JP5987484B2 - Gas diffusion electrode substrate and method for producing the same - Google Patents

Description

  The present invention relates to a gas diffusion electrode substrate suitably used for a gas diffusion layer of a fuel cell, particularly a polymer electrolyte fuel cell. More specifically, gas diffusion that achieves both high drainage and low water vapor diffusivity, can exhibit high power generation performance over a wide temperature range from low temperature to high temperature, and has excellent mechanical properties, electrical conductivity, and thermal conductivity. The present invention relates to an electrode substrate.

  A gas diffusion electrode base material (hereinafter referred to as an electrode base material) containing carbon fibers is widely used in a gas diffusion layer of a fuel cell because it is excellent in conductivity and thermal conductivity and excellent in mechanical properties. . However, when the polymer electrolyte fuel cell is operated at a relatively low temperature of less than 70 ° C., water generated by the reaction fills the electrode substrate in a high current density region, resulting in insufficient supply of fuel gas. There is a known problem (flooding) that the performance decreases. On the other hand, when operating at a relatively high temperature of 80 ° C. or higher, there is a known problem (dry-up) in which power generation performance decreases as a result of drying of the electrolyte membrane due to water vapor diffusion and decreasing proton conductivity.

  In order to eliminate flooding and dry-up, studies are underway to control the pore structure.

Patent Document 1 discloses an electrode base material containing carbonaceous powder and having a density and pore diameter within a specific range. In this method, by setting the density to be in the range of 0.25 to 0.55 g / cm ³ and the pore diameter in the range of 25 to 55 μm, the flooding and dry-up are optimized to be relatively small. However, by controlling the density and pore diameter within such ranges, the suppression of dry-up and flooding is insufficient, and the power generation performance is still insufficient.

  Patent Documents 2 to 5 disclose a method of forming a through hole in the thickness direction of an electrode base material. In this method, flooding is improved by the through hole acting as a drainage path. However, since water vapor diffuses through the through holes and dry-up at a high temperature becomes remarkable, the power generation performance is still insufficient. Moreover, the problem that mechanical properties, such as a bending elastic modulus and bending strength of an electrode base material, are impaired by through-hole formation remained.

  Patent Document 6 discloses a method in which an organic fiber fibrillar material is made together with carbon fiber and then impregnated with a resin composition and carbonized to produce an electrode substrate. In this method, the resin composition attached around the fibril-like substance remains as a net-like carbide, and small pores having a diameter of about 10 μm and large pores having a diameter of about 30 μm are formed. Flooding is improved because drainage is facilitated by large pores. However, the suppression of dry-up is insufficient, and the power generation performance is still insufficient. Moreover, it is difficult to control the extent of organic fiber fibrils during papermaking, and it is difficult to produce the same electrode substrate with good reproducibility. Moreover, the specific gravity difference between the carbon fiber and the organic fiber fibril is large, and the problem remains that the paper tends to be non-uniform in the thickness direction during papermaking.

  Patent Document 7 discloses an electrode base material produced by laminating and integrating a plurality of types of pre-impregnated bodies having different pore mode diameters and then firing them. In this method, since drainage is promoted from the smaller pore mode diameter to the larger pore mode, flooding is improved. However, the suppression of dry-up is insufficient, and the power generation performance is still insufficient. Further, in the process of manufacturing the electrode base material, there is a problem that a difference in curing shrinkage and a heat shrinkage difference occur between the front and back surfaces, and the electrode base material is likely to warp.

  On the other hand, in order to improve the performance of the electrode base material, studies have been conducted to control the shape and characteristics of carbon fibers.

  In patent document 8, the electrode base material using the carbon fiber baked in the temperature range of 1800-2400 degreeC is disclosed. However, although this method improves the conductivity and thermal conductivity of the electrode substrate, flooding and dry-up cannot be suppressed.

  Patent Document 9 discloses an electrode base material including two or more types of carbon fibers, that is, carbon fibers having a diameter of 4 to 9 μm and carbon fibers having different diameters. This method improves the conductivity and thermal conductivity of the electrode substrate. In addition, the pore diameter can be increased without changing the density. As a result, flooding tended to be improved, but the effect was insufficient.

JP 2004-311431 A Japanese Patent Laid-Open No. 08-111226 JP 2002-110182 A Japanese Patent Application Laid-Open No. 2004-152584 JP 2008-190072 A JP 2006-040886 A JP 2009-234851 JP 2009-283259 A JP 09-324390 A

  In view of the background of such conventional technology, the object of the present invention is to achieve both high drainage and low water vapor diffusibility, and can exhibit high power generation performance over a wide temperature range from low temperature to high temperature. An object of the present invention is to provide a fuel cell gas diffusion electrode base material having excellent properties and thermal conductivity.

The gas diffusion electrode substrate of the present invention employs the following means in order to solve such problems. That is, a gas diffusion electrode substrate obtained by binding carbon fibers of the following [A] and [B] with a carbide, having a density in the range of 0.2 to 0.4 g / cm ³ and a pore diameter of A gas diffusion electrode substrate characterized by being in the range of 40 to 70 μm.
[A] Carbon fiber having an average diameter of a single fiber of 3 μm to 8 μm and an average length of 4 to 20 mm [B] The average diameter of the single fiber is more than 8 μm and 30 μm or less, and the average length is 0.5 ~ 4 mm carbon fiber also of method for producing a gas diffusion electrode substrate of the present invention, in order to solve the above problems, and adopts the following means. That is, after forming a pre-impregnated body by impregnating 50 to 200 parts by mass of a resin component with respect to 100 parts by mass of carbon fiber in a papermaking body obtained by papermaking the carbon fiber [A] and the carbon fiber [B]. The pre-impregnated body is carbonized. The method for producing a gas diffusion electrode substrate.

The preferable aspect of this invention is that the average length of the said carbon fiber [B] is 0.5-4 mm. Moreover, the other preferable aspect of this invention is that the thickness of the said electrode base material is in the range of 150-250 micrometers, and the carbon fiber fabric weight of the said electrode base material is in the range of 20-40 g / m < ² >. That is, the electrode base material contains carbonaceous powder, and the papermaking body contains 10 to 100 parts by mass of pulp with respect to 100 parts by mass of carbon fibers.

  According to the present invention, an electrode base material that achieves both high drainage and low water vapor diffusibility, can exhibit high power generation performance over a wide temperature range from low temperature to high temperature, and is excellent in mechanical properties, electrical conductivity, and thermal conductivity. Can be obtained.

  As a result of earnest investigation for an electrode base material that achieves both high drainage and low water vapor diffusibility and has excellent power generation performance over a wide temperature range from low temperature to high temperature, In addition, the present inventors have found that this problem can be solved when the density and pore diameter are within a specific range in an electrode base material including carbon fibers having a single fiber diameter larger than that of the carbon fibers.

  The electrode substrate of the present invention is formed by binding carbon fibers with carbides. Such an electrode substrate is usually obtained by impregnating a carbon fiber sheet with a resin and carbonizing the sheet, as will be described later.

  Examples of the carbon fiber in the present invention include polyacrylonitrile (PAN) -based, pitch-based, and rayon-based carbon fibers. Of these, PAN-based and pitch-based carbon fibers are preferably used because of their excellent mechanical strength.

In the present invention, the average diameter of single fibers is 3 μm or more and 8 μm or less, the carbon fiber [A] having an average length of 4 to 20 mm, and the average diameter of single fibers is more than 8 μm and not more than 30 μm, and the average length is It is necessary to include both 0.5 to 4 mm carbon fiber [B]. By adding carbon fiber [B] having a diameter larger than that of carbon fiber [A] to carbon fiber [A], the number of carbon fibers necessary to maintain the same density is reduced. As a result, the density is maintained. Meanwhile, the pore diameter can be increased. It is known that the water vapor diffusibility depends on the porosity, and the porosity is proportional to the reciprocal of the density. Therefore, it is considered that the water vapor diffusibility is maintained by maintaining the density. On the other hand, drainage is known to depend on the pore size when the pressure required to push liquid water into pores made of hydrophobic carbon fibers is used as an index, and the pore size is increased. This is thought to improve drainage. As a result, an electrode base material having excellent power generation performance over a wide temperature range from low temperature to high temperature can be obtained.

  In the present invention, the average diameter of the single fiber in the carbon fiber [A] is required to be in the range of 3 μm or more and 8 μm or less from the viewpoint of achieving both high drainage and low water vapor diffusion, and is 5 μm or more and 8 μm or less. It is preferable to be within the range. When the average diameter is less than 3 μm, the pore diameter becomes small, the drainage performance is lowered, and flooding cannot be suppressed. On the other hand, when the average diameter is larger than 8 μm, the water vapor diffusibility increases and the dry-up cannot be suppressed.

  In the present invention, the average diameter of the single fiber in the carbon fiber [B] is required to be in the range of more than 8 μm and 30 μm or less in view of achieving both high drainage and low water vapor diffusion, and more than 10 μm. It is preferably within a range of 25 μm or less, and more preferably within a range of more than 12 μm and 20 μm or less. When the average diameter is 8 μm or less, the pore diameter becomes small, the drainage performance decreases, and flooding cannot be suppressed. On the other hand, when the average diameter is larger than 30 μm, the water vapor diffusibility increases, and the dry-up cannot be suppressed.

  Here, the average diameter of the single fiber in the carbon fiber is taken with a microscope such as a scanning electron microscope, the carbon fiber is magnified 1000 times or more, and 30 different single fibers are randomly selected. The diameter was measured and the average value was obtained. As a scanning electron microscope, S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used.

  In the present invention, the average length of the carbon fiber [A] needs to be 4 mm or more from the viewpoint that the electrode base material has excellent mechanical properties, electrical conductivity, and thermal conductivity. Generally, carbon fibers [A] having a small average diameter of single fibers have a larger strength than carbon fibers [B] because there are few surface defects with respect to the fiber diameter, and carbon fibers [A] have a large influence on the strength of papermaking bodies. When the carbon fiber [A] is 4 mm or less, the strength of the papermaking body is remarkably insufficient and the papermaking body cannot be obtained. On the other hand, if the average length is greater than 20 mm, the dispersibility of the carbon fibers during papermaking decreases, and it is difficult to obtain a homogeneous electrode substrate. Carbon fibers having such an average length can be obtained by a method of cutting continuous carbon fibers into a desired length.

  In the present invention, the average length of the carbon fibers [B] needs to be 0.5 mm or more from the viewpoint of papermaking properties. When the average length is less than 0.5 mm, the carbon fibers [B] pass through the paper body during paper making, and it becomes difficult to adjust the blending amount of the carbon fibers [B]. On the other hand, if the average length is larger than 20 mm, the dispersibility of the carbon fibers during papermaking is lowered, and it becomes difficult to obtain a homogeneous electrode substrate. The preferred combination of the average length of the carbon fiber [A] and the carbon fiber [B] is that, from the viewpoint of mechanical properties, conductivity, and thermal conductivity, the strength of the paper body increases as the average length increases. The carbon fiber [A] has an average length of 4 to 20 mm, and the carbon fiber [B] has an average length of 0.5 to 4 mm, preferably 0.5 mm or more and less than 4 mm. From the viewpoint of papermaking properties, as the average length of the carbon fiber [B] increases, the dispersibility decreases due to the entanglement between the carbon fiber [A] and the carbon fiber [B]. It is preferable that the length is 4 to 20 mm and the average length of the carbon fiber [B] is 0.5 to 4 mm.

  The carbon fiber [B] having such an average length is obtained by dispersing continuous carbon fiber into a desired length or by dispersing the carbon fiber [B] in water and stirring the mixture using a mixer or a slashfiner. It is obtained by a method of

  When pulp is included in the paper body, the carbon fiber [B] is added to the water in which the pulp is dispersed and stirred, and the fiber is shortened while dispersing the carbon fiber [B]. B] It is preferable because it works as a buffer material for entanglement and improves dispersibility.

  Here, the average length of the carbon fiber is a length such as a scanning electron microscope or the like. Is measured and the average value is obtained. As a scanning electron microscope, S-4800 manufactured by Hitachi, Ltd. or an equivalent thereof can be used. In addition, although the average diameter and average length of the single fiber in carbon fiber are normally measured by observing the carbon fiber directly about the carbon fiber used as a raw material, you may observe and measure an electrode base material.

  In addition, the dispersibility when paper making the carbon fiber [A] and the carbon fiber [B] is observed by enlarging the surface of the paper body cut into a circular shape having a diameter of 7.5 cm with an optical microscope to 5 times or more, Evaluation was performed by counting the number of bundles composed of aggregates of carbon fiber [A] and carbon fiber [B] having a width of 0.5 mm or more. Since bundling can cause a decrease in the durability of the fuel cell, it is preferable that the binding be small.

  In this invention, it is preferable that the compounding ratio of carbon fiber [B] with respect to 100 mass parts of carbon fiber [A] is 20-200 mass parts, It is more preferable that it is 30-150 mass parts, Furthermore, 40- It is preferably 120 parts by mass. When the blending ratio is 20 parts by mass or more, drainage performance is improved, flooding is improved, and power generation performance at low temperatures is improved. On the other hand, when the blending ratio is 200 parts by mass or less, the smoothness of the electrode base material is increased, the electric resistance between the separator and the power generation performance is improved. Furthermore, the flexibility of the electrode substrate is increased, and the handleability is improved.

In the present invention, the density of the electrode base material needs to be in the range of 0.2 to 0.4 g / cm ³ , and preferably in the range of 0.22 to 0.35 g / cm ³ , More preferably, it is in the range of 0.24 to 0.3 g / cm ³ . When the density is less than 0.2 g / cm ³ , the water vapor diffusibility is large, and dry-up cannot be suppressed. Further, the mechanical properties are insufficient, and the electrolyte membrane and the catalyst layer cannot be sufficiently supported. In addition, the electrical conductivity is insufficient, and the power generation performance decreases at both high and low temperatures. On the other hand, if the density is larger than 0.4 g / cm ³ , the drainage performance is lowered and flooding cannot be suppressed. The electrode base material having such a density can be obtained by controlling the carbon fiber basis weight in the pre-impregnated body, the blending amount of the resin component with respect to the carbon fiber, and the thickness of the electrode base material in the production method described later. Among these, it is effective to control the carbon fiber basis weight in the pre-impregnated body and the blending amount of the resin component with respect to the carbon fiber. Here, a low-density substrate is obtained by reducing the carbon fiber basis weight of the pre-impregnated body, and a high-density substrate is obtained by increasing the carbon fiber basis weight. Moreover, a low density base material is obtained by reducing the compounding quantity of the resin component with respect to carbon fiber, and a high density base material is obtained by increasing the compounding quantity of the resin component. Moreover, a low density base material is obtained by increasing the thickness of the electrode base material, and a high density base material is obtained by reducing the thickness.

  Here, the density of the electrode base material is obtained by dividing the basis weight (mass per unit area) of the electrode base material weighed using an electronic balance by the thickness of the electrode base material when pressed with a surface pressure of 0.15 MPa. Can be obtained.

In the present invention, the pore diameter of the electrode substrate is required to be in the range of 40 to 70 μm, preferably in the range of 45 to 75 μm, and more preferably in the range of 50 to 70 μm. . When the pore diameter is less than 40 μm, drainage is insufficient and flooding cannot be suppressed. When the pore diameter is larger than 70 μm, the electrical conductivity is insufficient, and the power generation performance decreases at both high and low temperatures. Conventionally, when the density of the electrode substrate is 0.2 g / cm ³ or more in order to suppress dry-up, the pore diameter tends to be small, and it is difficult to make the pore diameter 40 μm or more. In the case where the density of the electrode base material is in the range of 0.2 to 0.4 g / cm ³ , the present inventors have an average diameter of the single fibers of 3 μm or more and 8 μm or less, and an average of the single fibers. It has been found that by including both carbon fibers having a diameter exceeding 8 μm, the pore diameter is set to 40 μm or more, and both flooding suppression and dry-up suppression can be achieved. Here, a substrate having a large pore diameter is obtained by increasing the average diameter of the carbon fibers [B], and a substrate having a small pore diameter is obtained by reducing the average diameter of the carbon fibers [B]. Moreover, a base material with a large pore diameter is obtained by increasing the compounding ratio of the carbon fiber [B] to 100 parts by mass of the carbon fiber [A], and a pore diameter is decreased by decreasing the compounding ratio of the carbon fiber [B]. A small substrate is obtained.

  Here, the pore diameter of the electrode substrate is obtained by determining the peak diameter of the pore diameter distribution obtained by measuring in the measurement pressure range of 6 kPa to 414 MPa (pore diameter 30 nm to 400 μm) by mercury porosimetry. When a plurality of peaks appear, the peak diameter of the highest peak is adopted. As a measuring device, Autopore 9520 manufactured by Shimadzu Corporation or an equivalent product thereof can be used.

  In this invention, it is preferable that the thickness of an electrode base material exists in the range of 150-220 micrometers, and it is more preferable that it exists in the range of 160-200 micrometers. A thickness of 150 μm or more is preferable because the mechanical properties are excellent and the electrolyte membrane and the catalyst layer can be firmly supported. When the thickness is 220 μm or less, the path for drainage is shortened, flooding is improved, and power generation performance at low temperatures is improved.

  Here, the thickness of the electrode base material can be determined using a micrometer in a state where the surface pressure is 0.15 MPa.

In the present invention, it is preferred that the basis weight of the carbon fibers in the electrode substrate is in the range of 20 to 40 g / ^{m 2,} and more preferably in the range of 25 to 35 g / ^{m 2.} It is preferable that the basis weight of the carbon fiber is 20 g / m ² or more because the electrode base material is excellent in mechanical properties, electrical conductivity, and thermal conductivity. When it is 40 g / m ² or less, drainage performance is improved, flooding is improved, and power generation performance at low temperatures is improved.

Here, the basis weight of the carbon fiber in the electrode base material is the weight of the residue obtained by removing the organic matter by holding the paper body cut to 10 cm square in an electric furnace at a temperature of 450 ° C. for 15 minutes in a nitrogen atmosphere. , Divided by the area of the paper body (0.1 m ² ).

  In the present invention, it is not possible to obtain an electrode base material with sufficiently excellent power generation performance over a wide temperature range from low temperature to high temperature only by including the carbon fiber [A] and the carbon fiber [B]. In this case, the density and the pore diameter must be in a specific range.

  Next, a method for obtaining the electrode substrate of the present invention will be described. The electrode base material of the present invention is preliminarily prepared by impregnating 50 to 200 parts by mass of a resin component with respect to 100 parts by mass of carbon fiber in a paper body obtained by papermaking the carbon fiber [A] and the carbon fiber [B]. After the impregnated body is formed, the pre-impregnated body is obtained by carbonization. Hereinafter, further description will be added to each step.

<Paper making body and method for producing paper making body>
In the present invention, in order to obtain a papermaking body containing carbon fibers, a wet papermaking method in which carbon fibers are dispersed in a liquid and a dry yarn making method in which carbon fibers are dispersed in air are used. Of these, the wet papermaking method is preferably used because of its excellent productivity. In particular, before making the carbon fiber [A] and the carbon fiber [B], a step of stirring the aqueous dispersion of the carbon fiber [B] to shorten the carbon fiber [B] is employed. Is preferred. If this process is adopted, it is easy to set the average length of the carbon fiber [B] within the above-described range.

  In the present invention, for the purpose of improving drainage of the electrode base material and suppressing water vapor diffusibility, paper may be made by mixing carbon fibers with organic fibers. As the organic fiber, polyethylene fiber, vinylon fiber, polyacetal fiber, polyester fiber, polyamide fiber, rayon fiber, acetate fiber, cellulose fiber and the like can be used.

  In the present invention, for the purpose of improving the drainage of the electrode substrate and suppressing the water vapor diffusibility, it is preferable to make paper by mixing carbon fibers with fibril-like organic fibers. By mixing the fibrillar organic fibers, the resin component adhering around the fibrillar materials remains as a net-like carbide, and small pores derived from the fibrillar organic fibers and large pores derived from the carbon fibers are formed. it is conceivable that. In the base material of the present invention, in particular, water vapor diffusibility is suppressed, so that power generation performance at high temperatures is improved. Examples of the fibril-like organic fiber include various pulps such as pulp derived from wood such as conifers and hardwoods, pulp derived from non-wood such as straw and kenaf, and pulp derived from synthetic fibers such as polyethylene.

  When pulp is included in the paper body, the pulp content in the paper body is preferably 20 to 80 parts by weight, more preferably 30 to 70 parts by weight, with respect to 100 parts by weight of carbon fiber. Furthermore, it is preferable to set it as 40-60 mass parts. When the blending amount of the pulp is 20 parts by mass or more, water vapor diffusibility is small, dry-up is improved, and high-temperature performance is improved. On the other hand, when the compounding amount of the resin component is 100 parts by mass or less, drainage is improved, flooding is improved, and power generation performance at low temperature is improved.

  In the present invention, an organic polymer can be included as a binder for the purpose of improving the form retainability and handling of the papermaking body. Here, as the organic polymer, polyvinyl alcohol, polyvinyl acetate, polyacrylonitrile, cellulose or the like can be used.

  The paper body in the present invention is preferably in the form of a sheet in which carbon fibers are randomly dispersed in a two-dimensional plane for the purpose of maintaining in-plane conductivity and thermal conductivity isotropic.

<Impregnation of resin component into paper body>
In the present invention, as a method of impregnating the paper component containing carbon fiber with the resin component, a method of immersing the paper component in a solution containing a resin component, a method of applying a solution containing a resin component to a paper component, and a resin component For example, a method of transferring a film on a paper body is used. Especially, since productivity is excellent, the method of immersing a papermaking body in the solution containing a resin component is used preferably.

  The resin component used in the present invention is preferably one that is carbonized during firing to become a conductive carbide. You may add additives, such as a solvent and surfactant, to a resin component as needed.

  The resin component used in the present invention preferably has a carbonization yield of 40% by mass or more. When the carbonization yield is 40% by mass or more, the electrode base material is preferable because it has excellent mechanical properties, electrical conductivity, and thermal conductivity.

  In the present invention, examples of the resin component include thermosetting resins such as phenol resins, epoxy resins, melamine resins, and furan resins. Of these, a phenol resin is preferably used because of its high carbonization yield.

  In this invention, it is necessary to mix | blend 50-200 mass parts of resin components with respect to 100 mass parts of carbon fibers, and it is preferable to impregnate 60-150 mass parts, and also 70-100 mass parts to the said papermaking body. It is preferable to mix. When the blending amount of the resin component is 50 parts by mass or more, the electrode base material is preferable because it has excellent mechanical properties, electrical conductivity, and thermal conductivity. On the other hand, when the compounding amount of the resin component is 200 parts by mass or less, drainage is improved, flooding is improved, and power generation performance at low temperature is improved.

  In the present invention, it is preferable to add carbonaceous powder to the resin component from the viewpoint of improving the mechanical properties, conductivity, and thermal conductivity of the electrode substrate. Here, as the carbonaceous powder, carbon black, carbon nanotube, carbon nanofiber, milled fiber of carbon fiber, graphite or the like can be used. Among these, it is preferable to use graphite because the mechanical properties, conductivity, and thermal conductivity are improved and the amount of the resin component is reduced. By reducing the amount of the resin component, drainage is improved, flooding is improved, and power generation performance at low temperatures is improved. Examples of the graphite include flaky graphite, earthy graphite, artificial graphite, expanded graphite, and spherical graphite. Of these, scale-like graphite is preferably used because of its high effect of improving mechanical properties, conductivity, and thermal conductivity.

  The amount of carbonaceous powder added to the resin component is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, and 5 to 12 parts by mass with respect to 100 parts by mass of the resin component. More preferably, it is a part. It is preferable for the amount of carbonaceous powder added to be 5 parts by mass or more because the electrode base material has excellent mechanical properties, electrical conductivity, and thermal conductivity. On the other hand, when the addition amount of the carbonaceous powder is 20 parts by mass or less, the flexibility of the electrode base material is increased, and the productivity is excellent, which is preferable.

  In the present invention, when the resin component is impregnated into the paper body, the resin component can be used as it is, or, if necessary, mixed with various solvents for the purpose of improving the impregnation property into the paper body. It can also be used. Here, methanol, ethanol, isopropyl alcohol, or the like can be used as the solvent.

  The resin component is preferably liquid at 25 ° C. and 0.1 MPa. Alternatively, a solvent may be added to the resin component to form a resin composition, and the resin composition may be liquid at 25 ° C. and 0.1 MPa. It is preferable that the resin component (resin composition in the case of using a solvent) is in a liquid state because the paper body has excellent impregnation properties and the electrode base material has excellent mechanical properties, electrical conductivity, and thermal conductivity.

<Lamination and heat treatment of pre-impregnated body>
In the present invention, after forming a pre-impregnated body impregnated with a resin component on a paper body, prior to carbonization, a plurality of pre-impregnated bodies may be bonded together for the purpose of making the electrode substrate a predetermined thickness. The pre-impregnated body can be heat-treated for the purpose of thickening and partially crosslinking the resin component.

  When a plurality of pre-impregnated bodies are laminated, a plurality of pre-impregnated bodies having the same properties can be laminated, or a plurality of pre-impregnated bodies having different properties can be laminated. Specifically, a pre-impregnated body obtained by adding and impregnating carbonaceous powder to the resin component and a pre-impregnated body obtained by impregnating the resin component without adding carbonaceous powder can be bonded together. . In addition, a plurality of pre-impregnated bodies having different average diameters and average lengths of carbon fibers, carbon fiber basis weight of the papermaking body, blending amount of organic fibers, impregnation amount of resin component, blending amount of carbonaceous powder, and the like may be bonded together. it can.

In the present invention, it is preferred that the basis weight of the carbon fibers in the substrate after bonding the pre-impregnated material is in the range of 20 to 40 g / m ^2, and more preferably in the range of 25 to 35 g / m ² . It is preferable that the basis weight of the carbon fiber is 20 g / m ² or more because the electrode base material is excellent in mechanical properties, electrical conductivity, and thermal conductivity. When it is 40 g / m ² or less, drainage performance is improved, flooding is improved, and power generation performance at low temperatures is improved.

  In the present invention, for the purpose of heat-treating the pre-impregnated body for the purpose of thickening and partially cross-linking the resin component or the resin composition, a method of spraying hot air, heating between hot plates of a press device, etc. The method of heating, the method of heating between continuous belts, etc. can be used.

<Carbonization>
In the present invention, the pre-impregnated body is bonded together as necessary, heat treated, and then carbonized. Carbonization is usually by firing in an inert atmosphere. For this firing, a batch type heating furnace can be used, or a continuous type heating furnace can be used. The inert atmosphere can be obtained by flowing an inert gas such as nitrogen gas or argon gas in the furnace.

  In the present invention, the maximum temperature of firing is preferably in the range of 1500 to 3000 ° C, more preferably in the range of 1700 to 3000 ° C, and further in the range of 1900 to 3000 ° C. preferable. When the maximum temperature is 1500 ° C. or higher, the carbonization of the resin component proceeds, and the electrode base material is preferably excellent in conductivity and thermal conductivity. On the other hand, the maximum temperature of 3000 ° C. or lower is preferable because the operating cost of the heating furnace is reduced.

  In the present invention, the firing rate is preferably in the range of 80 to 5000 ° C./min for firing. A temperature increase rate of 80 ° C. or higher is preferable because productivity is excellent. On the other hand, when the temperature is 5000 ° C. or lower, the carbonization of the resin component gradually proceeds and a dense structure is formed. Therefore, the electrode base material is preferably excellent in conductivity and thermal conductivity.

<Post-processing>
The electrode substrate is preferably subjected to water repellent treatment for the purpose of improving drainage. The water repellent finish can be performed by applying a hydrophobic resin to the electrode substrate after carbonization and heat-treating it. Examples of the hydrophobic resin include polychlorotrifluoroethylene resin (PCTFE), polytetrafluoroethylene resin (PTFE), polyvinylidene fluoride resin (PVDF), a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), tetra Examples thereof include fluororesins such as a copolymer of fluoroethylene and perfluoropropyl vinyl ether (PFA) and a copolymer of tetrafluoroethylene and ethylene (ETFE). The application amount of the hydrophobic resin is preferably 1 to 50 parts by mass, and more preferably 3 to 40 parts by mass with respect to 100 parts by mass of the electrode substrate. When the application amount of the hydrophobic resin is 1 part by mass or more, the electrode substrate is preferable because it has excellent drainage. On the other hand, when the amount is 50 parts by mass or less, the electrode base material is preferably excellent in conductivity.

  In the present invention, it is preferable to form a microporous layer having conductivity, a so-called microporous layer, on at least one surface of the electrode substrate that has been subjected to water repellent finishing. When the microporous layer is provided, the surface unevenness of the water-repellent electrode base material is covered and smoothed. Therefore, when the membrane-electrode assembly is configured and the fuel cell is configured, the electric resistance between the catalyst layer and the electrode layer Can be reduced. In addition, damage to the solid polymer electrolyte membrane can be prevented more reliably. The microporous layer can be formed by applying a mixture of the hydrophobic resin used in the above-described water-repellent processing and the above-mentioned carbon filler to the surface of the water-repellent electrode base material. Carbon black is preferably used as the carbon filler. In this invention, it is preferable to mix | blend 1-70 mass parts of hydrophobic resin with respect to 100 mass parts of carbon fillers in a microporous layer, and it is more preferable to mix | blend 5-60 mass parts. When the blending amount of the hydrophobic resin is 1 part by mass or more, the microporous layer is preferable because it has excellent mechanical strength. On the other hand, when the amount is 70 parts by mass or less, the microporous layer is preferable because it has excellent conductivity and thermal conductivity.

  A membrane-electrode assembly is constructed by bonding the electrode substrate of the present invention to at least one surface of a solid polymer electrolyte membrane having catalyst layers on both sides. In addition, when using the water-repellent processed electrode base material provided with the microporous layer, it is preferable to configure the membrane-electrode assembly so that the microporous layer is in contact with the catalyst layer. A polymer electrolyte fuel cell can be constructed by laminating a plurality of such membrane-electrode assemblies sandwiched between separators via gaskets. The catalyst layer is composed of a layer containing a solid polymer electrolyte and catalyst-supporting carbon. As the catalyst, platinum is usually used. In a fuel cell in which a reformed gas containing carbon monoxide is supplied to the anode side, it is preferable to use platinum and ruthenium as the catalyst on the anode side. As the solid polymer electrolyte, it is preferable to use a perfluorosulfonic acid polymer material having high proton conductivity, oxidation resistance, and heat resistance. Such a fuel cell unit and the configuration of the fuel cell itself are well known.

  Hereinafter, the present invention will be described specifically by way of examples. The electrode substrate measurement method, fuel cell performance evaluation method, and materials are shown below.

<Measurement of electrode substrate thickness>
The thickness of the electrode substrate was determined using a micrometer in a state where the electrode substrate was pressurized at a surface pressure of 0.15 MPa.

<Measurement of carbon fiber basis weight in electrode substrate>
The basis weight of the carbon fiber in the electrode substrate is that the paper body cut out in a 10 cm square is held in an electric furnace at a temperature of 450 ° C. for 15 minutes in a nitrogen atmosphere, and the weight of the residue obtained by removing the organic matter is determined as the paper body. Divided by the area (0.1 m ² ).

<Density measurement of electrode substrate>
The density of the electrode base material is obtained by dividing the basis weight of the electrode base material to be measured by the thickness when pressed with a surface pressure of 0.15 MPa.

<Measurement of pore diameter of electrode substrate>
The pore diameter of the electrode base material is obtained by determining the peak diameter of the pore diameter distribution obtained by measuring in the measurement pressure range of 6 kPa to 414 MPa (pore diameter 30 nm to 400 μm) by mercury porosimetry. When multiple peaks appeared, the peak diameter of the highest peak was adopted. As a measuring device, Autopore 9520 manufactured by Shimadzu Corporation was used.

<Evaluation of power generation performance of polymer electrolyte fuel cells>
1.00 g of platinum-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum support: 50% by mass), 1.00 g of purified water, “Nafion” (registered trademark) solution (“Nafion” (registered trademark) 5 manufactured by Aldrich) (0.0 mass%) 8.00 g and isopropyl alcohol (manufactured by Nacalai Tesque) 18.00 g were sequentially added to prepare a catalyst solution.

Next, “Naflon” (registered trademark) PTFE tape “TOMBO” (registered trademark) No. 7 cut to 7 cm × 7 cm. A catalyst solution was applied to 9001 (manufactured by NICHIAS Corporation) by spraying and dried at room temperature to prepare a PTFE sheet with a catalyst layer having a platinum amount of 0.3 mg / cm ² . Subsequently, a solid polymer electrolyte membrane “Nafion” (registered trademark) NR-211 (manufactured by DuPont) cut to 10 cm × 10 cm is sandwiched between two PTFE sheets with a catalyst layer, and pressed to 5 MPa with a flat plate press. Pressing at 5 ° C. for 5 minutes transferred the catalyst layer to the solid polymer electrolyte membrane. After pressing, the PTFE sheet was peeled off to produce a solid polymer electrolyte membrane with a catalyst layer.

  Next, the solid polymer electrolyte membrane with a catalyst layer is sandwiched between electrode substrates having two microporous layers cut into 7 cm × 7 cm, and pressed at 130 ° C. for 5 minutes while being pressed to 3 MPa with a flat plate press, A membrane-electrode assembly was produced. In addition, the electrode base material provided with the microporous layer was arrange | positioned so that the surface which has a microporous layer may contact the catalyst layer side.

The obtained membrane-electrode assembly was incorporated into a single cell for fuel cell evaluation together with a serpentine-type separator having a single flow path having a groove width of 1.5 mm, a groove depth of 1.0 mm, and a rib width of 1.1 mm. Was used to evaluate the power generation performance. First, the output voltage was measured when the operating temperature was held at 65 ° C. and the current density was set at 2.0 A / cm ^3, and used as an indicator of low temperature performance. Next, the current density is set to 1.2 A / cm ³ , the operating temperature is maintained from 80 ° C. for 5 minutes, the output voltage is measured while repeatedly raising 2 ° C. over 5 minutes, and the limit temperature at which power generation is possible is determined Used as an index of high temperature performance.
Here, hydrogen pressurized to 210 kPa was supplied to the anode side, and air pressurized to 140 kPa was supplied to the cathode side, and the evaluation was performed at an operating temperature of 65 ° C. Both hydrogen and air were humidified using a humidification pot set at 70 ° C. The utilization rates of hydrogen and oxygen in the air were 80% and 67%, respectively.

<Measurement of breaking load of paper body>
A paper body having a width of 50 mm was gripped by a tensile test jig attached to an autograph with a span length of 250 mm, pulled at a speed of 2 to 4 mm / min until breaking, and the maximum load was measured. When the breaking load is low, the papermaking body or the pre-impregnated body is broken and difficult to obtain. Therefore, it is preferably 100N or more, and more preferably 120N or more. In the case of a continuous long sheet, the breaking load in the longitudinal direction only needs to satisfy the above value.

<Material>
Carbon fiber [A]
A-1: PAN-based carbon fiber “Torayca” (registered trademark) T300-3K
Toray Industries, Inc., average diameter of single fiber: 7μm, average length: 12mm (cut product)
Other fine carbon fiber A-2: PAN-based carbon fiber “Torayca” (registered trademark) T300-3K
Toray Industries, Ltd., average diameter of single fiber: 7μm, average length: 1.0mm (cut product)
Carbon fiber [B]
B-1: Pitch-based carbon fiber “Donna Carbo Chop” (registered trademark) S332
Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 18 μm, average length: 5.5 mm
B-2: Pitch-based carbon fiber “Donna Carbo” (registered trademark) S232
Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 13 μm, average length: 5.5 mm
B-3: Pitch-based carbon fiber “Donna Carbo” (registered trademark) S234
Made by Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 10 μm, average length: 10 mm
B-4: Pitch-based carbon fiber “Donna Carbo” (registered trademark) S331
Made by Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 18 μm, average length: 3.3 mm
B-5: Pitch-based carbon fiber “Donna Carbo” (registered trademark) S331
Made by Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 18 μm, average length: 1.0 mm
[B] The material (B-4) was dispersed in water and stirred for 15 minutes with a mixer.
Other high-definition carbon fiber B-6: Pitch-based carbon fiber “Donna Carbon” (registered trademark) S331
Made by Osaka Gas Chemical Co., Ltd., average diameter of single fiber: 18 μm, average length: 0.4 mm
[B] The material (B-4) was dispersed in water and stirred for 30 minutes with a mixer.
Pulp [C]
Hardwood bleached kraft pulp "LBKP" craft market pulp (Hardwood)
Made by Alabama River Pulp, average length: 0.8mm
Binder [D]
PVA (polyvinyl alcohol)
Thermosetting resin [E]
E-1: Resol type phenol resin KP-743K
E-2 manufactured by Arakawa Chemical Industries, Ltd .: Novolac-type phenolic resin “Tamanor” (registered trademark) 759
Arakawa Chemical Industries, Ltd. carbonaceous powder [F]
F-1: Scaly graphite BF-5A
Made by Chuetsu Graphite Industries Co., Ltd., average particle size: 5 μm
F-2: Carbon black “Denka Black” (registered trademark)
Electrochemical Industry Co., Ltd. Solvent [G]
Methanol Nacalai Tesque Co., Ltd. hydrophobic resin [H]
PTFE resin “Polyfluorocarbon” (registered trademark) PTFE dispersion D-1E
Surfactant [I] manufactured by Daikin Industries, Ltd.
Surfactant “TRITON” (registered trademark) X-100
Made by Nacalai Tesque ( Reference Example 1 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Process for producing paper body The above-mentioned [A] material (A-1) and [B] material (B-1) are mixed at a weight ratio of 70:30 and dispersed in water to obtain a wet papermaking method. The paper was made continuously. Further, a 10% by mass aqueous solution of the above [D] material was applied and dried to prepare a carbon fiber papermaking body. The coating amount of polyvinyl alcohol was 25 parts by mass with respect to 100 parts by mass of the paper body. The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted to be 20. When the breaking load of the paper body was measured, it was 180 N, and the breaking load of the paper body was very good.
-Step II: Step of adjusting the mixed resin composition Using the above-mentioned [E] material and [F] material with respect to 100 parts by weight of carbon fiber in the paper body, the composition ratio (E-1) / ( E-2) / (F-1) = Adjust the concentration with the material [G] so as to be 45/45/10, and stir for 1 minute using an ultrasonic dispersion device to obtain a uniformly dispersed resin composition. Obtained.
-Step III: Preparation, pasting and heat treatment of pre-impregnated body A paper body cut to 9 cm x 12.5 cm is immersed in a mixed resin composition filled with aluminum bat, and the paper body is impregnated with the mixed resin composition Then, it was heated at 100 ° C. for 3 minutes and dried to prepare a pre-impregnated body. Next, two pre-impregnated bodies were laminated and heat-treated at 180 ° C. for 6 minutes while being pressed with a flat plate press. In addition, a spacer was disposed on the flat plate press during the pressurization, and the interval between the upper and lower press face plates was adjusted so that the thickness of the pre-impregnated body after the heat treatment was 200 μm.
-IV process: Electrode base material preparation process The base material which heat-processed the pre-impregnation body was baked and carbonized by nitrogen gas atmosphere in the heating furnace, and the electrode base material was obtained. Here, the firing conditions were as follows.
(B) Temperature rise from room temperature to 2400 ° C. at a rate of temperature rise of 500 ° C./min (b) Hold at 2400 ° C. for 5 minutes (c) Allow to cool from 2400 ° C. to room temperature Step V: Water repellent electrode substrate Production and Step of Forming Microporous Layer The electrode substrate was immersed in a 2.5% aqueous solution of [H] material, and then heated and dried at 100 ° C. for 3 minutes to produce a water repellent electrode substrate. Next, a carbon coating solution layer having a thickness of 50 μm was formed on the water repellent electrode substrate using a coater. The carbon coating liquid used here was (F-2) of the [F] material, [H] material, [I] material, and purified water, and the blending ratio was 7.7 parts by mass / 2.5 parts by mass / What was adjusted so that it might become 1.8 mass parts / 88 mass parts was used. The water-repellent electrode substrate on which the carbon coating layer was formed was dried at 100 ° C. for 10 minutes and then heated at 380 ° C. for 10 minutes to produce a water-repellent electrode substrate on which a microporous layer was formed.

Subsequently, as a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.25 g. / Cm ³ , the pore diameter is 51 μm, and the result of the power generation performance of the electrode base material with this characteristic is an output voltage of 0.45 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit The temperature was 88 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 1, Reference Example 1 was good in both low temperature performance and high temperature performance.

( Reference examples 2 and 3)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
[A] material in Reference Example 1 Step (A-1) and [B] material (B-1) a weight ratio of as shown in Table 1 50:50 (Example 2), 30: 70 (Reference Example 3 The papermaking body was obtained in the same manner as in Reference Example 1 except that the mixture was mixed in step 1 ).
The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted. As a result, the number of paper bodies of Reference Example 2 was 25 and the number of paper bodies of Reference Example 3 was 15. When the breaking load of the paper body was measured, the paper body of Reference Example 2 was good at 140 N, but the paper body of Reference Example 3 was relatively good at 105 N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
It was the same as Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode base material on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode base material was 30 g / m ² , the density was 0.24, and. 25 g / cm ³ , pore diameters of 58 and 63 μm, and the results of power generation performance of the electrode base material having this characteristic are output voltages of 0.47 and 0.48 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2. 0 A / cm ³ ) and the limiting temperatures were 90 and 86 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 1, Reference Example 2 had good low temperature performance and extremely high temperature performance, and Reference Example 3 had very good low temperature performance and relatively good high temperature performance.

( Reference Examples 4 and 5)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
In the step of Reference Example 1, the weight ratio of [A] material (A-1) and [B] material (B-2), [A] material (A-1) and [B] material (B-3) was 70. : A papermaking body was obtained in the same manner as in Reference Example 1 except that mixing was performed at 30. The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted. As a result, it was 20 for the paper body of Reference Example 4 and 25 for the paper body of Reference Example 5 . When the breaking load of the paper body was measured, the paper body of Reference Example 4 was very good at 190N, and the paper body of Reference Example 5 was very good at 210N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate with a microporous layer formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.25 g / cm ^3. The pore diameter was 47 and 44 μm, and the results of the power generation performance of the electrode base material having this characteristic were output voltages of 0.44 and 0.43 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ^3). ), The limiting temperature was 88 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 1, Reference Example 4 was good in both low temperature performance and high temperature performance, and Reference Example 5 was relatively good in low temperature performance and good in high temperature performance.

( Reference Example 6 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The same as Reference Example 2 .
-Step II: Step of adjusting the mixed resin composition
In the process of Reference Example 1 , it was the same as Reference Example 1 except that the composition ratio (E-1) / (E-2) / (F-1) = 90/90/10.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 180 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.36 g / cm ^3. The pore diameter is 49 μm, and the result of the power generation performance of the electrode base material having this characteristic is an output voltage of 0.42 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 90 ° C. (Humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 1, Reference Example 6 had relatively good low temperature performance and very good high temperature performance.

( Reference Examples 7-9 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The same as Reference Example 2 . In Reference Example 9, since the carbon fiber basis weight of the electrode base material was increased, the surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was 30. When the breaking load of the paper body was measured, the paper body of Reference Example 9 was very good at 195N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
In the step of Reference Example 1, the procedure was the same as Reference Example 1 except that the distance between the upper and lower press face plates was adjusted so that the thickness of the pre-impregnated body after heat treatment was 150 to 250 μm.
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 140 to 230 μm, the carbon fiber basis weight of the electrode substrate was 30 to 42 g / m ² , and the density was 0.1. 21 to 0.36 g / cm ³ and a pore diameter in the range of 45 to 61 μm are obtained, and the results of power generation performance of the electrode base material having these characteristics are output voltages of 0.42 to 0.46 V (operation temperature 65 ° C. , Humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 84 to 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Reference Example 7 has good low temperature performance and high temperature performance, Reference Example 8 has good low temperature performance and relatively good high temperature performance, and Reference Example 9 has relatively low temperature performance. Good and high temperature performance was very good.

( Reference Example 10 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The same as Reference Example 2 .
-Step II: Step of adjusting the mixed resin composition
In the step of Reference Example 1, the procedure was the same as Reference Example 1 except that the composition ratio (E-1) / (E-2) / (F-1) = 45/45/0.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.23 g / cm ^3. The pore diameter is 56 μm, and the results of power generation performance of the electrode base material having this characteristic are output voltage 0.42 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 84 ° C. (Humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Reference Example 10 had relatively low temperature performance and relatively high temperature performance.

( Reference Example 11 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The same as Reference Example 2 .
-Step II: Step of adjusting the mixed resin composition
In the step of Reference Example 1, the procedure was the same as Reference Example 1 except that the composition ratio (E-1) / (E-2) / (F-2) = 45/45/10.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate with a microporous layer formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.25 g / cm ^3. The pore diameter is 54 μm, and the results of power generation performance of the electrode base material having this characteristic are output voltage 0.44 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 86 ° C. (Humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Reference Example 11 had good low temperature performance and relatively high temperature performance.

( Reference Example 12 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
Except mixing the weight ratio of [A] material (A-1), [B] material (B-1), and [C] material by 50:50:50 in the process of the reference example 1 as shown in Table 2. A paper body was obtained in the same manner as in Reference Example 1 . The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted to be 10. When the breaking load of the paper body was measured, the paper body of Reference Example 12 was extremely good at 170 N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.37 g / cm ^3. The pore diameter is 56 μm, and the result of the power generation performance of the electrode base material having this characteristic is that the output voltage is 0.47 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), and the limit temperature is any Was 92 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Reference Example 12 was very good in both low temperature performance and high temperature performance.

( Reference Examples 13 and 14 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
As shown in Table 2, the weight ratio of [A] material (A-1), [B] material (B-1), and [C] material in the process of Reference Example 1 was 50:50:50 ( Reference Example 13 ), A paper body was obtained in the same manner as in Reference Example 1 except that mixing was performed at 50:50:90 ( Reference Example 14 ). The surface of the paper body was observed with a microscope, 10 pieces in the paper body of Reference Example 1 3 was counted unity contained within a circle of diameter 7.5 cm, the paper body of Reference Example 14 was nine. When the breaking load of the paper body was measured, the paper body of Reference Example 13 was very good at 170 N, and the paper body of Reference Example 14 was very good at 190 N.
-Step II: Step of adjusting the mixed resin composition
The same as Reference Example 6 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode base material on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode base material was 30 g / m ² , the density was 0.37 and 0.00. 39 g / cm ³ , pore diameters of 47 and 42 μm, and the results of power generation performance of the electrode base material having this characteristic are output voltages of 0.43 and 0.42 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2. 0 A / cm ³ ) and the limiting temperatures were both 92 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Reference Examples 13 and 14 had relatively good low-temperature performance and very good high-temperature performance.

( Example 1 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
Except mixing the weight ratio of [A] material (A-1), [B] material (B-4), and [C] material by 50:50:50 in the process of the reference example 1 as shown in Table 2. A paper body was obtained in the same manner as in Reference Example 1 . When the surface of the paper body was observed with a microscope and the bundles contained in a circle having a diameter of 7.5 cm were counted, the number was 2 and the surface condition was very good. When the breaking load of the paper body was measured, the paper body of Example 1 was very good at 165N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.37 g / cm ^3. The pore diameter is 56 μm, and the result of power generation performance of the electrode base material having this characteristic is that the output voltage is 0.47 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), and the limit temperature is 92 The temperature was 70 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Example 1 was very good in both low temperature performance and high temperature performance.

( Example 2 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
Except mixing the weight ratio of [A] material (A-1), [B] material (B-5), and [C] material by 50:50:50 in the process of the reference example 1 as shown in Table 2. A paper body was obtained in the same manner as in Reference Example 1 . When the surface of the paper body was observed with a microscope and the number of bundles contained in a circle having a diameter of 7.5 cm was counted, it was 0, and the surface condition was extremely good. When the breaking load of the paper body was measured, the paper body of Example 2 was very good at 160 N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.37 g / cm ^3. The pore diameter is 56 μm, and the result of power generation performance of the electrode base material having this characteristic is that the output voltage is 0.47 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), and the limit temperature is 92 The temperature was 70 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 2, Example 2 was extremely good in both low temperature performance and high temperature performance.

( Examples 3 and 4 )
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
Table 3 shows [A] material (A-1) and [B] material (B-4), and [A] material (A-1) and [B] material (B-5) in the process of Reference Example 1. A paper body was obtained in the same manner as in Reference Example 1 except that the mixing was performed at 50:50. When the surface of the paper body was observed with a microscope and the number of bundles contained in a circle having a diameter of 7.5 cm was counted, it was 12 for the paper body of Example 3 and 11 for the paper body of Example 4 . When the breaking load of the paper body was measured, the paper body of Example 3 was good at 135N, and the paper body of Example 4 was good at 130N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.24 g / cm ^3. The pore diameter is 58 μm, and the results of the power generation performance of the electrode base material with this characteristic are both output voltage 0.47 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), and the limit temperature is Both were 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 3, the low temperature performance was good and the high temperature performance was very good.

(Comparative Example 1)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The [A] material in Reference Example 1 Step a (A-1) except that the paper with 100% as shown in Table 3 to obtain a paper body in the same manner as in Reference Example 1. The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted. When the breaking load of the paper body was measured, the paper body of Comparative Example 1 was very good at 225N.
-Step II: Step of adjusting the mixed resin composition
It was equivalent to Reference Example 10 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
It was the same as Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.23 g / cm ^3. The pore diameter is 39 μm, and the result of the power generation performance of the electrode base material having this characteristic is an output voltage of 0.38 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 84 ° C. It was found that the humidification temperature was 70 ° C. and the current density was 1.2 A / cm ² . The results are shown in Table 4.

(Comparative Example 2)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
Step I: Process for producing paper body The same as Comparative Example 1.
-Step II: Step of adjusting the mixed resin composition
In the step of Reference Example 1, the procedure was the same as Reference Example 1 except that the composition ratio (E-1) / (E-2) / (F-1) = 90/90/0.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
It was the same as Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.38 g / cm ^3. The pore diameter is 32 μm, and the result of the power generation performance of the electrode base material having this characteristic is an output voltage of 0.32 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), limit temperature 88 ° C. (Humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 4, Comparative Example 2 had good high temperature performance.

(Comparative Example 3)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
A paper body was obtained in the same manner as in Reference Example 1 except that [B] material (B-1) was made at 100% as shown in Table 3 in the step of Reference Example 1 . The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted. When the breaking load of the paper body was measured, the paper body of Comparative Example 3 had an extremely low value of 60N.
Step II: Mixed resin composition preparation step The same as Comparative Example 1.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
It was the same as Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .
As a result of evaluating the characteristics using the obtained water-repellent electrode substrate with a microporous layer formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , and the density was 0.26 g / cm ^3. The pore diameter was 68 μm, and the electrode base material having this characteristic caused base material cracking, and the output voltage and limit temperature data could not be obtained. It described in Table 4.

(Comparative Examples 4 and 5)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
The same as in Reference Example 1 .
-Step II: Step of adjusting the mixed resin composition
In the step of Reference Example 1 , the same as in Reference Example 1 except that the composition ratio (E-1) / (E-2) / (F-1) = 20/20/10 and 140/140/10 did.
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate with a microporous layer formed, the thickness was 170 μm, the carbon fiber basis weight of the electrode substrate was 30 g / m ² , the density was 0.18 and 0.00. 42 g / cm ³ , pore diameters of 46 and 28 μm, and the results of power generation performance of the electrode base material with this characteristic were an output voltage of 0.38 V and power generation impossible (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A) / Cm ³ ), limit temperature 82 and 90 ° C. (humidification temperature 70 ° C., current density 1.2 A / cm ² ). As shown in Table 4, Comparative Example 5 had very high temperature performance.

(Comparative Example 6)
A water-repellent electrode base material having a microporous layer was produced through the following steps I to V.
-Step I: Paper body production process
A paper body was obtained in the same manner as in Reference Example 1 except that B-6 was used instead of [B] material (B-1) in the step of Reference Example 1 . The surface of the paper body was observed with a microscope, and the number of bundles contained in a circle having a diameter of 7.5 cm was counted to be 10. When the breaking load of the paper body was measured, the paper body of Comparative Example 6 was good at 150 N.
-Step II: Step of adjusting the mixed resin composition
The same as in Reference Example 1 .
Step III: Preparation of pre-impregnated body, bonding, and heat treatment process
The same as in Reference Example 1 .
-Step IV: Electrode substrate production process
The same as in Reference Example 1 .
-Step V: Production of water repellent electrode substrate, formation of microporous layer
The same as in Reference Example 1 .

As a result of evaluating the characteristics using the obtained water-repellent electrode substrate on which a microporous layer was formed, the average length of the [B] material (B-6) was too short, so that the [B] material (B -6) was removed from the paper body together with water, the thickness was 120 μm, the carbon fiber basis weight of the electrode substrate was 21 g / m ² , the density was 0.23 g / cm ³ , and the pore diameter was 39 μm. As a result of the power generation performance of the electrode base material having this characteristic, the output voltage is 0.36 V (operation temperature 65 ° C., humidification temperature 70 ° C., current density 2.0 A / cm ³ ), the limit temperature is 82 ° C. (humidification temperature 70 ° C., current The density was found to be 1.2 A / cm ² ).

(Comparative Example 7)
-Step I: Paper body production process
Using A-2 instead of [A] material (A-1) in Reference Example 2 Step, [B] material except for using B-6 in place of (B-1) is the same as in Reference Example 2 Paper was made by the method. Since both the fiber lengths of A-2 and B-6 were short, the base material was broken in the papermaking process, and a papermaking body could not be obtained.

Claims (7)

A gas diffusion electrode base material obtained by binding carbon fibers of the following [A] and [B] with carbides, having a density in the range of 0.2 to 0.4 g / cm ³ and a pore diameter of 40 to A gas diffusion electrode substrate characterized by being in the range of 70 μm.
[A] Carbon fiber having an average diameter of a single fiber of 3 μm to 8 μm and an average length of 4 to 20 mm [B] The average diameter of the single fiber is more than 8 μm and 30 μm or less, and the average length is 0.5 carbon fiber of ~ 4 mm The gas diffusion electrode substrate according to claim 1, wherein the thickness is in the range of 150 to 220 µm. Gas diffusion electrode substrate according to claim 1 or 2 carbon fiber weight per unit area of the electrode substrate is in the range of 20 to 40 g / m ^2. The gas diffusion electrode substrate according to any one of claims 1 to 3 , comprising carbonaceous powder. A pre-impregnated body is formed by impregnating 50 to 200 parts by mass of a resin component with respect to 100 parts by mass of carbon fiber in a paper body obtained by papermaking the carbon fiber [A] and the carbon fiber [B]. The method for producing a gas diffusion electrode substrate according to any one of claims 1 to 4 , wherein the impregnated body is carbonized. The method for producing a gas diffusion electrode substrate according to claim 5 , wherein the papermaking body contains 10 to 100 parts by mass of pulp with respect to 100 parts by mass of carbon fiber. Before paper the carbon fibers [B] and the carbon fibers [A], wherein stirring the aqueous dispersion of the carbon fibers [B], claim 5 comprising a step of fiber shortening the carbon fiber [B] Or a method for producing a gas diffusion electrode substrate according to 6 .