JP5024593B2 - FUEL CELL SEPARATOR MEMBER, MOLD FOR MOLDING, AND METHOD FOR PRODUCING FUEL CELL SEPARATOR - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a fuel cell separator member molded using a resin molding material containing graphite, a molding die, and a method for manufacturing a fuel cell separator.

There are several types of fuel cells, such as solid oxide fuel cells and polymer electrolyte fuel cells (PEFC). Among them, polymer electrolyte fuel cells are excellent separators for fuel cells. A molded product made of a resin and graphitized carbon is used.
The quality required for such a separator includes gas barrier properties, electrical conductivity, durability, dimensional accuracy, etc. In particular, the separator does not discharge components that affect the electrolyte membrane, which is the heart of the battery, and prevents its damage. Therefore, in order to prevent gas leakage, it is required that the plate thickness accuracy be smoothed in units of several tens of micrometers. Furthermore, cost reduction of the separator is required at the practical stage, and labor saving is indispensable in the processing process.

These separator members can be produced mainly by compression (press) molding or injection molding using a mold. However, when the graphite is mixed with the thermosetting resin to such an extent that the electroconductivity is good, the flow is reversed. In general, a compression (press) molding method or an injection compression molding method is performed because of poor performance.
These separators need to be provided with through holes as shown in FIG. 1 as flow paths for hydrogen, air, and generated water. However, if the resin molded product once produced as shown in FIG. 2 is drilled by machining, the productivity is low, which increases the cost.

Therefore, as a method of creating this through-hole, generally, a through-hole portion having a thin-walled portion is provided in a mold of a resin molded product, and the through-hole portion is separated and removed by cutting the thin-walled portion of the separator member once produced. The method of doing is mentioned.
Among them, in order to facilitate the separation of the through-hole portion, a method of forming a thin-wall portion in which the thickness of the outer peripheral thin-wall portion of the through-hole forming portion is 10 to 50% of the separator member thickness is formed (for example, a patent) In this proposal, as shown in FIG. 3, the thin portion for separation is in the horizontal direction with respect to the plate, and the position in the plate thickness direction is also the thickness of the plate. Is in range.

For this reason, when the removal portion 2 of the through hole is formed in the separator body 1 in the shape as shown in FIG. 3, if the removal portion 2 is removed by a punch or the like, the variability is within the thickness range of the through hole as shown in FIG. Will remain.
If such a burr exists, the burr may be detached during operation of the battery to block the flow path and reduce the battery performance. For this reason, when removing the through-hole, it is necessary to completely remove the burr. However, since the through-hole usually has a shape connecting R and a straight line, if there is a burr within the thickness range, It will take time and effort to remove along this shape.

Further, when the shape of the thin portion is as shown in FIG. 5, when the removed portion 2 is removed, the main body may be chipped as shown in FIG. In this case, a part of the molded product may collapse from the chipped portion and enter the fluid, damaging the electrolyte membrane and reducing the battery performance.
Further, as shown in FIG. 7, if the protrusion of the mold at the separating portion is made to be a blade-like protrusion, there is a drawback that the thin blade-like protrusion of the mold is easily damaged when the material is charged or when the molded product is removed.
Further, when the thin portion is provided in the horizontal direction within the plate thickness with respect to the plate as shown in FIGS. 3, 5, and 7, since the protrusion is provided on the mold, a portion having a small sectional area is locally generated. When a part with a small cross-sectional area occurs locally, when the material with poor fluidity such as graphite mixed is filled in the mold and molded at high pressure, the biting part opens slightly, and in the vicinity of the biting part A phenomenon that the thickness accuracy becomes several tens of μm occurs. If the plate thickness accuracy is locally deviated by several tens of micrometers, there is a risk of causing gas leakage or damage to the electrolyte membrane.
JP 2002-134127 A

  The problem to be solved by the present invention is a fuel that can easily and reliably carry out post-processing of a molded product after separation of the through-hole portion, does not weaken the mold structurally, and does not impair plate thickness accuracy. The manufacturing method of the separator member for batteries, and the metal mold | die for producing this separator member are provided.

As a result of intensive investigations on the above problems, the inventor found that the thin portion for separating the through hole of the separator member was at a position within the range of the plate thickness in the horizontal direction with respect to the plate as shown in FIG. By forming it so that it comes to the outer position of the plate thickness from one surface, even if burrs are generated due to separation of the thin part, the burrs are formed outward, so the horizontal plane is polished horizontally. It was found that it can be easily and reliably removed. Further, when a mold is filled with a material having poor fluidity such as graphite mixed, the material of the separation part 2 does not move in the horizontal direction even when the mold is closed as shown in FIG. It has been found that when the structure moves only in the vertical direction, a local increase in thickness around the cut-out portion is not observed.
And for this purpose, the present invention is completed by obtaining the knowledge that it is necessary to install a thin portion for forming the through hole at a position in the outward direction of the plate thickness from one surface of the separator member. It came.

That is, the present invention is a fuel cell separator member formed by molding a fuel cell separator material containing graphite and a resin, and having a thin portion for forming a through hole, wherein the thin portion is a separator member. A separator member for a fuel cell, characterized in that it is provided from one side of the plate toward the outer side of the plate thickness.
Moreover, this invention provides the metal mold | die for a mold used for the manufacturing method of the said separator member for fuel cells.
Furthermore, the present invention cuts the thin portion of the fuel cell separator member and cuts the through-hole portion to generate a burr in a convex shape from one surface of the separator member toward the outside of the plate thickness, The present invention provides a method for producing a separator for a fuel cell, characterized by performing deburring.

According to the present invention, since the burr by separating the through-hole portion is formed so as to protrude outward from the one side of the separator member, the burr can be removed by polishing the surface of the plate in the horizontal direction. Post-processing becomes very easy. When polished, the influence on the plate thickness remains within a few μm and there is almost no influence on the accuracy.
Furthermore, even when a material with poor fluidity is filled in the mold and molded, a significant increase in the plate thickness in the vicinity of the through hole is not observed, and a separator that can effectively exhibit battery performance can be obtained.

The best mode for carrying out the present invention will be described in detail below.
The fuel cell separator member of the present invention is formed by molding a fuel cell separator material containing graphite and a resin, and has a thin portion for forming a through hole.
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 separator material for a fuel cell used in the present invention is obtained by mixing graphite powder, a resin, an additive and the like by kneading.
The graphite powder used in the present invention is not limited as long as it exhibits high conductivity. For example, graphitized carbonaceous material such as mesocarbon microbeads, graphitized coal-based coke and petroleum-based coke. In addition, special carbon materials such as graphite electrodes and isotropic graphite, natural graphite, quiche graphite and the like are used, and processed powder of graphite electrodes and the like.
The resin used in the present invention is not particularly limited as long as it is a thermosetting resin or a thermoplastic resin that is heat resistant and has a viscosity that is low enough to be kneaded. For example, phenol resin, furfuryl alcohol resin, epoxy resin , Polyester resins, vinyl ester resins, urea resins, melamine resins, polyphenylene sulfide (PPS) resins, polyphenylene oxide (PPO) resins, and the like. Of these, unsaturated polyester resins and vinyl ester resins are preferred. These resins are 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.

The ratio of the graphite powder and the resin is, for example, blended and mixed so that the weight ratio is 95: 5 to 60:40.
The separator material may further contain an additive such as a release agent. Further, an external release agent can be applied in the mold without using such a release agent.

When the resin is a thermosetting resin, the mixture can be used after further thickening and aging. In this case, the separator material for a fuel cell is preformed (preformed), then press-molded and cured to produce a separator member.
Examples of the molding method of the separator material including graphite powder and resin include various press molding methods using a mold or an injection molding method.
When performing a press molding method or an injection molding method, for example, when a mixture of a thermosetting resin and graphite powder is heated and molded using a pressure type press molding machine or an injection molding machine, the mold temperature is 100 to 100. It is good to hold | maintain at 350 degreeC, Preferably about 100-150 degreeC. In this case, the temperature is set to be not less than the curing temperature of the thermosetting resin to be used and less than the carbonization temperature. The molding pressure is 2 to 100 MPa, preferably 5 to 50 MPa.

  When pressure-molding a thermoplastic resin, a mixture of resin and graphite is put into the mold, the mold is heated to 100 to 350 ° C., the resin is melted, and then the mold is added at 2 to 100 MPa. It is formed into a predetermined shape by cooling while pressing. When a thermoplastic resin is injection-molded, a material heated and melted at 100 to 350 ° C. with a screw is injected or injection-compressed into a mold, and then cooled with the mold to obtain a predetermined molded product.

The metal mold | die used for this invention can produce the separator member for fuel cells in a defined shape, and usually has 3-10 through-hole parts.
As a mold for providing a through-hole separating portion and a thin-walled portion in the fuel cell separator member in the outward direction of the plate thickness from one surface of the separator member, for example, upper and lower portions provided with uneven shapes as shown in FIG. Examples include molds.
In this case, it is preferable that the position of the thin wall portion is not completely in the vertical direction of the plate thickness, but is inclined to the center of the through hole by the draft angle of the mold. The draft angle of the mold is preferably 0.5 to 15 ° in terms of demoldability and product appearance.
Furthermore, the thickness of the thin wall portion 3 for cutting off the through-hole shown in FIG. 10 is preferably 0.01 to 0.3 mm, and further 0.05 to 0.15 mm in terms of ease of polishing. This is good. Moreover, R may be attached to the corner 4 portion of the convex portion of the mold, and the range is not particularly specified, but the range of 0.05 to 0.3 is preferable.

  Using this mold, the material previously formed in the shape of a lump or sheet is filled into the center or the entire surface of the mold, molded under the above-mentioned pressure and heating conditions, and removed from the mold, the through hole portion and the thin wall portion A separator member for a fuel cell provided in the outward direction of the plate thickness from one surface of the separator member can be obtained.

  The separator member for a fuel cell obtained by using the separator material is usually formed into a predetermined shape, and preferably formed so that the groove processing is unnecessary or only partially required, and the drilling processing is simple. , Which is shaped to be done accurately.

In the fuel cell separator member of the present invention, a thin portion for forming the through hole is provided from one surface of the separator member toward the outer side of the plate thickness.
As the shape in which the thin portion is provided from one surface toward the outside of the plate thickness, for example, a cut-out portion is preferably provided in the outward direction of the plate thickness as shown in FIG. In terms of processing, a shape in which only a thin portion for separation is provided outside the plate thickness as shown in FIG. In addition, as shown in FIG. 14, the thin part can be easily removed as a result of the method in which the thin part is tilted in a slanting direction because the abrasive is slightly bent in the hole. Further, as shown in FIG. 15, it is also effective to make the draft on the upper mold side intentionally so that the separation part can be taken by the upper mold at the time of demolding and to remove the separation part at the same time as the demolding. In this case, the separation part remaining in the upper mold has a larger linear expansion coefficient than that of the mold, so that it can be easily removed by contracting by blowing air.

In the present invention, the thin portion of the fuel cell separator member is cut and the through-hole portion is cut to generate a burr in a convex shape from one surface of the separator member in the outward direction of the plate thickness. It is to take.
The thin portion of the through hole can be easily cut by using air blow, a human finger or a punch. Due to the cutting of the thin portion, burrs generated in a convex shape remain outside the plate thickness range in the through hole.
Such burrs can be easily removed by applying the surface of the plate horizontally with an abrasive or the like, or by passing the plate through a roll of polishing cloth such as Scotch Bright. Examples of the abrasive include abrasive cloth [for example, Scotch Bright (registered trademark)] and sandpaper.

Example 1
Hereinafter, the present invention will be described in detail based on examples of the present invention.
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 at room temperature for 24 hours to increase the viscosity.
The resulting material was preformed in a square shape of about 1cm thick, put into a mold 5 and 6 as shown in FIG. 11, mold temperature 140 ° C., the mold in the vertical direction under a pressure of 100 kg / cm ² pressure The molded product was pressed for 5 minutes and demolded. The through hole portion of this mold is shown in FIG. The thickness of the thin wall portion of the through hole of this mold is 0.1 mm, and the draft is 5 °.
This molded product was already in a state where the cut-off portion was removed at the time of demolding. Moreover, since the protrusion of the burr | flash part remained around the through-hole, the horizontal surface was polished with Scotch Bright (registered trademark) to remove the burr. A little processing could be done.

Example 2
Under the same conditions as in Example 1, the thickness of the thin portion of the through hole of the mold was 0.01 mm, and the draft was 0.5 °.
Since this molded product was already separated at the time of demolding, and the protrusions on the burr portion were very slight, no post-processing was necessary.

Example 3
Under the same conditions as in Example 1, the thickness of the thin portion of the through hole of the mold was 0.3 mm, and the draft was 15 °.
When the cut-off part in the penetration direction of this molded product was removed, burrs remained. Therefore, sandpaper was applied in the horizontal direction to remove burrs. We were able to finish processing with little effort.

Schematic diagram showing the shape of the separator and through hole Schematic diagram for machining through holes Schematic diagram showing the structure of a conventional through-hole thin part The schematic diagram which shows the case where a cutting part is removed by the structure of FIG. Schematic diagram showing the structure of a conventional through-hole cutting part with another shape Schematic diagram showing the case where the cut-off portion is removed in the structure of FIG. Schematic diagram showing the structure of a conventional through-hole cutting part with another shape The schematic diagram which shows the structure of the cutting-off part of the through-hole of this invention The schematic diagram which shows the removal method of the burr | flash when the thin part burr | flash for separation in this invention remains The schematic diagram which shows the cutting-off structure of the through-hole of this invention Schematic diagram showing the shape of the mold used in the present invention The schematic diagram which shows the cutting-off structure of the through-hole of the Example of this invention The schematic diagram which shows the example of the separation structure of the through-hole of this invention The schematic diagram which shows the example of the separation structure of the through-hole of this invention The schematic diagram which shows the example of the separation structure of the through-hole of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator main body 2 Cut-off part 3 of through-hole 3 Thin-wall part 4 for cutting 4 Corner part of mold convex part 5 Upper mold 6 Lower mold 7 Processing tool 8 Abrasive material

Claims (5)

A fuel cell separator member formed by molding a fuel cell separator material containing graphite and a resin, and having a thin wall portion for forming a through hole, the thin wall portion being a plate from one surface of the separator member A separator member for a fuel cell, characterized by being provided toward the outer side of the thickness. The fuel cell separator member according to claim 1, wherein a gradient of the thin portion of the separator member is 0.5 to 15 °. The fuel cell separator member according to claim 1 or 2, wherein a thickness of the thin portion of the separator member is 0.01 to 0.3 mm. The molding die used when manufacturing the separator member for fuel cells of any one of Claims 1-3. The thin burr | flash part of the separator member for fuel cells of any one of Claims 1-3 is cut | disconnected, and a burr | flash is protruded toward the outer direction of plate | board thickness from one surface of a separator member by cut | disconnecting a through-hole part. A method for producing a separator for a fuel cell, characterized in that the deburring is performed and then deburring is performed.

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