JPWO2006088034A1 - Fuel cell separator and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell separator having improved durability due to improved power generation efficiency accompanying stable supply of fuel gas and excellent acid resistance. The present invention relates to a fuel cell separator comprising a mixture of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees on a membrane surface, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more. A mixture of a polyimide resin and a carbon powder containing in the molecule at least one of the group consisting of a sulfonic acid group, a carboxyl group, a sulfonic acid metal base, a carboxyl metal base, an amino group, a hydroxyl group, a polybutadiene and a polyether group; It is related with the separator for fuel cells which consists of. [Selection figure] None

Description

  The present invention relates to a fuel cell separator and a method for producing the same. In particular, the surface is highly hydrophilic, the fuel gas is supplied smoothly, and the flow of water and drainage supplied with the gas is smooth, so the polymer electrolyte fuel has high power generation efficiency and excellent durability. A battery separator can be provided.

  Conventionally, a separator made of carbon, in which a groove for allowing hydrogen gas or air to pass therethrough has been mainly used as a separator for a polymer electrolyte fuel cell after a thermosetting resin and a carbon material are mixed and baked. This carbon separator is known to have problems such as curling generated during firing, gas leakage, reduction in power generation efficiency due to elution of unfired components, and high cost. Moreover, although the resin molding (patent document 1) which mix | blended the carbon material with the polyimide resin and the electrically conductive resin molding (patent document 2) which mix | blended the carbon material with the polyimide resin and the epoxy resin are examined, as a polyimide resin, Since thermosetting polyimide resin was used, it had the same problem as above. On the other hand, by improving the defects of these resin moldings, it was attempted to use a metal plate as a separator that was excellent in strength even when it was thin, and could be manufactured at a low cost such as press processing, and stainless steel was plated with gold (Patent Documents 3 and 4), a method of forming carbon fine particles together with Ta and Ti on the surface of stainless steel by vapor deposition (Patent Document 5) and the like have been proposed.

  However, these methods are concerned about the corrosion of stainless steel, which is thought to be caused by the occurrence of pinholes, and the affinity of the separator surface with water generated after the reaction of water vapor, hydrogen gas and oxygen supplied with the fuel gas. Due to its poor nature, there is a drawback that stable supply of fuel gas and stable drainage are difficult.

JP 2000-234055 A JP 2000-239488 A JP-A-10-228914 JP 2000-294257 A JP-A-11-126622

  An object of the present invention is to improve these drawbacks and to provide an inexpensive fuel cell separator that has less curling, excellent acid corrosion resistance, and can smoothly perform fuel gas and drainage.

As a result of intensive studies to achieve the above object, the present inventor has reached the present invention. That is, the present invention relates to the following.

(1) A fuel cell separator comprising a mixture of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees on the membrane surface, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more.

(2) For fuel cells in which a mixture layer of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more is laminated on a metal plate separator.

(3) Polyimide resin and carbon containing in the molecule at least one of the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group A fuel cell separator comprising a mixture of powders.

(4) Polyimide resin and carbon containing in the molecule at least one of the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group A fuel cell separator in which a powder mixture layer is laminated on a metal plate.

(5) The separator for a fuel cell according to (2) or (4), wherein the metal plate is a steel plate, a stainless steel plate, a titanium plate or an aluminum plate.

(6) After laminating a mixture layer of a thermoplastic resin and carbon powder having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more on a metal plate, press A method for producing a separator for a fuel cell, in which concave and convex grooves are formed by processing.

(7) After forming a concave and convex groove by press molding a metal plate, a thermoplastic resin having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more A method for producing a separator for a fuel cell in which a mixture layer of carbon powder is laminated.

(8) A polyimide containing in the molecule at least one of the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group on a metal plate A method for producing a separator for a fuel cell, in which an uneven groove is formed by pressing after laminating a mixture layer of a carbon resin and carbon powder.

(9) After forming a concave and convex groove by press molding a metal plate, among the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group The manufacturing method of the separator for fuel cells which laminates | stacks the mixture layer of the polyimide resin and carbon powder which contain at least 1 type in a molecule | numerator.

(10) The method for producing a fuel cell separator according to any one of (6) to (9), wherein the metal plate is a steel plate, a stainless steel plate, a titanium plate, or an aluminum plate.

  The present invention is a thermoplastic resin that forms a tough film with high surface hydrophilicity and high elongation, preferably by using a molded body having an appropriate conductivity by mixing a polyimide resin and carbon powder, It is possible to provide a fuel cell separator that is excellent in acid resistance, has a stable supply of fuel such as hydrogen and air, and can smoothly discharge and recycle water generated by power generation.

The present invention will be described in detail below.
Generally, a thermoplastic resin is hydrophobic, and a water droplet contact angle shows 90 degree | times or more. On the other hand, in a fuel cell, hydrogen or air (oxygen) combustion gas is usually supplied to an electrode provided with an ion exchange membrane through a groove of a separator together with water vapor. Water generated at the electrode by power generation is discharged through the separator and reused as water vapor for cooling the stack and supplying combustion gas. Since it is important for the power generation efficiency and durability of the fuel cell that the water flows stably between the grooves of the separator, the separator surface is preferably hydrophilic.
Therefore, the thermoplastic resin used in the present invention is preferably hydrophilic, and its index is preferably a water droplet contact angle of 15 to 80 degrees and a water absorption of 3 to 15%. As the thermoplastic resin used in the present invention, a polyimide resin containing a polar group is preferable in consideration of acid resistance and the like. Examples of the polyimide resin include polyimide resin, polyamideimide resin, polyetherimide resin, and polyesterimide resin. Among these, polyamideimide resin is particularly preferable from the viewpoint of solvent solubility and separator processability.
Polyimide resins can be easily synthesized by a conventionally known method such as a method in which a polycarboxylic acid anhydride and diamine or diisocyanate are stirred in a polar organic solvent such as N-methyl-2-pyrrolidone at room temperature or under heating. Can do. In this case, a polyamideimide resin can be produced by replacing part or all of the acid component with trimellitic anhydride or dicarboxylic acid.

It is preferable that the acid component used for the synthesis of the polyimide resin used in the present invention is mainly trimellitic anhydride, but part or all of it can be replaced with other polybasic acid or anhydride thereof. For example, tetracarboxylic acids such as pyromellitic acid, biphenyl tetracarboxylic acid, biphenyl sulfone tetracarboxylic acid, benzophenone tetracarboxylic acid, biphenyl ether tetracarboxylic acid, ethylene glycol anhydrobis trimellitate, propylene glycol anhydro bis trimellitate and the like This is accomplished by copolymerizing the anhydrides. Among these, pyromellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, biphenyl tetracarboxylic acid anhydride, ethylene glycol anhydrobis trimellitate, propylene glycol anhydro bis trimellitate in terms of reactivity, solubility, price, etc. Is preferably used. In addition, oxalic acid, adipic acid, malonic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, dicarboxypolybutadiene, dicarboxypoly (acrylonitrile-butadiene), dicarboxypoly (styrene-butadiene), etc., as long as the properties are not impaired. Aliphatic dicarboxylic acids such as aliphatic dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 4,4′-dicyclohexylmethanedicarboxylic acid, dimer acid, terephthalic acid, isophthalic acid, diphenylsulfone dicarboxylic acid Aromatic dicarboxylic acids such as acid, diphenyl ether dicarboxylic acid, naphthalene dicarboxylic acid and the like may be copolymerized. Among these, 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid are preferably copolymerized from the viewpoint of acid resistance, and dimer acid and number average molecular weight are 1000 or more and less than 8000 from the adhesion property to metal. It is preferable to copolymerize dicarboxypolybutadiene, dicarboxypoly (acrylonitrile butadiene) and dicarboxypoly (styrene-butadiene). These copolymerization amounts are preferably in the range of 1 to 60 mol% when the acid component is 100 mol%.

In addition, a urethane group can be introduced into the molecule by replacing part of the acid component of the polyimide resin with glycol. Examples of glycols include alkylene glycols such as ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, and hexanediol, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and one or more of the above dicarboxylic acids. And polyesters having a hydroxyl group at the molecular end synthesized from one or more of the above-mentioned glycols. Among these, polyethylene glycol and polyester having a terminal hydroxyl group are used together for the effect of imparting adhesion to metal and hydrophilicity. Polymerization is preferred. Moreover, these number average molecular weights are preferably 500 or more, and more preferably 1000 or more. The upper limit is not particularly limited, but is preferably less than 8000.

Examples of the diamine (diisocyanate) component used in the synthesis of the polyimide resin in the present invention include aliphatic diamines such as ethylenediamine, propylenediamine, and hexamethylenediamine, and their diisocyanates, 1,4-cyclohexanediamine, and 1,3-cyclohexanediamine. Alicyclic diamines such as dicyclohexylmethane-4,4′-diamine and their diisocyanates, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 4,4 Examples include aromatic diamines such as' -diaminodiphenylsulfone, benzidine, 3,3'-dimethylbenzidine, xylylenediamine, naphthalenediamine, and diisocyanates thereof. Refractory, cost, diaminodiphenylmethane terms of electrolyte solution resistance, 3,3'-dimethyl benzidine, isophorone diamine, dicyclohexylmethane-4,4'-diamine and these diisocyanates are preferred. A preferable copolymerization amount is in the range of 30 to 100 mol% when the amine (isocyanate) component of the polyimide resin is 100 mol%.

  In order to make the thermoplastic resin hydrophilic in the present invention, other thermoplastic resin having a polar group may be blended, but it is preferable to introduce the polar group directly into the molecule. As the polar group, introduction of at least one of the group consisting of a sulfonic acid group, a carboxyl group, a sulfonic acid metal base, a carboxyl metal base, an amino group, a hydroxyl group and a polyether group is preferable. Alternatively, after the synthesis is completed, the following compound is preferably added for copolymerization or modification.

  For example, introduction of sulfonic acid metal base includes 5-sodium sulfoisophthalic acid, ethylene glycol ester, propylene glycol ester of 5-sodium sulfoisophthalic acid and the like. Examples of the introduction of the carboxyl group include a method of graft polymerization of the above trifunctional or higher polyvalent carboxylic acids and acrylic acid onto a polyimide resin. Examples of amino group introduction include diethanolamine, N-methyl-diethanolamine, and N-ethyl-diethanolamine. Examples of the introduction of the hydroxyl group include glycerin, trimethylolpropane, pentaerythritol, 5-sodium hydroxyisophthalic acid, ethylene glycol ester of 5-sodium hydroxyisophthalic acid, and the like. Examples of the introduction of the polyether group include copolymerization of polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and the like. These copolymerization amounts are preferably in the range of 0.01 to 30 mol% when the total amount of each of the acid component and the isocyanate component is 100 mol%.

  The polyimide resin obtained by the introduction of the above polar group is hydrophilized and the contact angle on the surface of the coating film is lowered to achieve the object of the present invention. More preferably, it is a polyimide resin polymerized by combining a raw material having a hydrophobic raw material. For example, one or more of polyether groups such as sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polyethylene glycol and carboxyl group-containing polybutadiene, polyacrylonitrile butadiene, dimer acid, etc. Are preferably copolymerized simultaneously. In this case, all the raw materials may be charged at once to form a random copolymer, or the raw materials may be sequentially added to the reaction system to form a block copolymer. Since the hydrophilicity of the surface is improved, it tends to be more preferable.

The polyimide resin used in the present invention can be easily produced in a polar solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone. When using the isocyanate method, it is preferable to stir while heating at 60 to 200 ° C. If necessary, amines such as triethylamine and diethylenetriamine, and alkali metal salts such as sodium fluoride, potassium fluoride, cesium fluoride, sodium methoxide, and the like can be used as a catalyst.

The thermoplastic resin used in the present invention preferably has a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more of the coating film of only the resin. If the water droplet contact angle is less than 15 degrees, the molded product will swell greatly and shape stability will be poor, and the flow path of gas or water vapor may become narrow during use. If it exceeds 80 degrees, stable supply of the desired combustion gas May be a problem. The lower limit of the water droplet contact angle is preferably 30 ° C. or higher. When the water absorption is less than 3%, the hydrophilicity of the molded product is insufficient, and there is a problem in the stable supply of combustion gas and water vapor. When the water absorption exceeds 15%, the molded product swells greatly and the same problem as described above may occur. . If the tensile elongation is less than 50%, the molded product is fragile, cracking may occur during molding, or moldability may be insufficient when molding after applying to metal. The upper limit of the tensile elongation is not particularly limited, but is preferably less than 500%. The water droplet contact angle in the present invention is a value measured with a contact angle meter (CA-X type) manufactured by Kyowa Interface Science Co., Ltd., using a resin-only film having a thickness of 30 μm. The water absorption rate in the present invention is determined by measuring the weight (W0) after drying about 3 g of a solid resin without foaming at 120 ° C. for 1 hour, and immersing it in water at 25 ° C. for 20 hours. The weight (W1) after wiping off is measured to obtain a value obtained by the following formula. Water absorption (%) = 100 × {(W1−W0) / W1}. The tensile elongation in the present invention is a value measured using a resin-only film having a thickness of 30 μm under a condition of 25 ° C. and 70% RH at a tensile speed of 20 mm / min.

The separator for a fuel cell of the present invention is provided in two forms in which a mixed resin molded body of a thermoplastic resin and carbon powder and a mixture of the thermoplastic resin and carbon powder are laminated on a metal plate. As a metal plate, a stainless steel plate, a steel plate, a titanium plate, and an aluminum plate are preferable. Hereinafter, these manufacturing methods will be described. Although there is no restriction | limiting in particular in a manufacturing method, The following methods are preferable and (1)-(3) are especially preferable.
(1) Thermoplastic resin powder or pellets and carbon powder are blended and thermoformed by injection molding or press molding.
(2) A solution in which carbon powder is mixed and dispersed in a thermoplastic resin solution is applied to a metal plate and dried, and then uneven grooves are formed by press molding.
(3) After the metal plate is press-molded to form uneven grooves, a solution in which carbon powder is mixed and dispersed in a thermoplastic resin solution is applied and dried.
(4) After laminating the molded body of (1) on a metal plate, concave and convex grooves are formed by press molding.
(5) After the metal plate is press-molded to form uneven grooves, the molded body of (1) is laminated on the metal plate.

The thermoplastic resin used for the production is preferably a polyimide resin containing a polar group. The manufacturing method of the separator using this polyimide resin is demonstrated concretely.
The polyimide resin is produced by a solution polymerization method in a polar solvent as described above. The polymerization solution can be used as it is in (2) and (3) of the above-described separator production method.

The polyimide resin used in the production of (1) is solidified by putting a solution of polyimide resin into a poor solvent such as water, and washed, dried and pulverized into a powder, or in a pellet form What is used is a pellet obtained by melting and kneading this polyimide solid resin and carbon powder, or a master pellet, if necessary, mixed with a higher fatty acid salt or other inorganic filler, and injection molded and / or It is obtained by press molding. As the carbon powder, carbon black such as ketjen black, furnace black, acetylene black and the like alone or a mixture of two or more kinds thereof are used, and the volume resistance of the molded body is 1 to 10 ⁻⁵ Ω · cm, preferably It is preferable to mix | blend so that it may become 10 ^{< -1} > ^-10 < ^-3 > (omega | ohm) * cm. The temperature at the time of injection molding or press molding is preferably 30 to 100 ° C. higher than the glass transition temperature of the polyimide resin used. The sheet thickness of the molded product is preferably 0.1 to 3 mm.

In the production method (2), the above-described carbon black and carbon powder such as graphite are mixed with the polyimide resin solution so that the volume resistance value is 1 to 10 ⁻³ Ω · cm, and a ball mill, sand mill, high speed A solution dispersed by a dissolver or the like is applied to a metal plate, dried, and then press-molded to form a predetermined groove.

In the manufacturing method of (3), it is manufactured by applying a polyimide resin / carbon powder mixed resin solution similar to that used in (2) to a metal plate having grooves formed by press molding in advance, and drying. The

In the case of (2) and (3), the thickness of the metal is preferably 0.1 to 2 mm, and the thickness of the polyimide resin and carbon powder mixture layer is preferably 0.003 to 0.5 mm.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited by these Examples.
In addition, the measured value in an Example was measured with the following method.
(1) Contact angle A water droplet contact angle was measured with a contact angle meter (CA-X type) manufactured by Kyowa Interface Science Co., Ltd. using a film that was applied on a polyester film, dried at 150 ° C. for 20 hours and then peeled off. It was measured. In addition, the measurement of the water droplet contact angle after the sample was immersed in a sulfuric acid aqueous solution of pH 3 at 90 ° C. for 20 hours was also performed.
(2) The weight (W0) after drying the water-absorbing solid resin at 120 ° C. for 1 hour is measured, and the weight (W1) after being immersed in water at 25 ° C. for 20 hours is determined by the following formula. It was.
Water absorption rate (%) = 100 × {(W1-W0) / W1}
(3) Tensile high elongation Polyester film was coated with a resin solution, dried at 150 ° C. for 20 hours, and then peeled off, and a 30 μm resin single film was removed at 25 ° C. and 70% RH using a tensile tester manufactured by Toyo Baldwin. Measurement was performed at a pulling rate of 20 mm / min under the conditions of
(4) The appearance after the acid-resistant molded product was immersed in a sulfuric acid aqueous solution of pH 3 at 90 ° C. for 20 hours was observed.
Judgment: ○: No abnormality △: Peeling or cracking ×: Peeling or cracking occurred.
(5) In the case of a moldable metal laminate, the crack and peeling of the coating film during press working were observed. In the case of a thermoformed product, the smoothness of the surface was observed.

[Example 1]
In a four-necked flask equipped with a thermometer, a condenser tube, and a nitrogen gas inlet tube, 0.95 mol of trimellitic anhydride (TMA), 0.05 mol of 5-sodium sulfoisophthalic acid, 4,4′-diphenylmethane diisocyanate (MDI) 1 mol and potassium fluoride 0.02 mol were charged together with N-methyl-2-pyrrolidone so that the solid content concentration would be 25%, and stirred at 130 ° C. for 5 hours to be reacted. The obtained polyamideimide resin had a logarithmic viscosity of 0.68 dl / g and a glass transition temperature of 285 ° C.
100 parts of this polyamideimide resin solution was mixed with 25 parts of graphite and uniformly dispersed by a three roll mill.
This dispersion was applied to stainless steel (SUS304) having a thickness of 0.3 mm so as to have a dry film thickness of 0.3 mm and dried at 200 ° C. for 1 hour. The properties of this laminate are shown in Table 1.

[Examples 2 to 8]
The same method as Example 1 except that 5-sodiumsulfoisophthalic acid of Example 1 was changed to the monomers (and amounts thereof) shown in Table 1 and (molar amounts listed in Table 1) moles of TMA were used. Thus, a polyamide-imide resin was synthesized, and a stainless steel plate laminate using this was prepared. The characteristics are shown in Table 1.

[Example 9]
Under the same conditions as in Example 1, using a solution obtained by dissolving YK-30 (acrylic polymer of Nippon Exlan Kogyo Co., Ltd.) as a thermoplastic resin in N-methyl-2-pyrrolidone so that the solid content concentration becomes 15%. A metal laminate was prepared. The evaluation results are shown in Table 1.

[Example 10]
The polyamideimide resin solution of Example 1 was poured into water, solidified, sufficiently washed with water, dried and pulverized to obtain a solid polyamideimide resin.
After 100 parts of graphite were dry blended with 100 parts of this solid resin, the mixture was kneaded for 15 minutes in a heating mill at 320 ° C., and a predetermined amount of the mixture was filled in the mold, followed by hot pressing at 290 ° C. for 15 minutes. And a molded product having a thickness of 2 mm was obtained. The properties of this molded product are shown in Table 1.

[Example 11]
Using a four-necked flask equipped with a thermometer, a cooling tube, and a nitrogen introducing tube, two-stage polymerization was performed by the following method to synthesize a block copolymer.
(First stage polymerization)
0.37 mol of TMA, 0.25 mol of polyethylene glycol having a molecular weight of 2000, 0.62 mol of MDI and 0.012 mol of potassium fluoride were charged together with NMP so that the solid content concentration would be 25%, and at 130 ° C. for 2.5 hours Reacted.
(Second stage polymerization)
After the first stage polymerization was completed, the solution was cooled to 50 ° C. or lower, and then 0.25 mol of TMA, 0.05 mol of acrylonitrile butadiene having a terminal carboxyl group (CTBN 1300 × 13 manufactured by Ube Industries), 0.3 mol of MDI and potassium fluoride. 0.006 mol was charged together with NMP so that the solid concentration would be 25%, and reacted at 130 ° C. for 2.5 hours.
Graphite was mixed with the obtained polyamideimide resin solution in the same manner as in Example 1, and applied to a stainless steel plate and dried to prepare a metal laminate. The results are shown in Table 1.

[Comparative Example 1]
A polyamideimide resin was synthesized under the same conditions as in Example 1 except that 1.05 mol of trimellitic anhydride and 1 mol of diphenylmethane-4,4′-diisocyanate were used in Example 1. The obtained polyamideimide resin had a logarithmic viscosity of 0.41 dl / g and a glass transition temperature of 295 ° C.
Using this polyamideimide resin, a metal laminate was prepared under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[Comparative Example 2]
A polyamide-imide resin was synthesized under the same conditions as in Comparative Example 1 except that the amount of trimellitic anhydride in Comparative Example 1 was changed to 1 mol. Using this solution, a metal laminate was prepared under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[Comparative Example 3]
In the polyamideimide resin solution of Comparative Example 1, 20% of polyethylene glycol having a molecular weight of 400 was blended with respect to the resin solid content. Using this mixed solution, a metal laminate was prepared under the same conditions as in Example 1. The evaluation results are shown in Table 1.

[Comparative Example 4]
A metal laminate was prepared under the same conditions as in Example 1 using a solution in which 3 parts of a nonionic surfactant (trade name Neugen HC) was blended with 100 parts of the polyamideimide resin solution of Comparative Example 2. The evaluation results are shown in Table 1.

The present invention provides a fuel cell separator having a stable supply of fuel gas and excellent acid resistance by using a thermoplastic resin excellent in hydrophilicity, particularly a mixture of a polar group-containing polyimide resin and carbon powder. it can.

Claims (10)

A fuel cell separator comprising a mixture of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees on the membrane surface, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more. A separator for a fuel cell in which a mixture layer of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more is laminated on a metal plate. Mixture of polyimide resin and carbon powder containing in the molecule at least one of the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group A fuel cell separator comprising: Mixture of polyimide resin and carbon powder containing in the molecule at least one of the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group A separator for a fuel cell in which a layer is laminated on a metal plate. The separator for a fuel cell according to claim 2 or 4, wherein the metal plate is a steel plate, a stainless steel plate, a titanium plate, or an aluminum plate. After laminating a mixture layer of a thermoplastic resin and a carbon powder having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more on a metal plate, it is uneven by pressing. Of manufacturing a fuel cell separator for forming a groove. After forming a concave-convex groove by press molding a metal plate, a thermoplastic resin and carbon powder having a water droplet contact angle of 15 to 80 degrees, a water absorption rate of 3 to 15%, and a tensile elongation of 50% or more on the film surface A method for producing a fuel cell separator in which a mixture layer is laminated. A polyimide resin containing, in a molecule, at least one selected from the group consisting of a sulfonic acid group, a carboxyl group, a sulfonic acid metal base, a carboxyl metal base, an amino group, a hydroxyl group, a polybutadiene group, and a polyether group on a metal plate; A method for producing a separator for a fuel cell, in which an uneven groove is formed by pressing after laminating a mixture layer of carbon powder. After forming a concave and convex groove by press molding a metal plate, at least one kind selected from the group consisting of sulfonic acid group, carboxyl group, sulfonic acid metal base, carboxyl metal base, amino group, hydroxyl group, polybutadiene group and polyether group Is a method for producing a separator for a fuel cell in which a mixture layer of a polyimide resin containing carbon and a carbon powder is laminated. The method for producing a separator for a fuel cell according to any one of claims 6 to 9, wherein the metal plate is a steel plate, a stainless steel plate, a titanium plate, or an aluminum plate.