JP2011154972A - Method of manufacturing fuel cell separator, and fuel cell equipped with the fuel cell separator manufactured by the method - Google Patents

Abstract

The present invention provides a method for producing a fuel cell separator that suppresses desorption of metal ions from a fuel cell separator and suppresses a decrease in proton conductivity of an electrolyte due to desorption of metal ions and decomposition of the electrolyte.
A molding composition is prepared by blending raw material components including graphite particles and a resin component, and then the molding composition is molded in a process of molding the molding composition into a fuel cell separator A. Before, a metal component is removed from a molding composition using a magnet. By removing the metal component from the molding composition, the content of the metal component in the fuel cell separator A can be reduced.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a fuel cell separator, and a fuel cell including the fuel cell separator manufactured by the manufacturing method.

  In general, a fuel cell is composed of a cell stack in which several tens to several hundreds of unit cells are stacked in series, thereby obtaining a predetermined voltage.

  The most basic structure of the unit cell has a configuration of “separator / fuel electrode (anode) / electrolyte / oxidant electrode (cathode) / separator”. In this unit cell, fuel is supplied to the fuel electrode of the pair of electrodes facing each other through the electrolyte, the oxidant is supplied to the oxidant electrode, and the fuel is oxidized by an electrochemical reaction, so that the chemical energy of the reaction is increased. Directly converted to electrochemical energy.

  Such fuel cells are classified into several types depending on the type of electrolyte. Recently, solid polymer fuel cells using a solid polymer electrolyte membrane as an electrolyte have attracted attention as fuel cells that can provide high output. Has been.

  FIG. 1 shows an example of a polymer electrolyte fuel cell. Between two fuel cell separators A, A having a plurality of convex portions (ribs) 1a formed on the left and right side surfaces, an electrolyte 4 (solid polymer electrolyte membrane) and a gas diffusion electrode (fuel electrode 3a and oxidation) A single cell (unit cell) is configured by interposing a membrane-electrode assembly (MEA) 5 composed of the agent electrode 3b). A battery body (cell stack) is formed by arranging several tens to several hundreds of unit cells. Between adjacent convex portions 1a in the fuel cell separator A, a gas supply / discharge groove 2 which is a flow path for hydrogen gas as a fuel and oxygen gas as an oxidant is formed.

  Such a cell stack is composed of, for example, 50 to 100 unit cells in the case of a stationary type for home use, 400 to 500 unit cells in the case of loading on a car, It is composed of 10 to 20 unit cells.

In this polymer electrolyte fuel cell, hydrogen gas, which is a fluid, is supplied to the fuel electrode, and oxygen gas, which is a fluid, is supplied to the oxidizer electrode, whereby current is taken out from the external circuit. In the reaction, the reaction shown in the following formula occurs.
Fuel electrode reaction: H ₂ → 2H ⁺ + 2e ⁻ (1)
Oxidant electrode reaction: 2H ⁺ + 2e ⁻ + 1 / 2O ₂ → H ₂ O (2)
Overall reaction: H ₂ + 1 / 2O ₂ → H ₂ O
That is, hydrogen (H ₂ ) becomes proton (H ⁺ ) on the fuel electrode, and this proton moves through the solid polymer electrolyte membrane to the oxidant electrode and reacts with oxygen (O ₂ ) on the oxidant electrode. To produce water (H ₂ O). Accordingly, the operation of the polymer electrolyte fuel cell requires the supply and discharge of the reaction gas, the discharge of water, and the extraction of the current.

In addition, a methanol direct fuel cell (DMFC), which is a type of solid polymer fuel cell, supplies a methanol aqueous solution instead of hydrogen as a fuel. In this case, each electrode has the following formula: A reaction is occurring. An oxygen reduction reaction (the same reaction as when hydrogen is used as fuel) occurs at the air electrode.
Fuel electrode reaction: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1 ′)
Air electrode reaction: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (2 ′)
Overall reaction: CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O
Among the components constituting such a fuel cell, the fuel cell separator A has a plurality of gas supply / discharge grooves on one side or both sides of a thin plate-like body as shown in FIGS. 1 (a) and 1 (b). 2 and has the function of separating the fuel gas, oxidant gas and cooling water flowing in the fuel cell so that they do not mix, and also transmits the electric energy generated by the fuel cell to the outside. Or plays an important role in dissipating heat generated in the fuel cell to the outside.

  The fuel cell separator A is formed from a metal plate, a molding composition containing graphite particles and a resin component, or the like.

  In such a fuel cell, when the metal ions are desorbed from the fuel cell separator A, the metal ions diffuse into the electrolyte 4 and further trapped at the ion exchange site of the electrolyte 4, and as a result, the electrolyte 4. There is a possibility that the proton conductivity of the lowers. Further, the fuel cell separator A may be washed with water in the production process. In such a case, if the fuel cell separator A contains a metal component, a metal oxide (rust) is formed on the surface of the fuel cell separator A. Will appear. Then, the deterioration of the electrolyte 4 becomes remarkable.

In general, when metal (M) is ionized to form metal ion (M ²⁺ ), this metal ion causes a Fenton reaction shown in the following reaction formula to generate a hydroxy radical, and this hydroxy radical decomposes electrolyte 4. There is also a risk of it.

^{_{H 2 O 2 + M 2+ +}} H + → M 3+ + H 2 O + HO ·
Even when the fuel cell separator A is formed from a molding composition containing graphite particles and a resin component, a metal may be mixed into the graphite particles as a foreign substance, and this metal may cause the above problem. Of course, when artificial graphite is used as the graphite particles, especially when natural graphite is used, metals such as Cr, Mn, Fe, Co, Ni, Cu, and Zn are foreign matters in the natural graphite. May be mixed.

  In Patent Document 1, in view of the above problems, after removing the metal from the graphite particles in advance, the graphite particles and the resin component are mixed to prepare a molding composition, and the fuel cell separator is prepared from the molding composition. Is disclosed.

JP 2006-155936 A

  However, even with the method described in Patent Document 1, it is difficult to sufficiently reduce the metal content in the fuel cell separator A, and the proton conductivity of the electrolyte due to desorption of metal ions from the fuel cell separator is difficult. The decrease and the decomposition of the electrolyte could not be sufficiently suppressed.

  The present invention suppresses desorption of metal ions from a fuel cell separator, and a method of manufacturing a fuel cell separator capable of suppressing a decrease in proton conductivity of an electrolyte due to the desorption of metal ions and decomposition of the electrolyte. The purpose is to provide.

  Moreover, this invention aims at providing a fuel cell provided with the fuel cell separator manufactured by the manufacturing method of the said fuel cell separator.

  The method for producing a fuel cell separator according to the first invention includes a step of forming a molding composition by blending raw material components including graphite particles and a resin component, and then molding the molding composition, Before molding the molding composition, the metal component is removed from the molding composition.

  In the first invention, the method for removing the metal component from the molding composition is preferably suction removal using a magnet.

  In the first invention, the method for removing the metal component from the molding composition is preferably suction removal using a magnet.

  In 1st invention, before preparing the said composition for shaping | molding, it is preferable to remove a metal component from a graphite particle at least among the said raw material components previously.

  In the first invention, it is preferable to remove the metal component from all the raw material components in advance before preparing the molding composition.

  In 1st invention, it is preferable that the method of removing a metal component from the said raw material component is attraction | suction removal using a magnet.

  The method for producing a fuel cell separator according to the second invention includes a step of forming a molding composition by blending raw material components including graphite particles and a resin component, and then molding the molding composition, Before preparing the molding composition, the metal component is previously removed from all raw material components.

  In the first and second inventions, after molding the molding composition to obtain a molded body, the molded body is subjected to wet blasting, and the metal component from the slurry containing abrasive grains used in the wet blasting process. It is preferable to apply while removing with a magnet.

  In the first and second inventions, by removing the metal component, the amount of the metal component in the fuel cell separator is washed with hot water at 90 ° C. for 1 hour, and then at 90 ° C. for 1 hour. It is preferable that the metal oxide having a diameter larger than 100 μm does not exist on the surface of the fuel cell separator when the heat drying treatment is performed.

  A fuel cell according to a third invention includes the fuel cell separator manufactured by the first and second inventions.

  According to the present invention, desorption of metal ions from the fuel cell separator can be suppressed, and a decrease in proton conductivity of the electrolyte due to the desorption of metal ions and decomposition of the electrolyte can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS An example of embodiment of this invention is shown, (a) is a schematic perspective view which shows the unit cell of a fuel cell, (b) shows the fuel cell separator in the said unit cell, respectively. FIG. 6 is an exploded perspective view illustrating another example of a unit cell of a fuel cell that is configured using a gasket according to another example of the embodiment of the present invention. It is a perspective view which shows the further another example of embodiment of this invention, and shows an example of a fuel cell. (A) thru | or (c) is a schematic sectional drawing which shows the example of the suction removal apparatus used in embodiment of this invention, respectively. It is general | schematic sectional drawing which shows the example of the wet blast processing apparatus provided with the suction removal apparatus used in embodiment of this invention.

  Embodiments of the invention will be described below.

  A molding composition for producing a fuel cell separator A (hereinafter referred to as separator A) contains a resin component and graphite particles.

It is preferable that this molding composition does not contain a primary amine and a secondary amine. That is, it is preferable that this molding composition does not contain a compound having substituents —NH and —NH ₂ . Furthermore, it is preferable that the molding composition does not contain a tertiary amine. Thus, when the molding composition does not contain an amine, the separator A formed from the molding composition does not poison the platinum catalyst in the fuel cell, and the electromotive force when the fuel cell is used for a long time. Is suppressed.

  The resin component contained in the molding composition may be either a thermoplastic resin or a thermosetting resin.

  Examples of the thermoplastic resin include polyphenylene sulfide resin and polypropylene resin.

  When using a thermosetting resin, it is preferable that this thermosetting resin contains at least one of an epoxy resin and a thermosetting phenol resin. Epoxy resins and thermosetting phenol 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.

  The content of the epoxy resin and the thermosetting phenol resin with respect to the total amount of the thermosetting resin is preferably in the range of 50 to 100% by mass. It is particularly preferable if the thermosetting resin contains only an epoxy resin, only a thermosetting phenol resin, or only an epoxy resin and a thermosetting phenol resin.

  The epoxy resin is preferably solid, and particularly preferably has a melting point in the range of 70 to 90 ° C. Thereby, the change of a material decreases and the handleability of the molding composition at the time of shaping | molding improves. When the melting point is less than 70 ° C., aggregation tends to occur in the molding composition, and the handleability may be lowered. If a resin having a low melt viscosity is selected as the epoxy resin, the molding composition and the separator A can be highly filled with graphite particles while maintaining good moldability of the moldability composition. . In addition, a part of epoxy resin may be liquid within the range where the said effect | action is exhibited.

  As the epoxy resin, an ortho cresol novolak type epoxy resin, a bisphenol type epoxy resin, a biphenyl type epoxy resin, a phenol aralkyl type epoxy resin having a biphenylene skeleton, or the like is preferably used. This ortho-cresol novolac type epoxy resin, bisphenol type epoxy resin, and phenol aralkyl type epoxy resin having a biphenylene skeleton are excellent in that they have a good melt viscosity and a small amount of impurities, and in particular, a small amount of ionic impurities.

  In particular, the epoxy resin contains an epoxy resin component consisting only of an ortho cresol novolac type epoxy resin, or selected from an ortho cresol novolac type epoxy resin, a bisphenol type epoxy resin, a biphenyl type epoxy resin, and a phenol aralkyl type epoxy resin having a biphenylene skeleton. It is preferable that the epoxy resin component which consists of at least 1 type of is included. When an ortho-cresol novolac type epoxy resin is an essential component, the molding composition has excellent moldability and the separator A has excellent heat resistance. In addition, the manufacturing cost can be reduced. The proportion of the ortho-cresol novolac type epoxy resin in the epoxy resin component is preferably in the range of 50 to 100% by mass from the viewpoint of improving the moldability, improving the heat resistance of the separator A, and reducing the production cost. In particular, the range is preferably 50 to 70% by mass.

  It is also preferable to use a bisphenol type epoxy resin, a biphenyl type epoxy resin, or a phenol aralkyl type epoxy resin having a biphenylene skeleton together with the orthocresol novolac type epoxy resin. In this case, the melt viscosity of the molding composition can be further reduced, and when a thinner separator A is obtained, its toughness can be improved.

  In particular, when a bisphenol F type epoxy resin is used, the viscosity of the molding composition can be reduced, and a molding composition having particularly high moldability can be obtained. In this case, the content of the bisphenol F type epoxy resin in the epoxy resin component is preferably in the range of 30 to 50% by mass.

  In addition, when a biphenyl type epoxy resin is used, the biphenyl type resin has a low melt viscosity, can significantly improve the fluidity of the molding composition, and the thin moldability is particularly improved. In this case, the content of the biphenyl type epoxy resin in the epoxy resin component is preferably in the range of 30 to 50% by mass.

  Further, when a phenol aralkyl type epoxy resin having a biphenylene skeleton is used, the strength and toughness of the separator A can be improved, and the hygroscopicity of the separator A can be reduced. For this reason, the mechanical properties, electrical conductivity, and stability of the properties during long-term use of the separator A are excellent. The proportion of the phenol aralkyl type epoxy resin having a biphenylene skeleton in the epoxy resin component in this case is preferably in the range of 30 to 50% by mass.

  The content of the epoxy resin component with respect to the total amount of the thermosetting resin in the molding composition is preferably in the range of 50 to 100% by mass.

  The epoxy resin component is contained in the molding composition as at least part of the epoxy resin in the thermosetting resin. That is, as the thermosetting resin other than the epoxy resin component, for example, selected from epoxy resins other than the epoxy resin component, thermosetting phenol resin, vinyl ester resin, polyimide resin, unsaturated polyester resin, diallyl phthalate resin, etc. One or more kinds of resins may be used. However, it is desirable not to use a resin containing an ester bond because it may hydrolyze in an acid resistant environment. Moreover, it is also suitable to use a polyimide resin as a thermosetting resin at the point which contributes to the improvement of the heat resistance and acid resistance of the separator A. As such a polyimide resin, it is particularly preferable to use a bismaleimide resin, for example, 4,4-diaminodiphenyl bismaleimide. By using this together, the heat resistance of the separator A can be further improved.

  When using a thermosetting phenol resin, it is particularly preferable to use a phenol resin that undergoes a polymerization reaction by ring-opening polymerization. Examples of such phenol resins include benzoxazine resins. In this case, since gas due to dehydration is not generated in the molding process, voids are not generated in the molded product, and a decrease in gas permeability can be suppressed. It is also preferable to use a resol-type phenol resin, for example, a resol-type phenol resin having a structure of ortho-ortho 25-35%, ortho-para 60-70%, para-para 5-10% by 13C-NMR analysis. Is preferably used. The resol resin is usually in a liquid state, but the resol type phenol resin can easily adjust the softening point and can easily have a melting point of 70 to 90 ° C. Thereby, there is little change of material and the handleability at the time of shaping | molding improves. When the melting point is less than 70 ° C., aggregation tends to occur in the molding composition, and the handleability may be lowered.

  Moreover, you may use together other resin other than an epoxy resin and a thermosetting phenol resin. For example, one or more kinds of resins selected from polyimide resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, and the like can be used. However, it is desirable not to use a resin containing an ester bond because it may hydrolyze in an acid resistant environment.

  Moreover, it is also suitable to use a polyimide resin as a thermosetting resin at the point which contributes to the improvement of the heat resistance and acid resistance of the separator A. As such a polyimide resin, it is particularly preferable to use a bismaleimide resin, and specific examples thereof include 4,4-diaminodiphenyl bismaleimide. By using such other resins in combination, the heat resistance of the separator A can be further increased.

  When an epoxy resin is used, the molding composition has a curing agent as an essential component, and this curing agent includes a phenolic compound as an essential component. Examples of the phenol compound include novolak type phenol resins, cresol novolac type phenol resins, polyfunctional phenol resins, aralkyl-modified phenol resins, and the like.

  The content of the phenolic compound relative to the total amount of the curing agent is determined depending on the amount of the epoxy resin used. Further, it is particularly preferable that the curing agent is only a phenol compound.

  The total content of the thermosetting resin and the curing agent in the solid content of the molding composition is preferably in the range of 14 to 24.1% by mass.

  Moreover, when using together other hardening | curing agents other than a phenol type compound, it is preferable that another hardening | curing agent is a non-amine type compound, In this case, the electrical conductivity of the separator A can be maintained in a high state. At the same time, poisoning of the catalyst of the fuel cell can be suppressed. It is also preferable not to use an acid anhydride compound as a curing agent. When an acid anhydride-based compound is used, it is hydrolyzed in an acidic environment such as a sulfuric acid acidic environment, causing a decrease in the electrical conductivity of the separator A or increasing the elution of impurities from the separator A. There is a fear.

  When an epoxy resin is used as the thermosetting resin, the epoxy resin in the thermosetting resin and the phenolic compound in the curing agent when the thermosetting resin and the curing agent are blended are the epoxy resin for the phenolic compound. It is preferable that the equivalent ratio of is in the range of 0.8 to 1.2.

  Further, the graphite particles are used for reducing the electrical resistivity of the molded separator A and improving the conductivity of the separator A. The content of the graphite particles is preferably in the range of 75 to 90% by mass with respect to the total amount of the molding composition. Thus, when the ratio of the graphite particles is 75% by mass or more, the separator A is provided with sufficiently excellent conductivity. Further, by setting this proportion to 90% by mass or less, a sufficiently excellent moldability is imparted to the molding composition and a sufficiently excellent gas permeability is imparted to the separator A.

  The graphite particles can be used without limitation as long as they exhibit high conductivity, for example, those obtained by graphitizing carbonaceous materials such as mesocarbon microbeads, those obtained by graphitizing coal-based coke and petroleum-based coke. Any suitable powder such as a graphite electrode, a processed powder of a special carbon material, natural graphite, quiche graphite, expanded graphite, or the like can be used. Such graphite particles can be used alone or in combination of two or more.

  The graphite particles may be either artificial graphite powder or 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.

  Further, it is preferable that the graphite particles be purified, whether natural graphite powder or artificial graphite powder. In this case, since the ash content and ionic impurities are low, the separator is a molded product. The elution of impurities from A can be suppressed.

  Here, the ash content in the graphite particles is preferably 0.05% by mass or less, and if the ash content exceeds 0.05% by mass, the characteristics of the fuel cell manufactured using the separator A may be deteriorated. .

  Moreover, it is preferable that the average particle diameter of a graphite particle is the range of 15-100 micrometers. When the average particle size is 10 μm or more, the moldability of the molding composition is excellent, and when it is 100 μm or less, the surface smoothness of the separator A can be improved. In order to particularly improve the moldability, the average particle diameter is preferably 30 μm or more, and the surface smoothness of the separator A1 is particularly improved to increase the arithmetic average height Ra (JIS) of the surface of the separator A as described later. In order for B0601: 2001) to be in the range of 0.4 to 1.6 μm, particularly less than 1.0 μm, the average particle size is preferably 70 μm or less.

  In particular, when obtaining a thin separator A, the graphite particles preferably have a particle size that passes through a 100 mesh sieve (aperture 150 μm). If the graphite particles contain particles that do not pass through a 100-mesh sieve, graphite particles having a large particle size are mixed in the molding composition, and in particular, the molding composition is molded into a thin sheet. The formability at the time will fall.

  Further, the aspect ratio of the graphite particles is preferably 10 or less. In this case, it is possible to prevent the separator A from being anisotropic and to prevent deformation such as warpage.

  Regarding the reduction of the anisotropy of the separator A, the contact resistance ratio between the flow direction of the molding composition at the time of molding in the separator A and the direction orthogonal to the flow direction is 2 or less. It is preferable.

  Further, as the graphite particles, those having two or more types of particle size distribution, that is, those obtained by mixing two or more types of particles having different average particle diameters are also preferably used. In this case, it is particularly preferable to mix graphite particles having an average particle size of 1 to 50 μm and graphite particles having an average particle size of 30 to 100 μm. When graphite particles having such a particle size distribution are used, particles having a large particle size have a small surface area, so that it is expected that kneading is possible even with a small amount of resin. It is expected to increase the strength of the molded product while improving the contact properties of the separator A, thereby improving the performance of the separator A, such as an increase in density, conductivity, gas impermeability, and strength. You can plan. The mixing ratio of the particles having an average particle diameter of 1 to 50 μm and the particles having an average particle diameter of 30 to 100 μm is adjusted as appropriate, and the mixing ratio of the former to the latter is particularly 40:60 to 90:10, particularly 65:35. ~ 85: 15 is preferred.

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

  The molding composition may contain additives such as a curing catalyst, a wax (release agent), a coupling agent and the like as necessary.

  As a curing catalyst (curing accelerator), an appropriate one can be contained, but in order not to contain a primary amine and a secondary amine in the composition, a non-amine compound may be used. preferable. For example, amine-based diaminodiphenylmethane and the like are not preferable because the residue may poison the fuel cell catalyst. In addition, imidazoles are less preferred because they easily release chlorine ions after curing, and may cause impurity elution.

  However, the hydrocarbon in the second position has a weight loss of 5% or less 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 temperature of 30 minutes. Use of a substituted imidazole having a group is preferable in that the storage stability of the molding composition can be improved. In particular, when a thin separator A is obtained, the volatility when the sheet-like separator A is formed from the molding composition prepared in a varnish shape, the smoothness of the separator A, and the like are improved. As this substituted imidazole, it is particularly preferable to use a substituted imidazole having 6 to 17 carbon atoms in the 2-position hydrocarbon group. Specific examples thereof include 2-undecylimidazole, 2-heptadecylimidazole, and 2-phenyl. Examples include imidazole and 1-benzyl-2-phenylimidazole. Of these, 2-undecylimidazole and 2-heptadecylimidazole are preferred. These compounds are used alone or in combination of two or more. The content of such a substituted imidazole is appropriately adjusted, whereby the molding and curing time can be adjusted. The content of the substituted imidazole 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 composition.

  Further, a phosphorus compound is preferably used as the curing catalyst. Moreover, you may use together a phosphorus compound and the said substituted imidazole. An example of a phosphorus compound is triphenylphosphine. When such a phosphorus compound is contained, elution of chlorine ions from the separator A which is a molded product can be suppressed.

  The content of such a curing catalyst is appropriately adjusted, but is preferably in the range of 0.5 to 3 parts by mass with respect to the epoxy resin.

  As the coupling agent, an appropriate one is used, but it is preferable not to use aminosilane so as not to contain the primary amine and the secondary amine in the molding composition. When aminosilane is used, there is a risk of poisoning the fuel cell catalyst, which is not preferable. Further, it is preferable not to use mercaptosilane as a coupling agent. Similarly, when this mercaptosilane is used, there is a risk of poisoning the fuel cell catalyst.

  Examples of coupling agents used include silicon-based silane compounds, titanate-based, and aluminum-based coupling agents. For example, epoxy silane is suitable as a silicon-based coupling agent.

  When the epoxysilane coupling agent is used, the amount used in the solid content of the molding composition is preferably in the range of 0.5 to 1.5% by mass. In this range, the coupling agent can be sufficiently suppressed from bleeding on the surface of the separator A.

  The coupling agent may be previously attached to the surface of the graphite particles by spraying or the like. The amount added in that case is appropriately set, and it is necessary to consider the specific surface area of the graphite particles and the coating area per unit mass of the coupling agent, but preferably the coating area of the coupling agent The total amount is in the range of 0.5 to 2 times the total surface area of the graphite particles. In this range, the coupling agent can be sufficiently suppressed from bleeding on the surface of the separator A, and contamination of the mold surface can be suppressed.

  In addition, an appropriate wax is used as the wax (internal mold release agent). However, particularly at 120 to 190 ° C., an internal release that undergoes phase separation without being compatible with the thermosetting resin and the curing agent in the molding composition. Preferably, a mold is used. 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 exhibits a good release improving effect by phase separation from the thermosetting resin and the hardener in the molding process of the molding composition.

  Further, the content of the internal mold release agent is appropriately set according to the complexity of the shape of the separator A, the groove depth, the ease of releasability from the mold surface such as the draft, etc., but the molding composition It is preferable to be in the range of 0.1 to 2.5% by mass with respect to the total amount, and when the content is 0.1% by mass or more, sufficient mold release properties are exhibited at the time of mold molding, When the content is 2.5% by mass or less, the hydrophilicity of the separator A is sufficiently suppressed by the wax. The content of the wax 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.

  In particular, when a thin separator A is obtained, the molding composition may be prepared in a liquid form (including varnish and slurry) by containing a solvent in the molding composition. As the solvent, it is preferable to use a polar solvent such as methyl ethyl ketone, methoxypropanol, N, N-dimethylformamide, dimethyl sulfoxide or the like. Moreover, a solvent may use only 1 type and may use 2 or more types together. The amount of the solvent used is appropriately set in consideration of the moldability when the sheet-like separator A is produced from the molding composition, but preferably the viscosity of the molding composition is in the range of 1000 to 5000 cps. The usage amount is set. In addition, what is necessary is just to use a solvent as needed, and it is not necessary to use a solvent, if a molding composition can be prepared in a liquid state by using liquid resin as a thermosetting resin.

  Further, the content of ionic impurities in the separator A is preferably such that the sodium content is 5 ppm or less and the chlorine content is 5 ppm or less by mass ratio with respect to the total amount of the molding composition. The product is preferably prepared so that the content of ionic impurities in the molding composition is 5 ppm or less and the chlorine content is 5 ppm or less by mass ratio with respect to the total amount of the molding composition. In this case, elution of ionic impurities from the separator A can be suppressed, and deterioration in characteristics such as a decrease in starting voltage of the fuel cell due to the elution of impurities can be suppressed.

  In order to reduce the content of ionic impurities in the separator A and the molding composition as described above, as components such as a thermosetting resin, a curing agent, graphite, and other additives constituting the molding composition. In addition, it is preferable to use a component in which the content of ionic impurities is a sodium content of 5 ppm or less and a chlorine content of 5 ppm or less by mass ratio with respect to each component.

  Here, the content of the ionic impurities is derived based on the amount of the ionic impurities in the extraction water of the object. The extracted water is obtained by putting an 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. The ionic impurities in the extracted water are evaluated by ion chromatography. And based on the amount of ionic impurities in the extracted water to be derived, the amount of ionic impurities in the object is converted into a mass ratio with respect to the object and is derived.

  Moreover, it is preferable that the molding composition is prepared so that the TOC (total organic carbon) of the separator A formed with this composition is 100 ppm or less.

  Here, TOC is a numerical value measured using an aqueous solution after the separator A is charged into the ion exchange water at a rate of 100 ml of ion exchange water with respect to 10 g of the mass of the separator A and treated at 90 ° C. for 50 hours. . Such a TOC can be measured by, for example, Shimadzu total organic carbon analyzer “TOC-50” in accordance with JIS K0102. In the measurement, the CO2 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 concentration of organic substances contained indirectly can be measured, the inorganic carbon (IC) and total carbon (TC) in the sample are measured, and the difference between the total carbon and inorganic carbon (TC− IC) to measure total organic carbon (TOC).

  By making the TOC 100 ppm or less, it is possible to further suppress the deterioration of characteristics as a fuel cell.

  The value of TOC can be reduced by selecting high-purity components as the constituents of the molding composition, further adjusting the equivalent ratio of the resin, or performing post-curing treatment during molding. .

  A separator A is obtained by blending the raw material components as described above to prepare a molding composition and molding the molding composition. Thus, in manufacturing the separator A, the metal component is removed from at least one of the raw material component, the molding composition, and the separator A. In particular, it is preferable to remove the metal component from at least the molding composition. Thereby, content of the metal component of a fuel cell separator can be reduced.

  In preparing the molding composition, it is preferable to remove the metal component from components (hereinafter referred to as raw material components) blended in the molding composition in advance. That is, it is preferable to previously remove the metal component from at least one of the graphite particles, the resin component, and other raw material components. In particular, it is preferable to remove the metal component in advance from at least the graphite particles. In this case, the metal component content of the fuel cell separator can be more reliably reduced by removing the metal component from the graphite particles in advance. In addition, the resin component may also contain a metal component as an impurity during the production process. For this reason, it is preferable to remove the metal component from the resin component in advance. In addition, the raw material components other than the graphite particles and the resin component may contain a metal component as an impurity in the production process or the like. For this reason, it is preferable to remove the metal component from the raw material components other than the graphite particles and the resin component in advance.

  In particular, it is preferable to remove the metal component from all raw material components in advance. In this case, the metal component content in the fuel cell separator can be further reliably reduced by removing the metal component from all the raw material components in advance.

  When the metal component is previously removed from the raw material component, the total content of Fe, Co, and Ni in the raw material component is preferably 1 ppm by mass or less, more preferably 0.5 ppm by mass or less. Remove metal components. Furthermore, from the raw material component to the metal component so that the total content of Cr, Mn, Fe, Co, Ni, Cu and Zn in the raw material component is preferably 1 ppm by mass or less, more preferably 0.5 ppm by mass or less. Remove.

  Further, it is preferable that a metal component having a diameter of 35 μm or more is removed from the raw material component, and further a metal component having a diameter of less than 35 μm is also removed.

  As an example of a method for removing the metal component from the raw material component, there is a method of sucking and removing the metal component in the raw material component using a magnet. In this case, the metal component can be sufficiently removed from the raw material component, and in particular, the content of the magnetic substance can be reduced. As the magnet, a permanent magnet or an electromagnet can be used. In the case of a permanent magnet, it is particularly preferable to use at least one selected from neodymium rare earth magnets and samarium cobalt rare earth magnets. In this case, the metal component can be easily removed. In order to reliably remove the metal component, the magnetic force (magnetic flux density) of the magnet is preferably 10,000 Gauss or more, more preferably 20000 Gauss or more, and from the viewpoint of operability, it is 30000 Gauss or less. Is preferred. However, since the magnetic force (magnetic flux density) of a normal neodymium rare earth magnet is up to 12000 gauss, or up to about 14000 gauss, the magnetic force (magnetic flux density) when using a normal neodymium rare earth magnet is 12000 gauss or less. Or 14,000 gauss or less. In order to improve the removal efficiency of the metal component, it is preferable to use a magnet having a larger magnetic force in the above range.

  As a first example of an apparatus for sucking and removing a metal component from a raw material component using a magnet (hereinafter referred to as a suction removing apparatus 27), an object (here, a raw material component) as shown in FIG. ), And a device configured by arranging magnets 29 on both sides of the passage 28 through which is passed. The magnet 29 may be a permanent magnet or an electromagnet. Each magnet 29 is provided such that different magnetic poles are arranged on the opposing surfaces. Each magnet 29 is preferably formed such that the opposed surfaces facing each other via the passage 28 are uneven, and the convex portions and the concave portions appearing on the respective opposed surfaces are formed symmetrically. The magnetic field gradient generated in the When the object or slurry in which the object is dispersed is passed through the passage 28 between the magnets 29 in the suction removing device 27, particularly the magnetic material among the metal components in the object is attracted to the magnet 29. To be removed. The object after passing through this passage 28 is collected in an appropriate collection container.

  Examples of the magnetic material include Fe, Co, and Ni, and also alloys having magnetism. For example, stainless steel such as SUS430 having magnetism is also removed. Further, SUS304 and SUS316 do not have magnetism in a normal state, but become magnetized when stress is applied. For example, when stress is applied to a part such as a SUS304 or SUS316 screw used in various devices during processing or screw tightening, the SUS304 or SUS316 constituting the part has magnetism. It becomes like this. SUS304 and SUS316 having such magnetism are also removed from the object.

  In the suction removal device 27 of the first example, a plurality of rod-shaped adsorbers made of a magnetic material such as iron, cobalt, or nickel are arranged at intervals in the passage 28 between the magnets 29. Also good. For example, the adsorbents are provided in parallel so that the longitudinal direction thereof is orthogonal to the direction of passage of the object in the passage 28. When an object or a slurry in which the object is dispersed is passed through the passage 28 between the magnets 29 in the suction removal device 27 (see arrow A in the figure), among the metal components in the object, The magnetic body is removed by adsorbing to the adsorbent. The object after passing through this passage 28 is collected.

  As a second example of the suction / removal device 27, there is a suction / removal device 27 configured by arranging a plurality of rod-shaped magnets 29 at intervals in a passage 28 through which an object passes. The rod-shaped magnets 29 are provided so as to be arranged in a grid, for example. Further, two or more grids composed of a plurality of rod-shaped magnets 29 may be provided along the direction of passage of the object in the passage 28. In addition, a plurality of rod-shaped magnets 29 provided in the passage 28 can rotate around a common rotation axis along the longitudinal direction of the rod-shaped magnet 29 in the passage 28. Also good. When the object or the slurry in which the object is dispersed is passed through the passage 28 in the suction removal device 27 (see arrow A in the figure), among the metal components in the object, particularly the magnetic material is It is attracted to the rod-shaped magnet 29 and removed. The object after passing through this passage 28 is collected.

  As a third example of the suction / removal device 27, there is an apparatus that separates a metal component from the object by using the attractive force of the magnet while dropping the object on the peripheral surface of a cylindrical body 30 having a magnet. Can be mentioned. The cylindrical body 30 rotates around a horizontal rotation axis.

  The magnet in the cylindrical body 30 is provided at an appropriate position. For example, inside the cylindrical body 30, a magnet that is long in the rotational axis direction of the cylindrical body 30 and rotates axially in the same direction as the cylindrical body 30 is located near the upper portion of the cylindrical body 30 and one side portion of the cylindrical body 30. (When the cylindrical body 30 rotates to the right, it is provided to the right, and when it rotates to the left, it is provided to the left).

  A plurality of magnets may be provided inside the cylindrical body 30 so as to be arranged along the circumferential surface of the cylindrical body 30. In this case, for example, a plurality of magnets having magnetic poles arranged in the radial direction of the cylindrical body 30 are arranged at intervals. The magnets are arranged so that the directions of the magnetic poles are alternately reversed. A plurality of magnets having magnetic poles arranged in the circumferential direction of the cylindrical body 30 are arranged between the magnets. This magnet is also arranged in the opposite direction of the magnetic poles alternately. Alternatively, a plurality of magnets may be arranged on the cylindrical peripheral surface in the same manner as described above.

  In the suction removal device 27 of the third example, when an object is dropped onto the rotating cylindrical body 30 (see arrow A in the figure), the object is biased by the rotational force of the cylindrical body 30. It falls while being done (see arrow B in the figure). On the other hand, a component including a metal component (especially a magnetic material) in the object is attracted to the magnet of the cylindrical body 30 and is attracted to the cylindrical body 30, or the dropping trajectory from the cylindrical body 30 by the attractive force from the magnet. Is changed (see arrow C in the figure). For this reason, the component containing a metal component is adsorbed by the cylindrical body 30 and removed. Even if the component containing the metal component falls from the cylindrical body 30, it falls to a position different from the drop position of the component not containing the metal component. As a result, the object is sorted into a component containing a metal component and a component not containing a metal component.

  A plurality of types of suction / removal devices 27 may be combined, or the same type of suction / removal devices 27 may be provided in multiple stages.

  In the suction removal device 27 as described above, a strong magnetic field and a weak magnetic field may occur in the path through which the object passes, and metal components are removed from the object passing through the weak magnetic field. It may be difficult to be done. In such a case, it is preferable to provide the suction removal device 27 with a shielding object that shields the path leading to the portion where the magnetic field is weak. Examples of the shield include a member having a slit that leads only to a portion where the magnetic field is strong.

  In this way, by removing the metal component from the raw material component by suction using a magnet, the metal component, particularly the magnetic material (Fe, Co, Ni, etc.) can be removed from the raw material component, Fe in the raw material component, The contents of Co and Ni can be particularly reduced.

  Examples of the method for removing the metal component from the graphite particles include a method of washing the graphite particles using a strongly acidic solution having a pH of 2 or less. As the strongly acidic solution, for example, aqua regia obtained by mixing concentrated nitric acid having a concentration of 69% by mass and concentrated hydrochloric acid having a concentration of 36% by mass in a ratio of 1: 3 by volume ratio, hydrochloric acid having a concentration of 15% by mass or more, At least one selected from sulfuric acid having a concentration of 15% by mass or more and nitric acid having a concentration of 15% by mass or more can be used. In this case, the metal component can be easily removed from the graphite particles. The concentration of the hydrochloric acid water, the sulfuric acid water and the nitric acid water is preferably 30% by mass or less from the viewpoint of operability.

  The method for removing the metal component from the raw material component is not limited to the above method. As a method other than the above, for example, when removing a metal component from graphite particles, the metal component is eluted and removed in the electrolyte solution by performing an electrolysis reaction in the electrolyte solution using the graphite particles as an electrode. A method is mentioned. Other appropriate methods may be employed.

  The molding composition is prepared by mixing the above-described components by an appropriate technique, and kneading and granulating as necessary.

  After preparing the molding composition, it is preferable to remove the metal component from the molding composition. In this case, even when a metal component is mixed in preparing the molding composition, the metal component can be removed from the molding composition. In this case, the metal component can be sufficiently removed from the molding composition, and in particular, the content of the magnetic substance can be reduced.

  When removing the metal component from the molding composition, the total content of Fe, Co, and Ni in the molding composition is preferably 1 mass ppm or less, more preferably 0.5 mass ppm or less. The metal component is removed from the molding composition. Further, the molding composition is such that the total content of Cr, Mn, Fe, Co, Ni, Cu and Zn in the molding composition is preferably 1 ppm by mass or less, more preferably 0.5 ppm by mass or less. Remove metal components from objects.

  Further, it is preferable that a metal component having a diameter of 35 μm or more is removed from the molding composition, and further, a metal component having a diameter of less than 35 μm is also removed.

  Examples of the method for removing the metal component from the molding composition include a method in which the metal component in the molding composition is removed by suction using a magnet, as in the method for removing the metal component from the raw material component. When the metal component in the molding composition is removed by suction using a magnet, the same suction removal device 27 as that of the raw material component can be used.

  In order to remove the metal component from the raw material component or the molding composition until the content becomes a predetermined value or less, after removing the metal component from the raw material component or the molding composition by the method exemplified above, The content of the metal component of the raw material component or the molding composition is measured by inductively coupled plasma (ICP) analysis, and the raw material component or the molding composition is measured until the measurement result becomes a predetermined value or less. It is preferable to repeat the removal of the metal component from.

  The molding composition 1 (separator A) can be obtained by molding this molding composition. As a molding method, an appropriate method such as injection molding or compression molding can be employed. For example, as shown in FIG. 1, the separator A is formed with a plurality of convex portions (ribs) 1 a on both surfaces, so that hydrogen gas as a fuel and an oxidizing agent are formed between the adjacent convex portions 1 a. A gas supply / discharge groove 2 which is a flow path of oxygen gas is formed.

  The separator A is composed of an anode side separator having a gas supply / discharge groove 2 only on one side, and a cathode side separator having a gas supply / discharge groove 2 only on one side opposite to the anode side separator. Also good. By superposing the anode side separator and the cathode side separator, a separator A having gas supply / discharge grooves 2 on both sides as shown in FIG. 1 is formed. A channel through which cooling water flows may be formed between the anode side separator and the cathode side separator. In this case, it is preferable to interpose a gasket between the anode side separator and the cathode side separator.

  When the thin separator A is obtained from the molding composition prepared in a varnish shape, the molding composition is first molded into a sheet to obtain a fuel cell separator molding sheet (molding sheet). The molding composition is formed into a sheet by, for example, casting (progressive) molding. In this case, a plurality of types of film thickness adjusting means can be used. Such a casting method using a plurality of types of film thickness adjusting means can be realized, for example, by using a multi-coater that has already been put into practical use. As a film thickness adjusting means for casting, it is preferable to use a slit knife and at least one of a doctor knife and a wire bar, that is, either one or both. The thickness of this molding sheet is preferably 0.05 mm or more, and more preferably 0.1 mm or more. The thickness is preferably 0.5 mm or less, and more preferably 0.3 mm or less. Thus, by making the thickness of the molding sheet 0.5 mm or less, the separator 1 can be made thinner and lighter, and the cost thereof can be reduced. In particular, if the thickness is 0.3 mm or less. When the solvent is used, the remaining solvent in the molding sheet can be effectively suppressed. Further, when this thickness is less than 0.05 mm, the advantage in producing the separator A is not sufficiently exhibited, and this thickness is preferably 0.1 mm or more considering the formability in particular.

  The molding sheet is made into a semi-cured (B stage 20) state by drying along with casting, and this is compressed and thermoset to form a plurality of convex portions (ribs) 1a on both sides. A gas supply / discharge groove 2 can be formed between the portions (ribs) 1a to obtain the separator A. At this time, when the separator A is formed in a corrugated plate shape and the gas supply / discharge groove 2 on the other surface side is formed on the back side of the convex portion 1a on the one surface side, a plurality of the thin films are formed on both surfaces while being thin. The separator A having the convex portions (ribs) 1a and the gas supply / discharge grooves 2 between the convex portions (ribs) 1a can be obtained.

  At the time of compression / thermosetting molding of the molding sheet, first, the molding sheet is cut (cut) or punched into a predetermined plane dimension as necessary, and is thermally cured in a mold by a compression molding machine. The conditions of this compression / thermosetting molding depend on the composition of the molding composition, the type of conductive substrate, the molding thickness, etc., but the heating temperature is in the range of 120 to 190 ° C., and the compression pressure is in the range of 1 to 40 MPa. It is preferable to set by.

  In the production of the separator A, the separator A may be produced by molding one molding sheet, or the separator A may be produced by stacking a plurality of molding sheets.

  By forming the molding sheet in this manner, a thin separator A, particularly a separator A having a thickness in the range of 0.2 to 1.0 mm can be manufactured. Thus, by using the molding sheet at the time of manufacturing the separator A, it becomes easy to form the molding material thinly and uniformly even when manufacturing the thin separator A, and the moldability and thickness accuracy are high. Become.

  When the separator A is manufactured, a molding sheet and an appropriate conductive substrate may be laminated and molded. When a conductive substrate is used, the mechanical strength of the separator A can be improved. When a conductive substrate is used, compression / thermosetting can be performed in a state in which molding sheets (including a laminate of a plurality of molding sheets) are laminated on both sides of the conductive substrate, or Compression / thermosetting can be performed in a state where conductive substrates are laminated on both sides of a molding sheet (including a laminate of a plurality of molding sheets).

  Examples of the conductive substrate include carbon paper, carbon prepreg, carbon felt and the like. Moreover, these electroconductive base materials may contain base material components, such as glass and resin, in the range which does not impair electroconductivity. The thickness of the conductive substrate is preferably in the range of 0.03 to 0.5 mm, and more preferably in the range of 0.05 to 0.2 mm.

  The molded body 1 (separator A) is preferably subjected to blasting or the like to remove the surface skin layer and adjust the surface roughness of the separator A.

  The arithmetic average height Ra (JIS B0601: 2001) of the surface of the separator A is preferably in the range of 0.4 to 1.6 μm. In this case, gas leakage at the joint between the separator A and the gasket 12 can also be suppressed. For this reason, it is not necessary to mask the part joined to the gasket 12 in the separator A during the wet blasting process, and the production efficiency of the separator A is improved. Note that it is difficult to make the arithmetic average height Ra less than 0.4 μm, and if this value is greater than 1.6 μm, the gas leak may not be sufficiently suppressed. The arithmetic average height Ra of the surface of the separator A is particularly preferably 1.2 μm or less. Furthermore, when the arithmetic average height Ra of the surface of the separator A is less than 1.0 μm, the gas leak is particularly suppressed, and even if the fastening force at the time of manufacturing the cell stack is lowered as the separator A is thinned, Gas leak can be sufficiently suppressed. It is also preferable that the arithmetic average height Ra of the surface of the separator A is 0.6 μm or more.

Further, the contact resistance of the surface of the separator A is preferably 15 mΩcm ² or less. In this case, the function of the separator A for transmitting the electric energy generated by the fuel cell to the outside can be maintained at a high level.

  At the time of the blasting treatment, it is preferable that the molded body 1 (separator A) is subjected to a wet blasting treatment, and in this treatment, a metal component is removed with a magnet from a slurry containing abrasive grains such as alumina particles. Abrasive grains used for blasting may contain metal components as impurities, and metal components may be mixed in slurry containing abrasive grains during blasting. When blasting is performed using a slurry containing such a metal component, the metal component is driven from the abrasive grains onto the surface of the separator A. However, when the wet blasting process is performed using the abrasive grains while removing the metal component from the slurry with a magnet as described above, the metal component is prevented from adhering to the separator A during the blasting process. In other words, while removing the skin layer and adjusting the surface roughness by the wet blasting process, metal components such as metal foreign matters contained in the abrasive grains in the slurry are prevented from being driven into the separator A during the wet blasting process. can do.

  FIG. 5 shows a schematic configuration of an apparatus (wet blasting apparatus) used for the wet blasting process. This wet blasting apparatus includes a stage 20 on which a molded body 1 (separator A) to be processed is conveyed. The stage 20 is provided with nozzles 21 for injecting the slurry 26 toward the processing target above and below the processing target. The slurry 26 is obtained by dispersing abrasive grains such as alumina particles in a dispersion medium such as water. Although not shown, the stage 20 is sequentially provided with a fountain nozzle for injecting water and a hot air nozzle for injecting hot air, following the nozzle 21. A storage container 23 for storing the slurry 26 is connected to the nozzle 21 via a pipe 24. The pipe 24 is provided with a pump 25 that pumps the slurry from the storage container 23 to the nozzle 21 through the pipe 24. If necessary, an air pump that supplies compressed air to the nozzle 21 is also provided. Below the stage 20 is provided a pan 22 that receives the slurry 26 after being sprayed onto the object to be treated. Since the upper surface of the pan 22 is inclined downward toward the position above the storage container 23, the slurry 26 received by the pan 22 is returned to the storage container 23.

  A suction removal device 27 for removing a metal component by a magnet as described above is provided in the pipe 24 of the wet blast treatment device. That is, for example, by providing the suction removal device 27 as in the first, second, or third example as described above in the middle of the pipe 24, when the slurry 26 flows through the pipe 24, The metal component is removed by the suction removing device 27.

  When performing wet blasting on the molded body 1 (separator A) using this wet blasting apparatus, the slurry 26 is supplied from the storage container 23 to the nozzle 21 through the pipe 24, and the slurry 26 is injected from the nozzle 21. When compressed air is supplied to the nozzle 21 together with the slurry 26, the spray pressure of the slurry 26 from the nozzle 21 increases. The slurry 26 is sprayed from the nozzle 21 onto the molded body 1 (separator A) conveyed by the stage 20, whereby the molded body 1 (separator A) is subjected to wet blasting. The slurry 26 is returned to the storage container 23 through the pan 22 and reused.

  The molded body 1 (separator A) after the wet blasting is further moved in the stage 20, and is washed by spraying warm water such as ion-exchanged water from the fountain nozzle onto the molded body 1 (separator A). Is removed and further heated and dried by spraying warm air.

  In this wet blasting process, when the slurry 26 passes through the pipe 24, the metal component adhering to the abrasive grains is removed by the suction removing device 27. Thereby, a wet blast process can be performed using this abrasive grain, removing a metal component from an abrasive grain with a magnet.

  In the wet blasting apparatus, the suction removing apparatus 27 may be provided at an appropriate position in the circulation path of the slurry 26 in addition to the pipe 24 as described above.

  Further, in the same manner as the method for removing the metal component from the graphite particles, the metal component may be sucked and removed from the molded body 1 (separator A) using a magnet. In this case, for example, by disposing the molded body 1 (separator A) between a pair of magnets, the metal component can be removed by suction from the molded body 1 (separator A). In addition, you may remove a metal component from the molded object 1 (separator A) by appropriate methods other than the suction removal using a magnet. However, the method of cleaning using a strongly acidic solution is not preferable because the resin constituting the separator A may be dissolved, and the ultrasonic cleaning may cause the graphite particles to be detached from the separator A.

  In the separator A obtained as described above, the degree of adhesion of the metal component was determined by washing the separator A with hot water at 90 ° C. for 1 hour and then subjecting the separator A to heat drying at a temperature of 90 ° C. for 1 hour. This can be confirmed by observing the surface of the separator A. When a metal component adheres to the separator A, a metal oxide (rust) is generated on the surface of the separator A by the above treatment. Even if the surface of the separator A after the treatment is visually observed, it is preferable that the presence of the metal oxide (rust) cannot be confirmed. In particular, it is preferable that no metal oxide larger than 100 μm in diameter is present on the surface of the separator A after the treatment, and it is more preferable if no metal oxide larger than 50 μm in diameter exists. Further, it is particularly preferable if there is no metal oxide having a diameter larger than 30 μm.

Moreover, it is preferable that the total amount of Fe, Co, and Ni exposed on the surface of the separator A is 0.010 μg / cm ² or less. Furthermore, it is preferable that the total amount of Cr, Mn, Fe, Co, Ni, Cu and Zn exposed on the surface of the separator A is 0.01 μg / cm ² or less.

  A fuel cell can be manufactured using the separator A manufactured as described above. FIG. 1 shows an example of a polymer electrolyte fuel cell. A membrane-electrode assembly (MEA) 5 comprising an electrolyte 4 such as a solid polymer electrolyte membrane and a gas diffusion electrode (fuel electrode 3a and oxidant electrode 3b) is interposed between the two separators A and A. A single battery (unit cell) is configured. A battery body (cell stack) can be formed by arranging several tens to several hundreds of unit cells.

  FIG. 2 shows an example of the structure of a single cell of a solar battery configured using the gasket 12. This single cell is configured by stacking separators A and A, gaskets 12 and 12 and a membrane-electrode assembly 5. In the separator A, fuel through-holes 13a and 13a and oxidant through-holes 13b and 13b are formed in an outer peripheral portion surrounding a region where the convex portion 1a and the gas supply / discharge groove 2 are formed. Two fuel through holes 13a, 13a are formed, and each fuel through hole 13a, 13a communicates with both ends of the gas supply / discharge groove 2 on the surface of the separator A overlapping the fuel electrode 3a. Two oxidant through holes 13b and 13b are also formed, and each of the oxidant through holes 13b and 13b communicates with both ends of the gas supply / discharge groove 2 on the surface of the separator A overlapping the oxidant electrode 3b. A cooling through hole 13c is also formed in the outer peripheral portion.

  In the present embodiment, as shown in FIG. 2, the separator A is formed with a straight type gas supply / discharge groove 2. In general, the gas supply / discharge grooves 2 in the separator A include a serpentine type groove having a bend and a straight type groove having no bend. Of course, in the separator A shown in FIG. 2, a serpentine type gas supply / discharge groove 2 may be formed in the separator A.

  A gasket 12 for sealing is laminated on the outer peripheral portion of the separator A. The gasket 12 has an opening 15 for accommodating the fuel electrode 3a and the oxidant electrode 3b in the membrane-electrode assembly 5 at a substantially central portion thereof, and the gas supply / discharge groove 2 of the separator A is exposed in the opening 15. To do. On the outer peripheral side of the opening 15, the fuel through-hole 14 a, the oxidant through-hole 14 b, and the cooling are located at positions that coincide with the fuel through-hole 13 a, oxidant through-hole 13 b, and cooling through-hole 13 c of the separator. Each through hole 14c is formed.

  Further, the fuel through-hole 16a, the outer peripheral portion of the electrolyte 4 in the membrane-electrode assembly 5 is also located at a position matching the fuel through-hole 13a, the oxidant through-hole 13b, and the cooling through-hole 13c of the separator. An oxidizing agent through hole 16b and a cooling through hole 16c are formed.

  In this single cell structure, each fuel through-hole 13a. By communicating 14a and 16a, the fuel flow path for the supply and discharge of the fuel to the fuel electrode is configured. In addition, the oxidant flow paths for supplying and discharging the oxidant to and from the oxidant electrode are configured by communicating the oxidant through holes 13b, 14b, and 16b. In addition, the cooling through holes 13c, 14c, and 16c communicate with each other to form a cooling flow path through which cooling water and the like flow.

  In such a single cell structure of a fuel cell, the fuel electrode 3a, the oxidant electrode 3b, and the electrolyte 4 are formed of a known material corresponding to the type of the fuel cell. In the case of a polymer electrolyte fuel cell, the fuel electrode 3a and the oxidant electrode 3b are configured by supporting a catalyst on a base material such as carbon cloth, carbon paper, carbon felt or the like. Examples of the catalyst in the fuel electrode 3a include a platinum catalyst, a platinum / ruthenium catalyst, and a cobalt catalyst. Examples of the catalyst in the oxidant electrode 3b 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.

  The gasket 12 is, 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). ), A rubber material selected from chloroprene rubber, acrylic rubber, fluorine rubber, and the like. This rubber material may contain a tackifier.

  When laminating the gasket 12 on the separator A, for example, the gasket 12 formed in a sheet shape or a plate shape in advance can be bonded or bonded to the separator A. The gasket 12 can be laminated on the separator A by molding a material for forming the gasket 12 on the surface of the separator A. For example, an unvulcanized rubber material is applied to a predetermined position on the surface of the separator A by screen printing or the like, and a coating film of this rubber material is vulcanized to form a desired shape on the surface of the separator A. A gasket 12 can 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 12 can be easily laminated even on the thin separator A. Further, the separator A is set in a mold, an unvulcanized rubber material is injected into a predetermined position on the surface of the separator A, and the rubber material is heated and vulcanized to vulcanize the separator A. It is also possible to form a gasket 12 having a desired shape at a predetermined position on the surface. Thus, when forming the gasket 12 by metal mold | die shaping | molding, compression molding, injection molding, etc. can be employ | adopted besides transfer molding.

  FIG. 3 shows an example of a fuel cell C (cell stack) composed of a plurality of single cells. The fuel cell C communicates with a fuel supply port 17a and a discharge port 17b communicating with the fuel flow channel, an oxidant supply port 18a and a discharge port 18b communicating with the oxidant flow channel, and a cooling flow channel. A cooling water supply port 19a and a discharge port 19b.

  In such a fuel cell C, since the metal component is removed from the raw material component, the molding composition, or the separator A when the separator A is manufactured, the content of the metal component in the separator A is small. Therefore, even if the separator A is washed with water and then incorporated into the fuel cell C, metal oxide (rust) hardly appears on the surface of the separator A. For this reason, the desorption of metal ions from the separator A in the fuel cell C is suppressed, and the decrease in proton conductivity of the electrolyte 4 and the decomposition of the electrolyte 4 due to the desorption of such metal ions are suppressed. The performance of C is maintained for a long time.

  As described above, the content of the metal component in the separator A is sufficiently and surely reduced, and metal oxide (rust) is prevented from appearing on the surface of the separator A, so that the separator C in the fuel cell C The desorption of metal ions can be suppressed. It is possible to suppress the decrease in proton conductivity of the electrolyte and the decomposition of the electrolyte due to the desorption of the metal ions. For this reason, the performance of the fuel cell C can be maintained over a long period of time.

  Examples of the present invention will be described below. In addition, this invention is not limited to this Example.

[Examples 1-15, Comparative Examples 1-2]
For each Example and Comparative Example, the raw material components shown in Table 1 were placed in a stirring mixer (“5XDMV-rr type” manufactured by Dalton) so as to have the composition shown in Table 1, and mixed by stirring. The resulting mixture was prepared. It grind | pulverized to the particle size of 500 micrometers or less with the granulator.

  The obtained pulverized product was compression molded under the conditions of a mold temperature of 185 ° C., a molding pressure of 35.3 MPa, and a molding time of 2 minutes. Next, the pressure was released while the mold was closed, and after holding for 30 seconds, the mold was opened and the separator A was taken out.

  The shape of the obtained separator A was 200 mm × 250 mm and the thickness was 1.5 mm. One surface of the molded body 1 has 57 gas supply / discharge grooves 2 having a length of 250 mm, a width of 1 mm, and a depth of 0.5 mm, and the other surface is a gas having a length of 250 mm, a width of 0.5 mm, and a depth of 0.5 mm. 58 supply / discharge grooves 2 were formed.

  The surface of the separator A is subjected to a blasting process using a slurry containing alumina particles as abrasive grains using a wet blasting apparatus (model PFE-300T / N) manufactured by Macau Corporation, and then washed with ion-exchanged water. Further, it was dried with warm air. Table 1 shows the results of measuring the arithmetic average height Ra (JIS B0601: 2001) of the surface of the separator A after the blast treatment.

  Table 1 shows the metal component removal method and the removal target performed in each Example and Comparative Example. The removal of metal components is not performed on objects for which no method is indicated. In addition, among the raw material components shown in Table 1, the other raw material components refer to all raw material components excluding graphite particles and resin components.

  Moreover, the removal method of the metal component shown in Table 1 is as follows.

(Method 1)
An electromagnet with a magnetic force of 20000 gauss arranged across the passage through which the object passes, using a strong magnetic field type magnetic metal foreign matter removing device (trade name Stomag) manufactured by GS Co., Ltd. The metal component was removed by suction from the material. The processing speed was 10 kg per hour.

(Method 2)
A magnet-system / automatic cleaning made by Seiho Co., Ltd. Using a clean flow magnet (model SECC320001), a rod-shaped neodymium rare earth magnet with a magnetic force of 12,000 gauss arranged in two stages in a lattice shape, Alternatively, the metal component was removed by suction from the molding material. The processing speed was 10 kg per hour.

(Method 3)
The object (graphite particles) was washed with aqua regia in which 69% by mass of concentrated nitric acid and 36% by mass of concentrated hydrochloric acid were mixed at a volume ratio of 1: 3.

(Method 4)
The object (graphite particles) was washed with 15% by mass of nitric acid to remove the metal component.

(Method 5)
In the wet blasting treatment of the separator A, a neodymium rare earth magnet having a magnetic force of 12,000 gauss was disposed across the slurry piping 24 in the wet blasting treatment apparatus, and the metal component was attracted and removed from the abrasive grains.

(Method 6)
In the wet blasting process of the separator A, an electromagnet having a magnetic force of 20000 Gauss was disposed across the slurry pipe 24 in the wet blasting apparatus, and the metal component was attracted and removed from the slurry.

[Metal component amount evaluation]
The finally obtained separator A was washed with warm water of 90 ° C. for 1 hour and then subjected to a heat drying treatment at 90 ° C. for 1 hour, and then the surface of the separator A was visually observed. As a result, the case where the metal oxide (rust) was not recognized on the surface of the separator A was evaluated as “good”, and the case where it was recognized as “bad”.

  Further, the separator A after this treatment was observed with a microscope. For each example and comparative example, both sides of 200 separators A were observed. Based on the results, the amount of metal components was evaluated by the total number of metal oxides (rust) having a diameter of more than 50 μm and not more than 100 μm and the total number of metal oxides (rust) having a diameter of more than 100 μm in 200 separators A. .

  The results are shown in Table 1.

[Evaluation of fuel cell electromotive voltage fluctuation]
A catalyst powder (manufactured by Takanaka Tanaka, Pt / C standard product) carrying platinum particles having an average particle diameter of about 3 nm was prepared on acetylene black powder. In addition, content of the platinum particle in this catalyst powder was 25 mass%. After the catalyst powder was dispersed in isopropanol, this dispersion solution and a dispersion solution in which perfluorocarbonsulfonic acid powder was dispersed in ethanol were mixed to prepare a catalyst paste.

  Separately, after impregnating a carbon nonwoven fabric (manufactured by Toray, TGP-H-120) having a size of 14 cm × 14 cm in plan view and a thickness of 360 μm into an aqueous dispersion containing fluororesin (manufactured by Daikin Industries, Neoflon ND1), It dried and heated at 400 degreeC for 30 minute (s), and produced the water-repellent carbon paper used as a diffused layer.

Subsequently, the catalyst paste described above was applied on one side of the carbon paper by a screen printing method to form a catalyst layer, and a pair of electrodes in which the catalyst layer and the carbon paper were laminated were produced. A part of the catalyst layer was embedded in carbon paper. The amount of the platinum particles were exposed on the catalyst layer surface and perfluorocarbon sulfonic acid was respectively 0.6 mg / cm ² and 1.2 mg / cm ^2.

  As a polymer electrolyte membrane, a perfluorocarbon sulfonic acid membrane (manufactured by Japan Coretex, outer dimensions 15 cm × 15 cm, thickness 30 μm) was prepared separately, and the above-described pair of electrodes were stacked on both sides of the polymer electrolyte membrane. The pair of electrodes was arranged such that carbon paper (diffusion layer) was arranged on the outer surface side. These were joined by hot pressing to obtain a membrane-electrode assembly 5.

The outer circumference on the separator A obtained in each of the examples and comparative examples (the separator A on which the metal oxide is adhered when there is a separator A on which the metal oxide is adhered in the metal component amount evaluation) After applying ethylene-propylene-diene rubber to the portion by screen printing, the gasket 12 was formed by heat vulcanization. The separator A was overlapped on both sides of the membrane-electrode assembly 5 to prepare a fuel cell C composed of a standard single cell (electrode area 25 cm ² ) of the Japan Automobile Research Institute.

  The fuel cell C is supplied with air as a fuel gas at a flow rate of 2.0 NL / min and hydrogen as an oxidant gas at a flow rate of 0.5 NL / min with an external circuit connected to the fuel cell C. C was operated continuously for 1000 hours. The state of fluctuation with time of the electromotive voltage (V) during the operation of the fuel cell C was investigated. The result was expressed as a percentage of the electromotive voltage after the fluctuation with respect to the initial value ((E1 / E0) × 100 (%)). E1 is the electromotive voltage after fluctuation, and E0 is the initial electromotive voltage.

Details of each component in the table are as follows <Composition>
Epoxy resin A: Cresol novolak type epoxy resin (“EOCN-1020-75” manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 199, melting point 75 ° C.)
-Epoxy resin B: Bisphenol F type epoxy resin ("830CRP" manufactured by Dainippon Ink & Chemicals, Inc., epoxy equivalent 171, liquid at 25 ° C)
Curing agent A: Novolac type phenolic resin ("PSM6200" manufactured by Gunei Chemical Co., OH equivalent 105)
Curing agent B: polyfunctional phenol resin (Maywa Kasei Co., Ltd. "MEH-7500", OH equivalent 100)
Phenol resin A: resol type phenol resin (“Sample A” manufactured by Gunei Chemical Co., Ltd., melting point 75 ° C., ortho-ortho 25-35% by 13C-NMR analysis, ortho-para 60-70%, para-para 5 10%)
・ 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 ESC Corporation, average particle size 100 μm, ash content 0.05%, sodium ion 3 ppm, chloride ion 1 ppm)
Coupling agent: Epoxy silane (“A187” manufactured by Nihon Unicar)
Wax A: natural carnauba wax (“H1-100” manufactured by Dainichi Chemical Co., Ltd., melting point: 83 ° C.)
Wax B: Montanic acid bisamide ("J-900" manufactured by Dainichi Chemical Co., Ltd., melting point: 123 ° C)

A Fuel cell separator (separator)
C Fuel cell

Claims (9)

After preparing a molding composition by blending raw material components including graphite particles and a resin component, including a step of molding this molding composition,
A method for producing a fuel cell separator, comprising removing a metal component from the molding composition before molding the molding composition.   2. The method for producing a fuel cell separator according to claim 1, wherein the method for removing the metal component from the molding composition is suction removal using a magnet.   3. The method for producing a fuel cell separator according to claim 1, wherein at least a metal component is removed from at least graphite particles among the raw material components before preparing the molding composition.   4. The method for producing a fuel cell separator according to claim 3, wherein metal components are previously removed from all raw material components before preparing the molding composition.   The method for producing a fuel cell separator according to claim 3 or 4, wherein the method for removing the metal component from the raw material component is suction removal using a magnet. After preparing a molding composition by blending raw material components including graphite particles and a resin component, including a step of molding this molding composition,
A method for producing a fuel cell separator, wherein metal components are previously removed from all raw material components before preparing the molding composition.   After forming the molding composition to obtain a molded body, the molded body is subjected to wet blasting while removing metal components from the slurry containing abrasive grains used in the wet blasting with a magnet. A method for producing a fuel cell separator according to any one of claims 1 to 6.   By removing the metal component, the amount of the metal component in the fuel cell separator is washed with hot water at 90 ° C. for 1 hour, and then heated and dried at 90 ° C. for 1 hour. The method for producing a fuel cell separator according to any one of claims 1 to 7, wherein a metal oxide having a diameter of more than 100 µm does not exist on the surface of the fuel cell separator.   A fuel cell comprising the fuel cell separator produced by the method according to claim 1.

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