhancer), for example, polyvinyl acetate, polyacrylonitrile, cellulose, polyethylene oxide, to improve papermaking property, binding property (strength), handling property, handling property, etc. as required Polyacrylamide, styrene-butadiene rubber, starch, corn starch and the like can also be used. Such a binder may be mixed at the time of paper making and may be wet-made with the conductive fibers 11 and the binder 12, or may be impregnated after paper making. In addition, for example, the papermaking base 13 can be formed using a flocculant, a viscosity modifier, a surfactant, and the like.

  Furthermore, when carrying out the present invention, a mechanical entanglement method (needle punching method, etc.), a high pressure liquid injection method (water jet punching method, etc.), and a high pressure gas injection method (steam jet punching method, etc.) at the time of papermaking are performed as necessary. It is also possible to increase the strength, handling property, conductivity, and the like of the papermaking substrate 13 by performing the entanglement process by the above method to entangle the conductive fibers 11 three-dimensionally. Furthermore, an operation for controlling the degree of orientation of the fiber may be performed by adjusting the dehydration rate of the dispersion medium. Further, the paper quality of the sheet-like (paper-like) paper-making substrate 13 may be adjusted by, for example, compressing the paper-making substrate 13 produced by a paper machine through a roll.

  Next, in the first embodiment, the carbon precursor resin impregnation step (step S12) is performed on the paper making base material 13 obtained by paper making the conductive fiber 11 and the binder 12 together. Then, the first carbon precursor resin 14A is impregnated.

The first carbon precursor resin 14A to be impregnated into the papermaking base material 13 in this carbon precursor resin impregnation step (step S12) is a high level in a non-oxidizing atmosphere in the subsequent carbonization / graphitization step (step S40). A resin (resin that becomes a carbon source) that is carbonized and graphitized by heat treatment (hereinafter also simply referred to as “carbonization” without distinction) to become a conductive carbide, and the conductive fibers 11 and the like after carbonization It is sufficient that it functions as a binding component for binding, such as phenol resin, furan resin, epoxy resin, melamine resin, imide resin, urethane resin, aramid resin, urea resin, unsaturated polyester resin, pitch, etc. A thermosetting resin or the like is used.
Among them, a phenol resin that has good handling properties, a high residual carbon ratio (carbonization rate) remaining as a conductive substance after carbonization, and a strong binding force for binding the conductive fibers 11 such as carbon fibers is preferable.

  As phenol resin, resol type phenol resin, cresol type phenol, xylenol resin and the like are used in addition to phenol. In particular, the resole phenolic resin obtained by the reaction of phenols (phenol, resorcin, cresol, xylol, etc.) and aldehydes (formaldehyde, paraformaldehyde, furfural, etc.) in the presence of an ammonia catalyst reduces the durability of the fuel cell 200. It is preferable at the point which does not contain the metal component which causes this. Further, an aqueous phenol resin dissolved or dispersed (including emulsification and the like) in water may be used, or a solvent type (solvent dilution type) may be used.

  The blending amount of the first carbon precursor resin 14A such as a phenol resin to be carbonized is set according to the desired characteristics of the gas diffusion layer base material 10, but the resin carbide in the gas diffusion layer base material 10 If the ratio is in the range of 10 to 90% by mass, preferably 15 to 80% by mass, the conductivity and strength of the gas diffusion layer substrate 10 are sufficiently high. More preferably, if it is in the range of 15 to 40% by mass, and more preferably 20 to 40% by mass, the gas diffusion layer substrate 10 has high moisture and gas permeability. In addition, deformation due to thermal shrinkage during carbonization is small, and shape retention is enhanced.

  As a method for impregnating the paper making base material 13 with the first carbon precursor resin 14A such as a phenol resin, a method of immersing the paper making base material 13 in a resin dispersion liquid, a resin dispersion liquid in the paper making base material 13 or the like. And a method of transferring a resin film on the papermaking substrate 13 and the like. The paper making base material 13 is immersed in the dispersion of the first carbon precursor resin 14A from the viewpoint of productivity and uniformity, although it is appropriately selected depending on the properties, addition amount, etc. of the first carbon precursor resin 14A. Thus, it is preferable to impregnate the papermaking substrate 13 with the first carbon precursor resin 14A. Further, squeezing may be performed by a dip-nip method using a squeezing device, and in such a squeezing device, adjustment and control of the impregnation amount of the first carbon precursor resin 14A can be easily performed by changing the roll interval. It can be carried out.

  In this way, in the impregnation with the first carbon precursor resin 14A, usually, a resin in which the first carbon precursor resin 14A is dispersed in a dispersion medium such as alcohols, ketones (acetone, etc.), toluene, water or the like. For example, in the case of a phenol resin, a dispersion medium such as alcohol such as methanol, ethanol, butyl alcohol, or water is used.

Thus, in the first embodiment, in the paper making step (step S11), the conductive fibers 11 and the binder 12 are made together to form the paper making base 13, and then the carbon precursor resin impregnation step (step S12). ), By impregnating the paper making base material 13 with the first carbon precursor resin 14A, the precursor 15 of the gas diffusion layer base material 10 (hereinafter referred to as “gas diffusion layer base material precursor 15”, or simply (Referred to as “base precursor 15”).
The paper making process (step S11) and the carbon precursor resin impregnation process (step S12) correspond to the base material precursor forming process (step S10) for forming the gas diffusion layer base material precursor 15. That is, the base material precursor forming step (step S10) in the first embodiment includes a paper making step (step S11) and a carbon precursor resin impregnation step (step S12).

  As described above, in the first embodiment, in the paper making process (step S11), the conductive fiber 11 and the binder 12 are made together to form the paper making base 13, and the subsequent carbon precursor resin impregnation process (step S12). ), The paper making base material 13 is impregnated with the first carbon precursor resin 14A, whereby the conductive fibers 11 and the binder 12 are made together, and the first carbon precursor resin 14A is adhered. Thus, the base material precursor 15 is produced.

  Next, the conductive fiber 11 and the binder 12 are made in this way, and the base material precursor 15 containing the first carbon precursor resin 14A is formed in a molding step (step S20). The surface of the substrate precursor 15 is smoothed by calendar molding, press molding (pressure molding), or the like.

As a result, the unevenness on both the front and back surfaces in the thickness direction of the substrate precursor 15 is reduced and the surface is smoothed, and the contact with the peripheral layers such as the catalyst layer 110 and the separator 140 is increased when the substrate precursor 15 is incorporated. The resistance can be reduced. In addition, even if protrusions such as fiber frays are present on the surface of the substrate precursor 15, it can be suppressed by pressing or the like. Further, by adjusting the orientation of the conductive fibers 11 or adjusting the density of the base material precursor 15 by pressing, the gas diffusion layer 100 has characteristics such as conductivity, strength, moisture and gas permeability. It is possible to adjust. That is, the molding pressure at this time is set in consideration of desired characteristics (conductivity, strength, moisture and gas permeability, etc.) of the gas diffusion layer 100, and is within a range of, for example, 0.01 to 10 MPa. Is done.
In addition, since the base material precursor 15 is densified by molding, it is included in the paste-like coating liquid 24 that is applied to the base material precursor 15 in the next gas diffusion layer precursor formation step (step 30). The conductive material 21 for forming the microporous layer 20 and the second carbon precursor resin 14B are less likely to enter the inside of the base material precursor 15, and from the conductive material 21 and the second carbon precursor resin 14B. The resulting microporous layer precursor 25 can be formed on the surface of the substrate precursor 15.

  In the molding step (step S20) at this time, moisture of the substrate precursor 15 is removed and dried by molding, for example, heating at 50 to 200 ° C. Further, the first carbon precursor resin 14A may be cured by heating at the time of molding. By pasting the thermosetting first carbon precursor resin 14A such as phenol resin contained in the front substrate precursor 15 in the next gas diffusion layer precursor forming step (step S30), a paste-like coating is applied. The liquid 24 can be prevented from soaking (penetrating) into the substrate precursor 15. In addition, since the carbonization and graphitization step (step 40) described later can suppress fixation during carbonization of the first carbon precursor resin 14A, it is possible to fix the first carbon precursor resin 14A. It is possible to improve the contact property, further prevent the deformation of the gas diffusion precursor 50, and improve the strength of the gas diffusion layer 100 and the bonding property with the surrounding layers.

  Subsequently, a paste-like coating liquid for forming the microporous layer 20 of the gas diffusion layer 100 in the gas diffusion layer precursor formation step (step S30) on the base material precursor 15 thus formed. 24 is applied.

  Here, the coating liquid 24 for forming the microporous layer 20 according to the first embodiment is a paste-like mixture containing the conductive material 21, the second carbon precursor resin 14B, and the dispersion medium 23. .

As the conductive material 21, there are a carbon type and a metal type, but considering thermal and chemical stability (corrosion resistance, conductivity, etc.), for example, carbon black, graphite (graphite), vapor growth carbon, activated carbon, etc. The carbon powder (carbon particles) is preferred. These can be used singly or in appropriate combination of two or more. Carbon fiber or the like can be used as long as it has conductivity, but the functional surface (current collection function, repellent property) of the microporous layer 20 that forms finer pores than the gas diffusion layer substrate 10 can be used. In view of water performance, mitigation of non-uniformity of the gas diffusion layer base material 10, and contact with the catalyst layer 110), powdery carbon particles are usually the main component. In addition, when blending carbon fibers in addition to carbon particles, the strength and conductivity of the microporous layer 20 can be improved.
Among these, powdered conductive materials such as carbon black and graphite are preferable from the viewpoints of handling properties, purity, and the like, and from the viewpoints of conductivity, strength, gas and moisture permeability in the microporous layer 20, and the like. In particular, when the conductive fibers 11 constituting the substrate precursor 15 to be coated are carbon fibers, the powdered conductive material 21 such as carbon black or graphite is also preferably compatible with the carbon fibers. Examples of carbon black include carbon particles such as acetylene black, ketjen black, furnace black, thermal black, channel black, and lamp black.

The second carbon precursor resin 14B is carbonized / graphite by high heat treatment in a non-oxidizing atmosphere in the subsequent carbonization / graphitization step (step S40) in the same manner as the first carbon precursor resin 14A described above. Any resin that is converted into a conductive carbide (resin that becomes a carbon source) and functions as a binding component that binds the conductive material 21 and the like after carbonization can be used. Furan resins, epoxy resins, melamine resins, imide resins, urethane resins, aramid resins, urea resins, unsaturated polyester resins, thermosetting resins such as pitch, and the like are used. Among them, a phenol resin having good handling properties, a high residual carbon ratio (carbonization rate) remaining as a conductive substance after carbonization, and a strong binding force for binding the conductive material 21 such as carbon powder (carbon particles). preferable. Of course, an aqueous phenol resin dissolved or dispersed in water (including emulsification and the like) may be used, or a solvent type (solvent dilution type) may be used.
The second carbon precursor resin 14B may use the same resin as the first carbon precursor resin 14A, or may be a resin different from the first carbon precursor resin 14A.

  The blending amount of the second carbon precursor resin 14B such as a phenol resin to be carbonized is set according to desired characteristics of the microporous layer 20, but the ratio of the resin carbide in the microporous layer 20 is 10%. If it is in the range of ˜50 mass%, preferably 20 to 40 mass%, the conductivity and strength of the microporous layer 20 are improved without impeding the permeability of moisture and gas. In addition, deformation due to thermal shrinkage during carbonization is small, and shape retention is improved. For example, a phenol resin is used as the second carbon precursor resin 14B, and the resin amount (solid content) of the phenol resin is 10 to 100 parts by mass with respect to 100 parts by mass of the conductive material 21 such as carbon powder. It can adjust to the ratio of the above-mentioned resin carbide by setting it as the range.

  As the dispersion medium 23 in which the conductive material 21 and the second carbon precursor resin 14B are dispersed, a dispersion medium 23 such as alcohols, ketones (acetone, etc.), toluene, water, or the like is used. For example, when the second carbon precursor resin 14B is a phenol resin, an alcohol such as methanol, ethanol or butyl alcohol, or a dispersion medium 23 such as water is preferably used.

  The mixing and dispersing process in which the conductive material 21 and the second carbon precursor resin 14B are dispersed in the dispersion medium 23 is performed, for example, by stirring using a mixer such as a general disper or planetary, a bead mill, or the like. In particular, by blending the second carbon precursor resin 14B such as a phenol resin, the conductive material 21 can be highly dispersed without applying a high shear stress and without using a dispersant. Is possible. And since it is highly dispersed without applying high shear stress, if the conductive material 21 is carbon particles, the three-dimensional structure of the carbon particles is easily maintained, and the strength of the resulting microporous layer 20 is improved. Can be planned.

However, when carrying out the present invention, the conductive material 21 and the second carbon precursor resin 14B may be dispersed using a dispersant. When the dispersibility of the components of the coating liquid 24 is increased by using a dispersant, the piping or pump of the coating apparatus is not clogged during coating, and coating unevenness due to concentration changes is not caused.
In particular, in the first embodiment, after the paste-like coating liquid 24 is applied to the substrate precursor 15, the carbonization / graphitization is performed. The dispersant used for the paste-like coating liquid 24 is as follows. Since it can be removed at a high heat treatment temperature in the carbonization / graphitization step (step S40), it is not limited to the selection of a dispersant having a low decomposition temperature, and the degree of freedom in selecting the dispersant is increased. Examples of the dispersant include polyoxyethylene tridecyl ether, polyoxyethylene alkylphenyl ether (Triton X-100, etc.), polyoxyethylene lauryl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene alkylene. Nonionic (nonionic) surfactants such as alkyl ethers and polyethylene glycol alkyl ethers, cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium chlorides and alkylpyridium chlorides, polyoxyethylene fatty acid esters, acidic groups Surfactants such as anionic surfactants such as structurally modified polyacrylates, polyethylene oxide, methylcellulose, hydroxyethylcellulose, Ethylene glycol (e.g., ethers alkylphenol polyethylene glycol ethers of higher aliphatic alcohols and polyethylene glycol, etc.), a thickener polyvinyl alcohol or the like can be used.

  In the first embodiment, in the gas diffusion layer precursor forming step (step S30), the conductive material 21 for forming the microporous layer 20 and the second carbon precursor resin 14B are used as the dispersion medium 23. By applying the dispersed paste-like coating liquid 24 to one surface of the substrate precursor 15 in the thickness direction, a precursor 50 of the gas diffusion layer 100 (hereinafter referred to as “gas diffusion layer precursor 50”) is formed. .

  As a method of applying the paste-like coating liquid 24 for forming the microporous layer 20 to the substrate precursor 15, brush coating, brush coating, roll coater method, reverse roll coater method, bar coater method, die coater method, blade method, knife coater Method, spin coater method, screen printing, rotary screen printing, curtain coating method, dip coater method, spray coater method, gravure coater method, applicator, spray spraying and the like. In particular, in the application by a (reverse roll) coater or the like, the surface smoothness of the gas diffusion layer precursor 50 obtained by applying the paste-like coating liquid 24 to the base material precursor 15 can be improved. It is not limited. And by blending the second carbon precursor resin 14B such as a phenol resin, it is possible to highly disperse the conductive material 21 without using the above-described dispersant separately. At the time of coating, clogging of piping and pumps of the coating apparatus is unlikely to occur, and coating unevenness due to concentration change is also unlikely to occur.

Here, the base material precursor 15 to which the paste-like coating liquid 24 is applied is the first by impregnating the first carbon precursor resin 14A into the aggregate made up of the paper fibers made of conductive fibers 11 such as carbon fibers and the binder 12. The carbon precursor resin 14A is adhered and densified by molding, and since it is before carbonization / graphitization, there are few voids. Furthermore, the paste-like coating liquid 24 has an appropriate viscosity by containing the second carbon precursor resin 14B such as a phenol resin.
Therefore, when the paste-like coating liquid 24 is applied to the base material precursor 15, the components of the paste-like coating liquid 24 hardly penetrate (infiltrate) into the base material precursor 15. The conductive material 21 and the second carbon precursor resin 14B adhere to the surface, and the precursor 25 of the microporous layer 20 (hereinafter referred to as “microporous layer precursor”) made of the conductive material 21 and the second carbon precursor resin 14B. A body 25 ”) is formed. Further, even if a part of the paste-like coating liquid 24 enters the voids in the surface layer of the substrate precursor 15, this results in an improvement in adhesion with the substrate precursor 15.

  In the case where the paste-like coating liquid 24 is applied to the base material precursor 15 in this way, the base material precursor 15 can be finished in any shape depending on the shape of the base material precursor 15. That is, the sheet-like material requires a molding process corresponding to the shape of the base material precursor 15 and increases the cost, but the coating type material can follow the shape of the base material precursor 15 to further reduce the cost. Can do.

  Thus, in the gas diffusion layer precursor formation step (step S30), the conductive material 21 for forming the microporous layer 20, the second carbon precursor resin 14B, and the dispersion medium 23 are applied to the base material precursor 15. By applying the paste-like coating liquid 24 having the main composition, a gas diffusion layer precursor 50 composed of the base material precursor 15 and the microporous layer precursor 25 is obtained.

In particular, the first embodiment is a configuration in which the paste-like coating liquid 24 for forming the microporous layer 20 is applied to the base material precursor 15 before carbonization / graphitization, and as described above, before carbonization / graphitization. In the base material precursor 15, since the components of the paste-like coating liquid 24 are difficult to soak (penetrate), in the paste-like coating liquid 24, the viscosity is increased to prevent the base material precursor 15 from penetrating. It is not always necessary to add a sticking agent. Therefore, the occurrence of unevenness during application due to the use of a thickener to increase the viscosity is small, and uniform application is possible.
In addition, the paste-like coating solution 24 contains the second carbon precursor resin 14B such as a phenol resin, so that it has an appropriate viscosity and viscosity, and separately contains a dispersant and a thickener. Even if not, the conductive material 21 is highly dispersed, and the applicability is ensured.
However, when the present invention is implemented, as described above, in the paste-like coating liquid 24, a surfactant or the like for increasing the dispersibility of the conductive material 21 or the like is increased as necessary. It is also possible to add a thickener for the purpose. And even if these surfactants and thickeners are blended in the paste-like coating liquid 24, the surfactants and thickeners are thermally decomposed by the high-temperature heat treatment in the subsequent carbonization / graphitization step (step S40). Therefore, the burden of the drying and baking process in the subsequent drying and baking process (step S60) is not increased.

  In the case of carrying out the present invention, gas diffusion may be performed as necessary at the stage where the paste-like coating liquid 24 is applied to the substrate precursor 15 before the next carbonization / graphitization step (step S40). A drying step for removing moisture from the layer precursor 50 may be provided.

  The drying method at this time is not particularly limited, and may be natural drying. For example, a hot air furnace that circulates and supplies hot air, an atmospheric furnace that uses a high-temperature heater, an IR furnace that uses an infrared heater, a micro-furnace Drying may be performed by a non-contact drying method using equipment such as a microwave oven using a wave, or by a contact drying method by contacting a heated roll or hot plate. The heating condition at this time may be a temperature at which moisture in the gas diffusion layer precursor 50 can be removed, and is usually set within a range of 50 ° C to 200 ° C. In addition, you may harden thermosetting 1st carbon precursor resin 14A and 2nd carbon precursor resin 14B, such as a phenol resin, by the heating at the time of drying. Before the next carbonization / graphitization step (step 40), the first carbon precursor resin 14A and the second carbon precursor resin 14B are cured to vaporize the carbon precursor resins 14A and 14B during carbonization. Therefore, the contact with the conductive fibers 11 and the conductive material 21 can be improved, the deformation of the gas diffusion precursor 50 can be prevented, and the strength of the gas diffusion layer 100 and the surrounding layers can be prevented. It becomes possible to improve the joining property.

  Next, a carbonization / graphitization process (step S40) is performed on the gas diffusion layer precursor 50 obtained by applying the paste-like coating liquid 24 for forming the microporous layer 20 to the base material precursor 15 in this way. ), High-temperature heat firing is performed in a non-oxidizing atmosphere.

In the carbonization / graphitization step (step S40), in a non-oxidizing atmosphere such as inert treatment (inert gas), the temperature is usually 1000 to 3500 ° C., preferably 1200 to 3000 ° C. for 10 minutes to By performing the heating and baking treatment for 1 hour, the first carbon precursor resin 14A in the base material precursor 15 and the second carbon precursor resin 14B in the microporous layer precursor 25 are carbonized and graphitized.
Here, if the maximum temperature during the heat treatment is too low, the strength and conductivity of the resulting gas diffusion layer 100 are small, whereas if the maximum temperature during the carbonization is too high, the fiber strength of the conductive fibers 11 is low. There is a possibility that deterioration, deterioration of the conductive material 21, dropping off or the like may occur.
The heating and firing conditions such as the heating temperature, time, and heating atmosphere are set according to the type and amount of the compounding material, the desired characteristics of the gas diffusion layer 100, etc., but the conductive fiber 11 and the conductive material 21 When the carbon-based first carbon precursor resin 14A and the second carbon precursor resin 14B are phenol resins, they are 1000 to 3500 ° C., more preferably 1200 to 3000 ° C., and still more preferably 1500 to 2800 in a nitrogen atmosphere. By heating in the temperature range of ° C., impurities in the gas diffusion layer precursor 50 are reduced, and in the obtained gas diffusion layer 100, electrical characteristics such as high strength and high conductivity (specific resistance, etc.) And corrosion resistance. The heat treatment time at the maximum temperature is usually 0.5 to 20 minutes.

Here, the heating and firing conditions are set according to the type and amount of the compounding material, the desired properties (conductivity, etc.) of the gas diffusion layer base material 10, and the first carbon precursor resin 14A and the first carbon precursor resin 14A. No distinction is made between carbonization and graphitization of the second carbon precursor resin 14B.
The inert atmosphere for making the non-oxidizing atmosphere can be obtained by circulating an inert gas such as nitrogen gas, argon gas, or helium gas in the heating furnace. Depending on the case, it is also possible to carry out a heat-firing process under an atmosphere of carbon dioxide gas or the like under vacuum.
The heat treatment under an inert treatment (inert gas) atmosphere includes a heat treatment at 300 to 800 ° C. (pretreatment; pre-baking and precarbonization) and a heat treatment at 1000 to 3500 ° C. (main treatment; post-carbonization). , Graphitization).

As a method of heating and firing at this time, for example, a hot air furnace that circulates and supplies hot air, an atmospheric furnace that uses a high-temperature heater, an IR furnace that uses an infrared heater, a microwave furnace that uses a microwave, and the like are used. There are a non-contact method and a contact method in which a heated roll or hot plate is contacted and dried.
In a non-contact method such as a method of blowing hot air in a hot air furnace or the like, operability and maintainability are easy, and dropping off due to contact with a heat source such as the conductive fiber 11 or the conductive material 21 is prevented.
On the other hand, for example, in a contact method such as a method of hot pressing in the thickness direction (hydraulic press, hot press, belt press, roll press, etc.), the surface of the gas diffusion layer precursor 50 particularly in heating while applying a surface pressure. The smoothness can be improved, and the contact property with the peripheral layers such as the catalyst layer 110 and the separator 140 can be increased when the fuel cell 200 is incorporated. If the press pressure is increased more than necessary, the pores may be filled, and the gas diffusion layer precursor 50 becomes dense, and it becomes difficult to discharge gas and the like generated during heating and firing. There is a risk of causing deformation or damage. For this reason, the molding pressure is set in consideration of the target characteristics (strength, permeability, etc.) of the gas diffusion layer 100, and is, for example, a press pressure of 0.01 to 2 MPa.

  By such a high-temperature baking treatment in a non-oxidizing atmosphere, the first carbon precursor resin 14A and the second carbon precursor resin 14B such as a phenol resin are carbonized and graphitized. The carbonized and graphitized resin, that is, resin carbide, binds the conductive fibers 11 and the conductive material 21 to form a strong conductive path, and the gas diffusion layer base material 10 and the microporous layer 20 obtained. The conductivity and strength of the can be increased.

  That is, in the carbonization / graphitization step (step S40), the gas diffusion layer precursor 50 is subjected to high-temperature heat treatment in a non-oxidizing atmosphere, so that the first carbon precursor such as a phenol resin in the base material precursor 15 is obtained. The body fibers 14A are carbonized and graphitized, and the conductive fibers 11 are bound by a resin carbide obtained by carbonizing and graphitizing the first carbon precursor resin 14A. Further, the second carbon precursor resin 14B such as a phenol resin in the microporous layer precursor 25 is carbonized and graphitized, and the second carbon precursor resin 14B is carbonized and graphitized to be conductive by a resin carbide. The material 12 is bound. Further, at the boundary between the base material precursor 15 and the microporous layer precursor 25, the conductive fiber is formed by the resin carbide obtained by carbonizing the first carbon precursor resin 14A such as a phenol resin or the second carbon precursor resin 14B. 11 and the conductive material 21 are bound together. Thereby, in the gas diffusion layer 100 to be obtained, the fixing of the gas diffusion layer base material 10 and the microporous layer 20 becomes high. That is, the gas diffusion layer substrate 10 and the microporous layer 20 are strongly connected, and the microporous layer 20 is difficult to peel from the gas diffusion layer substrate 10 even when assembled to the fuel cell 200. Further, the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 is small.

  In this way, in the carbonization / graphitization step (step S40), the gas diffusion layer substrate 50 is subjected to high heat treatment in a non-oxidizing atmosphere, whereby the substrate on which the first carbon precursor resin 14A such as a phenol resin is disposed. In the microporous layer precursor 25 in which the precursor 15 and the second carbon precursor resin 14B are arranged, the first carbon precursor resin 14A such as a phenol resin and the second carbon precursor resin 14B are carbonized. . And the conductive fiber 11 and the conductive material 21 are bound by those resin carbides. Further, the substrate precursor 15 becomes porous, and micropores smaller than the voids (pores) of the substrate precursor 15 are formed in the microporous layer 20. Further, when a binder 12 such as polyvinyl alcohol, polylactic acid, pulp, etc. is disposed in the base material precursor 15 before carbonization / graphitization, the binder 12 is decomposed and disappears, and the disappearance trace is It becomes a void (pore). Even when a part of the first carbon precursor resin 14A such as a phenol resin or the second carbon precursor resin 14B is lost, the disappearance trace becomes a void. Further, as described above, even when a dispersant such as a surfactant or a thickener is disposed in the microporous layer precursor 25, the microporous layer precursor 25 is dispersed by the high-temperature heat treatment in the carbonization / graphitization step (step S40). The agent is removed. Therefore, the burden of removing the dispersant is not applied in the subsequent drying and firing step (step S60).

  Next, in the first embodiment, the water repellent resin 31 in the water repellent resin impregnation step (step S50) is performed on the gas diffusion layer precursor 50 thus heated and fired in a non-oxidizing atmosphere. Impregnate.

Examples of the water-repellent resin 31 impregnated in the water-repellent resin impregnation step (step S50) include, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and perfluoroalkoxy fluorine. Fluorine series such as resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVdF), etc. Resin, silicone resin or the like is used. These can be used singly or in appropriate combination of two or more.
Among these, a fluorine-based polymer material excellent in water repellency, corrosion resistance during electrode reaction, and the like is preferable, and in particular, PTFE that provides high water repellency is preferable. PTFE may be a tetrafluoroethylene homopolymer, derived from halogenated olefins such as chlorotrifluoroethylene and hexafluoropropylene, and other fluorine-based monomers such as perfluoro (alkyl vinyl ether). It may be a modified PTFE containing units.

  Incidentally, it is desirable that the water repellent resin 31 has an average molecular weight in the range of 50,000 to 1,000,000. When the average molecular weight is too low, the binding property as a binder for bonding the conductive fibers 11 and the conductive material 21 is small. On the other hand, when the average molecular weight is too large, the fibers tend to be fiberized at the time of mixing and become poorly dispersed. Therefore, the stability may decrease, and the concentration may change due to fibrosis. When the water-repellent resin is a fluoropolymer, the fluoropolymer is difficult to dissolve in a solvent, and therefore it is difficult to measure the average molecular weight with melt viscosity. For this reason, the specific gravity method which calculates | requires an average molecular weight from the relationship between specific gravity and a number average molecular weight is applied.

When the water-repellent resin 31 is impregnated, the water-repellent resin 31 such as a fluorine-based resin is not normally dispersed in water as it is, so that the water-repellent resin 31 is submerged in water with an appropriate surfactant (dispersant). Impregnated in the form of a dispersion, for example, an emulsion in which a water-repellent resin 31 such as a fluorine-based resin is emulsified in water or a dispersion in which a water-repellent resin 31 such as a fluorine-based resin is dispersed in water or the like .
Incidentally, an emulsion (also referred to as an “emulsion”) is also called an emulsion, and the original meaning is that the liquid particles form a milky form as colloidal particles or coarser particles in the liquid (dispersed system). Although it is (Saburo Nagakura et al., “Iwanami Rikagaku Dictionary (5th edition)” page 152, published by Iwanami Shoten Co., Ltd. on February 20, 1998), it is generally used in a broader sense in this specification. The term “emulsion” is used herein as “a solid or liquid particle dispersed in a liquid”.

Examples of the impregnation method of the water repellent resin 31 include a gas diffusion layer precursor after carbonization and graphitization in a water repellent resin emulsion such as a fluorine-based resin or a dispersion of the water repellent resin 31 such as a water repellent resin dispersion. The body 50 is immersed, or a dispersion of the water repellent resin 31 is applied to the gas diffusion layer precursor 50 after carbonization / graphitization (kiss coating method, dipping method, spray method, curtain coating method, roller contact method, etc.) By doing so, the water-repellent resin 31 can be impregnated inside the gas diffusion layer precursor 50. Of course, the squeezing may be performed by a dip-nip method or the like using a squeezing device. In such a squeezing device, the amount of the water-repellent resin 31 can be adjusted and controlled by changing the roll interval.
The impregnation method is appropriately selected depending on the type, nature, added amount, etc. of the water repellent resin 31, but from the viewpoint of uniformity and productivity distributed throughout the gas diffusion layer precursor 50 after carbonization / graphitization, the water repellency. The gas diffusion layer precursor 50 after carbonization / graphitization is preferably immersed in the dispersion liquid of the resin 31.

Here, when there is too little content of the water-repellent resin 31, water repellency and a binder effect are insufficient. On the other hand, when there is too much content, the void | hole of the microporous layer 20 will decrease especially, and gas permeability will fall. For example, when the water repellent resin 31 is PTFE, the amount of adhesion to the gas diffusion layer 100 in terms of solid content is 5 to 100 g / m ² , preferably 10 to 50 g / m ² .

Further, in the first embodiment, after the water-repellent resin 31 is impregnated in the gas diffusion layer precursor 50 in this way, the drying and baking are performed in the drying and baking process (step S60).
By this drying and firing, the dispersant contained in the dispersion liquid of water and the water repellent resin 31 is removed. If the removal of the dispersant by drying and baking at this time is insufficient, moisture is captured by the remaining hydrophilic group of the dispersant, so that sufficient water repellency can be ensured in the obtained gas diffusion layer 100. Therefore, when applied to the fuel cell 200, practical drainage cannot be obtained. Therefore, the drying and baking temperature is set to a temperature and time at which the dispersant contained in the dispersion of the water-repellent resin 31 can be removed by thermal decomposition and volatilization.

Here, the dispersant to be removed by thermal decomposition / volatilization by heating in the drying and firing step (step S60) is the water repellent resin 31 such as a fluororesin in the previous water repellent resin impregnation step (step S50). For the purpose of uniformly impregnating the entire gas diffusion layer precursor 50 after carbonization / graphitization, a small amount of a dispersant such as a surfactant used to uniformly disperse the water repellent resin 31 in the dispersion medium. is there. That is, in the first embodiment, the conductive material, the water repellent resin, and the dispersing agent (surfactant, thickener) for dispersing the conductive material and the water-repellent resin on the gas diffusion layer base material 10 that has been carbonized and graphitized as in the past. Etc.) is not applied to form a coating film of the microporous layer 20, but is used to form the microporous layer 20 on the substrate precursor 15 before carbonization / graphitization. After applying the paste-like coating liquid 24 and carbonizing / graphitizing, the gas diffusion layer precursor 50 is impregnated with the water-repellent resin 31 without applying the paste-like coating liquid 24 for forming the microporous layer 20. Therefore, the content of the dispersant inhibiting water repellency is small in the gas diffusion layer precursor 50 to be dried and fired in the drying and firing step (step S60). In the first embodiment, the paste-like coating liquid 24 for forming the microporous layer 20 is thus applied to the base material precursor 15 before carbonization / graphitization, and the carbonization / graphitization step (step S40). In this case, since the microporous layer precursor 25 is heated and fired together with the base material precursor 15, a dispersant such as a surfactant or a thickener is disposed in the paste-like coating liquid 24 for forming the microporous layer 20. However, the dispersant at this time is removed by the high heat treatment in the carbonization / graphitization step (step 40).
Therefore, the obtained gas diffusion layer 100 exhibits sufficient water repellency even in a short time and at a low temperature by drying and baking treatment as compared with the conventional case.

That is, a microporous layer forming paste 20 containing a conductive material and a water-repellent resin is applied to the carbonized porous gas diffusion layer base material 10 to form a microporous layer 20 of a carbon structure. In the conventional design to be formed, since a conductive material and a water-repellent resin contained in the paste mixture for forming the microporous layer need to be dispersed, a large amount of a dispersant is used, and the microporous layer for heating and firing is used. Since the content of the dispersant in the coating film component is large, heating at a high temperature is necessary to sufficiently remove the dispersant and to exhibit water repellency. In particular, conventionally, the porous gas diffusion layer base material 10 that has been carbonized is coated with a paste-like mixture for forming a microporous layer containing a conductive material and a water-repellent resin. A water repellent resin such as PTEF was dispersed using a dispersant so that the components of the paste mixture for forming the microporous layer did not penetrate into the gas diffusion layer base material 10 due to the porosity of the layer base material 10. After the impregnation (water repellency treatment) of the water repellent resin emulsion (or dispersion) was performed on the gas diffusion layer substrate 10, the paste mixture for forming the microporous layer was applied. In addition, a dispersant such as a thickener may be disposed in the paste mixture for forming a microporous layer so as not to soak into the gas diffusion layer base material 10 (penetration), and the viscosity may be increased. There were many.
For this reason, in the conventional baking that is performed after applying a paste-like mixture for forming a microporous layer containing a conductive material and a water-repellent resin to a porous carbon diffusion layer base material 10 that has been carbonized, In order to sufficiently remove the agent and develop water repellency, it is generally necessary to heat at a high temperature of 300 ° C to 360 ° C.

  On the other hand, in the first embodiment, as described above, the paste precursor coating liquid 24 for forming the microporous layer 20 is applied to the base precursor 15 before carbonization / graphitization, and the base precursor is thus obtained. 15, the microporous layer precursor 25 formed on the substrate precursor 15 is carbonized and graphitized under a predetermined heating condition. The carbonized and graphitized gas diffusion layer precursor 50 includes a substrate precursor. A microporous layer precursor 25 made of a carbide of the conductive material 21 and the second carbon precursor resin 14B is formed on the surface of the body 15. Therefore, the gas diffusion layer precursor 50 made porous by carbonization / graphitization is subjected to water repellent treatment as in the prior art, and then a large amount of dispersion for dispersing the conductive material, the water repellent resin, and them. It is not necessary to apply a paste-like mixture for forming a microporous layer containing an agent, and only a water repellent treatment is performed.

Therefore, in the first embodiment, the amount of the dispersant present in the gas diffusion layer precursor 50 to be dried and fired is small. That is, even when a dispersing agent such as a surfactant for dispersing the conductive fibers 11 is blended in the microporous layer forming paste-like coating liquid 24, the high heating temperature condition in the carbonization / graphite step (step S40) described above. Since the dispersing agent blended in the microporous layer forming paste-like coating liquid 24 is decomposed and removed by firing, the gas-diffusing layer precursor 50 to be dried and fired has a microporous layer-forming paste-like coating liquid 24. There is no remaining dispersant disposed therein, and only a small amount of the dispersant used for dispersing the water-repellent resin 31 is present.
For this reason, in the drying and baking after impregnating the water-repellent resin 31, it is possible to sufficiently remove moisture and the dispersant even in a shorter time and at a lower temperature than in the past. For example, when a PTFE resin emulsion is used as the water repellent resin 31, a dispersant (dispersant for dispersing the water repellent resin 31) that inhibits moisture and water repellency even under a low heating temperature condition of 200 to 250 ° C. Completely removed, the resulting gas diffusion layer 100 exhibits high water repellency.

That is, in the drying and firing step (step S60) of the first embodiment, only the dispersant and water used for dispersing the water-repellent resin 31 are removed, so that the water and dispersant are decomposed and volatilized to disappear. The drying and firing necessary for the above, in other words, the drying and firing necessary for developing the water repellency by the water-repellent resin 31 may be performed at a low temperature. In addition, it is possible to shorten the time required for drying and baking for decomposing / volatilizing and erasing moisture and a dispersant to develop water repellency. Accordingly, the furnace length of the drying and firing furnace can be shortened, and further, the time for raising the temperature to a predetermined temperature for the development of water repellency can be shortened, so that the time required for the drying and firing treatment can be shortened.
Therefore, the load concerning drying and firing can be reduced, and the power required for the drying and firing treatment in the drying and firing step (step S60) can be suppressed, and the manufacturing cost can be reduced.

  In this way, in the drying and firing step (step S60), the gas diffusion layer precursor 50 impregnated with the water-repellent resin 31 is dried and fired, whereby the moisture and the dispersant in the gas diffusion layer precursor 50 are removed and the water repellent property is removed. The water repellency due to the aqueous resin 31 is expressed. Furthermore, when the water-repellent resin 31 is partially melted, it functions as a resin binder that binds the conductive fibers 11 and the conductive material 21, and the resulting gas diffusion layer 100 is strengthened.

  The order of drying and baking is not particularly limited, and drying and baking may be performed simultaneously. Also, the heat treatment for removing and dispersing the dispersing agent and the heat treatment for mainly binding by melting the water-repellent resin are changed, and the heat treatment is performed separately by changing the drying and firing temperature and time conditions. It is also possible.

Thus, the gas diffusion layer precursor 50 of the first embodiment is obtained by drying and firing the gas diffusion layer precursor 50.
The gas diffusion layer 100 according to the first embodiment thus obtained has a multilayer structure composed of the gas diffusion layer substrate 10 and the microporous layer 20 formed on one surface in the thickness direction of the gas diffusion layer substrate 10. Have.

  Here, the gas diffusion layer base material 10 according to the first embodiment has predetermined pores and is porous, so that moisture and gas permeability are ensured. Then, the first carbon precursor resin 14A is carbonized and graphitized at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere, whereby the first carbon precursor resin 14A is carbonized and graphitized. Conductive fibers 11 are bound by resin carbide. Thus, since the conductive fiber 11 is bound to the resin carbide, a conductive path is formed and has high conductivity and strength. In addition, since the conductive fibers 11 are bound with resin carbide, the conductive fibers 11 have elasticity and the like, and have high dimensional absorbability when joined to the electrolyte membrane 120 in application to the fuel cell 200. Furthermore, by making the paper together with the binder 12 at the time of making the conductive fiber 11, the bonding property, the entanglement property, and the contact property of the conductive fiber 11 are improved, and the shape retaining property and strength are high. , Peeling is difficult to occur and the fixing property of the conductive fiber 11 is high. Furthermore, the binder 12 disappears by heating in the carbonization / graphitization step (step S40), and the disappeared traces become voids, so that the void ratio (pore) and the pore diameter are improved, and moisture and gas permeability are improved. Enhanced. In addition, the gap and permeability can be easily controlled by the blending amount, type, size, and the like of the binder 12.

  Also, in the microporous layer 20 of the first embodiment, micropores smaller than the voids (pores) of the gas diffusion layer base material 10 are formed and porous, and moisture and gas permeability are ensured. Yes. In particular, the base material precursor 15 before the carbonization / graphitization is coated with a paste-like coating liquid 24 containing the conductive material 21 for forming the microporous layer 20 and the second carbon precursor resin 14B, to thereby form the base material precursor. The microporous layer precursor 25 formed on the base material precursor 15 together with the body 15 was baked under predetermined heating conditions in the carbonization / graphitization step (step S40), so that it was 1000 in a non-oxidizing atmosphere. The second carbon precursor resin 14B is carbonized and graphitized at a temperature of ˜3500 ° C., and the conductive material 21 is bound by a resin carbide formed by carbonizing and graphitizing the second carbon precursor resin 14B. Yes. In this way, the conductive material 21 is bonded to the resin carbide, so that a conductive path is formed, and it has high conductivity and layer strength and is strong. Further, the conductive material 21 in the microporous layer precursor 25 is bound by the resin carbide obtained by carbonizing the second carbon precursor resin 14B in this way, so that the conductive material 21 is removed and peeled off. Is unlikely to occur. Therefore, the handleability is good, the smoothness at the contact surface with the catalyst layer 110 is maintained during assembly to the fuel cell 200 and use, and the possibility of a decrease in power generation efficiency and short circuit due to an increase in contact resistance is reduced.

Further, after the assembly to the fuel cell 200, even if an external force is applied due to, for example, expansion or contraction of the electrolyte membrane 120 due to the operation of the fuel cell 200, or due to the sandwiching pressure of the separator at the time of stacking, etc. The conductive material 21 of the layer 20 is not easily lost (peeled). Therefore, the durability is high, and the conductive material 21 does not flow and does not block the pores of the gas diffusion layer base material 10 and the gas flow path 141, and may cause clogging that causes a decrease in output. Absent. Therefore, the performance of the fuel cell 200 can be stabilized.
Thus, the microporous layer 20 of the first embodiment has high reliability and durability. In addition, since the conductive material 21 is bound with resin carbide, it has elasticity and the like, and has high dimensional absorbability when bonded to the electrolyte membrane 120 when applied to the fuel cell 200. In addition, the resin carbide formed by carbonizing the second carbon precursor resin 14B binds the conductive material 21, so that the microporous layer 20 is appropriately hardened. Even if it is sandwiched, the pores of the microporous layer 20 are hardly crushed and held, and stable performance such as gas diffusibility and drainage can be ensured.

  In particular, in the first embodiment, a paste-like coating liquid 24 for forming the microporous layer 20 is applied to the base material precursor 15 before carbonization / graphitization, and the microporous layer precursor 25 is combined with the base material precursor 15. Is fired under a predetermined heating condition in the carbonization / graphitization step (step S40), and therefore, the conductive fiber 11 in the base material precursor 15 at the boundary between the base material precursor 15 and the microporous layer precursor 25. And the conductive material 12 in the microporous layer precursor 25 are bonded by a resin carbide obtained by carbonizing the first carbon precursor resin 14A, so that the gas diffusion layer substrate 10 and the microporous layer 20 The integral bonding strength is high, and the fixing power of the microporous layer 20 to the gas diffusion layer substrate 10 is high. Further, the formation of a conductive path made of a resin carbide obtained by carbonizing the first carbon precursor resin 14A reduces contact resistance between the gas diffusion layer base material 10 and the microporous layer 20, which is advantageous for current collection.

  Furthermore, since the second carbon precursor resin 14B is blended in the paste-like coating liquid 24 for forming the microporous layer 20, the substrate precursor is also formed by a resin carbide obtained by carbonizing the second carbon precursor resin 14B. Since the conductive fiber 11 in the body 15 and the conductive material 21 in the microporous layer precursor 25 are bound, the bond between the gas diffusion layer base material 10 and the microporous layer 20 is increased. For this reason, the microporous layer 20 is difficult to peel off from the gas diffusion layer base material 10, and the adhesion between the two is high, and the formation of the microporous layer 20 with desired characteristics and the high bondability between the gas diffusion layer base material 10 are ensured. Can do. Therefore, the microporous layer 20 is hardly peeled off from the gas diffusion layer base material 10 when assembled to the fuel cell 200 or used, and the fixing power of the microporous layer 20 to the gas diffusion layer base material 10 is improved. Further, the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 is further reduced by the formation of the conductive path by the resin carbide formed by carbonizing the second carbon precursor resin 14B, and the entire gas diffusion layer 10 is reduced. The conductivity can be increased and the current collecting function can be improved. That is, it is possible to reduce the electrical resistance, improve the current collecting property, and improve the performance of the fuel cell 200. As described above, since the conductive material 21 forming the microporous layer 20 is not easily dropped, missing, or peeled off, it is possible to prevent an increase in contact resistance or a short circuit when the fuel cell 200 is used. Is done. Therefore, when this gas diffusion layer 100 is used as the electrode 130 for the fuel cell 200, durability is high, stable battery performance is exhibited in the fuel cell 200, and high reliability is obtained.

  Further, a paste-like coating liquid 24 for forming the microporous layer 20 is applied to the substrate precursor 15 before carbonization / graphitization, and the microporous layer precursor 25 is carbonized and graphitized together with the substrate precursor 15 ( Since firing is performed at a predetermined high temperature condition in step S40), not only the substrate precursor 15 but also the microporous layer 20 can be made free of metal contamination (reduction of mixing of metals as impurities), conductivity, etc. The output of the fuel cell 200 can be stabilized. That is, even if the low-purity conductive material 21 is used, the purity is increased and homogenized by firing under a predetermined high temperature condition capable of carbonizing the first carbon precursor resin 14A and the second carbon precursor resin 14B. In addition, characteristics such as high conductivity can be secured. Preferably, high-temperature heating at 1500 ° C. or higher and 3000 ° C. or lower in the carbonization / graphitization step (step S40) is advantageous for reducing metal contamination.

  According to the gas diffusion layer 100 including the gas diffusion layer base material 10 and the microporous layer 20 formed on one surface in the thickness direction of the gas diffusion layer base material 10, the non-uniformity of the gas diffusion layer base material 10 is caused by the microporous layer 20. It is relaxed and a smooth surface is obtained at the contact surface with the catalyst layer 110. Even if the gas diffusion layer substrate 10 is frayed or fluffed, the conductive fibers 11 of the gas diffusion layer substrate 10 come into contact with the catalyst layer 110 or the electrolyte membrane 120 and damage the catalyst layer 110 or the electrolyte membrane 120. The occurrence of a short circuit caused by the conductive fibers 11 and the catalyst layer 110 of the gas diffusion layer base material 10 is prevented. Furthermore, since the microporous layer 20 is denser than the gas diffusion layer base material 10, the contact property with the catalyst layer 110 is increased, and the contact resistance is low, which is advantageous for current collection. In addition, since water generated by the battery reaction is subdivided by the microporous layer 20 and sent to the gas diffusion layer base material 10, the drainage performance is improved and the effect of preventing flooding is enhanced. Therefore, the battery performance is further stabilized. Further, by controlling the components of the microporous layer 20, it is possible to easily obtain controllability of performance according to the use environment and operating conditions of the battery, which is difficult only with the gas diffusion layer substrate 10 alone.

And in this Embodiment 1, the paste-form coating liquid 24 for microporous layer 20 formation is apply | coated to the base-material precursor 15 before carbonization and graphitization, and the base-material precursor 15 and the micro formed on it. Since the gas diffusion layer precursor 50 made of the porous layer precursor 25 is fired under a predetermined heating condition in the carbonization / graphitization step (step S40), the water-repellent resin 31 is impregnated, and then dried and fired. In the gas diffusion layer precursor 50 that is dried and fired after water treatment, the presence of a dispersant that inhibits water repellency is small, and the conductive property that was included in the pasty mixture for forming a microporous layer at the time of drying and firing. Removal of dispersants such as non-ionic surfactants to disperse materials and thickeners to prevent penetration (penetration) of paste mixture components into the gas diffusion layer substrate Necessary There. Therefore, the dispersant that inhibits water repellency is sufficiently decomposed and volatilized by drying and baking at a temperature lower than the temperature condition necessary for removing the dispersant in the conventional paste mixture for forming the microporous layer. It can be removed and high water repellency of the gas diffusion layer 100 can be secured. In addition, it is possible to shorten the time required for drying and baking for eliminating water and the dispersant and exhibiting water repellency, and further, it is possible to shorten the time for raising the temperature to a predetermined temperature in order to remove the moisture and the dispersant. The time required for the drying and firing process can be shortened.
That is, since sufficient water repellency is exhibited even by drying and baking under low temperature conditions, the temperature during drying and baking can be reduced, and the time in the drying and baking process (step S60) can be shortened.

  Thus, by reducing the temperature at the time of drying and baking, and by reducing the load of the drying and baking process by shortening the time at the time of drying and baking, the energy cost for the drying and baking process in the drying and baking process (step S60) can be reduced, Manufacturing cost can be reduced. In addition, the manufacturing cost can be suppressed by shortening the length of the drying and firing furnace by shortening the time required for drying and firing. Therefore, the cost of the gas diffusion layer 100 can be reduced. In addition, the production efficiency of the gas diffusion layer 100 can be increased by shortening the drying and baking time. Furthermore, since the emission amount of carbon dioxide can be reduced by reducing the energy cost, the load on the natural environment can be reduced.

  Thus, in the gas diffusion layer 100 of the first embodiment, the power generation efficiency of the fuel cell 200 is affected without remaining a dispersant that inhibits water repellency even after drying and baking under low temperature conditions. By ensuring the water repellency to be given, the water generated by the battery reaction is smoothly discharged, and the flatting phenomenon is prevented. That is, high water repellency can be obtained even if the load during drying and firing is reduced, and the fuel cell 200 can maintain stable output and battery performance over a long period of time. In addition, since the drying and firing temperature necessary for the expression of water repellency can be lowered, the components of the gas diffusion layer 100 are deteriorated or weakened due to high-temperature oxidation heating or overheating, and the occurrence or deformation of cracks in the gas diffusion layer 100 is caused. As a result, the smoothness of the gas diffusion layer 100 can be prevented from being lowered.

Further, the water-repellent resin 31 impregnated in the carbonized / graphitized base precursor 15 and the water-repellent resin 31 impregnated in the microporous layer precursor 25 after carbonized / graphitized by heating during drying and firing are provided. By melting, the conductive fibers 11 in the base material precursor 15 are bound together by the melted water-repellent resin 31, or the conductive materials 21 in the microporous layer precursor 25 are bound together. The conductive fiber 11 and the conductive material 21 are bound, and the mechanical strength of the entire gas diffusion layer 10 and the bonding strength of the gas diffusion layer 10 and the microporous layer 20 are increased. And the falling off of the conductive material 21 is prevented.
In particular, in the first embodiment, since the drying and firing temperature can be lowered, thermal decomposition of the water-repellent resin 31 is suppressed, and a high binding force by the melted water-repellent resin 31 is obtained. Furthermore, since the dispersant does not remain in the gas diffusion layer 100 obtained by sufficiently removing the dispersant present in the gas diffusion layer base material 50 even under a low temperature condition of drying and baking, the conductive property of the water-repellent resin 31 is reduced by the dispersant. The binding of the conductive fiber 11 and the conductive material 21 is not hindered.
In the first embodiment, the second carbon precursor resin 14B is carbonized by blending the second carbon precursor resin 14B with the paste-like coating liquid 24 even if the drying and firing temperature is lowered. By the binding with the resin carbide thus formed, the mechanical strength and bonding strength of the gas diffusion layer base material 10 and the microporous layer 20 are increased, and the fixing property of the conductive fibers 11 and the conductive material 21 is increased.

  Thus, the gas diffusion layer 100 of the first embodiment has high fixability of the conductive fibers 11 and the conductive material 21, maintains water repellency, and is advantageous for current collection. Can be made uniform and used as the electrode 130 for the fuel cell 200, the electrical resistance can be reduced, the current collecting performance can be improved, and the performance of the fuel cell 200 can be improved. Furthermore, the characteristics at the time of high load are excellent, and the stable diffusivity of the reaction gas is maintained without lowering the utilization rate of the reaction gas. Therefore, the fuel cell 200 can maintain a stable output for a long time, It is possible to quickly follow the increase in required power generation amount and to exhibit high battery performance. Therefore, the membrane electrode assembly 150 of the polymer electrolyte fuel cell that can operate stably for a long period of time and requires high reaction activity can be suitably used.

  In addition, conventionally, when applying a paste material mixture for forming a microporous layer in which a conductive material, a water-repellent resin, and a large amount of a dispersant are dispersed to disperse the carbonized gas diffusion layer base material 10, The component of the paste mixture for forming the microporous layer is prevented from soaking (penetrating) into the porous gas diffusion layer base material 10 having pores, and the paste mixture component component on the surface of the gas diffusion layer base material 10 is further prevented. For fixing, the gas diffusion layer base material 10 was impregnated with a water-repellent resin, the moisture was dried, and then the microporous layer-forming paste-like mixture was applied, followed by drying and firing. However, in the present first embodiment, the microporous layer 20 is formed on the base precursor 15 before carbonization / graphitization to which the first carbon precursor resin 14A is attached by the impregnation of the first carbon precursor resin 14A. Since the paste-like coating liquid 24 is applied, as described above, the base material precursor 15 has few voids, and the first carbon precursor resin 14A is held (filled). Even if the paste-like coating liquid 24 is applied to the substrate precursor 15 without performing the water-repellent treatment or the drying process before the paste-like coating liquid 24 is applied, the paste-like coating liquid is applied to the surface of the substrate precursor 15. 24 components can be fixed. Therefore, the workability and manufacturing process of manufacturing can be simplified and the manufacturing cost can be reduced.

Next, the gas diffusion layer 100 according to Embodiment 1 of the present invention will be described with reference to examples.
Table 1 shows the compounding materials used in the manufacture of the gas diffusion layer 100 of this example.

  The manufacturing method of the gas diffusion layer 100 according to the present embodiment will be described. According to the flowchart of FIG. 2, the carbon fiber (short fiber; average fiber diameter 0.1 to 50 μm, average fiber length 0.01) as the conductive fiber 11. To 50 mm) and polyvinyl alcohol (PVA) fibers as the binder 12 are mixed with water as a dispersion medium (papermaking medium), and beaten in water using an appropriate papermaking reagent, so that the carbon fiber 11 and the PVA are mixed. Fiber 12 was dispersed in water. In addition, water was 98.0-99.9 weight part with respect to a total of 100 weight part of carbon fiber and PVA fiber. Subsequently, the resulting carbon fiber 11, PVA fiber 12, and water mixture was subjected to paper making using a mesh member, and the paper making process (step S11) was performed.

Papermaking is carried out by supplying the above mixture to the upper surface of a mesh member (stainless steel (SUS316, 65-80 mesh) or plastic) and subjecting the mixture to vacuum dehydration using a vacuum dehydrator placed at the bottom of the mesh member. A method of separating the contained liquid component (water as a dispersion medium) from the solid component (carbon fiber 11 and PVA fiber 12) and depositing the solid component (carbon fiber 11 and PVA fiber 12) on the upper surface of the mesh member. I went there.
As a result, a sheet-like (paper-like) papermaking substrate 13 having a basis weight (weighing) of the carbon fiber 11 of 25 g / m ² was obtained. The papermaking substrate 13 thus obtained is a sheet-like aggregate of carbon fibers 11 and PVA fibers 12.

Next, a carbon precursor resin impregnation step (step S12) was performed in which the sheet-like paper base material 13 obtained in the paper making step (step S11) was impregnated with a phenol resin as the first carbon precursor resin 14A. .
Specifically, a sheet-like papermaking substrate 13 is immersed in a phenolic resin dispersion (diluent) in which a phenolic resin as the first carbon precursor resin 14A is dispersed in methanol. The material 13 was impregnated with a phenol resin as the first carbon precursor resin 14A. The phenol resin as the first carbon precursor resin 14A was adjusted so that the impregnation amount (adhesion amount) of the resin (solid content) after impregnation into the sheet-shaped papermaking substrate 13 was 7 g / m ² .
As a result, a gas diffusion layer base material precursor 15 in which a phenol resin 14 was adhered to a sheet-like papermaking base material 13 composed of the carbon fibers 11 and the PVA fibers 12 was obtained.

  That is, the carbon fiber as the conductive fiber 11 and the PVA fiber as the binder 12 by performing the base material precursor forming step (step S10) including the paper making step (step S11) and the carbon precursor resin impregnation step (step S12). Are made of paper, and a base material precursor 15 containing a phenol resin as the first carbon precursor resin 14A is formed.

  Furthermore, in the present Example, the shaping | molding process (step S20) which smoothes the front and back of the thickness direction of the base material precursor 15 by calendar shaping | molding was implemented.

  Subsequently, 100 g of carbon powder as the conductive material 21 and 50 g of phenol resin as the second carbon precursor resin 14B are mixed and dispersed in 300 g of methanol as the dispersion medium 23 to form a paste-like coating for forming the microporous layer 20. Liquid 24 was produced. Then, by performing the gas diffusion layer precursor forming step (step S30) in which the paste-like coating liquid 24 is applied to one side in the thickness direction of the base material precursor 15, conductivity is applied to one side of the base material precursor 15. A microporous layer precursor 25 containing carbon powder as the material 21 and a phenol resin as the second carbon precursor resin 14B is formed, and a gas diffusion layer precursor comprising the base material precursor 15 and the microporous layer precursor 25 A body 50 was obtained.

In this embodiment, the paste-like coating liquid 24 is applied to the substrate precursor 15 by a reverse coater method. In the gas diffusion layer precursor 50 in which the paste-like coating liquid 24 is applied to the substrate precursor 15, The coating amount was adjusted such that the carbon powder as the conductive material 21 and the phenol resin as the second carbon precursor resin 14B contained in the paste-like coating liquid 24 were 25 g / m ^{2 in} terms of solid content.

  Next, a carbonization / graphitization step (step S40) is performed in which the obtained gas diffusion layer precursor 50 is heated and fired in a nitrogen gas atmosphere in a heating and firing furnace set at 2000 ° C. for 1 hour. The phenol resin as the first carbon precursor resin 14A and the phenol resin as the second carbon precursor resin 14B in the precursor 50 were carbonized.

Subsequently, 26 g of an emulsion of PTFE resin as a water-repellent resin 31 (manufactured by Daikin Industries, Ltd .: POLYFLON PTFE D-210C [solid content (resin content) 61%]) was diluted with 500 g of water to repel the water-repellent resin 31. The carbonized gas diffusion layer precursor 50 is immersed in the water-repellent resin 31 dispersion to impregnate the carbonized gas diffusion layer precursor 50 with the water-repellent resin 31. An aqueous resin impregnation step (step S50) was performed. The blending amount of the PTFE resin (solid content) as the water repellent resin 31 at this time was adjusted so that the resin (solid content) impregnation amount (adhesion amount) after drying and firing was 7 g / m ² .
This PTFE emulsion (Daikin Kogyo Co., Ltd .: POLYFLON PTFE D-210C [solid content (resin content) 61%]) has a nonionic surfactant (dispersant) for stabilizing PTFE fine particles. About 6 mass% / P (conforming to JIS K 6893).

And the drying baking process (step S60) which dry-fires the gas diffusion layer precursor 50 impregnated with the PTFE resin as the water repellent resin 31 at 250 ° C. for 5 minutes (250 ° C. × 5 minutes) was performed.
Thus, gas diffusion layers 100 according to Examples 1 to 10 including the gas diffusion layer base material 10 and the microporous layer 20 were obtained.

The compounding materials used in the manufacture of the gas diffusion layers 100 of Examples 1 to 10 are as shown in Table 1.
Here, with respect to Examples 1 to 10, only the content of the conductive material 21 blended in the paste-like coating liquid 24 for forming the microporous layer 20 is different, and all other blended materials are unified. Yes. Specifically, as shown in Table 1 and Table 2 below, for Examples 1 to 5, carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd.) is used as the conductive material 21 to be blended in the paste-like coating liquid 24. : Trade name “Denka Black (registered trademark)”), and only the particle size of carbon black is different between Examples 1 to 5. Moreover, about Example 6 thru | or Example 10, graphite is used for the electroconductive material 21 mix | blended with the paste-form coating liquid 24, and only the particle diameter of graphite differs between Examples 6 thru | or Example 10. .

As shown in Table 2, carbon black having a median diameter of 30 nm was used in Example 1 as the conductive material 21 to be blended in the paste-like coating liquid 24, and the median diameter was 50 nm in Example 2. In Example 3, carbon black with a median diameter of 100 nm is used, in Example 4, carbon black with a median diameter of 20 nm is used, and in Example 5, the particle diameter is Carbon black with a median diameter of 200 nm was used.
In Example 6, graphite having a median diameter of 3 μm is used, in Example 7, graphite having a median diameter of 5 μm is used, and in Example 8, graphite having a median diameter of 20 μm is used. In Example 9, graphite having a median diameter of 1 μm was used, and in Example 10, graphite having a median diameter of 50 μm was used.

For comparison, gas diffusion layers 100 according to Comparative Example 1 and Comparative Example 2 were prepared by a conventional manufacturing method.
In Comparative Example 1 and Comparative Example 2, a base material precursor forming process (step S11) comprising a paper making process (step S11) and a carbon precursor resin impregnation process (step S12) according to the flowchart of FIG. 4 showing a conventional manufacturing process. Although it is the same as that of an Example until S10), the paste-form coating liquid 24 is apply | coated with respect to the base material precursor 15 obtained through the papermaking process (step S11) and the carbon precursor resin impregnation process (step S12). Without performing the molding step (step S20) and the carbonization / graphitization step (step S40). The conditions for the molding step (step S20) and the carbonization / graphitization step (step S40) were the same as in the above example. That is, a base material precursor 15 in which a phenolic resin 14 is adhered to a sheet-shaped paper base material 13 composed of carbon fibers 11 and PVA fibers 12 is calendered and then heated and fired at 2000 ° C. in a nitrogen atmosphere. Was carbonized.

Subsequently, the microporous layer-shaped paste mixture 27 to be applied later is prevented from penetrating into the base material precursor 15 after carbonization, and the water repellency for ensuring the water repellency of the gas diffusion layer base material 10 is ensured. A water-repellent resin 31a dispersion was prepared by diluting 26 g of PTFE resin emulsion (produced by Daikin Industries, Ltd .: POLYFLON PTFE D-210C [solid content (resin content) 61%)) with 500 g of water as the aqueous resin 31a. Then, the substrate precursor 15 carbonized in the carbonization / graphitization step (step S40) is immersed in the dispersion of the water-repellent resin 31a, thereby making the substrate precursor 15 after carbonization water-repellent. A water repellent resin impregnation step (step S50) for impregnating the PTFE resin as the resin 31a was performed. The blending amount of the PTFE resin (solid content) as the water-repellent resin 31a at this time was adjusted so that the resin (solid content) impregnation amount (adhesion amount) after moisture drying was 3 g / m ² .

Then, after drying the substrate precursor 15 impregnated with the PTFE resin as the water repellent resin 31a to evaporate the moisture in the substrate precursor 15, the carbonization impregnated with the PTFE resin as the water repellent resin 31a. Carbon black (acetylene black) as a conductive material 21 (manufactured by Denki Kagaku Kogyo Co., Ltd .: trade name “Denka Black (registered trademark)”) on one side in the thickness direction of the subsequent substrate precursor 15. 60 g, 75 g of an emulsion of PTFE resin (manufactured by Daikin Industries, Ltd .: POLYFLON PTFE D-210C [solid content (resin content) 61%]) as the water-repellent resin 31b for ensuring the water repellency of the microporous layer 20; In Comparative Example 1 and Comparative Example 2 in which 7 g of nonionic surfactant (dispersant) and 185 g of ion-exchanged water as the dispersion medium 23 are mixed and dispersed. That was a paste-like mixture 27 for microporous layer forms performed thin coating tool (die head) Gas diffusion layer precursor forming step applied using (step S30).
Then, the gas diffusion layer 100 which concerns on the comparative example 1 and the comparative example 2 which consist of the gas diffusion layer base material 10 and the microporous layer 20 was produced by implementation of the drying baking process (step S60) which dry-fires the whole.

In addition, in the paste mixture 27 for microporous layer shape according to Comparative Example 1 and Comparative Example 2, a planetary agitation / defoaming apparatus (manufactured by Kurashiki Boseki Co., Ltd .: trade name “Mazerustar” set to revolution 800 rpm and autorotation 900 rpm. KK-1000W ") for 3 minutes, and the mixture is dispersed and degassed. In the coating film after application to the substrate precursor 15, carbon powder as the conductive material 21 and PTFE as the water repellent resin 31 are prepared. The coating amount was adjusted so that the resin was 30 g / m ^{2 in} terms of solid content.
As a precaution, the compounding materials used in the manufacture of the gas diffusion layers 100 of Comparative Example 1 and Comparative Example 2 are shown in Table 3.

  Here, in Comparative Example 1 and Comparative Example 2, only the heating temperature conditions in the drying and firing step (step S60) were changed, and the other manufacturing conditions were all the same. That is, in Comparative Example 1, the drying and baking temperature condition was set to 360 ° C., and drying and baking were performed at 360 ° C. for 5 minutes. On the other hand, in Comparative Example 2, the temperature condition for drying and baking was set to 250 ° C., which was the same as in Examples 1 to 10, and drying and baking was performed at 250 ° C. for 5 minutes.

  And about the gas diffusion layer 100 of Example 1 thru | or Example 10, Comparative Example 1 and Comparative Example 2 which were produced in this way, the characteristic evaluation test was done. Evaluation items were dispersibility, applicability, smoothness, water repellency, air permeability, and resistance.

Regarding dispersibility, in Examples 1 to 10, the dispersion state of the components of the paste-like coating liquid 24 for forming the microporous layer 20, that is, carbon black or graphite carbon powder as the conductive material 21, The dispersion state and sedimentation properties when a predetermined amount of the phenol resin as the carbon precursor resin 14B and methanol as the dispersion medium were mixed and dispersed were visually observed. In Comparative Example 1 and Comparative Example 2, the dispersion state of the components of the microporous layer-shaped paste mixture 27, that is, carbon black carbon powder as the conductive material 21, and PTFE resin as the water-repellent resin 31. And a planetary agitation / defoaming device (trade name “Mazerustar KK-1000W” manufactured by Kurashiki Boseki Co., Ltd.) in which a nonionic surfactant and ion-exchanged water are set at 800 rpm for revolution and 900 rpm for 3 minutes. The dispersion state and sedimentation when prepared by mixing and defoaming were visually observed.
For the paste-like coating liquid 24 according to Example 1 to Example 10 or the paste-like mixture 27 according to Comparative Example 1 and Comparative Example 2, the case where solid-liquid separation did not occur was evaluated as ◎, and could be sufficiently put into practical use. Although it was a thing, the thing which solid-liquid separation was seen slightly was evaluated as (circle).

Regarding the coating properties, in Examples 1 to 10, the flow characteristics of the paste-like coating liquid 24 when applied to the substrate precursor 15 by the reverse coater, and the paste-like coating liquid 24 is applied to the substrate precursor 15. The coating unevenness of the coating film (microporous layer precursor 25) formed on the substrate precursor 15 was visually observed. In Comparative Example 1 and Comparative Example 2, the flow characteristics of the paste mixture 27 and the coating unevenness of the coating film (microporous layer precursor 25) were visually observed when the paste mixture 27 was applied with a die head. .
The flow characteristics at the time of application are good and a case where a uniform film is formed is evaluated as ◎, and the film uniformity is at a satisfactory level, but the flow characteristics at the time of application are inferior, and the coating amount tends to vary. For this reason, a product whose productivity was lowered in order to maintain the uniformity of the film was evaluated as ◯.

  The smoothness was evaluated by evaluating the film thickness uniformity of the produced gas diffusion layer 100. Specifically, the film thickness at the end and center of the shape of the gas diffusion layer 100 produced was measured with a digital dial gauge at a pressure of 0.1 MPa, and each of the measured film thicknesses at five or more points was measured. However, if the average film thickness is less than ± 10%, it is judged that the smoothness is excellent, and the evaluation is ◎◎, and if the average film thickness exceeds ± 10% but is ± 20% or less The smoothness was good and evaluated as “◎”, and those exceeding ± 20% and less than 30% with respect to the average film thickness were judged to be sufficiently practical enough to be evaluated as “good”.

  For water repellency, the gas diffusion layer 100 is set up perpendicularly to the horizontal plane, and 3 g of ion-exchanged water is sprayed on the opposite front and back surfaces in the thickness direction of the gas diffusion layer 100 by spraying five times, and water drops fall. The test of whether or not to do was conducted. For water drops that did not remain on the front and back surfaces of the gas diffusion layer 100, the water repellency was judged good and evaluated as ◎, and the water droplets remained attached to the front and back surfaces of the gas diffusion layer 100. About what was, it judged that it was unsuitable for practical use because water repellency was insufficient, and was evaluated as x.

Regarding the air permeability, the gas diffusion layer 100 is used as a test apparatus so that one side in the thickness direction of the gas diffusion layer 100 punched out to 50Φ is a pressure chamber and the other side in the thickness direction of the gas diffusion layer 100 is an open chamber. In the pressure chamber on one side in the thickness direction of the gas diffusion layer 100, 0.5 L / min, 0 under a load of 1260 N (surface pressure of 1.8 MPa) (load measuring device (WGA-710B): Kyowa Sangyo Co., Ltd.) .7 L / min, 0.9 L / min nitrogen gas (flow rate controller (PAC-D2): Horiba ESTEC Co., Ltd.) is supplied, and the pressure difference from the open chamber (differential pressure gauge (GPG-204C11): Co., Ltd. Okano Manufacturing Co., Ltd.). If the average value of the gas permeability (normal permeability) calculated from the gradient of the differential pressure is 2.0 [1.0 × 10 ⁻⁶ m / (Pa · Sec)] or more, the gas permeability Judged that the properties were good, evaluated as ◎, and for 1.0 or more and less than 2.0, the gas permeability was at a satisfactory level, so it was judged that it was sufficiently practical and evaluated as ◯. .

With respect to the resistance value, the gas diffusion layer 14 is sandwiched between blocks made of beryllium copper, and a current of 1080 N is applied (surface pressure 1 MPa) (load measuring device (K3HB-VLC-C2BT11): OMRON Corporation). (1A × 1-5 MPa), and the electric resistance in the thickness direction per unit area of the gas diffusion layer 14 (resistance meter (3566): Tsuruga Electric Co., Ltd.) was measured. If the measured value [mΩ · cm ² ] of electrical resistance (average value) is 15 or less, the electrical conductivity is judged to be good and evaluated as ◎, and if it exceeds 15 and less than 20, the electrical conductivity is satisfactory. Since it was in the level which can be performed, it judged that it was able to endure practically enough and evaluated as (circle).

Furthermore, in addition to these evaluation items, taking into account the temperature conditions for drying and firing, in addition to being an evaluation of ◎◎ or ◎ for all of dispersibility, coatability, smoothness, air permeability, and resistance value, the drying and firing step The temperature at the time of drying and baking in (Step S60) is 250 ° C., that is, lower than the temperature condition (300 to 360 ° C.) at the time of drying and baking performed after application of the conventional paste mixture 27 for forming the microporous layer, Those having water repellency of ◎ and capable of exhibiting high water repellency were evaluated as ◎ in the overall evaluation because the energy cost was suppressed. In addition, it is sufficient that the temperature condition at the time of drying and baking is 250 ° C. and the water repellency is evaluated as ◎ and any of dispersibility, applicability, smoothness, air permeability, and resistance value is evaluated as ○ Since it can withstand practical use, it is considered to be acceptable, and it is evaluated as “Good” in the overall judgment. On the other hand, although the temperature condition of drying and baking is 250 ° C., the water cost is an evaluation of x that is not suitable for practical use, or the temperature condition of heating and drying is high (360 ° C.), and the energy cost for drying and baking is low. About what is not suppressed, it becomes evaluation of x by comprehensive determination.
The evaluation results of each evaluation item are as shown in the right orchid of Table 2.

As shown in Table 2, in Comparative Example 1 produced by the conventional production method, although sufficient water repellency can be obtained, the overall evaluation is x because the temperature condition for drying and baking is high. On the other hand, in Comparative Example 2, the temperature condition for drying and firing was set to a low temperature condition as in the example, but as a result, the dispersant was not sufficiently removed and the water repellency was greatly reduced, and the results were not practical. The overall evaluation is x.
In the conventional manufacturing method from Comparative Example 1 and Comparative Example 2, in order to obtain high water repellency in the gas diffusion layer 100, drying and firing at a high temperature that sufficiently removes the dispersant that inhibits water repellency is necessary. It can be said that there is.

On the other hand, in Examples 1 to 10, although the temperature condition for drying and baking is lower than the conventional temperature condition (300 to 360 ° C.) (250 ° C.), the dispersibility, the coatability, and the smoothness The water repellency, air permeability, and resistance values are all evaluated as ◎, ◎, or ○, and evaluated as ◎ or で in the overall judgment.
In the production methods of Examples 1 to 10, the drying and baking temperature conditions were lower than the conventional temperature conditions (300 to 360 ° C.) but high water repellency was obtained. A paste-like coating liquid 24 for forming the microporous layer 20 is applied to the base material precursor 15 before carbonization, and both the base material precursor 15 and the microporous layer precursor 25 are carbonized. This is because only the impregnation of the resin 31 is performed and subjected to drying and baking, so that the gas diffusion layer precursor 50 to be dried and sintered contains a small amount of a component of a dispersant that inhibits water repellency. As a result, even when the temperature for drying and baking is low, the component of the dispersant that inhibits water repellency is sufficiently decomposed and removed, so that high water repellency is exhibited.

  In particular, Examples 1 to 3 in which carbon black having a median diameter of 30 nm to 100 nm is used as the conductive material 21 to be blended in the paste-like coating liquid 24, and the median diameter is 3 μm to 20 μm. In Examples 6 to 8 using the above graphite, all of dispersibility, coatability, smoothness, water repellency, air permeability, and resistance value were evaluated as ◎◎ or In addition, the water repellency, gas and moisture permeability, and conductivity required for the gas diffusion layer 100 were excellent. In addition, the dispersibility is good without adding a dispersant to the paste-like coating liquid 24, and there is no solid-liquid separation, so that the preservability is good, the coating efficiency is also good, and the smoothness of the microporous layer 20 is achieved. It was also excellent. Therefore, when applied to the fuel cell 200, the characteristics of the gas diffusion layer 100 are effectively expressed and a high output can be stably obtained.

  Further, as the conductive material 21 to be blended in the paste-like coating liquid 24, Example 4 in which carbon black having the smallest particle diameter among Examples 1 to 5 using carbon black and having a median diameter of 20 nm is used. Then, a high water repellency (）) is obtained at a temperature (250 ° C.) lower than the conventional temperature condition (300 to 360 ° C.), and the dispersibility, coatability, smoothness, and resistance value are also obtained. Although it was evaluated as 、, the air permeability was evaluated as ◯. That is, it was found that when carbon black is used as the conductive material 21 to be blended in the paste-like coating liquid 24, the gas permeability of the gas diffusion layer 100 is lowered when the median diameter of the carbon black is less than 30 nm. . However, even if the evaluation is ◯, the air permeability is satisfactory, so that it can sufficiently withstand practical use.

  On the other hand, as the conductive material 21 to be blended in the paste-like coating liquid 24, Example 5 using carbon black having the largest particle diameter among Examples 1 to 5 using carbon black and having a median diameter of 200 nm. Then, high water repellency (（) is obtained when the temperature condition of the drying and firing is lower than the conventional temperature condition (300 to 360 ° C) (250 ° C), and the air permeability and resistance value are evaluated as ◎. Also, the dispersibility, coating property, and smoothness were evaluated as “Good”. That is, when carbon black is used as the conductive material 21 to be blended in the paste-like coating liquid 24, when the median diameter of the carbon black exceeds 100 nm, dispersibility, applicability, and smoothness may decrease. found. However, even if the evaluation is ○, the dispersibility, coatability and smoothness are satisfactory levels, so that they can sufficiently withstand practical use.

  Furthermore, in Example 9 using graphite having a median diameter of 1 μm, which is the smallest among Examples 6 to 10 using graphite as the conductive material 21 blended in the paste-like coating liquid 24, High water repellency (◎) is obtained when the temperature condition of drying and baking is lower than the conventional temperature condition (300 to 360 ° C) (250 ° C), and the resistance value is also evaluated as ◎, dispersibility, coating The property, smoothness and air permeability were evaluated as “Good”. That is, when graphite is used as the conductive material 21 to be blended in the paste-like coating liquid 24, if the median diameter of the graphite is less than 3 μm, dispersibility, coatability, smoothness, and air permeability may decrease. found. However, even if the evaluation is ○, the dispersibility, coatability, smoothness, and air permeability are satisfactory levels, so that they can sufficiently withstand practical use.

  Further, as the conductive material 21 to be blended in the paste-like coating liquid 24, Example 10 using graphite having the largest particle diameter among Examples 6 to 10 using graphite and having a median diameter of 50 μm is used. Then, high water repellency (（) is obtained when the temperature condition of drying and baking is lower than the conventional temperature condition (300 to 360 ° C) (250 ° C), and the dispersibility and air permeability are also evaluated as ◎. Also, the applicability, smoothness and resistance value were evaluated as “Good”. That is, when graphite is used as the conductive material 21 to be blended in the paste-like coating liquid 24, it has been found that when the median diameter of graphite exceeds 20 μm, the coatability, smoothness, and resistance value decrease. However, even if the evaluation is good, the applicability, smoothness, and resistance value are satisfactory levels, so that they can sufficiently withstand practical use.

  Thus, from Example 1 to Example 5, when carbon black is used as the conductive material 21 of the paste-like coating liquid 24, if the particle size is too small, the gas permeability of the gas diffusion layer 100 decreases, On the other hand, if the particle size is too large, it has been found that the dispersibility, coatability and smoothness are lowered, and if the particle size of the carbon black is in the range of the median diameter of 20 nm or more and 200 nm or less, it is practical. Gas and moisture permeability are ensured, and practical dispersibility, applicability, and smoothness can be ensured. Preferably, as long as the median diameter is in the range of 30 nm or more and 100 nm or less, the dispersibility and applicability are high, so that long-term storage and production efficiency during coating are good. Moreover, since the smoothness of the microporous layer 20 is high, the adhesiveness with the catalyst layer 110 can be improved to reduce the contact resistance or prevent moisture from being stored between the catalyst layer 110 and the like. Furthermore, the gas and moisture permeability can be improved due to the high air permeability. Therefore, stable output improvement can be achieved in the fuel cell 200.

  Further, from Example 6 to Example 10, when graphite is used as the conductive material 21 of the paste-like coating liquid 24, if the particle size is too small, the dispersibility, applicability, smoothness and air permeability decrease. On the other hand, if the particle size is too large, it has been found that applicability, smoothness and conductivity are lowered. If the particle size of graphite is in the range of 1 to 50 μm, the practical gas can be used. In addition, water permeability and conductivity can be ensured, and practical dispersibility, applicability, and smoothness can be ensured. Preferably, when the median diameter is in the range of 3 μm or more and 20 μm or less, the dispersibility and applicability are high, so that long-term storage and production efficiency during coating are good. Moreover, since the smoothness of the microporous layer 20 is high, the adhesiveness with the catalyst layer 110 can be improved to reduce the contact resistance or prevent moisture from being stored between the catalyst layer 110 and the like. Further, the low resistance value can improve the conductivity, and the high air permeability can improve the permeability of gas and moisture. Therefore, stable output improvement can be achieved in the fuel cell 200.

  Thus, in Examples 1 to 10, it was confirmed that high water repellency was obtained even if the temperature condition during drying and firing was lowered. And since the temperature conditions at the time of drying and firing can be lowered, the energy cost at the time of drying and firing can be reduced, and the manufacturing cost can be suppressed. And since the energy consumption at the time of drying baking can be reduced, an environmental load can also be reduced.

In Comparative Example 1 and Comparative Example 2, which are conventional manufacturing procedures, the paste mixture 27 for forming the microporous layer is applied to the porous base material precursor 15 after carbonization. In order to fix the component 27 on the surface of the base material precursor 15 after carbonization, a water-repellent resin impregnation step (step S50) and drying are required before the paste-like mixture 27 is applied, and the paste-like mixture 27 The mixing of the dispersing agent which improves the dispersibility of the component and the stirring by high shear stress are required, and the manufacturing process and manufacturing operation are complicated.
On the other hand, in Examples 1 to 10, since the paste-like coating liquid 24 for forming the microporous layer 20 is applied to the base material precursor 15 before carbonization, the conventional complicated production is performed. No work is required and the manufacturing process can be simplified. In particular, since the phenolic resin that is the second carbon precursor resin 14B is blended in the paste-like coating liquid 24, the carbon that is the conductive material 21 without the blending of a dispersing agent or stirring by a high shear stress. The dispersibility of the particles is high, and good coatability and surface smoothness can be obtained.

  As described above, Examples 1 to 10 can simplify the manufacturing process, provide high water repellency even when the drying and firing load is reduced, and reduce the manufacturing cost. It is.

  As described above, the method of manufacturing the fuel cell gas diffusion layer 100 according to the first embodiment is a fuel cell including the gas diffusion layer base material 10 and the microporous layer 20 disposed on one surface in the thickness direction thereof. A gas diffusion layer base precursor 15 in which the conductive fibers 11 and the binder 12 are integrated by papermaking, and the first carbon precursor resin 14A is contained. With respect to the base material precursor formation process (step S10) to be formed and the base material precursor 15 formed in the base material precursor formation process (step S10), the conductive material 21 for forming the microporous layer 20 and the first A gas diffusion layer precursor forming step (step S30) for forming a gas diffusion layer precursor 50 by applying a paste-like coating liquid 24 containing two carbon precursor resins 14B, and a gas diffusion layer precursor 50 is heated and fired at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere to carbonize and graphitize the first carbon precursor resin 14A and the second carbon precursor resin 14B ( Step S40), a water-repellent resin impregnation step (Step S50) in which the gas diffusion layer precursor 50 after carbonization / graphitization is impregnated with the water-repellent resin 31, and the gas diffusion layer precursor 50 impregnated with the water-repellent resin 31. And a drying and baking step (step S60) for drying and baking.

  Thus, according to the fuel cell gas diffusion layer 100 of Embodiment 1 and the manufacturing method thereof, the conductive material 21 for forming the microporous layer 20 with respect to the base material precursor 15 before carbonization / graphitization. Is applied to form a gas diffusion layer precursor 50 composed of a substrate precursor 15 and a microporous layer precursor 25, and the microporous layer precursor 25 is carbonized together with the substrate precursor 15.・ Graphitize. Since the gas diffusion layer precursor 50 is only impregnated with the water-repellent resin 31 after carbonization / graphitization, the gas diffusion layer precursor 50 that is dried and fired after the water-repellent treatment impedes water repellency. Low content of dispersant. In particular, the paste-like coating liquid 24 containing the conductive material 21 for forming the microporous layer 20 is applied to the substrate precursor 15 before carbonization / graphitization, and the carbonization / graphitization step (step) after the coating is applied. Since S40) is performed, even when the paste-like coating liquid 24 containing the conductive material 21 contains a dispersant, the dispersant at that time is a carbonization / graphitization step in which high-temperature heat treatment is performed (step S40). Disappears. Accordingly, in the drying and firing step (step S60) after the water repellent treatment, a nonionic surfactant or the like for dispersing the conductive material contained in the pasty mixture 27 for forming the microporous layer as in the past is used. There is no need to remove the dispersant. Therefore, high water repellency can be ensured without drying and firing at a lower temperature than before, without the dispersant in the gas diffusion layer precursor 50 being sufficiently removed and remaining. In addition, the time required for the drying and firing treatment can be shortened.

Conventionally, since the paste mixture 27 for forming the microporous layer is applied to a porous base material that has been subjected to a high temperature treatment, the paste-like mixture 27 soaks (permeates) into the porous base material. In order to prevent and prevent the components of the paste-like mixture 27 from being fixed on the surface of the porous base material, the porous base material is impregnated with the water-repellent resin 31a and the moisture is dried. It was necessary to apply, or it was necessary to mix a thickener with the paste-like mixture 27 to increase the viscosity, and the manufacturing process and manufacturing work were complicated.
On the other hand, in the method for manufacturing the fuel cell gas diffusion layer 100 of the first embodiment, the first carbon precursor resin 14A is attached by the impregnation of the first carbon precursor resin 14A before carbonization / graphitization. The base precursor 15 is coated with a paste-like coating liquid 24 for forming the microporous layer 20, and the base precursor 15 has few voids and is retained by the first carbon precursor resin 14A ( Filling). Therefore, the paste-like coating liquid 24 to the substrate precursor 15 can be obtained without performing water-repellent treatment or drying before applying the paste-like coating liquid 24, or without adjusting the viscosity of the paste-like coating liquid 24. The components of the paste-like coating liquid 24 can be fixed on the surface of the base material precursor 15 by coating. Therefore, the manufacturing process and manufacturing workability can be simplified.

  In addition, in the conventional manufacturing method, for example, even when pores are formed by disappearance of the pore forming agent in the microporous layer 20, a heating step for heating and eliminating the pore forming agent is separately provided, or heating in the drying and firing step is performed. There is a need to increase the firing temperature and the energy cost is inevitably increased. That is, in the conventional manufacturing method, it is necessary to provide a high-temperature firing step after applying the paste-like mixture 27 to a carbonized / graphitized porous substrate. However, in the production method of the present invention, the paste-like coating liquid 24 is applied to the substrate precursor 15 before carbonization / graphitization, and the substrate precursor 15 and the microparticles together with the substrate precursor 15 in the carbonization / graphitization step (step S40). Since the porous layer 20 is also fired at a high temperature, the manufacturing process can be simplified and energy costs can be saved.

  As described above, the time required for drying and baking can be shortened and the temperature can be reduced, and the workability of the production and the production process can be simplified, so that the production cost can be reduced and the environmental load can be reduced.

  In addition, the microporous layer precursor 25 is fired at a high temperature together with the substrate precursor 15, and the first carbon precursor resin 14 </ b> A in the substrate precursor 15 is carbonized, whereby the first carbon precursor resin. The conductive carbide 11 of the base material precursor 15 and the conductive material 21 of the microporous layer precursor 25 are bound at the boundary between the base material precursor 15 and the microporous layer precursor 25 by the resin carbide formed by carbonizing 14A. Therefore, even when the amount of the binding component due to the water-repellent resin 31 is reduced by reducing the heat drying load, the substrate precursor 15 and the microporous layer precursor 25 are strongly bonded. Therefore, the microporous layer 20 is not easily peeled from the gas diffusion layer base material 10, and the integral bonding strength between the microporous layer 20 and the gas diffusion layer base material 10 is high. In addition, the conductive fibers 11 of the base material precursor 15 and the conductive material 21 of the microporous layer precursor 25 are bound at the boundary between the base material precursor 15 and the microporous layer precursor 25, so that the microporous material is bonded. The contact resistance between the layer 20 and the gas diffusion layer substrate 10 is also small, and the conductivity of the entire gas diffusion layer 100 can be improved. In addition, in the case where the paste-like coating liquid 24 is applied to the substrate precursor 15 before carbonization / graphitization, the component of the paste-like coating liquid 24 can be appropriately fixed on the surface layer portion of the substrate precursor 15. Bondability of the porous layer 20 and the gas diffusion layer base material 10 can be further enhanced.

  Furthermore, since the microporous layer precursor 25 is fired at a high temperature together with the base material precursor 15 in this way, there are few impurities in the microporous layer 20 and the corrosion resistance is excellent. Accordingly, it is possible to prevent the performance of the electrolyte membrane 120 from being deteriorated by metal ions.

In this way, the manufacturing process can be simplified, a high water repellency can be obtained even if the load of heat drying is reduced, and the manufacturing method of the gas diffusion layer 100 can be reduced in manufacturing cost and environmental load. .

  In particular, in the method of manufacturing the fuel cell gas diffusion layer 100 of the first embodiment, in the water repellent resin impregnation step (step S50), the PEFE resin emulsion as the water repellent resin 31 is carbonized and graphitized after graphitization. When the layer precursor 50 is impregnated, the water repellency can be sufficiently expressed if the temperature at which the gas diffusion layer precursor 50 is dried and fired in the drying and firing step (step S60) is in the range of 200 to 250 ° C. Therefore, the electric power required for drying and firing is effectively reduced, the production cost is effectively suppressed, and the environmental load is reduced with less carbon dioxide emission.

Furthermore, according to the method for manufacturing the fuel cell gas diffusion layer 100 of the first embodiment, the base material precursor forming step (step S10) is to make the paper making base material 13 by making the conductive fiber 11 into paper. Since it comprises a step (step S11) and a carbon precursor resin impregnation step (step S12) in which the paper base material 13 is impregnated with the first carbon precursor resin 14A, the first papermaking body of the conductive fiber 11 is formed. It is easy to attach the carbon precursor resin 14A in a desired distribution, and it is easy to control the gas diffusion layer base material 10 to a desired characteristic.
However, when practicing the present invention, the conductive fibers 11 and the first carbon precursor resin 14A are made together to make the conductive fibers 11 and the first carbon precursor resin. The substrate precursor 15 containing 14A may be formed. And in the said Embodiment 1, the gas diffusion layer base material 10 is formed by impregnating the 1st carbon precursor resin 14 in the papermaking base material 13 formed by making the conductive fiber 11 with the binder 12 paper. However, when practicing the present invention, the gas diffusion layer substrate 10 may be formed by paper-making the conductive fibers 11, the first carbon resin precursor 14A, and the binder 12 together.

  Furthermore, according to the method for manufacturing the fuel cell gas diffusion layer 100 of the first embodiment, in the paper making process (step S11) in the base material precursor formation process (step S10), the conductive fibers 11 and the conductive Since the papermaking substrate 13 is formed by making paper together with the binder 12 that binds the fibers 11, that is, when the conductive fibers 11 are collected by papermaking, the conductive fibers 11 together with the binder 12 that binds the conductive fibers 11 are formed. Since it is accumulated by papermaking, it is possible to facilitate the papermaking by increasing the capture property and the papermaking yield of the conductive fibers 11 at the time of papermaking, and by increasing the dispersibility of the conductive fibers 11 to prevent re-convergence, The entanglement property and reinforcing property of the conductive fiber 11 can be improved. Furthermore, the conductive fibers 11 after papermaking can be prevented from falling off and peeling off to enhance the shape retention and handleability. In particular, the binder 12 is lost (burned out) by heating in the carbonization / graphitization step (step S40), and the disappeared traces become pores (pores, pores) that serve as gas and moisture channels of the gas diffusion layer base material 10. If it is polyvinyl alcohol, a pulp, etc. which form, control of the gas permeability of the gas diffusion layer base material 10 is easy by the addition amount etc. of a binder. In addition, since the pores of a predetermined size are appropriately secured by the disappearance of the binder 12, it is advantageous for improving the permeability and suppressing the generation of cracks.

  In addition, according to the method for manufacturing the fuel cell gas diffusion layer 100 of the first embodiment, the paste-like coating liquid 24 applied to the base material precursor 15 in the gas diffusion layer precursor formation step (step S30) Since the second carbon precursor resin 14B that is carbonized and graphitized by firing in the carbonization / graphitization step (step S40) to become a resin carbide is contained, the obtained microporous layer 20 includes the second carbon precursor resin. The conductive material 21 is bound by the resin carbide formed by carbonizing 14B to form a conductive path. Therefore, the conductivity and layer strength of the microporous layer 20 can be improved. Further, the conductive material 21 is bound to the conductive fiber 11 of the gas diffusion layer base material 10 by the resin carbide obtained by carbonizing the second carbon precursor resin 14B, thereby forming a conductive path. Therefore, the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 is also small, and the conductivity of the entire gas diffusion layer 10 can be increased, and the microporous layer 20 is fixed to the gas diffusion layer substrate 10. Power is improved.

  The paste-like coating liquid 24 thus contains the second carbon precursor resin 14B such as a phenol resin, so that it is possible to conduct electricity without adding a separate dispersant or applying a high shear stress. The dispersibility of the conductive material 21 is high, and the applicability and the smoothness of the microporous layer 20 are also high. Therefore, the surface of the microporous layer 20 is likely to be uniform, the contact resistance with the catalyst layer 110 can be reduced, and moisture can be prevented from being stored between the catalyst layer 110 and the high output of the fuel cell 200. Enable. In addition, the paste-like coating liquid 24 contains the second carbon precursor resin 14B such as a phenol resin, so that the paste-like coating liquid 24 has an appropriate viscosity and soaks (penetrates) into the substrate precursor 15. Is prevented.

  Moreover, according to the manufacturing method of the fuel cell gas diffusion layer 100 of the first embodiment, further, between the base material precursor formation step (step 10) and the gas diffusion layer precursor formation step (step S30). Since the molding step (step S20) for smoothly molding the surface of the substrate precursor 50 is provided, the smoothness of the surface of the gas diffusion layer 100 can be improved. Therefore, it is possible to improve the adhesion with the catalyst layer 110 to reduce the contact resistance and to prevent moisture from being stored between the catalyst layer 110 and the like. Further, the conductive fiber 11 can be prevented from sticking into the electrolyte membrane 120. Therefore, stable output improvement can be achieved in the fuel cell 200.

  Then, the conductive fiber 11 is integrated and the base material precursor 15 containing the first carbon precursor resin 14A contains the conductive material 21 and the second carbon precursor resin 14B. Gas obtained by applying paste-like coating liquid 24 and then heat-firing at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere, impregnating water-repellent resin 31 and drying and baking. According to the diffusion layer 100, the conductive material 21 is bound to the microporous layer 20 by a resin carbide obtained by carbonizing the second carbon precursor resin 14B.

Therefore, the first embodiment is a gas diffusion layer 100 for a fuel cell comprising a gas diffusion layer substrate 10 and a microporous layer 20 disposed on one surface in the thickness direction of the gas diffusion layer substrate 10. The porous layer 20 can also be regarded as an invention of the gas diffusion layer 100 in which the conductive material 21 is bound by a resin carbide obtained by carbonizing the second carbon precursor resin 14B.
According to the gas diffusion layer 100, the conductive material 21 is bound by the resin carbide obtained by carbonizing the second carbon precursor resin 14B, so that a conductive path is formed. Therefore, the conductivity and layer strength of the microporous layer 20 can be improved. Further, the conductive material 21 is bound to the conductive fiber 11 of the gas diffusion layer base material 10 by the resin carbide obtained by carbonizing the second carbon precursor resin 14B, thereby forming a conductive path. Therefore, the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 is also small, and the conductivity of the entire gas diffusion layer 10 can be increased, and the microporous layer 20 is fixed to the gas diffusion layer substrate 10. Power is improved.

[Embodiment 2]
Next, a manufacturing method of the fuel cell gas diffusion layer 100 (cathode side gas diffusion layer 100K, anode side gas diffusion layer 100A) of the second embodiment will be described with reference to FIG.

  In the second embodiment, as shown in the flowchart of FIG. 3, the process from the paper making process (step S11) to the carbonization / graphitization process (step 14) is different from the first embodiment. Since the first paper making process (step S11) and the carbonization / graphitization process (step 14) and thereafter are the same, only differences from the first embodiment will be described.

In Embodiment 1 described above, the carbon precursor resin 14A is impregnated in the carbon precursor resin impregnation step (step S12) with respect to the paper base 13 in which the conductive fibers 11 and the binder 12 are accumulated by papermaking. After the base material precursor 15 is formed, the conductive material 21 for forming the carbon precursor resin 14B and the microporous layer 20 is formed on the base material precursor 15 in the gas diffusion layer precursor formation step (step S30). By applying a paste-like coating liquid 24 containing, a gas diffusion layer precursor 50 composed of the substrate precursor 15 and the microporous layer precursor 25 is formed.
On the other hand, in the second embodiment, the papermaking substrate 13 is formed in the gas diffusion layer precursor forming step (step S31) with respect to the papermaking substrate 13 in which the conductive fibers 11 and the binder 12 are integrated by papermaking. Gas diffusion comprising the base material precursor 15 and the microporous layer precursor 25 by adding a paste-like mixed liquid 26 containing the carbon precursor resin 14 to be impregnated into the electrode and the conductive material 21 for forming the microporous layer 20. The layer precursor 50 is formed to reduce the number of manufacturing steps.

  That is, in the method for manufacturing the fuel cell gas diffusion layer 100 of the second embodiment, as shown in the flowchart of FIG. 3, first, the gas diffusion layer base material 10 is formed in the paper making process (step S11). After forming the paper making base material 13 by making paper together with the conductive fiber 11 to be bonded and the binder 12 to which the conductive fiber 11 is bound, in the subsequent gas diffusion layer precursor forming step (step S31), the paper making base material 13 On the other hand, a paste-like mixed liquid 26 containing the carbon precursor resin 14 and the conductive material 21 is applied, or the papermaking substrate 13 is immersed in the paste-like mixed liquid 26.

  Here, the mixed liquid 26 of the second embodiment is a paste-like mixed liquid containing the carbon precursor resin 14, the conductive material 21, and the dispersion medium 23.

  The carbon precursor resin 14 is carbonized / graphite by high heat treatment in a non-oxidizing atmosphere in the subsequent carbonization / graphitization step (step S40) as in the carbon precursor resins 14A and 14B of the first embodiment. (Hereinafter, also simply referred to as “carbonization” without distinction) to become a conductive carbide (resin that becomes a carbon source), and after carbonization, the conductive fibers 11 and the conductive material 21 are bonded. Any thermosetting resin such as phenol resin, furan resin, epoxy resin, melamine resin, imide resin, urethane resin, aramid resin, urea resin, unsaturated polyester resin, pitch, etc. Etc. are used.

As for the conductive material 21, the microporous layer 20 is formed as in the first embodiment. For example, carbon black, graphite, vapor-grown carbon, activated carbon powder (carbon particles) ) Is used.
And also as the dispersion medium 23 which disperse | distributes these electroconductive materials 21 and the carbon precursor resin 14, the dispersion medium 23, such as alcohol, ketones (acetone, etc.), toluene, water, etc. like the said Embodiment 1. FIG. Is used.

  The mixing / dispersing process in which the conductive material 21 and the carbon precursor resin 14 are dispersed in the dispersion medium 23 is performed, for example, by stirring using a mixer such as a general disper or planetary, a bead mill, or the like. In particular, by blending the carbon precursor resin 14 such as a phenol resin, the conductive material 21 can be highly dispersed without applying a high shear stress or using a dispersant. is there. And since it is highly dispersed without applying high shear stress, if the conductive material 21 is carbon particles, the three-dimensional structure of the carbon particles is easily maintained, and the strength of the resulting microporous layer 20 is improved. Can be planned.

However, when practicing the present invention, the conductive material 21 and the carbon precursor resin 14 may be dispersed using a dispersant. When the dispersibility of the components of the paste-like mixed liquid 26 is increased by using a dispersant, for example, the paste-like mixed liquid 26 may be applied to the papermaking substrate 13 in order to form the gas diffusion layer precursor 50. At the time of application, the pipes and pumps of the application apparatus are not clogged, and application unevenness due to concentration change is not caused.
In particular, the second embodiment also performs carbonization / graphitization firing after the gas diffusion layer precursor formation step (step S31), and the dispersant used for the paste-like mixed liquid 26 is the following carbonization. -Since it can be removed at a high heat treatment temperature in the graphitization step (step S40), it is not limited to the selection of a dispersant having a low decomposition temperature, and the degree of freedom of selection of the dispersant is increased. Examples of the dispersant include polyoxyethylene tridecyl ether, polyoxyethylene alkylphenyl ether (Triton X-100, etc.), polyoxyethylene lauryl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene alkylene. Nonionic (nonionic) surfactants such as alkyl ethers and polyethylene glycol alkyl ethers, cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium chlorides and alkylpyridium chlorides, polyoxyethylene fatty acid esters, acidic groups Surfactants such as anionic surfactants such as structurally modified polyacrylates, polyethylene oxide, methylcellulose, hydroxyethylcellulose, Ethylene glycol (e.g., ethers alkylphenol polyethylene glycol ethers of higher aliphatic alcohols and polyethylene glycol, etc.), a thickener polyvinyl alcohol or the like can be used.

  Then, by applying the paste-like mixed liquid 26 obtained by dispersing the carbon precursor resin 14 and the conductive material 21 in the dispersion medium 23 in this way on one side in the thickness direction of the papermaking base 13, or the papermaking base. A precursor 50 of the gas diffusion layer 100 (hereinafter referred to as “gas diffusion layer precursor 50”) is formed by immersing one side of 13 in the paste-like mixed liquid 26.

  As a method for applying the paste-like mixed liquid 26 to the papermaking substrate 13, brush coating, brush coating, roll coater method, reverse roll coater method, bar coater method, die coater method, blade method, knife coater method, spin coater method, screen Examples thereof include printing, rotary screen printing, curtain coating method, dip coater method, spray coater method, gravure coater method, applicator, and spray spraying. In particular, coating by a (reverse roll) coater or the like can improve the surface smoothness of the gas diffusion layer precursor 50 in which the paste-like mixed liquid 26 is coated on the papermaking substrate 13, but is not necessarily limited thereto. Is not to be done. And by blending the carbon precursor resin 14 such as a phenol resin, the conductive material 21 can be highly dispersed without using the above-described dispersant separately. It is difficult for clogging to occur in the piping and pump of the coating apparatus, and coating unevenness due to concentration change is also difficult to occur.

  Here, when the paste-like mixed liquid 26 containing the carbon precursor resin 14 and the conductive material 21 is applied to one side of the paper-making base 13, or when one side of the paper-making base 13 is immersed in the paste-like mixed liquid 26. The carbon precursor resin 14 in the paste-like mixed liquid 26 penetrates into the paper-making base 13 made of an aggregate of the conductive fibers 11 such as carbon fibers and the binder 12 that have been made, and before carbonization and graphitization. Therefore, the carbon precursor resin 14 and the conductive material 21 adhere to one side of the papermaking substrate 13 because the papermaking substrate 13 has few voids. As a result, the carbon precursor resin 14 is attached to the papermaking base 13 made of an aggregate of the conductive fibers 11 and the binder 12 to form the base precursor 15, and the carbon precursor resin is formed on one surface in the thickness direction. 14 and a precursor 25 of the microporous layer 20 made of the conductive material 21 (hereinafter referred to as “microporous layer precursor 25”) are formed. That is, a gas diffusion layer composed of a base material precursor 15 composed of conductive fibers 11, a binder 12 and a carbon precursor resin 14, and a microporous layer precursor 25 composed of the carbon precursor resin 14 and a conductive material 21. A precursor 50 is formed.

  Thus, in the second embodiment, the conductive material 21 for forming the microporous layer 20 is formed on the paper base 13 in the gas diffusion layer precursor forming step (step S31) subsequent to the paper making step (step S11). The substrate precursor is obtained by applying a paste-like mixed liquid 26 having the carbon precursor resin 14 and the dispersion medium 23 as the main composition, or by immersing the papermaking substrate 13 in the paste-like mixed liquid 26. A gas diffusion layer precursor 50 comprising 15 and a microporous layer precursor 25 is obtained.

  In the second embodiment, the paste-like mixed liquid 26 contains the carbon precursor resin 14 so that the paste-like mixed liquid 26 has an appropriate viscosity and consistency, and separately contains a dispersant and a thickener. Even if not, the conductive material 21 is highly dispersed, and the applicability is ensured. However, when practicing the present invention, as described above, in the paste-like mixed liquid 26, a surfactant or the like for increasing the dispersibility of the conductive material 21 or the like is increased as necessary. It is also possible to add a thickener for the purpose. Even when these surfactants and thickeners are blended in the paste-like mixed liquid 26, the surfactants and thickeners are thermally decomposed by the high-temperature heat treatment in the subsequent carbonization / graphitization step (step S40). Therefore, the burden of the drying and baking process in the subsequent drying and baking process (step S60) is not increased.

  Next, in the second embodiment, the calendering step (step S20) is performed on the gas diffusion layer precursor 50 composed of the base material precursor 15 and the microporous layer precursor 25 thus formed. Molding for smoothing the surface of the gas diffusion layer precursor 50 is performed by molding, press molding (pressure molding), or the like.

  Thereby, the unevenness of the front and back surfaces in the thickness direction of the gas diffusion layer precursor 50 is reduced, the surface is smoothed, and the contact property with the peripheral layers such as the catalyst layer 110 and the separator 140 is improved when incorporated in the fuel cell 200. It becomes possible to reduce contact resistance. In addition, even if protrusions such as fiber frays are present on the surface of the gas diffusion layer precursor 50, it can be suppressed by pressing or the like. Further, by adjusting the orientation of the conductive fibers 11 or adjusting the denseness of the gas diffusion layer precursor 50 by pressing, the conductivity, strength, moisture and gas permeability of the gas diffusion layer 100, etc. Allows adjustment of characteristics. That is, the molding pressure at this time is set in consideration of desired characteristics (conductivity, strength, moisture and gas permeability, etc.) of the gas diffusion layer 100, and is within a range of, for example, 0.01 to 10 MPa. Is done.

  In the molding step (step S20) at this time, the moisture of the gas diffusion layer precursor 50 is removed by drying, for example, by heating at 50 to 200 ° C. Furthermore, the carbon precursor resin 14 may be cured by heating during molding. Thereby, in the next carbonization / graphitization step (step 40), the carbon precursor resin 14 can be fixed by suppressing vaporization at the time of carbonization. Therefore, the contact property with the conductive fibers 11 and the conductive material 21 can be achieved. In addition, the deformation of the gas diffusion precursor 50 can be prevented, and the strength of the gas diffusion layer 100 and the bonding property with the surrounding layers can be improved.

  And after shaping | molding in this way, similarly to the said Embodiment 1, with respect to the gas diffusion layer precursor 50, in a non-oxidizing atmosphere in a carbonization and graphitization process (step S40). High-temperature heat firing is performed, and further, water-repellent resin 31 is impregnated in the water-repellent resin impregnation step (step S50), and then dry firing is performed in the dry firing step (step S60). A gas diffusion layer 100 comprising the gas diffusion layer substrate 10 and the microporous layer 20 is obtained.

  Also in the carbonization / graphitization step (step S40) of the second embodiment, the temperature is usually 1000 to 3500 ° C., preferably 1200 to 3000 ° C. in a non-oxidizing atmosphere such as an inert treatment (inert gas). The carbon precursor resin 14 in the substrate precursor 15 and the carbon precursor resin 14 in the microporous layer precursor 25 are carbonized and graphitized by performing a heating and baking treatment for 10 minutes to 1 hour in a temperature range. .

Also in the second embodiment, the carbon precursor resin 14 such as a phenol resin is carbonized and graphitized by such a high-temperature baking treatment in a non-oxidizing atmosphere. The carbonized and graphitized resin, that is, resin carbide, binds the conductive fibers 11 and the conductive material 21 to form a strong conductive path, and the gas diffusion layer base material 10 and the microporous layer 20 obtained. The conductivity and strength of the can be increased.
That is, in the carbonization / graphitization step (step S40), the gas diffusion layer precursor 50 is subjected to high-temperature heat treatment in a non-oxidizing atmosphere, so that a carbon precursor resin such as a phenol resin in the substrate precursor 15 is obtained. The conductive fiber 11 is bound by a resin carbide obtained by carbonizing and graphitizing and carbonizing and graphitizing the carbon precursor resin 14. The carbon precursor resin 14 such as a phenol resin in the microporous layer precursor 25 is also carbonized and graphitized, and the conductive material 12 is bound by a resin carbide obtained by carbonizing and graphitizing the carbon precursor resin 14. Is done. Furthermore, at the boundary between the base material precursor 15 and the microporous layer precursor 25, the conductive fibers 11 and the conductive material 21 are bound by a resin carbide obtained by carbonizing the carbon precursor resin 14 such as a phenol resin. Thereby, in the gas diffusion layer 100 to be obtained, the fixing of the gas diffusion layer base material 10 and the microporous layer 20 becomes high. That is, the gas diffusion layer substrate 10 and the microporous layer 20 are strongly connected, and the microporous layer 20 is difficult to peel from the gas diffusion layer substrate 10 even when assembled to the fuel cell 200. Further, the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 is small.

  Thus, also in the second embodiment, the carbon diffusion resin 50 is subjected to high heat treatment in the non-oxidizing atmosphere in the carbonization / graphitization step (step S40), thereby containing the carbon precursor resin 14 such as a phenol resin. The carbon precursor resin 14 of the base material precursor 15 and the microporous layer precursor 20 to be carbonized is carbonized. And the conductive fiber 11 and the conductive material 21 are bound by those resin carbides. Further, the substrate precursor 15 becomes porous, and micropores smaller than the voids (pores) of the substrate precursor 15 are formed in the microporous layer 20. Further, when a binder 12 such as polyvinyl alcohol, polylactic acid, pulp, etc. is disposed in the base material precursor 15 before carbonization / graphitization, the binder 12 is decomposed and disappears, and the disappearance trace is It becomes a void (pore). Even if a part of the carbon precursor resin 14 disappears, the disappearance trace becomes a void. Further, as described above, even when a dispersing agent such as a surfactant or a thickener is arranged in the paste-like mixed liquid 26, the dispersing agent is obtained by the high-temperature heat treatment in the carbonization / graphitization step (step S40). Is removed. Therefore, the burden of removing the dispersant is not applied in the subsequent drying and firing step (step S60).

  Also in the second embodiment, the water-repellent resin 31 is impregnated in the water-repellent resin impregnation step (step S50) with respect to the gas diffusion layer precursor 50 thus heated and fired in a non-oxidizing atmosphere. After that, in the drying and firing step (step S60), drying and firing are performed. As in the first embodiment, the amount of the dispersant present in the gas diffusion layer precursor 50 to be dried and fired at this time is small. Therefore, it is possible to sufficiently remove the moisture and the dispersant even in a short time and at a low temperature as compared with the conventional case. That is, also in the second embodiment, in the drying and baking step (step S60), the dispersant and the water used for dispersing the water-repellent resin 31 are only removed, so that the moisture and the dispersant are decomposed and volatilized. The drying and firing necessary for disappearing, in other words, the drying and firing necessary for developing the water repellency by the water-repellent resin 31 may be performed at a low temperature. In addition, it is possible to shorten the time required for drying and baking for decomposing / volatilizing and erasing moisture and a dispersant to develop water repellency. Accordingly, the furnace length of the drying and firing furnace can be shortened, and further, the time for raising the temperature to a predetermined temperature for the development of water repellency can be shortened, so that the time required for the drying and firing treatment can be shortened. Therefore, the load concerning drying and firing can be reduced, and the power required for the drying and firing treatment in the drying and firing step (step S60) can be suppressed, and the manufacturing cost can be reduced.

  The gas diffusion layer 100 according to Embodiment 2 manufactured as described above is also a multilayer structure including the gas diffusion layer base material 10 and the microporous layer 20 formed on one surface in the thickness direction of the gas diffusion layer base material 10. Have

  Also in the gas diffusion layer base material 10 according to the second embodiment, moisture and gas permeability are ensured by forming predetermined pores and being porous. Also. When the carbon precursor resin 14 is carbonized and graphitized at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere, the conductive fibers 11 are formed by the resin carbide obtained by carbonizing and carbonizing the carbon precursor resin 14. It is bound. Thus, since the conductive fiber 11 is bound to the resin carbide, a conductive path is formed and has high conductivity and strength.

  Also, in the microporous layer 20 according to the second embodiment, micropores smaller than the voids (pores) of the gas diffusion layer base material 10 are formed and porous, and moisture and gas permeability are ensured. ing. In particular, by adding a paste-like mixed liquid 26 containing the conductive material 21 for forming the microporous layer 20 and the carbon precursor resin 14 to the papermaking substrate 13 before carbonization / graphitization, together with the substrate precursor 15, The microporous layer precursor 25 formed on the substrate precursor 15 is baked under predetermined heating conditions in the carbonization / graphitization step (step S40), so that the temperature is 1000 to 3500 ° C. in a non-oxidizing atmosphere. The carbon precursor resin 14 is carbonized / graphitized at a temperature, and the conductive material 21 is bound by a resin carbide formed by carbon / graphitizing the carbon precursor resin 14. In this way, the conductive material 21 is bonded to the resin carbide, so that a conductive path is formed, and it has high conductivity and layer strength and is strong.

  Further, also in the second embodiment, a paste-like mixed liquid 26 containing the conductive material 21 for forming the microporous layer 20 and the carbon precursor resin 14 is added to the papermaking base 13 before carbonization / graphitization, Since the microporous layer precursor 25 is fired together with the base material precursor 15 under predetermined heating conditions in the carbonization / graphitization step (step S40), at the boundary between the base material precursor 15 and the microporous layer precursor 25. The gas diffusion layer is formed by binding the conductive fiber 11 in the substrate precursor 15 and the conductive material 12 in the microporous layer precursor 25 with a resin carbide obtained by carbonizing the carbon precursor resin 14. The joint strength of the base material 10 and the microporous layer 20 is high, and the fixing power of the microporous layer 20 to the gas diffusion layer base material 10 is high. In addition, the formation of a conductive path made of a resin carbide obtained by carbonizing the carbon precursor resin 14 reduces the contact resistance between the gas diffusion layer substrate 10 and the microporous layer 20 and is advantageous for current collection.

  In particular, in the second embodiment, a paper-making substrate is obtained by adding a paste-like mixed liquid 26 containing the conductive material 21 and the carbon precursor resin 14 to the paper-making substrate 13 before carbonization / graphitization. Since 13 is before carbonization / graphitization, the gap is small, so that the carbon precursor resin 14 is adhered to the paper base 13 to form the base precursor 15, and on one side of the paper base 13. A microporous layer precursor 25 made of the conductive material 21 and the carbon precursor resin 14 is formed. That is, by adding the conductive material 21 for forming the microporous layer 20 at the same time as impregnating the paper precursor 13 with the carbon precursor resin 14, the number of manufacturing steps is reduced, and the manufacturing steps are reduced. Has been shortened. Therefore, the manufacturing cost can be reduced by simplifying the manufacturing workability and the manufacturing process.

  As described above, the method for manufacturing the fuel cell gas diffusion layer 100 according to the second embodiment includes a gas diffusion layer for a fuel cell including the gas diffusion layer base material 10 and the microporous layer 20 disposed on one surface in the thickness direction. A method of manufacturing the layer 100, in which a paper making process (step S11) for forming a paper making base material 13 in which conductive fibers 11 and a binder 12 are integrated by paper making, and a carbon precursor resin for the paper making base material 13; 14 and a gas diffusion layer precursor forming step (step S31) for forming a gas diffusion layer precursor 50 by adding a paste-like mixed liquid 26 containing a conductive material 21 for forming the microporous layer 20, and gas diffusion The layer precursor 50 is heated and fired at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere to carbonize and graphitize the carbon precursor resin 14 (step S40). A water-repellent resin impregnation step (step S50) in which the gas diffusion layer precursor 50 after carbonization / graphitization is impregnated with the water-repellent resin 31, and the gas diffusion layer precursor 50 impregnated with the water-repellent resin 31 is dried and fired A drying firing step (step S60).

  According to the fuel cell gas diffusion layer 100 of Embodiment 2 and the method for producing the same, the conductivity for forming the carbon precursor resin 14 and the microporous layer 20 with respect to the papermaking substrate 13 before carbonization / graphitization. A paste-like mixed liquid 26 containing the material 21 is added to form a gas diffusion layer precursor 50 composed of the substrate precursor 15 and the microporous layer precursor 25, and the microporous layer precursor 25 together with the substrate precursor 15. Is carbonized and graphitized. Since the gas diffusion layer precursor 50 is only impregnated with the water-repellent resin 31 after carbonization / graphitization, the gas diffusion layer precursor 50 that is dried and fired after the water-repellent treatment impedes water repellency. Low content of dispersant. In particular, a paste-like mixed liquid 26 containing the carbon precursor resin 14 and the conductive material 21 for forming the microporous layer 20 is applied to the papermaking base 13 before carbonization / graphitization. Since the graphitization step (step S40) is performed, even when the paste-like mixed liquid 26 contains a dispersant, the dispersant at that time disappears in the carbonization / graphitization step (step S40) in which high-temperature heat treatment is performed. To do. Accordingly, in the drying and firing step (step S60) after the water repellent treatment, a nonionic surfactant or the like for dispersing the conductive material contained in the pasty mixture 27 for forming the microporous layer as in the past is used. There is no need to remove the dispersant. Therefore, high water repellency can be ensured without drying and firing at a lower temperature than before, without the dispersant in the gas diffusion layer precursor 50 being sufficiently removed and remaining. In addition, the time required for the drying and firing treatment can be shortened.

Conventionally, since the paste mixture 27 for forming the microporous layer is applied to a porous base material that has been subjected to a high temperature treatment, the paste-like mixture 27 soaks (permeates) into the porous base material. In order to prevent and prevent the components of the paste-like mixture 27 from being fixed on the surface of the porous base material, the porous base material is impregnated with the water-repellent resin 31a and the moisture is dried. It was necessary to apply, or it was necessary to mix a thickener with the paste-like mixture 27 to increase the viscosity, and the manufacturing process and manufacturing work were complicated.
In contrast, in the method of manufacturing the fuel cell gas diffusion layer 100 of the second embodiment, the paste-like mixed liquid 26 is applied to the papermaking base material 13 before carbonization / graphitization. The paper-making base 13 can be impregnated with the carbon precursor resin 14 by adding the paste-like mixed liquid 26 to the material 13, and the conductivity for forming the carbon precursor resin 14 and the microporous layer 20 on the surface of the base precursor 15. The material 21 can be fixed. Therefore, the manufacturing process and manufacturing workability can be simplified.

  As described above, according to the fuel cell gas diffusion layer 100 and the manufacturing method thereof according to the second embodiment, it is possible to reduce the time and temperature required for drying and firing, and simplify the manufacturing workability and the manufacturing process. Therefore, it is possible to reduce the manufacturing cost and the environmental load.

The description of the second embodiment is a gas diffusion layer 100 for a fuel cell comprising a gas diffusion layer base material 10 and a microporous layer 20 disposed on one surface in the thickness direction of the gas diffusion layer base material 10. The microporous layer 20 can also be regarded as an invention of the gas diffusion layer 100 in which the conductive material 21 is bound by a resin carbide obtained by carbonizing the carbon precursor resin 14.
According to the gas diffusion layer 100, the conductive material 21 is bound by the resin carbide formed by carbonizing the carbon precursor resin 14, and a conductive path is formed. Therefore, the conductivity and layer strength of the microporous layer 20 can be improved. In addition, the conductive material 21 is bound to the conductive fiber 11 of the gas diffusion layer base material 10 by the resin carbide formed by carbonizing the carbon precursor resin 14, thereby forming a conductive path. The contact resistance between the diffusion layer substrate 10 and the microporous layer 20 is also small, the conductivity of the gas diffusion layer 10 as a whole can be increased, and the fixing force of the microporous layer 20 to the gas diffusion layer substrate 10 is improved. To do.

  By the way, since the gas diffusion layer base material 10 of the gas diffusion layer 100 of the said Embodiment 1, 2 is a paper-like thing formed by making the conductive fiber 11, it is compared with cloth shape or felt shape (nonwoven fabric). Even if it is thin, it has high dimensional stability in the surface direction and thickness direction, excellent molding processability, and high bending rigidity, so it has excellent handling properties when stacking the membrane / electrode assembly 150 ing. Further, the paper-like one that makes the conductive fibers 11 can obtain a high air permeability and can reduce the pore diameter, so that it is suitable not only for use in low humidity conditions but also in high humidity conditions. In addition, since the unevenness can be reduced, adhesion with the catalyst layer 110 can be improved. Furthermore, since it is thin and easy to mold, it is easy to reduce the stack size. In addition, since the dimensional stability after cutting in the process of cutting the gas diffusion layer 100 to a predetermined dimension is also good, and excellent in easy chucking and easy mobility in the transfer process by the robot, the fuel cell 200 can be mass-produced. It is advantageous. Further, the sheet-like material can cope with the thinning of the electrode 130 of the fuel cell 200.

In the first and second embodiments, the gas diffusion layer base material 10 has been described as a paper-like material in which the conductive fibers 11 are accumulated by papermaking. However, when the present invention is carried out, the gas diffusion layer base material is used. 10 may be in the form of cloth, felt (nonwoven fabric), or mat.
The thickness of the gas diffusion layer 100 is, for example, 1 μm to 400 μm, preferably 50 μm to 300 μm, and the microporous layer 20 is 50% of the thickness of the gas diffusion layer substrate 10. It is as follows.
The arrangement of the microporous layer 20 may be on both sides instead of one of the front and back surfaces of the gas diffusion layer substrate 10.

  In the first and second embodiments, the binder 12 such as PVA fiber made together with the conductive fiber 11 is eliminated in the carbonization / graphitization step (step S40). A heating step for eliminating the binder 12 such as PVA fibers may be provided before the carbon precursor resin impregnation step (step S40).

  Furthermore, when implementing this invention, you may perform the drying which removes the water | moisture content (a dispersion medium is included) in the gas diffusion layer precursor 50 before carbonization and graphitization, and a carbon precursor as needed. The resins 14, 14A and 14B may be cured.

In practicing the present invention, the configuration, composition, components, blending amount, material, and other manufacturing processes of other parts of the fuel cell gas diffusion layer 100 are limited to those in the first and second embodiments. It is not a thing.
In addition, the numerical values given in the first embodiment and the examples of the present invention do not indicate critical values, but indicate appropriate values suitable for implementation. Is not to deny.

DESCRIPTION OF SYMBOLS 10 Gas diffusion layer base material 11 Conductive fiber 12 Binder 13 Papermaking base material 14 Carbon precursor resin 14A 1st carbon precursor resin 14B 2nd carbon precursor resin 15 Base material precursor 20 Microporous layer 21 Conductive material 24 coating solution 25 microporous layer precursor 26 mixed solution 31 water repellent resin 100 gas diffusion layer 200 fuel cell S10 base material precursor forming step S11 paper making step S12 carbon precursor resin impregnation step S30, S31 gas diffusion layer precursor forming step S40 Carbonization / graphitization process S50 Water-repellent resin impregnation process S60 Dry firing process

Claims (9)

A method for producing a gas diffusion layer for a fuel cell, comprising producing a gas diffusion layer comprising a gas diffusion layer substrate and a microporous layer disposed on one or both sides in the thickness direction of the gas diffusion layer substrate,
A base material precursor forming step of forming a gas diffusion layer base material precursor in which conductive fibers are integrated and the first carbon precursor resin is contained;
Gas diffusion in which a coating liquid containing a conductive material for forming a microporous layer is applied to the base material precursor formed in the base material precursor formation step to form the precursor of the gas diffusion layer. A layer precursor forming step;
The gas diffusion layer precursor formed in the gas diffusion layer precursor formation step is heated and fired in a non-oxidizing atmosphere to carbonize and graphitize the first carbon precursor resin. Process,
A water-repellent resin impregnation step of impregnating the water-repellent resin with respect to the gas diffusion layer precursor after the carbonization and graphitization;
A method for producing a gas diffusion layer for a fuel cell, comprising: a drying and firing step of drying and firing the gas diffusion layer precursor impregnated with the water repellent resin.   The base material precursor forming step includes a paper making step of forming the paper base by making the conductive fibers, and a carbon precursor resin impregnation step of impregnating the first carbon precursor resin to the paper base. The method for producing a gas diffusion layer for a fuel cell according to claim 1, comprising:   The coating liquid applied to the base material precursor in the gas diffusion layer precursor formation step is carbonized and graphitized by heating and baking in a non-oxidizing atmosphere in the carbonization / graphitization step and resin carbide. The manufacturing method of the gas diffusion layer for fuel cells of Claim 1 or Claim 2 containing the 2nd carbon precursor resin which becomes. A method for producing a gas diffusion layer for a fuel cell, comprising producing a gas diffusion layer comprising a gas diffusion layer substrate and a microporous layer disposed on one or both sides in the thickness direction of the gas diffusion layer substrate,
A papermaking process for forming a papermaking substrate in which conductive fibers are integrated;
A gas diffusion layer precursor forming step of forming a precursor of the gas diffusion layer by adding a mixed liquid containing a carbon precursor resin and a conductive material for forming a microporous layer to the papermaking substrate;
A carbonization / graphitization step in which the gas diffusion layer precursor formed in the gas diffusion layer precursor formation step is heated and fired in a non-oxidizing atmosphere to carbonize and graphitize the carbon precursor resin;
A water-repellent resin impregnation step of impregnating the water-repellent resin with respect to the gas diffusion layer precursor after the carbonization and graphitization;
A method for producing a gas diffusion layer for a fuel cell, comprising: a drying and firing step of drying and firing the gas diffusion layer precursor impregnated with the water repellent resin.   The gas diffusion for a fuel cell according to any one of claims 1 to 4, wherein the accumulation of the conductive fibers is made by papermaking the conductive fibers together with a binder for binding the conductive fibers. Layer manufacturing method.   6. The fuel cell according to claim 1, wherein a temperature at which the gas diffusion layer precursor is dried and fired in the drying and firing step is in a range of 200 to 250 ° C. 6. A method for producing a gas diffusion layer.   The conductive material for forming the microporous layer is carbon black having a median diameter in a range of 30 nm to 100 nm, according to any one of claims 1 to 6. A method for producing a gas diffusion layer for a fuel cell.   The fuel according to any one of claims 1 to 6, wherein the conductive material for forming the microporous layer is graphite having a particle diameter in a range of a median diameter of 3 µm to 20 µm. A method for producing a gas diffusion layer for a battery. A gas diffusion layer for a fuel cell comprising a gas diffusion layer substrate and a microporous layer disposed on one or both sides in the thickness direction of the gas diffusion layer substrate,
The microporous layer is formed by binding a conductive material constituting the microporous layer with a resin carbide formed by carbonizing a carbon precursor resin at a temperature of 1000 to 3500 ° C. in a non-oxidizing atmosphere. A gas diffusion layer for a fuel cell.

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