JP2014154475A - Fuel cell separator and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell separator in which the discharge of water from a groove is effectively promoted, so that power generation efficiency of a fuel cell can be stabilized.SOLUTION: A fuel cell separator 20 contains graphite particles and a cured product comprising a thermosetting resin component. In the fuel cell separator 20, a groove 2 for gas circulation is formed. An inner side face of the groove 2 is formed to have an arithmetic average height Sa defined by ISO 25178-2:2012 of 0.5-1.6 μm.

Description

  The present invention relates to a fuel cell separator applied to a fuel cell and a method for manufacturing the same.

  In general, a fuel cell is composed of a cell stack in which several tens to several hundreds of single cells are stacked in series, whereby the fuel cell can generate an electromotive force. Fuel cells are classified into several types according to the type of electrolyte. In recent years, a polymer electrolyte fuel cell provided with a polymer electrolyte membrane has attracted attention as a high-power fuel cell.

  A single cell of a polymer electrolyte fuel cell is configured, for example, by stacking a fuel cell separator, a gasket, and a membrane-electrode composite (see FIG. 2). In the separator, a manifold is formed in an outer peripheral portion surrounding a region where a gas flow groove is formed. Further, if necessary, a gasket for sealing is laminated on the outer peripheral portion of the separator.

  Among the components constituting such a fuel cell, the separator has a unique shape in which a gas circulation groove and a manifold are formed. The separator has a function of separating the fuel, oxidant, and cooling water flowing in the fuel cell so as not to mix, and transmits the electric energy generated by the fuel cell to the outside, and the heat generated by the fuel cell to the outside. It plays an important role of heat dissipation.

  The separator is formed from a molding material containing, for example, graphite particles and a resin component. In this case, for example, a separator is obtained by molding a molding material in a mold.

  Such a separator may be subjected to a blasting treatment for removing the skin layer and adjusting the surface roughness, a hydrophilization treatment for improving hydrophilicity, and the like. In particular, it is known that water generated by a reaction has a great influence on battery characteristics during power generation by a fuel cell. One of the most important characteristics required of a separator is that this water can be discharged quickly. For that purpose, hydrophilicity of the separator is required.

  For example, in Patent Document 1, a molding composition containing an epoxy resin, a phenolic compound, and graphite particles is molded, and the surface of the separator obtained thereby is subjected to wet blasting and remote atmospheric pressure. It is disclosed that plasma treatment is sequentially performed, and subsequently, a gasket is laminated on the surface of the separator, and further, a remote atmospheric pressure plasma treatment is performed again on the separator surface to obtain a separator with a gasket. .

  However, with the demand for miniaturization of fuel cells, miniaturization of separators and miniaturization of grooves formed in the separators are also progressing. Accordingly, it becomes difficult for water to be discharged from the groove. For this reason, even if a groove | channel is refined | miniaturized, it is calculated | required that water is rapidly discharged | emitted from this groove | channel.

JP 2011-150858 A

  The present invention has been made in view of the above reasons, and by effectively promoting the discharge of water from the groove, the fuel cell separator capable of stabilizing the power generation efficiency of the fuel cell, and such a fuel It is an object to provide a method for producing a battery separator.

  A fuel cell separator according to a first aspect of the present invention is a fuel cell separator that includes a cured product of a thermosetting resin component and graphite particles, and is formed with a groove for gas circulation. The arithmetic average height Sa defined by ISO 25178-2: 2012 on the inner surface is 0.5 to 1.6 μm.

  In the fuel cell separator according to the second aspect of the present invention, in the first aspect, the inner surface of the groove is subjected to a hydrophilic treatment.

According to a third aspect of the present invention, there is provided a method for producing a fuel cell separator comprising: molding a molding material containing graphite particles and a thermosetting resin component; The arithmetic average height defined by ISO 25178-2: 2012 on the inner surface of the groove by performing a wet blasting process in which a liquid mixture containing an abrasive material is sprayed onto the inner surface of the groove. And adjusting Sa to 0.5 to 1.6 μm.

  In the method of manufacturing a fuel cell separator according to the fourth aspect of the present invention, in the third aspect, the liquid mixture is directed toward the surface of the molded body where the groove is formed in the wet blasting process. The mixed liquid is sprayed onto the inner surface of the groove by spraying in a direction inclined by 10 ° to 30 ° with respect to the normal of this surface.

  The method for manufacturing a fuel cell separator according to the fifth aspect of the present invention further includes the step of subjecting the inner surface of the groove to a hydrophilic treatment in the third or fourth aspect.

  According to the fuel cell separator of the present invention, the hydrophilicity of the inner surface of the gas flow groove in the fuel cell separator is improved, and water droplets are less likely to collect in the groove, so that water is effectively discharged from the groove. To be promoted. Thereby, stability of a fuel cell provided with a fuel cell separator improves.

  Further, in the method for producing a fuel cell separator according to the present invention, the hydrophilicity of the inner surface of the gas flow groove in the fuel cell separator can be easily improved. Can effectively promote the discharge of water. Thereby, stability of a fuel cell provided with the fuel cell separator manufactured by the present invention is improved.

It is a schematic sectional drawing which shows the wet blast process in one Embodiment of this invention. It is a disassembled perspective view which shows the unit cell of the fuel cell in one Embodiment of this invention. It is a perspective view which shows the fuel cell in one Embodiment of this invention. FIG. 3A and FIG. 3B are perspective views showing a separator with a gasket according to an embodiment of the present invention.

  Embodiments of the invention will be described below.

  FIG. 2 schematically shows the structure of a unit cell of a fuel cell separator (hereinafter referred to as a separator) 20 and a polymer electrolyte fuel cell including the separator 20 in the present embodiment. The unit cell is configured by stacking the separator 20, the gasket 12, and the membrane-electrode assembly 5. The membrane-electrode assembly 5 includes an oxidant electrode 31, a fuel electrode 32, and an electrolyte 4.

  The separator 20 is formed with a groove 2 for gas distribution. The separator 20 may further be formed with a groove 7 for circulating cooling water. In the present embodiment, one unit cell includes a cathode-side separator 21 and an anode-side separator 22 as the separator 20. Each of the cathode side separator 21 and the anode side separator 22 has a first surface in the thickness direction and a second surface on the opposite side of the first surface.

  In the unit cell, the first surface of the cathode separator 21 overlaps with the oxidant electrode 31, and the first surface of the anode separator 22 overlaps with the fuel electrode 32.

  On the first surface of the anode separator 22, a groove 2 (202) for flowing fuel gas is formed as a gas flow groove 2. The anode-side separator 22 has a region where a groove 202 for allowing the fuel gas to flow is formed and an outer peripheral portion surrounding this region.

  The cathode-side separator 21 is provided with a groove for flowing an oxidant gas as a gas flow groove 2 (not shown) on the second surface thereof. The cathode-side separator 21 has a region where a groove for allowing the oxidant gas to flow therethrough and an outer peripheral portion surrounding this region. Further, a groove 7 for circulating cooling water is formed on the second surface of the cathode side separator 21.

  When two unit cells are overlapped, the second surface of the cathode-side separator 21 in one unit cell and the second surface of the anode-side separator 22 in the other unit cell are overlapped. Between the cathode side separator 21 and the anode side separator 22, a flow path composed of the grooves 7 is formed. This channel is a channel for circulating cooling water.

  In addition, the groove | channel for distribute | circulating a cooling water may be formed in the 2nd surface of the anode side separator 22. FIG. Further, a groove for circulating cooling water is formed on the second surface of the cathode-side separator 21, and a groove for circulating cooling water is also formed on the second surface of the anode-side separator 22. Good.

  Each separator 20 is formed with a manifold 13 having holes penetrating the separator 20. In the present embodiment, six manifolds 13 are formed in each separator 20. These manifolds 13 are opened at the outer peripheral portions of the first surface and the second surface of each separator 20. The six manifolds 13 include two fuel manifolds 131, two oxidant manifolds 132, and two cooling manifolds 133. The two oxidant through holes 131 and 131 in the cathode separator 21 communicate with a groove in the first surface of the cathode separator 21. The two fuel through holes 132 and 132 in the anode side separator 22 communicate with the groove 202 in the first surface of the anode side separator 22. Further, the two cooling manifolds 133 in the cathode side separator 21 communicate with the groove 7 in the second surface of the cathode side separator 21.

  In the present embodiment, as shown in FIG. 2, the gas flow groove 2 in the separator 20 is a straight type. Generally, as a groove in the separator, there are a serpentine type groove having a bend and a straight type groove having no bend. Of course, the gas distribution groove 2 in the separator 20 shown in FIG. 2 may be a serpentine type.

The thickness of the separator 20 is formed in the range of 0.5-3.0 mm, for example. The width of the gas flow groove 2 of the separator 20 is formed in a range of 0.5 to 1.5 mm, for example, and a depth of 0.5 to 1.5 mm, for example. The ratio (A / B) of the width (A) to the depth (B) of the groove 2 is preferably 1 or more. In this case, the efficiency of the hydrophilization process mentioned later becomes high. Moreover, the opening area of the manifold 13 is, for example, in the range of 0.5 to 5.0 cm ² .

  The gasket 12 is overlaid on the outer peripheral portion of each of the first surface of the cathode side separator 21 and the first surface of the anode side separator 22. Thereby, the gas leak of fuel gas and oxidant gas is suppressed.

  Further, when two unit cells are overlapped, the gasket 12 is also provided between the second surface of the cathode separator 21 in one unit cell and the second surface of the anode separator 22 in the other unit cell. Intervenes. This gasket 12 suppresses leakage of cooling water.

  The second surface of the cathode side separator 21 and the second surface of the anode side separator 22 may be bonded with an adhesive such as an olefin resin adhesive. In this case, the leakage of the cooling water is suppressed even if no gasket is interposed between the second surface of the cathode side separator 21 and the second surface of the anode side separator 22.

  In this unit cell structure, the oxidant through-hole 131 in the separator 20 constitutes an oxidant flow path for supplying and discharging the oxidant to the oxidant electrode. Further, the fuel through-hole 132 constitutes a fuel flow path for supplying and discharging fuel to the fuel electrode. The cooling through-hole 133 constitutes a cooling channel through which cooling water or the like flows.

  The oxidant electrode 31, the fuel electrode 32, and the electrolyte 4 are formed of a known material corresponding to the type of fuel cell. In the case of a polymer electrolyte fuel cell, the oxidant electrode 31 and the fuel electrode 32 are configured by supporting a catalyst on a substrate such as carbon cloth, carbon paper, or carbon felt. Examples of the catalyst in the oxidant electrode 31 include a platinum catalyst, a platinum / ruthenium catalyst, and a cobalt catalyst. Examples of the catalyst in the fuel electrode 32 include a platinum catalyst and a silver catalyst. In the case of a solid polymer fuel cell, the electrolyte 4 is formed of, for example, a proton conductive polymer membrane. In particular, in the case of a methanol direct fuel cell, for example, the proton conductivity is high, and the electronic conductivity and methanol permeability are high. It is formed from a fluorine resin or the like that is hardly shown.

  FIG. 3 shows an example of a fuel cell 40 (cell stack) composed of a plurality of unit cells including the separator 20 and the membrane-electrode assembly 5. This fuel cell 40 includes an oxidant supply port 171 and a discharge port 172 that communicate with the oxidant through hole 131 of the separator 20, and a fuel supply port 181 and a discharge port 182 that communicate with the fuel through hole 132 of the separator 20. And a cooling water supply port 191 and a discharge port 192 communicating with the cooling through hole 133 of the separator 20.

  In the present embodiment, the separator contains a cured product of a thermosetting resin component and graphite particles. As described above, the gas channel is formed in the separator. Furthermore, arithmetic mean height Sa prescribed | regulated by ISO 25178-2: 2012 of the inner surface of this groove | channel is 0.5-1.5 micrometers. In the case where the separator contains a cured product of a thermosetting resin component and graphite particles, if the inner surface of the groove for gas flow has the rough surface shape as described above, The hydrophilicity of the side is very high. For this reason, even if water adheres in the groove for gas circulation, the water tends to spread over a wide range in the groove, thereby making it difficult for water droplets to collect in the groove for gas circulation. Emissions are effectively promoted.

  In this separator, when 1 μL of ion exchange water is dropped into the groove for gas circulation, the spreading length of the ion exchange water along the longitudinal direction of the groove is preferably 10 mm or more, and can be 20 mm or more. More preferably, it is more preferably 35 mm or more. By adjusting the roughness of the inner surface of the gas flow groove as described above, the separator can acquire such high hydrophilicity. Thereby, discharge of water from the groove for gas distribution is further effectively promoted.

  It is also preferable that a hydrophilic treatment is performed on the inner surface of the groove for gas flow. In this case, the hydrophilicity of the inner surface of the groove for gas circulation is combined by adjusting the roughness of the inner surface of the groove for gas circulation as described above and the treatment for hydrophilicity. The nature becomes even higher. Thereby, discharge of water from the groove for gas distribution is further effectively promoted.

  In the present embodiment, the separator manufacturing method forms a molding material containing graphite particles and a thermosetting resin component, thereby producing a molded body in which grooves for gas circulation are formed, and polishing. Arithmetic average height defined by ISO 25178-2: 2012 on the inner surface of the gas flow groove by performing a wet blasting process for injecting the mixed liquid containing the material onto the inner surface of the gas flow groove Adjusting Sa to 0.5-1.6 μm. For this reason, the roughness of the inner surface of the groove for gas circulation can be easily adjusted by performing wet blasting on the inner surface of the groove for gas circulation. In the separator manufactured in this way, the hydrophilicity of the inner surface of the gas distribution groove is very high. The molding material is, for example, a solid content ratio of 70 to 80% by mass of graphite particles, 20 to 30% by mass of a thermosetting resin component, and 0.1 to 0.5% by mass of an aliphatic internal mold release agent. Can be contained.

  During the wet blasting process, the nozzle directs the mixed liquid toward the gas flow groove in the molded body and injects the mixed liquid in an oblique direction with respect to this surface. It is preferable to spray on the inner surface of the groove. In this case, the mixed liquid can easily reach the inner surface of the gas flow groove, and therefore, the roughness of the inner surface of the gas flow groove that is difficult to process can be more easily adjusted.

  It is also preferable that the method for manufacturing the separator further includes a step of subjecting the inner surface of the gas circulation groove to a hydrophilic treatment. In this case, the hydrophilicity can also improve the hydrophilicity of the inner surface of the gas flow groove, and therefore, the discharge of water from the gas flow groove is further effectively promoted.

  More specific embodiments of the separator and the manufacturing method thereof will be described.

  In this embodiment, the molding material used for manufacturing the separator contains graphite and a thermosetting resin component.

  Graphite particles are used to improve the conductivity of the separator by reducing the electrical specific resistance of the separator. The ratio of the graphite particles in the molding material is preferably in the range of 70 to 90% by mass with respect to the total solid content in the molding material. When the ratio of the graphite particles is 70% by mass or more, the separator is provided with sufficiently excellent conductivity. When the ratio is 90% by mass or less, the molding material has sufficiently excellent moldability. As well as being imparted, the separator is provided with sufficiently excellent gas permeability. The ratio of the graphite particles is more preferably in the range of 70% by mass to 80% by mass.

  The graphite particles may be any of artificial graphite powder and natural graphite powder. Natural graphite powder has the advantage of high conductivity, and artificial graphite powder has the advantage of low anisotropy, although the conductivity is somewhat inferior to that of natural graphite powder. For example, as graphite particles, graphite particles obtained by graphitizing carbonaceous materials such as mesocarbon microbeads, graphite particles obtained by graphitizing coal-based coke and petroleum-based coke, processed powder of graphite electrodes and special carbon materials, natural graphite One or more selected from quiche graphite, expanded graphite and the like are used.

  The graphite particles are preferably purified. In this case, since the contents of ash and ionic impurities in the graphite particles are reduced, the elution of impurities from the separator is suppressed.

  The average particle size of the graphite particles is preferably in the range of 10 to 100 μm. When the average particle size is 10 μm or more, the moldability of the molding material becomes excellent. If the average particle size is 30 μm or more, better results can be obtained. Moreover, if this average particle diameter is 100 micrometers or less, the surface smoothness of a separator will further improve. If this average particle size is 70 μm or less, better results can be obtained.

  The average particle diameter of the graphite particles is a volume average particle diameter measured by a laser diffraction scattering method with a laser diffraction / scattering particle size analyzer (such as Microtrac MT3000II series manufactured by Nikkiso Co., Ltd.).

  Thermosetting resin components include, for example, epoxy resins, thermosetting phenol resins, vinyl ester resins, polyimide resins, unsaturated polyester resins, diallyl phthalate resins, polyester resins, urea resins, melamine resins, silicone resins, vinyl ester resins, and At least one kind of thermosetting resin selected from benzoxazine resins can be contained. Among these, it is preferable to use at least one kind of thermosetting resin selected from benzoxazine resin, epoxy resin, and thermosetting phenol resin. In this case, the heat resistance and mechanical strength of the separator are particularly high.

  When an epoxy resin is used, the epoxy resin preferably contains at least one selected from ortho-cresol novolac type epoxy resin, bisphenol type epoxy resin, biphenyl type epoxy resin, and phenol aralkyl type epoxy resin having a biphenylene skeleton. . These resins are excellent in that they have a good melt viscosity and a small amount of impurities, in particular, a small amount of ionic impurities.

  When an epoxy resin is used, the thermosetting resin component further contains an epoxy resin curing agent. Although it will not specifically limit if a hardening | curing agent has the capability to harden an epoxy resin, It is preferable to make a phenolic compound an essential component. This phenolic compound contains at least one selected from various polyphenol resins such as phenol novolac resin, cresol novolac resin, phenol aralkyl resin, naphthol aralkyl resin, and the like. When a phenolic compound is used, it is preferable that the equivalent of the epoxy resin with respect to 1 equivalent of a phenolic compound is the range of 0.8-1.2.

  When a thermosetting phenol resin is used as the thermosetting resin, it is particularly preferable to use a phenol resin that undergoes a polymerization reaction by ring-opening polymerization. An example of such a phenolic resin is a benzoxazine resin. In this case, since gas due to dehydration is not generated in the molding process, voids are hardly generated in the molded product, and a decrease in gas permeability of the separator is suppressed. It is also preferable to use a resol type phenol resin. For example, as a result of 13C-NMR analysis, ortho-ortho bond ratio 25 to 35%, ortho-para bond ratio 60 to 70%, para-para bond ratio 5 to 10%. It is preferable to use a resol type phenolic resin having a structure of The resol resin is usually in a liquid state, but the resol type phenol resin can easily adjust the softening point, and a resol type phenol resin having a melting point of 70 to 90 ° C. can be easily obtained. Thereby, the change of a molding material decreases and the handleability at the time of shaping | molding improves. When the melting point is less than 70 ° C., the components are likely to aggregate in the molding material, and the handleability may be reduced.

  The thermosetting resin component may contain a catalyst (curing accelerator) as necessary. Examples of the catalyst include organic phosphines such as triphenylphosphine, tertiary amines such as 1,8-diazabicyclo (5,4,0) undecene-7, and imidazoles such as 2-methylimidazole. The content of the catalyst in the molding material is preferably in the range of 0.5 to 3% by mass with respect to the total amount of the thermosetting resin and the curing agent in the molding material.

  As a catalyst, the weight loss when heated under the conditions of a measurement start temperature of 30 ° C., a heating rate of 10 ° C./min, a holding temperature of 120 ° C., and a holding time of 30 minutes at a holding temperature of 5% or less is second, Substituted imidazoles having hydrocarbon groups may be used. As this substituted imidazole, a substituted imidazole having 6 to 17 carbon atoms in the 2-position hydrocarbon group is particularly preferable. Specific examples of this substituted imidazole include 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-phenylimidazole and the like.

  The molding material may further contain an internal mold release agent. As the internal mold release agent, an appropriate one is used, and in particular, the internal mold release agent is capable of phase separation without being compatible with the thermosetting resin and the hardener in the molding material at 120 to 190 ° C. It is preferable to have. As such an internal release agent, it is preferable to use at least one selected from polyethylene wax, carnauba wax, and long-chain fatty acid wax. Such an internal mold release agent is phase-separated from the thermosetting resin and the hardener in the molding process of the molding material, so that the mold release improving effect is satisfactorily exhibited.

  The amount of the internal mold release agent used is appropriately set in consideration of the complexity of the separator shape, the groove depth, the ease of releasability from the mold surface such as the draft angle, and the like. In particular, the ratio of the internal mold release agent to the total amount of the molding material is preferably in the range of 0.1 to 2.5% by mass. When this ratio is 0.1% by mass or more, sufficient release properties are exhibited at the time of molding the mold, and when this ratio is 2.5% by mass or less, the hydrophilic property on the surface of the separator is inhibited by the internal mold release agent. Is sufficiently suppressed. The ratio of the internal mold release agent is more preferably in the range of 0.1 to 1% by mass, and particularly preferably in the range of 0.1 to 0.5% by mass.

  The molding material may contain additives such as a coupling agent as necessary. Examples of the coupling agent include silicon-based silane compounds, titanate-based, and aluminum-based coupling agents. In particular, an epoxy run coupling agent is suitable among silicon coupling agents. The coupling agent may be previously attached to the surface of the graphite particles by spraying or the like. The amount of the epoxy run coupling agent used is preferably in the range of 0.5 to 1.5 mass% with respect to the entire solid content of the molding material. In this range, bleeding of the coupling agent to the separator surface is sufficiently suppressed.

  The molding material may further contain short fibers such as carbon fibers and metal fibers. Moreover, the molding material may contain various additives within a range in which functions necessary for the separator are ensured.

  The molding material may contain a solvent. In particular, when a thin separator is produced, the molding material may be prepared in a liquid form (including varnish and slurry) by containing a solvent. The solvent can contain one or more selected from polar solvents such as methyl ethyl ketone, methoxypropanol, N, N-dimethylformamide, dimethyl sulfoxide, and the like.

  The content of ionic impurities in the separator is preferably small, and in particular, the sodium content in the separator is preferably 5 ppm by mass or less, and the chlorine content is preferably 5 ppm by mass or less. For this purpose, the content of ionic impurities in the molding material is preferably low. The content of ionic impurities is derived based on the amount of ionic impurities in the extraction water of the object. The extracted water can be obtained by putting the object into ion-exchanged water at a rate of 100 ml of ion-exchanged water with respect to 10 g of the object and treating it at 90 ° C for 50 hours. Ionic impurities in the extracted water are evaluated by ion chromatography. Based on the amount of ionic impurities in the extracted water, the amount of ionic impurities in the object is derived in terms of a mass ratio with respect to the object.

The molding material is preferably prepared such that the TOC (total organic carbon) of the separator is 100 ppm or less. When the TOC of the separator is 100 ppm or less, deterioration of the characteristics of the fuel cell is further suppressed. The TOC is a numerical value measured using an aqueous solution after the separator is put into ion-exchanged water at a rate of 100 ml of ion-exchanged water with respect to 10 g of the separator and treated at 90 ° C. for 50 hours. The TOC is measured by, for example, a total organic carbon analyzer “TOC-50” manufactured by Shimadzu Corporation based on JIS K0102. In the measurement, the CO ₂ concentration generated by burning the sample is measured by a non-dispersive infrared gas analysis method, and the carbon concentration in the sample is quantified. By measuring the carbon concentration, the organic substance concentration is indirectly measured, and the inorganic carbon (IC) and total carbon (TC) in the sample are measured. From the difference between the total carbon and inorganic carbon (TC-IC), the total organic Carbon (TOC) is measured. The value of TOC is reduced by selecting a high-purity component as each component constituting the molding material, further adjusting the equivalent ratio of the resin, or performing a post-curing process during molding.

  The molding material is prepared, for example, by mixing the above components in a predetermined ratio in an arbitrary order. For mixing the components, for example, a mixer such as a planetary mixer, a ribbon blender, a Redige mixer, a Henschel mixer, a rocking mixer, or a Nauta mixer is used.

  A molded body is obtained by molding the molding material, and a separator is obtained by subjecting the molded body to surface treatment.

  The method for molding the molding material is selected from appropriate mold molding methods such as injection molding, transfer molding, compression molding, and extrusion molding. In particular, when the compression molding method is employed, the dimensional accuracy of the separator can be improved and the mechanical strength of the separator can be improved.

  A groove for gas distribution is formed in the molded body. For example, when the molding material is molded, a mold having a convex portion corresponding to the groove is used, so that the groove is formed in the molded body. In addition, after forming a molded object, a groove | channel may be formed by performing mechanical processing, such as a cutting process, to this molded object. In addition, the groove | channel for distribute | circulating cooling water may be formed in a molded object further.

  When the compression molding method is employed, it is preferable that the molding material is molded by this mold in a state where the mold is disposed under a reduced pressure condition or a vacuum condition. In this case, the density variation of the molded body is reduced and the thickness accuracy of the molded body is increased. In particular, the degree of vacuum around the mold is preferably 80 kPa or more, and more preferably 95 kPa or more. The upper limit of the degree of vacuum is not particularly limited, but is practically up to 100 kPa.

  Although the heating temperature and compression pressure at the time of compression molding depend on the composition of the molding material, the molding thickness, and the like, it is preferable that the heating temperature and the compression pressure are set, for example, in the range of a heating temperature of 120 to 190 ° C and a compression pressure of 1 to 40 MPa. The molding time is preferably set in the range of 15 seconds to 600 seconds.

  After the compression molding, the mold is cooled, and then the molded body is taken out from the mold. This molded body may be further subjected to heat treatment. The heating temperature in this heat treatment is preferably in the range of 150 to 180 ° C., and the heating time is preferably in the range of 30 seconds to 1 hour.

  The molded body thus obtained is subjected to wet blasting. In the wet blasting process, a mixed liquid containing an abrasive is sprayed onto the inner surface of the gas flow groove in the molded body. In this case, for example, a wet blast process is performed on the entire surface of the molded body where the gas flow groove is formed, whereby the mixed liquid is injected onto the inner surface of the groove. By this wet blast treatment, the arithmetic mean height Sa (arithmetic mean height of the scale limited surface; Sa) defined by ISO 25178-2: 2012 is 0.5 to 1 on the inner surface of the groove for gas circulation. Adjusted to 5 μm. Thus, when the surface roughness of the inner surface of the gas circulation groove is adjusted, the hydrophilicity of the inner surface of the gas circulation groove becomes very high.

  The arithmetic average height Sa is derived from the measurement result of the three-dimensional surface property by a laser microscope. As the laser microscope, for example, a 3D measurement laser microscope (model number OLS4000) manufactured by Shimadzu Corporation is used.

  In the wet blast process, for example, the directivity in the injection direction of the abrasive is higher than in the case of the air blast process, and therefore, the abrasive is less likely to diffuse during the process. Therefore, in this embodiment, the wet blast treatment is employed, so that the mixed liquid containing the abrasive is easily sprayed onto the inner surface of the groove. Thereby, the surface roughness of the inner surface of the groove is easily adjusted.

  In the wet blast treatment, it is preferable that the liquid mixture is sprayed in an oblique direction with respect to the surface of the molded body on which the groove is formed. The mixed liquid is difficult to be sprayed onto the inner surface of the gas flow groove, but when the mixed liquid is sprayed in an oblique direction, the mixed liquid is easily sprayed onto the inner surface of the gas flow groove. For this reason, the roughness of the inner surface of the groove for gas circulation can be adjusted more easily.

  FIG. 1 shows an example of a wet blasting method in the present embodiment. In this example, the molded body 8 in which the straight type gas distribution groove 2 is formed is arranged so that the surface on which the groove 2 is formed faces upward. In addition, the groove | channel 7 for distribute | circulating a cooling water is also formed in the surface on the opposite side to the surface in which this groove | channel 2 is formed of this molded object 8. FIG.

In this state, the molded body 8 is conveyed by a conveying device 9 such as a conveyor in a direction crossing the longitudinal direction of the groove 2. Two nozzles 6 (a first nozzle 61 and a second nozzle 62) for injecting the mixed liquid are disposed above the conveyance path of the molded body 8. Each nozzle 6 has a long and wide shape along the longitudinal direction of the groove 2 in the molded body 8. From each nozzle 6, the mixed liquid is ejected in the form of a long wide strip (or curtain) along the longitudinal direction of the groove 2. In the figure, the injection direction of the mixed liquid is indicated by a broken line. The injection direction of the mixed liquid from each nozzle 6 is inclined with respect to the normal line of the surface of the molded body 8 where the groove 2 is formed. Further, the direction of inclination of the injection direction by the first nozzle 61 is opposite to the direction of inclination of the injection direction by the second nozzle 62. The inclination angles θ ₁ and θ _{2 in the} injection direction are appropriately set. For example, it is preferably 10 ° to 30 ° with respect to the normal line of the surface of the molded body 8 where the groove 2 is formed. The inclination angles θ ₁ and θ ₂ are angles that appear in a cross section orthogonal to the longitudinal direction of the groove 2 of the molded body 8. When the tilt angles θ ₁ and θ ₂ are 10 ° or more, the mixed liquid is effectively sprayed on the inner surface of the groove 2, and the roughness of the inner surface of the groove 2 is appropriately adjusted. Further, when the inclination angles θ ₁ and θ ₂ are 30 ° or less, wet blasting is also performed in a region other than the inside of the groove 2 in the molded body 8 (for example, a region sandwiched between two adjacent grooves 2). The surface treatment by the treatment is effectively performed. This effectively removes the skin layer and adjusts the surface roughness in this region. For this reason, the high contact resistance of the separator 20 can be maintained.

  In this example, when each of the first nozzle 61 and the second nozzle 62 injects the liquid mixture while the conveying device 9 is conveying the molded body 8, the entire surface of the molded body 8 on which the groove 2 is formed. Over this period, a wet blasting process is performed, and the skin layer is removed. At this time, a wet blast process is performed on the inside of the groove 2 by sequentially spraying the mixed liquid onto the plurality of grooves 2 formed in the molded body 8. Furthermore, since the injection direction of the mixed liquid from each nozzle 6 is inclined and the direction of the inclination is different between the first nozzle 61 and the second nozzle 62, the mixed liquid is present on both inner surfaces in the groove 2. Be sprayed. That is, wet blasting is performed on one inner surface of the groove 2 by the mixed liquid sprayed from the first nozzle 61, and the other inner surface of the groove 2 is sprayed by the mixed liquid sprayed from the second nozzle 62. Is subjected to wet blasting. For this reason, the skin layer is removed from the inner side surface of the groove, and the surface roughness of the inner side surface is easily adjusted.

  Furthermore, since the liquid mixture is also sprayed onto a region other than the inside of the groove 2 (for example, a region sandwiched between two adjacent grooves 2), the skin layer in this region is also removed and the surface of this region is removed. The roughness is also adjusted. Thereby, the contact resistance of the separator 20 is reduced.

The inner surface of the gas flow groove 2 in the molded body 8 and the separator 20 is inclined so as to face the opening of the groove 2 with respect to the normal of the surface on which the groove 2 is formed. preferable. In particular, the inclination angle θ _{3 of the} inner surface is preferably in the range of 1 to 10 ° with respect to the normal line of the surface on which the groove 2 is formed, and more preferably in the range of 3 to 7 °. The inclination angle θ ₃ is an angle that appears in a cross section orthogonal to the longitudinal direction of the groove 2. For example, the inclination angle θ ₃ is set to 5 °. In this case, the liquid mixture is easily sprayed on the inner surface of the groove 2 during the wet blasting process, and therefore, the wet blasting process is more effectively performed on the inner surface of the groove 2.

  The material of the abrasive (abrasive grain) used for the wet blast treatment is not particularly limited, and examples thereof include alumina, silicon carbide, zirconia, glass, nylon, and stainless steel. The average particle size of the abrasive is appropriately set, but is preferably in the range of 3 to 200 μm, preferably in the range of 3 to 60 μm, and preferably in the range of 6 to 45 μm. A range of ˜40 μm is more preferable. The average particle diameter of the abrasive is the particle diameter (d50) at the 50% cumulative height.

  The wet blasting method is not limited to the above. For example, when the mixed liquid is sprayed over a wide range from the nozzle, the wet blasting process may be performed while the molded body is conveyed in a direction along the longitudinal direction of the groove. The number of nozzles may be more than two. Only one nozzle may be used. In this case, for example, the wet blast process may be performed on the molded body, and then the inclination direction of the injection direction of the mixed liquid from the nozzle may be changed, and then the wet blast process may be performed again on the molded body. A wet blast process may be performed by moving a nozzle with respect to a molded object, without conveying a molded object.

  In the present embodiment, as shown in FIG. 1, a third nozzle 63 and a fourth nozzle 64 that eject the mixed liquid are also arranged below the transport path. Each of the nozzles 63 and 64 has a long and wide shape along the longitudinal direction of the groove 7 for circulating the cooling water in the molded body 8. From each of the nozzles 63 and 64, the mixed liquid is ejected in a long and wide strip shape (or curtain shape) along the longitudinal direction of the groove 2. The injection direction of the mixed liquid from the nozzles 63 and 64 is inclined with respect to the normal line of the surface of the molded body 8 where the groove 2 is formed. Further, the direction of inclination of the injection direction by the third nozzle 63 is opposite to the direction of inclination of the injection direction by the fourth nozzle 64. Thereby, in this embodiment, while the conveyance apparatus 9 conveys the molded object 8, a liquid mixture is injected from each nozzle 61, 62, 63, 64, and the groove | channel for gas distribution | circulation of the molded object 8 is formed. The surface to be formed and the surface opposite to the surface (hereinafter referred to as a water channel surface) are simultaneously subjected to wet blasting. For this reason, the skin layer is removed from the water channel surface, and the surface roughness is appropriately adjusted.

  In addition, when the groove | channel for gas distribution | circulation is formed in each of both surfaces of the thickness direction of a molded object, wet blasting may be performed simultaneously on both surfaces of a molded object. In this case, on each of both surfaces of the molded body, the skin layer on the inner surface of the gas flow groove may be removed and the surface roughness may be adjusted.

  It is also preferable that a hydrophilic treatment is performed on the inner side surface of the gas flow groove. The hydrophilic treatment is performed, for example, after wet blasting. It is also preferable that after the wet blasting treatment, the molded body is subjected to a hydrophilization treatment after being subjected to a cleaning treatment, or after the cleaning treatment is further subjected to a drying treatment. In the washing process, for example, the molded body is washed with ion exchange water or the like. In the drying process, the molded body is preferably air-dried by air blow or the like. In the drying process, the molded product is allowed to stand in a desiccator containing a desiccant such as silica gel, the molded product is allowed to stand in a dryer having a temperature of room temperature or higher (for example, 50 ° C.), and vacuum drying. A method of removing moisture from the molded body using a machine may be employed. By this drying treatment, the molded body is preferably dried until the moisture absorption rate is 0.1% or less.

  The hydrophilization treatment is a treatment for improving the hydrophilicity of the inner surface of the gas circulation groove. Thereby, higher hydrophilicity is imparted to the inner surface of the groove for gas circulation. The hydrophilic treatment may be performed over the entire surface of the molded body where the grooves are formed.

The hydrophilic treatment is not particularly limited as long as it is a treatment capable of improving the hydrophilicity of the inner surface of the gas circulation groove. The hydrophilization treatment includes, for example, plasma treatment for exposing the molded body to plasma, ozone gas treatment for exposing the molded body to ozone gas, SO ₃ treatment for exposing the molded body to SO ₃ , and fluorine for exposing the molded body to a gas containing fluorine. One or more types are selected from the treatment, the flame treatment in which a gas containing a modifier compound containing a silicon compound or an aluminum compound is burned, and the ozone water treatment in which ozone water is brought into contact with the molded body. In particular, it is preferable to employ plasma treatment.

  The plasma treatment is preferably atmospheric pressure plasma treatment, and particularly preferably remote atmosphere pressure plasma treatment. In the atmospheric pressure plasma processing by the remote method, for example, a plasma processing apparatus including a discharge space having an outlet and a discharge electrode for generating an electric field in the discharge space is used. In this plasma processing apparatus, a plasma generating gas is supplied to the discharge space, the pressure in the discharge space is maintained near atmospheric pressure, and a voltage is applied between the discharge electrodes to discharge the discharge space. When generated, plasma is generated in the discharge space. The gas stream containing the plasma is blown out from the outlet and blown onto the molded body, whereby the molded body is subjected to plasma treatment. Examples of such a plasma processing apparatus include the APT series manufactured by Sekisui Chemical Co., Ltd., but an appropriate plasma processing apparatus provided by Panasonic Corporation, Yamato Material Corporation, or the like may be used.

  When such a remote-type plasma treatment is employed, plasma is sprayed toward the surface of the molded body, so that the inner surface of the groove of the molded body is sufficiently processed. For this reason, the hydrophilic treatment is effectively performed on the inner surface of the groove, and the hydrophilicity of the inner surface of the groove is effectively improved. Further, the molded body is not exposed to electric discharge during the plasma treatment, and therefore, the molded body is hardly damaged during the plasma treatment.

  The atmospheric pressure plasma treatment is performed under conditions appropriately set so that desired hydrophilicity is imparted to the inner surface of the gas flow groove. The plasma generating gas in the atmospheric pressure plasma treatment is preferably nitrogen gas, and particularly preferably the oxygen content in the nitrogen gas is 2000 ppm or less. In this case, particularly high hydrophilicity is imparted to the inner surface of the groove by the atmospheric pressure plasma treatment.

  Further, when the equivalent ratio of the epoxy resin to the phenolic compound in the molding material is in the range of 0.8 to 1.2, the hydrophilicity of the surface of the separator is particularly increased by the plasma treatment.

  The atmospheric pressure plasma treatment is preferably performed under conditions in which the temperature of the molded body and the ambient temperature are adjusted so that condensation does not occur on the surface of the molded body. In this case, the consumption of plasma due to water droplets adhering to the surface of the compact is suppressed, and the processing efficiency is improved. As described above, the temperature of the molded body is preferably equal to or higher than the temperature at which no condensation occurs on the surface of the molded body (dew point temperature). For stable atmospheric pressure plasma treatment, the temperature of the compact is preferably 70 ° C. or lower. In order to stabilize the atmospheric pressure plasma treatment, it is also important to keep the temperature of the compact and the ambient temperature constant. In adjusting the atmospheric temperature, the temperature of the plasma unit of the plasma processing apparatus is usually adjusted. Depending on the configuration of the plasma processing apparatus, the temperature of the stage that supports the compact during plasma processing is adjusted.

  In the atmospheric pressure plasma processing, plasma processing other than the remote method, for example, direct plasma processing may be employed.

  The molded product after the plasma treatment may be left in the air as it is, but is subjected to a water contact treatment in which the molded product is brought into contact with water by immersing the molded product in water such as ion exchange water. It is preferable.

  The details of the mechanism of hydrophilic improvement by atmospheric pressure plasma treatment are unknown in this way, but the hydroxyl group is distributed on the surface of the molded body, so that moisture is adsorbed on this surface and functional groups are easily generated. By the atmospheric pressure plasma treatment, contaminants are removed from the surface of the molded body to be in a highly active state, and hydrophilic functional groups such as hydroxyl groups are introduced into the activated surface to make the surface of the molded body hydrophilic. It is considered that many functional groups are formed, which contributes to the improvement of hydrophilicity.

  In particular, when the molded body is subjected to the drying treatment as described above prior to the plasma treatment, the atmospheric pressure plasma treatment on the molded body is not easily inhibited by water molecules, and the efficiency of the atmospheric pressure plasma treatment is improved.

In the atmospheric pressure plasma treatment, it is preferable that no arc is generated in the molded body. For this purpose, for example, it is desirable that a grounding device is installed in the electrode part of the plasma processing apparatus. Further, when the above-mentioned water contact treatment is performed on the molded body after the plasma processing, the surface of the molded body Hydrophilicity is further improved. Although the detailed mechanism is not clear, it is considered that the hydrophilicity of the surface of the molded body is improved due to the adsorption of water molecules on the surface of the molded body activated by the atmospheric pressure plasma treatment.

  When the ozone gas treatment is employed, the treatment is performed by bringing ozone gas into contact with the surface of the molded body. For example, ozone gas can be brought into contact with the molded body by placing the molded body in a processing container and supplying a gas containing ozone gas into the processing container. Subsequently, the molded body may be left as it is in the atmosphere, or may be washed with water and then dried.

  The gas containing ozone gas may further contain oxygen gas, air, or the like. The ozone gas concentration is not particularly limited. For example, even if the ozone gas concentration is relatively low in the range of 3.5 to 8.0% by volume, the ozone gas concentration is relatively high in the range of 8.0 to 14.0% by volume. Also good. The treatment temperature is preferably in the range of −50 ° C. to 200 ° C., more preferably in the range of 0 ° C. to 100 ° C., further preferably in the range of 0 ° C. to 50 ° C., and in the range of room temperature to 30 ° C. Is most preferred. The treatment time is preferably in the range of 0.1 to 5 hours, and more preferably in the range of 0.2 to 1 hour. The atmospheric pressure during the treatment is preferably near normal pressure, but may be lower or higher than normal pressure, and is preferably in the range of several hPa to 0.2 MPa, for example.

  It is considered that the reason why the hydrophilicity is improved by such ozone gas treatment is that hydrophilic functional groups are introduced to the surface of the separator due to ozone reacting on the surface of the separator. When the equivalent ratio of the epoxy resin to the phenolic compound in the molding material is in the range of 0.8 to 1.2, the hydrophilicity of the separator surface is particularly increased by the ozone gas treatment. As a pretreatment for the ozone gas treatment, the molded body may be subjected to a plasma treatment using oxygen as a plasma generating gas.

If the SO ₃ treatment is employed, by contacting the gas (SO ₃ containing gas) containing SO ₃ for example, on the surface of the molded body, the processing is performed. In this case, for example, the molded body is housed in an acid-resistant sealed container, and the state in which the SO ₃ -containing gas is circulated in the sealed container is maintained for a certain period of time. Note that the molded body may be continuously passed through a chamber in which the SO ₃ -containing gas flows.

The SO ₃ -containing gas may further contain an inert gas such as nitrogen, argon or helium, oxygen, carbon dioxide gas or the like. The SO ₃ -containing gas may further contain a gaseous Lewis base. The SO ₃ concentration in the SO ₃ -containing gas is preferably in the range of 0.1 to 80% by volume, more preferably 0.1 to 10% by volume, and further preferably 0.1 to 5% by volume. preferable. The flow rate per minute of only the SO ₃ gas in the SO ₃ -containing gas in the closed container at the time of treatment is preferably in the range of 0.5 to 5 times the capacity of the closed container, and this flow rate is The range is preferably 0.01 to 10,000 ml / min. The treatment temperature is preferably in the range of 20 ° C to 100 ° C, more preferably 30 ° C to 80 ° C, and even more preferably 40 ° C to 70 ° C. The treatment time is preferably in the range of 0.1 seconds to 120 minutes, more preferably in the range of 1 to 60 minutes. Subsequent to the SO ₃ treatment, it is also preferable to immediately carry out post-treatment such as washing with water, treatment with an aqueous solution of sodium bicarbonate and lime water. In particular, it is preferable that the post-treatment includes a treatment for washing the molded body with an alkaline solution and a treatment for washing the molded body with ion-exchanged water at 10 ° C. or higher.

When the SO ₃ treatment is performed, SO ₃ reacts with the surface of the molded body to generate sulfonic acid groups, which are distributed on the surface of the molded body, thereby improving the hydrophilicity of the molded body. In particular, when hydroxyl groups on the surface of the SO ₃ pretreatment of the molded body is distributed, the generation of sulfonic acid groups at the surface of the molded product by the SO ₃ treatment is promoted significantly. Further, when the equivalent ratio of the epoxy resin to the phenolic compound in the molding material is in the range of 0.8 to 1.2, the hydrophilicity of the surface of the molding is particularly increased by the SO ₃ treatment. Further, as a pretreatment for the SO ₃ treatment, the molded body may be subjected to plasma treatment using oxygen as a plasma generating gas, heat treatment, flame treatment, corona treatment, ultraviolet irradiation treatment, and the like.

  When the fluorine treatment is employed, the fluorine treatment is performed, for example, by bringing a fluorine-containing gas (fluorine-containing gas) into contact with the surface of the molded body. In this case, for example, the molded body is housed in a sealed container, and after the inside of the sealed container is depressurized, an inert gas such as nitrogen gas is supplied into the sealed container, and then fluorine gas is supplied into the sealed container. . The molded body after the treatment may be left in the air as it is, or may be washed with water and then dried.

  The fluorine-containing gas may further contain an inert gas such as nitrogen, argon or helium, oxygen, carbon dioxide gas or the like. The fluorine concentration in the fluorine-containing gas is preferably in the range of 0.01 to 100% by volume. The treatment conditions for the fluorine treatment are set so that a sufficient amount of fluorine is efficiently introduced into the separator and the separator is not deteriorated or burned. For example, the treatment temperature is preferably −50 ° C. or higher and 200 ° C. or lower. This treatment temperature is more preferably 0 ° C. or higher, and even more preferably room temperature or higher. Further, this treatment temperature is more preferably 100 ° C. or less, further preferably 50 ° C. or less, and most preferably 30 ° C. or less. The treatment time is preferably from 1 second to 10 days. The practical treatment time is preferably in the range of 1 to 4 hours at the longest, and preferably 1 day or less even when the treatment is performed for a long time. The atmospheric pressure is preferably close to normal pressure, but may be lower or higher than normal pressure, and is preferably in the range of several hPa to 0.2 MPa, for example.

  The reason why the hydrophilicity of the surface of the molded body is improved by the fluorine treatment is that fluorine binds to the surface of the molded body and further reacts with water, so that -COOH groups are distributed on the surface of the separator. Conceivable. When the equivalent ratio of the epoxy resin to the phenolic compound in the molding material is in the range of 0.8 to 1.2, the hydrophilicity of the surface of the molding is particularly increased by the fluorine treatment. As a pretreatment for the fluorine treatment, a plasma treatment using oxygen as a plasma generating gas may be performed.

  When the flame treatment is employed, the flame treatment is performed, for example, by spraying a combustible gas containing a modifier compound onto the surface of the molded body while being burned. In this case, for example, the combustible gas is combusted with a burner or the like, and the molded body is moved while spraying the combustible gas toward the separator in the form of a curtain.

The modifier compound contains a silicon compound or an aluminum compound. There is no restriction | limiting in particular in a silicon compound and an aluminum compound. In consideration of easy availability and ease of handling, the silicon compound is preferably at least one compound selected from the group consisting of alkylsilane compounds, alkoxysilane compounds, siloxane compounds, and silazane compounds. The aluminum compound is preferably at least one compound selected from alkyl aluminum compounds and alkoxy aluminum compounds. These modifier compounds may be used individually by 1 type, or multiple types may be used together. As a specific example of the modifier compound, itro treatment agent manufactured by Itro Co., Ltd. containing a silicon compound can be mentioned. The ratio of the modifier compound in the combustible gas is not particularly limited, but is preferably in the range of 1 × 10 ⁻¹⁰ to 10 mol%. Moreover, the temperature of a flame may be controlled or the carrier effect may be exhibited by making the combustible gas contain air. The combustible gas preferably contains propane gas and hydrocarbon gas such as LPG (liquefied petroleum gas) as a fuel for combustion. The combustion temperature of the combustion gas is set in the range of 500 to 1500 ° C., for example. The blowing time of the combustible gas is set, for example, in the range of 0.1 to 100 seconds per 100 cm ^{2 of the} molded body area.

  It is considered that the hydrophilicity is improved by the flame treatment because fine particles such as silicon oxide and aluminum oxide adhere to the surface of the molded body. In particular, when hydroxyl groups are distributed on the surface of the molded body, the particles are firmly bonded to the molded body by the hydroxyl groups. For this reason, it becomes difficult for the particles to fall off from the molded body, and for this reason, the hydrophilicity of the surface of the molded body is maintained high over a long period of time. When the equivalent ratio of the epoxy resin to the phenolic compound in the molding material is in the range of 0.8 to 1.2, the hydrophilicity of the surface of the molding is particularly increased by the flame treatment. As a pretreatment for the flame treatment, a plasma treatment using oxygen as a plasma generating gas may be performed.

When the ozone water treatment is employed, the ozone water treatment is performed by bringing ozone water into contact with the molded body. Thereby, the hydrophilic property of the surface of a molded object improves. This is considered to be because functional groups such as carboxyl groups and hydroxyl groups are generated by oxidizing the surface of the molded body by ozone. The concentration of ozone water is preferably greater than 50 ppm, more preferably 80 ppm or more. Moreover, it is preferable that the density | concentration of this ozone water is 110 ppm or less. In the ozone water treatment, an appropriate technique such as immersing the molded body in ozone water is adopted. The treatment conditions are appropriately set, but the temperature of the ozone water is preferably normal temperature or lower, and particularly preferably in the range of 0 to 4 ° C. Moreover, it is preferable that the contact time (processing time) of a molded object and ozone water is 10 hours or more.
The separator may include a gasket. Hereinafter, a separator without a gasket is simply referred to as a separator 20, and a separator with a gasket is referred to as a separator 30 with a gasket. The separator 30 with a gasket has a structure in which the separator 20 and the gasket 12 are laminated. Examples of the gasket-attached separator 30 include a separator 31 with a gasket (see FIG. 4A) including, for example, a cathode-side separator 21 and a gasket 12 stacked on the first surface thereof, and an anode-side separator 22 and the first separator thereof. And a gasketed separator 32 (see FIG. 4B) including a gasket 12 superimposed on the second surface and a gasket 12 superimposed on the second surface.

  Gaskets include, for example, natural rubber, silicone rubber, SIS copolymer, SBS copolymer, SEBS, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber (HNBR). It is formed from a rubber material selected from chloroprene rubber, acrylic rubber, fluorine rubber and the like. This rubber material may contain a tackifier.

  In obtaining a separator with a gasket, for example, a gasket previously formed in a sheet shape or a plate shape is bonded and bonded to a molded body or a separator, for example.

  Further, the gasket may be formed by molding a material for forming the gasket on the surface of the molded body or the separator. In this case, for example, a material for forming a gasket on the surface of the molded body or the separator is applied by a screen printing method or the like, and subsequently, the material is cured to form a gasket on the molded body or the separator. May be. For example, an unvulcanized rubber material is applied to a predetermined position on the surface of a molded body or a separator by screen printing or the like, and a coating film of the rubber material is vulcanized, thereby a predetermined position on the surface of the molded body or the separator. A gasket having a desired shape may be formed. In the vulcanization, heating, irradiation with radiation such as an electron beam, or other appropriate vulcanization methods are employed. In this case, the gasket is easily laminated even on a thin molded body or separator.

  In addition, a molded body or a separator is set in a mold, and an unvulcanized rubber material is injected into a predetermined position on the surface of the molded body or separator, and the rubber material is heated and vulcanized. Thus, a gasket having a desired shape may be formed at a predetermined position on the surface of the molded body or the separator. Thus, in forming a gasket by metal mold | die shaping | molding, shaping | molding methods, such as compression molding and injection molding, can be employ | adopted besides transfer molding.

  When a gasket is formed by mold molding, it is preferable that the gasket is further heated after the molded body or separator on which the gasket is laminated is taken out of the mold. In this case, the curing reaction of the gasket further proceeds, thereby suppressing the elution of impurities from the gasket.

  When a separator with a gasket is manufactured, for example, the molded body is subjected to wet blasting for adjusting the surface roughness of the inner surface of the groove, and then the molded body is laminated with a gasket, and then the molded body is laminated. The molded body is subjected to wet blasting for adjusting the surface roughness of the inner surface of the groove. Furthermore, following this, the above-described hydrophilization treatment may be performed on the molded body.

  Moreover, when a separator with a gasket is manufactured, after the gasket is laminated on the molded body, the molded body may be subjected to a wet blasting process for adjusting the surface roughness of the inner surface of the groove. In this case, even when a component derived from the material for forming the gasket adheres to the molded body when the gasket is overlaid on the molded body, this component is removed from the molded body by wet blasting. For this reason, it is suppressed that the hydrophilic property of the inner surface of a groove | channel is reduced by the component derived from the material for forming a gasket. Moreover, since the component derived from the material for forming the gasket is removed and the surface roughness of the inner surface of the groove is adjusted, the manufacturing efficiency of the separator with gasket is improved. Further, following the wet blasting treatment, the above-described hydrophilization treatment may be performed on the molded body on which the gasket is laminated.

  Examples of the present invention will be described below. The present invention is not limited to these examples.

[Examples 1 to 6, Comparative Examples 1 and 2]
For each example, the raw material components shown in the table below were placed in a stirring mixer ("5XDMV-rr type" manufactured by Dalton) so as to have the composition shown in the table below and mixed with stirring. A molding material was obtained by pulverizing the mixture thus obtained to a particle size of 500 μm or less with a granulator.

  Using this molding material, a molded body was formed as follows. First, a mold composed of an upper mold and a lower mold was placed in a vacuum chamber. When 5 seconds have elapsed since the molding material was placed on the lower mold of the mold, pressure reduction in the vacuum chamber was started, and the vacuum chamber reached a vacuum level of 97 kPa over 10 seconds. Subsequently, the molding material was compression molded by lowering the upper mold toward the lower mold and clamping the mold. The compression molding conditions were a mold temperature of 170 ° C., a molding pressure of 35.3 MPa, and a molding time of 3 minutes. Next, the pressure was released while the mold was closed, and the mold was opened after being held for 30 seconds. Subsequently, the molded body was taken out from the mold.

The shape of the obtained molded body was a rectangular shape having a plan view of 200 mm × 250 mm, and the thickness was 1.5 mm at the thickest part and 0.5 mm at the thinnest part. In addition, by compression molding, 25 straight-type grooves having a width of 0.5 mm, a depth of 0.5 mm, and an inner surface inclined angle θ ₃ of 5 ° are formed on one surface (first surface) of the molded body. Formed. Further, 25 straight type grooves having a width of 0.5 mm and a depth of 0.5 mm were formed on the surface opposite to the first surface (second surface; water channel surface). This molded body is referred to as a “shaped A” molded body.

  In addition, in the “shape A” shaped body, a shaped body having a groove width of 1.0 mm formed on the first surface was obtained. This compact is referred to as a “shape B” compact.

  In addition, a molded body having a groove width of 2.0 mm in the “shaped A” molded body was also obtained. This molded body is referred to as a “shaped C” molded body.

Subsequently, wet blasting was performed on the first surface of each molded body. In the treatment, the molded body was conveyed in a direction perpendicular to the longitudinal direction of the groove with the first surface thereof facing upward. Two wide (250 mm wide) nozzles were disposed along the longitudinal direction of the grooves in the molded body above the conveyance path of the molded body. However, for Comparative Example 1, only one nozzle was disposed. From the nozzle, a mixed liquid containing an abrasive (alumina powder) was sprayed. The inclination angles θ ₁ and θ ₂ in the jetting direction of the mixed liquid from the nozzle are shown in the following table. The particle size d50 of the abrasive in the mixed solution is also shown in the table below.

  After the wet blast treatment, the three-dimensional surface property of the inner surface of the groove of the first surface in the molded body was measured with a 3D measurement laser microscope, and based on the result, ISO 25178-2: 2012 of the inner surface of the groove was measured. The specified arithmetic average height Sa was derived. As a result, Sa is less than 0.5 μm, “1”, 0.5 μm or more and less than 0.8 μm, “2”, 0.8 μm or more and less than 1.2 μm, “3”, 1.2 μm or more. The case of 1.6 μm or less was evaluated as “4”. The result is as shown in “Evaluation of arithmetic average height of inner surface of groove” in the table below.

  Subsequently, the molded body was washed with ion-exchanged water and further dried with hot air, and then the molded body was subjected to a remote atmospheric pressure plasma treatment. In the atmospheric pressure plasma treatment, AP-T series manufactured by Sekisui Chemical Co., Ltd. was used as the plasma treatment apparatus. Processing conditions are: processing width: 300 mm, number of plasma units: 1, sample-electrode distance: 3 mm, gas type for plasma generation: nitrogen, oxygen content in gas: 1000 ppm, gas flow rate: 150 L / min, sample transport Speed: 0.25 m / min, processing temperature: 25 ° C.

[Bending strength evaluation]
In each of the examples and comparative examples, a molded product for measuring bending strength having a size of 80 mm × 10 mm × 4 mm was prepared in the same manner as in the case of manufacturing a separator. The bending strength was measured under the condition of 2 mm / min. The results are shown in the table below.

[Evaluation of flexural modulus]
At the time of the measurement of the bending strength evaluation, the flexural modulus was measured simultaneously according to JIS K6911. The results are shown in the table below.

[Groove hydrophilicity evaluation]
1 μL of ion exchange water was dropped into the groove on the first surface of each separator. In this case, the spreading length of the ion exchange water along the longitudinal direction of the groove was measured. As a result, the case where the spread length was less than 15 mm was evaluated as “1”, the case where the spread length was 15 mm or more and less than 30 mm was “2”, and the case where the spread length was 30 mm or more was evaluated as “3”.

[Contact resistance evaluation]
Carbon paper was placed on the top and bottom of each separator, and copper plates were placed on the top and bottom, and a surface pressure of 1 MPa was applied in the up-down direction. The voltage between the two carbon papers was measured with a voltmeter, and the current between the two copper plates was measured with an ammeter, and the contact resistance was calculated from the result. The carbon paper used is TGP-HM series (090M: thickness 0.28 mm, 120M: thickness 0.38 mm) manufactured by Toray. The results are shown in Table 1.

[Limited oxygen utilization rate evaluation]
After applying ethylene-propylene-diene rubber to the outer peripheral part on the separator by screen printing, a gasket was formed by heat vulcanization. This obtained the separator with a gasket. Furthermore, a fuel cell composed of a standard single cell (electrode area 25 cm ² ) of the Japan Automobile Research Institute was fabricated using this separator with gasket and the membrane-electrode composite. With this fuel cell connected to an external circuit, the fuel cell was operated by increasing the oxygen utilization rate from 30% to 5% under the conditions of a fuel utilization rate of 60% and a current density of 0.3 A / cm ² . The test was stopped when the cell voltage was below 600 mV. An operation test of 5 hours was conducted at each oxygen utilization rate, and the highest oxygen utilization rate at which the cell voltage did not fluctuate and could be stably operated was evaluated as a critical oxygen utilization rate. When this limiting oxygen utilization rate is high, it can be said that the stability of power generation is enhanced by suppressing the clogging of the separator due to adhesion of water droplets.

In addition, the detail of the component used by the present Example is as follows. In addition, the mixture ratio in a table | surface is a ratio which converted all the components into solid content.
Epoxy resin: Cresol novolac type epoxy resin (“EOCN-1020-75” manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 199, melting point 75 ° C.).
Curing agent: novolak type phenol resin (“PSM6200” manufactured by Gunei Chemical Industry Co., Ltd., OH equivalent 105).
Curing accelerator: triphenylphosphine (“TPP” manufactured by Hokuko Chemical Co., Ltd.).
Natural graphite (“WR50A” manufactured by Chuetsu Graphite Industries Co., Ltd., average particle size 50 μm, ash content 0.05%, sodium ion 4 ppm, chloride ion 2 ppm).
Artificial graphite (“SGP100” manufactured by SEC Carbon Co., Ltd., average particle size 100 μm, ash content 0.05%, sodium ion 3 ppm, chloride ion 1 ppm).
Coupling agent: Epoxy silane (“A187” manufactured by Nippon Unicar Co., Ltd.).
Internal release agent A: natural carnauba wax (“H1-100” manufactured by Dainichi Chemical Co., Ltd., melting point 83 ° C.).
-Internal mold release agent B: Montanic acid bisamide ("J-900", manufactured by Dainichi Chemical Industry Co., Ltd., melting point: 123 ° C).

20 Separator 2 Gas distribution groove 8 Molded body

Claims (5)

A fuel cell separator comprising a cured product of a thermosetting resin component and graphite particles, wherein a groove for gas circulation is formed,
An arithmetic average height Sa defined by ISO 25178-2: 2012 on the inner surface of the groove is 0.5 to 1.6 μm. The fuel cell separator according to claim 1, wherein the inner surface of the groove is subjected to a hydrophilic treatment. A step of producing a molded body in which grooves for gas circulation are formed by molding a molding material containing graphite particles and a thermosetting resin component, and a mixed liquid containing an abrasive is contained in the grooves. Fuel including a step of adjusting the arithmetic average height Sa defined by ISO 25178-2: 2012 of the inner surface of the groove to 0.5 to 1.6 μm by performing a wet blast process for injecting the side surface A method for producing a battery separator. During the wet blast treatment, the mixed liquid is sprayed in a direction inclined by 10 ° to 30 ° with respect to the normal of the surface toward the surface on which the groove is formed in the molded body, The method of manufacturing a fuel cell separator according to claim 3, wherein the mixed liquid is injected onto an inner surface of the groove. The method for producing a fuel cell separator according to claim 3 or 4, further comprising a step of hydrophilizing the inner surface of the groove.

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