WO2011092885A1 - Method for producing fuel cell separator, and fuel cell - Google Patents

Abstract

Disclosed is a method for producing a fuel cell separator that is suppressed in release of metal ions therefrom, thereby being capable of suppressing decrease in the proton conductivity of the electrolyte and decomposition of the electrolyte due to the release of metal ions from the fuel cell separator. Specifically disclosed is a method for producing a fuel cell separator, which comprises a step wherein a molding composition is prepared by blending staring material components containing graphite particles and a resin component, and then the molding composition is molded. Before molding the molding composition, the metal component is removed from the molding composition. By removing the metal component from the entirety of the molding composition, the amount of metal components contained in a fuel cell separator can be reduced.

Description

Manufacturing method of fuel cell separator and fuel cell

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.

Generally, a fuel cell is composed of a cell stack composed of several tens to several hundreds of unit cells 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.

1A and 1B show an example of a polymer electrolyte fuel cell. Between the two fuel cell separators 40, 40 having a plurality of convex portions (ribs) 33 formed on the left and right side surfaces, an electrolyte 4 (solid polymer electrolyte membrane) and a gas diffusion electrode (fuel electrode 31 and oxidation) A single battery (unit cell) is configured by interposing a membrane-electrode assembly (MEA) 5 composed of the agent electrode 32). A battery body (cell stack) is formed by arranging several tens to several hundreds of unit cells. Between the adjacent convex portions 33 in the fuel cell separator 40, a gas supply / discharge groove 2 is formed which is a flow path for hydrogen gas as fuel and oxygen gas as oxidant.

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 mounting on a car, and in the case of mounting on a laptop computer. 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 40 has a unique gas supply / discharge groove 2 on one or both sides of a thin plate-like body as shown in FIGS. 1A and 1B. And has a function of separating the fuel gas, oxidant gas and cooling water flowing in the fuel cell so that they do not mix, and transmits the electric energy generated by the fuel cell to the outside, or the fuel cell It plays an important role of dissipating the heat generated in the outside.

The fuel cell separator 40 is formed of 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 40, the metal ions are diffused 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 40 may be washed with water in the manufacturing process. In such a case, if the fuel cell separator 40 contains a metal component, a metal oxide (rust) is formed on the surface of the fuel cell separator 40. 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 40 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.

However, even with the method described in Patent Document 1, it is difficult to sufficiently reduce the metal content in the fuel cell separator 40, 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.

Japanese Patent Application Publication No. 2006-155936

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.

Another object of the present invention is to provide a fuel cell including a fuel cell separator manufactured by the method for manufacturing a 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, it is preferable that the method for removing the metal component from the molding composition is suction removal using a magnet.

In the first invention, before preparing the molding composition, it is preferable to previously remove at least the metal component from the graphite particles among the raw material components.

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

In the first invention, it is preferable that the method of removing the metal component from the raw material component is 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 is characterized by including a fuel cell separator manufactured according to the first and second inventions.

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

1 is a schematic perspective view of a unit cell of a fuel cell, showing an example of an embodiment of the present invention. FIG. 1B is a schematic perspective view showing a fuel cell separator in the unit cell shown in FIG. 1A. 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. It is a schematic sectional drawing which shows the 1st example of the suction removal apparatus used in embodiment of this invention. It is a schematic sectional drawing which shows the 2nd example of the suction removal apparatus used in embodiment of this invention. It is a schematic sectional drawing which shows the 3rd example of the suction removal apparatus used in embodiment of this invention. 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.

Hereinafter, embodiments of the invention will be described.

The molding composition for producing the fuel cell separator 40 (hereinafter referred to as the separator 40) 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 40 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 in a solid form, 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 40 can be highly filled with graphite particles while maintaining good moldability of the molding 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 novolac 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 the ortho-cresol novolac type epoxy resin is an essential component, the molding composition has excellent moldability, and the separator 40 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 40, and reducing the manufacturing cost. A range of 50 to 70% by mass is particularly preferable.

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 is further reduced, and the toughness is improved when the thinner separator 40 is obtained.

Particularly when a bisphenol F type epoxy resin is used, the viscosity of the molding composition is 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.

Further, when a biphenyl type epoxy resin is used, since the biphenyl type resin has a low melt viscosity, the fluidity of the molding composition is remarkably improved, and the thin moldability of the molding composition 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.

Moreover, when a phenol aralkyl type epoxy resin having a biphenylene skeleton is used, the strength and toughness of the separator 40 are improved, and the hygroscopicity of the separator 40 is further reduced. For this reason, the mechanical characteristics, conductivity, and stability of the characteristics during long-term use of the separator 40 are excellent. In this case, the proportion of the phenol aralkyl type epoxy resin having a biphenylene skeleton in the epoxy resin component 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 a 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. A polyimide resin is also suitable as the thermosetting resin in that it contributes to improving the heat resistance and acid resistance of the separator 40. As such a polyimide resin, bismaleimide resin is particularly preferable, and as this bismaleimide resin, for example, 4,4-diaminodiphenyl bismaleimide can be mentioned. By using the polyimide resin in combination, the heat resistance of the separator 40 is further increased.

When a thermosetting phenol resin is used, 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 is suppressed. It is also preferable to use a resol type phenol resin, for example, a resol type phenol having a structure of ortho-ortho 25-35%, ortho-para 60-70%, para-para 5-10% by 13C-NMR analysis. A resin is preferably used. The resol resin is usually liquid, but the softening point of the resol type phenol resin is easily adjusted, and a resol type phenol resin having a melting point of 70 to 90 ° C. can be easily obtained. 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 handling property of the molding composition may be deteriorated.

Further, other resins other than the epoxy resin and the thermosetting phenol resin may be used in combination. 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.

When an epoxy resin is used, the molding composition contains a curing agent as an essential component, and this curing agent contains 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 other hardening | curing agents other than a phenol type compound are used together, it is preferable that another hardening | curing agent is a non-amine type compound, In this case, while the electrical conductivity of the separator 40 is maintained in the high state, The poisoning of the catalyst of the fuel cell is suppressed. It is also preferred that no acid anhydride compound is used as the 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 40 or increasing the elution of impurities from the separator 40. There is a risk that.

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

Further, the graphite particles are used to reduce the electrical specific resistance of the molded separator 40 and improve the conductivity of the separator 40. The graphite particle content 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 40 is provided with sufficiently excellent conductivity. Further, when this ratio is 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 40.

Any graphite particles can be used as long as they exhibit high conductivity. For example, graphite particles obtained by graphitizing carbonaceous materials such as mesocarbon microbeads, coal-based cokes, and petroleum-based cokes are graphitized. In addition to the graphite particles obtained in this manner, suitable graphite particles such as graphite electrode, special carbon material processed powder, natural graphite, quiche graphite, expanded graphite and the like are used. Only one kind of such graphite particles may be used, or a plurality of kinds may be used in combination.

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.

In addition, it is preferable that the graphite particles are purified regardless of whether they are natural graphite powder or artificial graphite powder. In this case, since there are few ash and ionic impurities in the graphite particles, The elution of impurities from a certain separator 40 is suppressed.

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 40 may be deteriorated.

The average particle size of the graphite particles is preferably in the range of 15 to 100 μm. 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 40 is improved. In order to particularly improve the moldability, the average particle size is preferably 30 μm or more. Further, the surface smoothness of the separator 401 is particularly improved, and the arithmetic average height Ra (JIS) of the surface of the separator 40 is 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.

Further, when obtaining a thin separator 40 in particular, 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 40 from being anisotropic and to prevent deformation such as warpage.

Regarding the reduction of the anisotropy of the separator 40, the ratio of the contact resistance between the flow direction of the molding composition at the time of molding in the separator 40 and the direction orthogonal to the flow direction is 2 or less. It is preferable.

Further, as the graphite particles, it is also preferable to use graphite particles having two or more kinds of particle size distributions, that is, graphite particles obtained by mixing two or more kinds of particles having different average particle diameters. In this case, it is particularly preferable to mix graphite particles having an average particle diameter of 1 to 50 μm and graphite particles having an average particle diameter of 30 to 100 μm. When graphite particles having such a particle size distribution are used, it is expected that particles having a large particle size have a small surface area, so that they can be kneaded even with a small amount of resin. While improving the contact between each other, it is expected to increase the strength of the molded product, thereby improving the performance such as the density of the separator 40, the conductivity, the gas impermeability, the strength, etc. Can be achieved. 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 appropriately adjusted. In particular, the mixing mass ratio of the former to the latter is 40:60 to 90:10, particularly 65:35. It is preferably ~ 85: 15.

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.).

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

As a curing catalyst (curing accelerator), an appropriate one can be contained, but a non-amine compound should be used so as not to contain a primary amine and a secondary amine in the composition. Is preferred. 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. The use of a substituted imidazole having a group is preferable in that the storage stability of the molding composition is improved. In particular, when the thin separator 40 is obtained, the volatility when forming the sheet-like separator 40 from the molding composition prepared in a varnish shape, the smoothness of the separator 40, and the like are improved. As this substituted imidazole, a substituted imidazole having a hydrocarbon group having 6 to 17 carbon atoms in the 2-position is preferably used, and specific examples thereof include 2-undecylimidazole, 2-heptadecylimidazole, 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. Further, a phosphorus compound and the substituted imidazole may be used in combination. An example of a phosphorus compound is triphenylphosphine. When such a phosphorus compound is used, elution of chlorine ions from the separator 40 which is a molded product is 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 that no aminosilane is used because the molding composition does not contain a primary amine and a secondary amine. The use of aminosilane is not preferred because it may poison the fuel cell catalyst. Further, it is preferable that mercaptosilane is not used as the coupling agent. Similarly, when this mercaptosilane is used, the fuel cell catalyst may be poisoned.

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 epoxy silane coupling agent is used, the amount used is preferably in the range where the content in the solid content of the molding composition is 0.5 to 1.5% by mass. In this range, the coupling agent is sufficiently suppressed from bleeding on the surface of the separator 40.

The coupling agent may be previously adhered to the surface of the graphite particles by spraying or the like. The addition amount 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 of is in the range of 0.5 to 2 times the total amount of the surface area of the graphite particles. In this range, bleeding of the coupling agent to the surface of the separator 40 is sufficiently suppressed, and contamination of the mold surface is suppressed.

As the wax (internal mold release agent), an appropriate one is used, but particularly at 120 to 190 ° C., 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 mold 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 40, the groove depth, the ease of releasability from the mold surface such as the draft angle, etc., but the molding composition The content is preferably 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 releasability is exhibited at the time of mold molding. When the content is 2.5% by mass or less, the hydrophilicity of the separator 40 is sufficiently inhibited by the wax. The wax content 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 the thin separator 40 is obtained, the molding composition may be prepared in a liquid form (including varnish and slurry) by containing a solvent. As the solvent, for example, polar solvents such as methyl ethyl ketone, methoxypropanol, N, N-dimethylformamide, dimethyl sulfoxide are preferable. Further, only one type of solvent may be used, or two or more types may be used in combination. The amount of the solvent used is appropriately set in consideration of the moldability when the sheet-like separator 40 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, a solvent should just be used as needed, and a solvent does not need to be used if a molding composition is prepared in a liquid state by using liquid resin as a thermosetting resin.

Further, the content of ionic impurities in the separator 40 is preferably a sodium content of 5 ppm or less and a chlorine content of 5 ppm or less in terms of mass ratio with respect to the total amount of the molding composition. It is preferable that the content of the ionic impurities in the molding composition is adjusted so 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. In this case, elution of ionic impurities from the separator 40 is suppressed, and deterioration of characteristics such as a decrease in starting voltage of the fuel cell due to the elution of impurities is suppressed.

In order to reduce the content of ionic impurities in the separator 40 and the molding composition as described above, each component 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.

The content of ionic impurities is derived based on the amount of ionic impurities in the extracted water of the object. The extracted water is obtained by charging the object in 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. In addition, ionic impurities in the extracted water are evaluated by ion chromatography. Then, based on the derived ionic impurity amount in the extracted water, the amount of the ionic impurity in the object is derived in terms of a mass ratio with respect to the object.

Further, the molding composition is preferably prepared such that the TOC (total organic carbon) of the separator 40 formed from this composition is 100 ppm or less.

The TOC is a numerical value measured using an aqueous solution after the separator 40 is charged into ion-exchanged water at a rate of 100 ml of ion-exchanged water with respect to 10 g of the mass of the separator 40 and treated at 90 ° C. for 50 hours. . This TOC is measured by, for example, a total organic carbon analyzer “TOC-50” manufactured by Shimadzu 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 the organic substance contained indirectly is measured. Inorganic carbon (IC) and total carbon (TC) in the sample are measured, and total organic carbon (TOC) is measured from the difference between the total carbon and inorganic carbon (TC-IC).

When the above TOC is 100 ppm or less, characteristic deterioration as a fuel cell is further suppressed.

The value of TOC is reduced by selecting a high-purity component as each component constituting the molding composition, adjusting the equivalent ratio of the resin, or performing a post-curing process during molding.

A molding composition is prepared by blending the raw material components as described above, and the separator 40 is obtained by molding the molding composition. Thus, when the separator 40 is manufactured, the metal component is removed from at least one of the raw material component, the molding composition, and the separator 40. In particular, at least the metal component is preferably removed from the molding composition. Thereby, the content of the metal component of the fuel cell separator is reduced.

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

In particular, it is preferable that the metal component is removed in advance from all raw material components. In this case, the metal component is removed from all the raw material components in advance, so that the content of the metal component in the fuel cell separator is further reliably reduced.

When the metal component is previously removed from the raw material component, the raw material component is adjusted so that the total content of Fe, Co, and Ni in the raw material component is preferably 1 mass ppm or less, more preferably 0.5 mass ppm or less. The metal component is removed from 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. Is removed.

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

An example of a method for removing the metal component from the raw material component is a method of removing the metal component in the raw material component by suction using a magnet. In this case, the metal component is sufficiently removed from the raw material component, and the content of the magnetic substance is particularly reduced. As the magnet, a permanent magnet, an electromagnet, or the like 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 is 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. It is preferable. However, since the magnetic force (magnetic flux density) of a normal neodymium-based rare earth magnet is up to 12000 gauss, or up to about 14000 gauss, the magnetic force (magnetic flux density) when a normal neodymium-based rare earth magnet is used is 12000 gauss. 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 a device for sucking and removing a metal component from a raw material component using a magnet (hereinafter referred to as a suction removing device 27), an object (here, the raw material component) passes as shown in FIG. 4A. An apparatus in which magnets 29 are arranged on both sides of the passage 28 is provided. 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 the slurry in which the object is dispersed passes through the passage 28 between the magnets 29 in the suction removal device 27, particularly the magnetic material among the metal components in the object is attracted by the magnet 29. 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 the object or slurry in which the object is dispersed passes through the passage 28 between the magnets 29 in the suction removal device 27 (see the arrow indicated by reference numeral 60 in the figure), the metal component in the object is removed. Of these, the magnetic substance is removed by adsorbing on 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 in which the object passes through 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 slurry in which the object is dispersed passes through the passage 28 in the suction removal device 27 (see the arrow indicated by reference numeral 60 in the figure), among the metal components in the object, particularly magnetic The body 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, on the inner side of 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 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).

Further, a plurality of magnets may be provided inside the cylindrical body 30 so as to be arranged along the peripheral surface of the cylindrical body 30. In this case, for example, a plurality of magnets (first magnets) having magnetic poles arranged in the radial direction of the cylindrical body 30 are arranged at intervals. The first magnets are arranged so that the directions of the magnetic poles are alternately reversed. A plurality of magnets (second magnets) having magnetic poles arranged in the circumferential direction of the cylindrical body 30 are arranged between the first magnets. This second magnet also has the magnetic poles arranged alternately in opposite directions. Alternatively, a plurality of second 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 falls on the rotating cylindrical body 30 (see the arrow indicated by reference numeral 60 in the figure), the object is a rotational force of the cylindrical body 30. (See the arrow indicated by reference numeral 70 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 the arrow indicated by reference numeral 80 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.

Further, 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 that the suction removal device 27 is provided with a shield that shields a path leading to a 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, the metal component is attracted and removed from the raw material component by the magnet, so that the metal component, particularly the magnetic material (Fe, Co, Ni, etc.) is removed from the raw material component, and Fe, Co, and Ni in the raw material component are removed. The content of is particularly reduced.

Further, as a method for removing the metal component from the graphite particles, there is 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 is 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 a metal component is removed 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. The method of doing is mentioned. Other appropriate methods may be employed.

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

After the molding composition is prepared, the metal component is preferably removed from the molding composition. In this case, even if a metal component is mixed when the molding composition is prepared, the metal component can be removed from the molding composition. In this case, the metal component is sufficiently removed from the molding composition, and the content of the magnetic substance is particularly reduced.

When the metal component is removed from the molding composition, the total content of Fe, Co, and Ni in the molding composition is preferably 1 ppm by mass or less, more preferably 0.5 ppm by mass 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. The metal component is removed from the object.

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 with a magnet, it is preferable to use the same suction removal device 27 as that for the raw material component.

In order for the metal component to be removed from the raw material component or the molding composition until the content falls below a predetermined value, the metal component is removed from the raw material component or the molding composition by the method exemplified above. After that, 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 component is measured until the measurement result becomes a predetermined value or less. It is preferred that the removal of the metal component from the composition is repeated.

The molded body 1 (separator 40) is obtained by molding this molding composition. As the molding method, an appropriate method such as injection molding or compression molding is employed. For example, as shown in FIGS. 1A and 1B, the separator 40 is formed with a plurality of convex portions (ribs) 33 on both surfaces, so that hydrogen gas as a fuel is interposed between the adjacent convex portions 33, and A gas supply / discharge groove 2 which is a flow path of oxygen gas which is an oxidizing agent is formed.

The separator 40 includes an anode 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 40 having gas supply / discharge grooves 2 on both sides as shown in FIGS. 1A and 1B 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, a gasket is preferably interposed between the anode side separator and the cathode side separator.

When the thin separator 40 is obtained from the molding composition prepared in a varnish shape, the molding composition is first molded into a sheet shape to obtain a fuel cell separator molding sheet (molding sheet). It is done. 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. The casting method using such a plurality of types of film thickness adjusting means is realized by using, for example, a multi-coater that has already been put into practical use. As the film thickness adjusting means for casting, it is preferable to use at least one of a doctor knife and a wire bar, that is, one or both of them together with a slit die. 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, when the thickness of the molding sheet is 0.5 mm or less, a reduction in thickness and weight of the separator 1 and a reduction in cost are achieved. In particular, if the thickness is 0.3 mm or less, a solvent is used. In this case, the remaining of the solvent inside the molding sheet is effectively suppressed. Further, when this thickness is less than 0.05 mm, the advantage in manufacturing the separator 40 is not sufficiently exhibited, and this thickness is preferably 0.1 mm or more in consideration of moldability.

This molding sheet is made into a semi-cured (B stage) state by drying accompanying casting, and this is subjected to compression / thermosetting molding to form a plurality of convex portions (ribs) 33 on both sides and The separator 40 is obtained by forming the gas supply / discharge groove 2 between the convex portions (ribs) 33. At this time, when the separator 40 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 33 on the one surface side, a plurality of convex portions are formed on both surfaces while being thin. The separator 40 having the (rib) 33 and the gas supply / discharge groove 2 between the convex portions (rib) 33 is obtained.

In the compression / thermosetting molding of the molding sheet, the molding sheet is first cut (cut) or punched into a predetermined plane dimension as necessary, and is thermoset by a compression molding machine in the mold. The compression / thermosetting molding conditions 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 that

In producing the separator 40, the separator 40 may be produced by molding a single molding sheet, or the separator 40 may be produced by molding a plurality of molding sheets. .

By forming the molding sheet in this way, a thin separator 40, particularly a separator 40 having a thickness in the range of 0.2 to 1.0 mm can be manufactured. As described above, the use of the molding sheet at the time of manufacturing the separator 40 makes it easy for the molding material to be thinly and uniformly arranged and molded even when the thin separator 40 is manufactured. Increases accuracy.

Note that when the separator 40 is manufactured, a molding sheet and an appropriate conductive base material may be laminated and molded. When the conductive substrate is used in this way, the mechanical strength of the separator 40 is improved. When a conductive substrate is used, compression and 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, Alternatively, 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.

It is preferable that the skin layer of the surface layer of the molded body 1 is removed and the surface roughness of the separator 40 is adjusted by blasting the molded body 1 (separator 40).

The arithmetic average height Ra (JIS B0601: 2001) of the surface of the separator 40 is preferably in the range of 0.4 to 1.6 μm. In this case, gas leakage at the joint between the separator 40 and the gasket 12 is suppressed. For this reason, it is not necessary to mask the part joined to the gasket 12 in the separator 40 during the wet blasting process, and the production efficiency of the separator 40 is improved. Note that it is difficult for the arithmetic average height Ra to be 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 40 is particularly preferably 1.2 μm or less. Further, when the arithmetic average height Ra of the surface of the separator 40 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 reduced as the separator 40 is thinned, Gas leak is sufficiently suppressed. It is also preferable that the arithmetic average height Ra of the surface of the separator 40 is 0.6 μm or more.

Further, the contact resistance on the surface of the separator 40 is preferably 15 mΩcm ² or less. In this case, the function of the separator 40 for transmitting the electric energy generated by the fuel cell to the outside is maintained at a high level.

In the blasting process, it is preferable that the molded body 1 (separator 40) is subjected to a wet blasting process, and in this process, 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 a slurry containing such a metal component is used and blasting is performed, the metal component is driven from the abrasive grains onto the surface of the separator 40. However, if the abrasive grains are used and wet blasting is performed while removing the metal components from the slurry with a magnet as described above, adhesion of the metal components to the separator 40 during blasting is suppressed. That is, while the removal of the skin layer and the adjustment of the surface roughness are performed by the wet blasting process, metal components such as metal foreign matters contained in the abrasive grains in the slurry may be driven into the separator 40 during the wet blasting process. It is suppressed.

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 40) 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.

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

When wet blasting is performed on the molded body 1 (separator 40) by 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 supplied from the nozzle 21 to the nozzle 21. Be injected. Note that when compressed air is supplied to the nozzle 21 together with the slurry 26, the injection 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 40) conveyed by the stage 20, whereby the molded body 1 (separator 40) 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 40) after the wet blasting further moves 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 40). 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, wet blasting is performed using the abrasive grains while removing metal components from the abrasive grains with a magnet.

In the wet blast treatment apparatus, the suction removal 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.

Furthermore, 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 40) with a magnet. In this case, the metal component is attracted and removed from the molded body 1 (separator 40) by, for example, arranging the molded body 1 (separator 40) between the pair of magnets. In addition, a metal component may be removed from the molded object 1 (separator 40) 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 40 may be dissolved, and the ultrasonic cleaning may cause the graphite particles to be detached from the separator 40.

In the separator 40 obtained as described above, the degree of adhesion of the metal component was determined by washing the separator 40 with hot water at 90 ° C. for 1 hour and then subjecting the separator 40 to heat drying at 90 ° C. for 1 hour. This is confirmed by observing the surface of the separator 40. When a metal component adheres to the separator 40, a metal oxide (rust) is generated on the surface of the separator 40 by the treatment. Even if the surface of the separator 40 after the treatment is visually observed, it is preferable that the presence of the metal oxide (rust) is not confirmed. In particular, it is preferable that no metal oxide larger than 100 μm in diameter is present on the surface of the separator 40 after the treatment, and it is more preferable if there is no metal oxide larger than 50 μm in diameter. 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 40 is 0.010 μg / cm ² or less. Furthermore, the total amount of Cr, Mn, Fe, Co, Ni, Cu and Zn exposed on the surface of the separator 40 is preferably 0.01 μg / cm ² or less.

A fuel cell can be manufactured using the separator 40 manufactured as described above. FIG. 1A 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 31 and oxidant electrode 32) is interposed between the two separators 40, 40. Thus, a unit cell (unit cell) is configured. A battery body (cell stack) is 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 cell configured by using the gasket 12. This single cell is configured by stacking separators 40 and 40, gaskets 12 and 12, and membrane-electrode assembly 5. In the separator 40, the first fuel through holes 131 and 131 and the first oxidant through holes 132 and 132 are formed on the outer periphery surrounding the region where the convex portion 33 and the gas supply / discharge groove 2 are formed. Is formed. Two first fuel through holes 131 and 131 are formed, and the first fuel through holes 131 and 131 are respectively formed at both ends of the gas supply / discharge groove 2 on the surface overlapping the fuel electrode 31 of the separator 40. Communicate. Two first oxidant through holes 132, 132 are also formed, and each first oxidant through hole 132, 132 is formed in the gas supply / discharge groove 2 on the surface overlapping the oxidant electrode 32 of the separator 40. It communicates with both ends. A first cooling through-hole 133 is also formed in the outer peripheral portion.

In the present embodiment, as shown in FIG. 2, the separator 40 is formed with a straight type gas supply / discharge groove 2. In general, the gas supply / discharge groove 2 in the separator 40 includes a serpentine type groove having a bend and a straight type groove having no bend. Of course, in the separator 40 shown in FIG. 2, the serpentine type gas supply / discharge groove 2 may be formed in the separator 40.

The gasket 12 for sealing is laminated on the outer peripheral portion of the separator 40. The gasket 12 has an opening 15 for accommodating the fuel electrode 31 and the oxidant electrode 32 in the membrane-electrode assembly 5 at substantially the center thereof, and the gas supply / discharge groove 2 of the separator 40 is exposed in the opening 15. To do. On the outer peripheral side of the opening 15, a second fuel-use fuel is provided at a position matching the first fuel through-hole 131, the first oxidant through-hole 132, and the first cooling through-hole 133. A through hole 141, a second oxidant through hole 142, and a second cooling through hole 143 are formed.

Further, the outer peripheral portion of the electrolyte 4 in the membrane-electrode assembly 5 also matches the first fuel through hole 131, the first oxidant through hole 132, and the first cooling through hole 133 of the separator. A third fuel through-hole 161, a third oxidant through-hole 162, and a third cooling through-hole 163 are respectively formed at the positions.

In this single cell structure, the separator 40, the gasket 12, and the first fuel through-hole 131, the second fuel through-hole 141, and the third fuel through-hole 161 of the electrolyte 4 communicate with each other. A fuel flow path for supplying and discharging fuel to and from the electrode is formed. In addition, the first oxidant through-hole 132, the second oxidant through-hole 142, and the third oxidant through-hole 162 communicate with each other to supply and discharge the oxidant to and from the oxidant electrode. An oxidant flow path is formed. The first cooling through-hole 133, the second cooling through-hole 143, and the third cooling through-hole 163 communicate with each other to form a cooling flow path through which cooling water or the like flows.

In such a single cell structure of the fuel cell, the fuel electrode 31, the oxidant electrode 32, 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 31 and the oxidant electrode 32 are configured by carrying 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 31 include a platinum catalyst, a platinum / ruthenium catalyst, and a cobalt catalyst. Examples of the catalyst in the oxidant 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.

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 the gasket 12 is laminated on the separator 40, for example, the gasket 12 previously formed in a sheet shape or a plate shape is bonded to the separator 40 by bonding or fusion. The gasket 12 may be laminated on the separator 40 by molding a material for forming the gasket 12 on the surface of the separator 40. For example, an unvulcanized rubber material is applied to a predetermined position on the surface of the separator 40 by screen printing or the like, and a desired shape is formed on the predetermined position on the surface of the separator 40 by vulcanizing the coating film of the rubber material. The gasket 12 is 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 40. In addition, the separator 40 is set in a mold, an unvulcanized rubber material is injected into a predetermined position on the surface of the separator 40, and the rubber material is heated and vulcanized. The gasket 12 having a desired shape may be formed at a predetermined position on the surface of the separator 40. In this way, when the gasket 12 is formed by die molding, compression molding, injection molding, or the like can be employed in addition to transfer molding.

FIG. 3 shows an example of a fuel cell 50 (cell stack) composed of a plurality of single cells. This fuel cell 50 communicates with a fuel supply port 171 and a discharge port 172 communicating with the fuel flow channel, an oxidant supply port 181 and a discharge port 182 communicating with the oxidant flow channel, and a cooling flow channel. A cooling water supply port 191 and a discharge port 192.

In such a fuel cell 50, since the metal component is removed from the raw material component, the molding composition, or the separator 40 when the separator 40 is manufactured, the content of the metal component in the separator 40 is small. For this reason, even if the separator 40 is washed and then incorporated into the fuel cell 50, metal oxide (rust) hardly appears on the surface of the separator 40. For this reason, the desorption of metal ions from the separator 40 in the fuel cell 50 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. 50 performance is maintained over a long period of time.

As described above, the content of the metal component in the separator 40 is sufficiently and reliably reduced, and the appearance of metal oxide (rust) on the surface of the separator 40 is suppressed, so that the separator C in the fuel cell 50 can be obtained. The desorption of metal ions from is suppressed. As a result, the decrease in proton conductivity of the electrolyte due to the desorption of metal ions and the decomposition of the electrolyte are suppressed. For this reason, the favorable performance of the fuel cell 50 is maintained over a long period of time.

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

[Examples 1 to 15, Comparative Examples 1 and 2]
For each of the examples and comparative examples, 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 40 was taken out.

The shape of the obtained separator 40 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 40 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 40 after the blast treatment.

Table 1 shows the metal component removal methods and removal targets performed in the examples and comparative examples. 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 process of the separator 40, a neodymium rare earth magnet having a magnetic force of 12,000 gauss was disposed across the slurry piping 24 in the wet blasting apparatus, and the metal component was attracted and removed from the abrasive grains.

(Method 6)
In the wet blast treatment of the separator 40, an electromagnet having a magnetic force of 20000 gauss was disposed across the slurry piping 24 in the wet blast treatment apparatus, and metal components were attracted and removed from the slurry.

[Metal component amount evaluation]
The finally obtained separator 40 was washed with warm water at 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 40 was visually observed. As a result, the case where metal oxide (rust) was not recognized on the surface of the separator 40 was evaluated as “good”, and the case where it was recognized as “bad”.

Further, the separator 40 after this treatment was observed with a microscope. For each example and comparative example, both sides of 200 separators 40 were observed. Based on the result, 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 40. .

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%. This catalyst powder was dispersed in isopropanol, and then 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 143 m × 143 m 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, on one side of the carbon paper, the above-described catalyst paste was applied 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 the polymer electrolyte membrane, a perfluorocarbon sulfonic acid membrane (manufactured by Japan Coretex, outer dimensions 15 cm × 15 cm, thickness 30 μm) was separately prepared, 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 composite 5.

The outer periphery on the separator 40 obtained in each of the examples and comparative examples (the separator 40 on which the metal oxide is adhered when there is a separator 40 on which the metal oxide is recognized 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 40 was stacked on both sides of the membrane-electrode assembly 5 to produce a fuel cell 50 composed of a standard single cell (electrode area 25 cm ² ) of the Japan Automobile Research Institute.

The fuel cell 50 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 50. 50 was operated continuously for 1000 hours. The state of variation with time of the electromotive voltage (V) during the operation of the fuel cell 50 was investigated. The result was expressed as a percentage of the electromotive voltage after fluctuation to the initial value ((E1 / E0) × 100 (%)). E1 is an electromotive voltage after fluctuation, and E0 is an initial electromotive voltage.

Details of each component in the table are as follows: 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 to 35% by 13C-NMR analysis, ortho-para 60 to 70%, para-para 5 to 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.)

Claims (9)

1. 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 a metal component is removed 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 of 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 or 2, wherein, before preparing the molding composition, at least a metal component is removed from graphite particles among the raw material components.
4. 4. The method for producing a fuel cell separator according to claim 3, wherein metal components are removed from all raw material components in advance before preparing the molding composition.
5. The method for producing a fuel cell separator according to claim 3 or 4, wherein the method of removing the metal component from the raw material component is suction removal using a magnet.
6. 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.
7. 2. A molded body obtained by molding the molding composition, and then subjected to a wet blasting treatment while removing metal components from a slurry containing abrasive grains used in the wet blasting treatment with a magnet. The manufacturing method of the fuel cell separator as described in any one of thru | or 6.
8. 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 larger than 100 µm does not exist on the surface of the fuel cell separator.
9. A fuel cell comprising a fuel cell separator manufactured by the method according to any one of claims 1 to 8.

Images