JP5185661B2 - Fuel cell separator - Google Patents

Description

  The present invention relates to a fuel cell separator incorporated in a fuel cell.

  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 “fuel cell separator / fuel electrode (anode) / electrolyte / oxidant electrode (cathode) / fuel cell 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. 1 shows an example of a polymer electrolyte fuel cell. A solid polymer fuel cell is disposed between two fuel cell separators 1 and 1 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 2 and 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. At this time, a gas supply / discharge groove 4 serving as a flow path for hydrogen gas as a fuel and oxygen gas as an oxidant is formed between the adjacent convex portions 1a.

  Such a cell stack is composed of, for example, 50 to 100 unit cells in a stationary type for home use, and is composed of 400 to 500 unit cells for automobile loading.

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 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 be operated in a humid atmosphere in the range of room temperature to 120 ° C., and therefore water is often handled in a liquid state. Therefore, it is necessary to replenish the liquid water and to discharge the liquid water from the oxidizer electrode.

  Among the components constituting such a fuel cell, the fuel cell separator 1 has a plurality of gas supply / discharge grooves on one or both sides of a thin plate-like body as shown in FIGS. 1 (a) and 1 (b). 4 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 And plays an important role of radiating the heat generated in the fuel cell to the outside.

  In general, the fuel cell separator 1 has the following requirements. (1) High conductivity, (2) Corrosion resistance (acid resistance) against corrosive electrolytes, (3) Airtightness to separate gases, (4) Tightening with bolts and nuts when assembling to a fuel cell It has strength to prevent the fuel cell separator 1 from being cracked or cracked during assembling work, etc., as well as mechanical strength, and particularly excellent vibration resistance and impact resistance when used as a mobile power source for automobiles etc. Creep resistance, (5) moldability for forming complex shapes, (6) low cost, (7) swelling resistance (those that do not swell when immersed in water or aqueous sulfuric acid solution), (8) Heat resistance (withstand heat generation during reaction (90 to 120 ° C.)), (9) It is required to satisfy the required characteristics at the same time, such as liquid water does not accumulate.

  As the fuel cell separator 1 of such a polymer electrolyte fuel cell, a carbon composition using various thermoplastic resins or thermosetting resins, which are advantageous in terms of productivity and cost, as a binder has been proposed ( For example, see Patent Documents 1 to 5).

Here, among the above characteristics required for the fuel cell separator 1, in order to exhibit the characteristics that liquid water does not accumulate, an approach to improve the hydrophilicity of the surface of the fuel cell separator 1, An approach to increase the water absorption of the fuel cell separator 1 can be considered. Among these, in order to increase the water absorption of the fuel cell separator 1, it is conceivable that the fuel cell separator 1 contains a porous material such as alumina aerosil.
JP 59-26907 A JP-A-55-61752 JP-A-56-116277 Japanese Patent Laid-Open No. 8-31231 JP 59-26907 A

  However, if the fuel cell separator 1 contains alumina aerosil or the like, the conductivity of the fuel cell separator 1 is lowered, and the fuel cell separator 1 may not function sufficiently. In order to improve the function of the fuel cell separator 1, it is preferable to adopt a method as simple as possible from the viewpoint of improving manufacturing efficiency.

  The present invention has been made in view of the above points. The water absorption of the fuel cell separator is improved by a simple method and without deterioration of other characteristics of the fuel cell separator 1. An object of the present invention is to provide a fuel cell separator in which the accumulation of water is suppressed.

  The fuel cell separator 1 according to the present invention is characterized by containing activated carbon. For this reason, the water absorption of the fuel cell separator 1 is improved by the activated carbon, and furthermore, since the activated carbon is a conductive material, the conductivity of the fuel cell separator 1 is not impaired, and other characteristics are also prevented from being impaired. Is done.

  The content of the activated carbon is preferably in the range of 5 to 10% by mass. In this case, the water absorption rate of the fuel cell separator 1 is remarkably improved and particularly high moldability is maintained.

The fuel cell separator 1 is preferably manufactured by molding a composition for a fuel cell separator that contains a thermosetting resin and graphite particles, and that contains activated carbon as part of the graphite particles . In this case, the fuel cell separator 1 excellent in various properties such as moldability and conductivity required for the fuel cell separator 1 can be obtained.

  Moreover, it is preferable that the said thermosetting resin contains at least one among a phenol resin and an epoxy resin. The phenol resin and the epoxy resin are suitable because they have a good resin viscosity and few impurities.

The graphite particles other than the activated carbon are preferably natural graphite having an average particle diameter of 3 to 150 μm. In this case, moldability and surface smoothness are maintained at a higher level.

  The fuel cell separator 1 preferably has a water absorption of 1% or more when exposed to an atmosphere of 105 ° C. and 100 RH for 500 hours. In this case, sufficient water absorption is imparted to the fuel cell separator 1.

  According to the present invention, the water absorption of the fuel cell separator is improved, so that when the liquid water adheres to the fuel cell separator, the water is absorbed, and the liquid water does not easily accumulate in the fuel cell separator. . At this time, the water absorption of the fuel cell separator is sufficiently improved by a simple method of including activated carbon in the fuel cell separator, and other characteristics required for the fuel cell separator are not hindered. is there.

  The best mode for carrying out the present invention will be described below.

  The fuel cell separator 1 according to the present invention contains activated carbon. Since the activated carbon is porous, the water absorption is high, and therefore the water absorption of the fuel cell separator 1 is improved. Moreover, since activated carbon is a conductive material, even if the fuel cell separator 1 contains activated carbon, the conductivity of the fuel cell separator 1 is not impaired, and the corrosion resistance, air tightness, strength, and moldability of the fuel cell separator 1 are not impaired. It does not cause the deterioration of various characteristics such as.

  In order to maintain high conductivity of the fuel cell separator 1 and to suppress elution of impurities from the fuel cell separator 1, the activated carbon is preferably of high purity. In particular, activated carbon having a purity in the range of 99% or more is preferably used.

  Here, if the activated carbon is contained, the water absorption of the fuel cell separator 1 is improved by that amount. In particular, if this content is 5% by mass or more with respect to the total amount of the fuel cell separator 1, the fuel Particularly high water absorption is imparted to the battery separator 1. In addition, as the content of the activated carbon increases, the improvement in water absorption increases. However, when the content is excessive, other materials constituting the fuel cell separator 1 are adsorbed on the activated carbon, thereby forming the fuel cell separator 1. May decrease. In order to suppress such a decrease in moldability, the content is desirably 10% by mass or less.

  Such a fuel cell separator 1 is manufactured by molding a composition for a fuel cell separator containing activated carbon.

  The composition for a fuel cell separator is preferably a mixture containing a synthetic resin and a conductive material (including activated carbon), and particularly preferably contains a thermosetting resin and graphite particles. At this time, the activated carbon is contained in the fuel cell separator composition as a part of the graphite particles.

  Inclusion of graphite particles in the fuel cell separator composition contributes to a reduction in the electrical resistivity of the fuel cell separator 1 and improves the conductivity of the fuel cell separator 1. The content of the graphite particles is preferably 60 to 90% by mass, more preferably 75 to 90% by mass with respect to the total amount of the composition. If the ratio of the graphite particles is too small, the conductivity required for the fuel cell separator 1 may not be sufficiently obtained, and if it is excessive, the gas permeability and molding required for the fuel cell separator 1 may be lost. There is a risk that sufficient properties cannot be obtained.

  The particle size of the graphite particles is not particularly limited, but an average particle size of 3 to 150 μm is particularly preferable. If the average particle size is less than 3 μm, the moldability is lowered, and if it exceeds 150 μm, the surface smoothness of the molded product may be impaired.

  The graphite particles preferably have an aspect ratio of 10 or less. If this aspect ratio exceeds 10, the molded fuel cell separator 1 may become anisotropic and warp.

  Any graphite particles other than activated carbon can be used without limitation as long as they exhibit high conductivity. Specific examples of the graphite particles include, for example, graphitized carbonaceous materials such as mesocarbon microbeads, graphitized coal-based coke and petroleum-based coke, graphite electrode and processed powder of special carbon material, natural powder Suitable examples include graphite, quiche graphite, expanded graphite and the like. 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 artificial graphite or natural graphite, but natural graphite has an advantage of high conductivity. Artificial graphite has the advantage of low anisotropy, although its conductivity is somewhat inferior to natural graphite powder.

  Further, when the graphite particles are particularly spherical natural graphite particles, the crystallinity of graphite, that is, the conductivity is high, and there is no anisotropy, so the fluidity is good and the molding with excellent conductivity is possible. Become. However, since spherical graphite is difficult to form a conductive path, the conductivity as a molded product is lowered when only a single piece is used. For this reason, the combined use with anisotropic graphite is preferable.

  The graphite particles are preferably purified from natural graphite or artificial graphite. In this case, since the ash content and ionic impurities are low, the fuel cell is a molded product. The elution of impurities from the separator 1 is suppressed.

  Here, the ash content in the graphite particles is preferably 0.05% by mass or less, and the ionic impurities in the extracted water have a sodium content of 5 ppm or less and a chlorine content of 5 ppm or less by mass ratio with respect to the total amount of the graphite particles. It is preferable to make it.

  If the above ash content exceeds 0.05% by mass, there is a risk that the characteristics of the fuel cell will deteriorate. Further, when the ionic impurities in the extracted water exceed 5 ppm of sodium or exceed 5 ppm of chlorine, when the fuel cell separator 1 is formed, the characteristics of the fuel cell may be deteriorated due to elution of impurities. .

  Here, the extracted water is obtained by dispersing the target component in ion-exchanged water at a ratio of 100 ml of ion-exchanged water with respect to 10 g of the target component (here, graphite particles) and treating at 90 ° C. for 50 hours. Ionic impurities in the extracted water are evaluated by ion chromatography. Based on the amount of ionic impurities in the extracted water to be derived, the total amount of ionic impurities in the target component in the composition is converted into a mass ratio with respect to the total amount of the target component in the composition. It is. The content of ionic impurities is measured by the same method as described above except for graphite.

  As the thermosetting resin, an appropriate one applicable to resin molding is adopted. In particular, the thermosetting resin preferably includes at least one of an epoxy resin and a phenol resin. These epoxy resins and phenol resins are suitable because they have good resin viscosity and few impurities. In particular, epoxy resins are particularly excellent because they contain few ionic impurities. When the thermosetting resin contains at least one of an epoxy resin and a phenol resin, the total amount of the epoxy resin and the phenol resin may be in the range of 50 to 100% by mass with respect to the total amount of the thermosetting resin. preferable.

  In addition to these resins, one or more types of resins selected from polyimide resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, etc. may be used in combination. There is a risk of hydrolysis. Among these resins, polyimide resin is particularly suitable in terms of contributing to improvement of heat resistance and acid resistance. As such a polyimide resin, a bismaleimide resin is particularly preferable, and for example, 4,4-diaminodiphenyl bismaleimide is preferable. By using this 4,4-diaminodiphenyl bismaleimide in combination, the heat resistance of the fuel cell separator 1 is further enhanced.

  Further, in these thermosetting resins, it is preferable that the content of chlorine ions, which are ionic impurities, and the content of sodium ions are both 5 ppm or less by mass ratio with respect to the total amount of the thermosetting resin. In this case, the elution of impurities from the fuel cell separator 1 which is a molded product is further reduced.

  The epoxy resin is preferably a solid epoxy resin, particularly preferably an epoxy resin having a melting point in the range of 70 to 130 ° C. Thereby, the change of a material decreases and the handleability at the time of shaping | molding improves. When the melting point is less than 70 ° C., the composition tends to aggregate and the handleability may be reduced. Such an epoxy resin is preferably contained in a proportion of 50 to 100% by mass with respect to the total amount of the thermosetting resin.

  Moreover, it is also preferable to use a low-viscosity epoxy resin. In this case, the moldability of the composition is maintained and the graphite particles are highly filled.

  The phenol resin is preferably 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. The content of such a phenol resin is preferably in the range of 5 to 50% by mass with respect to the total amount of the thermosetting resin.

  Moreover, it is also preferable that a phenol resin is a resol type phenol resin. In this case, the resol type phenol resin preferably has a structure of ortho-ortho 25-35%, ortho-para 60-70%, para-para 5-10%, for example, by 13C-NMR analysis. The resol resin is usually in a liquid state, but the above-mentioned resol type phenol resin can easily adjust the softening point, and a phenol resin having a melting point of 70 to 80 ° C. can be easily obtained. Thereby, the change of a material decreases and the handleability at the time of shaping | molding improves. When the melting point is less than 70 ° C., the composition tends to aggregate and the handleability may be reduced. The content of such a resol type phenol resin is preferably in the range of 10 to 70% by mass with respect to the total amount of the thermosetting resin.

  The composition may contain additives such as a curing initiator, a curing catalyst, a wax (release agent), and a coupling agent as necessary. At this time, it is preferable not to include a primary amine and a secondary amine in the composition, and it is preferable not to further include a tertiary amine. In this case, poisoning of the platinum catalyst in the fuel cell by the amine mixed in the fuel gas is prevented, and a decrease in electromotive force when the fuel cell is used for a long time is suppressed.

  That is, the curing initiator (curing agent) when an epoxy resin is used is preferably a non-amine compound. In the case of amines, the fuel cell catalyst may be poisoned. It is also preferred that the curing initiator is not an acid anhydride compound. An acid anhydride-based compound may be hydrolyzed in an acid-resistant environment such as a sulfuric acid acid environment, thereby increasing the elution of impurities from the fuel cell separator 1.

  As the curing initiator (curing agent), a phenol compound is particularly preferable. In this case, the characteristics of the molded product are excellent.

  The content of the curing initiator is appropriately set, but the stoichiometric equivalent ratio of the curing initiator to the epoxy resin is preferably 1 to 1.12.

  In addition, the curing catalyst (curing accelerator) used together with the epoxy resin is not particularly limited, but a non-amine compound is preferable in order not to contain a primary amine and a secondary amine in the composition. For example, amine-based diaminodiphenylmethane is not preferred 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 used together with the epoxy resin, a phosphorus compound is preferably used. One example is triphenylphosphine. When such a phosphorus compound is contained, elution of chlorine ions from the fuel cell separator 1 which is a molded product is suppressed.

  Also in the curing initiator and the curing catalyst as described above, the content of chlorine ions, which are ionic impurities, and the content of sodium ions are each preferably 5 ppm or less by mass ratio. In this case, elution of ionic impurities from the fuel cell separator 1 which is a molded product is further suppressed.

  Although content of the said curing catalyst is adjusted suitably, Preferably it is set as the range of 0.5-3 mass parts with respect to an epoxy resin.

  Moreover, a coupling agent can be contained in the composition. As this coupling agent, an appropriate one is used, but it is preferable that the composition does not contain a primary amine and a secondary amine. It is also preferred that the coupling agent is not mercaptosilane. Similarly, when mercaptosilane is used, the fuel cell catalyst may be poisoned.

  Examples of the coupling agent used include silicon-based silane compounds, titanate-based, aluminum-based and the like. 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 of the coupling agent is appropriately set, but preferably the total amount of the area covered by the coupling agent is in the range of 0.5 to 2 times the total surface area of the graphite particles. When this value increases, the coupling agent bleeds on the surface of the molded product, and the mold surface may be contaminated during molding.

  When the composition contains a wax (release agent), an appropriate wax is used, and natural carnauba wax is particularly preferable. Moreover, although content of a wax is set suitably, the range of 0.1-2.5 mass% is preferable with respect to the composition whole quantity. If this content is less than 1% by mass, sufficient releasability cannot be obtained during molding, and if it exceeds 2.5% by mass, sufficient wettability with water required for the fuel cell separator 1 is obtained. There is a risk of being lost.

  Further, this wax also preferably has a content of chlorine ions, which are ionic impurities, and a content of sodium ions of 5 ppm or less in terms of mass.

  Moreover, it is preferable that the composition prepared in the present invention has a TOC (total organic carbon) of a molded article formed from the composition of 100 ppm or less. If the TOC exceeds 100 ppm, the characteristics of the fuel cell may deteriorate.

Here, the TOC is a numerical value measured using an aqueous solution after processing a molded product having a specific surface area of 20 cm ² / g at 90 ° C. for 50 hours. Such TOC is measured by, for example, a total organic carbon analyzer “TOC-50” manufactured by Shimadzu Corporation based on JIS K0102. The measuring method is as follows. First, the sample is burned and thermally decomposed, and the generated CO ₂ concentration is measured by a non-dispersive infrared gas analysis method to determine the total carbon (TC) in the sample. Further, the concentration of CO ₂ liberated by adding an acid to the sample is measured in the same manner, and inorganic carbon (IC) is quantified in the same manner as TC. Total organic carbon (TOC) is derived from the difference between the total carbon and the inorganic carbon (TC-IC).

  Here, the reduction of the TOC is achieved, for example, by using a high-purity raw material, adjusting the equivalent ratio of the resin, or adopting a post-curing treatment.

  In addition, the content of chlorine ions and sodium ions, which are water-soluble ions, in the entire composition is preferably 5 ppm or less in terms of mass ratio with respect to the total amount of the composition. If this value exceeds 5 ppm, the characteristics of the fuel cell may deteriorate due to the elution of impurities from the molded fuel cell separator 1.

Based on the mass of the composition, the content of the above-mentioned chlorine ions and sodium ions is obtained by extracting water-soluble ions from a molded product obtained by molding the composition and evaluating and measuring the ions by ion chromatography. It is derived by conversion. At this time, a molded product having a specific surface area of 20 cm ² / g is made into 100 mL of ion-exchanged water with respect to 10 g of the molded product, and the molded product is immersed in ion-exchanged water and treated at 90 ° C. for 50 hours, whereby ions are ionized in the ion-exchanged water. By extracting, water-soluble ions are extracted.

  The composition for a fuel cell separator is prepared by an appropriate technique. For example, the components described above are mixed by an appropriate technique to prepare a mixture, and the mixture is stirred or kneaded as necessary. Further, the composition for a fuel cell separator is prepared by granulating and further pulverizing to reduce the diameter as necessary.

  A specific example of a method for preparing a composition for a fuel cell separator will be described.

  For example, first, a mixture obtained by blending each component constituting the composition is stirred. At this time, you may mix | blend the component except a thermosetting resin. When this mixture contains a thermosetting resin at this time, it is preferable to stir in the state heated to the temperature more than the melting start temperature of a thermosetting resin. Although the said heating temperature is suitably set according to the kind of thermosetting resin, Preferably the upper limit of heating temperature shall be 120 degreeC. Moreover, time, such as stirring, can be 5 to 30 minutes, for example. In this way, the mixture is stirred and the like while the thermosetting resin is melted, so that the thermosetting resin and other components such as graphite particles are uniformly mixed.

  Next, a solvent for dissolving the thermosetting resin (for example, isopropyl alcohol, methanol, etc.) is added to the mixture by dropping, spraying, and the like, and the mixture is further mixed by further stirring. Here, when the mixture does not contain the thermosetting resin at this stage, the thermosetting resin is added to the mixture before the stirring. This stirring time is, for example, 5 to 30 minutes. Particularly when the solvent is added by spraying at this time, the resin component and the graphite particles are mixed well, and a large lump is prevented from being generated in the composition, so that a fine granular composition is obtained. The spraying conditions when the solvent is added by spraying are preferably a spray pressure of 0.05 to 0.3 MPa, a spray air amount of 5 to 50 ml / min, and a fluid pressure of 0.05 to 0.5 MPa. The amount of the solvent used is adjusted to an appropriate amount so that all the thermosetting resin can be dissolved. Preferably, the amount of the solvent used is 50% by mass or less based on the total solid content of the raw material. To be. If the amount of the solvent used is excessive, the time required for volatilization of the solvent becomes long and the productivity is lowered. The amount used is more preferably 25% by mass or less. Further, even during this stirring, if stirring is performed in a state of being heated to a temperature equal to or higher than the melting start temperature of the thermosetting resin as described above, further uniform mixing is possible.

  Next, granulation is performed by stirring the mixture and volatilizing the solvent. The stirring time at this time is preferably 5 to 30 minutes. Volatilization of the solvent can be performed by heating the mixture, reducing the pressure of the atmosphere around the mixture, or the like. The pressure may be reduced simultaneously with the heating. The heating temperature can be a temperature equal to or higher than the temperature at which the thermosetting resin in the mixture is dissolved, and the pressure at the time of depressurization can be set in the range of, for example, 0.1 MPa to 0.01 MPa. At this time, it is preferable that the solvent in the mixture is sufficiently volatilized, and if this solvent remains, voids may be generated in the molded article.

  The composition is prepared as described above, and this composition can be further formed into a smaller particle size by further pulverizing with a granulator or the like. At this time, if the composition is formed into particles having a particle size of 500 μm or less, for example, unfilling during molding can be further suppressed.

  The fuel cell separator composition obtained as described above is used for molding the fuel cell separator 1. As a molding method at this time, an appropriate method such as injection molding or compression molding is employed. The fuel cell separator 1 is formed in a shape as shown in FIG. 1 as described above, for example.

  Since the fuel cell separator 1 formed in this way contains activated carbon, it has high water absorption. For this reason, even if liquid water adheres to the surface of the fuel cell separator 1, this water is absorbed by the fuel cell separator, and liquid water is prevented from accumulating in the fuel cell separator 1. At this time, the improvement of the water absorption of the fuel cell separator 1 is achieved by a simple method of containing activated carbon, so that the production efficiency of the fuel cell separator 1 is not lowered. Moreover, since activated carbon is used as described above, the conductivity of the fuel cell separator 1 is not impaired, and other characteristics such as strength are not deteriorated.

  The fuel cell separator 1 thus formed preferably has a water absorption rate of 1% or more when exposed to an atmosphere of 105 ° C. and 100 RH for 500 hours. This water absorption is achieved by adjusting the content of activated carbon according to the components constituting the fuel cell separator 1. When the water absorption rate of the fuel cell separator 1 is within the above range, the fuel cell separator 1 exhibits sufficient water absorption, and liquid fuel can be sufficiently prevented from accumulating in the fuel cell separator 1.

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

(Examples 1-10, Comparative Examples 1-3)
For each example and comparative example, a mixture having the composition shown in Table 1 was charged into a stirring mixer ("5XDMV-rr type" manufactured by Dalton), and the mixture was stirred while heating the stirring mixer to 90 ° C with warm water. . Next, a solvent (methanol) was added in an amount shown in Table 1 to this mixture, and stirring was further continued for 10 minutes. Next, the solvent was completely removed from the mixture by drying under reduced pressure at 90 ° C. using a vacuum pump. Further, this mixture was pulverized to a particle size of 500 μm or less with a granulator to obtain a composition for a fuel cell separator.

This composition was compression molded under the conditions of a temperature of 175 ° C., a pressure of 34.3 MPa (350 kg / cm ² ), and a molding time of 20 minutes, and then demolded to obtain a molded product.

  In addition, the compounding quantity of each component in Table 1 is shown by the mass part.

(Evaluation)
Evaluation of water absorption rate: The molded products obtained in each Example and Comparative Example were exposed to an atmosphere of 105 ° C and 100RH for 500 hours, and the water absorption rate was measured based on the difference in mass before and after.

  -Volume resistivity evaluation: It measured based on JISK7194.

  Three-point bending strength: The three-point bending strength was measured by setting the distance between the fulcrums to 16 times the thickness of the test piece (4 mm).

  -Formability evaluation: About each Example and the comparative example, 30 samples were shape | molded on the same conditions, the external appearance was observed and the presence or absence of unfilling was confirmed. In addition, the number of defects was evaluated as “◯”, the number of defects 2 or more and 5 or less as “Δ”, and the number of defects 6 or more as “x”. .

  -Warm water conductivity: For each example and comparative example, two samples each having dimensions of 10 mm x 40 mm x 4 mm were prepared under the same conditions, and the two samples were immersed in 50 g of ion-exchanged water and added. It was kept at 150 ° C. for 168 hours in a pressure vessel. Next, the conductivity of the ion-exchanged water after the treatment was measured using a conductivity meter (CONDUCTIVITY METER ES-12).

  The results are shown in Table 1.

  As is clear from these results, in Examples 1 to 12 containing activated carbon, molded articles having high water absorption were obtained while maintaining properties such as conductivity. In Examples 1, 2, 4, and 5, in which the purity of the activated carbon is particularly high and the content of the activated carbon is in the range of 5 to 10% by mass, the water absorption is particularly high and high conductivity is maintained. Furthermore, the moldability was also excellent. On the other hand, in Comparative Examples 1 and 3 in which activated carbon is not used, sufficient water absorption is not obtained, and in Comparative Example 2 in which alumina aerosil which is an insulating porous material is used instead of activated carbon, water absorption is achieved. However, the conductivity was significantly reduced.

An example of a fuel cell separator is shown, (a) and (b) are perspective views.

Explanation of symbols

  1 Fuel cell separator

Claims (2)

A fuel cell separator produced by molding a composition for a fuel cell separator containing a thermosetting resin containing at least one of a phenol resin and an epoxy resin, and graphite particles,
The fuel cell separator composition contains activated carbon as a part of the graphite particles, and the graphite particles other than the activated carbon are natural graphite having an average particle diameter of 3 to 150 μm,
The whole fuel cell separator is formed from the fuel cell separator composition,
A fuel cell separator comprising activated carbon in a range of 5 to 10% by mass . 2. The fuel cell separator according to claim 1 , wherein the water absorption is 1% or more when exposed to an atmosphere of 105 ° C. and 100 RH for 500 hours.