JP2001052721A - Separator for fuel cell and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a fuel cell having high conductivity, thermal conductivity, mechanical strength and dimensional accuracy of its groove by forming and molding without going through a carbonizing and graphitizing process and a cutting process. SOLUTION: A separator for a fuel cell is obtained by applying injection- molding or compression-molding to a resin composition containing a conductive particle containing conductive coarse particles (graphite coarse particles and the like) having an average particle diameter (D50%) of 40-120 μm and an a non-carbonaceous resin such as a phenol resin without carbonizing and graphitizing it. The ratio of the non-carbonaceous resin is 25 w.% or less. The conductive coarse particle and a conductive fine particle (spherical graphite having a diameter of about 5-30 μm, a natural graphite particle in a flake form and the like) having a small average particle diameter can be used for the conductive coarse particle by combining them at the ratio of the former/the latter = 100/0-40/60 (weight ratio). The separator may be composed of a molding 1 of the resin composition and a conductive materials 2, 3 integrated with the molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator in a fuel cell (particularly, a polymer electrolyte fuel cell, referred to as PEFC) and a method for producing the same.

[0002]

2. Description of the Related 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 membrane of Dow Chemical) as an electrolyte membrane. A porous graphite paper having a thickness of about 0.1 to 0.3 mm is provided, and a platinum alloy catalyst is supported as an electrode catalyst on the surface of the paper. Further, on the outside of the graphite paper, a porous graphite plate having a thickness of about 1 to 3 mm in which a groove serving as a gas flow path is formed, and a flat separator of a dense carbon plate having a thickness of about 0.5 mm are sequentially formed. A cell is formed by arranging the cells, or a separator, which is a dense carbon plate having a thickness of about 1 to 3 mm and formed with a groove serving as a gas flow path, is formed.

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

As such a separator, a kneaded product of a resin alone such as a phenol resin or the like and a carbon powder is formed into a flat plate, and then carbonized or graphitized in a non-oxidizing atmosphere to obtain a carbonaceous or graphite whole. It is manufactured by forming a flat plate of quality and further forming a groove on the surface of the flat plate by cutting. In addition, instead of the phenolic resin, it is similarly manufactured using petroleum or coal-based pitch having a high carbonization yield as a binder.

[0005]

However, in addition to gas impermeability, the separator has high conductivity in the thickness direction (for example,
(A conductivity of about 10 ^-1 to 10 ^-3 Ωcm) is required. Therefore, as described above, it is necessary to eliminate the low conductivity of the phenol resin and the pitch by carbonizing the molded plate of the phenol resin and the pitch and the graphite powder. That is, the production of the separator requires a carbonization step, and a molded article containing an unfired (ie, non-carbonaceous) resin cannot attain the conductivity required for a fuel cell separator.

[0006] Therefore, as a usual method, the formed plate is fired and carbonized in an inert atmosphere, and further subjected to a graphitization treatment by heat treatment at a temperature of 2000 ° C or higher to obtain a carbonaceous plate as a whole. .

However, this step is performed because the yield is reduced due to warpage or cracking of the carbonized plate accompanied by a polycondensation reaction, and cutting work is required for both the flat plate separator and the grooved separator. , Very expensive. Further, the carbonization step impairs gas impermeability, and thus requires further impregnation with a resin.

Accordingly, an object of the present invention is to provide a fuel cell separator (particularly a fuel cell separator having excellent properties such as gas impermeability, electrical conductivity, thermal conductivity, mechanical strength, and acid resistance without requiring a carbonization step. (Polymer type fuel cell separator) and a method for producing the same.

[0009] Another object of the present invention is to provide not only a carbonization / graphitization step and a cutting step but also a molding / molding step and a dimensional accuracy in addition to characteristics such as high conductivity and heat conductivity. It is an object of the present invention to provide a method for producing a fuel cell separator (particularly, a polymer electrolyte fuel cell separator) capable of forming a high groove (gas flow path).

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have formed a flat plate from a combination of a non-carbonaceous resin and specific graphite particles,
Furthermore, it has been found that when the composition is combined with a metallic conductive material and molded, a high-performance separator can be obtained without going through a carbonization / graphitization step and a cutting step, and the present invention has been completed.

[0011] That is, a feature of the present invention is a conductive plate composed of conductive particles and at least one non-carbonaceous resin selected from a thermosetting resin and a thermoplastic resin. At least comprises coarse particles having an average particle diameter (D50%) of 40 to 120 μm. The conductive particles may be configured by combining the coarse particles and fine particles capable of filling gaps between the coarse particles, and the ratio of the coarse particles to the fine particles may be, for example, the former / the latter = It is about 40/60 to 100/0 (weight ratio). The ratio of the non-carbonaceous resin is 25% by weight or less based on the total amount of the conductive particles and the non-carbonaceous resin, and the ratio between the conductive particles and the non-carbonaceous resin is, for example, the former / The latter can be selected from a range of about 95/5 to 75/25 (weight ratio). The conductive plate is useful as a fuel cell separator or the like. More specifically, the fuel cell separator (a) of the present invention comprises at least a composition containing graphite coarse particles having an average particle diameter (D50%) of 40 to 120 μm and a non-carbonaceous resin as essential components. Furthermore, the average particle size is smaller than the graphite coarse particles,
It is characterized by being formed of a composition containing graphite fine particles capable of filling between graphite coarse particles. Further, the fuel cell separator (b) of the present invention includes a fuel cell separator composed of a molded article of the composition and a conductive material integrated with the molded article (ie, a composition forming the separator). And a conductive material (such as a metal-based conductive material) integrally formed.

[0012] The separator (a) can be manufactured by injection molding or compression molding of the composition. The separator (b) integrates a molded body and a conductive material;
For example, it can be manufactured by integrating the composition and the conductive material by molding.

[0013] In the present specification, "graphite particles" means graphite or carbonaceous particles, and need not have a graphite structure as long as they have high conductivity. Is preferred. The term “non-carbonaceous resin” means a resin selected from a thermosetting resin and a thermoplastic resin. High quality resin
It does not include carbonized or graphitized resins fired at a temperature of 0 ° C. or higher (particularly 500 ° C. or higher).

The particle size distribution of the powder particles can be easily measured by a laser beam diffraction method, and the particle size at a cumulative degree of 20%, 50% or 80% can be obtained from the obtained cumulative particle size distribution curve. it can. Here, the particle diameter at a cumulative degree of 50% is represented by a symbol D50%, and is referred to as an average particle diameter. Further, the spread of the particle size distribution can be represented by a ratio between a particle size (D20%) at a cumulative degree of 20% and a particle size (D80%) at a cumulative degree of 80%, and the ratio (D80% / D20%) is defined as the uniformity degree. Call. If the numerical value of this degree of uniformity is large, it indicates a broad particle size characteristic composed of various particles from a large particle size to a small particle size, and if this numerical value is small, it indicates that the particle size characteristic is a uniform particle size. .

In the following description, a conductive plate or a fuel cell separator may be simply referred to as a plate or a separator.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Plate or Separator of the Invention
(Especially, separators for polymer electrolyte fuel cells, etc.) are characterized by low volume resistance in the thickness direction and high flexural strength, despite the non-carbonaceous resin, without undergoing the carbonization or graphitization process. There is. The volume resistance in the thickness direction of the plate or the separator is 0.001 to 0.05 Ωcm, preferably 0.001 to 0.03 Ωcm (for example, 0.001 to 0.03 Ωcm).
1 to 0.025 Ωcm). The thermal conductivity in the thickness direction of the separator is 2 to 60 W / mK, preferably 3 to 6 W / mK.
It may be 0 W / mK, more preferably about 5 to 60 W / mK.

The apparent density of the separator is, for example, 1.
7 to 2.1 g / cm ³ , preferably 1.8 to 2.1 g / cm ³
cm ³ (for example, 1.8 to 2 g / cm ³ ).

Further, the bending strength of the separator is 3 to 2
0 kgf / mm ^2, preferably 5~20kgf / mm ² approximately, the thickness of the separator is, for example, 0.5-3 m
m, preferably about 0.8 to 2.5 mm.

Fuel cell separators (a) and (b)
Is made of a non-carbonaceous resin which is unfired (uncarbonized and non-graphitized) and is at least one resin (binder) selected from a thermosetting resin and a thermoplastic resin.

[Non-carbonaceous resin] As the thermosetting resin,
For example, 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 resin, an amino resin (a melamine resin, a urea resin, and the like) can be exemplified. These thermosetting resins can be used alone or in combination of two or more.

Among these thermosetting resins, phenol resins are excellent in heat resistance, acid resistance, strength, hot water resistance and cost. Phenol resins include ordinary resol resins, novolak resins, phenol resins formed by a specific reaction of phenols and aldehydes, and phenol resins formed by the reaction of phenols, aldehydes and nitrogen-containing compounds (copolymerization). Phenolic resin).

A phenol resin obtained by the above-mentioned specific reaction of phenols and aldehydes and a method for producing the same are disclosed in Japanese Patent Publication No. Sho 62-30221, and (1) a hydrochloric acid (HCl) concentration of 5-28. % 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.
(2) The phenols are contacted at a specific ratio while maintaining the specific ratio, and (3) the phenols are clouded by this contact, and thereafter, a granular or powdery solid is formed. The contact is performed as described above, and a granular or powdery resin can be obtained by maintaining the temperature in the reaction system at 45 ° C. or lower during this contact. The resin solid may be separated from the reaction mixture, washed with water, and neutralized with an aqueous alkali solution (an aqueous solution containing a base such as an alkali metal hydroxide or ammonia).

The phenols include phenol, meta-cresol, and other phenols (o-cresol, m-cresol
Cresol, p-cresol, bisphenol A, o
-, M- or _pC2-4 alkylphenol, p-phenylphenol, xylenol, hydroquinone, resorcinol, etc.).

The obtained phenol resin is (1) substantially composed of carbon, hydrogen and oxygen atoms, and (2) a methylene group, a methylol group, and a trifunctional phenol residue as a main binding unit. And a trifunctional phenol residue is bonded to a methylene group at one of the 2, 4 and 6-positions, and is bonded to a methylene group and / or a methylol group at at least one other position. I have. Also,
(3) In the infrared absorption spectrum by the KBr tablet method, the absorption intensity at a wave number of 1600 cm ^-1 (the absorption peak attributed to benzene) is D ₁₆₀₀ , and the wave number is 990 to 1015.
When cm ^-1 maximum absorption intensity at (absorption peak attributable to methylol group) D _990-1015, the absorption intensity at wave number 890 cm ^-1 (absorption peak of the isolated hydrogen atoms of the benzene nuclei) was D _890, D _{9 90-1015} / D ₁₆₀₀ = 0.2 to 9.0 (preferably 0.2 to 5, more preferably 0.3 to 4), D ₈₉₀ / D ₁₆₀₀ = 0.09 to 1.0 (preferably Is 0.1 to 0.9, more preferably 0.12 to 0.8)
It is about.

Further, the powdery phenol resin is
(A) containing spherical primary particles and secondary aggregates having a particle size of 0.1 to 150 μm, and (B) at least 50% by weight of the whole
Has a size capable of passing through a 100 Tyler mesh sieve, and (C) a free phenol content by liquid chromatography is usually 50 to 500 ppm (preferably 4 ppm).
00 ppm or less, more preferably 300 ppm or less).

The solubility of the resin in methanol is as follows:
It is at least 20% by weight (preferably at least 30% by weight, more preferably at least 40% by weight).

Examples of the thermoplastic resin include polyolefin resins (polypropylene resin, ethylene-propylene copolymer, etc.), polyester resins (polyalkylene terephthalate, polyalkylene naphthalate or copolyesters thereof, polyarylate, etc.), Polycarbonate resin (such as bisphenol A type polycarbonate resin), polystyrene resin (such as styrene monomer such as styrene alone or copolymer), and acrylic resin (such as (meth) acrylic monomer such as methyl methacrylate) Homopolymer or copolymer), polyamide resin (polyamide 6, polyamide 66, polyamide 610, etc.),
Examples thereof include a polyphenylene ether resin, a polyphenylene sulfide resin, a polyether ether ketone resin, and a polysulfone-based resin (such as a polysulfone resin and a polyethersulfone resin). These thermoplastic resins can be used alone or in combination of two or more.

[Conductive Particles] The conductive particles contain at least coarse particles, and the average particle diameter of the coarse particles (D50%)
Is, for example, 40 to 150 μm (for example, 50 to 125 μm).
μm), preferably 50 to 150 μm (for example, 50 to 150 μm).
125 μm), and usually about 40 to 120 μm (for example, 50 to 120 μm). Such conductive coarse particles form a conductive skeleton in a plate or a separator, and can increase the effective cross-sectional area contributing to conductivity, and even if the specific surface area is small, the amount of resin is greatly reduced, but the gas permeability is small. , Plates or separators with high integrity and high mechanical strength can be formed.

Such conductive coarse particles can be selected from various conductive particles, for example, metal and non-metal particles. Preferred conductive coarse particles are graphite particles, for example, natural graphite,
You can choose from artificial graphite. The graphite particles usually have a butanol-substituted true specific gravity of 2.1 or more (for example, 2.1 to 2.
About 3), and examples thereof include graphite particles using petroleum or coal needle coke as a raw material. The BET specific surface area of the conductive coarse particles (especially graphite particles) is usually 10 m ^2.
/ G or less (for example, 1 to 5 m ² / g), preferably 2 to 5 m ² / g.
It is about 5 m ² / g. The oil absorption by Method A (using dibutyl phthalate (DBP)) specified in JIS K 6221 is, for example, about 60 to 75 cc / 100 g.

The shape of the conductive coarse particles (such as graphite coarse particles) is not particularly limited, but is usually non-spherical and amorphous. In particular, conductive coarse particles such as graphite particles generally have a flat shape and an amorphous shape in cross section. Uniformity of particle size distribution of conductive coarse particles (especially graphite coarse particles) (D80% /
D20%) is, for example, 5 or less (that is, about 1 to 5).
And usually 1.5 to 5, preferably 2
-5, especially about 2.2-4.8.

The conductive coarse particles can be used in combination with conductive fine particles. As the conductive fine particles, various conductive particles can be used as long as they have a smaller average particle diameter than the conductive coarse particles and can be filled in the gaps between the conductive coarse particles. By filling the voids between the filled coarse particles with the fine particles, the conductivity can be greatly improved.

When the average particle diameter of the conductive coarse particles is D1, the average particle diameter of the conductive fine particles (D50%) D2
Can be selected from the range of D2 = D1 × 0.001 to D1 × 0.6, and usually D1 × 0.01 to D1 × 0.5,
Preferably D1 × 0.02 to D1 × 0.5, especially D1 ×
It is about 0.05 to D1 × 0.5.

In order to impart conductivity, the average particle diameter (D50%) of the fine particles can be selected, for example, from the range of about 0.1 to 50 μm according to the average particle diameter of the coarse particles.
It is about 1 to 50 μm, preferably about 5 to 40 μm, and more preferably about 5 to 30 μm (for example, about 10 to 25 μm).

The conductive fine particles can be selected from metal particles and non-metal particles as in the case of coarse particles, but can be generally selected from graphite particles such as natural graphite and artificial graphite. The shape of the fine particles is not particularly limited, and may be, for example, a polygonal shape such as a sphere, an ellipse, or a square, a plate shape such as a scale or a flake shape, a rod shape, an amorphous shape, and the like. Among these conductive fine particles, in order to impart filling properties and lubricity during molding,
At least one selected from spherical particles (spherical graphite) and flaky particles (flaky natural graphite particles or graphite powder) can be suitably used. Since the spherical conductive fine particles have high filling properties for the gaps between the coarse particles, the conductivity can be efficiently improved. Further, the flaky particles have a high filling property for the gaps between the coarse particles as in the case of the spherical fine particles, and are in surface contact with the conductive coarse particles functioning as a conductive skeleton, so that the conductivity can be efficiently improved.

The spherical graphite particles include graphitized products of mesocarbon microbeads (hereinafter simply referred to as MCMB), spheroidized natural and artificial graphite, fluid coke, and Gilsonite coke. Among these spherical graphite particles, MCMB is a sphere (mesophase sphere) in which crystals are highly oriented and have a structure similar to graphite. M
The average particle size of CMB is usually 5 to 50 μm, preferably 10 to 40 μm, and particularly about 10 to 25 μm. MC
MB is produced by heating bituminous substances such as coal tar, coal tar pitch, and heavy oil at about 300 to 500 ° C. Such a method for producing MCMB is disclosed, for example, in Japanese Patent Publication No. 1-29688, Japanese Patent Application Laid-Open No. 1-2426.
No. 91, for example. The graphitized product of MCMB is obtained by graphitizing MCMB by an ordinary method.

The flaky natural graphite particles (or flaky natural graphite powder) are obtained by expanding a highly crystalline natural graphite by a known method (for example, using sulfuric acid) and pulverizing it by a jet mill or the like. is there. By pulverizing the product in which the lamination structure of the graphite crystal is separated between the layers by the expansion treatment, a very flat graphite powder (scale or flaky powder) is obtained. Such a powder can be easily compressed by pressurization, and can improve the filling property. The average particle size of the flaky natural graphite particles can be arbitrarily adjusted by a pulverizing operation.

The combination of the conductive coarse particles and the conductive fine particles (especially graphite particles) enables high-density filling of graphite particles during molding, and effectively imparts high conductivity to plates and separators. Furthermore, the addition of the graphite particles having high self-lubricating properties alleviates the internal stress during molding, makes it difficult for stress strain to remain, and can prevent the plate and the separator from warping or deforming.

The ratio between the conductive coarse particles and the conductive fine particles is as follows:
Range in which high conductivity can be imparted, for example, former / latter (weight ratio) = 100/0 to 40/60, preferably 100 /
It is about 0 to 50/50 (for example, 100/0 to 60/40).

The content of the conductive coarse particles is usually 5 based on the total amount of the conductive particles and the non-carbonaceous resin.
0 to 95% by weight (preferably 55 to 90% by weight, especially 6
0 to 90% by weight), and the content of the conductive fine particles is 0 to 40%.
% (Preferably 0 to 35% by weight).

Since the conductive particles contain at least coarse particles, the specific surface area and oil absorption of the conductive particles can be reduced. Therefore, even if the content of the non-carbonaceous resin is small,
A plate (such as a separator) having high mechanical strength can be obtained, and a plate (such as a separator) having high conductivity and heat conductivity can be obtained without going through a carbonization or graphitization step.

The content of the non-carbonaceous resin is usually 25% by weight or less (preferably about 5 to 25% by weight) based on the total amount of the graphite particles and the non-carbonaceous resin. More specifically, the ratio between the conductive particles and the non-carbonaceous resin is usually the former / the latter = 95/5 to 75/25 (weight ratio), preferably 90/10 to 80/20 (weight). Ratio). With such a composition ratio, physical properties of the plate (separator) such as conductivity, mechanical strength, and thermal conductivity can be improved.

The composition (resin composite material) 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, for example, from the range of 0.5 to 50 μm, preferably 1 to 30 μm, and more preferably 5 to 20 μm. The average fiber length of the carbon fibers can be appropriately selected, for example, 10 μm to 5 mm, preferably 20 μm to 5 mm.
It is about μm 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 the separator. When the content of the carbon fiber exceeds 10% by weight, the airtightness decreases, and the gas permeability increases.

Further, in order to improve the conductivity of the non-carbonaceous resin, conductive fine particles such as conductive carbon black (furnace black, acetylene black, Ketjen black, etc.) and colloidal graphite may be contained as necessary. .

Further, a composition (resin composite material) composed of the above components may be added, if necessary, to a coupling agent,
A release agent, a lubricant, a plasticizer, a curing agent, a curing aid, a stabilizer and the like may be appropriately blended.

Such a plate (separator) (a)
Can be produced by a conventional molding method for a synthetic resin, for example, injection molding or compression molding. In the injection molding, the resin, conductive particles (graphite particles and the like), and a composite material component (resin composition) composed of carbon fibers as required are melt-kneaded (preparation of pellets as necessary and melt-kneading). A flat plate (flat separator) can be manufactured by injection molding in a predetermined mold. When using a thermosetting resin, in compression molding, for example, a pressure of 20 to 1000 kg
/ Cm ^2, at a temperature of about 100 to 300 ° C., can be produced flat plates (plate-like separator) by the composite component (resin composition) to pressure molding by heating in a mold.

The conductive plate or the fuel cell separator (b) is composed of a molded article of the resin composition containing the above components, and a conductive material integrated with the molded article. This molded body is, like the plate or the separator (a),
It may be formed of a composition composed of resin, conductive particles (eg, graphite particles), and, if necessary, carbon fiber.

In the plate or the separator (b), the type and form of the conductive material are not particularly limited, and a coating (conductive coating or the like), a fibrous conductive material (conductive fiber such as metal fiber, carbon fiber, etc.) And the like, a thin-film conductive material (conductive film, sheet, metal foil, etc.), a plate-shaped conductive material (metal plate, etc.), a rod-shaped conductive member (metal rod, pin, etc.), etc. The volume resistance of the conductive material may be, for example, about 10 ⁻⁵ to 10 ⁻² Ωcm. As the conductive material, metal, for example, aluminum,
Copper, gold, silver, platinum and the like can be mentioned.

The separator (b) has various modes,
For example, (b-1) at least one side of the molded body made of the resin composition, a fuel cell separator coated with a conductive material, (b-2) at least one side or inside of the molded body made of the resin composition, A fuel cell separator having a closely adhered or buried conductive material is included. In the former separator (b-1), the conductive material is often a conductive film or a thin film conductive material, and in the latter separator (b-2), the conductive material is a plate-shaped conductive material or a rod-shaped conductive material. In many cases, the conductive material may be at least partially embedded in the molded body.

In the method of the present invention, the fuel cell separator (b) can be manufactured by integrating a molded body of the resin composition and a conductive material by molding. More specifically, a flat mold (female mold) having a cavity,
When molding using a compression molding machine having a convex portion (core) corresponding to the cavity, a conductive material (such as a conductive sheet) is formed on a portion of the mold corresponding to at least one surface (one surface or both surfaces) of the molded body. ) And through the step of pressing the resin composition into a mold, the separator is coated on at least one side with a conductive material or the conductive material is closely adhered to at least one surface and integrated. A separator can be manufactured. The conductive material may be provided so as to be peelable from the mold, and may be provided (or adhered) using an adhesive as necessary. In addition, the conductive material can be disposed on the cavity side and / or the core side of the mold.

In place of disposing the conductive material, a step of applying a conductive material (such as a conductive resin composition) to a portion of the mold corresponding to at least one surface (one or both surfaces) of the molded body is employed. Alternatively, a fuel cell separator can be manufactured by passing the resin composition into a cavity and pressurizing the resin composition. 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 setting a conductive material (such as a thin metal plate) in advance in a portion of the mold corresponding to at least one side or the inside of the molded body, filling the cavity with the resin composition, and forming a conductive material (such as a thin metal plate) And the like, and a step of integrating the same into a molded body, a fuel cell separator in which the conductive material is integrated on one surface or inside the molded body.

In these methods, even when the conductivity of the separator itself is insufficient, only the both surfaces including the separator surface contacting the porous graphite paper carrying the catalyst or the opposite surface are made highly conductive. Thereby, the transfer of electrons in the catalyst phase can be smoothly performed on the separator surface through the porous graphite paper.

The pressure molding is carried out according to a conventional method according to the type of the resin.
It can be carried out at a temperature of about 0 to 1000 kg / cm ² and a temperature of about 100 to 300 ° C. Further, for the pressure molding, a compression molding method, a transfer molding method, and an insert molding method can also be adopted.

Further, in order to increase the conductivity in the thickness direction of the separator, a conductive material is disposed on at least one of the cavity side and the core side (usually, the cavity side) of the mold, and the resin composition is put in the cavity, and The conductive insert (insert pin, insert plate, etc.) is arranged on one of the cavity side and the core side (usually the core side) toward the other (usually the cavity side) and press-molded to form the conductive insert. It may be embedded in the thickness direction of the separator.

FIG. 1 is a schematic sectional view showing an example of the fuel cell separator of the present invention. In this example, the fuel cell separator includes a conductive metal foil 3 having an uneven cross section and conductive insert pins 2 standing up at predetermined intervals in a plurality of recesses of the conductive metal foil. Metal foil 3
The conductive insert pin 2 is integrated with a molded body 1 of a conductive resin composition containing at least the conductive particles and the non-carbonaceous resin. 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 molded body 1. In such a fuel cell separator, a conductive metal foil (aluminum foil, platinum foil, or the like) 3 is temporarily fixed in an uneven shape in a cross section along an uneven groove on the core side of a mold, and a plurality of conductive insert pins ( Aluminum insert pins, etc.) 2 are inserted upright at predetermined intervals into a plurality of protrusions on the core side of the mold,
It can be obtained by placing the conductive resin composition 1 in a mold and molding. Molding is performed by using a conductive metal foil (aluminum foil,
After filling the conductive resin composition 1 in a state where the platinum foil 3 or the like is present, it can be performed by pressure molding. 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 in order 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. In this fuel cell separator, in the separator shown in FIG. 1, a sheet-shaped conductive metal foil 3 is located on a surface opposite to the conductive metal foil 3 having an uneven cross section, and both ends of the conductive insert pin 2 are provided. The surface is in contact with the conductive metal foils 3 on both surfaces, and the conductive metal foils 3 and the conductive insert pins 2 on both surfaces are integrated with the molded body 1. Such a fuel cell separator,
A conductive metal foil having an irregular cross section and a sheet-shaped conductive metal foil (aluminum foil, platinum foil, etc.) 3 are fixed to the core side and the cavity side of the mold, respectively, and the aluminum insert pins 2 are used to project the core convexities. It can be obtained by inserting the conductive resin composition 1 into a part and molding it. The conductive metal foil 3 can be integrated on both surfaces 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 molded body 1 having an uneven groove formed on one surface, a conductive paint 4 formed on the uneven surface of the molded body, and a thickness in contact with the conductive paint. The molded body 1, the conductive paint 4, and the conductive insert pins 2 are integrated with each other. In addition, the conductive insert pins 2 are respectively arranged in adjacent grooves of the molded body 1. One end face of the conductive insert pin 2 is disposed at the bottom of the adjacent concave groove of the molded body 1 in contact with the conductive paint 4, and the end face of the insert pin 2 is exposed on the flat surface of the molded body 1. ing. In such a fuel cell separator, a conductive paint (Dotite, manufactured by Fujikura Kasei Co., Ltd., etc.) 4 is releasably applied to the core side of the mold by brushing, etc. It can be obtained by inserting an insert pin (aluminum insert pin) 2 in the thickness direction, adding the conductive resin composition 1 and molding. The molding is performed in the same manner as the fuel cell separator of FIG. 1 except that the conductive metal foil is fixed along the concave and convex grooves of the core and a conductive paint is applied to the concave and convex grooves of the core. be able to. Also, the conductive insert pin 2 is erected in the mold, and the molded body 1 having the concave and convex grooves on one surface is molded.
By applying the conductive paint 4 to the uneven surface of the above, a fuel cell separator 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 molded article 1 having an uneven groove on one surface, a conductive paint 4 formed on both surfaces of the molded article, and a conductive paint Conductive insert pin 2 that contacts the shaft and the shaft extends in the thickness direction.
And In such a fuel cell separator having both surfaces provided with conductivity, a conductive paint (such as dotite) 4 is releasably applied to the cavity side and the core side of the mold, and a plurality of conductive insert pins are attached to the metal. A method of erecting and inserting in a mold, molding the conductive resin composition 1 therein,
The conductive insert pins 2 are erected in the mold, the molded body 1 having the concave and convex grooves on one surface is molded, and the conductive paint 4 is applied to both surfaces of the molded body 1 obtained. it can.

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 a molded product 1 having an uneven groove formed on one surface.
And a conductive plate material (such as an aluminum plate) 5 integrated with the flat surface of the molded body. The separator having such a structure can be obtained by temporarily fixing a conductive plate material (such as an aluminum plate) 5 on the cavity side of the mold, putting the conductive resin composition 1 in the mold, and molding. . The molding can be performed by disposing the conductive plate material 5 in a mold, filling the mold with the conductive resin composition 1, 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 is in contact with the conductive plate 5 of the conductive molded body 1 in order to increase the conductivity in the thickness direction, except that the conductive insert pin 2 extends in the thickness direction on the other uneven surface. 5 has the same structure as the separator shown in FIG. In the separator having such a structure, a conductive plate material (such as an aluminum plate) 5 is temporarily fixed to the cavity side of the mold, and a plurality of conductive insert pins (such as aluminum insert pins) 2 are inserted into the convex portions on the core side. Then, the conductive resin composition 1 can be obtained by putting the conductive resin composition 1 in a mold and performing pressure molding.

According to the method of the present invention, the separator can be economically produced only by the molding and shaping steps at a temperature not higher than the carbonization temperature without going through the carbonizing or graphitizing step and the cutting step. Further, as a mold at the time of molding, by using a mold in which at least one of the cavity side and the core side (particularly the core side) is formed with a continuous convex portion (protrusion) or a groove, a grooved separator can be formed at low cost. It can be obtained with a high degree of accuracy.

The separator of the present invention is useful as a separator for a fuel cell, particularly for a polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte membrane.

[0063]

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 / graphitization step and a cutting step. . In particular, when a phenol resin is used, it is advantageous in terms of heat resistance, acid resistance, strength, and hot water resistance. In the method of the present invention,
A groove (gas flow path) having high dimensional accuracy can be formed in addition to characteristics such as high electrical conductivity and thermal conductivity by a molding / molding step without passing through a carbonizing / graphitizing step and a cutting step. Therefore, the present invention can be effectively applied to a fuel cell separator (particularly, a polymer electrolyte fuel cell separator).

[0064]

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

The following materials were used in Examples and Comparative Examples.

(1) Graphite coarse particles As artificial graphite, acicular coke was used as a raw material,
After subjected to graphitization at 00 ° C, by pulverizing and classifying,
The following high-purity artificial graphite powder was obtained.

(1a) Graphite coarse particles having an average particle size (D50%) of 110 μm are D20% = 73 μm and D80% = 180
μm, the degree of uniformity D80% / D20% = 2.5, the BET specific surface area was 2 m ² / g, and the oil absorption using dibutyl phthalate (DBP) was 65 cc / 100 g.
The butanol-substituted true specific gravity of the coarse graphite particles according to JIS-R-7222 was 2.24.

(1b) Graphite coarse particles having an average particle diameter (D50%) of 50 μm are D20% = 20 μm and D80% = 90 μm
And the uniformity D80% / D20% = 4.5, and B
ET specific surface area is 5m ² / g, dibutyl phthalate (DBP)
Was 70 cc / 100 g. The butanol-substituted true specific gravity of the coarse graphite particles according to JIS-R-7222 was 2.24.

(2) Fine graphite particles (2a) The average particle diameter (D50
%) Of 25 μm. These graphite fine particles have D20% = 10 μm, D80% = 42 μm,
The degree of uniformity D80% / D20% = 4.2, the BET specific surface area was 8 m ² / g, and the oil absorption using dibutyl phthalate (DBP) was 80 cc / 100 g. This graphite coarse grain J
The true specific gravity of butanol substitution according to IS-R-7222 is 2.
24. (2b) Graphitized MCMB (manufactured by Osaka Gas Co., Ltd., “MCM
(B): average particle size of 20 μm) (2c) Flaky natural graphite particles (manufactured by SSC Corporation, “S
NE-10G ": average particle diameter 10 μm)

(3) Resin (3a) Powdered phenol resin (manufactured by Kanebo Co., Ltd., “Bellpearl S890”: average particle size: 20 μm) (3b) Polyphenylene ether resin (manufactured by Mitsubishi Engineering-Plastics Co., Ltd., “UPIACE NX”) -700
0N ”) (4) Pitch-based carbon fiber (“ Donacarbo S ”manufactured by Donac Co., Ltd., average fiber diameter 13 μm, average fiber length 3 mm) (5) Conductive carbon black (manufactured by Mitsubishi Chemical Corporation, conductive carbon black) , “# 3050”: special furnace black, unit particle size 0.04 μm, DBP oil absorption 1
75 cc / 100 g) Comparative Examples 1-4 Artificial graphite 25 μm (2a), graphitized MC as fine graphite particles
MB 20 μm (2b), powdered phenolic resin (3), and conductive carbon black (5) were dry-mixed at a ratio shown in Table 1 using a mixer for 10 minutes. This powder mixture was charged into a mold and molded under the conditions of a molding pressure of 50 kg / cm ² and 170 ° C. for 20 minutes.

Examples 1 to 8 Artificial graphite particles 110 μm (1a), artificial graphite particles 50 μm (1b) as graphite coarse particles, and artificial graphite particles 2 as fine graphite particles
5 μm (2a), 20 μm (2b) of graphitized MCMB, flaky natural graphite particles (2c), and powdery phenol resin (3a) were dry-mixed for 10 minutes using a mixer at a ratio shown in Table 1. This powder mixture was charged into a mold, and a molding pressure of 50 kg / cm ² , 17
Press molding was performed under the conditions of 0 ° C. × 20 minutes.

Table 1 shows the results. Numerical values in the table indicate parts by weight.

[0073]

[Table 1]

As is clear from Table 1, in the comparative example, although a good molded product was obtained, the specific resistance in the thickness direction was 0.04 Ωcm or more, and the intended low-resistance molded product was not obtained. . On the other hand, in the examples, the surface condition of the molded body was good, and the specific resistance in the thickness direction was as high as 0.01 to 0.02 Ωcm.

Example 9 100 parts by weight of the powdery phenol resin (3a) and 100 parts by weight of the conductive carbon black (5) were dry-mixed for 10 minutes using a mixer in advance. Further, artificial graphite coarse particles 110
480 parts by weight of μm (1a), graphitized M as graphite fine particles.
120 parts by weight of 20 μm (2b) of CMB was added and dry-mixed for 10 minutes using a mixer. This powder mixture is poured into a mold,
Press molding was performed under the conditions of a molding pressure of 50 kg / cm ² and 170 ° C. × 20 minutes. As a result, the apparent density of the obtained molded plate was 1.80 g / cm ³ , and the specific resistance in the thickness direction was 0.8.
039 Ωcm.

Example 10 480 parts by weight of artificial graphite coarse particles 110 μm (1a), 120 parts by weight of graphitized MCMB 20 μm (2b) as fine graphite particles, 10 parts by weight of carbon fiber (4), powdery phenol resin
(3a) is weighed out at a ratio of 100 parts by weight, and using a mixer
Dry mixed for 10 minutes. This powder mixture was put into a mold and press-molded under the conditions of a molding pressure of 50 kg / cm ² and 170 ° C. for 20 minutes. As a result, the apparent density of the obtained molded plate was 1.88 g / cm ³ and the specific resistance in the thickness direction was 0.0.
17 Ωcm.

Example 11 100 parts by weight of polyphenylene ether resin (3b), 400 parts by weight of artificial graphite coarse particles 110 μm (1a), 100 parts by weight of graphitized MCMB 20 μm (2b) as graphite fine particles were added, and a mixer was used. Dry mixed for minutes. This powder mixture was supplied to an extruder to prepare pellets. Using the prepared pellets, a flat plate was injection molded by an injection molding machine. As a result, the apparent density of the obtained molded plate was 1.9.
0 g / cm ³ , specific resistance in the thickness direction is 0.014 Ωcm
Met.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a fuel cell separator of 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 of the present invention.

FIG. 6 is a schematic sectional view showing another example of the fuel cell separator of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Molded object 2 ... Conductive insert pin 3 ... Conductive metal foil 4 ... Conductive paint 5 ... Conductive plate material

Claims (19)

[Claims] 1. A fuel cell separator comprising graphite particles and at least one non-carbonaceous resin selected from a thermosetting resin and a thermoplastic resin, wherein the graphite particles have at least an average particle diameter. (D50%) 40-12
A fuel cell separator containing 0 μm graphite coarse particles. 2. The fuel cell separator according to claim 1, wherein the graphite coarse particles are non-spherical amorphous particles. 3. The uniformity (D80) of the particle size distribution of graphite coarse particles.
% / D20%) is 5.0 or less. 4. The graphite particles having an average particle size (D50%) of 4
A graphite coarse particle of 0 to 120 μm and a graphite fine particle having an average particle diameter smaller than the graphite coarse particle were divided into former / latter = 10
The fuel cell separator according to claim 1, wherein the separator is contained in a ratio of 0/0 to 40/60 (weight ratio). 5. When the average particle diameter of graphite coarse particles is D1, the average particle diameter (D50%) D2 of fine graphite particles is D2.
5. The fuel cell separator according to claim 4, wherein D1 × 0.05 to D1 × 0.5. 6. The fuel cell separator according to claim 4, wherein the graphite fine particles are at least one selected from spherical graphite and flaky natural graphite particles. 7. The fuel cell separator according to claim 1, wherein the content of the non-carbonaceous resin is 25% by weight or less based on the total amount of the graphite particles and the non-carbonaceous resin. 8. The fuel cell separator according to claim 1, wherein the thermosetting resin is a phenol resin. 9. A phenol resin containing (i) a methylene group, a methylol group, and a trifunctional phenol residue as main binding units, and (ii) a wave number in an infrared absorption spectrum by a KBr tablet method. 1600cm
The absorption intensity at ^-1 and D _1600, wavenumber 990~1015c
The maximum absorption intensity at m ^-1 is D _990-1015 , and the wave number is 890c.
When the absorption intensity at m ^-1 is D ₈₉₀ , D _990-1015 / D
₁₆₀₀ = 0.2 to 9.0, D ₈₉₀ / D ₁₆₀₀ = 0.09 to
9. The fuel cell separator according to claim 8, wherein (iii) the free phenol content by liquid chromatography is from 50 to 500 ppm. 10. The fuel cell separator according to claim 1, further comprising carbon fibers. 11. A fuel cell separator comprising a molded article of the composition containing the components according to claim 1 and a conductive material integrated with the molded article. 12. The fuel cell separator according to claim 11, wherein at least one surface of the molded body is covered with a conductive material. 13. The fuel cell separator according to claim 11, wherein a conductive material is provided on at least one surface or inside of the molded body. 14. A plate composed of conductive particles and at least one non-carbonaceous resin selected from a thermosetting resin and a thermoplastic resin, wherein the conductive particles have an average particle diameter (D50% ) 40-120 μm coarse particles 40-
100% by weight and 0 to 60% of fine particles that can be filled between the coarse particles, and the ratio of the conductive particles to the non-carbonaceous resin is the former / the latter = 95/5 to 75
/ 25 (weight ratio). 15. A composition containing the graphite particles according to claim 1 and at least one non-carbonaceous resin selected from a thermosetting resin and a thermoplastic resin, which is injection-molded or compression-molded. 10. A method for producing the fuel cell separator according to any one of items 9. 16. The method for producing a fuel cell separator according to claim 15, wherein the molded body and the conductive material are integrated. 17. A step of arranging a conductive sheet at a portion of a mold corresponding to at least one surface of a molded body, and a step of putting the composition according to claim 15 and pressing the same. 17. The method for producing a fuel cell separator according to item 16. 18. A method comprising the steps of: applying a conductive resin composition to at least a portion of a mold corresponding to at least one surface of a molded body; and applying the composition according to claim 15 and applying pressure. Item 17. A method for producing a fuel cell separator according to Item 16. 19. A step of previously setting a conductive material on a portion of a mold corresponding to at least one surface or the inside of a molded body, and a step of filling the composition according to claim 15 and integrating with the conductive material. The method for producing a fuel cell separator according to claim 16, wherein: