JP4430962B2 - Separator material for polymer electrolyte fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a separator material for a polymer electrolyte fuel cell comprising a graphite / resin cured molded body and a method for producing the same.

  A fuel cell directly converts chemical energy of fuel into electrical energy, and has high conversion efficiency to electrical energy. Especially, polymer electrolyte fuel cells have lower temperatures and higher output than phosphoric acid fuel cells. Therefore, it is expected as a small mobile power source and a stationary power source including an automobile power source.

  The polymer electrolyte fuel cell is usually an electrolyte membrane made of a polymer ion exchange membrane such as a fluororesin ion exchange membrane having a sulfonic acid group, and a catalyst electrode carrying a catalyst such as platinum on both sides thereof, A stack in which a single cell composed of a separator or the like provided with gas supply irregularities (grooves) for supplying a fuel gas such as hydrogen or an oxidant gas such as oxygen or air is stacked on each electrode, and 2 provided outside the stack. It consists of two current collectors.

  As shown in FIG. 1, the unit cell has a pair of electrodes 3, 4 (cathode 3, anode 4) disposed with an electrolyte membrane 5 made of an ion exchange membrane formed of, for example, a fluorine-based resin interposed therebetween, The separator 1 is formed of a dense carbon material sandwiched between both sides, and a sealing material 6 is provided at the end of the separator in a direction parallel to the gas groove. The electrodes 3 and 4 are formed of a porous body made of short carbon fibers carrying a catalyst such as platinum, or carbon black carrying a catalyst bound with a resin.

  A plurality of concave and convex grooves 2 are formed in the separator 1, and a space formed between the grooves 2 and the cathode 3 is used as an oxidant gas (oxygen-containing gas such as air) flow path. The space formed between the fuel gas (for example, hydrogen gas or a mixed gas containing hydrogen gas as a main component) flow path, using the chemical reaction that occurs when the fuel gas and the oxidant gas contact the electrode, An electric current is taken out between the electrodes. In general, the battery stack is assembled by laminating the single cells into tens to hundreds.

  Therefore, since the separator needs to supply the fuel gas and the oxidant gas to the electrode in a completely separated state, a high degree of gas impermeability is required. In addition, it is effective to reduce the internal resistance of the battery in order to increase the power generation efficiency, and it is necessary to reduce the plate thickness of the separator and to have high conductivity.

  In order to improve battery performance, the single cells in the stack are assembled so that they are in close contact with each other, and a good contact state is maintained even during power generation to prevent an increase in the contact electrical resistance between the separator and the electrode. At the same time, it is important to prevent gas leakage between single cells and gas leakage outside the single cells. That is, it is important that the material strength is high so that no breakage or chipping occurs during assembly, and that the material strength is sufficient even at a temperature of about 100 ° C., which is the operating temperature of the battery. Furthermore, it is required to have high moisture resistance so that no dimensional change due to moisture absorption occurs in the atmosphere.

  A carbonaceous material has been conventionally used as a separator material that requires such material characteristics, and a carbon / resin formed by binding a carbon powder such as graphite with a thermosetting resin as a binder. A cured molded body is preferably used.

For example, Patent Document 1 discloses a plate-like molded body composed of 60 to 85% by weight of graphite powder having a particle size distribution with an average particle size of 50 μm or less and a maximum particle size of 100 μm or less and a thermosetting resin of 15 to 45% by weight. Graphite-resin curable molding having a material property of a specific resistance in the plane direction of 300 × 10 ⁻⁴ Ωcm or less, a ratio of specific resistance in the thickness direction / plane direction of 7 or less, and a bending strength of 300 kgf / cm ² or more A separator member for a polymer electrolyte fuel cell and a method for producing the same are disclosed.

  In Patent Document 2, 100 parts by weight of graphite powder having an average particle size of 50 μm or less and a maximum particle size of 250 μm or less and 15 to 30 parts by weight of phenol resin having a number average molecular weight of 100 to 400 are mixed, and the mixture is pulverized and sieved. While adjusting the sized particle size of 0.1 to 5 mm prepared to 30 to 180 ° C., injection molding is performed on a mold heated to a temperature of 100 to 200 ° C., and the molded body is heat-cured. A method for producing a fuel cell separator is disclosed.

  Further, the present applicant mixed and kneaded a phenol resin solution having a saturated water absorption of 3% or less and a graphite powder in a weight ratio of 10 to 25% by weight of resin solids and 90 to 75% by weight of graphite powder. The present inventors have developed and proposed a method for producing a separator for a polymer electrolyte fuel cell, characterized in that the kneaded product is dried and then pulverized, and the pulverized particles are filled in a mold and hot-press molded.

  According to Patent Document 3, by using a phenol resin having a low water absorption rate, it is possible to manufacture a separator with little warpage and little increase in electrical resistance due to water absorption.

  Furthermore, the present applicant has advanced research focusing on the properties of a novolak type phenolic resin as a thermosetting resin. Graphite powder has a monomer amount of 5% by weight or less, a dimer amount of 20% by weight or less, and a plate flow at 125 ° C. A separator for a polymer electrolyte fuel cell made of a graphite / resin-cured molded body, in which a novolac type phenol resin of 150 mm or more is bound as a binder, and a manufacturing method thereof (Patent Document 4) have been developed.

According to Patent Document 4, by using a novolac type phenol resin having a low monomer and dimer content and a low melt viscosity and excellent moldability, it is dense and excellent in gas impermeability, and has low electrical resistance and mechanical strength. A separator material for a polymer electrolyte fuel cell having high moisture resistance and excellent material properties and a method for producing the same are provided.
JP 2000-021421 A JP 2000-331690 A Japanese Patent Application No. 2002-288521 Japanese Patent Application No. 2003-399296

  However, since novolak-type phenol resin usually uses hexamine (hexamethyltetramine) as a curing agent, ammonia gas is generated as a decomposition gas of hexamine during the curing reaction, and a part of the generated ammonia gas is contained in the cured resin. Since it remains, a trace amount of ammonia also remains in the graphite / resin cured molded body.

  Since the polymer electrolyte fuel cell is exposed to a moisture-rich environment such as water generated by gas humidification or cell reaction during operation or cooling water, the ammonia remaining in the separator becomes ammonium ions. The ammonium ions are eluted in the battery cell, and the ammonium ions hinder the movement of protons in the electrolyte membrane or lower the catalytic function of the electrode. As a result, there is a problem that the battery performance is lowered. In addition, when the amount of TOC (total organic carbon) elution increases, the catalyst surface that causes the battery reaction is covered to reduce the catalytic activity, or adhere to the electrolyte membrane and contaminate it, changing the water retention of the electrolyte membrane, It will inhibit the movement.

  Furthermore, when a novolac type phenol resin is used, for example, the water absorption elongation rate in 90 ° C. hot water simulating the environment during battery operation is large, and non-uniform elongation occurs in the separator, causing cracks, There is a problem to break. In addition, when ethylene glycol, which is an antifreeze solution, is added to the cooling water, the elongation rate due to the liquid absorption may be larger.

  In other words, the separator material of the polymer electrolyte fuel cell is excellent in gas impermeability, low electrical resistance, high mechanical strength, and the like, which are conventionally known, and lowers the battery performance. It is necessary that the elution of ammonia and organic substances is small and the elongation at the time of water absorption is small.

  Therefore, as a result of intensive studies to solve these problems, the present inventors have used a curing agent containing nitrogen by using a benzylic ether type phenol resin having a dimethylene ether bond in combination. It was confirmed that curing can be achieved only by heating, generation and residue of ammonia was suppressed, and elution of TOC (total organic carbon) was further reduced to solve these problems. That is, an object of the present invention is to provide a separator for a polymer electrolyte fuel cell having excellent performance that solves these problems and a method for producing the same.

In order to achieve the above object, a separator for a polymer electrolyte fuel cell according to the present invention is composed of a novolac type graphite powder having a benzylic ether type phenol resin and a monomer amount of 5% by weight or less and a dimer amount of 20% by weight or less. the weight ratio of the resin solids of the phenolic resin is 90: 10 to 40: characterized in construction in that it consists formed by sintering wearing graphite / cured resin molded product 60 mixed resin as a binder.

  The weight ratio of the resin solid content of the mixed resin to the graphite powder is preferably 10:90 to 35:65.

The method for producing a separator for a polymer electrolyte fuel cell according to the present invention is a method for producing a separator for a polymer electrolyte fuel cell according to the present invention, wherein the amount of benzylic ether type phenol resin and monomer is 5% by weight or less. The mixed resin solution in which the weight ratio of the resin solid content of the novolak-type phenolic resin having a dimer amount of 20% by weight or less is adjusted to 90:10 to 40:60, and the organic solvent after kneading the graphite powder with the mixed resin solution The preformed mold is filled with a molding powder obtained by volatilizing and then pulverizing the kneaded product, and the preform is inserted into the molding mold by pressing the upper mold and pressurizing to 1 to 10 MPa. It is structurally characterized by hot pressing at a temperature of 20-50 MPa and a temperature of 150-250 ° C.

  The weight ratio of the resin solid content of the mixed resin to the graphite powder is preferably 10:90 to 35:65.

  The novolac type phenol resin preferably has a monomer amount of 5% by weight or less, a dimer amount of 20% by weight or less, and a plate flow at 125 ° C. of 150 mm or more.

  Using a mixed resin of benzylic ether type phenolic resin and novolac type phenolic resin as the binder resin of graphite powder, and specifying the weight ratio of the resin solids, the resin solids content of the mixed resin and the graphite powder, Formed from a graphite / resin-cured molded article with low water absorption elongation when immersed in hot water at 90 ° C. for 500 hours, ammonium ion elution and TOC (total organic carbon) elution after 50 hours. According to the separator material for a polymer electrolyte fuel cell of the present invention, the battery performance is excellent, the output decrease after long-term power generation is small, and stable power generation is possible.

  Also, a kneaded product in which a mixed resin of benzylic ether type phenolic resin and novolac type phenolic resin is used as a binding resin of graphite powder, and the weight ratio of the resin solid content, the resin solid content of the mixed resin and the weight ratio of graphite powder is specified. The above separator material can be manufactured by preparing a preform in advance from a molding powder obtained by pulverizing and then inserting the preform into a mold and hot pressing.

  The solid polymer fuel cell separator material of the present invention is a graphite / resin cured molded body obtained by binding graphite powder with a mixed resin of benzylic ether type phenolic resin and novolac type phenolic resin as a binder. The graphite / resin cured molded body is formed into a plate shape having a thickness of about 1 to 3 mm, and a groove having a depth of about 0.5 to 1 mm serving as a flow path for fuel gas and oxidant gas on both the front and back surfaces or one surface Are formed in large numbers.

And this invention, when this graphite / resin hardening molded object is immersed in 90 degreeC hot water,
(1) The water absorption elongation after immersion for 500 hours is 0.20% or less,
(2) Ammonium ion elution amount after immersion for 50 hours is 2 μg / g or less,
(3) TOC (total organic carbon) elution amount after immersion for 50 hours is 100 μg / g or less,
It is characterized by having the following properties.

  Artificial graphite, natural graphite, expanded graphite, or a mixture thereof is used as the graphite powder, and graphite powder that has been pulverized by an appropriate pulverizer and sieved to adjust the particle size is used. The particle size of the graphite powder is adjusted, for example, to an average particle size of 50 μm or less and a maximum particle size of 100 μm or less in order to prevent the dropping of graphite powder particles and the generation of cracks between particles when providing gas grooves in the separator. It is preferable.

  The separator for a polymer electrolyte fuel cell according to the present invention is obtained by binding the graphite powder by a mixed resin of a benzylic ether type phenolic resin and a novolac type phenolic resin. By using the material, swelling due to water absorption of the graphite / resin-cured molded article can be reduced, so that elongation due to water absorption during battery operation and elongation over time due to moisture absorption when placed in the atmosphere can be suppressed.

  That is, the water absorption elongation when immersed in hot water at 90 ° C. that simulates the environment during battery operation (1) for 500 hours is 0.20% or less. If the elongation percentage is 0.20% or less, it is possible to prevent the separator from being damaged because warpage of the separator due to water absorption and cracking due to non-uniform elongation due to water absorption in the separator can be suppressed. The elongation percentage is measured from a change in length or width when immersed in hot water at 90 ° C. for 500 hours. For example, elongation percentage = [(length after immersion−length before immersion) / (length before immersion)] × 100.

  Also, since a mixed resin of benzylic ether type phenolic resin and novolak type phenolic resin is used as a binder, generation of ammonia and generation of organic carbon occurs at the time of curing compared to those using novolac type phenolic resin alone as a binder. These components are suppressed, and these components contained in the graphite / resin cured molded body are extremely reduced. As a result, it is possible to suppress the phenomenon that these components are eluted into the battery cell when the battery is in operation, preventing the proton movement of the solid polymer membrane and reducing the catalytic function of the electrode.

  That is, in order to suppress these phenomena, (2) the amount of ammonium ions eluted after immersion in hot water at 90 ° C. that simulates the environment during battery operation for 50 hours is set to 2 μg / g or less (3 ) By suppressing the TOC (total organic carbon) elution amount to 100 μg / g or less, it becomes possible to effectively prevent a decrease in battery performance such as a decrease in voltage and a decrease in output. Ammonium ions are measured by an ion chromatography method, and TOC (total organic carbon) is measured by a TOC meter (JIS K0805).

  In this case, the weight ratio of the resin solid content of the benzylic ether type phenol resin and the novolac type phenol resin in the mixed resin is set to 90:10 to 40:60. When the amount of benzylic ether type phenolic resin exceeds 90% by weight and the amount of novolac type phenolic resin is less than 10% by weight, the structure of the graphite / resin-cured molded body becomes non-uniform, whereas the amount of benzylic ether type phenolic resin When the weight ratio is less than 40% by weight and the amount of novolak type phenol resin exceeds 60% by weight, the curing rate of the mixed resin is slowed down, and molding takes time and productivity is lowered. A more preferable range is 90:10 to 50:50.

  Preferably, in the graphite / resin cured molded body forming the solid polymer fuel cell separator material of the present invention, the weight ratio of the resin solid content of the mixed resin to the graphite powder is set to 10:90 to 35:65. Is done. When the resin solid content is less than 10% by weight and the weight ratio of the graphite powder exceeds 90% by weight, the resin content is small and the fluidity at the time of molding is reduced, so that the structure of the molded body becomes non-uniform. If it exceeds 35% by weight and the graphite powder is less than 65% by weight, the electrical resistance increases and the battery performance is lowered.

  The method for producing a separator for a polymer electrolyte fuel cell according to the present invention comprises the steps of kneading a mixed resin solution prepared by dissolving a benzylic ether type phenol resin and a novolac type phenol resin in an organic solvent, and graphite powder. The preformed mold is filled with a molding powder obtained by volatilizing and then pulverizing the kneaded product, and the preform is inserted into the molding mold by pressing the upper mold and pressurizing to 1 to 10 MPa. Hot pressing is performed at a temperature of 20 to 50 MPa and a temperature of 150 to 250 ° C.

  In this case, the weight ratio of the resin solid content of the benzylic ether type phenol resin and the novolac type phenol resin in the mixed resin is set to 90:10 to 40:60. Preferably, the weight ratio of the resin solid content of the mixed resin to the graphite powder is set to 10:90 to 35:65.

  The benzylic ether type phenol resin alone has low fluidity, and it is difficult to uniformly knead with graphite powder, and the moldability deteriorates. Therefore, the novolac type phenol resin is added and mixed to increase the fluidity. Provided. At that time, the benzylic ether type phenolic resin and the novolac type phenolic resin are dissolved in an appropriate organic solvent such as alcohol or ether by adjusting the weight ratio of the resin solids to 90:10 to 40:60. A mixed resin solution having a low viscosity is prepared.

  When the amount of the benzylic ether type phenolic resin in the mixed resin exceeds 90% by weight and the weight ratio of the novolak type phenolic resin is less than 10% by weight, the fluidity of the mixed resin becomes low, and it is difficult to form uniformly. / The structure of the resin-cured molded body becomes non-uniform. On the other hand, when the amount of the benzylic ether type phenolic resin is less than 40% by weight and the amount of the novolac type phenolic resin is more than 60% by weight, the curing speed of the mixed resin becomes slow, and molding takes time and the productivity is lowered. A more preferable range is 90:10 to 50:50.

  The mixed resin solution is mixed with graphite powder and uniformly kneaded. In this case, adjusting the weight ratio of the resin solid content of the mixed resin and the graphite powder to a ratio of 10:90 to 35:65, and appropriate kneading such as a kneader, a pressure type kneader, or a twin screw kneader A uniform kneaded product is prepared by sufficiently kneading with a machine. After kneading, the organic solvent is volatilized and removed from the kneaded product by vacuum drying or air drying. The graphite powder to be used is preferably used by adjusting the particle size so that the average particle size is 50 μm or less and the maximum particle size is 100 μm or less.

  The weight ratio of the resin solid content of the mixed resin to the graphite powder is preferably set to 10:90 to 35:65. If the resin solid content is less than 10% by weight and the weight ratio of the graphite powder exceeds 90% by weight, the resin content is Since the flowability during molding is reduced due to the small amount, the structure of the molded body becomes non-uniform. On the other hand, when the resin solid content exceeds 35% by weight and the graphite powder is less than 65% by weight, the electrical resistance increases. This is because the battery performance is degraded.

  Since the surface of the kneaded material is covered with a resin coating, the conductivity is lowered. Therefore, the kneaded material is pulverized in order to prevent a decrease in conductivity by exposing the graphite portion. The pulverization is performed to pulverize to about 0.1 to 1 mm in order to uniformly fill the preform mold, thereby obtaining a molding powder. It is also possible to correct the material property anisotropy by pulverization of the kneaded material, thereby reducing the electrical resistance in the thickness direction of the plate-like molded body serving as the separator and reducing the anisotropy in the surface direction. You can also.

  The molding powder is uniformly filled in the cavity of the preforming mold, and an upper mold heated to a temperature equal to or higher than the melting point of the resin, for example, the resin melting point + 10 ° C., is placed on the preform and preliminarily molded at a pressure of 1 to 10 MPa. Make a renovation.

  This plate-like preform is inserted into a mold having a concavo-convex portion that forms a groove serving as a gas flow path of the separator by applying a release agent, and at a pressure of 20 to 50 MPa and a temperature of 150 to 250 ° C. By hot pressing, a separator material made of a graphite / resin-cured molded body in which the resin is cured and the graphite powder is bound with the cured resin and integrated is manufactured. The separator material thus manufactured is further machined as necessary.

  The novolak type phenolic resin used in the above production process preferably has a monomer amount of 5% by weight or less, a dimer amount of 20% by weight or less, and a plate flow at 125 ° C. of 150 mm or more.

  When the monomer amount exceeds 5% by weight and the dimer amount exceeds 20% by weight, the low molecular weight component in the novolak type phenol resin increases, and the amount of low boiling point components gasified and volatilized during molding and curing increases. The pores are easily formed in the resin cured molded body, and the gas impermeability is lowered.

  The plate flow is a parameter measured by JIS K6909 “Phenolic Resin Test Method for Grinding Wheels” and shows the fluidity of phenolic resin when heated and melted at 125 ° C. When this value is below 150 mm, the high molecular weight component is Since the moldability increases and the formability deteriorates, the structure tends to become non-uniform.

  The resin properties can be adjusted by, for example, removing the low-volatile components of the monomer or dimer by heating under reduced pressure, separating and removing the monomer, using the difference in solubility in the solvent between the dimer and the polymer component, or It is adjusted by a method of selectively promoting polymerization of monomers and dimers by controlling the catalyst and reaction temperature during resin synthesis.

  Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1 to 4 and Comparative Example 4
A benzylic ether type phenolic resin is dissolved in acetone so that the resin solid content is 60% by weight, and the resin solution A is obtained. The monomer amount is less than 1% by weight, the dimer amount is 10% by weight or less, A novolac type phenol resin having a plate flow of 226 mm was dissolved in methanol so that the resin solid content was 70% by weight to prepare a resin solution B. The resin solutions A and B were mixed at different quantitative ratios to prepare mixed resin solutions having different weight ratios of resin solids of benzylic ether type phenol resin and novolac type phenol resin.

  For the graphite powder, artificial graphite powder having an average particle size of 40 μm and a particle size adjusted to a maximum particle size of 80 μm or less is used, and the mixed resin solution and the graphite powder are kneaded so that the weight ratio of the resin solid content to the graphite powder is 20:80. And kneaded for 1 hour. The kneaded product was air-dried at room temperature for 24 hours and further vacuum-dried to volatilize and remove the organic solvent. Next, after the kneaded product was pulverized, the particle size was adjusted to obtain a molding powder of 0.1 to 0.5 mm.

  The molding powder was filled evenly into the preforming mold, and the upper mold heated to 70 ° C. was placed and pressurized at a pressure of 3 MPa for 10 seconds to produce a preformed plate-like preform.

  Fluorine-based mold release agent is applied to a molding die having an outer shape of 270 × 270 mm in which a groove shape having a width of 1 mm and a depth of 0.6 mm is engraved within a range of 200 × 200 mm, and a preform is applied to the molding die. It was inserted and hot-press molded at a pressure of 40 MPa and a temperature of 180 ° C. In this way, a separator material (200 × 200 mm, maximum thickness) comprising a graphite / resin-cured molded body in which graphite powder is bound with a cured resin and having a gas channel and a groove having a width of 1 mm and a depth of 0.6 mm is formed. A thin part thickness of 0.45 mm) was produced.

  Test pieces (6 × 30 mm) cut out from these separator materials were immersed in a sealed container containing 50 ml of distilled water and held in a thermostat at 90 ° C. The ammonium ion concentration and the TOC (total organic carbon) concentration after holding for 50 hours were measured to determine the ammonium ion elution amount and the TOC (total organic carbon) elution amount.

  Moreover, the water absorption elongation rate was calculated | required by immersing a test piece in the airtight container containing 50 ml distilled water, and measuring the change of the length after hold | maintaining for 500 hours in a 90 degreeC thermostat. Furthermore, the water absorption elongation rate was calculated | required by measuring the change of the length after immersing in 50% ethylene glycol aqueous solution and hold | maintaining for 500 hours in a 90 degreeC thermostat.

The material properties of the test pieces were measured by the following method.
(1) Bending strength (MPa);
Measured at room temperature and 90 ° C according to JISR1601.
(2) Specific resistivity (mΩ · cm);
Measured according to JISC2525.
(3) Contact resistance (mΩ · cm ² );
Measured at 1A energization while contacting the test pieces at a pressure of 1 MPa.
(4) Gas permeability coefficient (mol · m · m ^-2 · sec ^-1 · MPa ^-1 );
Measure the gas permeation per unit cross-sectional area when applying a differential pressure of 0.2 MPa with nitrogen gas.

Comparative Examples 1-3
When only the novolac type phenol resin is used as the binder resin (Comparative Example 1), when only the benzylic ether type phenol resin is used (Comparative Example 2), when the resol resin is used (Comparative Example 3), A graphite / resin cured molded body was produced in the same manner as in the above Example, and its characteristics were measured by the same method.

  The obtained results are shown in Table 1.

  A fuel cell for 10 cells was assembled by combining the separator material of Example 1 with a solid polymer membrane and a gas diffusion electrode. The temperature was raised to 90 ° C., and humidified hydrogen gas and air were sent from the manifold to the fuel electrode and the air electrode of the cell to cause a fuel cell reaction to generate electricity. When the voltage in each cell after the lapse of 24 hours was measured, the average voltage was 0.75V. Furthermore, as a result of continuously generating power up to 2000 hours and measuring the voltage of each cell after 2000 hours, it was 0.73 V and the voltage drop rate was 3%. On the other hand, as a result of assembling a similar battery stack using the separator material of Comparative Example 1 and generating power, the voltage after 24 hours was 0.73 V, but the voltage after 2000 hours was 0.63 V. The voltage drop rate was 14%.

1 is a partial cross-sectional view showing a schematic structure of a solid polymer fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Gas channel groove 3 Cathode 4 Anode 5 Electrolyte membrane 6 Sealing material

Claims (5)

The graphite powder is combined with a mixed resin of a benzeric ether type phenolic resin and a novolak type phenolic resin having a monomer amount of 5% by weight or less and a dimer amount of 20% by weight or less in a weight ratio of 90:10 to 40:60. A separator for a polymer electrolyte fuel cell, comprising a graphite / resin-cured molded body bound as a material.   The separator material for a polymer electrolyte fuel cell according to claim 1, wherein the weight ratio of the resin solid content of the mixed resin to the graphite powder is 10:90 to 35:65. A method for producing a separator for a polymer electrolyte fuel cell according to claim 1 or 2,
The resin solid content weight ratio of the benzylic ether type phenol resin and the novolak type phenol resin having a monomer amount of 5% by weight or less and a dimer amount of 20% by weight or less was adjusted to 90:10 to 40:60 and dissolved in an organic solvent. After kneading the mixed resin solution and the graphite powder, the organic solvent is volatilized and removed, and then the molding powder obtained by pulverizing the kneaded product is filled into a preforming die, and the upper die is placed and pressurized to 1 to 10 MPa. A method for producing a separator material for a polymer electrolyte fuel cell, wherein a preform that has been preformed is inserted into a mold and hot-press molded at a pressure of 20 to 50 MPa and a temperature of 150 to 250 ° C.   The manufacturing method of the separator material for polymer electrolyte fuel cells of Claim 3 which adjusts the weight ratio of resin solid content of mixed resin and graphite powder to 10: 90-35: 65, and knead | mixes.   The separator for a polymer electrolyte fuel cell according to claim 3 or 4, wherein the monomer amount of the novolak type phenol resin is 5% by weight or less, the dimer amount is 20% by weight or less, and the plate flow at 125 ° C is 150 mm or more. Production method.

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