JP2011034807A - Manufacturing method of fuel cell separator, and fuel cell separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a fuel cell separator which has a high hydrophilicity applied on the surface of the separator and can maintain this hydrophilicity for a long period, and can maintain a high power generation efficiency of the fuel cell by preventing closure of a gas supply and exhaust groove by water droplet. <P>SOLUTION: A molding composition is formed which contains a thermosetting resin containing epoxy resin, a curing agent containing a phenolic compound, and graphite particles, and in which the equivalent ratio of the epoxy resin to the phenolic compound is 0.8-1.2. A surface treatment is applied on the surface of the molding 1 obtained by burning and spraying a gas containing a reforming agent compound including a silicon compound or an aluminum compound. Since the epoxy resin and phenolic compound are blended in the molding composition and their blending ratio is adjusted, and by this very simple method, a hydroxyl group is distributed in the molding 1, thereby at the time of surface treatment, the silicon compound or the like is easily jointed firmly to the hydroxy group on the surface of the molding 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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, the chemical energy of the reaction is obtained by oxidizing the fuel by electrochemical reaction by supplying fuel to the fuel electrode and supplying the oxidant to the oxidant electrode of the pair of electrodes facing each other through the electrolyte. Direct conversion 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. 2 shows an example of a polymer electrolyte fuel cell. A solid high fuel cell is disposed between two fuel cell separators A and A each having a plurality of convex portions (ribs) 1a formed on both left and right side surfaces. A single cell (unit cell) is formed by interposing the molecular electrolyte membrane 4 and the gas diffusion electrodes (fuel electrode and oxidant electrode) 3 and 3, and several tens to several hundreds of unit cells are arranged in parallel. A battery body (cell stack) is formed. The convex portion 1a constitutes a gas supply / discharge groove 2 which is a flow path for hydrogen gas as a fuel and oxygen gas as an oxidant between adjacent convex portions 1a.

  Such a cell stack is composed of, for example, 50 to 100 unit cells for a stationary type for home use, 400 to 500 unit cells for mounting on a car, and 10 to 10 for a laptop computer. It can be composed of 20 unit cells.

In this polymer electrolyte fuel cell, hydrogen gas, which is a fluid, is supplied to a fuel electrode, and oxygen gas, which is a fluid, is supplied to an oxidizer electrode, thereby extracting current from an 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 4 to the oxidant electrode and reacts with oxygen (O ₂ ) on the oxidant electrode. To produce water (H ₂ O). Therefore, for the operation of the polymer electrolyte fuel cell, it is necessary to supply and discharge the reactive gas and to take out the current.

  In addition, the polymer electrolyte fuel cell is normally assumed to operate in a humid atmosphere in the range of room temperature to 120 ° C., and therefore water is often handled in a liquid state. It is necessary to manage the replenishment of liquid water and discharge the liquid water from the oxidizer electrode.

  Among the components constituting such a fuel cell, the fuel cell separator A includes a plurality of gas supply / discharge grooves on one or both sides of a thin plate-like body as shown in FIGS. 2 (a) and 2 (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.

  In this polymer electrolyte fuel cell, when water droplets generated by the above reaction adhere to the surface of the separator A on the side of the oxidant electrode, the gas supply / discharge groove 2 is closed, and the flow rate of oxygen gas is reduced. There is a problem of flooding that decreases. For this reason, active examination is made in order to discharge efficiently the water adhering to the separator A surface.

  For example, Patent Document 1 proposes improving the wettability of the separator surface by irradiating the surface of the separator with vacuum ultraviolet light from a vacuum ultraviolet light irradiation device, but the productivity is poor and not suitable for practical use. There is a problem.

  Patent Document 2 proposes to form a film of hydrophilic phenol resin or hydrophilic epoxy resin on the separator surface, and Patent Document 3 proposes to form a silane compound having a hydrophilic functional group. In the case of Patent Document 2, the electrical characteristics of the separator may be deteriorated, and in the case of Patent Document 3, the process of forming a silane compound is complicated and is not suitable for practical use.

  Moreover, although patent document 4 proposes forming a separator from a molding material containing a silicon compound, it has a drawback that moldability is lowered.

  In Patent Document 5, the separator is first heated in a heating furnace and then subjected to flame treatment with a flame from a burner to improve the hydrophilicity of the separator. It cannot be sustained.

  Furthermore, Patent Document 6 proposes that a gas containing a silicon compound or the like is sprayed on the separator surface while burning. This method has high processing efficiency, and high hydrophilicity is imparted to the surface of the separator after processing.

  However, even with the method in Patent Document 6, the hydrophilicity of the separator surface deteriorates with time, and the hydrophilicity cannot be maintained for a long time.

JP 2003-142116 A JP 2000-251903 A JP 2007-299754 A JP 2008-186642 A JP 2002-313356 A JP 2006-185729 A

  The present invention has been made in view of the above points, and can impart high hydrophilicity to the surface of the separator and maintain this hydrophilicity for a long period of time, and the gas supply / discharge groove is closed by water droplets. It is an object of the present invention to provide a method of manufacturing a fuel cell separator and a fuel cell separator capable of maintaining the high power generation efficiency of the fuel cell.

  As a result of diligent research, the inventors of the present invention have improved the hydrophilicity by spraying the surface of the fuel cell separator while burning a gas containing a silicon compound or the like. The technique has been found and the present invention has been completed.

  The manufacturing method of the fuel cell separator A according to the present invention includes a thermosetting resin containing an epoxy resin, a curing agent containing a phenolic compound, and graphite particles, and an equivalent ratio of the epoxy resin to the phenolic compound is 0. A surface treatment in which a molding composition in the range of 0.8 to 1.2 is molded and sprayed on the surface of the obtained molded body 1 while burning a gas containing a modifier compound containing a silicon compound or an aluminum compound. It is characterized by giving.

  For this reason, a hydroxyl group can be distributed in the molded object 1 by the very simple method of mix | blending an epoxy resin and a phenolic compound in a molding composition, and adjusting the compounding ratio. Thereby, at the time of surface treatment, it becomes easy for a silicon compound or the like to be firmly bonded to the hydroxyl group on the surface of the molded body 1, and thus the hydrophilicity of the surface of the fuel cell separator A is maintained for a long time.

  Moreover, the manufacturing method of the other fuel cell separator A which concerns on this invention shape | molds the molding composition containing the thermosetting resin containing a thermosetting phenol resin, and a graphite particle, and obtained molded object 1 of A surface treatment is performed on the surface by spraying a gas containing a modifier compound containing a silicon compound or an aluminum compound while burning.

  For this reason, it is possible to distribute hydroxyl groups in the molded body 1 by a very simple method of blending a thermosetting phenol resin as a thermosetting resin in the molding composition. It becomes easy for a silicon compound or the like to be firmly bonded to the hydroxyl group on the surface of 1, and thus the hydrophilicity of the surface of the fuel cell separator A is maintained for a long time.

  In this invention, it is preferable that arithmetic mean height Ra (JIS B0601: 2001) of the surface to which the said surface treatment is given of the said molded object 1 is the range of 0.4-1.6 micrometers. In this case, the treatment efficiency of the surface treatment on the molded body 1 is increased, and the hydrophilicity of the surface of the fuel cell separator A can be further improved and the hydrophilicity can be maintained for a long time.

  In the present invention, the surface treatment is preferably performed after the molded body 1 is subjected to plasma treatment. In this case, a reactive functional group is further introduced into the surface of the molded body 1 by plasma treatment, and a silicon compound or the like is easily bonded to the reactive sensitive group during the surface treatment. The hydrophilicity is further improved and the hydrophilicity can be maintained for a long time.

  In the present invention, the silicon compound is preferably at least one of a silane compound and a silicone compound.

  In this case, the hydrophilicity of the surface of the fuel cell separator A can be particularly improved.

  In the present invention, the modifier compound preferably contains at least one selected from alkylsilane compounds, alkoxysilane compounds, siloxane compounds, silazane compounds, alkylaluminum compounds, and alkoxyaluminum compounds.

  In this case, the hydrophilicity of the surface of the fuel cell separator A can be particularly improved.

  In the present invention, a gas supply / discharge groove 2 having a ratio A / B of width A to depth B of 1 or more is formed on the surface of the molded body 1 on which the surface treatment is performed. preferable. In this case, it is possible to maintain a high processing efficiency of the surface treatment for the molded body 1 while forming a gas supply / discharge groove 2 serving as a gas flow path on the surface of the molded body 1. The hydrophilicity of the resin can be further improved and the hydrophilicity can be maintained for a long time.

In the present invention, the surface treatment is preferably performed so that the contact resistance of the surface-treated surface is 15 mΩcm ² or less. In this case, the hydrophilicity of the fuel cell separator A can be improved, and the function of transmitting electric energy generated by the fuel cell using the fuel cell separator A to the outside can be maintained at a high level.

  Moreover, in this invention, it is preferable to perform the said surface treatment so that the static contact angle with the water of the said surface-treated surface may be in the range of 0-50 degrees.

  In this case, the hydrophilicity of the surface of the fuel cell separator A can be particularly improved.

  The fuel cell separator A according to the present invention is manufactured by the method as described above.

  According to the present invention, the hydrophilic treatment of the surface of the fuel cell separator can be performed with high efficiency by a simple method and the hydrophilicity of the fuel cell separator can be maintained over a long period of time. This prevents the gas supply / discharge groove in the fuel cell from being blocked by water droplets, so that the power generation efficiency of the fuel cell incorporating this fuel cell separator can be maintained high over a long period of time.

It is a perspective view which shows an example of embodiment of this invention. (A) is a schematic perspective view showing a unit cell of the fuel cell, and (b) is a schematic perspective view showing a fuel cell separator in the unit cell.

  Embodiments of the present invention will be described below.

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

Moreover, it is preferable that a molding composition does not contain a primary amine and a secondary amine. That is, it is preferable not to contain the compound having substituents —NH and —NH ₂ in the molding composition. Further, it is preferable that the molding composition does not contain a tertiary amine. For this reason, the separator A formed from this molding composition does not poison the platinum catalyst in the fuel cell, and can suppress a decrease in electromotive force when the fuel cell is used for a long time. .

  The thermosetting resin contains at least one of an epoxy resin and a thermosetting phenol resin as an essential component. 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, and the thermosetting resin is the epoxy resin only, the thermosetting phenol resin only, or the epoxy resin And thermosetting phenol resin alone are particularly preferred.

  It is preferable to use a solid epoxy resin, and it is particularly preferable to use an epoxy resin having a melting point in the range of 70 to 90 ° C. Thereby, there is little change of material and the handleability at the time of shaping | molding improves. If the melting point is less than 70 ° C., the produced molding material tends to aggregate and the handleability may be reduced. Further, 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 the moldability of the moldability composition.

  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. In addition, it is also preferable to use a resol type phenol resin. At this time, for example, 13C-NMR analysis shows a resol type having a structure of ortho-ortho 25-35%, ortho-para 60-70%, para-para 5-10%. It is preferable to use a phenol resin. 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. If this melting point is less than 70 ° C., it tends to aggregate in the molding composition, and the handleability may be reduced.

  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, for example, 4,4-diaminodiphenyl bismaleimide. By using this together, the heat resistance of the molded product 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.

  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. So that the equivalent ratio 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, and when it is 90% by mass or less, the molding composition is sufficiently excellent. The separator A is provided with sufficiently excellent gas permeability.

  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 may be deteriorated.

  Moreover, it is preferable to use a graphite particle having an average particle diameter of 1 to 150 μm. When the average particle size is 1 μm or more, the moldability of the molding composition is excellent, and when it is 150 μm or less, the surface smoothness of the molded body 1 can be improved. In order to particularly improve the moldability, the average particle size is preferably 15 μm or more, and the surface smoothness of the molded body 1 is particularly improved to increase the arithmetic average height Ra of the surface of the molded body 1 as described later. In order for (JIS B0601: 2001) to be in the range of 0.4 to 1.6 μm, the average particle size is preferably 60 μm or less.

  Further, the aspect ratio of the graphite particles is preferably 10 or less. In this case, it is possible to prevent anisotropy from occurring in the molded body 1 and to prevent deformation such as warpage.

  Regarding the reduction of the anisotropy of the molded body 1, the ratio of the contact resistance between the flow direction of the molding composition at the time of molding in the molded body 1 and the direction orthogonal to the flow direction is 2 or less. It is preferable that

  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 that the average particle size is in the range of 1 to 50 μm and the average particle size is 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 such as the bulk density of the separator A, the conductivity, the gas impermeability, the strength, etc. Can be achieved. At this time, 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 ratio of the former to the latter is 40:60 by mass ratio. It is preferable that it is -90: 10, especially 65: 35-85: 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.).

  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 is not preferable because the residue may poison the fuel cell catalyst. In addition, imidazoles are not preferred because they easily release chlorine ions after curing, which may cause impurity elution.

  As the curing catalyst, a phosphorus compound is preferably used. An example thereof 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.

  The coupling agent is preferably attached to the surface of the graphite particles by spraying or the like in advance. The addition amount 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 total amount of the coating agent coating area is 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 prevented from bleeding on the surface of the molded body 1 and contamination of the mold surface can be suppressed.

  As the wax (release agent), an appropriate one is used, and natural carnauba wax is particularly preferably used. Further, the content of the wax is appropriately set according to the complexity of the shape of the separator, the groove depth, the ease of releasability from the mold surface such as the draft, etc., but the total amount of the molding composition It is preferably in the range of 0.1 to 2.5% by mass, and when the content is 0.1% by mass or more, sufficient releasability is exhibited at the time of molding the mold, and the content is 2 When the content is 5% by mass or less, the hydrophilicity of the separator A is sufficiently inhibited by the wax. The wax content is particularly preferably in the range of 0.1 to 0.5% by mass.

  In addition, the content of ionic impurities in the molded body 1 is preferably such that the sodium content is 5 ppm or less and the chlorine content is 5 ppm or less in terms of mass ratio with respect to the total amount of the molding composition. The composition 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 in terms of 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 molded body 1 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. 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.

  In addition, the molding composition is preferably prepared such that the TOC (total organic carbon) of the molded body 1 formed with this composition is 100 ppm or less.

Here, TOC is a numerical value measured using an aqueous solution after the molded body 1 is charged into ion-exchanged water at a rate of 100 ml of ion-exchanged water with respect to 10 g of the molded body 1 and treated at 90 ° C. for 50 hours. It is. 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 CO ₂ concentration generated by burning the sample is measured by a non-dispersive infrared gas analysis method, and the carbon concentration in the sample is quantified. By measuring the carbon concentration, the 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. .

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

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

  In the molded body 1 formed in this way, when a thermosetting resin containing an epoxy resin is used and a curing agent containing a phenolic compound is used, hydroxyl groups generated in the cured product are distributed on the surface of the molded body 1. Become. In particular, by setting the equivalent ratio of the epoxy resin to the phenolic compound to be 0.8 to 1.2, the hydrophilicity of the molded body 1 is greatly improved by the surface treatment on the molded body 1 as will be described later, and this hydrophilicity. Will last for a long time. When the equivalent ratio is larger than 1.2, the above-mentioned effect cannot be obtained, and this is considered to be because the hydroxyl groups distributed in the molded body are insufficient. Also, when the equivalence ratio is less than 0.8, the reason is unclear, but the above effect cannot be obtained. In order to remarkably exert the effect of the surface treatment, particularly when the equivalent ratio is in the range of 0.8 to 1.0, the equivalent of the hydroxyl group becomes excessive and many hydroxyl groups are distributed on the surface of the molded body. More preferably, the equivalent ratio is in the range of 0.8 to 0.9.

  Further, when a thermosetting resin containing a thermosetting phenol resin is used, the hydroxyl groups resulting from the thermosetting phenol resin are distributed in the surface of the molded body 1 in the molded body 1. Thereby, as will be described later, the effect of improving the hydrophilicity by the surface treatment on the molded body 1 is improved.

  A surface treatment is performed on the surface of the molded body 1 by spraying it while burning a combustible gas containing a modifier compound. By this surface treatment, fine silicon oxide particles adhere to the surface of the molded body 1, thereby imparting excellent hydrophilicity to the surface of the molded body 1. At this time, since the hydroxyl groups are distributed on the surface of the molded body 1 as described above, the silicon oxide particles obtained by the surface treatment are firmly bonded to the hydroxyl groups of the molded body 1. For this reason, dropping of the silicon oxide particles from the surface of the molded body 1 is suppressed, and the hydrophilicity of the surface of the molded body 1 is maintained high over a long period of time.

  For example, as shown in FIG. 1, this surface treatment uses a burner 6 that injects a flame 5 in a curtain shape, and burns combustible gas with the burner 6 while conveying the molded body 1 in the direction of the arrow. This can be done by blowing the flame 5 toward the surface. As a result, the surface of the molded body 1 can be uniformly and efficiently subjected to surface treatment.

  In the surface treatment, a silicon compound or an aluminum compound is used as the modifier compound. The silicon compound and the aluminum compound are not particularly limited as long as they can be combusted in a flame of a general gas burner, but considering the availability and easy handling, the silicon compound is an alkylsilane compound. It is preferably at least one compound selected from the group consisting of alkoxysilane compounds, siloxane compounds, and silazane compounds, and the aluminum compound may be at least one compound selected from alkylaluminum compounds and alkoxyaluminum compounds. preferable.

  Examples of the alkylsilane compound include methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, tetraethylsilane, dimethyldichlorosilane, dimethyldiphenylsilane, diethyldichlorosilane, diethyldiphenylsilane, methyltrichlorosilane, methyltriphenylsilane, and dimethyldiethylsilane. A monosilane compound that may have a substituent such as hexamethyldisilane, hexaethyldisilane, a disilane compound that may have a substituent such as chloroheptamethyldisilane, and a substituent such as octamethyltrisilane. Examples thereof may include trisilane compounds.

  Examples of the alkoxysilane compound include methoxysilane, dimethoxysilane, trimethoxysilane, tetramethoxysilane, ethoxysilane, diethoxysilane, triethoxysilane, tetraethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyl Triethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dichlorodimethoxysilane, dichlorodiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trichloromethoxysilane, trichloroethoxysilane, tri Examples thereof include phenylmethoxysilane and triphenylethoxysilane.

  Examples of the siloxane compound include tetramethyldisiloxane, pentamethyldisiloxane, hexamethyldisiloxane, octamethyltrisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. Is mentioned.

  Examples of the silazane compound include hexamethyldisilazane.

  Examples of the alkylaluminum compound include trimethylaluminum, triethylaluminum, and tripropylaluminum.

  Examples of the alkoxyaluminum compound include aluminum methoxide and aluminum ethoxide.

  These modifier compounds may be used individually by 1 type, or multiple types may be used together.

  As such a modifier compound, for example, an Itro treatment agent manufactured by Itro Co., Ltd. containing a silicon compound can be mentioned.

The content of the modifier compound in the combustible gas is appropriately set according to the degree of hydrophilicity required for the surface of the molded body 1 and is not particularly limited. On the other hand, it can be made into the range of 1 * 10 < ^-10 > ^-10 mol%. In this case, when the content of the modifier compound is 1 × 10 ⁻¹⁰ mol% or more, the hydrophilicity of the surface of the separator A can be particularly improved by the surface treatment, and the content is 10 mol%. By being below, the mixability of the modifier compound and air etc. in combustible gas becomes high, and the incomplete combustion of a modifier compound is suppressed.

  Moreover, it is preferable that combustible gas contains air. This air can control the temperature of the flame 5, and this air can exert a carrier effect, and the uniformity of the surface treatment is increased.

  The combustible gas preferably contains a hydrocarbon gas as a combustion fuel, and particularly preferably contains propane gas or LPG (liquefied petroleum gas) as the hydrocarbon gas. Examples of LPG include butane (normal butane, isobutane), mixed gas of butane / propane, ethane, pentane (normal pentane, isopentane, cyclopentane) and the like. Propane gas and LPG are inexpensive and can be combusted at a predetermined temperature to stably thermally decompose the modifier compound, further improving the uniformity of the surface treatment.

  The amount of hydrocarbon gas and air in the combustible gas is appropriately set so as to suppress incomplete combustion of the modifier compound and to impart desired hydrophilicity to the surface of the molded body 1.

  In the surface treatment, the combustion temperature of the combustion gas suppresses incomplete combustion of the modifier compound, imparts desired hydrophilicity to the molded body 1, and suppresses thermal deformation and thermal deterioration of the molded body 1. Although it sets suitably so that it can do, it can be set as the range of 500-1500 degreeC, for example.

Moreover, the spraying time of the flame 5 with respect to the molded object 1 is also set suitably so that desired hydrophilicity may be provided to the molded object 1 and the thermal deformation and thermal deterioration of the molded object 1 can be suppressed effectively. However, for example, per 100 cm < ² > of the area of the molded body 1, the range may be 0.1 to 100 seconds.

  In performing the surface treatment on the molded body 1 in this way, the arithmetic average height Ra (JIS B0601: 2001) of the surface on which the surface treatment of the molded body 1 is performed is set in the range of 0.4 to 1.6 μm. It is preferable. In this case, the uniformity of the surface treatment is further increased, and the adhesion of the silicon oxide particles on the surface of the molded body 1 is further increased, so that the hydrophilicity of the surface of the molded body 1 can be further improved. The arithmetic average height Ra of the molded body 1 can be adjusted by adjusting the particle size of the graphite particles in the molded body 1 or by performing blasting or the like on the surface of the molded body 1 as described above. it can.

  Further, the ratio A / B between the width A and the depth B of the gas supply / discharge groove 2 formed on the surface of the molded body 1 on which the surface treatment is performed is preferably 1 or more. The flame 5 during the surface treatment easily spreads inside the gas supply / discharge groove 2, and the uniformity of the surface treatment is further enhanced. Further, the upper limit of the ratio A / B is not particularly limited, but in order to form the gas supply / discharge grooves 2 with high density, it is preferably 10 or less in practice.

  Prior to this surface treatment, the surface of the molded body 1 to be subjected to the surface treatment may be previously subjected to plasma treatment. By performing this plasma treatment, functional groups such as hydroxyl groups can be introduced on the surface of the molded body 1, and the silicon oxide or aluminum oxide particles adhering to the surface of the molded body 1 by the surface treatment are bonded to the functional groups. Thus, the particles of silicon oxide or aluminum oxide are more difficult to drop off from the surface of the molded body 1, and the hydrophilicity of the surface of the separator A is maintained for a longer period of time. The plasma treatment can be performed under conditions appropriately set so that a desired functional group can be introduced onto the surface of the molded body 1. For example, a plasma generation gas is used using a model number “PDC210” manufactured by Yamato Material Co., Ltd. As oxygen, it can be performed under the conditions of an applied power of 150 to 500 W and a treatment time of 30 seconds to 10 minutes.

  Further, by such surface treatment, it is preferable that the static contact angle with water on the surface of the molded body 1 after the treatment is in a range of 0 ° to 50 °, particularly in a range of 0 ° to 10 °. Preferably, it is more preferably in the range of 0 ° to 5 °. The static contact angle with water can be adjusted by appropriately setting the surface treatment conditions. Thereby, sufficiently high hydrophilicity can be imparted to the surface of the molded body 1.

Moreover, it is preferable that the contact resistance of the surface-treated surface of the molded body 1 is 15 mΩcm ² or less by such surface treatment. This contact resistance can also be adjusted by appropriately setting the surface treatment conditions. Since the film thickness of silicon oxide or aluminum oxide attached to the molded body 1 by the surface treatment is very thin, it is easy to achieve such a low contact resistance. Thereby, the function of the separator A that transmits electric energy generated by the fuel cell to the outside can be maintained at a high level.

  A fuel cell can be produced using the separator A produced as described above. FIG. 2 shows an example of a polymer electrolyte fuel cell. Between two fuel cell separators A and A, a polymer electrolyte membrane 4 and a gas diffusion electrode (fuel electrode and oxidant electrode) 3, A single battery (unit cell) is configured with 3 interposed. A battery body (cell stack) can be formed by arranging several tens to several hundreds of unit cells.

  In this fuel cell, the hydrophilicity is imparted to the surface of the separator A, so that the gas supply / discharge groove 2 in the separator A is less likely to be blocked by water droplets, and a decrease in power generation efficiency of the fuel cell can be suppressed. . Further, since the hydrophilicity of the separator A can be maintained for a long period, the power generation efficiency of the fuel cell can be maintained high for a long period.

  Hereinafter, the present invention will be described in detail based on examples.

(Examples 1-19, Comparative Examples 1-3)
For each of the examples and comparative examples, the 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 stirred and mixed, and the resulting mixture was sized. And pulverized to a particle size of 500 μm or less.

  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 with the mold closed, and after holding for 30 seconds, the mold was opened and the molded body 1 was taken out.

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

The surface of the molded body 1 was blasted to adjust the arithmetic average height Ra (JIS B0601: 2001) as shown in Table 1, and then the surface of the molded body 1 was subjected to surface treatment. In the surface treatment, a flame 5 produced by burning a combustible gas composed of the modifier compound shown in Table 1, LPG and air and containing 2 mol% of the modifier compound. Was sprayed onto the compact 1 for 1 second per 100 cm ^{2 of} area.

  In Example 7, prior to the surface treatment, the surface of the molded body 1 was subjected to plasma treatment using oxygen as a plasma generating gas under conditions of an applied power of 300 W and a treatment time of 3 minutes.

(Bending strength evaluation)
In each of the examples and comparative examples, a molded product for measuring bending strength having dimensions of 80 mm × 10 mm × 4 mm was prepared in the same manner as in the case of manufacturing the separator A, and the distance between fulcrums was 64 mm according to JIS K6911. The bending strength was measured at a speed of 2 mm / min.

(Contact resistance evaluation)
In each of the examples and comparative examples, the thickness of the separator A was formed to 3 mm, the carbon paper was disposed above and below the separator A, the copper plates were further disposed above and below it, and a surface pressure of 1 MPa was applied in the vertical direction. . The voltage between the two carbon papers was measured with a voltmeter and the current between the two copper plates was measured with an ammeter, and the resistance (average value) was calculated from the result. The carbon paper used is TGP-HM series (090M: thickness 0.28 mm, 120M: thickness 0.38 mm) manufactured by Toray.

(TOC evaluation)
In accordance with JIS K0551-4.3, the molded body 1 in each example and comparative example was first washed with methanol for 1 minute and then washed with ion-exchanged water for 1 minute. Next, the molded body 1 and ion-exchanged water were placed in a glass container so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded body 1 and treated at 90 ° C. for 50 hours. After adjusting the pH to 2 or less by adding phosphoric acid to the ion-exchanged water after the treatment, the amount of organic carbonic acid is measured by a wet oxidation-infrared TOC measurement method (using “Toray Stro TOC Automatic Analyzer MODEL1800” manufactured by Toray Engineering Co., Ltd.). Was measured.

(Static contact angle evaluation)
The separator A obtained in each Example and Comparative Example was horizontally arranged, and ion-exchanged water was dropped on the surface with a dropper, using a measuring instrument (product number “CA-W150”) manufactured by Kyowa Interface Science Co., Ltd. The static contact angle with water was measured.

  The separator A was poured into warm water at 90 ° C. and left for a certain period of time, and then dried. The standing time was 500 hours, 1000 hours, 1500 hours, and 2000 hours. About the separator A after this treatment, the static contact angle with water was measured in the same manner as described above.

(Water-soluble ion analysis)
The molded body 1 in each example and comparative example was washed with methanol for 1 minute, and then washed with ion-exchanged water for 1 minute. Next, the molded body 1 and ion-exchanged water were placed in a polyethylene container so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded body 1 and treated at 90 ° C. for 50 hours. The ion-exchanged water (extracted water) after the treatment was measured by ion chromatography (“CDD-6A” manufactured by Shimadzu Corporation).

(Electrical conductivity evaluation)
The molded body 1 in each example and comparative example was washed with methanol for 1 minute, and then washed with ion-exchanged water for 1 minute. Next, the molded body 1 and ion-exchanged water were placed in a polyethylene container so that the amount of ion-exchanged water was 100 ml with respect to 10 g of the molded body 1 and treated at 90 ° C. for 50 hours. The ion-exchanged water (extracted water) after the treatment was measured with a conductivity meter.

(Evaluation of fuel cell electromotive voltage fluctuation)
In each example and comparative example, a fuel having a structure shown in FIG. 2 is provided by interposing a solid polymer electrolyte membrane 4 and gas diffusion electrodes (fuel electrode and oxidant electrode) 3 and 3 between separators A and A. A battery was produced. Then, these fuel cells 1 were continuously operated for 1000 hours in a state where an external circuit was connected, and the state of fluctuation of the electromotive voltage (V) with time was investigated. The results were expressed as a percentage of the initial value of the electromotive voltage after fluctuation.

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.)
<Modifier compound>
-Modification treatment agent A: Tetramethoxysilane-Modification treatment agent B: Methyltrimethoxysilane-Modification treatment agent C: Dimethyldimethoxysilane-Modification treatment agent D: Dimethyldiethoxysilane-Modification treatment agent E: Itro Itoro treatment agent (groove depth / width evaluation)
In Example 1-19, the separators A each having a depth B of the gas supply / discharge groove 2 of 1 mm and a ratio A / B of the width A to the depth B of 0.8, 1, 5, 10 were respectively Produced.

  Static contact angle evaluation was performed on the inner surface of the gas supply / discharge groove 2 of each separator A. As a result, in any case of Example 1-19, the static contact angle with water is 10 ° when A / B is 0.8, and when A / B is 1, 5 and 10. It was 5 °.

A Fuel cell separator (separator)
1 Molded body 2 Gas supply / discharge groove

Claims (10)

  A molding composition containing a thermosetting resin containing an epoxy resin, a curing agent containing a phenolic compound, and graphite particles, wherein the equivalent ratio of the epoxy resin to the phenolic compound is in the range of 0.8 to 1.2. A method for producing a fuel cell separator, wherein a surface treatment is performed by molding a product and spraying the surface of the obtained molded body while burning a gas containing a modifier compound containing a silicon compound or an aluminum compound.   A molding composition containing a thermosetting resin containing a thermosetting phenol resin and graphite particles is molded, and a gas containing a modifier compound containing a silicon compound or an aluminum compound is formed on the surface of the resulting molded body. A method for producing a fuel cell separator, wherein the surface treatment is performed while spraying.   The arithmetic mean height Ra (JIS B0601: 2001) of the surface to which the surface treatment of the molded body is performed is in a range of 0.4 to 1.4 μm. Manufacturing method of fuel cell separator.   The method for producing a fuel cell separator according to any one of claims 1 to 3, wherein the surface treatment is performed after the molded body is subjected to plasma treatment.   The method for producing a fuel cell separator according to any one of claims 1 to 4, wherein the silicon compound is at least one of a silane compound and a silicone compound.   The said modifier compound contains at least 1 type selected from the alkylsilane compound, the alkoxysilane compound, the siloxane compound, the silazane compound, the alkylaluminum compound, and the alkoxyaluminum compound, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. A method for producing a fuel cell separator according to claim 1.   6. A gas supply / discharge groove having a ratio A / B of a width A to a depth B of 1 or more is formed on a surface of the molded body on which the surface treatment is performed. The manufacturing method of the fuel cell separator as described in any one. The method for producing a fuel cell separator according to any one of claims 1 to 7, wherein the surface treatment is performed so that a contact resistance of the surface-treated surface is 15 mΩcm ² or less.   The fuel cell according to any one of claims 1 to 8, wherein the surface treatment is performed so that a static contact angle with water of the surface treated surface is in a range of 0 to 50 °. Separator manufacturing method.   A fuel cell separator manufactured by the method according to any one of claims 1 to 9.

Images