WO1999049530A1

WO1999049530A1 - Separator for fuel cell and method for producing the same

Info

Publication number: WO1999049530A1
Application number: PCT/JP1999/001349
Authority: WO
Inventors: Hiroyuki Tajiri; Satoshi Yamaguchi; Naoto Yoshinaga; Yoshiteru Nakagawa
Original assignee: Osaka Gas Company Limited; Kanebo, Ltd.
Priority date: 1998-03-20
Filing date: 1999-03-18
Publication date: 1999-09-30

Abstract

A separator containing a noncarbon resin and having a volume resistance in the direction of the thickness is 0.15 Φcm or less and a bending strength of 3 to 20 kgf/mm2, and such a separator further having a thermal conductivity in the direction of the thickness is 2 to 60 W/mK. Such a separator can be produced by a method (a) in which a mixture of a resin and an electroconductive agent consisting of a spherical graphite powder or of a graphite powder having an aspect ratio of 2.0 or less is injection-molded or compression-molded or by a method (b) in which a synthetic resin molded piece and an electroconductive member are molded integrally. Therefore, without passing through a carbonizing step and a cutting step, a separator having excellent electrical conductivity, thermal conductivity, mechanical strength, and dimensional precision of groove can be produced by molding.

Description

Description: Separation element for fuel cell and method for producing the same

The present invention relates to separation in a fuel cell (particularly, a polymer electrolyte fuel cell) and a method for producing the same. Background art

A fuel cell, for example, a solid polymer fuel cell uses a solid polymer membrane (such as a Nafion membrane of DuPont or a Dow chemical of Dow Chemical) as an electrolyte membrane, and has a thickness of 0.1 on both sides of the electrolyte membrane. A porous graphite paper of about 0.3 mm is provided, and a platinum alloy catalyst is supported as an electrode catalyst on the surface of the paper. Outside the graphite vapor, a porous graphite plate having a thickness of about 1 to 3 mm and a dense carbon plate having a thickness of about 0.5 mm are provided with grooves serving as gas flow paths. A cell is constructed by sequentially arranging flat plate separators, or a separate carbon plate, which is a dense carbon plate with a thickness of about 1 to 3 mm with grooves formed as gas passages, Make up.

The plate separator is required to have gas impermeability to oxygen and hydrogen, electric conductivity, heat conductivity, mechanical strength, acid resistance and the like. In addition, in the case of a grooved separator, in addition to the performance required for a flat plate separator, it is required that the dimensional accuracy of the gas flow path be high.

Such separators are manufactured by forming a flat plate by carbonizing or graphitizing a molded plate of phenolic resin and graphite powder, or by forming grooves on the surface of the flat plate by cutting. It is also manufactured using petroleum or coal pitch instead of phenol resin.

However, high conductivity of the thickness direction in the evening separator (e.g., 1 0 ¹ ~ 1 0- ³ Ω cm approximately conductivity) is required. Therefore, as described above, it is necessary to eliminate the low conductivity of the phenol resin and the pitch by carbonizing the formed plate of the phenol resin pitch and the graphite powder. That is, the carbonization process is required for the production of the separator, and a molded article containing an unfired (ie, non-carbonaceous) resin cannot attain the electrical conductivity that can be used for a fuel cell separator. However, the reason for this process is that the yield decreases due to cracking of the plate after carbonization, etc., and both flat plate separation and grooved separation separation require cutting due to shrinkage of the plate after carbonization. Therefore, the cost is very high. In addition, the carbonization process often impairs gas impermeability.

Therefore, an object of the present invention is to provide a fuel cell separator (particularly a solid polymer) having excellent properties such as gas impermeability, electrical conductivity, thermal conductivity, mechanical strength, and acid resistance without undergoing a carbonization step. And a method for manufacturing the same.

Another object of the present invention is to provide a fuel cell capable of forming grooves (gas flow paths) with high dimensional accuracy in addition to characteristics such as high electrical conductivity and thermal conductivity by molding without going through a carbonizing step and a cutting step. It is an object of the present invention to provide a method for producing a separator for a fuel cell (particularly a separator for a polymer electrolyte fuel cell). Disclosure of the invention

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have formed a non-carbonaceous resin (particularly, a combination of a resin and a specific conductive agent) or a resin molded body and a conductive member. When they were formed together, they found that a high-performance separator could be obtained without going through the carbonization and cutting steps, and completed the present invention.

That is, the separator for a fuel cell of the present invention (particularly, a synthetic resin composite separator for a polymer electrolyte fuel cell) contains a non-carbonaceous resin and has a large thickness. The volume resistivity of the viewing direction 0. 1 5 Ω cm or less, the bending strength is 3~ ² 0 kgf Z mm 2. The thermal conductivity in the thickness direction of the separator may be about 2 to 60 WmK. Such separations consist of (a) non-carbon resin, at least one conductive agent selected from spherical graphite, graphite powder with an aspect ratio of 2.0 or less, and conductive carbon black. Included is the separation of molded synthetic resin composites. Further, the separation includes a separation consisting of (b) a synthetic resin molded body and a conductive member integrated with the molded body. Separation (b) may have the same characteristics as described above. The separator (a) can be manufactured by injection molding or compression molding, and the separator (b) can be manufactured by integrating a synthetic resin molded body and a conductive member by molding.

“Non-carbonaceous resin” means a resin selected from thermosetting resin and thermoplastic resin, and is, for example, heat-treated at a temperature of 700 ° C. or less (particularly 500 ° * or less). Carbonized or graphitized resin fired at a temperature of 700 or more (especially 500 or more). The synthetic resin molded product is a molded product of a non-carbonaceous resin, or a molded product composed of a non-carbonous resin and a conductive agent, and if necessary, carbon fibers. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view showing an example of a fuel cell separator according to the present invention. FIG. 2 is a schematic sectional view showing another example of the fuel cell separator of the present invention. FIG. 3 is a schematic sectional view showing still another example of the fuel cell separator of the present invention. FIG. 4 is a schematic sectional view showing another example of the fuel cell separator of the present invention. FIG. 5 is a schematic sectional view showing still another example of the fuel cell separator according to the present invention. FIG. 6 is a schematic sectional view showing another example of the fuel cell separator of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The separator for a fuel cell of the present invention is characterized by having a small volume resistance in the thickness direction and a high bending strength without going through a carbonization or graphitization step. The volume resistance in the thickness direction of the separator is 0.15 Qcm or less (e.g., 0.000 0 1 to 0.15 Qcm), preferably 0.00 0 1 to 0.1 Q. cm, more preferably about 0.001 to 0.08 Ωcm. Flexural ^{strength, 3~ 2 0 kgf / mm 2} , preferably 5~ ² 0 kgf / mm 2, more preferably 1 0~ 2 0 kgi Z mm ^ extent.

Further, the thermal conductivity in the thickness direction of the separator is 2 to 60 WmK, preferably 3 to 60 WZmK, and more preferably about 5 to 60 W / mK.

The thickness of the separator is, for example, 0.5 to 3 mm, preferably about 0.8 to 2.5 mm, and the bulk density is a range that does not impair the gas barrier properties, for example, 1.1 to 2. It is about 2 gZcm ³ .

Among the separations for fuel cells, separations) and (b) are unfired (uncarbonized and non-graphitized) and are at least one type of resin selected from thermosetting resins and thermoplastic resins. (Binder) is composed of non-carbonaceous resin. Examples of the thermosetting resin include a phenol resin, a copna resin (a resin obtained by reacting an aromatic aldehyde and an aromatic compound), a furan resin, an epoxy resin, a polyimide, a resin, and an amino resin. (Melamine resin, urea resin, etc.) and unsaturated polyester resin. These thermosetting resins can be used alone or in combination of two or more.

Among these thermosetting resins, phenolic resins are excellent in heat resistance, acid resistance, strength, hot water resistance, and cost. The phenolic resins include ordinary resole resins, novolak resins, phenolic resins formed by a specific reaction of phenols with aldehydes, and phenolic resins formed by the reaction of phenols with aldehydes and nitrogen-containing compounds. Hue Also includes phenolic resins (copolymerized phenolic resins).

The phenolic resin obtained by the specific reaction between the above phenols and aldehydes and a method for producing the same are disclosed in Japanese Patent Publication No. Sho 62-32111. ) A concentration of 5 to 28% by weight, a formaldehyde (HCHO) concentration of 3 to 25% by weight, and a total concentration of hydrochloric acid and formaldehyde of 15 to 40% by weight in a formaldehyde hydrochloride bath. (2) The phenols are brought into contact with each other while maintaining the phenols in a specific ratio. (3) The contact causes turbidity of the phenols, and then the contact is carried out so as to form a granular or powdery solid. By maintaining the temperature in the reaction system at 45 or less during this contact, a granular or powdery resin can be obtained. The resin solid may be separated from the reaction mixture, washed with water, and neutralized with an aqueous alkali solution (aqueous solution containing a base such as alkali metal hydroxide and ammonia).

The above phenols, phenol, Metakurezo Ichiru, other Hue Nord compound (o-cresol, m- cresol, p- cresol, bi Sufueno Ichiru eight, o-, m- or p-C ₂ _ ₄ alkyl phenols , P-phenylphenol, xylenol, hydroquinone, resorcinol, etc.).

The obtained phenolic resin is (1) substantially composed of carbon, hydrogen, and oxygen atoms, and (2) a methylene group, a methylol group, and a phenol group residue having three functions as main binding units. Contained, the trifunctional phenolic residue binds to the methylene group at one of the 2, 4 and 6-positions, and at least one other to the methylene group and Z or the methylol group. are doing. (3) In the infrared absorption spectrum by the KBr tablet method, the absorption intensity at ₁₆₀ cm ^_1 (absorption peak attributed to benzene) is set to D _1600, and the absorption intensity at 900 cm; the absorption intensity at ^_1 D ₉ g ₀ _ ₁₀₁₅ the maximum absorption intensity at (absorption peak attributable to the main Chiroru group), 8 9 0 cm- ¹ (absorption peak of the isolated hydrogen atoms of the benzene nuclei) was D _8Go When D ₉₉₀ — ₁₀₁₅ / D ₁₆₀₀ = 0.2 to 9.0 (good Preferably about 0.2 to 5, more preferably about 0.3 to 4), D _{89 ()} ZD ₁₆₀₀ = O.09 to 1 · 0 (preferably 0:! To 0.9, more preferably 0.12 to 0.8).

Further, the powdery phenol resin contains (Α) spherical primary particles having an average particle diameter of 0.1 to 150 and secondary clots, and (B) at least 50% by weight of (C) The free phenol content by liquid chromatography is 50 to 500 ppm (preferably 400 ppm or less, more preferably 300 ppm or less). ppm or less).

The solubility of the resin in methanol is 20% by weight or more (preferably 30% by weight or more, more preferably 40% by weight or more). As the thermoplastic resin, for example, a polyolefin-based resin (polypropylene) Resin, ethylene-propylene copolymer, etc.), polyester-based resin (polyalkylene terephthalate, polyalkylene naphthate or their copolyester, polyarylate, etc.), polycarbonate resin (bisphenol A-type polycarbonate) Styrene-based resin (such as styrene alone or copolymer), and acrylic resin (alone or copolymerized with acryl-based monomer such as methyl methacrylate). ), Polyamide resin (Polyamide 6, Polyamide 66, Polyamide 610, etc.) Examples include phenylene ether resin, polyphenylene sulfide resin, polyester terketone resin, polysulfone resin (polysulfone resin, polyethersulfone resin, etc.) These thermoplastic resins may be used alone or Two or more can be used in combination.

As the conductive agent, at least one selected from spherical graphite, graphite powder having an aspect ratio of 2.0 or less, and conductive carbon black (such as furnace black) can be used.

Examples of spheroidal graphite include graphitized mesocarbon microbeads, spheroidized natural and artificial graphite, Flutcox, and Gilsonie. And tocokes.

For example, mesocarbon microbeads (hereinafter referred to as MCMB) are spheres (mesophase small spheres) with highly oriented crystals and a structure similar to graphite. The average particle size of the spherical MCMB is usually 5 to 50 m (e.g., 5 to 25 m), preferably 10 to 40 m (e.g., 10 to 25 tim), particularly 10 to 50 m. It is about 30 Aim. MCM B is formed by heating bituminous substances such as coal tar, coal rubbit, and heavy oil at a temperature of about 300-500. Such a method for producing MCMB is described in, for example, Japanese Patent Publication No. 11-27968 and Japanese Patent Publication No. Hei 1-264691. Graphitized MCMB is a graphitized version of MCMB in the usual way.

Examples of the graphite powder include natural and artificial graphite powder having an aspect ratio of 2.0 or less (1 to 2.0). The average particle size of the graphite powder is, for example, 2 to 35 / zm, preferably It is about 5 to 30 m. Artificial graphite powder is obtained by using petroleum coke or the like as a raw material, molding, firing, and further graphitizing at a high temperature of 2000 or more.

By using such a graphitized product of MCMB and / or graphite powder, conductivity can be effectively imparted over the course of separation. In addition, since the shape of the conductive agent is spherical or the aspect ratio is 2.0 or less, not only can the composition ratio of the conductive component to the resin be increased, but also the internal stress during molding is reduced, and stress strain remains. It is hard to be warped or deformed during separation.

The ratio of the resin to the conductive agent is in a range that does not impair the conductivity, mechanical strength, thermal conductivity, etc., for example, the former / the latter = 20 to 80 to 50 Z50 (weight ratio), preferably Is 20 Z 80 to 40 Z 60 (weight ratio), more preferably 20 Z 80 to 35 Z 65 (weight ratio), especially 280 to 30 Z 70 (weight ratio) Ratio) range. If the content of the conductive agent is less than 50% by weight, the electrical conductivity and the thermal conductivity decrease, and if it exceeds 80% by weight, the bending strength decreases and the gas permeability also increases. The composite material composed of the resin and the conductive agent may further contain carbon fibers. The type of carbon fiber is not limited, and petroleum-based or coal-based pitch-based carbon fiber, PAN (polyacrylonitrile) -based carbon fiber, rayon-based carbon fiber, phenol resin-based carbon fiber, and the like can be used. The average fiber diameter of the carbon fibers can be selected from the range of, for example, 0.5 to 50 zm, preferably 1 to 30 um., And more preferably 5 to 20 m. The average fiber length of the carbon fibers can be appropriately selected and is, for example, about 10 m to 5 mm, and preferably about 20 m to 3 mm. The amount of carbon fiber used can be selected from the range of about 1 to 10% by weight of the whole composite material constituting Separé. If the carbon fiber content exceeds 10% by weight, the airtightness is reduced and the gas permeability is increased.

As described above, a synthetic resin composite material composed of a resin, a conductive agent, and, if necessary, carbon fiber, etc., may be provided with a coupling agent, a release agent, a lubricant, a plasticizer, a curing agent, a curing aid, if necessary. A stabilizer and the like may be appropriately blended.

Such a separator (a) can be produced by a conventional molding method for a composite material, for example, injection molding or compression molding. In injection molding, the resin, the conductive agent, and if necessary, a composite material component composed of carbon fiber are melt-kneaded (prepared as necessary and melt-kneaded), and injection-molded into a predetermined mold. A flat plate separator can be manufactured. For example, when a thermosetting resin is used, in the compression molding, for example, at a pressure of about 20 to 100 kg / cm ² and a temperature of about 100 to 300, the composite material component is placed in a mold. By heating and pressing under pressure, a flat separator can be manufactured.

The separation (b) of the separation for the fuel cell is composed of a synthetic resin molded body and a conductive member integrated with the molded body. The synthetic resin molded body may be formed of the resin alone, and as in the case of the separator (a), a synthetic resin composite material (conductive composite) composed of a resin, a conductive agent, and, if necessary, carbon fiber. Material). In the separation (b), the type and form of the conductive member are not particularly limited, and a coating (such as a conductive coating film), a fibrous conductive member (a conductive fiber such as a metal fiber or a carbon fiber, or a strand thereof) may be used. ), Thin-film conductive members (conductive films and sheets, metal foil, etc.), flat conductive members (metal plates, etc.), rod-shaped conductive members (metal rods, pins, etc.). The volume resistivity of the conductive member, for example, as a 1 0 ^{_ 5} to 1 0 "may be about ² Omega cm. The conductive member, a metal, e.g., Al Miniumu, copper, gold, silver, and platinum .

The separation (b) includes various aspects, for example, (b-1) a separation for a fuel cell in which at least one surface of a synthetic resin molded body is covered with a conductive member; (b-2) At least one side or inside of the synthetic resin molded body includes a separator for a fuel cell having a closely adhered or embedded conductive member. In the former separation (b-1), the conductive member is often a conductive film or a thin-film conductive member. In the latter separation (b-2), the conductive member is a flat conductive member ゃ rod-shaped conductive member. It is often a member, and the conductive member may be at least partially embedded in the synthetic resin molded body.

In the method of the present invention, the fuel cell separator (b) can be manufactured by integrating a synthetic resin molded body and a conductive member by molding. More specifically, molding is performed using a compression molding machine including a flat mold (female mold) having a cavity and a mold (male or core) corresponding to the cavity and having an uneven portion. At this time, a step of disposing a conductive member (such as a conductive sheet) on a portion of the mold corresponding to at least one side (one side or both sides) of the molded body; By performing the pressing step, a separator having at least one surface covered with a conductive member or a separator having at least one surface closely adhered to a conductive member can be manufactured. The conductive member may be provided so as to be peelable from the mold, and may be provided (or adhered) using an adhesive if necessary. Further, the conductive member can be disposed on the cavity side and the Z or core side of the mold. . Further, instead of disposing the conductive member, a step of applying a conductive member (such as a conductive resin composition) to at least a portion of the mold corresponding to one side (one side or both sides) of the molded body is adopted, It is also possible to manufacture a fuel cell separator by passing a synthetic resin or the above composite material into the cavity and pressurizing the same. The conductive resin composition may be in the form of a conductive paint or the like, and may be releasably applied to the cavity side and / or the core side of the mold.

Further, a step of previously setting a conductive member (such as a conductive metal plate) on at least a portion corresponding to at least one side or the inside of the molded body in the mold, and filling the cavity with a synthetic resin or the composite material, Through a step of integrating with a member (such as a metal plate), a fuel cell separator in which a conductive member is integrated on one side or inside of a molded body can be manufactured.

In these methods, even if the separation itself is not conductive or lacks conductivity, only both sides including the separation side or the opposite side that comes into contact with the porous graphite paper carrying the catalyst are used. By increasing the conductivity, the transfer of electrons in the catalyst phase can be performed smoothly on the evening surface of the separator through porous graphite paper. Further, by using a resin composition imparted with conductivity (the conductive composite material) instead of the synthetic resin, the electrical resistance of the separator can be further reduced.

The pressure molding can be performed according to a conventional method according to the type of the resin, for example, when a thermosetting resin is used, at a pressure of S O L O O O K g Z cm at a temperature of about 100 to 300. In addition, compression molding, transfer molding, and the like can be used for pressure molding, and insert molding can also be applied to these molding methods.

Furthermore, in order to increase the conductivity in the thickness direction of the separator, a conductive member is disposed on at least one of the mold side and the core side (usually, the cavity side), and the mold is made of a synthetic resin or the composite material. And insert the conductive insert (insert pin, insert plate, etc.) into one of the mold side (usually the core side) and the other side (usually the cavity side). The conductive insert may be buried in the thickness direction of the separator.

FIG. 1 is a schematic sectional view showing an example of a fuel cell separator according to the present invention. In this example, the fuel cell separator is provided with a conductive metal foil 3 having an uneven cross section and a conductive insert bin 2 standing up at predetermined intervals in a plurality of recesses of the conductive metal foil. The conductive metal foil 3 and the conductive insert bin 2 are integrated with the resin molded body 1. One end face of the conductive insert pin 2 is electrically connected to the conductive metal foil 3, and the other end face is exposed on the flat surface of the resin molding 1. In such a separator for fuel cells, conductive metal foil (aluminum foil, platinum foil, etc.) 3 is temporarily fixed along the concave / convex grooves on the core side of the mold in a concave / convex section, and a plurality of conductive inserts are used. A pin (such as an aluminum insert bin) 2 can be obtained by inserting the resin 1 into a plurality of projections on the core side of the mold at predetermined intervals, standing up, and then putting the resin 1 into the mold and molding. The resin 1 may be a thermosetting resin or a thermoplastic resin, and is typically a phenol resin. The molding is performed by filling the resin 1 with the conductive metal foil (aluminum foil, platinum foil, etc.) 3 present on either the cavity side or the core side of the mold, and then performing pressure molding. be able to. The conductive insert pin (aluminum insert pin) 2 can be inserted in the thickness direction of the separator by contacting the conductive metal foil 3 to impart conductivity in the thickness direction.

FIG. 2 is a schematic sectional view showing another example of the fuel cell separator of the present invention. This fuel cell separator is the same as the separator shown in FIG. 1 except that the sheet-shaped conductive metal foil 3 is located on the surface opposite to the conductive metal foil 3 having the uneven cross section. Both end surfaces of the pin 2 are in contact with the conductive gold foil 3 on both sides, and the conductive gold foil 3 on both sides and the conductive insert pin 2 are integrated with the resin molding 1. Such fuel cell separators are located on the core and cavity sides of the mold. Then, a conductive metal foil with an uneven cross section and a sheet-shaped conductive metal foil (aluminum foil, platinum foil, etc.) 3 are fixed, and an aluminum insert bin 2 is inserted into the convex part of the core, and the resin It can be obtained by molding by adding 1. The conductive metal foil 3 can be integrated on both sides of the separator as it is formed.

FIG. 3 is a schematic sectional view showing still another example of the fuel cell separator of the present invention. This fuel cell separator has a plate-shaped resin molded product 1 having an uneven groove formed on one surface, a conductive paint 4 formed on the uneven surface of the resin molded product, It is composed of a conductive insert pin 2 that extends in the thickness direction upon contact, and a resin molded body 1, a conductive paint 4, and a conductive insert bin 2 are integrated. Further, the conductive insert bins 2 are respectively arranged in adjacent grooves of the resin molded body 1. One end face of the conductive insert pin 2 is arranged on the bottom of the adjacent concave groove of the resin molded body 1 in contact with the conductive paint 4, and the end face of the insert bin 2 is formed of the resin molded body. It is exposed on 1 flat surface. Such a separator for fuel cells is prepared by applying a conductive paint (Dohite, manufactured by Fujikura Kasei Co., Ltd., etc.) 4 to the core of the mold by brushing or the like in a releasable manner. It can be obtained by inserting a conductive insert pin (aluminum insert pin) 2 in the thickness direction and adding resin 1 and molding. The molding was performed in the same manner as the fuel cell separator shown in Fig. 1, except that a conductive paint was applied to the core grooves instead of fixing the conductive metal foil along the core grooves. You can get it. Also, the conductive insert pins 2 are erected in the mold to form the resin molded body 1 having the concave and convex grooves on one surface, and the conductive paint 4 is coated on the concave and convex surface of the obtained resin molded body 1. By coating, a separator for a fuel cell having the above structure can be obtained.

FIG. 4 is a schematic sectional view showing another example of the fuel cell separator of the present invention. This fuel cell separator is the same as the fuel cell separator shown in FIG. 3 except that a resin molded body 1 having an uneven groove on one surface is provided. A conductive paint 4 formed on both surfaces of the resin molded article, and a conductive insert bin 2 that is in contact with the conductive paint on both surfaces and whose axis extends in the thickness direction. Such a fuel cell separator having conductivity on both sides is coated with a conductive paint (such as a metal sheet) 4 on the mold side and the core side in a releasable manner. Insert the resin by inserting the conductive insert pin into the mold, and insert the resin 1 into the mold, and then raise the conductive insert bin 2 in the mold to form a resin with an uneven groove on one surface. It can be obtained by molding the body 1 and applying the conductive paint 4 to both sides of the obtained resin molded body 1.

FIG. 5 is a schematic sectional view showing still another example of the fuel cell separator of the present invention. This fuel cell separator is composed of a conductive resin molded body 5 having an uneven groove formed on one surface, and a conductive plate material (eg, an aluminum plate) 6 integrated with a flat surface of the molded body. I have. Separators having such a structure can be obtained by temporarily fixing a conductive plate material (such as an aluminum plate) 6 to the mold cavity side, placing conductive resin 5 in the mold, and molding. Can be. As the resin constituting the conductive resin 5, either a thermosetting resin or a thermoplastic resin can be used, and a phenol resin is a typical example. The molding can be performed by arranging the conductive plate material 6 in a mold, filling the mold with the conductive resin 5, and performing pressure molding.

FIG. 6 is a schematic sectional view showing another example of the fuel cell separator of the present invention. This separator has the same structure as that of the conductive resin molding 5 except that the conductive insert bin 2 extends in the thickness direction on the other uneven surface in order to increase the conductivity in the thickness direction. It has the same structure as the separator shown in Figure 5. The separator with such a structure has a conductive plate (aluminum plate, etc.) 6 temporarily fixed on the mold cavity side, and a plurality of conductive insert pins (aluminum insert pins) on the core side protrusion. Etc.) 2 can be obtained by inserting the conductive resin 5 into the mold and press-molding. Industrial applicability

According to the method of the present invention, a high-performance separator can be produced by molding without going through a carbonizing or graphitizing step and a cutting step. Therefore, a grooved separator can be obtained with high precision by using a mold having a convex portion (protrusion) or a groove formed on at least one of the cavity side and the core side (particularly, the core side). be able to.

Furthermore, the separator of the present invention is excellent in various properties such as gas impermeability, electric conductivity, heat conductivity, mechanical strength, and acid resistance without undergoing a carbonization step or a cutting step, and is excellent in a fuel cell, particularly a solid state. It is useful as a separator for polymer electrolyte fuel cells using a polymer membrane as the electrolyte membrane. In particular, when a phenolic resin is used, it is excellent in heat resistance, acid resistance, strength, hot water resistance, and cost. According to the method of the present invention, a groove (gas flow path) having high dimensional accuracy can be formed by molding without going through the carbonizing step and the cutting step, in addition to the properties such as high conductivity and thermal conductivity. Therefore, the present invention can be effectively applied to a fuel cell separator (particularly, a polymer electrolyte fuel cell separator using a solid polymer membrane as an electrolyte membrane). Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

In the examples and comparative examples, the measurement of various physical properties was performed according to a conventional method. The surface condition was visually judged by a skilled person.

Examples 1 to 5

Phenol resin (manufactured by Kanebo Co., Ltd .: Bellpearl S890) and graphitized MCMB (manufactured by Osaka Gas Co., Ltd., average particle size: 10 jm and 25 μm) or artificial graphite powder (Chuetsu Graphite Co., Ltd.) ), RA 15, aspect ratio 1.3, average particle size 5 m) and the composition shown in Table 1 (33. 3: 6.6.7 or 25.0: 75.0) using a mixer for 10 minutes. This powder mixture was charged into a mold and molded under the conditions of a molding pressure of 5 O kg / cm ² and 160 × ²⁰ minutes. In Example ₅ , 2 parts by weight of carbon fiber (Donacarb S, average fiber length 3 mm, manufactured by Donac Co., Ltd.) was used per 100 parts by weight. The results are shown in Table 1.

Comparative Example 1

In place of the graphitized MC MB, soil graphite powder with an aspect ratio of more than 2 (manufactured by Nippon Graphite Industries, Ltd .: CP, aspect ratio 2.5, average particle size 5 ^ m) was used. The molding was performed in the same manner as in Example 1.

Examples 6 to 9

Polyphenylene ether resin (PPE resin, manufactured by Mitsubishi Engineering-Plastics Co., Ltd .: Upies NX-700N) and graphitized MCM B (Osaka Gas Co., Ltd., average particle size 1 0 m and 25 m) or artificial graphite powder (manufactured by Chuetsu Graphite Co., Ltd., RA 15, aspect ratio 1.3, average particle size 5 / zm) shown in Table 2 (25 parts by weight ratio). : 7 5 or 22.2: 7.7.8) and dry-mixed for 10 minutes using a mixer. The powder mixture was supplied to an extruder to prepare a pellet. Flat plates were formed by injection molding using the prepared pellets. The results are shown in Table 2.

Comparative Example 2

In place of the graphitized MCMB, an example using soil graphite powder with an aspect ratio of 2 (manufactured by Nippon Graphite Industries, Ltd .: CP, aspect ratio 2.5, average particle size 5 m) was used. Molding was performed in the same manner as in 6. A fine compact was not obtained. Table 2

Example 10-: I 1

An aluminum foil (thickness: 30 m) or a platinum foil (thickness: 30 m) is set on the cavity side or both sides of the flat mold with a small amount of adhesive, and on the core side to impart conductivity in the thickness direction. After inserting a plurality of aluminum insert bins (2 ηΐΓΏ φΧ 1.5 mm x 4) in the thickness direction, the phenolic resin used in Examples 1-4 (manufactured by Kanebo Co., Ltd.) was inserted into the mold. : Only Bellpearl S890) was added and molded under the same molding conditions as in Examples 1 to 5. The results are shown in Table 3.

Example 12: L3

Conductive paint (Fujikura Kasei Co., Ltd., Doyu It) is brush-coated on the core side. In order to provide conductivity in the thickness direction, an aluminum insert plate (thickness: 1.0 mm) having a plurality of protrusions (pins) is inserted on the cavity side, fixed, and then inserted into the mold. Only the phenolic resin (manufactured by Kanebo Co., Ltd .: Bellpearl S890) used in Examples 1 to 4 was put into the mold, and molded under the same molding conditions as in Examples 1 to 5. The results are shown in Table 3.

Comparative Example 3

Without using an aluminum insert (conductive member), only phenolic resin (manufactured by Kanebo Co., Ltd .: Bellpearl S890) was inserted and molded under the same conditions as in Examples 10 to 13. Table 3

Examples 14 to 17

An aluminum plate (0.5 mm thick) was previously inserted into the mold cavity side and fixed, and then the powder mixture (composite material) of Examples 1 to 4 was filled in the same manner to form a plurality of continuous pieces. Molding was performed using a core with convex portions formed in parallel, and a separator with grooves was obtained. Table 4 shows the results. Table 4

Example 18

Phenolic resin (manufactured by Kanebo Co., Ltd .: Bell Pearl S890) 33.3 parts by weight and graphitized MCMB (manufactured by Osaka Gas Co., Ltd., average particle size: 10 m) 50.0 parts by weight and artificial A molded product was obtained in the same manner as in Example 1 except that graphite powder (manufactured by Chuetsu Graphite Co., Ltd., RA 15, aspect ratio 1.3, average particle diameter 5 μιη) 16.7 parts by weight was used. . This compact has a thickness of 1.20 mm, a bulk density of 1.82 g / cm ³ , a volume resistivity in the thickness direction of 0.07 Ωcm, a bending strength of 9.2 kg / mm ² , and an apparent The thermal conductivity in the thickness direction was 6.0 W / mk, and the surface condition was good.

Example 19

25.0 parts by weight of phenolic resin (manufactured by Kanebo Co., Ltd .: Bellpearl S890) and graphitized MCMB (manufactured by Osaka Gas Co., Ltd., average particle size: 10 m) 70.0 parts by weight A molded body was obtained in the same manner as in Example 1 except that 5.0 parts by weight of furnace black (manufactured by Asahi Rikibon Co., Ltd., average particle size: 16 zm) was used. The thickness of this molded body is 1.22 mm, the bulk density is 1.85 gcm ³ , the volume resistivity in the thickness direction is 0.04 Qcm, and the bending strength is 8.6 kg / mm The apparent thermal conductivity in the thickness direction Was 7.0 W Zmk, and the surface condition was good.

Claims

The scope of the claims

1. Contains non-carbon resin and has a volume resistance of 0 in the thickness direction.

1 5 Omega cm or less, separator evening for a fuel cell flexural strength is ^{3~ 2 0 kgf _ / mm 2} .

2. The fuel cell separator according to claim 1, wherein the thermal conductivity in the thickness direction is 2 to 60 WZmK.

3. At least one non-carbon resin selected from thermosetting resin and thermoplastic resin, spherical graphite, graphite powder with aspect ratio of 2.0 or less, and conductive carbon black 3. The separator for a fuel cell according to claim 1, comprising at least one kind of conductive agent.

4. The fuel cell separator according to any one of claims 1 to 3, wherein the thermosetting resin is a phenol resin.

The 5-phenolic resin contains (i) a methylene group, a methylol group, and a trifunctional phenolic residue as a main binding unit. (Ii) In the infrared absorption spectrum by the KBr tablet method, The absorption intensity at ₁₆₀₀ cm— ¹ is D ₁₆₀₀ , the maximum absorption intensity at 990 to 1150 cm— ¹ is D ₉₉ o_1 _{() 15,} and the absorption at 890 cm ^_1 When the intensity is D ₈₉ o, D 990-1015 / D 1600 ^{= 0-2 to} 9.0, D 890

D ₁₆₀₀ = 0-09 ~: L. 0, and (ΠΪ) the free phenol content by liquid chromatography is 50-500 ppm, according to any one of claims 1-4. Separation evening for fuel cells.

6. The fuel cell separator according to any one of claims 1 to 5, wherein the spherical graphite is mesocarbon microbeads having an average particle size of 5 to 50 m.

7. The fuel cell separator according to any one of claims 1 to 6, wherein the graphite powder is a natural or artificial graphite powder having an aspect ratio of 1 to 2.

8. The fuel cell separator according to any one of claims 1 to 7, wherein the ratio of the resin and the conductive agent is the former Z latter = 280 to 550 (weight ratio).

9. The fuel cell separator according to any one of claims 1 to 8, further comprising a carbon fiber.

10. The fuel cell separator according to any one of claims 1 to 9, wherein the carbon fibers have an average fiber diameter of 0.5 to 50 wm and an average fiber length of 10 m to 5 mm.

11. The separator according to any one of claims 1 to 10, wherein the content of carbon fibers is 1 to 10% by weight based on the whole composite material made of non-carbonaceous resin.

1 2. A method for producing the fuel cell separator according to any one of claims 1 to 11 by injection molding or compression molding.

13. The fuel cell separator according to any one of claims 1 to 11, comprising: a synthetic resin molded body containing a non-carbonaceous resin; and a conductive member integrated with the molded body. evening.

1 4. A fuel cell separator composed of a synthetic resin molded body and a conductive member integrated with the molded body.

15. The fuel cell separator according to claim 13, wherein the conductive member is in the form of a film, a thin film, a fiber, a flat plate, or a rod.

16. The fuel cell separator according to any one of claims 13 to 15, wherein at least one surface of the synthetic resin molded body is covered with a conductive member.

17. The fuel cell separator according to any one of claims 13 to 16, wherein the synthetic resin molded body has a conductive member on at least one side or inside.

1 8. The method for producing a fuel cell separator according to any one of claims 13 to 17, wherein the synthetic resin molded body and the conductive member are integrated. Law.

19. The method according to claim 18, comprising a step of arranging a conductive sheet at a position corresponding to at least one surface of the molded body in the mold, and a step of pressing a synthetic resin. Production method for fuel cell separators.

20. The method according to claim 18, comprising a step of applying a conductive resin composition to at least a portion of the mold corresponding to one surface of the molded body, and a step of adding a synthetic resin and applying pressure. 19. The method for manufacturing the fuel cell separator described in 19 above.

21. It is composed of a step of setting a conductive member in advance at least on a portion corresponding to at least one surface or the inside of a molded body in a mold, and a step of filling with a synthetic resin and integrating with the conductive member. The method for producing a separator for a fuel cell according to any one of claims 18 to 20.

22. A fuel cell comprising the separator according to any one of claims 1 to 11 and 13 to 17.