JP4830264B2 - Manufacturing method of fuel cell separator - Google Patents

Description

  The present invention relates to a method for manufacturing a fuel cell separator that is molded using a resin molding material containing graphite.

There are several types of fuel cells, such as a solid oxide fuel cell and a polymer electrolyte fuel cell (PEFC). Among them, the polymer electrolyte fuel cell is one of the fuel cells excellent in conductivity. As mentioned. As such a polymer electrolyte fuel cell separator, a thermosetting resin or a molded product made of a thermoplastic resin and graphitized carbon is used.
The separator constitutes a unit cell together with an electrode or the like, and is used by laminating the unit cell, and requires a groove and a through hole for isolating the gas (hydrogen / oxygen) while allowing the gas to flow in the laminated state. To do. As a method of forming such a through hole, a method of cutting after molding, or a method of simultaneously molding a through hole cutting portion can be considered. However, the former method has a high processing cost, and the latter method tends to generate burrs in the hole processing portion after the separation portion is cut off, resulting in poor molding productivity.
For this reason, the method of making the outer peripheral part of a separation part thin is conceivable so that the separation part for forming a through hole can be easily separated after molding. As a method therefor, in order to facilitate the separation of the separation part, a manufacturing method has been proposed in which a thin notch part is formed in which the thickness of the outer peripheral part of the formation part is 10 to 50% of the thickness of the separator member. (For example, refer to Patent Document 1).

However, in order to form such a thin-walled portion, when the material is flowed in a mold and molded, the fluidity is deteriorated in the thin-walled portion, and a molding defect may occur at the back of the flow.
JP 2002-134127 A

  The problem to be solved by the present invention is to provide a method of manufacturing a fuel cell separator that does not cause a molding defect even if there is a thin portion for separating a separation portion for forming a through hole.

As a result of earnestly examining the above problems, the present inventor has biased the thin portion for separating the through-hole forming portion of the separator member from the center of the plate thickness, or by lowering the protrusion portion of the lower mold, etc. The flowability of the material is improved, and the part where the flow of the material is too fast is made higher in the protrusions of the lower mold, and by adjusting the balance of the flowability of the material, a molded product free from molding defects can be obtained. As a result, the present invention has been completed.
That is, the present invention is a method for manufacturing a fuel cell separator, wherein a fuel cell separator material containing graphite and a resin is formed into a separator shape having a plurality of through holes, and the thin wall for forming the through holes the position in the thickness direction of the parts to bias more than 10 percent from the center of the thickness of the separator for a fuel cell, further characterized Rukoto varying amounts to bias the center of the thickness by the position of the thin portion in the longitudinal direction A method for producing a fuel cell separator is provided.
The present invention also provides the above-described fuel cell separator manufacturing method in which the position of the thin-walled portion in the thickness direction is changed between the inside and the outside of one separated portion.
Furthermore, the present invention provides the method for producing the fuel cell separator described above, wherein the thickness of the thin portion is changed depending on the thin portion in the longitudinal direction or the position of the thin portion.

According to the present invention, by forming the thin portion for forming the through hole of the separator member at a position in the thickness direction that is offset by 10% or more from the center of the plate thickness, a molded product that does not cause a molding defect is obtained. Can do.

The best mode for carrying out the present invention will be described in detail below.
A fuel cell separator is provided between adjacent unit cells in a fuel cell configured by stacking a plurality of unit cells, and forms a fuel gas channel and an oxidant gas channel between electrodes, and oxidizes fuel gas and oxidant. It has an effect of separating the gas, and a groove and a through hole for a gas flow path are formed.
The fuel cell separator manufacturing method of the present invention manufactures all or a main part of the fuel cell separator.
The separator for a fuel cell obtained by the present invention is formed of graphite powder and resin in a predetermined shape, and is preferably formed so that grooving is not required or only part of it is required. And, it is molded so as to be performed accurately.
In the fuel cell separator of the present invention, for example, graphite powder and resin are mixed in a weight ratio of preferably 95: 5 to 60:40, and the separator material is preformed to form a preform. It can be obtained by a method of manufacturing by press molding and curing.

The graphite of the fuel cell separator material used in the present invention is not limited as long as it exhibits high conductivity. For example, graphitized carbonaceous material such as mesocarbon microbeads, coal-based coke and petroleum-based materials. Examples include graphitized coke, special carbon materials such as graphite electrodes and isotropic graphite, natural graphite, quiche graphite, etc., and processed powders of graphite electrodes.
The resin of the fuel cell separator material used in the present invention is not particularly limited as long as it is heat-resistant and low-viscosity thermosetting resin or thermoplastic resin. Examples of the resin include resins such as phenol resin, furfuryl alcohol resin, epoxy resin, polyester resin, vinyl ester resin, urea resin, melamine resin, and polyphenylene sulfide resin. Of these resins, unsaturated polyester resins and vinyl ester resins are preferred. These resins are usually diluted with a monomer component such as a styrene monomer, further thickened using a thickener in some cases, and cured using a curing agent such as an organic peroxide. Among these, monomer components, thickeners and the like react with the resin, and thus become a resin component.

Examples of the fuel cell separator material include other additives such as a release agent.
A separator material containing graphite, a resin, an additive, and the like is kneaded and mixed, and then aged and thickened in some cases.
There is no particular limitation on the molding method of the material, but various press molding methods or injection molding methods using a mold are preferable. In this case, the mold temperature is preferably from 100 to 350 ° C, particularly preferably from 100 to 150 ° C. The mold temperature is preferably equal to or higher than the curing temperature of the thermosetting resin to be used and does not reach the carbonization temperature. Molding pressure is preferably ^{20~1000Kg / cm 2, 50~500Kg / cm} 2 is particularly preferred.

Next, the manufacturing method of the separator for fuel cells of this invention is demonstrated using figures.
The separator used in the production method of the present invention usually has 3 to 10 through-holes that can create the shape of a predetermined fuel cell separator. A metal mold | die has a separation part and thin part for forming these numbers of through-holes, and a through-hole can be formed by separating this separation part through a thin part.
Further, the present invention is characterized in that the position in the thickness direction of the thin portion for forming the through hole of the fuel cell separator is provided at a position deviated from the center of the thickness as shown in FIG. The position in the thickness direction of the thin-walled portion is preferably deviated by 10% or more from the center of the thickness because the material flow in the molded portion can be changed.
By changing the position in the thickness direction of the thin wall portion according to the position of the thin wall portion in the length direction, and biasing in the thickness direction, and changing the amount of bias, the material filling property to the periphery of the separator mold Is preferable in that it can be adjusted.
FIG. 5 is an example in which the bias direction and the bias ratio are changed depending on the position of the thin portion.

Further, as shown in FIG. 6, it is preferable to change the position of the thin portion in the thickness direction between the inner side and the outer side even in one cut-off portion because the material filling property can be improved.
Further, it is preferable that the thickness of the thin portion for forming the through hole is changed depending on the position of the thin portion or the thin portion in the length direction as shown in FIG. 7 in that the fluidity of the separator material can be adjusted. .
By forming the protruding portion of the mold corresponding to the thin portion of the separator in such a shape, it becomes easy to obtain a molded product in which no filling, voids, and pinholes are generated.

FIG. 1 shows a state in which a separator material is put in a mold and formed into a shape having a cut-off part for forming a through hole and a thin part by a press. It is formed by being sandwiched between 3 and heated and pressurized.
FIG. 2 shows a state in which the separator member molded from the mold is released, and the molds 2 and 3 and the molded separator member 8 are released. The molded separator member 8 is provided with a thin-walled portion 4 at a predetermined through-hole forming position by a projection 5 of the mold. In addition, the shape of the separation portion is not limited to the illustrated shape, and the entire separation portion may be a thin portion.

FIG. 3 shows a state in which a through hole is provided in the molded separator member. The separation part 6 is separated from the separated separator member 8, and the through hole 10 is formed. Since the thin-walled portion 4 is formed, the separation portion 6 can be separated by a simple punching process or the like, or by pressing it with a hand.
FIG. 4 is an example in which the position in the thickness direction of the thin portion for forming the through hole is biased from the center of the thickness. This improves the filling property of the separator material in the vicinity of the through hole. 1, FIG. 2 and FIG. 4 show a cross section of the through hole forming portion before the cut portion is cut off.

Further, FIG. 5 shows a cross section 8 of the separator member in the vicinity of the through hole forming portion of the separator 9 as viewed from the thickness direction and the center line 12 of the through hole forming portion. It shows that the position of the thin portion in the thickness direction of the separation portion is changed depending on the position of the separation portion.
FIG. 6 shows an example in which the degree of bias is changed depending on the position of the thin wall portion in one through hole forming portion, and FIG. 7 shows the position of the through hole forming portion with respect to the thickness of the thin wall portion for cutting the cut portion. Or it is the example changed according to the position of the thin part, and by this, the fluidity | liquidity of a separator material can be adjusted.

  The present invention will be described in detail based on the following examples.

Example 1
A total of 20 parts by weight of a vinyl ester resin, a curing agent, a thickener, and an additive were added to and mixed with 80 parts by weight of graphite powder. The mixture was aged for 24 hours at room temperature to increase the viscosity.
The obtained material is preformed into a square shape with a thickness of about 1 cm, and the upper and lower molds are formed so that the thickness direction position of the thin portion as shown in 2 and 3 of FIG. 2 is deviated from the thickness center. It put into the metal mold | die which formed the projection part, and it shape | molded for 5 minutes on the conditions of the mold temperature of 140 degreeC, and the pressure of 100 kg / cm < ² >, and demolded. The average thickness of the obtained separator excluding the recesses was 2.5 mm, and the thickness of the thin portion 4 was 0.2 mm.
In the mold, the position in the thickness direction of the thin portion is deviated from the center of the thickness, and one thin portion (thin portion A) is shifted downward by 0.3 mm (12% from the thickness center). The thin part (thin part B) is shifted 1.0 mm downward (40% from the center of thickness), and the other thin part (thin part C) is shifted 0.3 mm upward (12% from the center of thickness). It was.
According to a preliminary test, the vicinity of the thin portion A is slightly poor in filling, the vicinity of the thin portion B is inferior in filling property, and the portion near the thin portion C is filled with material first, and the balance of filling is lost. Therefore, a cut-off portion was provided at such a position. The obtained separator member has a surface structure as shown in FIG. 7, and in a molded product using a mold centered on the thickness direction of the thin portion tested in advance, it is not filled and voided. Defects such as pinholes occurred in the outer periphery of the molded product in the vicinity of the through-holes, but no defects occurred in the molded products of the examples.

Comparative Example 1
A total of 20 parts by weight of a vinyl ester resin, a curing agent, a thickener, and an additive were added to and mixed with 80 parts by weight of graphite powder. The mixture was aged for 24 hours at room temperature to increase the viscosity.
The resulting material is preformed into a square shape with a thickness of about 1 cm, and the position in the thickness direction of the thin portion for forming the through hole as shown in 2 and 3 of FIG. It put into the metal mold | die in which the protrusion part of the type | mold and the lower mold | type was formed, shape | molded for 5 minutes on the conditions of the mold temperature of 140 degreeC, and the pressure of 100 kg / cm < ² >, and demolded. The average thickness of the obtained separator excluding the concave portion was 2.5 mm, and the thickness of the thin portion 4 for forming the through hole was 0.2 mm.
The obtained separator member was found to have a portion where voids were generated and a portion where voids were not generated in the vicinity of the through holes, and the material flow was not balanced.

Schematic diagram showing the state in which the separator material is press-molded with a mold Schematic diagram showing the state where the molded separator member is released from the mold Schematic diagram showing a state in which the thin-walled portion is cut off from the molded separator member and a through hole is provided Schematic diagram showing that the position of the thin-walled portion for forming the through hole is biased from the center Schematic diagram showing that the position of the thin portion in the thickness direction is deviated from the center of the thickness by the position of the through hole forming portion in the length direction Schematic diagram when changing the position of the thin part in one through hole formation part Schematic diagram when the thickness of the thin portion in the thickness direction is changed depending on the position of the through hole forming portion in the length direction Plan view showing surface structure of separator member

Explanation of symbols

1 Separator material 2 Mold (upper mold)
3 Mold (lower mold)
4 Thin portion 5 Projection portion 6 of mold corresponding to thin portion of separator 6 Separation portion 7 Separator groove 8 Separator member 9 Through hole (when viewed from thickness direction)

Claims (3)

A fuel cell separator manufacturing method for molding a fuel cell separator material containing graphite and a resin into a separator shape having a plurality of through-holes, wherein a position in a thickness direction of a thin portion for forming the through-holes the biased than 10% from the center of the thickness of the separator for a fuel cell, further, the manufacture of the fuel cell separator, characterized in Rukoto varying amounts to bias the center of the thickness by the position of the thin portion in the longitudinal direction Method. Furthermore, the manufacturing method of the separator for fuel cells of Claim 1 which changes the position of the thickness direction of the said thin part between the inner side and the outer side of one separation part. The manufacturing method of the separator for fuel cells of Claim 1 or 2 which changes the thickness of the said thin part with the position of the thin part or thin part of a length direction.

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