JP2002367620A - Manufacturing method of fuel cell separator - Google Patents

Abstract

(57) [Problem] To produce a fuel cell separator by heating and pressing a mixed raw material of a carbonaceous powder and a binder.
Without impairing the quality and functionality of the resulting separator,
Shorten the occupation time of the press molding machine and efficiently mass produce fuel cell separators. SOLUTION: The mixed material of the carbonaceous powder and the binder is heated in a heating furnace, and then the mixed material is introduced into a pressure molding machine to form a separator for a fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a fuel cell separator. More specifically, the present invention relates to a method for producing a fuel cell separator with high productivity by mixing a carbonaceous powder and a binder, heating the mixture, and pressing the mixture.

[0002]

2. Description of the Related Art In recent years, fuel cells utilizing the reaction between hydrogen and oxygen have attracted attention as power generation systems that respond to resource problems and environmental problems, and their practical use in various fields is being studied. The basic structure of a fuel cell is a structure in which dozens to hundreds of cells, each having an electrolyte sandwiched between porous positive and negative electrode plates and gas barrier properties and a conductive plate separator provided on both outer sides thereof, are stacked. Specifically, a ribbed electrode system in which grooves as reaction gas flow paths for hydrogen, air, etc. are engraved on the separator side surface of each positive and negative electrode plate, and a ribbed separator in which this groove is engraved on the surface of each separator There are methods.

A separator used in such a fuel cell is generally manufactured by mixing a carbonaceous powder with a binder and press-molding the mixture under heating. In particular,
After filling the molding material with the mixed raw material of the carbonaceous powder and the binder, the mixture is introduced into a pressure molding machine, heated and pressed in the pressure molding machine, cooled until the molded product is hardened, and then depressurized. . Since a pressure molding machine is generally provided with a heating means,
A series of operations of heating, pressurizing, cooling, and depressurizing are performed in the press forming machine, and the die cutting is performed outside the press forming machine. That is, in the related art, a fuel cell separator having a thickness of about 1 to several tens of mm and provided with ribs in some cases is preferably formed by preventing deformation such as warpage or swelling, and further forming In order to form a highly accurate rib, it was common sense that a series of operations from heating, pressing, cooling, and depressurization were performed in a pressing machine.

[0004]

However, heating,
In the conventional method in which a series of operations of press molding, cooling, and depressurization are performed in the press molding machine, the press molding machine is occupied during the series of operations, and particularly, productivity in mass production is remarkable. Will drop.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and heats and press-forms a mixed material of a carbonaceous powder and a binder to produce a separator for a fuel cell. The fuel cell separator can be efficiently manufactured without reducing the occupation time of the pressure molding machine without impairing the performance, and a method for manufacturing a fuel cell separator suitable for mass production of the fuel cell separator is provided. The purpose is to provide.

[0006]

A method of manufacturing a fuel cell separator according to the present invention is directed to a method of manufacturing a fuel cell separator by heating and pressing a mixed raw material of a carbonaceous powder and a binder. After the mixed raw material is heated in a heating furnace, the mixed raw material is introduced into a pressure molding machine and subjected to pressure molding.

That is, the present inventors have conventionally used common sense in a pressure molding machine to manufacture a fuel cell separator by heating and pressure molding a mixed material of carbonaceous powder and a binder. The heating of the mixed raw material, which has been performed, is intentionally heated in a heating furnace, and introduced into a pressure molding machine to perform pressure molding. The present inventors have found that a separator can be efficiently manufactured and a method for manufacturing a fuel cell separator suitable for mass production of a fuel cell separator can be provided, and the present invention has been completed.

[0008] In the present invention, the mixed raw material is heated in a heating furnace separate from the pressure molding machine, and then the heated mixed raw material is introduced into the pressure molding machine for pressure molding. The occupation time of the molding machine can be reduced. For this reason,
The rotation efficiency of the pressure molding machine is increased, and the fuel cell separator can be efficiently mass-produced. Even if heating is performed in a heating furnace separate from the pressure molding machine and then subjected to pressure molding with the pressure molding machine, the quality and functionality of the obtained separator are not impaired. It is possible to efficiently mass-produce the separator having the expected performance.

In the present invention, the heating before the pressure molding is preferably performed at a temperature equal to or higher than the glass transition point (Tg) of the binder. In order to reduce blistering and deformation, it is preferable to perform the treatment at a temperature lower than the decomposition point of the binder. However,
When the mixed raw material is not filled in the molding die at the time of heating, it is preferable to heat at a temperature lower than the glass transition point (Tg) of the binder from the viewpoint of handling properties. This heating step is preferably carried out continuously by continuously feeding the mixed raw material to the heating furnace.

In addition, when the pressure is released after the pressure molding, and then the die is released, cooling is performed in an optional step between the time after the pressure molding and the release of the die, so that the glass transition point (Tg) of the binder is lower than the glass transition point (Tg). It is preferable to perform the die cutting at a low temperature.

In this case, it is preferable to continuously cool the binder to a temperature lower than the glass transition point (Tg) of the binder after depressurization.

Further, in the present invention, productivity is improved by continuously supplying a mixed raw material to each of the steps of heating, pressure forming, depressurizing, cooling, and die cutting to continuously produce a separator. More preferred above.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method for producing a fuel cell separator of the present invention will be described in detail.

In the method of the present invention, first, a carbonaceous powder and a binder are mixed to produce a mixed raw material.

As the carbonaceous powder, graphite powder is usually used. There is no particular limitation on the graphite powder, and flaky, granular, massive, earth-like natural graphite, petroleum coke, pitch coke, and the like are used as main raw materials, and kneading, molding, firing, and masses produced by graphitization are included. Artificial graphite or the like may be pulverized as necessary, or expanded graphite or the like.

Carbonaceous powders such as graphite powders have an ash content of 1% by weight or less, especially 0.1% by weight, from the viewpoint of conductivity, battery performance and the like.
It is preferably at most 5% by weight. The content of alkali metal, alkaline earth metal and transition metal is 500 pp.
It is preferably at most m, especially at most 100 ppm.

The volatile matter in the carbonaceous powder is 2% by weight or less from the viewpoint of the surface smoothness of the separator and the battery performance.
In particular, it is preferably at most 1% by weight. The fixed carbon is preferably 98% by weight or more, particularly preferably 99% by weight or more.

The particle size of the carbonaceous powder is preferably such that the maximum particle size is 1000 μm or less from the viewpoint of separator performance and the like.
0 μm or less is more preferable, and 300 μm or less is particularly preferable. However, from the viewpoints of moldability and performance of the separator, it is preferable not to include fine powder. Therefore, the average particle size is 1 to 100 μm, particularly 3 to 70 μm, and particularly preferably 5 to 70 μm.
It is preferably from 50 μm to 50 μm.

On the other hand, the binder is not particularly limited.
Resins such as thermoplastic resins and thermosetting resins, rubbers, thermoplastic elastomers, and mixtures thereof are used.

As the thermoplastic resin used as the binder, saturated polyester resin, styrene-acryl resin,
Styrene resin, ABS resin, polyamide resin, polycarbonate resin, polysulfone resin, polyvinyl chloride resin, polyolefin resin, polyphenylene ether resin, polyphenylene sulfide resin, polyvinyl butyral resin, acrylic resin, fluorine resin, phenoxy resin, urethane resin, and these resins Block copolymer,
And mixtures thereof.

As the thermosetting resin, a phenol resin,
Examples include epoxy resins, unsaturated polyester resins, melamine resins, urea resins, diallyl phthalate resins, and mixtures thereof. The phenol resin may be any of a novolak resin, a resol resin, and a modified resin thereof, for example, a rubber-modified phenol resin.

The above rubber-modified phenolic resin can be obtained by reacting an unvulcanized rubber with a phenolic resin. Examples of the unvulcanized rubber include fluorine rubber, silicone rubber, butyl rubber, and chloroprene rubber. , Nitrile rubber, nitrile chloroprene rubber, chlorinated butyl rubber, chlorinated polyethylene, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-acryl glycidyl ether three-dimensional copolymer, urethane rubber, acrylic rubber, ethylene-propylene rubber, styrene rubber , Butadiene rubber, natural rubber, etc., or a mixture of two or more thereof or a copolymerized reaction product.

The novolak resin is, for example, phenol,
o-cresol, m-cresol, p-cresol,
2,5-xylenol, 3,5-xylenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, tert-butylphenol, 1-naphthol, 2
-At least one phenol such as naphthol, 4,4'-biphenyldiol, bisphenol A, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, phloroglicinol, etc. under an acid catalyst, Is a resin polycondensed with at least one of aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde and furfural, or ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and a resol resin is a novolak resin. Is a resin that has been polycondensed in the same manner except that an alkali catalyst is used in place of the acid catalyst in the polycondensation.

Among the phenolic resins, when a novolak resin is used, a curing reaction occurs when a curing agent is used, and when a resol resin is used, a curing reaction occurs without using a curing agent,
It becomes a cured product. Therefore, when a novolak resin is used as the phenol resin, it is desirable to use a curing agent to cure the separator during pressure molding. As the curing agent, for example, hexamethylenetetramine, and an amino compound having at least two methylol groups, alkoxymethyl groups, acetoxymethyl groups and the like as functional groups, specifically, melamine derivatives such as methoxymethylated melamine,
Resol resins and the like. In addition, these hardening | curing agents are 5 to 1 normally with respect to the total amount with a novolak resin.
0% by weight is used.

The rubbers and thermoplastic elastomers include natural rubber (isoprene rubber), synthetic rubber, styrene-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, and polyolefin-based thermoplastic elastomer. Elastomers, and mixtures thereof, for example, butadiene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, butyl rubber, ethylene propylene rubber, ethylene butene rubber, urethane rubber, fluorine rubber, silicon rubber, styrene Isoprene block copolymer and its hydrogenated derivative, styrene butadiene block copolymer and its hydrogenated derivative, styrene butylene block copolymer, polyether ether Ether block copolymer, a polyester ester block copolymer, polyether block amide copolymers, and mixtures thereof.
The rubber may be crosslinked at the time of molding with a crosslinking agent. As the crosslinking agent, a vulcanizing agent such as sulfur or a peroxide is used, and a peroxide is preferred.

When a thermoplastic resin, a thermoplastic elastomer or a rubber to which a vulcanizing agent is added as a binder is used as a binder, a cross-linking reaction is caused by the curing agent and a cross-linking agent (vulcanizing agent), and Things.

Among the above, the binder is a phenol resin among thermosetting resins, a polyolefin resin among thermoplastic resins, an ethylene propylene rubber, an isoprene rubber, a styrene butadiene rubber, a butyl rubber among rubbers. Among the thermoplastic elastomers, a hydrogenated derivative of a styrene-butadiene block copolymer is preferable. Among them, those which do not cause defects in a molded product due to generation of a decomposition gas under heating and pressure molding conditions, for example, heating loss ( In a nitrogen gas atmosphere, the temperature is raised from room temperature to 5 ° C / min.
It is preferable to select a material having a weight loss of 50% to 150 ° C. when heated to 50 ° C.) of 2% by weight or less, for example, a thermoplastic resin, a rubber, a thermoplastic elastomer, or a mixture thereof. Is preferred.

The particle size of the binder is preferably equal to or less than the particle size of the carbonaceous powder, and is 0.5 to 1.2 times, preferably 0, times the particle size of the carbonaceous powder. .6-1.
The particle size is 1 times, more preferably 0.7 to 1.0 times.
However, if the particle size of the binder is too small, air is included between the carbonaceous powder and the binder, and the binder becomes bulky.

The mixing of the carbonaceous powder and the binder is carried out by further adding a curing agent, a cross-linking agent (vulcanizing agent) and the like as necessary.
Tumble blender, ribbon blender, V-type blender, Henschel mixer, high-speed mixer, revolving mixer (for example, planetary mixer) or the like, or uniformly mixed, or single- or twin-screw extruder, roll, Banbury mixer, This is performed by mixing and kneading with a kneading machine such as a kneader or Brabender.

During this mixing, the carbonaceous powder and the binder are mixed more uniformly by heating at about 300 ° C. or lower, or by previously wetting the carbonaceous powder with an organic solvent or an aqueous medium. This is preferable because a separator having more uniform properties can be produced. For the same reason, the binder is preferably mixed as a solution or dispersion of an organic solvent or an aqueous medium.

Examples of the organic solvent used for wetting the carbonaceous powder and liquefying the solution or dispersion of the binder include alkanes such as butane, pentane, hexane, heptane and octane, cyclopentane, cyclohexane, cycloheptane and cyclohexane. Cycloalkanes such as octane, methanol, ethanol, propanol, butanol, amyl alcohol, hexanol, heptanol, octanol, decanol, undecanol, diacetone alcohol, furfuryl alcohol, alcohols such as benzyl alcohol, methyl cellosolve, ethyl cellosolve, butyl cellosolve , Methyl cellosolve acetate, cellosolves such as ethyl cellosolve acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol and dipropylene glycol dimethyl ether, acetone, methyl amino ketone, cyclohexanone, ketones acetophenone,
Ethers such as dioxane and tetrahydrofuran, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, ethyl lactate, 3-methoxypropion Esters such as methyl acid, halogenated hydrocarbons such as chloroform, methylene chloride and tetrachloroethane, aromatic hydrocarbons such as benzene, toluene, xylene, phenol, cresol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc. And the like.

Among these, the organic solvent used for the binder is preferably one that dissolves the binder, and one that has a solubility index similar to that of the binder. For example, an alcohol is preferable for a thermosetting resin such as a phenol resin, and an aromatic hydrocarbon is preferable for a thermoplastic resin such as a polyolefin resin and a rubber and a thermoplastic elastomer.

On the other hand, the aqueous medium is not particularly limited, but water is usually used.

Also, a mixture of the above-mentioned organic solvent and an aqueous medium can be used. In this case, the mixing ratio may be arbitrary, but is usually about 1/100 to 100/1.

In particular, it is preferable that the organic solvent for wetting the carbonaceous powder and the organic solvent used for the solution or dispersion of the binder have an azeotropic property. It is particularly preferred that

The amount of the organic solvent or aqueous medium used to wet the carbonaceous powder is preferably 1 to 300 parts by weight based on 100 parts by weight of the carbonaceous powder. The concentration of the binder in the liquid is preferably 1 to 90% by weight.

When a curing agent or a cross-linking agent (vulcanizing agent) for the binder is used, the curing agent or the cross-linking agent (vulcanizing agent) is used.
Such as a method of mixing with a binder or a solution or dispersion of an organic solvent or an aqueous medium thereof, a method of mixing with a carbonaceous powder or a wet substance thereof, and a method of mixing as a solution or dispersion or a wet substance of an organic solvent. Either way is fine,
It is preferable to use it by mixing it with a wet carbonaceous powder.

The binder is preferably used in an amount of 1 to 60 parts by weight based on 100 parts by weight of the carbonaceous powder.
More preferably, it is 0 parts by weight. In particular, when a thermosetting resin is used as the binder, the amount is 5 to 30 parts by weight based on 100 parts by weight of the carbonaceous powder. When a thermoplastic resin, rubber, or a thermoplastic elastomer is used, 100 parts by weight of the carbonaceous powder is used. Is preferably 1 to 20 parts by weight with respect to If the amount of the binder used is less than the above range, the mechanical strength and the like of the obtained separator tend to be inferior, and if it exceeds the above range, the performance such as conductivity of the separator tends to be impaired.

The mixture obtained by mixing the carbonaceous powder, the binder, and, if necessary, the curing agent or the cross-linking agent (vulcanizing agent) becomes wet, paste, or lump. Prior to pressure molding under heating, this mixture is appropriately heated and dried. The heating temperature at that time may be any temperature at which the used organic solvent or aqueous medium can be evaporated and the binder is not deteriorated, but is usually set to a temperature of 200 ° C. or lower, and the organic solvent or the organic solvent in the mixture is used. Drying is preferably performed until the content of the aqueous medium becomes preferably 1% by weight or less.

The mixture after heating and drying usually becomes non-uniform granules or agglomerates.
For example, with a mixer, jaw crusher, gyratory crusher, roll mill, sample mill, jet mill, hammer mill, impeller breaker, etc.
The maximum particle size is less than 3 mm, more preferably the maximum particle size is 0.1 mm.
The coarse pulverization is performed so as to have a thickness of 1 mm to 2 mm, more preferably 0.5 mm to 1 mm.

The mixed raw material containing the carbonaceous powder and the binder thus obtained is introduced into a heating furnace and heated.

The heating furnace is not particularly limited,
In mass production, a heating furnace that can be continuously fed into a heating furnace and continuously performs a heating process, for example, a horizontal or vertical continuous furnace, for example, a tunnel furnace, a pusher furnace, and a bucket furnace (The mixed raw material is stored in the bucket,
A heating furnace that continuously moves the mixed raw material by moving the bucket, or a batch furnace (a heating furnace that accommodates a large amount of mixed raw material at once, heats it, and then moves it out of the furnace on a belt conveyor and discharges it) Is exemplified.

When the mixed raw material is introduced into the heating furnace, the mixed raw material may be introduced directly into the furnace. However, it is more preferable to introduce the mixed raw material into a container such as a tray that can be appropriately transported. This is preferable because it can prevent Alternatively, the material may be charged into a molding die made of a die processed into a desired shape and then introduced. A release agent is appropriately applied to this molding die. There is no particular limitation on the method of filling the mixed raw material into the molding die, but industrially, the mixed raw material is put into the hopper, a fixed amount is put into the forming die, and the shape of the forming die is appropriately adjusted by using an auxiliary tool. In accordance with the method, a method of spreading the mixed raw material to every corner is adopted.

When a separator having a plurality of reaction gas flow grooves having a large number of parallel portions formed on at least one plate surface is formed, a large number of reaction gas flow grooves are formed on the inner surface of the mold corresponding to such reaction gas flow grooves. A molding die in which the linear ridges are provided in parallel may be used.

This heating may be performed in air, but if necessary, an atmospheric gas such as N ₂ or Ar can be used.

The heating temperature in the heating furnace is around a desired molding temperature, for example, usually (molding temperature -30 ° C) to (molding temperature + 50 ° C), preferably (molding temperature -20 ° C) to (molding temperature + 40 ° C). , More preferably (molding temperature -10
° C) to (molding temperature + 30 ° C) and lower than the decomposition point of the binder used. As described above, this heating is preferably performed at a temperature equal to or higher than the glass transition point (Tg) of the binder. However, when the mixed raw material is not filled in a molding die before heating, there is a problem in handling properties. Therefore, it is preferable to heat at a temperature lower than the glass transition point (Tg) of the binder.

It is sufficient that the mixed raw material has reached the desired temperature in the heating furnace before the pressure molding, and the heating method in the heating furnace is as follows. Any method may be used, such as introducing the mixed raw material or gradually heating after introducing the mixed raw material into the furnace.

When the temperature of the mixed raw material is lower than a desired molding temperature when the mixed raw material is introduced into a pressure molding machine after heating, the mixed raw material is appropriately heated by a heating device provided in the pressure molding machine. (Hereinafter, the heating by the press molding machine is referred to as “additional heating”). When the temperature is higher than the desired molding temperature, the molding may be carried out by slow cooling as appropriate. When additional heating is not performed, the heating equipment of the pressure molding machine can be omitted, which is industrially advantageous. In addition, when pressure molding is performed without performing additional heating, the temperature gradually decreases during the period from pressure molding to depressurization.However, in order to shorten the time until die release and efficiently manufacture the separator, Cooling from an early stage is more advantageous. However, if the temperature is lowered to a temperature lower than the glass transition point (Tg) of the binder during the press forming, the formability is impaired. In some cases, a heat insulating material is provided in the press forming machine. Alternatively, a decrease in temperature may be suppressed.

The heating temperature of the mixed raw material is checked with a surface thermometer or a thermometer provided in a molding die, and is easily controlled by adjusting the temperature of a heating furnace or a heating device provided in a pressure molding machine. can do.

After heating in a heating furnace, the mixed raw material is taken out and introduced into a pressure molding machine to perform pressure molding. At this time, the mixed raw material taken out of the heating furnace is immediately, for example, 1
It is preferable to introduce into the pressure molding machine within 0 minutes, preferably within 5 minutes, more preferably within 2 minutes.

When the mixed raw material is not filled in the molding die when heating the mixed raw material in the heating furnace, the heated mixed raw material is filled in a molding die arranged in a pressure molding machine. May be. By doing so, it is possible to reduce the time required for loading and unloading the molding die and the energy consumption required for heating the die. However, in order to uniformly fill the mixed raw material into the mold, the heated mixed raw material is filled into the forming die in a state where it is easy to handle before being introduced into the pressure forming machine, and then the forming die is pressurized. Preferably, it is introduced into a molding machine. Before the mixed raw material is heated in the heating furnace, the mixed raw material is filled into a molding die, and the molding die taken out of the heating furnace is introduced into a pressure molding machine, so that the temperature state of the molding die and the mixed raw material becomes more uniform. It is even more preferable because it becomes easier.

The press forming machine is not particularly limited.
When multiple molding dies are introduced into a pressure molding machine, multiple sheets are taken (side-by-side and simultaneously molded with multiple molding dies),
It can be a multi-stage (a plurality of stages are placed vertically, and a molding die is placed and pressed simultaneously). Further, the pressure molding in the pressure molding machine is a method in which the molding die is stationary in the pressure molding machine and the pressure molding is performed while the molding die is moved in the pressure molding machine. It may be a method.

The molding pressure and the molding temperature in the pressure molding machine are determined according to the type and the mixing ratio of the carbonaceous powder and the binder used, and the gas is sufficiently released from the molded article to form the carbonaceous powder and the binder. Is set appropriately so that the fusion of the molded article is sufficiently performed and the resulting molded article is not deformed such as cracks or warpage.
In general, lower pressures are required if the molding temperature is higher, and higher pressures if the molding temperature is lower. Molding pressure is usually 4
The pressure is preferably 0 to 400 MPa, particularly preferably 65 to 300 MPa. If the molding pressure is less than the above range, the carbonaceous powder and the binder are not sufficiently fused to each other, and defects tend to occur. If the molding pressure exceeds the above range, burrs (protrusion of the molded object from the molding die) tend to occur easily. The molding temperature is usually set to a temperature equal to or higher than the glass transition point (Tg) of the binder used in order to form a desired shape. In order to form the separator without surface roughness, chipping, cracking, deformation (warpage, swelling),
It is preferable that the temperature be lower than the decomposition point of the binder.
Here, the temperature equal to or higher than the Tg of the binder is 2 as the binder.
When a mixture of two or more kinds of binders is used, it means that the temperature is equal to or higher than the Tg of the binder having the lower Tg.
g or more.

In order to form a thin plate-like ribbed separator with a good yield without surface roughness, chipping, cracking, deformation (warpage, swelling), the molding temperature is (Tg + 20 ° C.) or more, preferably (Tg + 30 ° C.). ) Or more, more preferably the melting point (Tm) of the binder, more preferably (Tm + 2)
0 ° C.) or more, more preferably (Tm + 30 ° C.) or more. However, if the molding temperature is excessively high, the fluidity of the molded object becomes too high, and burrs are easily generated,
The dimensional stability of the resulting molded article is also poor. Also,
In addition to increasing the heat load on the molding die, it is also disadvantageous for cooling up to die removal in the subsequent process, so the molding temperature is usually
The temperature is preferably lower than the decomposition point of the binder, particularly (Tm + 100 ° C.) or lower, particularly preferably (Tm + 50 ° C.) or lower, for example, 50 to 400 ° C., particularly preferably about 100 to 300 ° C.

The decomposition point of the binder is defined as 5 ° C. in a nitrogen gas atmosphere by DSC or TG-DTA thermal analysis.
When heated from room temperature at a heating rate of / min, it refers to the temperature at which heat absorption or heat generation starts.

As described above, after the mixed raw material is introduced from the heating furnace into the pressure molding machine, heating may be performed. However, if the heating is continued after the start of pressurization to raise the temperature of the mixed raw material, ,
Decomposition gas generated from the mixed raw material easily causes a reduction in the strength of the molded body and nonuniform physical properties. The temperature of the mixed raw material at the time of pressure molding is not substantially raised from the pressure molding start temperature, and if the pressure molding is performed, the uniformity of the separator can be improved. The performance is also improved, which is preferable. In addition, not substantially raising the temperature means that the temperature is raised to such an extent that no decomposition gas is generated by heating after the start of the press molding, and the temperature is raised by 10 ° C. or less from the press forming start temperature, preferably. Includes a temperature rise of 8 ° C. or lower, but it is more preferable to perform pressure molding at a temperature lower than the temperature immediately before pressure molding, so that a heating operation is not required, and thus heating equipment of a pressure molding machine is not required. Further, the performance of the obtained molded body is improved, which is industrially advantageous.

The uniformity of the obtained separator is expressed, for example, as follows. That is, the maximum bending stress of the separator obtained by the method of the present invention is usually 10 MPa or more, especially 10 to 150 MPa, the deflection is usually 0.1 mm or more, especially 0.2 to 3.0 mm, and the volume resistivity ( (Plane direction) is preferably lower, but is usually 0.1 mΩ · cm or more, and the upper limit is usually 200 mΩ · cm.
cm or less, preferably 100 mΩ · cm or less, more preferably 50 mΩ · cm or less, by not substantially raising the temperature of the mixed raw material at the time of pressure molding from the pressure molding start temperature, Variations in these values in the plane of the separator plate can be reduced as follows. That is, as a coefficient of variation of values at any five points (9 points for volume resistivity) cut out from the plate surface of the separator, in the case of the maximum bending stress, the lower limit is usually 0.001 or more, and the upper limit is usually 0.1. It is 15 or less, preferably 0.12 or less, and more preferably 0.10 or less. In the case of deflection, the lower limit is usually 0.001 or more, and the upper limit is 0.15 or less, preferably 0.12 or less, more preferably 0.10 or less. In the case of volume resistivity, the lower limit is usually 0.001 or more, and the upper limit is usually 0.15 or less, preferably 0.12 or less, and more preferably 0.10 or less.
The coefficient of variation is a value obtained by dividing the standard deviation by the average value.

After the pressure molding by the pressure molding machine, the pressure is reduced in the pressure molding machine. This removal may be performed while moving the molding die in the pressure molding machine, or may be performed in a stationary state. Further, this pressure reduction may be performed so as to continuously reduce the pressing force, or may be performed so as to gradually reduce the pressing force. If air is sufficiently released during pressure molding, deformation and cracks such as swelling are unlikely to occur, so pressure can be released without cooling.However, if air is difficult to release, depressurizing at high temperature, Since deformation such as swelling or cracking is likely to occur, it is desirable to reduce the pressure after cooling to some extent or while cooling.

In the case of cooling at the time of depressurization, if the temperature is cooled to an excessively low temperature, the occupation period of the press molding machine is lengthened, and the productivity tends to decrease. When cooling is stopped at an excessively high temperature, the effect of cooling is not obtained, and deformation or cracking such as swelling may occur. Therefore, the cooling temperature is usually a temperature lower by several to 150 ° C., preferably lower by about 5 to 100 ° C. than the temperature at the end of the pressure molding, and the melting point (Tm) of the binder used. Below, preferably,
(Tm−50 ° C.) or lower and preferably Tg or higher of the binder. By starting the cooling from the time when the pressure molding is started, the temperature can be reduced to a temperature equal to or lower than the melting point (Tm) of the binder, and the pressure is released at an earlier stage, for example, at the end of the pressure molding. Therefore, it is preferable in shortening the occupation period of the press molding machine.

It is preferable to perform deaeration treatment with a vacuum pump or the like before the completion of the pressure molding step, since a dense molded body can be obtained and deformation such as swelling or warpage can be suppressed. . This deaeration treatment is performed, for example, at 40,000.
Pa (300 Torr) or less, especially 27000 Pa
(200 Torr) or less, especially 5000 Pa (37 T)
orr) or less, especially 1300 Pa (10 Torr)
It is preferable to perform the following.

In this deaeration treatment, the mixed raw material obtained by mixing the carbonaceous powder and the binder is heated, heated in a heating furnace, heated in a heating furnace, and then introduced into a pressure molding machine. Before and after the introduction into the pressure molding machine and before the start of the pressure molding, and after the start of the pressure molding and until the end of the pressure molding, it can be carried out. This deaeration treatment can be performed in one or more of these steps, or can be performed continuously in a plurality of steps. Among these, the degassing treatment before heating removes the gas contained in the mixed raw material and can reduce the distance between the particles, so that the bulk density increases and a dense molded body can be obtained. This has the effect of improving physical properties such as strength and volume resistivity of the molded body. The degassing process from the time of heating to the end of pressure molding not only removes gas contained in the mixed raw material and reduces the distance between particles, but also removes gas substances generated by heating. Therefore, the physical properties of the molded body can be further improved. Above all, the degassing treatment is the most effective in removing the gas contained in the mixed raw material and the gaseous substances generated by heating, and is therefore preferable in improving the physical properties of the molded body. In terms of shortening the time, the degassing treatment is preferably performed at the same time as the pressure molding, so that it is preferable. Further, in the case of performing the deaeration treatment continuously in a plurality of steps, it is preferable to perform the deaeration treatment from an earlier stage because more effects can be obtained. It is preferable to perform a deaeration treatment, and it is more preferable to perform a deaeration treatment over the following steps.

The deaeration release after performing such a deaeration process may be performed all at once, or may be performed gradually. Also,
The degassing release in the case of degassing during the pressure molding may be performed as long as the air is released and the carbonaceous powder and the binder are sufficiently fused together. It may be later.

Further, in the deaeration process before the introduction into the pressure molding machine, the shape is held together with the deaeration process in the same mold as that at the time of the pressure molding or a mold close to the final shape excluding the fine shape. As a result, the bulk density can be increased and the shape can be adjusted, so that there is also an effect that the handling property when taking out from the mold and transporting to the next step is improved.

In order to improve the handleability, the shape can be adjusted by carrying out the shape preservation by preforming with the same mold as that at the time of pressure molding or with a mold close to the final shape excluding the fine shape. . This preforming is usually carried out at 20-30.
The molding is performed at a molding pressure of 0 MPa, preferably 20 to 200 MPa. The molding temperature is not particularly limited as long as it is a temperature lower than the decomposition point of the binder, but when it is performed at room temperature, a heating operation is not required, which is industrially advantageous. In addition, the bulk density of the mixed raw material obtained by preforming is 1.2 to 1.8 g / cm.
³ , preferably 1.3 to 1.8 g / cm ³ , more preferably 1.4 to 1.8 g / cm ³ ,
It may be before heating the mixed raw material or after heating and before introducing it into the pressure molding machine.

After performing pressure molding and depressurization, the molding die is taken out of the pressure molding machine, and the obtained molded body is taken out of the molding die, and the mold is released. This die-cutting is preferably performed after the temperature is lowered to a temperature lower than the glass transition point (Tg) of the binder.

That is, at a temperature equal to or higher than the glass transition point (Tg) of the binder, the molded body is likely to be deformed at the time of die-cutting.
This causes defects such as cracking, swelling and warpage, and makes it difficult to obtain the original function of the separator. Die cutting can be performed by cooling to room temperature, but the glass transition point (T
g) at a temperature of 5 ° C. or more, especially 10 ° C. or more lower than Tg, since cracking and deformation due to die cutting can be suppressed, and in order to shorten the occupation time of the molding die,
It is preferable to perform die cutting at (Tg-5 ° C) or less, particularly (Tg-10 ° C) or less, for example, at (Tg-20 ° C) to (Tg-80 ° C). Therefore, when the molding die is not taken out from the pressure molding machine, the molded body is taken out from the pressure molding machine when the above temperature is reached.

In this case, the molding die can be naturally cooled by cooling, but forced cooling is performed by using an appropriate cooling means such as a low-temperature gas or a refrigerant spray. From the viewpoint of increasing the productivity and improving the productivity.

Cooling when removing the molding die from the pressure molding machine may be performed in any step before, during, or after pressure reduction after pressure molding. The molding dies are passed through the cooling zone while being continuously moved on the belt conveyor; or, one or more molding dies are moved into the cooling chamber batchwise and cooled, and then cooled by the belt conveyor or the like. It is possible to sequentially remove the mold by performing a continuous operation such as moving and discharging;
This is preferable because the occupation period of the molding die can be shortened, and the productivity can be further improved.

Regardless of whether cooling is performed before, during, or after depressurization, the cooling rate depends on the type of carbonaceous powder and binder used, the mixing ratio, the heating temperature, the heating temperature, and the like. It is set as appropriate depending on the pressing conditions, etc., but if the cooling rate can be increased by using a binder that does not generate decomposition gas or generate foam under heating and pressurizing conditions, if the cooling speed can be increased, the die removal can be started earlier. This is preferable because the occupation period of the molding die can be shortened.

As the cooling rate, for example, after pressure molding,
0.03 ° C / sec (= 1.8 ° C / m) until the temperature suitable for die removal in any of the steps before, during and after depressurization.
in) or more, preferably at 0.04 ° C./sec or more, but in order to shorten the time until die release, 0.05 ° C./sec.
sec or more, preferably 0.1 ° C./sec or more. The upper limit is usually 100 ° C / mi
n or less.

The method of the present invention is carried out, for example, in the following steps.

(1) The mixed raw material is filled in a molding die and heated in a heating furnace, and then the molding die is introduced into a pressure molding machine and pressurized. After the pressure molding, the pressure is released and the mold is released. Cooling is performed from the press molding to before the mold is released. Preferably, cooling is started together with the start of pressure molding. If necessary, deaeration treatment is performed from heating to before the end of pressure molding.

(2) After heating the mixed raw material in a heating furnace, the mixture is filled in a molding die, and the molding die is introduced into a pressure molding machine and pressurized. After the pressure molding, the pressure is released and the mold is released. Cooling is performed from the press molding to before the mold is released. Preferably, cooling is started together with the start of pressure molding. If necessary, deaeration treatment is performed from heating to before the end of pressure molding. In addition, the shape may be preserved before or after heating in a heating furnace as necessary.

(3) After heating the mixed raw material in a heating furnace, the mixed raw material is filled in a molding die arranged in a pressure molding machine and pressure molded.
After the pressure molding, the pressure is released and the mold is released. Cooling is performed from the press molding to before the mold is released. Preferably, cooling is started together with the start of pressure molding. If necessary, deaeration treatment is performed from heating to before the end of pressure molding. In addition, the shape may be preserved before or after heating in a heating furnace as necessary.

In the method for producing a fuel cell separator according to the present invention, the mixed raw material or a molding die filled with the mixed raw material is continuously used in each of the steps of heating, press forming, depressurizing, cooling and die cutting. By supplying and producing separators continuously,
This is preferable because a remarkable improvement in productivity can be obtained by shortening the occupation time of the pressure molding machine and the molding die.

The size and shape of the separator produced by the method of the present invention are not particularly limited, but usually a plate-like separator having a length and width of 50 to 1000 mm, especially 80 to 500 mm, is exemplified. The thickness of such a plate-like separator is preferably thinner, usually 20 mm or less, preferably 10 mm or less, more preferably 5 mm or less, and the lower limit is 0.1 mm in terms of performance such as strength and gas barrier properties.
Or more, preferably 0.3 mm or more. Further, the bulk density is usually 1.8 g / cm ³ or more, especially 1.9 to 2.2.
g / cm ³ . The present invention is particularly suitable for manufacturing a plate-like fuel cell separator in which one or both plate surfaces of such a plate-like separator is provided with a reaction gas flow channel groove having a large number of parallel portions.

[0077]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 After 500 g of natural graphite powder (average particle size: 24 μm) was added to 100 g of toluene and mixed to wet the graphite powder, commercially available polystyrene (average molecular weight: 200,000, glass transition point (Tg) = 75 g of a 33% by weight toluene solution (100 g, decomposition point = 395 ° C. (literature value)) (25 g of polystyrene + 50 g of toluene) were added, and the mixture was kneaded at 40 ° C. for 1 hour at a rotation speed of about 30 rpm using a double-arm kneader. And dried at 100 ° C. for 3 hours. 100 g of the powder under the sieve obtained by sieving the obtained mixture so as to have a maximum particle size of 1 mm or less was weighed and filled into a molding die. After heating the mold containing the powder to a temperature of 180 ° C. in 35 minutes using a dryer, the heated mold is placed on a hydraulic press plate, and a hydraulic pump is operated under a pressure of 98 MPa. Press molding was performed for 5 minutes. The temperature of the mold at the start of press molding is 1
The temperature was 79 ° C., and cooling started with a water-cooled jacket simultaneously with the start of molding. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to atmospheric pressure while cooling to 50 ° C. over 30 minutes with a water-cooled jacket. Thereafter, the mold is taken out from the hydraulic press, and the temperature of the mold is reduced to 44 ° C. for 10 minutes in the handling process.
A plate having a height of 5 mm and a plate-like fuel cell separator having a length of 100 mm and a width of 100 mm was manufactured by die-cutting the sample whose temperature had dropped to below.

During this time, the occupation time (operating time) of the hydraulic press was 35 minutes (press forming 5 minutes + depressurizing 30 minutes). In addition, the time from removal of the mold from the hydraulic press to removal of the mold was 10 minutes, and the time required from heating to removal of the mold was 80 minutes in total.

The obtained separator had a smooth surface without any noticeable unevenness, and had a bulk density of 2.1 g.
/ Cm ³ , and the volume resistivity measured by a four-probe resistance meter (“Loresta MP” manufactured by Mitsubishi Chemical Corporation) was 2.5 mΩ · cm. The volume resistivity was measured at nine points, and the average value was taken as the volume resistivity of the separator. The same applies to the following examples and comparative examples.

Example 2 The cooling by the water cooling jacket after stopping the hydraulic pump was
Pressure molding was performed in the same manner as in Example 1 except that the pressure was reduced to the atmospheric pressure while the temperature was raised to 15 ° C. over 15 minutes.
The mold is taken out of the hydraulic press and cooled with a water-cooled jacket, so that the temperature is reduced to 50 ° C. at a rate of 0.07 ° C./sec.
After cooling to 10
A plate-shaped fuel cell separator was manufactured by die-cutting the material whose temperature was lowered to 44 ° C. in a minute.

During this time, the occupation time (operating time) of the hydraulic press was 20 minutes (pressure molding 5 minutes + pressure reduction 15 minutes). The time from die removal from the hydraulic press to die release was 22 minutes, and the total time required from heating to die release was 77 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface condition was visually smooth without any noticeable unevenness, the bulk density was 2.1 g / cm ³ , and the volume resistivity was It was 2.6 mΩ · cm.

Example 3 The cooling by the water cooling jacket after the hydraulic pump was stopped was
The molding was performed in the same manner as in Example 1 except that the pressure was reduced to the atmospheric pressure while the temperature was reduced to 5 ° C. over 5 minutes, and then the mold was taken out of the hydraulic press and cooled with a water-cooled jacket to reduce the cooling rate. After cooling to 50 ° C. at 0.07 ° C./sec, the temperature was lowered to 44 ° C. in 10 minutes in the handling process of the die-cutting operation, and the plate was die-cut to produce a plate-shaped fuel cell separator.

During this time, the occupation time (operating time) of the hydraulic press was 10 minutes (pressure molding 5 minutes + pressure reduction 5 minutes).
The time required to remove the mold after removing the mold from the hydraulic press was 34 minutes, and the total time required from heating to removing the mold was 79 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface state was visually smooth without any noticeable unevenness, the bulk density was 2.1 g / cm ³ , and the volume resistivity was It was 2.7 mΩ · cm.

Example 4 As a mixed raw material, natural graphite powder (average particle size: 13 μm) 5
After wetting the graphite powder by adding and mixing 100 g of toluene with 00 g, a commercially available styrene / butadiene copolymer (average molecular weight 220,000, glass transition point (Tg))
= 100 ° C., decomposition point = 395 ° C. (literature value), 75 g of a 33% by weight toluene solution (25 g of a styrene / butadiene copolymer + 50 g of toluene) were added, and the number of revolutions was about 30 rpm and 40 ° C. using a double-arm kneader. And then heated and dried at 100 ° C. for 3 hours, and dried in the same manner as in Example 1 except that a powder under a sieve sieved to have a maximum particle size of 1 mm or less was used. Heating and pressing were performed, and then the pressure was reduced to atmospheric pressure while cooling to 50 ° C. over 30 minutes. The mold was taken out from the hydraulic press, and the mold whose temperature was reduced to 44 ° C. in 10 minutes in the handling process of the mold cutting operation was die-cut to produce a plate-shaped fuel cell separator.

During this time, the occupation time (operating time) of the hydraulic press was 35 minutes (press forming 5 minutes + depressurizing 30 minutes).
In addition, the time from removal of the mold from the hydraulic press to removal of the mold was 10 minutes, and the time required from heating to removal of the mold was 80 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface state was visually smooth without any noticeable unevenness, and the bulk density was 2.0 g / cm ^3.
And the volume resistivity was 9.6 mΩ · cm.

Example 5 As a raw material powder, 500 g of the natural graphite powder (average particle size: 13 μm) used in Example 4 was mixed with 100 g of toluene to wet the graphite powder, and then polystyrene (average molecular weight: 340,000; Glass transition point (Tg) = 101 ° C., decomposition point 395 ° C. (literature value) 75 g of 33% by weight toluene solution
(25 g of polystyrene + 50 g of toluene), and using a double-arm kneader, the number of revolutions was about 30 rpm,
After kneading for a period of time, the mixture was heated and dried at 100 ° C. for 3 hours, and pressed under the same conditions as in Example 1 except that powder under a sieve sieved to have a maximum particle size of 1 mm or less was used. Molding was performed, and then the pressure was reduced to atmospheric pressure while cooling to 50 ° C. over 30 minutes. The die was taken out of the hydraulic press, and the temperature was lowered to 44 ° C. in 10 minutes in the handling process of the die cutting operation, and the plate was die-cut to produce a plate-shaped fuel cell separator.

During this time, the occupation time (operating time) of the hydraulic press was 35 minutes (press forming 5 minutes + depressurizing 30 minutes). In addition, the time from removal of the mold from the hydraulic press to removal of the mold was 10 minutes, and the time required from heating to removal of the mold was 80 minutes in total.

The obtained separator was manufactured in the same manner as in Example 1.
When the evaluation was performed in the same manner, the surface condition visually
Is smooth and has no noticeable unevenness, and its bulk density is 2.1 g.
/ Cm ³And the volume resistivity is 8.6 mΩ · cm.
Met.

Comparative Example 1 100 g of a mixed raw material of natural graphite powder and polystyrene prepared in the same manner as in Example 1 was weighed and filled in a mold.
The mold containing the powder was heated to a temperature of 180 ° C. using a heater of a hydraulic press. When the temperature reached 180 ° C. 45 minutes later, the hydraulic press was operated to perform press molding under a pressure of 98 MPa for 5 minutes. The temperature of the mold at the start of press molding was 179 ° C., and cooling was started with a water-cooled jacket simultaneously with the start of molding. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to atmospheric pressure while cooling to 50 ° C. for 30 minutes with a water-cooled jacket. Thereafter, the mold is taken out from the hydraulic press, and the temperature of the mold is reduced to 44 ° C. for 10 minutes in the handling process.
After being cooled down, the mold was punched out, and the length and length were each 100 mm and the thickness was 5 mm.
mm plate-like fuel cell separator was produced.

During this time, the occupation time (operating time) of the hydraulic press is 80 minutes (heating time 45 minutes + press forming 5 minutes + depressurization 30 minutes), which is at least twice as large as that of the first embodiment and 4 times of the second embodiment.
The hydraulic press was occupied twice as long, eight times as long as in Example 3. The time from removal of the mold from the hydraulic press to removal of the mold was 10 minutes, and the time required from heating to removal of the mold was 90 minutes in total.

The obtained separator was manufactured in the same manner as in Example 1.
When the evaluation was performed in the same manner, the surface condition visually
Is smooth and has no noticeable unevenness, and its bulk density is 2.1 g.
/ Cm ³And the volume resistivity is 2.5 mΩcm.
Was.

The results of Examples 1 to 3 and Comparative Example 1 are summarized in Table 1.

[0097]

[Table 1]

Example 6 1 kg of toluene was added to 5 kg of natural powder graphite (average particle size: 13 μm) and mixed to wet the graphite powder, and then a commercially available styrene-butadiene block copolymer (styrene content: about 30% by weight) ) Is a hydrogenated derivative of styrene-based thermoplastic elastomer (hereinafter referred to as SEBC elastomer: glass transition point (Tg) = 100 ° C, decomposition point = 370 ° C (literature value)) 1.25 kg of a 20 wt% toluene solution (SE)
0.25 kg of BC elastomer + 1 kg of toluene) were added, and the spindle speed was set to 230 rpm and the chopper speed was set to 300 using a 20-liter horizontal mixer equipped with a chopper.
After kneading at 0 rpm and 40 ° C. for 10 minutes,
Heated and dried for hours. The obtained mixture is treated with a maximum particle size of 1
The powder under the sieve sieved to be less than 10 mm
0 g was weighed and filled. The mold containing this powder is
After heating to a temperature of 160 ° C. in minutes, the heated mold is placed on a hydraulic press plate, and a hydraulic pump is operated to operate at 98MP.
Press molding was performed for 5 minutes under the pressure of a. The temperature of the mold at the start of press molding was 159 ° C., and cooling was started with a water-cooled jacket simultaneously with the start of molding. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to the atmospheric pressure in one minute. Next, the mold was taken out from the hydraulic press and cooled with a water-cooled jacket to 50 ° C. at a temperature lowering rate of 0.07 ° C./sec.
A plate-shaped fuel cell separator was manufactured by die-cutting the sample whose temperature had dropped to below.

During this time, the occupation time (operating time) of the hydraulic press was 6 minutes (pressure molding 5 minutes + depressurization 1 minute). Further, the time from removal of the mold from the hydraulic press to removal of the mold was 25 minutes, and the time required from heating to removal of the mold was 61 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface state was visually smooth without any noticeable irregularities, the bulk density was 2.0 g / cm ³ , and the volume resistivity was It was 11.1 mΩ · cm.

Next, according to JIS K7171, a test piece having a length of 100 mm, a width of 10 mm, and a thickness of 5 mm was prepared by cutting a separator as a heat-pressed body, and the test piece was prepared. , The distance between fulcrums is 80m
m, the test speed is 5 mm / min, the maximum bending stress and the deflection at that time are measured by applying a load by applying an indenter to the plate surface of the separator, and the measured value and the coefficient of variation and the coefficient of variation of the volume resistivity are measured. Are shown in Table 2. The measured value is shown as an average value of five test pieces, and the coefficient of variation is a value obtained by dividing the standard deviation by the average value. The maximum bending stress and deflection are 5 points, and the volume resistivity is 9 points. It is a value obtained by dividing the standard deviation of points by the average value of nine points. The same applies to the following embodiments.

Example 7 In the same manner as in Example 6, the mold filled with the mixed raw material was heated to a temperature of 160 ° C. for 30 minutes, and then the heated mold was placed on a hydraulic press plate. 98MP by operating the hydraulic pump
Press molding was performed for 3 minutes under the pressure of a. The temperature of the mold at the start of press molding was 159 ° C., and simultaneously with the start of molding, degassing and depressurization inside the mold and cooling with a water-cooled jacket were started. The deaeration and decompression in the mold were performed by deaeration and decompression of the entire hydraulic press. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to the atmospheric pressure in one minute, and deaeration and release in the hydraulic press were performed. Immediately before degassing release, the pressure was reduced to 3000 Pa. Next, the mold is taken out from the hydraulic press and cooled with a water-cooled jacket to 50 ° C. at a temperature decreasing rate of 0.07 ° C./sec. A plate-shaped separator for a fuel cell was manufactured by die-cutting the lowered one.

During this time, the occupation time (operating time) of the hydraulic press was 4 minutes (press molding 3 minutes + depressurization 1 minute). In addition, the time from removal of the mold from the hydraulic press to removal of the mold was 33 minutes, and the time required from heating to removal of the mold was 67 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface condition was visually smooth without any noticeable unevenness, the bulk density was 2.0 g / cm ³ , and the volume resistivity was It was 6.4 mΩ · cm.

Next, the maximum bending stress and the deflection were measured in the same manner as in Example 6, and the results are shown in Table 2. In this example, a dense molded body could be obtained by degassing, and a separator having excellent volume resistivity and flexural strength could be obtained.

Example 8 A mixed raw material prepared in the same manner as in Example 6 was placed in a mold.
00g was weighed and filled. A mold containing this powder
After heating to a temperature of 170 ° C. in 3 minutes, the heated mold was placed on a hydraulic press plate. Activate hydraulic pump 9
Press molding was performed under a pressure of 8 MPa for 5 minutes. The temperature of the mold at the start of press molding was 169 ° C., and cooling was started with a water-cooled jacket simultaneously with the start of molding. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to the atmospheric pressure in one minute. Next, the mold is taken out from the hydraulic press and cooled with a water-cooled jacket to 50 ° C. at a temperature decreasing rate of 0.07 ° C./sec. A plate-shaped separator for a fuel cell was manufactured by die-cutting the lowered one.

During this time, the occupation time (operating time) of the hydraulic press was 6 minutes (pressure molding 5 minutes + pressure reduction 1 minute). In addition, the time from removal of the mold from the hydraulic press to removal of the mold was 27 minutes, and the time required from heating to removal of the mold was 66 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface condition was visually smooth without any noticeable unevenness, the bulk density was 2.0 g / cm ³ , and the volume resistivity was 2.0 g / cm ^3. It was 11.5 mΩ · cm. Next, the maximum bending stress and the deflection were measured in the same manner as in Example 6,
The results are shown in Table 2.

Example 9 In the same manner as in Example 8, the mold filled with the mixed raw materials was heated to a temperature of 170 ° C. for 33 minutes, and then the heated mold was placed on a hydraulic press plate. 98MP by operating the hydraulic pump
Press molding was performed for 5 minutes under the pressure of a. The temperature of the mold at the start of press molding was 169 ° C., and the temperature started to rise simultaneously with the start of molding. Thereafter, the hydraulic pump was stopped, and the pressure was reduced to the atmospheric pressure in one minute. The temperature of the mold at the time of depressurization was 195 ° C. Next, the mold was taken out of the hydraulic press, and cooled by a water-cooled jacket, thereby reducing the temperature at a rate of 0.07 ° C./sec.
After cooling to 50 ° C. in step c, the temperature was lowered to 44 ° C. in 10 minutes in the handling process of the die-cutting operation, and the plate was die-cut to produce a plate-shaped fuel cell separator.

During this time, the occupation time (operating time) of the hydraulic press was 6 minutes (pressure molding 5 minutes + depressurization 1 minute). In addition, the time from die removal from the hydraulic press to die release was 45 minutes, and the time required from heating to die release was 84 minutes in total.

When the obtained separator was evaluated in the same manner as in Example 1, the surface condition was visually smooth without any noticeable irregularities, the bulk density was 1.9 g / cm ³ , and the volume resistivity was It was 12.4 mΩ · cm. Next, the maximum bending stress and the deflection were measured in the same manner as in Example 6,
The results are shown in Table 2. In this example, the heating was continued after the start of pressurization to increase the temperature of the mixed raw material, so that the measured values of the volume resistivity and the maximum bending stress varied, and the deflection was reduced.

Table 2 summarizes the results of Examples 6 to 9.

[0113]

[Table 2]

From the above results, according to the present invention, the mixed raw material is heated in a heating furnace different from the pressure molding machine, and then the heated mixed raw material is introduced into the pressure molding machine to perform pressure molding. Therefore, it can be understood that the occupation time of the pressure molding machine can be reduced by the time required for heating, and the productivity can be increased.

Further, even if heating is performed in a heating furnace separate from the pressure molding machine and then pressure molding is performed in the pressure molding machine, the quality and functionality of the obtained separator are not impaired. Furthermore, it can be seen that the quality and functionality of the obtained separator can be improved by degassing treatment or an operation of substantially not raising the temperature during pressure molding.

[0116]

As described in detail above, according to the method for producing a fuel cell separator of the present invention, the occupation of a pressure molding machine used for pressure molding can be achieved without impairing the quality and functionality of the obtained separator. The time can be greatly reduced, productivity can be remarkably improved, and high-performance fuel cell separators can be efficiently mass-produced.

In particular, by performing cooling and performing die-cutting early after press-molding, not only the time required for producing the separator can be shortened, but also the rotation rate of the molding die can be increased. Efficient manufacturing can be performed. Furthermore, the quality and functionality of the obtained separator can be further improved by degassing treatment or an operation of substantially not raising the temperature during pressure molding.

Claims (24)

[Claims] 1. A method for producing a separator for a fuel cell by heating and press-forming a mixed raw material of a carbonaceous powder and a binder. A method for producing a separator for a fuel cell, comprising: 2. The method for manufacturing a fuel cell separator according to claim 1, wherein the mixed raw material is heated in a heating furnace, and then filled in a molding die and pressure molded. 3. The fuel cell separator according to claim 2, wherein the mixed material heated in the heating furnace is filled into a molding die arranged in the pressure molding machine and pressure molded. Manufacturing method. 4. The method according to claim 2, wherein after the mixed raw material heated in the heating furnace is filled in a molding die, the molding die is introduced into the pressure molding machine to perform pressure molding. For producing a fuel cell separator. 5. The method according to claim 1, wherein the mixed raw material is kept (i) before heating and / or (ii) after heating and before press molding. Of producing a fuel cell separator. 6. The fuel cell according to claim 1, wherein a heating temperature in the heating furnace is lower than a glass transition point (Tg) of the binder. Manufacturing method of separators for automobiles. 7. The method for manufacturing a fuel cell separator according to claim 1, wherein the mixed raw material is continuously fed into a heating furnace, and the heating step is continuously performed. 8. The method according to claim 1, wherein after the mixed raw material is filled in a molding die and heated in a heating furnace, the molding die is introduced into a pressure molding machine for pressure molding. For producing a fuel cell separator. 9. The method according to claim 8, wherein a heating temperature in the heating furnace is equal to or higher than a glass transition point (Tg) of the binder and lower than a decomposition point of the binder. A method for producing a fuel cell separator. 10. The method for manufacturing a fuel cell separator according to claim 8, wherein the molding die is continuously fed into the heating furnace, and the heating step is continuously performed. 11. The fuel cell separator according to claim 1, wherein a temperature at the time of the pressure molding is equal to or higher than a glass transition point (Tg) of the binder. Method. 12. The method according to claim 1, wherein additional heating is performed after introduction into the pressure molding machine, and a maximum temperature reached by the additional heating is a glass transition point of the binder. (Tg) A method for producing a fuel cell separator, wherein the temperature is lower than the decomposition point of the binder. 13. The pressure molding according to any one of claims 1 to 12, wherein the temperature of the mixed raw material at the time of the pressure molding is not substantially raised from the pressure molding start temperature. Of producing a fuel cell separator. 14. The degassing process according to claim 1, wherein after the carbonaceous powder and the binder are mixed, the mixed raw material is subjected to deaeration before the completion of pressure molding. Of producing a fuel cell separator. 15. The method according to claim 1, wherein the pressure is removed, the pressure is released, and then the die is removed. And the glass transition point (Tg) of the binder
A method for producing a separator for a fuel cell, comprising: performing die cutting at a lower temperature. 16. The method for manufacturing a fuel cell separator according to claim 15, wherein a pressure-reducing temperature at the time of pressure-reduction after the pressure molding is equal to or lower than a melting point (Tm) of the binder. 17. The fuel cell separator according to claim 15, wherein cooling to a temperature lower than a glass transition point (Tg) of the binder after depressurization is performed continuously. Production method. 18. The separator according to claim 15, wherein the mixed raw material is continuously supplied to each of the heating, pressure forming, depressurizing, cooling, and die-cutting steps. And a method for producing a fuel cell separator. 19. The method according to claim 8, wherein after the pressure molding, the pressure is released, the die is released, and cooling is performed in an arbitrary step from after the pressure molding to the die release. A separator for a fuel cell, wherein the separator is continuously manufactured by continuously supplying the molding die to each of the heating, pressure molding, depressurization, cooling, and die-cutting steps. Manufacturing method. 20. The method for manufacturing a fuel cell separator according to claim 1, wherein the carbonaceous powder is graphite powder. 21. The carbonaceous powder according to claim 1, wherein the amount of the binder used is
A method for producing a fuel cell separator, wherein the amount is 1 to 60 parts by weight with respect to parts by weight. 22. The method according to claim 1, wherein the mixed raw material of the carbonaceous powder and the binder is a mixture of the carbonaceous raw material and the binder in the presence of an organic solvent and / or an aqueous medium. It is characterized by being prepared by mixing to form a wet, pasty, or bulk form and then drying the mixture so that the content of the organic solvent and / or aqueous medium in the mixture is 1% by weight or less. A method for producing a fuel cell separator. 23. The fuel cell separator according to claim 1, wherein the fuel cell separator is a plate-like body, and a reaction gas flow channel groove having a large number of parallel portions is formed on at least one plate surface. A method for producing a fuel cell separator. 24. The fuel cell separator according to claim 1, wherein each of the fuel cell separators has a length of 50 mm.
A method for producing a fuel cell separator, which is a plate having a thickness of 0.1 to 20 mm and a thickness of 0.1 to 20 mm.