Precursor sheet for fuel cell separator

Abstract

This precursor sheet for a fuel cell separator contains graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin. The precursor sheet can be reverted to a slurry in an aqueous solvent, and thus it is possible to reuse defective articles and waste material generated during processing.

Description

Precursor sheet for fuel cell separator

[0001] The present invention relates to a precursor sheet for a fuel cell separator, and more particularly to a precursor sheet for a fuel cell separator that can be reslurried and reused.

[0002] Fuel cell separators provide electrical conductivity to each unit cell, ensure passage for fuel and air (oxygen) to be supplied to the unit cells, and serve as a boundary wall separating them. Generally, fuel cell separators are required to have properties such as gas (hydrogen and oxygen) impermeability, electrical conductivity, mechanical strength, durability (heat resistance, water resistance, acid resistance), thin and lightweight, and formability.

[0003] A conventional method for producing such fuel cell separators involves heat-compression molding a sheet-shaped separator precursor. For example, Patent Document 1 discloses a fuel cell separator obtained by compression molding a fuel cell separator precursor sheet, the fuel cell separator precursor sheet including a conductive substrate sheet, a dense layer containing first graphite particles having a predetermined bulk density and volume resistivity (conductivity), and a conductive layer containing second graphite particles having a predetermined bulk density and volume resistivity, the dense layer and the conductive layer comprising a resin. Patent Document 2 discloses a fuel cell separator obtained by heat-molding a stampable sheet containing a conductive filler and a polymer material in a molding machine equipped with a pair of molds engraved with the shape of the fuel cell separator.

[0004] Thus, although there have been many separator manufacturing techniques using sheet-shaped precursors, no method has been known to easily reuse the sheet-shaped precursor (by forming a slurry) in an aqueous solvent. For example, Patent Document 1 discloses that the conductive layer can be produced using a conductive layer-forming composition containing a water-soluble resin binder, graphite, and a resin. However, because the conductive layer is impregnated with a water-insoluble resin solution dissolved in a solvent, the water-insoluble resin solution coats the graphite, causing it to fuse. This makes it difficult to redissolve or reslurry the precursor in an aqueous solvent for reuse. Patent Document 2 also uses a stampable sheet produced by a papermaking process from a suspension containing a conductive filler and a polymer material. However, the sheet is dried at a high temperature and then compressed by a press. This causes the polymer particles to fuse together and the polymer material to the conductive filler, making it difficult to redissolve or reslurry the precursor in an aqueous solvent for reuse. Furthermore, neither document mentions the reuse of the sheet-shaped precursor.

[0005] Furthermore, Patent Document 3 discloses a coating composition for use in a current collector plate with a coating layer for a fuel cell, which contains a carbon material, a water-soluble resin binder, a water-dispersible resin particulate binder, and an aqueous liquid medium. Patent Document 4 discloses a coating composition for use in a separator with a coating layer for a fuel cell, which contains a carbon material, a water-soluble resin binder, a water-dispersible resin particulate binder, and an aqueous liquid medium. However, the compositions of Patent Documents 3 and 4 are coating compositions for coating the surface of a current collector plate or separator, but are not precursor sheets for fuel cell separators. Furthermore, the above coating compositions are not formed into a sheet for use as separator precursors, and because they form a water-resistant coating film after application and drying, they cannot be redissolved in an aqueous solvent or reslurried for reuse.

[0006] Japanese Patent No. 7056796 Japanese Patent Application Laid-Open No. 2006-269313 Japanese Patent Application Laid-Open No. 2016-183325 Japanese Patent Application Laid-Open No. 2016-81717

[0007] The present invention has been made in consideration of these circumstances, and aims to provide a precursor sheet for a fuel cell that can be reslurried into an aqueous solvent, thereby allowing for the reuse of defective products produced during manufacturing and scraps generated during processing.

[0008] As a result of extensive research to achieve the above-mentioned object, the inventors discovered that a precursor sheet for a fuel cell separator containing graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin can be reslurried in an aqueous solvent, and therefore defective products generated during manufacturing and scraps generated during processing can be easily reused, thereby completing the present invention.

[0009] That is, the present invention provides: 1. a precursor sheet for a fuel cell separator comprising graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin; 2. a precursor sheet for a fuel cell separator according to item 1, having a structure in which the graphite particles and the particulate or fibrous water-insoluble resin are fixed by the water-soluble resin; 3. a precursor sheet for a fuel cell separator according to item 1, in which the content of the water-soluble resin is 0.1 to 30.0 parts by mass per 100 parts by mass of the graphite particles, and the content of the particulate or fibrous water-insoluble resin is 10.0 to 70.0 parts by mass per 100 parts by mass of the graphite particles; 4. a precursor sheet for a fuel cell separator according to item 1, comprising carbon fiber; and 5. a fuel cell separator formed from the precursor sheet for a fuel cell separator according to any one of items 1 to 4.

[0010] The fuel cell separator precursor sheet of the present invention can be reslurried in an aqueous solvent, and defective products during production or scrap materials during processing can be reslurried and reprocessed into a sheet, thereby reducing losses during production. Furthermore, fuel cell separators obtained using the fuel cell separator precursor sheet of the present invention have excellent electrical conductivity and gas impermeability.

[0011] The present invention will be described in more detail below. A precursor sheet for a fuel cell separator (hereinafter abbreviated as "precursor sheet") according to the present invention is characterized by containing graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin.

[0012] [1] Graphite Particles The graphite particles constituting the precursor sheet of the present invention are not particularly limited, and either natural graphite or artificial graphite may be used. The artificial graphite particles may be appropriately selected from those conventionally used in fuel cell separators. Specific examples thereof include artificial graphite obtained by calcining needle coke and artificial graphite obtained by calcining lump coke. Meanwhile, the natural graphite particles may also be appropriately selected from those conventionally used in fuel cell separators. Specific examples thereof include lump natural graphite and flake natural graphite. These graphite particles may be used alone or in combination of two or more.

[0013] The shape of the graphite particles is not particularly limited, but is preferably spherical or flaky from the viewpoint of electrical conductivity. The average particle size of the graphite particles is not particularly limited, but in consideration of increasing electrical conductivity, it is preferably 5 to 200 μm, more preferably 10 to 200 μm, even more preferably 10 to 100 μm, and even more preferably 10 to 50 μm. In the present invention, the average particle size is the median diameter (d 50 ) (same below).

[0014] [2] Particulate or fibrous water-insoluble resin The particulate or fibrous water-insoluble resin is not particularly limited as long as it is particulate or fibrous and does not dissolve in water, and may be a thermoplastic resin or a thermosetting resin. As the thermoplastic resin, a resin with a melting point or glass transition point of 100° C. or higher is preferred because it has heat resistance that allows it to maintain its particulate or fibrous shape during drying when producing a precursor sheet. Specific examples include polyethylene, polypropylene, polyphenylene sulfide, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene, polyamide, polyetherketoneetherketoneketone, polyetherketone, liquid crystal polymer, polyimide, polyamideimide, polyphenylsulfone, polyetherimide and polysulfone, polybutylene terephthalate, polyethylene naphthalate, ABS resin, polycycloolefin and polyethersulfone, and derivatives thereof having a melting point of 100°C or higher, polycarbonate, polystyrene and polyphenylene oxide, and derivatives thereof having a glass transition point of 100°C or higher, and these may be used alone or in combination of two or more. The upper limit of the melting point or glass transition point is not particularly limited, but from the viewpoint of productivity of precursor sheets and fuel cell separators, a value of 300°C or lower is preferred.

[0015] The thermosetting resin can be appropriately selected from those commonly used as binder resins for carbon separators, etc. Specific examples include phenolic resins, epoxy resins, furan resins, unsaturated polyester resins, urea resins, melamine resins, diallyl phthalate resins, bismaleimide resins, polycarbodiimide resins, silicone resins, vinyl ester resins, and benzoxazine resins. These resins may be used alone or in combination. Among these, epoxy resins and phenolic resins are preferred because of their excellent heat resistance and mechanical strength. These water-insoluble resins are commercially available.

[0016] The particle shape of the water-insoluble resin is not particularly limited and may be any shape such as spherical, scale-like, block-like, foil-like, plate-like, needle-like, or amorphous, but spherical is preferred from the viewpoint of particle packing. The average particle size of the water-insoluble resin is also not particularly limited, but is preferably 1 to 150 μm from the viewpoints of improving particle packing and reducing the resistance of the resulting fuel cell separator.

[0017] In the precursor sheet of the present invention, the content of the particulate or fibrous water-insoluble resin is not particularly limited as long as the precursor sheet can be reslurried. From the viewpoint of ease of reslurrying, however, the content is preferably 10.0 to 70.0 parts by mass, and more preferably 15.0 to 65.0 parts by mass, per 100 parts by mass of the graphite particles.

[0018] [3] Water-Soluble Resin The water-soluble resin preferably has dispersibility, thickening properties, and adhesive properties from the viewpoint of uniformly dispersing graphite particles and a particulate or fibrous water-insoluble resin to form a sheet. In the present invention, "water-soluble" means that the resin is completely soluble in water at 25°C at a concentration of at least 1% by mass. Specific examples of water-soluble resins include aqueous resins such as acrylic resins, polyvinyl resins, polyether resins, polyurethane resins, polyester resins, polyolefin resins, polyamide resins, polyimide resins, polyallylamine resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, formaldehyde resins, silicone resins, fluororesins, and polysaccharides such as carboxymethyl cellulose. These resins may be used alone or in combination of two or more. Among these, acrylic resins, polyvinyl resins, polyether resins, and polysaccharides such as carboxymethyl cellulose are preferred from the viewpoint of uniformly dispersing graphite particles and a particulate or fibrous water-insoluble resin to form a sheet with a particularly small amount of addition. These water-soluble resins are commercially available.

[0019] In the precursor sheet of the present invention, the content of the water-soluble resin is not particularly limited as long as the precursor sheet can be reslurried. However, from the viewpoints of slurry dispersibility and ease of reslurrying the precursor sheet, the content is preferably 0.1 to 30.0 parts by mass, and more preferably 0.5 to 25.0 parts by mass, relative to 100 parts by mass of the graphite particles, and from the viewpoint of further increasing the strength of the precursor sheet, 1.0 to 25.0 parts by mass is even more preferable.

[0020] [4] Other Components In addition to the components described above, the precursor sheet of the present invention may contain other components commonly used in fuel cell separators. Examples of other components include internal release agents such as stearic acid wax, amide wax, montanic acid wax, carnauba wax, and polyethylene wax; conductive additives such as carbon black; and reinforcing materials such as carbon fiber. In particular, carbon fiber is preferably included from the viewpoint of further improving the strength of the precursor sheet and separator. The content of the other components is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of graphite particles, from the viewpoint of improving the reslurryability of the precursor sheet.

[0021] [5] Precursor Sheet Manufacturing Method The precursor sheet of the present invention can be obtained, for example, by forming a precursor sheet-making slurry, which is prepared by dispersing a composition containing graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin in water, into a sheet by coating or casting, and then drying and removing the water. In this way, by uniformly dispersing graphite and a particulate or fibrous water-insoluble resin by wet kneading and forming the sheet, it is possible to suppress the generation of voids due to unfilled resin during heat compression molding, and to obtain a separator with higher gas impermeability.

[0022] Examples of methods for producing a precursor sheet by coating include coating a slurry onto a resin film such as a PET film, drying the slurry, and then peeling the slurry from the resin film. The coating method is not particularly limited and may be appropriately selected from known methods such as spin coating, dipping, flow coating, inkjet coating, jet dispenser coating, spray coating, bar coating, gravure coating, roll coating, transfer printing, brush coating, blade coating, air knife coating, die coating, and screen printing.

[0023] One example of a method for producing a precursor sheet by casting is to pour the slurry into a box-shaped mold, dry it, and then remove it from the mold. If a mold with a shape that reflects the irregularities of the separator is used, it is possible to produce a precursor sheet with varying thicknesses in parts, which is difficult to achieve by a coating method. The material of the mold is not particularly limited, and may be appropriately selected from known materials such as release-treated metal molds and plastic molds made of silicone, fluororesin, etc.

[0024] The drying temperature for the slurry is not particularly limited as long as it is equal to or lower than the melting point or glass transition point of the particulate or fibrous water-insoluble resin, but is preferably equal to or lower than 100° C., more preferably from room temperature to 100° C., and even more preferably from 50 to 100° C. The thickness of the precursor sheet is not particularly limited as long as it allows the production of a fuel cell separator, but is preferably from 100 μm to 1 mm, and more preferably from 200 to 800 μm.

[0025] The precursor sheet of the present invention is a sheet of graphite particles and a particulate or fibrous water-insoluble resin formed by the water-soluble resin, and although its form is not particularly limited, it is preferable that at least a portion of the sheet has a structure in which the graphite particles and the particulate or fibrous water-insoluble resin are fixed by the water-soluble resin.

[0026] The precursor sheet of the present invention is characterized in that its shape is maintained by the dried water-soluble resin, and it has strength that allows it to be handled in sheet form, while the water-soluble resin redissolves when it comes into contact with water, allowing it to be easily converted into a slurry. Furthermore, since the sheet can be formed simply by drying and removing the water from the slurry, it is easy to form precursor sheets with an uneven shape with different thicknesses, rather than simply a flat plate shape as in the past.

[0027] [5] Fuel Cell Separator A fuel cell separator can be manufactured by heating and molding the precursor sheet of the present invention. The molding method is not particularly limited, but compression molding is preferred. The temperature during compression molding is not particularly limited as long as it exceeds the melting point or glass transition point of the particulate or fibrous water-insoluble resin, but a mold temperature of 150 to 250°C is preferred. The molding pressure is preferably 1 to 100 MPa, more preferably 1 to 60 MPa. The compression molding time is not particularly limited, but can be appropriately set from about 3 seconds to 1 hour.

[0028] By subjecting the precursor sheet of the present invention to heat compression molding, a particulate or fibrous water-insoluble resin is melted to fill the voids, bonding the graphite particles and obtaining a separator of the desired shape. Because the precursor sheet of the present invention uses a particulate or fibrous water-insoluble resin, the graphite particles are not pre-coated with a water-insoluble resin as in conventional methods. This prevents the formation of a resin layer on the separator surface during compression molding, resulting in low contact resistance and penetration resistance and excellent electrical conductivity. Furthermore, the resin content can be increased, resulting in a separator with high gas impermeability. In particular, the suppression of resin layer formation on the separator surface eliminates the need for a resin layer removal process to improve electrical conductivity. The increased surface exposure of the graphite particles results in the formation of fine irregularities, improving the adhesiveness of gaskets and the like, and further improving releasability during heat compression molding.

[0029] Generally, a solid polymer fuel cell is made up of a large number of unit cells arranged side by side, each of which is composed of a pair of electrodes sandwiching a solid polymer membrane and a pair of separators sandwiching these electrodes to form a gas supply / exhaust flow path. The fuel cell separator of the present invention can be used as some or all of these multiple separators.

[0030] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0031] [1] Precursor Sheet Preparation [Example 1-1] 100 parts by weight of flake graphite (particle size 20 μm, same below), 7.1 parts by weight of a water-soluble resin, polyacrylic acid (molecular weight 150,000, solids concentration 25% by weight aqueous solution, same below), 35.7 parts by weight of a particulate water-insoluble resin, particulate phenolic resin (particle size 25 μm, molecular weight 10,000, same below), and water as a solvent were mixed to prepare a precursor sheet slurry with a final solids concentration of 50% by weight. This slurry was applied to a release-treated PET film using a bar coater, dried in a blower dryer at 80°C, and peeled from the PET film after drying to obtain a precursor sheet. The resulting precursor sheet had a thickness of 480 μm.

[0032] Example 1-2 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the particulate water-insoluble resin was changed from particulate phenolic resin to powdered polypropylene (particle size 15 μm).

[0033] Example 1-3 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 1.4 parts by mass and the amount of particulate phenolic resin used was changed to 33.8 parts by mass.

[0034] Example 1-4 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 15.4 parts by mass and the amount of particulate phenolic resin used was changed to 38.5 parts by mass.

[0035] Example 1-5 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 6.4 parts by mass and the amount of particulate phenolic resin used was changed to 21.8 parts by mass.

[0036] Example 1-6 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 8.3 parts by mass and the amount of particulate phenolic resin used was changed to 58.3 parts by mass.

[0037] [Example 1-7] A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 7.2 parts by mass, the amount of particulate phenolic resin used was changed to 36.1 parts by mass, and 1 part by mass of carbon fiber (φ7 μm, fiber length 6 mm) was further blended.

[0038] Example 1-8 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 1.0 part by mass and the amount of particulate phenolic resin used was changed to 33.7 parts by mass.

[0039] Example 1-9 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 19 parts by mass and the amount of particulate phenolic resin used was changed to 39.7 parts by mass.

[0040] Example 1-10 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 6.3 parts by mass and the amount of particulate phenolic resin used was changed to 18.8 parts by mass.

[0041] Example 1-11 A precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that the amount of polyacrylic acid used was changed to 8.6 parts by mass and the amount of particulate phenolic resin used was changed to 63.8 parts by mass.

[0042] [Example 1-12] The precursor sheet obtained in Example 1-1 was mixed with water to prepare a slurry for producing a precursor sheet having a final solid content of 50 mass %, and a precursor sheet having a thickness of 480 μm was obtained in the same manner as in Example 1-1, except that this slurry was used.

[0043] Comparative Example 1-1 A slurry was prepared in the same manner as in Example 1-1, except that the amount of particulate phenolic resin used was changed to 33.3 parts by mass and polyacrylic acid was not added, but a precursor sheet could not be obtained.

[0044] [Comparative Example 1-2] 100 parts by weight of flake graphite, 7.1 parts by weight of polyacrylic acid, and water were mixed to prepare a slurry with a final solids concentration of 50% by weight. This slurry was applied to a release-treated PET film using a bar coater, dried in a fan dryer at 80°C, and then peeled off from the PET film to obtain a sheet. Particulate phenolic resin was dissolved in acetone to form a 50% by weight solution, which was then applied to and impregnated into the previously prepared sheet to obtain a precursor sheet containing 35.7 parts by weight of non-particulate phenolic resin derived from the particulate phenolic resin. The thickness of the obtained precursor sheet was 480 μm.

[0045] Table 1 shows a summary of the above examples and comparative examples.

[0046]

[0047] For Examples 1-1 to 1-12 and Comparative Examples 1-1 and 1-2, the dispersibility of the prepared slurries, the strength of the obtained precursor sheets, and the reslurrying of the precursor sheets were evaluated using the following methods. The results are shown in Table 2. [Slurry Dispersibility] The presence or absence of streaks or defects during application of the PET film was visually confirmed, and the thickness was measured at six random points and evaluated according to the following criteria. ⊚: No streaks or defects, and the thickness variation of the obtained precursor sheet was less than 3%. ◯: No streaks or defects, and the thickness variation of the obtained precursor sheet was 3% or more but less than 5%. Δ: Irregularities due to streaks or defects were observed, and the thickness variation of the obtained precursor sheet was 5% or more. ×: There were obvious streaks or defects, and a precursor sheet could not be obtained. [Precursor Sheet Strength] The tensile strength of the precursor sheet was measured using an autograph (manufactured by Shimadzu Corporation) at a chuck distance of 340 mm, a sample width of 40 mm, and a tensile speed of 100 mm / min. : 20N / 40mm or more 〇: 15N / 40mm or more and less than 20N / 40mm △: 10N / 40mm or more and less than 15N / 40mm [Reslurry] 30g of the precursor sheet pieces were added to 30mL of water and stirred to reslurry, and the presence or absence of streaks and defects at the time of applying the PET film was visually confirmed and evaluated according to the same criteria as for the dispersibility of the slurry. : No streaks or defects, and the thickness variation of the obtained precursor sheet was less than 3% 〇: No streaks or defects, and the thickness variation of the obtained precursor sheet was 3% or more and less than 5% △: Irregularities due to streaks and defects were observed, and the thickness variation of the obtained precursor sheet was 5% or more ×: There were obvious streaks and defects, and the precursor sheet could not be obtained

[0048]

[0049] As shown in Table 2, the slurries of Examples 1-1 to 1-12 have good dispersibility, and the obtained precursor sheets can be reslurried. Furthermore, as shown in Example 1-12, the dispersibility is good even when reslurried, and the obtained precursor sheets can also be reslurried. On the other hand, the slurry obtained in Comparative Example 1-1, which does not contain polyacrylic acid as a water-soluble resin, has poor dispersibility, and a precursor sheet cannot be obtained. The precursor sheet obtained in Comparative Example 1-2, which does not contain a particulate phenolic resin (contains a phenolic resin after dissolving in acetone), cannot be reslurried.

[0050] [3] Production of fuel cell separator [Example 2-1] The precursor sheet obtained in Example 1-1 was compression molded using a flat mold at 180°C and 60 MPa for 5 minutes to obtain a fuel cell separator. The thickness of the flat molded separator was 250 μm. [Example 2-2] A fuel cell separator was obtained in the same manner as in Example 2-1, except that the precursor sheet was changed to the one produced in Example 1-12.

[0051] The resulting fuel cell separators were measured for gas impermeability and conductivity by the following methods and evaluated according to the following criteria. The results are shown in Table 3. [Gas impermeability] A flat separator was molded, and the hydrogen gas permeability coefficient (unit: cm) was measured in accordance with JIS K7126-1:2006 (Plastics and sheets - Gas permeability test method - Part 1: Differential pressure method). 3 cm / (cm 2 The permeability coefficient of hydrogen gas was measured at 23°C and 150.3 kPa using a test gas (hydrogen gas) at a pressure of 150.3 kPa. Excellent: Hydrogen gas permeability coefficient was 1.0 x 10 -10 cm 3 cm / (cm 2 ・sec ・cmHg) or less. Good: Hydrogen gas permeability coefficient is 1.0 × 10 -10 m 3 cm / (cm 2 ・sec・cmHg) or more 1.0×10 -9 cm 3 cm / (cm 2sec cmHg) or less △: Hydrogen gas permeability coefficient is 1.0 × 10 -9 cm 3 cm / (cm 2 ・sec・cmHg) or more 1.0×10 -8 cm 3 cm / (cm 2 ×: Hydrogen gas permeability coefficient is less than 1.0 × 10 -8 cm 3 cm / (cm 2 [Conductivity] A flat separator is molded, sandwiched between gold-plated copper electrodes with a side length of 2 cm, and pressurized at 2.5 MPa for 10 seconds, then reduced to 1.0 MPa, and a current of 1 A / cm2 is applied between the gold-plated copper electrodes. 2 The interelectrode voltage was measured when a constant current of 1000 kJ / cm was applied. The obtained interelectrode voltage was converted into resistance, which was used as the separator penetration resistance (unit: mΩ cm). 2 ) and the conductivity was evaluated according to the following criteria: ⊚: Penetration resistance was 8 mΩ cm 2 Less than ○: Penetration resistance is 8 mΩ cm 2 10 mΩ・cm or more 2 Less than △: Penetration resistance is 10 mΩ cm 2 15 mΩ・cm or more 2 Less than ×: Penetration resistance is 15 mΩ cm 2 In the above cases

[0052]

[0053] As shown in Table 3, the fuel cell separators produced in Examples 2-1 and 2-2 are excellent in gas impermeability and electrical conductivity.

Claims

1. A precursor sheet for a fuel cell separator, comprising graphite particles, a particulate or fibrous water-insoluble resin, and a water-soluble resin.

2. A precursor sheet for a fuel cell separator according to claim 1, wherein said graphite particles and said particulate or fibrous water-insoluble resin are fixed by said water-soluble resin.

3. A precursor sheet for a fuel cell separator as described in claim 1, wherein the content of the water-soluble resin is 0.1 to 30.0 parts by mass per 100 parts by mass of the graphite particles, and the content of the particulate or fibrous water-insoluble resin is 10.0 to 70.0 parts by mass per 100 parts by mass of the graphite particles.

4. The fuel cell separator precursor sheet according to claim 1, which contains carbon fibers.

5. A fuel cell separator formed by molding the precursor sheet for a fuel cell separator according to any one of claims 1 to 4.

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