JP2011119124A - Manufacturing method for separator of fuel cell, and the separator of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a separator of a fuel cell and a separator of a fuel cell capable of improving durability of the separator, without causing poor molding and insufficient electrical conductivity. <P>SOLUTION: In the manufacturing method for the separator of the fuel cell which can mold the separator for the fuel cell, by pressurizing and cooling after heating and pressurizing a powdery molding material 1 by filling up to a molding die 10, the molding material 1 is prepared, by heating and kneading a designated resin and graphite particles at a temperature exceeding melting-start temperature of the designated resin; and then the powdery molding material 1 is prepared by mixing at temperature, under a melting-start temperature of the designated resin by adding graphite particles into the pulverized molding material 1, after pulverizing by crushing the molding material. Insufficient electrical conductivity of the separator can be solved, since the conductivity of the pulverized molding material 1 is not excessively impaired by sticking the designated resin around each graphite particle. Furthermore, it is also solved that poor mechanical characteristics and poor conductivity of the separator used for the fuel cell occur locally, since the local variation of the designated resin and graphite is restrained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a fuel cell separator that contributes to prevention of global warming, energy saving, and the like, and a fuel cell separator.

  Fuel cell separators used in fuel cells are required to have electrical conductivity, mechanical properties, and durability as important properties. In addition to these, high productivity is required in order to realize low prices and widespread use. It has been.

  When manufacturing such a fuel cell separator, although not shown, a predetermined amount of resin and graphite are mixed to form a molding material, and the molding material is heated and pressed to mold the fuel cell separator. (See Patent Documents 1, 2, 3, and 4). As the predetermined resin, a thermoplastic resin or a thermosetting resin is used. Moreover, in order to ensure electroconductivity, graphite is mix | blended abundantly 2-6 times by mass ratio with respect to the amount of resin.

Japanese Patent No. 4260428 Japanese Patent No. 3693275 JP 2008-078023 A Japanese Patent Laid-Open No. 2001-085030

  Conventional fuel cell separators have a high graphite ratio and poor flowability of the molding material in order to ensure conductivity as described above, so there is a limit to the amount of graphite mixed, and the preparation of the molding material is very difficult. There is a problem that it is difficult. Patent Documents 1 and 2 disclose a method of melt-kneading a thermoplastic resin and powdered graphite. In this method, excessive thermoplastic resin is present around the graphite during melt-kneading. Adhesion hinders conductivity, resulting in insufficient conductivity.

  In view of this point, Patent Document 3 discloses a method in which a thermoplastic resin is mixed with graphite without melting to obtain a molding material. In this method, the resin and graphite are locally localized. Since the variation becomes large, there arises a new problem that the surface state of the fuel cell separator is deteriorated, and mechanical characteristics and conductivity defects of the fuel cell separator are locally generated. This problem can be solved to some extent if the resin is used after being pulverized to the same particle size as that of graphite or less, but it is difficult to completely solve the problem.

  Further, Patent Document 4 shows a method of using a thermosetting resin. In this method, when the thermosetting resin is made into a liquid and mixed with graphite, a molding material is prepared and used, Similar to Patent Documents 1 and 2, the thermosetting resin may be excessively adhered to the periphery of graphite to inhibit the conductivity, leading to a lack of conductivity. Also, if a molding resin is prepared by mixing a powder resin with graphite, as in Patent Document 3, the local variation between the resin and graphite increases, so that the surface condition of the fuel cell separator deteriorates, Mechanical properties and conductivity defects of the battery separator are locally generated.

  Moreover, when using a thermosetting resin, since a long time is required for hardening of a thermosetting resin, improvement of productivity cannot be aimed at. Furthermore, since uncured components and reaction products are likely to remain as residues in the fuel cell separator, the residues may elute during the operation of the fuel cell, thereby reducing the durability of the fuel cell. In order to solve this problem, a method of removing the residue by post-heating has been proposed, but since a sufficient effect cannot be expected, productivity cannot be improved.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a method for manufacturing a fuel cell separator and a fuel cell separator that can improve durability without incurring molding defects or lack of conductivity. It is said.

In the present invention, in order to solve the above-mentioned problem, a powdery molding material is filled in a molding die, heated and pressurized, and then pressurized and cooled to obtain a fuel cell separator,
A predetermined resin and graphite particles are heated and kneaded at a temperature equal to or higher than the melting start temperature of the predetermined resin to prepare a preformed material, the preformed material is pulverized and powdered, and the powdered preformed material It is characterized in that a powdery molding material is prepared by adding graphite particles to and mixing at a temperature lower than the melting start temperature of a predetermined resin.

In addition, the linear expansion coefficient in the surface direction of the fuel cell separator can be set in a range of −60 to + 20% or less of the linear expansion coefficient of the molding die.
Further, the addition amount of graphite particles in the preforming material is the addition amount of graphite particles in the molding material x 0.5 or more and the addition amount of graphite particles in the molding material x less than 1.0, and the average of the graphite particles The particle size can be 5 to 500 μm.

  Furthermore, in order to solve the above-mentioned problems, the present invention is characterized in that a fuel cell separator is manufactured by the method for manufacturing a fuel cell separator according to claim 1, 2 or 3.

  Here, the predetermined resin and the graphite particles in the claims can be agitated and mixed before heating and kneading. The predetermined resin can be a thermoplastic resin or a thermosetting resin. The powdered preforming material can be appropriately classified with a classifier or a sieve.

According to the present invention, there is an effect that durability can be improved without causing molding defects and lack of conductivity.
Further, when the linear expansion coefficient in the surface direction of the fuel cell separator is set to a range of −60 to + 20% or less of the linear expansion coefficient of the molding die, the fuel cell separator is removed from the molding die. Further, it is possible to eliminate the possibility that cracks and cracks occur in the fuel cell separator and that molding defects are caused.

  Further, if the addition amount of the graphite particles in the preforming material is not less than 0.5 addition amount of the graphite particles in the molding material and less than 1.0 addition amount of the graphite particles in the molding material, the predetermined amount The variation between the resin and the graphite particles is reduced, the mechanical strength and conductivity of the fuel cell separator are improved, and an increase in gas permeability can be expected to be prevented. In addition, the resin is less likely to adhere to the surface of the graphite particles, and the decrease in conductivity of the fuel cell separator can be suppressed. In addition, since it is not necessary to increase the amount of graphite particles added, the fluidity of the molding material can be improved and the fuel cell separator can be easily processed.

  Further, if the average particle diameter of the graphite particles is 5 to 500 μm, it is possible to prevent the working environment from deteriorating or secondary aggregation to occur and the uniform dispersibility with a predetermined resin from being lowered, and the fuel It becomes possible to prevent a decrease in mechanical strength and conductivity in the battery separator. Moreover, since it can suppress that the melt fluidity of a molding material falls, it becomes possible to shape | mold a separator for fuel cells easily. Furthermore, it is possible to prevent an increase in the gap between the graphite particles, and it is possible to suppress a decrease in electrical conductivity or a decrease in mechanical properties due to a decrease in contact area with a predetermined resin.

It is a section explanatory view showing typically the molding die in the embodiment of the manufacturing method of the separator for fuel cells concerning the present invention. It is a plane explanatory view showing typically an embodiment of a separator for fuel cells concerning the present invention. It is a section explanatory view showing typically an embodiment of a separator for fuel cells concerning the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A method for manufacturing a fuel cell separator according to this embodiment includes a powdery molding material 1 as a molding die as shown in FIGS. 10 is a method of forming a fuel cell separator 20 having a plurality of grooves 22 by heating and pressurizing and then pressurizing and cooling. A molding resin 1 is obtained by heating and kneading a predetermined resin and graphite particles. The powdery molding material 1 is prepared by preparing and molding this molding material 1 and adding and mixing graphite particles.

The powdery molding material 1 is prepared by molding the molding material 1 by heating and kneading at least a predetermined resin and graphite particles at a temperature equal to or higher than the melting start temperature of the predetermined resin. Thereafter, graphite particles are added to the powdered molding material 1 and mixed at a temperature lower than the melting start temperature of a predetermined resin.
As the predetermined resin of the molding material 1, a thermoplastic resin or a thermosetting resin can be used. As the thermoplastic resin, a crystalline thermoplastic resin or an amorphous thermoplastic resin can be used.

  Examples of the thermoplastic resin include an olefin resin [low density polyethylene (LDPE) resin, high density polyethylene (HDPE) resin, very low density polyethylene (VLDPE) resin, linear low density polyethylene (LLDPE) resin, ultra high molecular weight]. Polyethylene (UHMW-PE) resin, homopolypropylene resin, polypropylene (PP) resin such as block polypropylene resin or random polypropylene resin, polymethylpentene (PMP) resin, cyclic olefin resin, etc.], polystyrene (PS) resin [Atactic Polystyrene resin, syndiotactic polystyrene resin, etc.], polyester resin [polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene naphthalate (PTT) Resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, polylactic acid (PLA) resin, etc.], polycarbonate (PC) resin, polyamide resin [nylon 6, nylon 11, nylon 12, nylon 46 , Nylon 66, nylon 6T, nylon 61, nylon 9T, nylon M5T, nylon MXD, nylon 610, nylon 612, etc.], polyphthalamide resin, polyarylene (PAR) resin, modified polyphenylene ether resin, fluorine-based resin [tetrafluoro Ethylene / ethylene copolymer (ETFE) resin, tetrafluoroethylene / hexafluoropropyl copolymer (FEP) resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) resin, etc. Polysulfone resins (polysulfone (PSU) resin, polyethersulfone (PES) resin, polyphenylsulfone (PPSU) resin, etc.), polyarylene sulfide resins (polyphenylene sulfide (PPS) resin, polyphenylene sulfide sulfone resin, or Polyphenylene sulfide ketone resin], liquid crystal polymer, or polyarylene ketone resin [polyetherketone (PEK) resin, polyetherketoneketone (PEKK) resin, polyetheretherketoneketone (PEEKK) resin, polyetheretherketone (PEEK) Resin, polyetherketone etherketoneketone (PEKEKK) resin, etc.], polyimide resin [polyetherimide (PEI) resin, polyamideimide (PAI) resin, polyimide ( PI) resin, etc.], but is not limited thereto.

  Among these thermoplastic resins, from the viewpoint of mechanical properties, chemical stability (hydrolysis resistance), availability, and cost of the fuel cell separator 20, polypropylene resin, cyclic olefin resin, polyphenylene sulfide Polysulfone-based resins such as resins, polyetherimide resins, polysulfone resins, polyether sulfone resins, and polyphenylene sulfone resins are preferable. A thermoplastic resin may be used individually by 1 type, and can also use 2 or more types together. The shape of the thermoplastic resin is not particularly limited to powder, granule, lump, granule, pellet or the like.

  Examples of the thermosetting resin include phenol resin, epoxy resin, diallyl phthalate resin, unsaturated polyester resin, polyimide resin, silicone resin, polyurethane resin, urea resin, melamine resin, etc., but are not limited thereto. is not. These thermosetting resins may be used alone or in combination of two or more. The shape of the thermosetting resin is not limited to powder, granule, lump, granule, pellet or the like.

  The predetermined resin may be either a thermoplastic resin or a thermosetting resin, but is preferably a thermoplastic resin. This is because in the case of a thermosetting resin, it takes a long time to cure, and the productivity cannot be improved. In addition, uncured components and reaction products are likely to remain in the fuel cell separator 20, and the residue is eluted during the operation of the fuel cell, thereby reducing the durability of the fuel cell. Moreover, since thermosetting resin undergoes curing shrinkage, the design of the molding die 10 becomes complicated. Furthermore, although thermoplastic resins can be recycled, thermosetting resins cannot be recycled after curing, this is based on the reason that product costs increase and the amount of waste increases.

  As graphite particles, natural graphite composed of scaly graphite, scaly graphite, massive graphite, earthy graphite, etc., expanded graphite obtained by chemically treating scaly graphite with concentrated sulfuric acid, etc., and heat-treating expanded graphite at high temperature Expanded graphite, artificial graphite, and the like. Among these graphite particles, excellent conductivity can be obtained by using artificial graphite which has few impurities and elution and has high purity. The graphite particles may be used alone or in combination of two or more.

  The average particle diameter of the graphite particles is 5 to 500 μm or less, preferably 10 to 300 μm or less, more preferably 3 to 200 μm or less. This is because when the average particle size of the graphite particles is less than 5 μm, the graphite particles soar during the work, the working environment is deteriorated, or secondary agglomeration occurs and the uniform dispersibility with a predetermined resin is reduced, This is based on the reason that the conductivity of the fuel cell separator 20 is lowered. Further, since the melt fluidity of the molding material 1 is lowered, it is based on the reason that it is difficult to mold the thin fuel cell separator 20.

  On the other hand, when the average particle diameter of the graphite particles exceeds 500 μm, the gap between the graphite particles becomes large, so that it is difficult to achieve high filling, and the contact area with a predetermined resin is reduced, resulting in mechanical characteristics. It is because it falls. In addition, two or more kinds of graphite particles having different particle diameters can be used in combination, and in the case of using these in combination, since high packing is possible, a highly conductive fuel cell separator 20 can be obtained. .

  Graphite particles include, for example, silane coupling agents [3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropylethoxysilane, etc.], titanate coupling agents [isopropyl triisostearoyl titanate, Tetraoctyl bis (dioctyl phosphite) titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, tetraisopropyl bis (dioctyl phosphite) titanate, isopropyl tri (N-amitoethyl / aminoethyl) titanate, etc.), aluminate coupling agent Various coupling agents such as [acetoalkoxyaluminum diisopropylate], surfactants [anionic surfactants, cationic surfactants, zwitterionic surfactants , Nonionic surfactants, etc.], styrene, can be treated with an organic compound such as acrylic.

  The composition ratio between the resin of the molding material 1 and the graphite particles varies depending on the type of resin used, but the composition volume ratio of the graphite particles is 50% by volume to 80% by volume, preferably 60% by volume to 75% by volume. This is based on the reason that the conductivity required for the fuel cell separator 20 cannot be obtained when the amount is less than 50% by volume. On the other hand, when it exceeds 80% by volume, the melt fluidity of the molding material 1 is lowered, and the mechanical strength and workability are lowered.

  When the molding material 1 is prepared by heating and kneading a predetermined resin and graphite particles at a temperature equal to or higher than the melting start temperature of the predetermined resin, the amount of graphite particles in the molding material 1 is as follows. The addition amount of x 0.5 or more and the addition amount of graphite particles in the molding material 1 x less than 1.0 are preferable. This is because when the addition amount of graphite particles is less than the addition amount of graphite particles in the molding material 1 × 0.5, local variation between the resin and the graphite particles becomes large, and the surface of the fuel cell separator 20 is increased. This is because scale-like patterns and avatar-shaped fine dents appear on the surface, the mechanical strength and conductivity of the fuel cell separator 20 decrease, and the gas permeability increases.

  On the other hand, when the addition amount of the graphite particles is not less than 1.0 addition amount of the graphite particles in the molding material 1, the resin adheres excessively to the surface of the graphite particles, so the graphite particles are in contact with each other. As a result, the conductivity of the fuel cell separator 20 is greatly reduced. Therefore, since the amount of graphite particles added is increased, the melt fluidity of the molding material 1 is lowered, and the workability of the fuel cell separator 20 is hindered.

  In addition to a predetermined resin and graphite particles, a conductive material can be selectively added to the molding material 1. Examples of the conductive material include a metal-based material and a carbon-based material, and these may be used alone or in combination. Examples of metal materials include nickel, iron, cobalt, boron, lead, chromium, copper, aluminum, titanium, bismuth, tin, tungsten, molybdenum, platinum, gold, silver, and conductive ceramics described in JP-A-2007-273458. Etc. can be used. Examples of the conductive ceramic include metal carbide, metal nitride, metal carbonitride, metal boride, and metal silicide.

  Examples of the metal carbide include tungsten carbide, silicon carbide, tantalum carbide, titanium carbide, niobium carbide, zirconium carbide, molybdenum carbide, vanadium carbide, chromium carbide, and boron carbide. Examples of the metal nitride include chromium nitride, aluminum nitride, molybdenum nitride, zirconium nitride, tantalum nitride, titanium nitride, gallium nitride, niobium nitride, vanadium nitride, scandium nitride, lanthanum nitride, silicon nitride, and boron nitride. To do. The metal carbonitride includes, for example, titanium carbonitride and zirconium carbonitride.

  Examples of the metal boride include titanium boride, zirconium boride, hafnium boride, vanadium boride, niobium boride, tantalum boride, chromium boride, molybdenum boride, tungsten boride, and lanthanum boride. Metal silicides include titanium silicide, zirconium silicide, hafnium silicide, niobium silicide, tantalum silicide, chromium silicide, molybdenum silicide, vanadium silicide, lanthanum silicide, manganese silicide, cobalt silicide, nickel silicide, copper silicide, tungsten silicide. can give.

  As the carbon-based material, carbon black, carbon nanotube, carbon nanohorn, fullerene, amorphous carbon, carbon fiber and the like can be used. As carbon black, furnace black, channel black, acetylene black, thermal black, etc. can be used. Moreover, as a carbon nanotube, a single wall carbon nanotube, a multi-walled carbon nanotube, etc. can be used. Examples of the carbon fiber include bread-based carbon fiber and pitch-based carbon fiber.

  In addition to a predetermined resin, graphite particles, and conductive material, a predetermined additive can be selectively added to the molding material 1. Examples of the predetermined additive include an antioxidant, a light stabilizer, an ultraviolet absorber, a plasticizer, a lubricant, a flame retardant, an antistatic agent, a heat resistance improver, an inorganic filler, and an organic filler.

  The melting start temperature when preparing the molding material 1 by heating and kneading a predetermined resin and graphite particles at a temperature equal to or higher than the melting start temperature of the predetermined resin varies depending on the type of the predetermined resin. When the predetermined resin is a thermoplastic resin, it differs between a crystalline thermoplastic resin such as homopolypropylene resin or polyphenylene sulfide resin and an amorphous thermoplastic resin such as polyetherimide resin or polyethersulfone resin. The melting start temperature indicates a melting point in the case of a crystalline thermoplastic resin and a glass transition temperature in the case of an amorphous thermoplastic resin.

  In the case of a crystalline thermoplastic resin, the heating and kneading temperature between the predetermined resin and the graphite particles is from the melting start temperature to less than the thermal decomposition temperature, preferably from the melting start temperature + 30 ° C. to less than the thermal decomposition temperature, and is amorphous. In the case of a thermoplastic resin, the melting start temperature is lower than the thermal decomposition temperature, preferably the melting start temperature + 50 ° C. is lower than the thermal decomposition temperature, more preferably the melting start temperature + 100 ° C. is lower than the thermal decomposition temperature.

  Heat kneading of a predetermined resin and graphite particles is performed by various types of kneaders such as a pressure kneader, a flashing kneader, and a KEX kneader, and various types of extrusion such as a single screw extruder, a twin screw extruder, a triaxial extruder, and a four screw extruder. It can be carried out using a heating kneader such as a machine, a Banbury mixer, or a planetary mixer. In addition, from the viewpoint of improving dispersibility before heating and kneading the predetermined resin and graphite particles as necessary, a Nauter mixer, a tumbler mixer, a hensil mixer, at a temperature lower than the melting start temperature of the predetermined resin, Stirring and mixing may be performed using a ribbon blender, a stirrer such as a V-type mixer, or a ball mill.

  The molding material 1 prepared by heating and kneading is pulverized and pulverized in order to mix the graphite particles again. The pulverization of the molding material 1 can be performed in one step, two steps, or a plurality of steps as required. Examples of the method for pulverizing the molding material 1 include a shear pulverization method, an impact pulverization method, a collision pulverization method, a freeze pulverization method, and a solution pulverization method. Among these, the viewpoint of simplification of the process and cost reduction Therefore, the shear pulverization method and the impact pulverization method are optimal.

  In the case of other pulverization methods, that is, the collision pulverization method, a special pulverization apparatus is required, which increases the cost. In the case of the freeze pulverization method, the heated kneaded material is once frozen with a low-temperature liquid such as liquid nitrogen. Since it grind | pulverizes after making it process, a process will become complicated and will cause a high cost. In the case of the solution pulverization method, the pulverization process is complicated, and the solution is used, so that the solution may remain in the pulverized product.

  Although the pulverization temperature of the molding material 1 varies depending on the type of resin, it is usually optimum that the temperature is lower than the melting start temperature, preferably the melting start temperature is −70 ° C. or lower, preferably the melting start temperature is −100 ° C. This is because if the pulverization temperature of the molding material 1 is equal to or higher than the melting start temperature, the molding material 1 is softened and cannot be pulverized. Moreover, when concretely crushing the molding material 1, use a grinder such as a hammer mill, a cutter mill, a feather mill, a flake crusher, a pin mill, an impact mill, a Victory mill, a ball mill, a jet mill, etc., a crusher, and a cutting machine. Can do.

  The average particle size of the powdered molding material 1 is preferably 5 to 500 μm or less, more preferably 10 to 300 μm or less, and still more preferably 30 to 200 μm or less. This is because, when the average particle size of the molding material 1 is less than 5 μm, the molding material 1 is swollen during the working, the working environment is deteriorated, and the uniform dispersion with the graphite particles to be added again due to secondary agglomeration. Based on the reason for the decline. On the other hand, when the average particle diameter of the molding material 1 exceeds 500 μm, a small dent is generated on the surface of the fuel cell separator 20, so that the mechanical strength and conductivity of the fuel cell separator 20 are locally increased. Based on the reason that it decreases and the gas permeability increases locally.

  The powdered molding material 1 is appropriately classified with a sieve screen, a vibrating sieve, a vibrating screen, an ultrasonic sieve, a micro separator, a micron separator, a turbo classifier classifier or a sieve as necessary.

  The powdered molding material 1 is prepared by adding graphite particles and mixing at a temperature lower than the melting start temperature of a predetermined resin. The molding material 1 and the graphite particles can be mixed using a nauter mixer, a tumbler mixer, a hensil mixer, a ribbon blender, a stirrer such as a V-type mixer, a ball mill, or the like. The mixing time is 5 to 120 minutes, preferably 10 to 90 minutes, more preferably 30 to 60 minutes.

Once the powdery molding material 1 is prepared, the molding die 10 is filled with a predetermined amount of the molding material 1 without being preformed, heated and pressurized, and then pressurized and cooled to produce a fuel cell. The separator 20 is compression molded.
As shown in FIG. 1, the molding die 10 includes a convex upper mold 11 having a molding portion 12 and a concave lower mold 13 having a molding portion 12 facing each other so as to be capable of clamping. The upper mold 11 and the lower mold 13 are made of a predetermined material and are mounted on a molding machine (not shown).

  Examples of the material of the molding die 10 include carbon steel (low carbon steel, high carbon steel, ordinary steel, special steel, low alloy steel, high tensile steel, etc.), stainless steel (ferritic stainless steel, martensite type). Iron-chromium stainless steel made of stainless steel, austenitic stainless steel, iron-chromium-nickel stainless steel such as austenitic / ferritic stainless steel), low alloy steel (molybdenum steel, chromium-molybdenum steel, molybdenum-) Vanadium steel, chromium-molybdenum-vanadium steel, chromium-nickel-molybdenum steel, etc.), ferritic heat-resistant steel with a chromium content of 16% or more, heat-resistant alloys (nickel-iron-cobalt alloy, nickel-chromium-titanium alloy, cobalt-chromium) -Tungsten alloy, etc.) and steel materials such as pre-hardened steel.

The linear expansion coefficient of various steel materials varies depending on the type and composition. For example, the linear expansion coefficient of carbon steel is 10 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C., although it varies depending on the carbon content. The linear expansion coefficient of stainless steel varies depending on the composition, but in the case of ferritic stainless steel, 9 × 10 ^{−6 to} 11 × 10 ⁻⁶ / ° C., and in the case of austenitic stainless steel, 10 × 10 ^−6. to 13 is a × ^{10 -6} / ℃. The linear expansion coefficient of the Purihado steel varies depending on the composition, it is ^{10 × 10 -6 ~13 × 10 -6} / ℃.

  If necessary, the upper mold 11 and the lower mold 13 of the molding die 10 are made of hard chromium, zinc, nickel chromium, nickel nitride, titanium nitride, nickel-phosphorus-polytetrafluoroethylene, nickel-phosphorus, nickel- Surface treatment can be applied by plating with boron, nickel-phosphorus-boron, etc., diamond-like carbon (DLC) coating, TiAl coating, titanium nitride coating, titanium carbide coating, silicon carbide coating, chromium nitride coating, etc. .

  When the molding die 10 is filled with a predetermined amount of the molding material 1, the molding amount of the molding material 1 differs depending on the molding location of the fuel cell separator 20. As a specific filling method, (1) the lower mold 13 of the molding die 10 is filled with the measured molding material 1 and made uniform with a scraper or the like, and a plurality of grooves 22 of the fuel cell separator 20 are molded. Scraping the molding part 12 of the molding die 10 to be scraped off with a scraper or the like and filling the molding material 1 in a well-balanced manner. (2) Considering the shape of the fuel cell separator 20, the lower mold 13 of the molding die 10. A method of filling the molding material 1 while increasing / decreasing it with a dispenser is applicable.

When filling the molding die 10 with a predetermined amount of the molding material 1, it is preferable to set the molding temperature of the molding die 10 lower than the melting start temperature of the predetermined resin. When the molding die 10 is heated and pressurized, the molding die 10 filled with the molding material 1 is set between a pair of hot plates heated to a predetermined temperature of the molding machine and heated and pressurized. Further, the heating temperature of the molding die 10 is preferably about the melting start temperature to less than the thermal decomposition temperature, preferably about the melting start temperature + 30 ° C. to + 150 ° C., regardless of the crystallinity and the amorphous property of the resin. The pressing pressure of the molding die 10 needs to be 300 kg / cm ² or more.

  When the molding die 10 is heated and pressurized, the molding material 1 is pressurized, a large number of graphite particles come into contact with each other, and a void into which the resin flows is defined therebetween. Then, by heating the molding die 10, the resin starts to flow in a temperature range equal to or higher than the melting start temperature of the resin, and the resin flows into the gaps between the many graphite particles. Therefore, good conductivity can be expected without excessive adhesion of the resin around the graphite particles.

The heating and pressing time of the molding die 10 may be a time for the resin to flow into the gaps between the many graphite particles. Specifically, for example, in the case of polyphenylene sulfide resin, the melting start temperature is + 100 ° C. and the pressure of 800 kg / cm ² with respect to the projected area of the fuel cell separator 20 is preferably 20 to 100 seconds or less.

When the molding die 10 is heated and pressurized, the molding die 10 is pressurized and cooled, the mold is opened, and the fuel cell separator 20 is removed, whereby the fuel cell separator 20 shown in FIGS. Can be manufactured. As a method of pressurizing and cooling the molding die 10 under a pressure of 800 kg / cm ² , (1) the molding die 10 is removed and set between a pair of cooled hot plates of another molding machine. And (2) a method of pressurizing and cooling while the molding die 10 is set between a pair of hot plates of a molding machine.

  Although the molding die 10 varies depending on the resin in the molding material 1, in the case of a crystalline resin, it is cooled to a melting start temperature or lower, preferably a crystallization temperature or lower, more preferably a glass transition point or lower. On the other hand, in the case of an amorphous resin, it is cooled to a melting start temperature or lower, preferably a melting start temperature −100 ° C. or lower, more preferably a melting start temperature −150 ° C. or lower. This is because if the molding die 10 is cooled to such a temperature range, the conductivity of the fuel cell separator 20 can be improved, and the warpage and the bending can be reduced.

However, since the productivity deteriorates due to a decrease in the cooling temperature, the fuel cell separator 20 is demolded at a high temperature that satisfies the electrical conductivity, and in the case of a crystalline resin, a glass transition point of −30 ° C. or higher to a crystal In the case of an amorphous resin below the crystallization temperature, the warping or bending of the fuel cell separator 20 may be corrected by aligning at a melting start temperature of −30 ° C. or higher and lower than the melting start temperature. The aligning is preferably performed by stacking the fuel cell separator 20 and placing a weight of 0.05 kg / cm ² thereon.

  The fuel cell separator 20 may be formed by any method such as compression molding, injection molding, injection compression molding, etc., but excellent heat resistance and water resistance can be obtained, and the durability of the fuel cell can be obtained. It is preferable to employ a compression molding method with a small amount of eluted ions and heavy metals that adversely affect the process. In addition, according to the compression molding method, the amount of the predetermined resin can be increased and the amount of graphite particles can be reduced, so that good conductivity can be obtained with a small number of graphite particles, and mechanical strength reduction and molding defects can be prevented. It can be expected to improve dimensional accuracy.

  Further, a step of preparing a molding material 1 by heating and kneading a predetermined resin and graphite particles at a temperature equal to or higher than a melting start temperature of the predetermined resin, a step of pulverizing the molding material 1, and making the powder The process of preparing the molding material 1 by adding graphite particles to the molding material 1 and mixing at a temperature lower than the melting start temperature of the predetermined resin effectively eliminates the possibility of molding defects and insufficient conductivity, Improvement of mechanical strength can be expected.

  As shown in FIGS. 2 and 3, the fuel cell separator 20 includes a planar rectangular base plate 21, and the center or flat surface of the base plate 21 has fuel or product water lined up in a horizontal row. A plurality of discharge grooves 22 are arranged in a substantially plane S shape and function to be stacked together with an electrolyte layer, an air electrode, and a fuel electrode to constitute a fuel cell.

  In order to increase the hydrophilicity, the fuel cell separator 20 is selectively subjected to surface treatment selectively. Specifically, the surface of the molded fuel cell separator 20 is subjected to flame treatment, corona treatment, ultraviolet treatment, plasma treatment, metal particles, ceramic particles, glass beads, resin particles, plant particles, etc. A blasting process is performed. In addition, the plurality of grooves 22 are perforated with a plurality of through holes 23 arranged in the periphery thereof, and each groove 22 is formed to have a substantially U-shaped cross section.

  As a method of forming the plurality of grooves 22 in the fuel cell separator 20, a method of forming the plurality of grooves 22 in the molded fuel cell separator 20 by a mechanical processing method such as cutting or the like, a plurality of molding molds 10 are used. There are a method for forming the fuel cell separator 20 having the grooves 22 and a method for forming the plurality of grooves 22 in the fuel cell separator 20 by a stapling method, and any of them may be used.

  The linear expansion coefficient in the surface direction of the fuel cell separator 20 is in the range of −60 to + 20% or less of the linear expansion coefficient of the molding die 10. This is because when the linear expansion coefficient in the surface direction of the fuel cell separator 20 is out of the range, cracks and cracks occur in the fuel cell separator 20 when the fuel cell separator 20 is removed from the molding die 10. However, it is based on the reason of causing a molding defect.

  According to the above, since the ratio of graphite can be reduced and the fluidity of the molding material 1 can be improved, the molding material 1 can be easily prepared. In addition, since the predetermined resin does not excessively adhere to the periphery of the graphite particles and the conductivity is not hindered, the lack of conductivity can be solved. Moreover, since the local dispersion | variation of the predetermined resin and graphite of the molding material 1 can be suppressed, the surface state of the separator 20 for fuel cells deteriorates, or the mechanical characteristics and electroconductivity of the separator 20 for fuel cells are deteriorated. It is possible to solve the problem that the defect occurs locally.

  Further, if a thermoplastic resin is used as the predetermined resin of the molding material 1, it is not necessary to cure the resin, so that it is possible to improve productivity and recycle. Furthermore, since uncured components and reaction products do not remain as residues in the fuel cell separator 20, there is no possibility of the residues eluting during the operation of the fuel cell and reducing the durability of the fuel cell. it can.

  In the above embodiment, the molding material 10 is filled with the molding material 1 and is simply heated and pressurized. However, from the viewpoint of energy cost countermeasures, a heating mechanism is used during heating and pressing, or pressure cooling is performed. In this case, a cooling mechanism may be used. Specifically, the molding die 10 may be provided with a heating mechanism composed of an electric heater or a cooling mechanism composed of a cooling water flow path. Further, a flow path may be formed in the molding die 10 so that heating steam or cooling water is circulated.

  Further, when the heating steam is circulated in the molding die 10 by using the superheated steam, a high temperature can be obtained at room temperature, and good heating efficiency can be obtained. . Further, the plurality of grooves 22 of the fuel cell separator 20 may be formed in a substantially planar shape or a meandering shape. Further, each groove 22 of the fuel cell separator 20 can be appropriately formed in a cross-sectional rectangle, square, trapezoid, triangle, semicircle, or the like.

Next, examples of the present invention will be described together with comparative examples.
[Example 1]
First, 2.5 kg of homopolypropylene resin, which is a crystalline thermoplastic resin (manufactured by Prime Polymer Co., Ltd .: trade name: Prime Polypro E200GV), 38.2% by volume, 10.0 kg of artificial graphite [Orient Sangyo Co., Ltd.] Product name: AT-No. 5S, average particle size 53.3 μm] 61.8% by volume, and 3 kg of zirconia balls with φ10 mm as a stirring medium were put in each, a lid was attached, this container was attached to a tumbler mixer, and rotated at 27 ° C. for 1 hour. These homopolypropylene resins, artificial graphite, and zirconia balls were dispersed and mixed to prepare a dispersion mixture.

  When the dispersion mixture was prepared in this way, zirconia balls were taken out from the dispersion mixture to prepare a dispersion mixture of homopolypropylene resin and artificial graphite. When the melting point of the homopolypropylene resin was measured by differential scanning calorimetry, the melting point of the homopolypropylene resin was 172 ° C. Moreover, since the homopolypropylene resin is a crystalline thermoplastic resin, the melting point was set as the melting start temperature. Further, the average particle diameter of the artificial graphite was measured by a laser diffraction scattering method or a microtrack method, and the particle diameter at which the cumulative weight was 50% was defined as the average particle diameter.

  The melting start temperature by differential scanning calorimetry is obtained by accurately weighing about 10 mg of a thermoplastic resin sample and raising the temperature at a rate of temperature increase of 10 ° C./min with a differential scanning calorimeter. Asked. Here, the melting point was a temperature showing the maximum endothermic peak in the differential scanning calorimetry curve, and the glass transition point was the intersection of the base line of the differential scanning calorimetry curve and the tangent of the inflection point. As the differential scanning calorimeter, Seiko Electronics Co., Ltd. [trade name PSC220] was used.

Next, the dispersion mixture was put into a 10 L pressure kneader heated to 200 ° C. and melt-kneaded for 30 minutes. The melt-kneaded product was taken out from the pressure kneader and cooled to 50 ° C. or less, and this melt-kneaded product was punched into φ10 mm. It was put into a hammer mill equipped with metal and pulverized. When the melt-kneaded material was pulverized in this way, the pulverized melt-kneaded material was again put into a pin mill equipped with a punching metal of φ0.3 mm and pulverized. It was 85.5 micrometers when the average particle diameter of this pulverized melt-kneaded material was measured.
In addition, about the average particle diameter of the pulverized melt-kneaded material, it measured by the laser diffraction scattering method or the microtrack method, and made the particle diameter in which an accumulated weight becomes 50% into the average particle diameter.

  When the melt-kneaded product is pulverized, 3.0 kg of artificial graphite (manufactured by Orient Sangyo Co., Ltd.) so that the volume ratio of the pulverized 10.0 kg of melt-kneaded product and artificial graphite becomes 69.0% by volume in a resin container. Product name AT-No. 5S, average particle size of 53.3 μm], and 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached. Once the lid is attached, the container is attached to a tumbler mixer and rotated at 27 ° C. for 1 hour to disperse and mix these melt-kneaded material, artificial graphite and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

Next, the molding material is uniformly filled into the molding die without a groove, which is a molding die, until the side surface temperature of the molding die reaches 200 ° C. by the pair of upper and lower hot plates of the compression molding machine. The fuel cell separator was compression molded by heating and pressing. As the mold for molding, a mold in which the surface of pre-hardened steel was plated with hard chrome was used. Further, at the time of heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side temperature of the molding die reaches 200 ° C., the molding die is immediately transferred to a cooling compression molding machine having a pair of upper and lower hot plates at a temperature of 30 ° C., and the side temperature of the molding die is increased. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die by pressurization and cooling to 50 ° C. or lower.

  Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects were evaluated and summarized in Table 1. The conductivity of the fuel cell separator was evaluated by a volume resistance [mΩ · cm], and the volume resistance was measured by a four-terminal four-probe method. The volume resistance value was an average value of 10 measurement values obtained by measuring 10 measurement samples, and a low resistivity meter [manufactured by Mitsubishi Oil Chemical Co., Ltd .: trade name: Loresta AP MCP-T400] was used as the measuring instrument.

  Regarding the defects in the surface state of the fuel cell separator, the surface states of the 10 fuel cell separators were each evaluated by visual observation, and were found to be defective when a scale-like pattern or a small avatar-shaped dent was generated on the surface.

[Example 2]
First, 2.0 kg of homopolypropylene resin used in Example 1 [manufactured by Prime Polymer Co., Ltd .: trade name: Prime Polypro E200GV] 31.1% by volume, 11.0 kg of flaky graphite [Chuetsu Graphite Industries, Ltd.] Product name: HG-50A, average particle size 50 μm (catalog value)] 68.9% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and a lid was attached.

  After the lid is attached in this manner, the container is attached to a tumbler mixer and rotated under the conditions of 26 ° C. for 1 hour to disperse and mix these homopolypropylene resin, flaky graphite and zirconia balls, and the zirconia balls are taken out and homopolypropylene resin A dispersion mixture of flaky graphite was prepared.

  Next, the dispersion mixture was put into a 10 L pressure kneader heated to 200 ° C. and melt-kneaded for 30 minutes. The melt-kneaded product was taken out from the pressure kneader and cooled to 50 ° C. or less. It was put into a cutter mill equipped with metal and pulverized. When the melt-kneaded product was pulverized in this way, the pulverized melt-kneaded product was again put into a pin mill equipped with a φ0.5 mm punching metal and pulverized. The average particle size of the crushed melt-kneaded product was measured and found to be 108.7 μm.

  When the melt-kneaded product is pulverized, 0.5 kg of flaky graphite [Chuetsu Graphite Industry Co., Ltd.] is placed in a resin container so that the volume ratio of the crushed 6.5 kg of melt-kneaded product and flaky graphite is 70.7% by volume. [Product name: HG-50A, average particle size of 50 μm] and 3 kg of zirconia balls of φ10 mm were introduced and attached with lids. Once the lid is attached, the container is attached to a tumbler mixer and rotated under the conditions of 25 ° C. and 1 hour. After these melt-kneaded materials, flaky graphite and zirconia balls are dispersed and mixed, the zirconia balls are taken out and used for fuel cells. A molding material for the separator was prepared.

  Next, the molding material is uniformly filled into the molding die without a groove, which is a molding die, until the side surface temperature of the molding die reaches 200 ° C. by the pair of upper and lower hot plates of the compression molding machine. The fuel cell separator was compression molded by heating and pressing. When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.

  Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects were evaluated and summarized in Table 1. The other parts were the same as in Example 1.

Example 3
First, in a resin container, 10.0 kg of polyphenylene sulfide resin (made by Toray Industries, Inc .: trade name Torelina E2180), which is a crystalline thermoplastic resin, 52.6% by volume, 15.0 kg of artificial graphite [made by Orient Sangyo Co., Ltd .: Product name AT-No. 5S, average particle size 53.3 μm] 47.4% by volume, and 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached.

  After the lid is attached in this manner, the container is attached to a tumbler mixer and rotated at 28 ° C. for 1 hour to disperse and mix these polyphenylene sulfide resin, artificial graphite, and zirconia balls, and the zirconia balls are taken out to obtain the polyphenylene sulfide resin and the artificial resin. A dispersed mixture of graphite was prepared. When the melting point of the polyphenylene sulfide resin was measured by differential scanning calorimetry, the melting start temperature of the polyphenylene sulfide resin was 286 ° C.

  Next, the dispersion mixture was put into a kneading extruder heated to 320 ° C., melted and kneaded, cooled to 50 ° C. or lower, and this melt-kneaded product was put into a hammer mill equipped with a φ6 mm punching metal and pulverized. When the melt-kneaded material was pulverized in this way, the pulverized melt-kneaded material was again put into a pin mill equipped with a punching metal of φ0.3 mm and pulverized. The average particle diameter of the pulverized melt-kneaded product was measured and found to be 80.3 μm.

  When the melt-kneaded product is pulverized, 8.0 kg of artificial graphite (manufactured by Orient Sangyo Co., Ltd.) so that the volume ratio of the pulverized 10.0 kg of melt-kneaded product and artificial graphite is 67.7% by volume in a resin container. Product name AT-No. 5S, average particle diameter of 53.3 μm], and 3 kg of zirconia balls having a diameter of 10 mm were introduced and a lid was attached. Once the lid is attached, the container is attached to a tumbler mixer and rotated at 30 ° C. for 1 hour to disperse and mix these melt-kneaded product, artificial graphite, and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

Next, the molding material is uniformly filled in a flat plate molding die without grooves, which is a molding die uniformly applied with a mold release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010], and compression molding is performed. The fuel cell separator was compression molded by heating and pressurizing with a pair of upper and lower hot plates of the machine until the side surface temperature of the molding die reached 320 ° C. At the time of heating and pressing, the temperature of the hot plate was 360 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.
Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects were evaluated and summarized in Table 1. The other parts were the same as in Example 1.

Example 4
First, 10.0 kg of polyphenylene sulfide resin used in Example 3 (made by Toray Industries, Inc .: trade name Torelina E2180), 62.5% by volume, 10.0 kg of artificial graphite [made by Tokai Carbon Co., Ltd .: goods Name 8020S, average particle size 140 μm] 37.5% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached.

  Once the lid is attached, the container is attached to a tumbler mixer and rotated under the conditions of 30 ° C. for 1 hour to disperse and mix these polyphenylene sulfide resin, artificial graphite and zirconia balls, and the zirconia balls are taken out to obtain polyphenylene sulfide resin and artificial graphite. A dispersion mixture of was prepared.

  Next, the dispersion mixture was put into a kneading extruder heated to 320 ° C., melted and kneaded, cooled to 50 ° C. or less, and this melt-kneaded product was put into a cutter mill equipped with a φ6 mm punching metal and pulverized. When the melt-kneaded product was pulverized in this way, the pulverized melt-kneaded product was again put into a pin mill equipped with a φ0.5 mm punching metal and pulverized. The average particle size of the crushed melt-kneaded product was measured and found to be 100.5 μm.

  When the melt-kneaded product is pulverized, 7.5 kg of artificial graphite (made by Tokai Carbon Co., Ltd .: trade name) is placed in a resin container so that the volume ratio of the pulverized 5 kg of melt-kneaded product and artificial graphite is 70.6% by volume. 8020S, average particle diameter of 140 μm], and 3 kg of zirconia balls having a diameter of 10 mm were introduced and a lid was attached. Once the lid is attached, the container is attached to a tumbler mixer and rotated at 27 ° C. for 1 hour to disperse and mix these melt-kneaded material, artificial graphite and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

  Next, the molding material is uniformly filled in a flat plate molding die without grooves, which is a molding die uniformly applied with a mold release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010], and compression molding is performed. The fuel cell separator was compression molded by heating and pressurizing with a pair of upper and lower hot plates of the machine until the side surface temperature of the molding die reached 320 ° C.

When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.
Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects were evaluated and summarized in Table 1. The other parts were the same as in Example 1.

Example 5
First, 4.0 kg of cyclic olefin resin (made by JSR: trade name: Arton R5000) 51.0% by volume, 8.0 kg of artificial graphite (made by OLYTAL SANGYO Co., Ltd .: product), which is an amorphous resin, is placed in a resin container. Name AT-No. 5S, average particle size 53.3 μm] 49.0% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached.

  Once the lid is attached, the container is attached to a tumbler mixer and rotated under the conditions of 25 ° C. for 1 hour to disperse and mix these cyclic olefin resin, artificial graphite and zirconia balls, and the zirconia balls are taken out and the cyclic olefin resin and artificial graphite are removed. A dispersion mixture of was prepared. When the melting point of the cyclic olefin resin was measured by differential scanning calorimetry, the melting start temperature was 143 ° C. Moreover, since cyclic olefin resin is an amorphous resin, the glass transition point was made into melting start temperature.

  Next, the dispersion mixture was put into a 10 L pressure kneader heated to 230 ° C. and melt-kneaded for 30 minutes. The melt-kneaded product was taken out from the pressure kneader and cooled to 50 ° C. or less. It was put into a hammer mill equipped with metal and pulverized. When the melt-kneaded material was pulverized in this way, the pulverized melt-kneaded material was again put into a pin mill equipped with a punching metal of φ0.3 mm and pulverized. The average particle size of the pulverized melt-kneaded product was measured and found to be 76.3 μm.

  After the melt-kneaded product is pulverized, 13.5 kg of artificial graphite (manufactured by Olympus Industrial Co., Ltd.) so that the volume ratio of the pulverized 9.0 kg of melt-kneaded product and artificial graphite is 75.7% by volume in a resin container. Product name AT-No. 5S, average particle diameter of 53.3 μm], and 3 kg of zirconia balls having a diameter of 10 mm were introduced and a lid was attached. Once the lid is attached, the container is attached to a tumbler mixer and rotated under the conditions of 24 ° C. for 1 hour to disperse and mix these melt-kneaded material, artificial graphite, and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

Next, the molding material is uniformly filled in a flat plate molding die without grooves, which is a molding die uniformly applied with a mold release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010], and compression molding is performed. The fuel cell separator was compression molded by heating and pressurizing with a pair of upper and lower hot plates of the machine until the side surface temperature of the molding die reached 230 ° C. At the time of heating and pressing, the temperature of the hot plate was 260 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

When the side surface temperature of the molding die reaches 230 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side surface temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.
Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects were evaluated and summarized in Table 1. The other parts were the same as in Example 1.

Example 6
1 is uniformly filled with the molding material prepared in Example 1, and the side temperature of the molding die reaches 200 ° C. by a pair of upper and lower hot plates of a compression molding machine. The fuel cell separator was compression molded by heating and pressurizing. As the molding die, a die obtained by plating the surface of prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. with hard chromium was used. Further, at the time of heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die. After the fuel cell separator is manufactured in this way, the linear expansion coefficient in the surface direction of the fuel cell separator is measured, and the state of the fuel cell separator, specifically, occurrence of breakage such as cracks and cracks is visually evaluated. These are summarized in Table 2.

The coefficient of linear expansion in the surface direction of the fuel cell separator was measured and found to be 8.1 [× 10 ⁻⁶ / ° C.]. Regarding the linear expansion coefficient in the surface direction of this fuel cell separator, the fuel cell separator obtained in Example 1 was cut with a grinder to a thickness of 1 mm or less and cut into a length of 15 mm and a width of 4 mm to obtain thermal stress. Using a strain measuring device (manufactured by Seiko Electronics Co., Ltd .: trade name: MA / SS120C type), the temperature was increased from 30 ° C. to 150 ° C. at a temperature increase rate of 10 ° C./min under a nitrogen atmosphere in a tension mode. It was determined by measuring the value at ° C.

Example 7
1 is uniformly filled with the molding material prepared in Example 2, and the side temperature of the molding die reaches 200 ° C. by a pair of upper and lower hot plates of the compression molding machine. The fuel cell separator was compression molded by heating and pressurizing. As the molding die, a die obtained by plating the surface of prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. with hard chromium was used. Further, at the time of heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die. When the fuel cell separator was manufactured in this way, the linear expansion coefficient in the surface direction of the fuel cell separator was measured, and the occurrence of breakage such as cracks or cracks was visually evaluated, and these are summarized in Table 2.

The coefficient of linear expansion in the surface direction of the fuel cell separator was measured and found to be 6.5 [× 10 ⁻⁶ / ° C.]. Regarding the linear expansion coefficient in the surface direction of this fuel cell separator, the fuel cell separator obtained in Example 2 was cut with a grinder so as to have a thickness of 1 mm or less, and a thermal stress strain measuring apparatus [manufactured by Seiko Electronics Co., Ltd .: Product name MA / SS120C type], in a nitrogen atmosphere, in a tension mode, the temperature was raised from 30 ° C. to 150 ° C. at a heating rate of 10 ° C./min, and the value at 30 ° C. to 100 ° C. was measured. Asked.

Example 8
1 is uniformly filled with the molding material prepared in Example 3, and the side temperature of the molding die reaches 320 ° C. by a pair of upper and lower hot plates of a compression molding machine. The fuel cell separator was compression molded by heating and pressurizing. The mold for molding uses a mold in which the surface of a prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. is plated with hard chromium, and a mold release agent [manufactured by Daikin Industries, Ltd .: commodity Name Die Free GA-6010] was uniformly applied. Further, at the time of heating and pressing, the temperature of the hot plate was 360 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die.

When the fuel cell separator was manufactured in this way, the linear expansion coefficient in the surface direction of the fuel cell separator was measured, and the occurrence of breakage such as cracks or cracks was visually evaluated, and these are summarized in Table 2. When the linear expansion coefficient in the surface direction of the fuel cell separator obtained in Example 3 was measured, it was 12.2 [× 10 ⁻⁶ / ° C.]. Others were the same as in Example 6.

Example 9
1 is uniformly filled with the molding material prepared in Example 4, and the side temperature of the molding die reaches 320 ° C. by a pair of upper and lower hot plates of a compression molding machine. The fuel cell separator was compression molded by heating and pressurizing. The mold for molding uses a mold in which the surface of a prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. is plated with hard chromium, and a mold release agent [manufactured by Daikin Industries, Ltd .: commodity Name Die Free GA-6010] was uniformly applied. Further, at the time of heating and pressing, the temperature of the hot plate was 360 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die.

When the fuel cell separator was manufactured in this way, the linear expansion coefficient in the surface direction of the fuel cell separator was measured, and the occurrence of breakage such as cracks or cracks was visually evaluated, and these are summarized in Table 2. When the linear expansion coefficient in the surface direction of the fuel cell separator obtained in Example 4 was measured, it was 9.8 [× 10 ⁻⁶ / ° C.]. Others were the same as in Example 6.

Example 10
1 is filled uniformly with the molding material prepared in Example 5, and the side surface temperature of the molding die reaches 230 ° C. by a pair of upper and lower hot plates of a compression molding machine. The fuel cell separator was compression molded by heating and pressurizing. As the molding die, a die obtained by plating the surface of prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. with hard chrome is used, and a mold release agent [manufactured by Daikin Industries, Ltd .: Product name Die Free GA-6010] was uniformly applied. Further, at the time of heating and pressing, the temperature of the hot plate was 260 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 230 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side surface temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die.

When the fuel cell separator was manufactured in this way, the linear expansion coefficient in the surface direction of the fuel cell separator was measured, and the occurrence of breakage such as cracks or cracks was visually evaluated, and these are summarized in Table 2. The linear expansion coefficient in the surface direction of the fuel cell separator obtained in Example 5 was measured and found to be 6.2 [× 10 ⁻⁶ / ° C.]. Others were the same as in Example 6.

[Comparative Example 1]
First, the homopolypropylene resin [manufactured by Prime Polymer Co., Ltd .: trade name: Prime Polypro E200GV] used in Example 1 was pulverized by a solution pulverization method, and then classified by a 150 mesh sieve, and a preforming material was not prepared.

  Next, 2.0 kg of homopolypropylene resin that passed through the sieve was 29.2% by volume, 12.0 kg of artificial graphite [trade name AT-No. 5S, average particle size 53.3 μm] 70.8% by volume, 3 kg of zirconia balls having a diameter of 10 mm as a stirring medium were put into a resin container and a lid was attached, and this container was attached to a tumbler mixer at 30 ° C. for 1 hour. The homopolypropylene resin, artificial graphite, and zirconia balls were dispersed and mixed, and the zirconia balls were taken out to prepare a molding material for a fuel cell separator.

Next, the molding material is uniformly filled into the molding die without a groove, which is a molding die, until the side surface temperature of the molding die reaches 200 ° C. by the pair of upper and lower hot plates of the compression molding machine. The fuel cell separator was compression molded by heating and pressing. As the mold for molding, a mold in which the surface of pre-hardened steel was plated with hard chrome was used. Further, at the time of heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die. Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects, were evaluated and summarized in Table 3, as in the Examples.

[Comparative Example 2]
First, 5.5 kg of homopolypropylene resin used in Example 1 (manufactured by Prime Polymer Co., Ltd .: trade name Prime Polypro E200GV) 71.2% by volume, 5.5 kg of artificial graphite [manufactured by Orient Sangyo Co., Ltd.] : Product name AT-No. 5S, average particle size 53.3 μm] 28.8% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and a lid was attached.

  After the lid is attached in this manner, the container is mounted on a tumbler mixer and rotated under the conditions of 28 ° C. for 1 hour to disperse and mix these homopolypropylene resin, artificial graphite and zirconia balls, and the zirconia balls are taken out and homopolypropylene resin and artificial A dispersed mixture of graphite was prepared.

  Next, the dispersion mixture was put into a 10 L pressure kneader heated to 200 ° C. and melt-kneaded for 30 minutes. The melt-kneaded product was taken out from the pressure kneader and cooled to 50 ° C. or less, and this melt-kneaded product was punched into φ10 mm. It was put into a hammer mill equipped with metal and pulverized. When the melt-kneaded product was pulverized in this way, the pulverized melt-kneaded product was again put into a pin mill equipped with a φ0.5 mm punching metal and pulverized. The average particle diameter of the crushed melt-kneaded product was measured and found to be 109.7 μm.

  When the melt-kneaded product is pulverized, 22.5 kg of artificial graphite (made by Orient Sangyo Co., Ltd .: trade name) so that the volume ratio of the crushed 10 kg of melt-kneaded product and artificial graphite is 69.0% by volume in a resin container. Product name AT-No. 5S, average particle diameter of 53.3 μm], and 3 kg of zirconia balls having a diameter of 10 mm were introduced and a lid was attached. Once the lid is attached, the container is attached to a tumbler mixer and rotated at 27 ° C. for 1 hour to disperse and mix these melt-kneaded product, artificial graphite and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

  Next, the molding material is uniformly filled into the molding die without a groove, which is a molding die, until the side surface temperature of the molding die reaches 200 ° C. by the pair of upper and lower hot plates of the compression molding machine. The fuel cell separator was compression molded by heating and pressing. When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.

  Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects, were evaluated and summarized in Table 3, as in the Examples.

[Comparative Example 3]
First, 5 kg of polyphenylene sulfide resin used in Example 2 (made by Toray Industries, Inc .: trade name Torelina E2180) 32.3% by volume, 17.5 kg of artificial graphite [made by Tokai Carbon Co., Ltd .: trade name 8020S] , Average particle size 140 μm] 67.7% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached.

  After the lid is attached, the container is mounted on a tumbler mixer and rotated at 28 ° C. for 1 hour, and these polyphenylene sulfide resin, artificial graphite and zirconia balls are dispersed and mixed, and the zirconia balls are taken out to obtain polyphenylene sulfide resin and artificial graphite A dispersion mixture of was prepared.

  Next, the dispersion mixture was charged into a kneading extruder heated to 320 ° C., melted and kneaded, cooled to 50 ° C. or lower, and the molten kneaded material was charged into a cutter mill equipped with a φ6 mm punching metal and pulverized. When the melt-kneaded material was pulverized in this way, the pulverized melt-kneaded material was again put into a pin mill equipped with a punching metal of φ0.3 mm and pulverized to prepare a molding material for a fuel cell separator. The average particle diameter of the molding material was measured and found to be 79.6 μm.

  Next, the molding material is uniformly filled in a flat plate molding die without grooves, which is a molding die uniformly applied with a mold release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010], and compression molding is performed. The fuel cell separator was compression molded by heating and pressurizing with a pair of upper and lower hot plates of the machine until the side surface temperature of the molding die reached 320 ° C.

When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die.
Once the fuel cell separator was manufactured, the characteristics of the fuel cell separator, that is, conductivity and surface state defects, were evaluated and summarized in Table 3, as in the Examples. The other parts were the same as those in Comparative Example 1.

[Comparative Example 4]
First, 12 kg of the homopolypropylene resin used in Example 1 (manufactured by Prime Polymer Co., Ltd .: trade name: Prime Polypro E200GV), 83.2% by volume, 6 kg of artificial graphite (manufactured by Orient Sangyo Co., Ltd .: trade name: AT) -No. 5S, average particle size 53.3 μm] 16.8% by volume, 3 kg of zirconia balls having a diameter of 10 mm were added as stirring media, and lids were attached.

  Once the lid is attached, the container is attached to a tumbler mixer and rotated under the conditions of 27 ° C. for 1 hour to disperse and mix these homopolypropylene resin, artificial graphite and zirconia balls. The zirconia balls are taken out and homopolypropylene resin and artificial graphite are removed. A dispersion mixture of was prepared.

  Next, the dispersion mixture is put into a 10 L pressure kneader heated to 200 ° C. and melt-kneaded for 30 minutes. The melt-kneaded product is taken out from the pressure kneader and cooled to 50 ° C. or lower. By grinding. The average particle diameter of the crushed melt-kneaded product was measured and found to be 83 μm.

  When the melt-kneaded product is pulverized, 12 kg of artificial graphite (made by Orient Sangyo Co., Ltd .: trade name, product name) so that the volume ratio of the crushed 12 kg of melt-kneaded product and artificial graphite is 44.7% by volume in a resin container. AT-No. 5S, average particle diameter of 53.3 μm], and 3 kg of zirconia balls having a diameter of 10 mm were introduced and a lid was attached. Once the lid is attached, the container is mounted on a tumbler mixer and rotated under the conditions of 28 ° C. for 1 hour to disperse and mix these melt-kneaded material, artificial graphite and zirconia balls, and then the zirconia balls are taken out to separate the fuel cell separator. A molding material was prepared.

Next, the molding material is uniformly filled in the grooved molding die, and is heated and pressurized by a pair of upper and lower hot plates of the compression molding machine until the side surface temperature of the molding die reaches 200 ° C. The separator was compression molded. As the molding die, a die obtained by plating the surface of prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. with hard chromium was used. At the time of heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die. When the fuel cell separator was manufactured in this manner, the occurrence of breakage such as cracks or cracks of the fuel cell separator was visually evaluated.

Further, in order to measure the linear expansion coefficient in the surface direction of the separator for the fuel cell, the molding die without grooves is uniformly filled, and the side temperature of the molding die is set by a pair of upper and lower hot plates of a compression molding machine. Was heated and pressurized until the temperature reached 200 ° C. In this heating and pressing, the temperature of the hot plate was 250 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

When the side surface temperature of the molding die reaches 200 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine having a temperature of 30 ° C., and the side temperature of the molding die becomes 50 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die. The removed fuel cell separator was cut with a grinder to a thickness of 1 mm or less, and then measured in the same manner as in Example 6 to obtain the linear expansion coefficient. The linear expansion coefficient in the surface direction of this fuel cell separator was 19.4 [× 10 ⁻⁶ / ° C.].

[Comparative Example 5]
First, 1.0 kg of polyphenylene sulfide resin used in Example 3 (product name: Torelina E2180), 17.2% by volume, 8.0 kg of artificial graphite (product manufactured by Orient Sangyo Co., Ltd .: product) used in a resin container. Name AT-No. 5S, average particle diameter 53.3 μm] 82.3 vol%, and 3 kg of zirconia balls having a diameter of 10 mm as a stirring medium were put in each case and a lid was attached.

  After the lid is attached in this manner, the container is attached to a tumbler mixer and rotated at 29 ° C. for 1 hour to disperse and mix these polyphenylene sulfide resin, artificial graphite and zirconia balls. A dispersed mixture of graphite was prepared.

  Next, the dispersion mixture was put into a kneading extruder heated to 320 ° C. and melt-kneaded, and then the melt-kneaded product was taken out and cooled to 50 ° C. or less. The melt-kneaded product was placed in a hammer mill equipped with a φ10 mm punching metal. Added and crushed. When the melt-kneaded material was pulverized in this way, the pulverized melt-kneaded material was again put into a pin mill equipped with a punching metal of φ0.3 mm and pulverized. The average particle size of the pulverized melt-kneaded product was measured and found to be 94.3 μm.

Next, the molding material is uniformly filled in the grooved molding die, and is heated and pressurized by a pair of upper and lower hot plates of the compression molding machine until the side surface temperature of the molding die reaches 320 ° C. The separator was compression molded. As the molding die, a die obtained by plating the surface of prehardened steel having a linear expansion coefficient of 12.5 × 10 ⁻⁶ / ° C. with hard chromium was used. Further, the molding material was filled after uniformly applying a release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010] to the surface of the molding die. Further, at the time of heating and pressing, the temperature of the hot plate was 360 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

  When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 148 mm × 210 mm × 1 mm was removed from the molding die. When the fuel cell separator was manufactured in this manner, the occurrence of breakage such as cracks or cracks of the fuel cell separator was visually evaluated.

In addition, in order to measure the linear expansion coefficient in the surface direction of the separator for a fuel cell, it is filled in a molding die without a groove uniformly coated with a release agent [manufactured by Daikin Industries, Ltd .: trade name: Die Free GA-6010]. The pair of hot plates of the compression molding machine was heated and pressurized until the side surface temperature of the molding die reached 320 ° C. In this heating and pressing, the temperature of the hot plate was 360 ° C., and the molding pressure was 800 kg / cm ² with respect to the area of the fuel cell separator.

When the side surface temperature of the molding die reaches 320 ° C., the temperature of the pair of upper and lower hot plates is immediately transferred to a cooling compression molding machine whose temperature is 30 ° C., and the side temperature of the molding die becomes 80 ° C. or less. The fuel cell separator having an outer shape of 210 mm × 297 mm × 3 mm was removed from the molding die. The removed fuel cell separator was cut with a grinder to a thickness of 1 mm or less, and then measured in the same manner as in Example 6 to obtain the linear expansion coefficient. The linear expansion coefficient in the surface direction of this fuel cell separator was 3.3 [× 10 ⁻⁶ / ° C.].

[Result]
In the case of Examples 1 to 5, the fuel cell separator has a volume resistance of 10 mΩ · cm or less and has sufficient conductivity, and the surface of the fuel cell separator has a scale-like pattern or avatar. No small dents or the like were observed, and a very good fuel cell separator could be obtained. Moreover, in Examples 6 to 10, no breakage such as cracks or cracks was observed in the fuel cell separator, and a high-quality fuel cell separator could be obtained.

  On the other hand, in the case of Comparative Examples 1 and 2, the conductivity of the fuel cell separator was sufficient, but the surface of the fuel cell separator had a scale-like pattern or a small avatar-like dent. A molding defect occurred in the battery separator. Further, in the case of Comparative Example 3, the volume resistance value of the fuel cell separator significantly exceeded 10 mΩ · cm, causing a problem in the conductivity of the fuel cell separator. Furthermore, in Comparative Examples 4 and 5, cracks were observed in the fuel cell separator, and molding defects occurred in the fuel cell separator.

DESCRIPTION OF SYMBOLS 1 Molding material 10 Molding die 11 Upper mold 12 Molding part 13 Lower mold 20 Fuel cell separator 21 Base plate 22 Groove

Claims (4)

A method for producing a fuel cell separator by filling a molding die with a powdery molding material, heating and pressurizing, and then pressurizing and cooling to obtain a fuel cell separator,
A predetermined resin and graphite particles are heated and kneaded at a temperature equal to or higher than the melting start temperature of the predetermined resin to prepare a preformed material, the preformed material is pulverized and powdered, and the powdered preformed material A method for producing a separator for a fuel cell, comprising preparing a powdery molding material by adding graphite particles to a mixture and mixing at a temperature lower than a melting start temperature of a predetermined resin.   2. The method for producing a fuel cell separator according to claim 1, wherein the linear expansion coefficient in the surface direction of the fuel cell separator is in the range of -60 to + 20% or less of the linear expansion coefficient of the molding die.   The addition amount of graphite particles in the preforming material is the addition amount of graphite particles in the molding material × 0.5 or more and the addition amount of graphite particles in the molding material × less than 1.0, and the average particle size of the graphite particles The manufacturing method of the separator for fuel cells of Claim 1 or 2 which is 5-500 micrometers.   A fuel cell separator manufactured by the method for manufacturing a fuel cell separator according to claim 1, 2 or 3.

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