JP2003297381A - Separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance separator for a fuel cell suppressing deformation such as warpage, bulging, or cracking by forming the separator by using carbonaceous powder and a binder as components. <P>SOLUTION: In the separator for the fuel cell comprising a formed body using the carbonaceous powder and binder as components, a coefficient of variation of bulk density is ≤0.01, a coefficient of a variation in fracture energy is ≤0.12, a coefficient of variation of volume specific resistance is ≤0.10, a coefficient of variation in maximum bending stress is ≤0.10, and a coefficient of a variation in maximum bending stress strain is ≤0.10 to suppress dispersion of a whole of the formed body. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell separator, and more particularly to a fuel cell separator obtained by molding carbonaceous powder and a binder as components.

[0002]

2. Description of the Related Art In recent years, a fuel cell, which is an energy supply source having high power generation efficiency and excellent environmental friendliness, has been attracting attention as a power generation system that answers resource problems and environmental problems. Among these fuel cells, polymer electrolyte fuel cells (PEFC) that use solid polymer as electrolyte
Is getting the most attention. This polymer electrolyte fuel cell
A film-like ion-exchange membrane serving as an electrolyte has catalyst layers on both sides, and collectors are provided on both sides thereof to form a membrane-electrode assembly (MEA). And on the outside,
A grooved separator that serves as a fuel passage is provided,
Hydrogen or oxygen passes between the MEA and the separator,
A cell is configured with all of these as one. The fuel cell has a structure in which several tens to several hundreds of cells are stacked.
For example, when a potential difference of about 0.7 V is obtained with one cell, for example, 300 cells are stacked and connected in series,
For example, a stack can be obtained that obtains a voltage of 210V.

The separator used in this fuel cell is
A thin groove (flow path) is formed on the plate-like surface, and this groove is formed in parallel with the main region of the separator, for example, in parallel or in a meandering manner in order to increase the contact area between the gas diffusion electrode and the gas. It is formed with various pitches. Typically, a ribbed electrode system in which a groove as a reaction gas flow path for hydrogen, air, etc. is engraved on the separator side surface of each positive and negative electrode plate, and a ribbed electrode method in which this groove is engraved on the surface of each separator There is a separator method, etc. As for its performance, not only it has an excellent gas barrier property that does not allow the supplied hydrogen and oxygen gases to pass therethrough and has high strength, but it also requires conductivity because it is an electrode of a fuel cell. Further, it is required to secure surface accuracy in order to prevent deterioration of conductivity between the separator and the MEA.

As a method of producing such a fuel cell separator, there is a method of mixing and molding a carbonaceous powder and a binder. The molding method mainly includes injection molding and compression molding. Specifically, in this compression molding,
After a raw material mixture of a carbonaceous powder and a binder is filled in a molding die, it is heated and pressurized by a pressure molding machine, cooled, and then demolded. Further, in injection molding, a mixed raw material of carbonaceous powder and a binder is pelletized, heated and melted by an injection molding machine, injected into a molding die, and then die-cut after cooling. As described above, in order to stack for hundreds by the method of mixing the carbonaceous powder and the binder, heating and molding, and to withstand long-term use as a fuel cell separator, warpage and swelling are required. It is necessary to suppress deformation such as cracking and deterioration of separator function at an extremely high level.

[0005]

However, since the carbonaceous powder and the binder have different powder characteristics, it is not easy to mix them uniformly at a high level. In compression molding, the behavior of the mixed powder in the mold depends on the supply state of the mixed powder of the carbonaceous powder and the binder to the molding die, as well as the heating condition and the pressurizing condition. Unevenness is liable to occur, and the molded body is liable to have burrs, warpage, swelling, and cracking. In injection molding, the behavior during heating and melting of pellets, how to provide a gate, melting temperature, injection pressure, injection speed, mold temperature, curing time, etc. can be selected in the mold. The behavior and properties of the melt were uneven, the molded body was uneven, and deformation such as warpage, swelling, and cracking and deterioration of separator performance were likely to occur. As described above, as a technique for industrially mass-producing a thin plate-shaped fuel cell separator having a shape with thin ribs by molding,
The current situation is that it has not been established yet.

The present invention has been made in order to solve the above technical problems, and an object of the present invention is to mold a carbonaceous powder and a binder as components, It is intended to obtain a high-performance fuel cell separator in which deformation such as swelling and cracking is suppressed.

[0007]

Based on the above object, as a result of intensive studies by the present inventors, a fuel cell which is a molded product formed of a carbonaceous powder and a binder as components and formed of a thin plate shape. Suppresses variations in physical properties of separators for
It has become possible to obtain a uniform fuel cell separator as a whole. That is, the fuel cell separator to which the present invention is applied is made of a molded product containing carbonaceous powder and a binder, and has a bulk density variation coefficient of 0.01 or less and a fracture energy variation coefficient of 0. It is characterized by being less than .12.

Here, the coefficient of variation of the volume resistivity is 0.1
0 or less and / or coefficient of variation of maximum bending stress is 0.1
It is preferable that the coefficient of variation of 0 or less and / or the maximum bending stress strain is 0.10 or less. By suppressing these variations in mechanical properties, it becomes possible to obtain a separator in which deformation such as warpage, swelling, and cracking is suppressed.

The carbonaceous powder may be graphite powder. Furthermore, it is preferable that the average particle diameter of the carbonaceous powder is 1 μm or more and 100 μm or less, because the molded body can be made uniform.

Furthermore, the binder is selected from the group consisting of thermosetting resins, thermoplastic resins, rubbers, and thermoplastic elastomers, and the particle size of the binder is
It is preferably 0.5 to 1.2 times the particle size of the carbonaceous powder.

Further, the present invention is characterized in that a mixed raw material of carbonaceous powder and a binder is heated and pressure-molded, and after the carbonaceous powder and the binder are mixed, the mixture is heated. It can be characterized in that it is obtained by pressure molding.

Further, a molded body is formed in a plate shape, and a reaction gas flow channel groove is formed on the plate surface of the plate shape. Further, this molded body has a length and width of 50 to 10 each.
It is a plate-shaped body having a thickness of 00 mm and a thickness of 0.5 to several tens of mm.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. 1 (a), (b)
FIG. 3 is a diagram showing an example of a separator (fuel cell separator) molded according to the present embodiment. Figure 1 (a)
Is a plan view, and FIG. 1B shows a cross section taken along the line AA of FIG. The separator 10 used in the fuel cell is
It has a thin plate-like shape as shown in Fig. 1 and a thickness of 5 mm.
It is a degree. The vertical and horizontal dimensions are 50 on each side.
It is about 1000 mm. In addition, a reaction gas flow channel groove 11 is formed in the center thereof. The reaction gas flow channel groove 11 is provided within a predetermined range from the central portion of the separator 10 on both surfaces or one surface of the separator 10.
For example, a large number of parallel portions or meanders are formed at a fine pitch. The separator 10 is required to have excellent gas barrier properties that do not allow permeation of supplied hydrogen and oxygen gases and to have high strength, and to be highly conductive because it is an electrode of a fuel cell. It

Next, carbonaceous powder and a binder will be described as each member constituting the fuel cell separator of the present embodiment. First, graphite powder is usually used as the carbonaceous powder. The graphite powder is not particularly limited, such as scaly, granular, lumpy, earthy natural graphite, petroleum coke or pitch coke as a main raw material, and kneaded, molded, fired, lumped or the like produced by graphitization. Artificial graphite and the like, which are crushed as necessary, and expanded graphite and the like can be used.

The carbonaceous powder such as the graphite powder is electrically conductive,
From the viewpoint of battery performance and the like, those having an ash content of 1% by weight or less, particularly 0.5% by weight or less are preferable. The content of alkali metal, alkaline earth metal, and transition metal is 500.
It is preferably ppm or less, particularly 100 ppm or less.

The volatile content in the carbonaceous powder is preferably 2% by weight or less, more preferably 1% by weight or less from the viewpoints of the surface smoothness of the separator 10 and the battery performance. The fixed carbon content is preferably 98% by weight or more, and 99% by weight.
The above are particularly preferable.

The particle diameter of the carbonaceous powder is preferably 1000 μm or less, more preferably 500 μm or less, and particularly preferably 300 μm or less, from the viewpoint of separator performance and the like. This is because if the maximum grain size is too large, defects will occur in the structure. However, in view of the moldability and performance of the separator 10, it is preferable not to include fine powder. This is because if there is a large amount of fine powder, it is difficult to degas, and defects are likely to occur. Therefore, the lower limit of the average particle size is 1 μm or more and 3 μm.
m or more, 5 μm or more, the upper limit is 100 μm, 70 μm, 5
It is preferably 0 μm.

Next, the binder will be described. The binder is not particularly limited, and resins such as thermoplastic resins and thermosetting resins, rubbers, thermoplastic elastomers, and mixtures thereof can be used.

As the thermoplastic resin, saturated polyester resin, styrene-acrylic 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, fluororesin, phenoxy resin, urethane resin, block copolymer weight of these resins A combination, a mixture thereof, and the like can be used.

As the thermosetting resin, phenol resin,
An epoxy resin, an unsaturated polyester resin, a melamine resin, a urea resin, a diallyl phthalate resin, a mixture thereof, or the like can be used.

As the phenol resin, novolac resin, resol resin, and modified resins thereof such as rubber modified phenol resin are used. High low molecular weight (distribution) causes defects during curing. Further, if a large amount of condensed water or the like is generated (a structure such as a side chain, a ring structure), defects are generated after curing. As this rubber-modified phenolic resin, one that can be obtained by reacting an unvulcanized rubber with a phenolic resin is used. Here, as the unvulcanized rubber, fluororubber, silicone rubber, butyl rubber, chloroprene rubber, nitrile rubber, nitrile chloroprene rubber, chlorinated butyl rubber, chlorinated polyethylene, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-acrylic glycidiether Three-dimensional copolymer, urethane rubber, acrylic rubber, ethylene-propylene rubber, styrene rubber, butadiene rubber,
One kind selected from natural rubber or a mixture of two or more kinds or a copolymerization reaction product is adopted.

As the novolac resin, phenol, o
-Cresol, m-cresol, p-cresol, 2,
5-xylenol, 3,5-xylenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, t
ert-butylphenol, 1-naphthol, 2-naphthol, 4,4′-biphenyldiol, bisphenol A, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol,
At least one of phenols such as phloroglicinol under acid catalysis, for example, 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. A resin that has been polycondensed with the seed can be used. Further, the resole resin is a resin that is polycondensed in the same manner except that an alkali catalyst is used instead of the acid catalyst in the polycondensation of the novolak resin.

Among the phenolic resins, when a novolac resin is used, a curing reaction occurs when a curing agent is used, and when a resole resin is used, a curing reaction occurs without using a curing agent.
It becomes a cured product. Therefore, when a novolac resin is used as the phenol resin, a curing agent is used to separate the separator 1
It is desirable to cure at the time of 0 pressure molding.

As the curing agent, 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 resin or the like is used.
If the dispersion is poor, the curing will be uneven and the uniformity will decrease. Further, when the amount of the curing agent is small, curing is insufficient and defects occur, but usually 5 to 1 with respect to the total amount with the novolac resin.
A proportion of 0% by weight is preferred.

Examples of 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. Elastomers, mixtures thereof and the like can be used. In particular, 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 hydrogenated derivative thereof, styrene butadiene block copolymer and hydrogenated derivative thereof, styrene butylene block copolymer, polyetherester block copolymer, polyesterester block copolymer, poly Ether block amide copolymers, mixtures thereof and the like can be used.

These rubbers may be crosslinked at the time of molding with a crosslinking agent, and as the crosslinking agent, sulfur, peroxide and the like are used, but peroxide is preferable. In such a case, it is preferable to sufficiently disperse. Further, in the case where the binder is a thermoplastic resin added with a crosslinking agent, a thermoplastic elastomer or a rubber added with a vulcanizing agent, a crosslinking reaction is caused by the crosslinking agent (vulcanizing agent) to give a cured product.

Although the types of binders have been described above, preferred binders are phenol resins among thermosetting resins, polyolefin resins among engineering resins, engineering plastics, etc. Among rubbers, ethylene propylene rubber, isoprene rubber, styrene butadiene rubber, butyl rubber, and among thermoplastic elastomers, hydrogenated derivatives of styrene butadiene block copolymers are preferable.

Among them, those which do not cause defects in the molded product due to generation of decomposition gas under the conditions of heating and pressure molding,
For example, heating loss (50 to 1 when heating from room temperature to 150 ° C. at a heating rate of 5 ° C./min in a nitrogen gas atmosphere)
It is preferable to select a resin whose weight loss at 50 ° C.) is 2% by weight or less, for example, a thermoplastic resin, a thermoplastic elastomer, or a mixture thereof.

The particle size of these binders is preferably the same as or smaller than the particle size of the carbonaceous powder, and is 0.5 to 1.2 times the particle size of the carbonaceous powder, preferably Has a particle size of 0.6 to 1.1 times, and more preferably 0.7 to 1.0 times. However, if the particle size is too small, air is included between the carbonaceous powder and the binder to increase the bulk, and a large amount of air is likely to cause defects, so 1 μm or more is preferable. On the other hand, if the particle size is too large, the dispersion of the binder locally exists and the uniformity deteriorates.

The amount of the binder used is 10 carbonaceous powders.
It is preferably 1 to 60 parts by weight with respect to 0 parts by weight,
It is more preferably 1 to 30 parts by weight. When a thermosetting resin is used as the binder, the amount is preferably 5 to 30 parts by weight, and more preferably 5 to 15 parts by weight, based on 100 parts by weight of the carbonaceous powder. When a thermoplastic resin, rubber, or thermoplastic elastomer is used, the amount is preferably 1 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the carbonaceous powder. When the amount of the binder used does not fall within this range, the mechanical strength of the obtained separator 10 tends to be poor, and when it exceeds this range, the performance such as conductivity of the separator 10 tends to be impaired. is there. In the thermosetting resin, the gas vent hole becomes a defect.

Next, the mixing of the carbonaceous powder and the binder will be described. Here, it is particularly important to uniformly mix, and if necessary, a curing agent, a crosslinking agent, etc. are added,
Mix and knead. As the mixing device, a mixing device that is difficult to pulverize in a state where the viscosity is lowered is desired so that kneading can be performed without pulverizing. For example, a mixer such as a tumbler blender, a ribbon blender, a V-type blender, a Henschel mixer, a high-speed mixer, and a rotation type mixer (for example, a planetary mixer) can be used for uniform mixing, or a single-screw or twin-screw extruder, roll, Banbury. A kneading machine such as a mixer, a kneader or a Brabender can be used.

The conditions for mixing are to heat the mixture at a temperature of about 300 ° C. or lower while improving the wettability of the carbonaceous powder graphite and the binder, while ensuring a sufficient decrease in viscosity. In addition, by previously moistening the carbonaceous powder with an organic solvent or an aqueous medium, the carbonaceous powder and the binder can be more uniformly mixed, and a separator 10 having more uniform properties can be produced. You can For the same reason, the binder is preferably mixed as a solution of an organic solvent or an aqueous medium (a binder that dissolves in the solvent) or a dispersion (in the case of a binder that does not dissolve in the solvent). It becomes possible to disperse thinly by diluting.

Here, as the organic solvent used for wetting the carbonaceous powder and for making the binder solution or dispersion liquid, those which are easily wettable with the graphite which is the carbonaceous powder are preferable, and those which dissolve the resin are preferable. For example, butane, pentane, hexane, heptane, alkanes such as octane, cyclopentane, cyclohexane, cycloheptane,
Cycloalkanes such as cyclooctane / methanol, ethanol, propanol, butanol, amyl alcohol, hexanol, heptanol,
Alcohols such as octanol, decanol, undecanol, diacetone alcohol, furfuryl alcohol, and benzyl alcohol ・ Methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, etc. ・ Propylene glycol monomethyl ether, propylene glycol monoethyl Propylene glycols such as ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol dimethyl ether, acetone, methylaminoketone, cyclohexanone,
Ketones such as acetophenone, dioxane, ethers such as tetrahydrofuran, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, lactic acid Esters of ethyl, methyl 3-methoxypropionate, etc., halogenated hydrocarbons such as chloroform, methylene chloride, tetrachloroethane, etc., aromatic hydrocarbons such as benzene, toluene, xylene, phenol, cresol etc., dimethylformamide, dimethylacetamide. , N-
Examples include high polar solvents such as methylpyrrolidone.

Of these, the organic solvent used for the binder is preferably one that easily wets carbonaceous powder such as graphite,
Those that dissolve the binder are preferable. Further, those having a solubility index similar to that of the binder are also preferable. In particular, alcohols are preferable for thermosetting resins such as phenol resins, and aromatic hydrocarbons are preferable for thermoplastic resins such as polyolefin resins, and rubbers and thermoplastic elastomers.

The aqueous medium used for wetting the carbonaceous powder and for making the binder solution or dispersion is not particularly limited, but water or alcohols is usually used. When using water, a surfactant or the like can be added so as to improve the wettability with graphite. It is also possible to use a mixture of an organic solvent and an aqueous medium. The mixing ratio may be arbitrary, but usually the organic solvent / aqueous solvent is 1/100.
It is about 100/1. In addition, 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, and it is particularly preferable to use the same organic solvent or aqueous medium. .

Here, the amount of the organic solvent or the aqueous medium used for wetting the carbonaceous powder is 100 carbonaceous powder.
It is preferably 1 to 300 parts by weight with respect to parts by weight,
The concentration of the binder in the binder solution or dispersion is preferably 1 to 90% by weight. In terms of energy efficiency, the smaller the amount, the better.

On the other hand, when a binder curing agent or a cross-linking agent (vulcanizing agent) is used, there are several mixing methods. First, as the first method, a curing agent and a cross-linking agent (vulcanizing agent) are added to carbonaceous powder (or a wet product thereof) and dispersed, and then a binder (or a solution of an organic solvent or an aqueous medium thereof). Alternatively, the dispersion is added and mixed. Also,
A second method is to mix a carbonaceous powder with a binder (both may be wet at this time), and then add a curing agent or a crosslinking agent (vulcanizing agent) later. This method requires good dispersion of the curing agent. Furthermore, the third
As the method, the binder is mixed with the curing agent or the crosslinking agent (vulcanizing agent) first, and the carbonaceous powder (or its wetted material) is mixed later. In such a method, since the binder and the curing agent are mixed first, it is preferable to use them after mixing and before curing. Although any method may be used, it is preferable to use it by mixing it with a wet material of carbonaceous powder, and uniform mixing is important.

Next, the drying of the mixture will be described. The mixture obtained by mixing the carbonaceous powder, the binder, and the curing agent or the cross-linking agent (vulcanizing agent) becomes a wet state, a paste state, or a lump state. Therefore, this mixture is appropriately dried by heating prior to pressure molding under heating. Here, the heating temperature may be a temperature at which the used organic solvent or aqueous medium can be evaporated and the binder does not deteriorate. Usually, it is preferable that the solvent is volatilized at a temperature of 200 ° C. or lower, and the mixture is dried until the content of the organic solvent or the aqueous medium in the mixture becomes 1% by weight or less. When this content is large, it becomes a gas release defect after molding.

Here, the mixture is pulverized after heating and drying, but after heating and drying, it usually becomes non-uniform granules or agglomerates, so this granules or agglomerates should be roughly pulverized for sieving. Is required. First, as the crushing device, a mixer, a jaw crusher, a gyratory crusher, a roll mill, a sample mill, a jet mill, a hammer mill, an impeller breaker, or the like is used. Further, if the crushed particle size is large, it is difficult to uniformly heat the inside by heat conduction and it is difficult to melt and deform, so that defects are likely to occur after molding and bonding. On the other hand, if it is too fine, it is bulky, contains air, is difficult to be deaerated, and tends to have defects. Therefore, the maximum particle size is less than 3 mm, preferably 0.1 to 2 mm, more preferably 0.5 to 1 mm.

When mass-producing the granules produced as described above, the granules may be continuously fed into a heating furnace for continuous heating. As a heating furnace,
For example, a horizontal or vertical continuous furnace is used. As a method of introducing the mixed raw material into the heating furnace, there are a method of directly introducing the mixed raw material into the furnace and a method of introducing the mixed raw material into a container such as a tray which can be appropriately transported. Further, it may be filled in a molding die which is a die processed to have a desired shape and introduced into a heating furnace.

At this time, a mold release agent is appropriately applied to this molding die as thinly as possible. There is no particular limitation on the method of filling the mixed raw material into the molding die, but industrially, after the mixed raw material is put into the hopper, a fixed amount is put into the molding die, and an appropriate auxiliary tool is used to A method is adopted in which the mixed raw material is spread to every corner according to the shape. At this time, the mixed raw material is spread over the surface in a smooth manner or, if there is a step, according to the height.

Here, the molding die is used in the case of molding the separator 10 in which the reaction gas channel groove 11 having a large number of parallel portions is formed on at least one plate surface as shown in FIG. A molding die in which a large number of linear blanks are provided in parallel on the inner surface of the die corresponding to the reaction gas flow channel groove 11 may be used. The heating atmosphere needs to be uniformly heated and may be performed in air, but an atmosphere gas such as N ₂ or Ar may be used as necessary.

Next, the heating temperature will be described. The heating temperature is near the desired molding temperature. The temperature around the molding temperature needs to be a temperature that does not exceed the decomposition point of the binder. Further, when molding, in consideration of the melting temperature of the resin, the glass transition point (Tg), etc., it is 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
℃). Further, when the temperature is higher than the desired molding temperature, it may be appropriately cooled and pressure-molded. In such a case, the heating equipment for pressure molding can be omitted, which is industrially advantageous. When pressure molding is performed without heating,
Although the temperature gradually decreases from the pressure molding to the depressurization, in order to shorten the time until die cutting and efficiently manufacture the separator 10, cooling from an early stage is more advantageous. . However, if the temperature lowers below the glass transition point (Tg) during the pressure molding process, the moldability is impaired. In some cases, a heat insulating material is provided in the pressure molding machine to reduce the temperature. It may be suppressed.

As for the mixed raw material, it is sufficient that the entire mixed raw material reaches a desired temperature before pressure molding. For example, there are a method of introducing the mixed raw material into a heating furnace set to a desired temperature, a method of introducing the mixed raw material into the furnace, and then gradually heating. In addition, this heating temperature can be easily controlled by confirming it with a surface thermometer or a thermometer provided in a molding die and adjusting the temperature of a heating furnace or a heating device provided in a pressure molding machine. it can.

The pressure molding machine is not particularly limited, but when a plurality of molding dies are introduced into the pressure molding machine, a plurality of molding dies are taken (side by side, a plurality of molding dies are simultaneously pressure-molded. ) Or a multi-stage (a plurality of stages vertically, placing a molding die and pressing simultaneously) is adopted.

Next, the molding pressure and the molding temperature in the pressure molding machine will be described. The molding pressure and the molding temperature are set such that the gas is sufficiently released from the object to be molded, and the carbonaceous powder and the binder are sufficiently fused, depending on the types and blending ratios of the carbonaceous powder and the binder used. Therefore, it is appropriately set so that the obtained molded body is not deformed such as cracked or warped. In general, if the molding temperature is high, lower pressure is sufficient,
If the molding temperature is lower, the pressure will be higher.

First, the molding pressure is usually 40 to 4
The pressure is preferably 00 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, and defects tend to occur.
Further, if the molding pressure exceeds the above range, burrs, which are protrusions of the molding target from the molding die, are likely to occur. When this burr is generated, a corner chip may occur during deburring.

Next, the molding temperature is usually the glass transition point of the binder used for molding into a desired shape.
The temperature exceeds (Tg). In addition, the separator 10
In order to perform molding without roughening, chipping, cracking, or deformation (warping or swelling) of the surface, the temperature is preferably lower than the decomposition point of the binder. Here, the temperature exceeding the Tg of the binder means
When two or more binders are mixed and used, T
It means that it exceeds the Tg of the binder with the lower g,
It is desirable to exceed the weight average Tg corresponding to the mixing ratio of plural kinds of binders.

At the lower limit of the molding temperature, in order to mold a thin plate-shaped ribbed separator without roughening, chipping, cracking, or deforming (warping or swelling) of the surface with a good yield, (Tg + 20)
C.) or higher, preferably (Tg + 30.degree. C.) or higher, more preferably the melting point (Tm) of the binder or higher, and particularly preferably (Tm +
20 ° C.) or higher, and particularly preferably (Tm + 30 ° C.) or higher. Regarding the high melting point resin, which is similar to so-called engineering plastics, as a binder, J
18.6 kg / cm ² (= 1.
The temperature may be equal to or higher than the deflection temperature under load of 82 MPa). However, if the molding temperature is excessively high, the flowability of the molded article becomes too high, burrs are easily generated, and the dimensional stability of the obtained molded article becomes poor.

Further, although it is the upper limit of the molding temperature, the heat load on the molding die becomes large and it is also disadvantageous for the cooling until the die cutting in the subsequent step. Therefore, the decomposition point of the binder is usually used. Less than,
Particularly, (Tm of binder + 100 ° C.) or less, and particularly (Tm of binder + 50 ° C.) or less are suitable. For example 50-40
The temperature is 0 ° C., particularly about 100 to 300 ° C. Here, the decomposition point of the binder is DSC method or TG-D.
5 ℃ / min under nitrogen gas atmosphere by TA method thermal analysis
It indicates the temperature at which heat absorption or heat generation starts when heated from room temperature at the heating rate.

As a pressure molding method, for example, there is a method in which after heating while moving in a heating furnace, it is introduced into a pressure molding machine and left to stand to perform pressure molding. There is also a method of performing pressure molding while moving in a pressure molding machine.

After the pressure molding by the pressure molding machine, depressurization is performed by this pressure molding machine. The depressurization may be performed while moving in the pressure molding machine, or the depressurization can be performed in a stationary state. At this time, the depressurization may be performed so as to continuously reduce the pressure, or may be performed so as to reduce the pressure stepwise. Further, if air is sufficiently released during pressure molding, deformation such as swelling and cracks are less likely to occur, and thus depressurization can be performed without cooling. However, if the air is difficult to escape, deformation and cracking such as swelling are likely to occur when decompressing at high temperature. Therefore, it is desirable to depressurize after cooling to some extent or while cooling.

When cooling at the time of depressurization, if the temperature is cooled to an excessively low temperature, the occupying period of the pressure molding machine becomes long and the productivity is likely to decrease. Further, if the cooling is stopped at an excessively high temperature, the effect due to the cooling cannot be obtained and there is a possibility that deformation such as swelling or cracking may occur. The cooling temperature during depressurization is preferably lower than Tg because if the temperature is too low, the molded product becomes glassy and brittle, and chipping easily occurs during deburring.
Specifically, the temperature at the end of pressure molding is usually several to 150 ° C. lower, preferably 5 to 100 ° C. lower, and the melting point (Tm) or less of the binder used, It is preferably (Tm−50 ° C.) or less and (Tg of binder + 30 ° C.) or less. Furthermore, by starting the cooling from the time when the press molding is started, the temperature can be lowered to the Tm or lower of the binder more quickly, and the pressure can be released at an earlier stage, for example, at the end of the pressure molding, The occupation period of the pressure molding machine can be shortened.

If deaeration treatment (vacuum pump or the like) is performed prior to pressure molding in a pressure molding machine, a dense molded body can be obtained and deformation such as swelling or warping can be suppressed. It is preferable from the point. Specifically, for example, 40,000 Pa
(300 Torr) or less, especially 27,000 Pa (200 T
It is preferable to carry out the degassing treatment at a pressure of not more than orr), particularly not more than 5000 Pa (37 Torr), especially not more than 1300 Pa (10 Torr).

The timing of the degassing process is as follows.
After mixing the carbonaceous powder and the binder, before heating the mixed raw material, during heating by the heating furnace, after heating by the heating furnace, before being introduced into the pressure molding machine, after being introduced into the pressure molding machine,
It can be performed either before the pressure molding is started or after the pressure is started and before the pressure molding is completed. Moreover, it can be performed in one or more of these steps, and further, can be continuously performed in a plurality of steps. However, in order to efficiently remove air and gas, it is preferable to perform deaeration treatment immediately before pressing.
It is also possible to perform preforming simultaneously with the degassing process.

Here, in the above degassing treatment before heating,
Since the gas contained in the mixed raw material can be removed and the distance between the particles can be reduced, the bulk density can be increased and a dense compact can be obtained, and the physical properties such as strength and volume resistivity of the compact can be improved. Has the effect of Further, in the above-mentioned, in the degassing process from the heating to the start of pressure molding,
Not only can the gas contained in the mixed raw material be removed to reduce the distance between particles, but also the gas substance generated by heating can be removed, so that the physical properties of the molded body can be further improved. Among them, the above-described degassing treatment is most effective in improving the physical properties of the molded body because it has the highest effect of removing the gas contained in the mixed raw material and the gas substance generated by heating. Further, in order to reduce the time occupied by the pressure molding machine, the above timing is preferable because the degassing process can be performed simultaneously with the pressure molding. still,
When continuously performing degassing treatment in a plurality of steps, it is preferable to perform degassing treatment from an earlier stage because more effects can be obtained, and specifically, the above-mentioned is preferable, and the above-mentioned Is more preferable.

After performing this deaeration process, deaeration release is carried out. This deaeration opening may be performed all at once or gradually. Further, deaeration and release in the case of deaeration during pressure molding may be performed in a state in which air is released and the carbonaceous powder and the binder are sufficiently fused, and therefore cooling is performed even during cooling. It may be later. Furthermore, the degassing process before introducing into the pressure molding machine is performed by degassing in the same mold as the press molding, or in a mold close to the final shape omitting the fine shape, so that the bulk density is reduced. Since the height can be increased and the shape can be adjusted, it is possible to obtain an effect that the handling property is improved when the product is taken out from the mold and transported to the next step.

Further, the shape retention can be carried out before the pressure molding. In the shape retention, handleability can be improved by preforming by using the same mold as that used for pressure molding or a mold close to the final shape in which a fine shape is omitted and adjusting the shape. The preforming pressure for this shape retention is usually 2
0 to 300 MPa, preferably 20 to 200 MP
a. Further, the preforming temperature for shape retention is not particularly limited as long as it is a temperature below the decomposition point of the binder, and heating at room temperature does not require a heating operation, which is industrially advantageous. Here, 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 1.4~1.8g / cm ^3. It should be noted that this pre-molding, even before heating the mixed raw material,
After heating, it may be before introduction into the pressure molding machine. However, if the surface of the molded body becomes dense and defects such as gas remain inside, the defects may not be sufficiently removed during vacuum deaeration and pressure molding. Therefore, it is preferable that the surface is not densified and gas is easily released. In particular, when preforming after heating, it is desired to lower the forming pressure to prevent the surface from becoming densified.

After the pressure molding and depressurization, the molding die is taken out from the pressure molding machine, and the obtained molding is taken out from the molding die. First, regarding the die-cutting temperature, it is preferably performed after the temperature has dropped to a temperature lower than the glass transition point (Tg) of the binder. Binder T
This is because at a temperature of g or more, the molded body is likely to be deformed at the time of die-cutting, which causes defects such as cracks, swelling, and warpage, and makes it difficult to obtain the original function of the separator. Although the die cutting can be performed by cooling to room temperature, cracking and deformation due to die cutting can be suppressed if the temperature is lower than the Tg of the binder by 5 ° C. or more, and especially lower than Tg by 10 ° C. or more. . Therefore, in order to shorten the occupation time of the molding die, the die-cutting is performed at (Tg-5 ° C) or less, particularly (Tg-10 ° C) or less, for example, (Tg-20 ° C) to (Tg-80 ° C). It is preferable to carry out. Further, if the temperature is too low, the molded body becomes brittle and may cause corner breakage, so a temperature lower than the Tg of the resin and close to Tg is preferable. 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.

Here, as the cooling until the die cutting, the molding die may be left to cool naturally. Further, when forced cooling is carried out by adopting an appropriate cooling means such as low-temperature gas or refrigerant spray, it is preferable in that the rotation rate of the molding die can be increased and the productivity can be improved. Cooling when the molding die is taken out from the pressure molding machine may be performed in any step after depressurization after pressure molding, during depressurization, and after depressurization. In particular, when the die-cutting is sequentially performed by a continuous operation, the occupying period of the molding die can be shortened, and the productivity can be further improved, which is preferable.
For example, a method of passing a molding die after depressurization through a cooling zone while continuously moving it on a belt conveyor, or one or a plurality of molding dies are moved batchwise into a cooling chamber. After cooling, there is a method in which it is moved by a belt conveyor or the like and discharged.

Whether the cooling is performed before the depressurization, during the depressurization, or after the depressurization, the cooling rate depends on the types of carbonaceous powder and binder, the mixing ratio, and the heating temperature. It is appropriately set depending on the pressure molding conditions and the like. However, if a binder that does not generate decomposed gas or foams under heating and pressurization is used as the binder and the cooling rate can be increased, the die can be removed quickly and the molding die occupies. It is preferable because the period can be shortened.

The cooling rate is such that after the pressure molding, before the depressurization, during the depressurization, or after the depressurization, the temperature is cooled to a temperature suitable for die cutting at a predetermined rate. For example, 0.0
3 ° C / sec (= 1.8 ° C / min) or more, preferably 0.0
It is 4 ° C / sec or more. Further, in order to shorten the time until die-cutting, 0.05 ° C./sec or more, preferably 0.0
It is 1 ° C / sec or more. Furthermore, the upper limit is usually 1
It is not higher than 00 ° C / min.

In the present embodiment, by strictly selecting and controlling the powder molding conditions from the above conditions, it is possible to obtain the separator 10 with less variation and excellent uniformity. That is, by selecting molding conditions, it is possible to produce an industrially advantageous fuel cell separator having excellent physical properties in terms of both performance and quality. This is realized, for example, by a combination of condition selections as shown in the embodiments described later.

As described above, the plate-shaped separator 10 thus obtained has a size and shape of 50 to 1000 mm in length and width, especially 80 to 500 mm, and 0.5 to several tens mm in thickness. 1 to 10 mm, bulk density is 1.8 g / cm ³ or more, and especially 1.9 to 2.2 g / cm ^3.
That is all. In particular, it is suitable for manufacturing a plate-shaped fuel cell separator in which one or both plate surfaces of such a plate-shaped separator 10 are formed with grooves for reaction gas passages having a large number of parallel portions.

As a point of caution, first, the amount of the binder (binder) that increases (deteriorates) the volume resistivity should be reduced as much as possible, and the carbon powder should be used effectively as a binder. Preferably. Therefore, at the time of mixing, the binder is allowed to efficiently enter the voids formed by the carbonaceous powder, and the binder is thinly and uniformly spread on the surface of the carbonaceous powder. Then, in molding, by heating and pressurizing (compression molding), the mold is charged as uniformly as possible. At this time, if the heights of the grooves and the like are different, the height of the charging amount and the like can be adjusted, and in some cases, it is possible to partially consolidate. And the removal of air contained in the powder,
Control of molding conditions such as material selection, heating, pressurization, degassing, cooling, and die cutting temperature and their combination so that gas generation due to melting of the binder is suppressed or the generated gas is degassed. It may be performed while adjusting the timing. Thus, in order to obtain a highly uniform fuel cell separator with less variation, uniform dispersion of carbonaceous powder such as graphite and a binder, uniform charging, efficient degassing, removal of large defects, It is preferable to achieve appropriate molding conditions, depressurization, and uniformity of the structure by cooling.

Here, as an example of optimization in compression molding, first, it is preferable to improve the surface wetting of the carbonaceous powder as a raw material by a wet treatment or the like to improve the compatibility with the binder. Further, as the binding material, a material that easily generates gas causes defects in the separator 10,
Those that generate less gas by heating are preferable. For example,
Phenolic resin tends to generate water and low molecular weight. In this respect, the thermoplastic resin is preferable to the thermosetting resin.
In addition, it is possible to reduce the amount of gas by molding a small amount of gas that generates a large amount of gas. Furthermore, in the relationship between the carbonaceous powder and the binder, the particle size of the carbonaceous powder is small,
When the distribution is wide, the average particle diameter of carbonaceous powder, the distribution and the amount of binder can be optimized by relatively increasing the amount of binder and uniformly covering the surface. On the other hand, when the particle size of the carbonaceous powder is too large, the number of defects increases and the uniformity deteriorates.

As an optimization in compression molding, next, in the method of mixing the carbonaceous powder and the binder, it is necessary to blend the binder and the carbonaceous powder so as to be uniform. As a method of this blending, a method of wetting the carbonaceous powder with a solvent and a method of lowering the viscosity of the binder by heating,
Solution of the binder with a solvent or dispersion medium, or dispersion of the binder,
Examples include a method of thinly coating with a dilute solution by dilution, an efficient mixing method by kneading, a mixing device, and optimization of mixing time. It is preferable that this mixing is sufficiently performed, and an efficient mixing method is selected depending on the mixing time, the mixer, selection of solvent wetting, temperature conditions, and the like. In addition, it is preferable to uniformly mix the carbonaceous powder and the binder, including the hardener. Here, it is preferable that the mixed product is uniform, and it is particularly preferable that the graphite powder surface is sufficiently covered with the binder for uniform mixing.

It is preferable to optimize the particle size of the granulated product to be put into the mold. If the particle size is too large, it does not melt sufficiently in the mold, it does not flow, and defects remain. If the particle size is too small, the air content is too large and deaeration takes time. In the mold injection, it is preferable to uniformly inject, and it is also effective to smooth the surface. Depending on the case, it is also effective to form a step such as a groove or to partially consolidate.

Under the molding conditions (degassing, temperature, pressure, time), it is preferable to sufficiently degas the gas and air. When the molding particle size is small, it is effective to sufficiently degas. The molding temperature is preferably a temperature (Tm or higher) at which fusion is sufficiently performed. Further, by increasing the molding pressure, defects can be suppressed and reduced, and the size can be suppressed so as not to affect the strength and the like. The defects are 10 μm or less, preferably 5 μm or less, and most preferably 1 μm or less. For die cutting, depressurize in the solidified state (molding pressure release)
Preferably. Since depressurization at high temperature deteriorates the product and swells the gas, the glass transition temperature (Tg) or lower is preferable. However, if it is too low, the product will be stiff, and it may be glassy and chip off when deburring.

Next, each measurement of fracture energy, maximum bending stress, maximum bending stress strain, bulk density, volume resistivity, etc. will be described. First, in terms of breaking energy, JIS K
A bending stress deflection curve is created according to 7171.
The point of maximum bending stress on the created bending stress deflection curve,
The strain at that time (point on the x-axis: maximum bending stress strain) and the area of a triangle formed by the three points of the origin were measured. At this time, the maximum bending stress and the maximum bending stress strain were measured in accordance with JIS K 7171 by inserting a test piece having a length of 100 mm, a width of 10 mm and a thickness of 5 mm into the end portion and the center portion of the plate, and A test piece was cut out from a fuel cell separator as a molded body, and the test piece was measured by applying an indenter to the plate surface of the separator 10 with a fulcrum distance of 80 mm and a test speed of 5 mm / min. Avoid the hole for stacking and scrape the rib part for the ribbed part
(It is considered that there is at least 1 mm even if the rib part is cut), and measure as a flat plate.

The coefficient of variation calculated for each physical property is obtained by the average value of standard deviations of values (maximum bending stress, fracture energy, etc.) / Values, and at least 3 points (2 points at the end + 1 point at the center), if possible. Do at least 5 points. By calculating the coefficient of variation, it is possible to grasp the variation in physical properties and the level of uniformity.

Next, the preferable range of each physical property value and its variation coefficient will be described. First, the value of the maximum bending stress (bending strength) is usually 10 MPa or more, preferably 15 MPa or more, and more preferably 20 M.
Pa or higher. Although there is no particular upper limit, it is considered difficult to produce a material having a pressure of 200 MPa or more. If the lower limit of these is exceeded, when the separator 10 is held horizontally,
It may be damaged during handling such as mounting or tightening,
It is easily deformed by heat when used.

The coefficient of variation in the maximum bending stress (bending strength) is usually 0.10 or less, preferably 0.08 or less, more preferably 0.05 or less, and particularly preferably 0.0.
It is 03 or less. The lower limit is the better, but usually,
There is about 0.0001. If the upper limit of these values is not satisfied, a low-strength portion exists, and a weak portion is easily broken due to lateral holding or handling during mounting. Further, it is easily damaged by thermal deformation during use.

Next, in the value at the maximum bending stress strain,
The upper limit is usually 5 mm or less, preferably 3 mm or less, and the lower limit is usually 0.4 mm or more, preferably 0.6 mm.
The above is more preferably 0.8 mm or more, and particularly preferably 1 mm or more. If this lower limit is exceeded, it becomes difficult to deform and becomes brittle, and it is likely to be damaged during handling such as lateral holding, mounting, and tightening, or easily damaged due to thermal deformation during use. There is no particular problem with the upper limit.

The coefficient of variation in the maximum bending stress strain is usually 0.10 or less, preferably 0.07 or less, more preferably 0.05 or less, and particularly preferably 0.0.
It is 3 or less. The lower the lower limit, the better.
There are about 0001. If these upper limits are not satisfied, when the separator 10 is assembled in the fuel cell, the portion that is deformed and intolerable undergoes excessive deformation and is easily broken. Also, it is easily damaged by thermal strain.

Next, with respect to the value of the breaking energy, there is no particular upper limit, but there is about 50 MPa · mm (in some cases, 30 MPa · mm). The lower limit is usually 6
MPa · mm or more, preferably 8 MPa · mm or more, more preferably 10 MPa · mm or more, particularly preferably 12 MPa · mm or more. If the value goes below the lower limit, it becomes difficult to deform and becomes brittle.
There is a risk of damage during handling and thermal deformation during use.

The coefficient of variation in this breaking energy is
It is usually 0.12 or less, preferably 0.10 or less, more preferably 0.08 or less, and particularly preferably 0.06 or less.
Regarding the lower limit, the smaller the better, the more preferable it is.
There are about 0001. If the value exceeds the upper limit, there is a portion having low resistance to deformation (fracture toughness), and the separator is likely to be damaged when the separator 10 is incorporated in the fuel cell, stacked and tightened. In addition, it falls and becomes easy to break (partial defect control).

Next, the measurement of the bulk density will be described. As a test piece, a length of 100 is used in accordance with JIS K7171.
mm, width 10 mm, thickness 5 mm (in the examples described later,
A flat plate having a vertical and horizontal length of 100 mm each and a thickness of 5 mm is cut into a height of 5 mm, a width of 10 mm and a length of 100 mm, and an average of 5 points, including the center portion from the end, is cut out. At this time, insert the end and center of the plate,
Sample the rest at equal intervals (minimum 3 points, 5 points, 9 points)
Points ...). Although avoiding the hole for stacking, even if it has ribs, it can be used as a test piece as it is. In the measurement of bulk density (measurement according to a standard method), in the case of a flat plate, the volume is measured by the width × height × length of a rectangular parallelepiped, and the bulk density is calculated by the obtained weight. If the dimensions cannot be measured with holes, grooves, etc., calculate the bulk density from the excluded volume and weight in water.

The upper limit of the value of the bulk density is not particularly limited, but is about 2.2 g / cc. The lower limit is usually 1.
It is 90 g / cc or more, preferably 1.95 g / cc or more, and more preferably 2.0 g / cc or more. If the value goes below the lower limit, the denseness tends to decrease, and the gas barrier properties and mechanical properties tend to decrease.

The coefficient of variation of this bulk density is usually 0.01 or less, preferably 0.008 or less, more preferably 0.00.
It is 6 or less. If the upper limit is not satisfied, a portion having a low bulk density is present and a portion having a low density is generated, so that the gas barrier property and the mechanical properties are deteriorated. Both of these characteristics are dominated by partial defects. The smaller the lower limit, the better, but normally there is about 0.0001.

Next, the measurement of the volume resistivity will be described. The 4-probe method (Loresta MP manufactured by Mitsubishi Kagaku) was used as the method for measuring the volume resistivity. The test piece is 100 vertical
mm, width 100 mm, and thickness 5 mm were used to measure 9 points of upper middle lower, left middle right. Since it is a non-destructive test, it has nothing to do with the shape itself and can be measured even with an actual product.
Although the hole for stacking was avoided, even if it had a rib, it was used as it was as a test piece. As the measurement conditions, for a test piece of 100 mm in length and width and 5 mm in thickness,
The length, width, measurement position, thickness, and width of the four probes were input, and numerical values were output in the measurement. Here, the coefficient of variation of the volume resistivity is calculated by standard deviation of volume resistivity (9 points) / average value.

The upper limit of the volume resistivity is 20 mΩ.
-Cm or less, preferably 15 mΩ-cm or less, more preferably 10 mΩ-cm or less. If the upper limit is exceeded, the electrical resistance will increase and the battery characteristics will deteriorate. Further, thermal distortion is likely to occur due to partial heat generation. The lower limit is preferably as low as possible, but is usually about 1 mΩ · cm or more.

The coefficient of variation of this volume resistivity is usually 0.
10 or less, preferably 0.08 or less, and more preferably 0.0.
It is 06 or less. If the upper limit is exceeded, the contact resistance may fluctuate and the flow of electricity may be uneven, resulting in a decrease in power generation efficiency, deterioration of the material due to local heating, and thermal distortion.

As described above, in the fuel cell separator to which the present embodiment is applied, warping, swelling, and cracking are achieved by making the physical properties of the molded product such as strength and volume resistivity more uniform and suppressing variations. It is possible to obtain a high-performance separator 10 that suppresses such deformation.

[0085]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 Natural graphite powder (average particle size 13 μm) 5 k as carbonaceous powder
Styrene-based elastomer (hereinafter SEBC), which is a hydrogenated derivative of a commercially available styrene-butadiene block copolymer (styrene content ratio of about 30% by weight), is charged into a 20-liter vertical high-speed mixer while rotating a rotary blade. 25
A solution of 0 g dissolved in 1000 cc of toluene was added and mixed for 10 minutes. SEBC has a Tg of 100 ° C. This mixture was dried at 110 ° C. for 6 hours or more until the toluene odor disappeared, and after sieving with a maximum particle size of 1 mm,
The upper part of the sieve is crushed with a mixer and the maximum particle size is 1 m.
The powder under the sieve which has been sieved to m or less is placed in a molding die 1
00 g was weighed and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, heated with an electric heater on the top plate for 45 minutes until the mold temperature reached 185 ° C, and then water was passed to cool the top plate. Start and when the mold temperature reaches 170 ℃, operate the hydraulic pump to
Press molding was performed under a pressure of MPa for 5 minutes. The mold temperature was cooled to 120 ° C. in these 5 minutes. After that, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower. By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 1
A plate-shaped fuel cell separator having a thickness of 00 mm and a thickness of 5 mm was manufactured.

The obtained separator 10 has a bulk density of 2.
The variation coefficient of the bulk density was 06 g / cc and 0.006.
The maximum bending stress (bending strength) is 19.2 MPa, the maximum bending stress variation coefficient is 0.088, the maximum bending stress strain (breaking strain) is 1.63 mm, and the maximum bending stress strain variation coefficient is 0.058. there were. At this time, the volume specific resistance (volume resistivity) was 11.5 mΩ · cm, and the coefficient of variation of the volume specific resistance was 0.054. Furthermore, the breaking energy is 15.7M
Pa · mm, the coefficient of variation of fracture energy is 0.1
Met. Thus, the separator 10 obtained by raising the molding temperature to an appropriate molding temperature had a small variation.

Comparative Example 1 In Comparative Example 1, the same sample as in Example 1 was used.
The process up to the insertion of the mold is the same as that described in the first embodiment. The difference here is that the molding temperature is lower than in Example 1.
That is, the mold containing the powder was introduced into a pressure molding machine, and the mold temperature was 145 ° C. over 45 minutes with an electric heater on the top plate.
After heating to 0 ° C., water was passed to start cooling the top plate, and when the mold temperature reached 130 ° C., the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 5 minutes. The mold temperature was cooled to 96 ° C. in these 5 minutes. After that, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of maximum bending stress of 0.122 and a coefficient of variation of maximum bending stress strain of 0.103, showing large variations in mechanical strength. At this time, the coefficient of variation of the volume resistivity was 0.113 and the coefficient of variation of the fracture energy was 0.191, and the variations were large. As described above, when the molding temperature was lower than the appropriate temperature, the obtained fuel cell separator was not uniform.

Example 2 5 kg of natural graphite powder (average particle size: 13 μm) was put into a 20 liter vertical high-speed mixer, and while rotating a rotary blade, a solution of 250 g of SEBC dissolved in 1000 cc of toluene was added and mixed for 10 minutes. did. This mixture
After drying at 110 ° C. for 6 hours or more until the toluene odor disappeared, after sieving with a maximum particle size of 1 mm, the upper part of the sieve was crushed with a mixer and sieved so that the maximum particle size was 1 mm or less for all amounts. 100 g of the powder under the sieve was weighed in a molding die and filled so that the surface became flat. The mold containing this powder was introduced into the pressure molding machine, and the electric heater on the top plate
After heating the mold temperature to 175 ° C over 45 minutes, water is passed to start cooling the top plate, and the mold temperature is 160 ° C.
Then, the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 5 minutes. Mold temperature is 11 in 5 minutes
It had cooled to 3 ° C. Then stop the hydraulic pump,
The pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.006 and a coefficient of variation of maximum bending stress of 0.06.
077, the coefficient of variation of maximum bending stress strain was 0.067. The coefficient of variation of volume resistivity at this time is 0.075
Met. Furthermore, the coefficient of variation of the fracture energy is 0.09.
It was 6. In this way, the fuel cell separator obtained by extending the molding time with an appropriate molding time was uniform with little variation.

Example 2-2 This example is an example of optimization under other conditions.
Until the powder is charged into the molding die, the above-described Example 2 is used.
Is the same as the description above. In this Example 2-2, the pressure was released during the temperature cooling of the standard product. That is, the mold containing the powder was introduced into a pressure molding machine, heated with an electric heater for the top plate over 45 minutes until the mold temperature reached 175 ° C., and then water was passed through the top plate. When cooling started and the temperature of the mold reached 160 ° C., the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 3 minutes. The mold temperature was cooled to 135 ° C. in these 3 minutes. After that, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower. By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 100 mm and the thickness is 5 mm.
A mm plate-shaped fuel cell separator was manufactured.

The obtained separator 10 had a variation coefficient of bulk density of 0.006. The coefficient of variation of the maximum bending stress is 0.012, and the coefficient of variation of the maximum bending stress strain is 0.0.
It was 44. The coefficient of variation of volume resistivity at this time was 0.072. Furthermore, the coefficient of variation of the breaking energy was 0.052. As described above, the pressure may be released during cooling of the standard product, and the separator 10 obtained with a proper molding time by extending the molding time was uniform with little variation.

Example 2-3 This example is an example of optimization under the conditions different from those of Example 2-2. Until the powder, which is a mixture, is charged into the molding die, the description is the same as that of the second embodiment described above. Here, even if the molding time is short, uniformization was achieved by degassing. That is, the mold containing this powder was introduced into a pressure molding machine capable of vacuuming, and it was sealed, and high temperature oil was circulated so that the temperature of the top plate was 175 ° C. over 45 minutes. After heating until, the oil is circulated while lowering the temperature to start cooling the top plate, and when the mold temperature reaches 160 ° C., the vacuum pump is operated to make the atmosphere vacuum,
The hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 1 minute. In this 1 minute, the atmosphere became a vacuum state of 270 hPa and the mold temperature was cooled to 153 ° C. After that, the vacuum pump was stopped, the atmosphere was opened, and the hydraulic pump was stopped, and then the pressure was released. Then, after cooling until the mold temperature becomes 50 ° C. or less, the mold is taken out from the pressure molding machine and is removed from the mold, so that the vertical and horizontal lengths are each 1
A plate-shaped fuel cell separator having a thickness of 00 mm and a thickness of 5 mm was manufactured.

The obtained separator 10 had a bulk density variation coefficient of 0.006. The coefficient of variation of the maximum bending stress is 0.076, and the coefficient of variation of the maximum bending stress strain is 0.0.
It was 84. At this time, the coefficient of variation of the volume resistivity was 0.063. Furthermore, the coefficient of variation of the breaking energy was 0.11. In this way, even if the molding time is shortened, degassing can provide a uniform separator 10 with little variation.

Example 2-4 This example is an example of optimization under conditions different from those of Examples 2-2 and 2-3. Until the powder, which is a mixture, is charged into the molding die, the description is the same as that of the second embodiment described above. Here, the mold containing the powder was introduced into a pressure molding machine capable of vacuuming, and the mold was sealed, and high temperature oil was circulated so that the mold plate temperature reached 195 ° C over 45 minutes. Heated until. After that, the oil is circulated while lowering the temperature of the oil to start cooling the top plate, and when the temperature of the mold reaches 180 ° C., the vacuum pump is operated, the atmosphere is evacuated, and the hydraulic pump is operated to reach 98 MPa. Press molded for 1 minute under pressure. In this 1 minute, the atmosphere became a vacuum state of 270 hPa and the mold temperature was cooled to 169 ° C. After that, the vacuum pump was stopped, the atmosphere was opened, and the hydraulic pump was stopped, and then the pressure was released. Then the mold temperature is 5
After cooling to 0 ° C. or less, the mold is taken out from the pressure molding machine and is removed from the mold to obtain a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm. Manufactured.

The obtained separator 10 had a coefficient of variation of bulk density of 0.007. Also, the coefficient of variation of maximum bending stress is 0.031, and the coefficient of variation of maximum bending stress strain is 0.0
It was 48. The coefficient of variation of volume resistivity at this time was 0.05. Further, the coefficient of variation of the breaking energy was 0.047. Thus, even if the molding time was shortened, the separator 10 was degassed and molded at a high temperature, whereby the separator 10 having a small variation and uniformized could be obtained.

Comparative Example 2 With the same sample as in Example 2, the same procedure as described in Example 2 was performed until the mixture powder was charged into the molding die. In Example 2, the molding time was optimized, whereas in Comparative Example 2, the molding time was short.
That is, the mold containing the powder is introduced into the pressure molding machine, and the mold temperature is 175 ° C. for 45 minutes with the electric heater of the top plate.
After heating to 0 ° C., water was passed to start cooling the top plate. When the temperature of the mold reached 160 ° C., the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 1 minute. The mold temperature was cooled to 152 ° C. in this 1 minute. After that, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a high coefficient of variation in bulk density of 0.013 and had large variations. In addition, the coefficient of variation of the maximum bending stress was as high as 0.102, and the variation in mechanical properties was large. The coefficient of variation of the fracture energy at this time is 0.163.
There was a lot of variation. As described above, when the molding time was short, the variation was large and the uniformity could not be maintained.

Example 3 In this example, 5 kg of natural graphite powder (average particle size 13 μm), which is the same sample as in Example 1, was charged into a 20 liter vertical high-speed mixer, and SEBC was rotated while rotating a rotary blade.
A solution of 250 g dissolved in 1000 cc of toluene was added and mixed for 10 minutes. This mixture is heated at 110 ° C. for 6 hours.
After drying for more than an hour until the smell of toluene disappears, it is sieved with a maximum particle size of 1 mm, then the upper part of the sieve is crushed with a mixer and 100 g of the powder was weighed in a molding die and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 170 ° C over 45 minutes with the electric heater on the top plate, the hydraulic pump was operated to
Press molding was performed under a pressure of 8 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. Then, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was reduced to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. By removing the mold from the pressure molding machine and removing it from the mold, the vertical and horizontal lengths are each 100 mm.
Thus, a plate-shaped fuel cell separator having a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.002. The coefficient of variation of the maximum bending stress was 0.018, and the coefficient of variation of the maximum bending stress strain was 0.064. At this time, the coefficient of variation of volume resistivity was 0.021. Furthermore, the coefficient of variation of the breaking energy was 0.052. In this way, by filling the molding die with the powder so that the surface becomes flat and depressurizing at a temperature of Tg or lower, it is possible to obtain a uniform separator 10 with a small variation.

Comparative Example 3 With the same sample as in Example 3, the same procedure as described in Example 3 was performed until the mixture powder was charged into the molding die. In Comparative Example 3, the pressure was released at a high temperature of Tg or Tm or higher. That is, the mold containing the powder was introduced into the pressure molding machine, and when the mold temperature reached 170 ° C. over 45 minutes with the electric heater on the top plate, the hydraulic pump was operated to
Press molding was performed under a pressure of 8 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, and at the same time, the hydraulic pump was stopped, the pressure was rapidly depressurized to atmospheric pressure, and then the mold was cooled to 50 ° C. or lower. Remove the mold from the pressure molding machine,
By die-cutting, the vertical and horizontal lengths are each 100
A plate-shaped fuel cell separator having a thickness of 5 mm and a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a high coefficient of variation of the maximum bending stress of 0.181 and a coefficient of variation of the maximum bending stress strain of 0.229, and had a large variation in mechanical properties. . At this time, the coefficient of variation of the volume resistivity was as high as 0.176, and the coefficient of variation of the fracture energy was as high as 0.395, showing a large variation. As described above, when the pressure was rapidly released (depressurized) at a high temperature (Tg or higher), the variation was large and the uniformity could not be maintained.

Example 4 5 kg of natural graphite powder (average particle size: 13 μm) was put into a 20 liter vertical high-speed mixer, and while rotating a rotary blade, a solution of 250 g of SEBC dissolved in 1000 cc of toluene was added and mixed for 10 minutes. did. This mixture
After drying at 110 ° C. for 6 hours or more until the toluene odor disappeared, the powder was sieved with a maximum particle size of 1 mm, and the sieve was crushed with a mixer. Then, 100 g of powder under the sieve, which is sieved so that the maximum particle size is 1 mm or less in total, is weighed in a molding die, and the central portion of the surface becomes a dent with a corner and a third of the end. So filled. That is, in this example, there was a variation in the powder input. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 170 ° C for 40 minutes with the electric heater on the top plate, the hydraulic pump was operated to
Press molding was performed under a pressure of 8 MPa for 5 minutes. The mold temperature had risen to 210 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower.
By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 100 mm and the thickness is 5 m.
A m-shaped plate-shaped fuel cell separator was manufactured.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.002. The coefficient of variation of the maximum bending stress was 0.007, and the coefficient of variation of the maximum bending stress strain was 0.039. The coefficient of variation of volume resistivity at this time was 0.022. Furthermore, the coefficient of variation of fracture energy was 0.043. In this way, even if the method of inputting into the molding die is bad and the surface is uneven (even if there is unevenness), the temperature will be melted and the pressure will be dispersed by increasing the molding temperature. It is possible to obtain a uniform separator 10 having a small size.

Comparative Example 4 Here, the molding temperature is lower than in Example 4. That is, in Comparative Example 4, 5 kg of natural graphite powder (average particle size: 13 μm) was charged into a 20 liter vertical high-speed mixer, and 250 g of SEBC was mixed with 1000 ml of toluene while rotating the rotary blades.
The solution dissolved in cc was added and mixed for 1 minute. This mixture is dried at 110 ° C. for 6 hours or more until the toluene odor disappears, sieved with a maximum particle size of 1 mm, and then pulverized with a mixer on the sieve so that the maximum particle size is 1 mm or less in total. 100 g of the sieved powder was weighed into a molding die and filled so that the central portion of the surface was a corner and the recess was a third of the end. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 170 ° C over 45 minutes with the electric heater on the top plate, the hydraulic pump was operated to reach 98MP.
It was press molded for 5 minutes under the pressure of a. The mold temperature had risen to 190 ° C. in these 5 minutes. Then, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower.
By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 100 mm and the thickness is 5 m.
A m-shaped plate-shaped fuel cell separator was manufactured.

The obtained fuel cell separator had a high coefficient of variation in bulk density of 0.011. The coefficient of variation of the maximum bending stress strain was as high as 0.133. Furthermore,
The coefficient of variation of the breaking energy was as high as 0.142.
As described above, when the method of charging into the molding die was bad, the surface was uneven, and the molding temperature was low, the coefficient of variation was high and the variation was large with respect to the predetermined physical properties.

Example 5 This Example 5 differs from the above-mentioned Examples in the kind of binder. Here, natural graphite powder (average particle size 13 μm)
Put 500 g into a 2 liter double-arm kneader, add 100 cc of toluene while rotating the rotary blade, and then 5
Mix for minutes to wet the graphite powder. Then, a solution of 25 g of commercially available polystyrene (average molecular weight 200,000, Tg = 100 ° C., decomposition point = 395 ° C. (reference value)) in 50 cc of toluene was added, and the mixture was kneaded for 1 hour. The mixture is dried at 110 ° C. for 6 hours or more until the toluene odor disappears, sieved with a maximum particle size of 1 mm, and then pulverized with a mixer on the sieve so that the maximum particle size is 1 mm or less in total. 100 g of the sieved powder under the sieve was weighed into a molding die and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, and the electric heater on the top plate
When the mold temperature reached 170 ° C. over a period of time, the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. By removing the mold from the pressure molding machine and removing it from the mold, the vertical and horizontal lengths are each 100 mm.
Thus, a plate-shaped fuel cell separator having a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.006. The coefficient of variation of the maximum bending stress was 0.015, and the coefficient of variation of the maximum bending stress strain was 0.038. At this time, the coefficient of variation of volume resistivity was 0.042. Furthermore, the coefficient of variation of the breaking energy was 0.051. In this way, even if the type of resin changes, if wetting treatment, sufficient mixing, uniform injection into the mold, proper molding temperature, proper molding time, etc. are selected, that is, by carefully molding, there will be variations. Could be made smaller.

Example 6 This example 6 differs from Example 5 in the amount of resin. That is, here, natural graphite powder (average particle size 13 μ
m) 500 g was put into a 2-liter double-arm kneader, 100 cc of toluene was added while rotating the rotary blade, and then mixed for 5 minutes to wet the graphite powder. Then, commercially available polystyrene (average molecular weight 200,000, Tg = 100
℃, decomposition point = 395 ℃ (reference value) 50g, toluene 1
A solution dissolved in 00 cc was added, and the mixture was kneaded for 1 hour. The subsequent processing is the same as in the fifth embodiment.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.006. The coefficient of variation of the maximum bending stress was 0.038, and the coefficient of variation of the maximum bending stress strain was 0.059. At this time, the coefficient of variation of volume resistivity was 0.041. Furthermore, the coefficient of variation of fracture energy was 0.057. In this way, even if the type of resin and the amount of resin change, if wetting treatment, sufficient mixing, uniform injection into the mold, proper molding temperature, proper molding time, etc. are selected, that is, careful molding is performed. By doing so, the variation could be reduced.

Example 7 Example 7 shows an example in which the kinds of binders are different and the molding pressure is appropriate. Natural graphite powder (average particle size 1
(3 μm) 500 g was put into a 2 liter double-arm kneader, 100 cc of toluene was added while rotating the rotary blade, and then mixed for 5 minutes to wet the graphite powder. Then, commercially available polystyrene (average molecular weight 200,000, Tg = 1
A solution obtained by dissolving 50 g of a mixture of 00 ° C., decomposition point = 395 ° C. (reference value) and SEBC in a weight ratio of 3: 7 in 200 cc of toluene was added and kneaded for 1 hour. This mixture
After drying at 110 ° C for 6 hours or more until the toluene odor disappears, sieving with a maximum particle size of 1 mm, sieving on the sieve with a mixer, and sieving so that the maximum particle size is 1 mm or less 100 g of the lower powder was weighed in a molding die and filled so that the surface became flat. The mold containing this powder
It was introduced into a pressure molding machine, and when the mold temperature reached 170 ° C. in 45 minutes with an electric heater on the top plate, the hydraulic pump was operated to perform press molding under a pressure of 98 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.001. The coefficient of variation of the maximum bending stress was 0.015, and the coefficient of variation of the maximum bending stress strain was 0.052. The coefficient of variation of volume resistivity at this time was 0.02. Further, the coefficient of variation of the breaking energy was 0.065. In this way, even if the type of binder is changed, the variation can be reduced by increasing the molding pressure.

Example 7-2 This is an example in which the molding pressure was made lower than in Example 7 and preforming was performed. The process up to filling the powder into the molding die is the same as that described in Example 7. The mold containing this powder was introduced into a pressure molding machine, and the
Pre-molded at 8MP for 5 minutes. After that, when the mold temperature reached 170 ° C. over 45 minutes with the electric heater on the top plate, the hydraulic pump was operated and press molding was performed under a pressure of 49 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.003 and a coefficient of variation of maximum bending stress of 0.03.
01, the coefficient of variation of maximum bending stress strain was 0.074, and the coefficient of variation of volume resistivity was 0.041. Further, the coefficient of variation of the breaking energy was 0.0819. As described above, even if the molding pressure was low, the inter-particle distance could be reduced by preforming, and the variation could be reduced.

Example 7-3 This is an example in which the molding pressure and the molding temperature were lowered as compared with Example 7, while preforming was performed. The process up to filling the powder into the molding die is the same as that described in Example 7. The mold containing this powder was introduced into a pressure molding machine and pre-molded at room temperature for 98 MP for 5 minutes. Then, with the electric heater on the top plate, the mold temperature is 150 for 45 minutes.
When the temperature reached ℃, the hydraulic pump was operated and press molding was performed under a pressure of 49 MPa for 5 minutes. Mold temperature is 1 in 5 minutes
It had risen to 70 ° C. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.003 and a coefficient of variation in maximum bending stress of 0.003.
027, the coefficient of variation of the maximum bending stress strain was 0.024, and the coefficient of variation of the volume resistivity was 0.051. Furthermore, the coefficient of variation of fracture energy was 0.03. As described above, even if the molding pressure and the molding temperature are low, the inter-particle distance can be reduced and the variation can be reduced by preforming.

Example 7-4 This is an example in which the molding pressure and the molding temperature were further lowered as compared with Example 7-3, while preforming was performed. The process up to filling the powder into the molding die is the same as that described in Example 7. The powder-containing mold was introduced into a pressure molding machine and pre-molded at room temperature for 98 MP for 5 minutes. Then, with the electric heater on the top plate, the mold temperature is 1 for 45 minutes.
When the temperature reached 30 ° C., the hydraulic pump was operated and press molding was performed under a pressure of 69 MPa for 5 minutes. The mold temperature had risen to 150 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.006 and a coefficient of variation of maximum bending stress of 0.06.
032, the coefficient of variation of the maximum bending stress strain was 0.037, and the coefficient of variation of the volume resistivity was 0.09. Furthermore, the coefficient of variation of the breaking energy was 0.016. As described above, even if the molding pressure and the molding temperature were further lowered, the inter-particle distance was reduced by the pre-molding, and the variation could be reduced.

Comparative Example 7 Here, the molding pressure was made lower than in Example 7. It is the same as that described in Example 7 until the powder is filled in the molding die. The mold containing the powder was introduced into the pressure molding machine, and when the mold temperature reached 170 ° C over 45 minutes with the electric heater on the top plate, operate the hydraulic pump to 49MP.
It was press molded for 5 minutes under the pressure of a. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water is passed through the top plate to start cooling, the hydraulic pump is stopped, and the mold temperature is 50 ° C.
The pressure was reduced to atmospheric pressure while cooling until the temperature became below. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a large coefficient of variation in bulk density of 0.026 and had a large variation. As described above, when the molding pressure is low, the variation becomes large, and the uniformity cannot be maintained.

Comparative Example 7-2 Here, too, the molding pressure is made lower than in Example 7.
It is the same as that described in Example 7 until the powder is filled in the molding die. The mold containing the powder was introduced into the pressure molding machine, and when the mold temperature reached 170 ° C over 45 minutes with the electric heater on the top plate, the hydraulic pump was activated to 69
Press molding was performed under a pressure of MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water is passed through the top plate to start cooling, the hydraulic pump is stopped, and the mold temperature rises to 5
The pressure was reduced to atmospheric pressure while cooling to 0 ° C or lower. By taking out the mold from the pressure molding machine and removing the mold,
A plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm was produced.

The obtained fuel cell separator had a large coefficient of variation in bulk density of 0.032 and had a large variation. As described above, when the molding pressure is low, the variation becomes large, and the uniformity cannot be maintained.

Example 8 Here, ultrasonic waves were applied to a poorly soluble resin, sufficiently dissolved in a solvent with a stirrer, and mixed with natural graphite. First, 500 g of natural graphite powder (average particle size: 13 μm) was put into a 2 liter double-arm kneader, 100 cc of toluene was added while rotating a rotary blade, and then mixed for 5 minutes to wet the graphite powder. After that, commercially available polystyrene (average molecular weight 340,000, Tg = 100 ° C, decomposition point = 395 ° C (reference value))
A solution of 50 g sufficiently dissolved in 200 cc of toluene while ultrasonically applying a homogenizer with a stirrer was added and kneaded for 1 hour. This mixture is
After drying at ℃ for 6 hours or more until there is no smell of toluene, sieving with a maximum particle size of 1 mm, then sieving on the sieve with a mixer and sieving so that the maximum particle size is 1 mm or less 100 g of the lower powder was weighed in a molding die and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, and the electric heater on the top plate
When the mold temperature reached 170 ° C. over a period of time, the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 5 minutes. The mold temperature had risen to 190 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. By removing the mold from the pressure molding machine and removing it from the mold, the vertical and horizontal lengths are each 100 mm.
Thus, a plate-shaped fuel cell separator having a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.002 and a coefficient of variation of maximum bending stress of 0.002.
014, the coefficient of variation of the maximum bending stress strain was 0.056, and the coefficient of variation of the volume resistivity was 0.033. Furthermore, the coefficient of variation of the breaking energy was 0.062. As described above, by applying ultrasonic waves to the resin that is difficult to dissolve, sufficiently dissolving it in a solvent with a stirrer, and mixing it with natural graphite, the variation was reduced.

Comparative Example 8 Here, unlike Example 8, mixing was performed by hand mixing. That is, natural graphite powder (average particle size 13 μm) 500
100 g of toluene was added to a 2 liter twin-arm kneader while rotating the rotary blades, and then mixed for 5 minutes to wet the graphite powder. Then, commercially available polystyrene (average molecular weight 340,000, Tg = 100 ° C., decomposition point = 3
A solution prepared by dissolving 50 g of 95 ° C. (reference value) in 200 cc of toluene while manually stirring was added and kneaded for 1 hour.
The subsequent process is the same as that described in the eighth embodiment.

The obtained fuel cell separator had a coefficient of variation of maximum bending stress strain of 0.102 and a coefficient of variation of fracture energy of 0.131, which were high. As described above, if the resin that is difficult to dissolve is not sufficiently dissolved in the solvent and mixed with the natural graphite, the variation becomes large.

Example 9 300 g of natural graphite powder (average particle size 13 μm) and 30 g of polycarbonate resin (high heat resistance and high impact grade PM1220 of Mitsubishi Engineering Plastics Co., Ltd.) were put in a vinyl bag, premixed, and then a twin-screw extruder. So 290
Mixing was carried out by passing the mixture at 5 ° C. five times. This mixture has a maximum particle size of 1
After sieving with a mixer, the upper part of the sieve was pulverized with a mixer, and 100 g of the powder under the size of the sieve that had been sieved so that the total maximum particle size was 1 mm or less was weighed and filled. The mold containing this powder was introduced into the pressure molding machine, and the electric heater on the top plate
When the mold temperature reaches 240 ° C over 90 minutes,
The hydraulic pump was operated and press molding was performed under a pressure of 98 MPa for 5 minutes. The mold temperature had risen to 261 ° C. in these 5 minutes. Then, the hydraulic pump was stopped, cooling was started with steam at the same time, steam was switched to cooling with water at a temperature of 250 ° C., and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower. By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 1
A plate-shaped fuel cell separator having a thickness of 00 mm and a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.003 and a coefficient of variation in maximum bending stress of 0.03.
No. 022, the coefficient of variation of maximum bending stress strain was 0.025, and the coefficient of variation of fracture energy was 0.036. Thus, when the molding temperature was raised, the variation became smaller.

Example 9-2 500 g of natural graphite powder (average particle size: 13 μm) was put into a 2 liter twin-arm kneader, and T was rotated while rotating a rotary blade.
After adding 100 cc of HF (tetrahydrofuran), the mixture was mixed for 5 minutes to wet the graphite powder. Then, 50 g of the same polycarbonate resin as in Example 9 was added to THF.
A solution dissolved in 250 cc was added, and the mixture was kneaded for 1 hour.
This mixture is dried at 110 ° C. for 6 hours or more until the odor of THF disappears, sieved with a maximum particle size of 1 mm, and then crushed on a sieve with a mixer so that the maximum particle size is 1 mm or less in all. 100g of powder under the sieve
It was weighed and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 240 ° C. over 90 minutes with the electric heater on the top plate, the hydraulic pump was operated to maintain the pressure at 98 MPa. Press molded for 5 minutes. The mold temperature had risen to 251 ° C. in these 5 minutes. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.003 and a coefficient of variation of maximum bending stress of 0.003.
026, the coefficient of variation of maximum bending stress strain was 0.035, and the coefficient of variation of fracture energy was 0.06. As described above, when the resin was dissolved in the solvent and uniformly dispersed, the variation became small.

Example 9-3 Here, a wet treatment is applied. That is, natural graphite powder
(Average particle size 13 μm) 500 g was put into a 2 liter double-arm kneader, and while rotating the rotary blade, THF100c
After adding c, it was mixed for 5 minutes to wet the graphite powder.
Then, a solution prepared by dissolving 50 g of the same polycarbonate resin as in Example 9 in 250 cc of THF was added, and the mixture was kneaded for 1 hour. The mixture is dried at 110 ° C. for 6 hours or more until the odor of THF disappears, and the maximum particle size is 1 m.
After sieving with m, the upper part is crushed with a mixer and 100 g of the powder under the size which is sieved so that the maximum particle size is 1 mm or less is measured in a molding die to make the surface flat. So filled. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 260 ° C for 90 minutes with the electric heater on the top plate, the hydraulic pump was operated to reach 98MP.
It was press molded for 5 minutes under the pressure of a. The mold temperature had risen to 284 ° C. in these 5 minutes. After that, water is passed through the top plate to start cooling, the hydraulic pump is stopped, and the mold temperature is 50 ° C.
The pressure was reduced to atmospheric pressure while cooling until the temperature became below. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a bulk density variation coefficient of 0.002 and a maximum bending stress variation coefficient of 0.002.
01, the coefficient of variation of the maximum bending stress strain was 0.058, and the coefficient of variation of the fracture energy was 0.054. In this way, the resin can be dissolved in a solvent to be uniformly dispersed, and the molding temperature can be increased to reduce the variation.

Example 9-4 Here, fine powder is used as the resin. That is, 300 g of natural graphite powder (average particle size 13 μm) and 30 g of the same polycarbonate resin as in Example 9 (made into fine particles of 0.1 mm or less) were put in a vinyl bag, premixed, and then biaxially extruded. The mixture was processed through a machine at 290 ° C. for 5 times. After sieving this mixture with a maximum particle size of 1 mm, the upper part of the mixture was crushed with a mixer, and 100 g of powder under the size of the powder was screened so that the total maximum particle size was 1 mm or less in a molding die. Filled. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 240 ° C. over 90 minutes with the electric heater on the top plate, the hydraulic pump was activated.
Press molding was performed under a pressure of 8 MPa for 5 minutes. The mold temperature had risen to 261 ° C. in these 5 minutes. After that, stop the hydraulic pump and start cooling with steam at the same time.
The temperature was changed from steam to water-cooling, and the pressure was depressurized to atmospheric pressure while cooling the mold temperature to 50 ° C. or lower.
By removing the mold from the pressure molding machine and removing the mold, the vertical and horizontal lengths are each 100 mm and the thickness is 5 m.
A m-shaped plate-shaped fuel cell separator was manufactured.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.004 and a coefficient of variation of maximum bending stress of 0.004.
028, the coefficient of variation of maximum bending stress strain was 0.017, and the coefficient of variation of fracture energy was 0.037. In this way, by making the particle size of the resin finer and improving the dispersion,
Variations can be reduced.

Comparative Example 9 There is no wet treatment here. That is, 300 g of natural graphite powder (average particle size 13 μm) and 30 g of the same polycarbonate resin as in Example 9 were put in a vinyl bag, premixed, and then passed through a twin-screw extruder at 290 ° C. five times to perform a mixing treatment. did. After sieving this mixture with a maximum particle size of 1 mm,
The upper part of the sieve was crushed with a mixer, and 100 g of the powder under the sieve which had been sieved so that the total maximum particle size was 1 mm or less was weighed and filled in a molding die. The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 220 ° C. over 90 minutes with the electric heater on the top plate, the hydraulic pump was operated to reduce the pressure to 98 MPa. And press molded for 5 minutes. The mold temperature had risen to 240 ° C. in these 5 minutes. After that, the hydraulic pump was stopped, cooling with water was started at the same time, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of maximum bending stress of 0.184. Also, the coefficient of variation of the breaking energy was as high as 0.186. Thus, when the resin is poorly dispersed and the molding temperature is low, the variation becomes large.

Example 10 300 g of natural graphite powder (average particle size: 13 μm) and polyphenylene sulfide (PPS: crosslinked type, melt viscosity at 300 ° C .: 2000 poise, deflection temperature under load: about 270 ° C.) 3
0 g was put in a vinyl bag, pre-mixed, and then passed through a twin-screw extruder at 290 ° C. five times for mixing treatment. After sieving this mixture with a maximum particle size of 1 mm, the upper part of the mixture was crushed with a mixer, and 100 g of powder under the size of the powder was screened so that the total maximum particle size was 1 mm or less in a molding die. Filled.
The mold containing this powder was introduced into a pressure molding machine, and when the mold temperature reached 300 ° C. over 90 minutes with an electric heater on the top plate, steam was caused to flow and cooling was started. The mold temperature was 290 ° C. and the hydraulic pump was operated to perform press molding under a pressure of 98 MPa for 5 minutes. Mold temperature is 2 in 5 minutes
It had dropped to 70 ° C. After that, the hydraulic pump was stopped, and the steam was switched to water cooling at the same time, and the mold temperature was 5
The pressure was reduced to atmospheric pressure while cooling to 0 ° C or lower. By taking out the mold from the pressure molding machine and removing the mold,
A plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm was produced.

The obtained fuel cell separator had a coefficient of variation in bulk density of 0.008 and a coefficient of variation in maximum bending stress of 0.008.
041, the coefficient of variation of maximum bending stress strain was 0.036, the coefficient of variation of volume resistivity was 0.053, and the coefficient of variation of fracture energy was 0.053. In this way, the variation can be reduced by increasing the number of biaxial extrusions to about 5 and improving the dispersion of the resin.

Comparative Example 10 Compared to Example 10, the number of biaxial extrusions is smaller here. That is, 300 g of natural graphite powder (average particle size 13 μm)
And PPS (crosslinked type, melt viscosity at 300 ° C: 2000 po
30 g of ise) was put in a vinyl bag, pre-mixed, and then passed through a twin-screw extruder twice at 290 ° C. for mixing treatment. The description of the subsequent processing is the same as that of the tenth embodiment.

The obtained fuel cell separator had a large coefficient of variation in bulk density of 0.017, a coefficient of variation in maximum bending stress strain of 0.109, and a coefficient of variation in fracture energy of 0.17.
It was as large as 159. Thus, the number of biaxial extrusions was as short as about two times, and when the resin was poorly dispersed, the variation was large.

Example 11 Here, a thermosetting resin was used as the binder. That is,
500 g of natural graphite powder (average particle size 13 μm) and 1.75 g (7%) of hexamine, which is a curing agent, were put into a 2 liter double-arm kneader, mixed for 2 minutes while rotating a rotary blade, and then 100 cc of ethanol was added. Mix for 5 minutes to wet the graphite powder and hardener. After that, 25 g of a commercially available novolac-based phenol resin was added to toluene 25c.
The solution dissolved in c was added and kneaded for 1 hour. This mixture is dried at 110 ° C. for 6 hours or more until the smell of ethanol disappears, sieved with a maximum particle size of 1 mm, and then crushed with a mixer on the sieve so that the total maximum particle size is 1 mm or less. 100 g of the powder under the sieve was weighed in a molding die and filled so that the surface became flat. The mold containing this powder was introduced into a pressure molding machine, and the electric heater on the top plate
When the mold temperature reached 200 ° C over a period of time, the hydraulic pump was operated and press molding was performed under a pressure of 98 MPa until the mold temperature reached 250 ° C. After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. The metal mold was taken out from the pressure molding machine, and the mold was removed to manufacture a plate-shaped fuel cell separator having a vertical and horizontal length of 100 mm and a thickness of 5 mm.

The obtained fuel cell separator had a coefficient of variation of bulk density of 0.004 and a coefficient of variation of maximum bending stress of 0.004.
028, the coefficient of variation of the maximum bending stress strain was 0.008, the coefficient of variation of the volume resistivity was 0.056, and the coefficient of variation of the fracture energy was 0.031. As described above, when the amount of the phenol resin used is reduced, the amount of the volatile matter is reduced, the number of defects is small, and the variation is small.

Comparative Example 11 Here, the compounding ratio of the thermosetting resin as the binder is increased. That is, natural graphite powder (average particle size 13 μm) 500
g and 5.25 g (7%) of hexamine, which is a curing agent,
The mixture was placed in a liter double-arm kneader and mixed for 2 minutes while rotating the rotary blade, then 100 cc of ethanol was added and mixed for 5 minutes to wet the graphite powder and the curing agent. Then, 75g of commercially available novolac phenolic resin
Was dissolved in 75 cc of toluene, and the mixture was kneaded for 1 hour. This mixture was dried at 110 ° C. for 6 hours or more until the smell of ethanol disappeared, and then the maximum particle size was 1 mm.
After sieving with, the upper part of the sieve is crushed with a mixer, and 100 g of powder under the sieve is screened so that the maximum particle size is 1 mm or less, so that the surface becomes flat. Filled. The subsequent processing is the same as that described in the eleventh embodiment.

The obtained fuel cell separator had a coefficient of variation of maximum bending stress strain of 0.132 and a coefficient of variation of fracture energy of 0.122. As described above, when the amount of the phenol resin used is large, the amount of the volatile matter increases, the number of defects increases, and the variation becomes large.

Comparative Example 11-2 Also in this example, the compounding ratio of the thermosetting resin as the binder is increased. That is, natural graphite powder (average particle size 13 μm) 50
0 g and 5.25 g (7%) of hexamine, which is a curing agent, were put into a 2 liter double-arm kneader and mixed for 2 minutes while rotating a rotary blade, then 100 cc of ethanol was added and mixed for 5 minutes to obtain graphite powder and The curing agent was moistened. Then, 75g of commercially available novolac phenolic resin
Was dissolved in 75 cc of toluene, and the mixture was kneaded for 1 hour. This mixture is dried at 110 ° C. for 6 hours or more until the odor of ethanol disappears, sieved with a maximum particle size of 1 mm, and then crushed with a mixer on the sieve so that the maximum particle size is 1 mm or less in all. 100 g of the powder under the sieve was weighed in a molding die and filled so that the surface became flat. The mold containing this powder was introduced into the pressure molding machine,
With the electric heater on the top plate, the mold temperature is 20 for 60 minutes.
When the temperature reached 0 ° C, the hydraulic pump was operated and press molding was performed under a pressure of 69 MPa until the mold temperature reached 250 ° C.
After that, water was passed through the top plate to start cooling, the hydraulic pump was stopped, and the pressure was depressurized to atmospheric pressure while cooling until the mold temperature became 50 ° C. or lower. By removing the mold from the pressure molding machine and removing it from the mold, the vertical and horizontal lengths are each 100 mm.
Thus, a plate-shaped fuel cell separator having a thickness of 5 mm was manufactured.

The obtained fuel cell separator had a bulk density variation coefficient of 0.028 and a maximum bending stress variation coefficient of 0.02.
131, the coefficient of variation of the breaking energy was 0.189. As described above, when the amount of the phenol resin used was large, the amount of the volatile matter increased, the defects increased, and the variation became large.

The results of Examples 1 to 11 and Comparative Examples 1 to 11-2 are shown in Tables 1, 2 and 3.

[0149]

[Table 1]

[0150]

[Table 2]

[0151]

[Table 3]

[0152]

As described in detail above, according to the present invention,
It becomes possible to obtain a high-performance fuel cell separator in which deformation such as warpage, swelling, and cracking is suppressed by molding carbonaceous powder and a binder as components, which is extremely advantageous industrially.

[Brief description of drawings]

1A and 1B are views showing an example of a separator (fuel cell separator) molded according to the present embodiment.

[Explanation of symbols]

10 ... Separator, 11 ... Reaction gas flow channel groove

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuo Suzuki             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Within Mitsubishi Chemical Corporation F-term (reference) 5H026 AA02 AA06 BB01 BB02 BB08                       CC03 CX07 EE06 EE18 HH00                       HH01 HH03 HH05 HH06

Claims (12)

[Claims] 1. A molded body comprising a carbonaceous powder and a binder as components, wherein the coefficient of variation of bulk density is 0.01 or less, and the coefficient of variation of fracture energy is 0.12 or less. Fuel cell separator. 2. The fuel cell separator according to claim 1, wherein the coefficient of variation of the volume resistivity is 0.10 or less. 3. The fuel cell separator according to claim 1, wherein the coefficient of variation of the maximum bending stress is 0.10 or less. 4. The coefficient of variation of maximum bending stress strain is 0.10.
It is the following, It is any one of Claim 1 thru | or 3 characterized by the above-mentioned.
The fuel cell separator according to the item. 5. The fuel cell separator according to claim 1, wherein the carbonaceous powder is graphite powder. 6. The carbonaceous powder has an average particle size of 1 μm or more and 100 μm or less.
7. The fuel cell separator according to any one of 1. 7. The binder according to claim 1, wherein the binder is selected from the group consisting of thermosetting resins, thermoplastic resins, rubbers, and thermoplastic elastomers. The fuel cell separator according to the item. 8. The particle size of the binder is 0.5 to 1.2 times the particle size of the carbonaceous powder, and the particle size of the binder is 0.5 to 1.2 times the particle size of the carbonaceous powder. The fuel cell separator described. 9. The fuel cell according to claim 1, wherein the mixed raw material of the carbonaceous powder and the binder is heated and pressure-molded. Separator. 10. The fuel according to claim 1, wherein the molded body is formed in a plate shape, and a reaction gas flow channel groove is formed on a plate surface of the plate shape. Battery separator. 11. The molded body has a length and width of 50 to 50 each.
The fuel cell separator according to any one of claims 1 to 10, which is a plate-shaped body having a thickness of 1000 mm and a thickness of 0.5 to several tens of mm. 12. The fuel according to claim 1, wherein the carbonaceous powder and the binder are mixed and then pressure-molded under heating. Battery separator.