JP2820492B2 - Carbon plate and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a carbon plate used for an electrode or the like of a fuel cell and a method for producing the same.

[Conventional technology]

A porous carbon electrode plate of a fuel cell is often manufactured by impregnating a carbon fiber sheet or a precursor fiber sheet thereof, a cellulosic fiber sheet such as paper, etc. with a thermosetting resin liquid, curing and firing.

The above sheet is generally obtained by a papermaking method having low productivity. However, since the sheet for a porous carbon plate needs to have a uniform in-plane and bulky surface, various ideas have been devised in the papermaking process. 62-12681, 60-122711, JP-A-1-298
91).

[Problems to be solved by the invention]

It is desired that the porous carbon plate for a fuel cell has high gas permeability in the direction perpendicular to the surface. However, a carbon plate having large pores has poor performance as an electrode and has a problem in strength. A carbon plate as a desirable electrode has many fine pores distributed in a direction perpendicular to the surface.

For example, a phosphoric acid fuel cell uses a concentrated phosphoric acid solution as an electrolyte, uses hydrogen and oxygen as fuel, and uses a chemical reaction using a platinum catalyst on a porous electrode carbon plate to reduce the energy involved in the reaction. We take it out as electricity. At this time, in order for hydrogen and oxygen as fuels to diffuse on the porous electrode carbon plate and react efficiently on the platinum catalyst, gas permeability in a direction perpendicular to the surface of the carbon plate needs to be excellent.

Various papermaking methods have been devised in the above-mentioned conventional method, but none satisfying the above requirements has been obtained.

An object of the present invention is to provide a carbon plate that has good gas permeability in the direction perpendicular to the surface of the carbon plate, has sufficient strength even if it is thin as an electrode plate, and is easy to manufacture.

[Means for solving the problem]

Since the fired carbon plate is brittle and hard, it is impossible to form many fine holes in the fired carbon plate by processing. Further, since the carbon plate as an electrode is quite thin, a porous one causes a problem in strength.

The inventor of the present invention reinforces the carbon plate by incorporating carbon fibers, and the cured body of the thermosetting resin can easily form fine holes, and even if this is fired, most of the holes remain. And have led to the present invention.

That is, the present invention is a carbon plate made of a carbon fiber and a carbide of a thermosetting resin, and has a large number of fine holes in a direction perpendicular to the surface of the carbon plate.

The method for producing the carbon plate is a method of impregnating a sheet of carbon fiber or a precursor thereof with a thermosetting resin liquid, curing the liquid, perforating a large number of fine holes in a direction perpendicular to the surface thereof, and firing the impregnated sheet. , Lamination pressing, curing, punching, firing, curing, lamination pressing, punching, firing, curing, punching, lamination pressing,
Firing method.

 Hereinafter, the present invention will be described in detail.

The carbon plate of the present invention is made of a carbon fiber and a carbide of a thermosetting resin, that is, the carbon fiber is dispersed in the carbide and is integrally bonded by the carbide.

This carbon fiber is not limited to carbon fiber already made from PAN-based or pitch-based, etc., and is treated as a precursor to infusibilize cellulose fibers such as paper or organic fibers such as PAN-based fibers. The resin may be carbonized at the same time as the resin is carbonized. The infusibilization treatment is possible even after resin impregnation.

As the thermosetting resin, a phenol resin, a furan resin, or the like is used, and these carbides are transmitted as so-called glassy carbon.

The carbon fiber content in the carbon plate is related to the strength, porosity, etc. of the carbon plate. Further, the porosity is affected by the firing conditions, for example, the rate of temperature rise, the presence or absence of pressure, and the like. Desirable values of the carbon fiber content also vary depending on these conditions, but generally 50 to 90% by weight is suitable.

The carbon plate has a large number of micropores in the direction perpendicular to its surface.
Pores are also generated when the thermosetting resin is carbonized, or when carbonized cellulose fiber or the like is used.

The micropores may not penetrate through the entire carbon plate because they may penetrate the carbon plate, or may be laminated after perforating each carbon plate in the laminated carbon plate as described in the manufacturing method described later. Is also included. Since the carbon plate has pores other than the fine holes, the carbon plate often communicates with other pores even if it is not the entire through-hole, and the effect of the present invention is not impaired.

It is desirable that a large number of micropores have a small diameter, but a too small diameter has a limitation in a manufacturing method. In practice, a range of 1.0 mm or less in hole diameter and 10 mm or less between holes is appropriate.

Other characteristic values of the carbon plate of the present invention include general ranges, including porosity including micropores of 50 to 80%, and compressive strength of 50 to 80%.
It is about 250 kg / cm ² .

The thickness of the carbon plate is usually about 0.4 to 2.0 mm for a fuel cell electrode.

 Next, the invention of the manufacturing method will be described.

First, carbon fiber or its precursor fiber (described above) is made into a sheet. For example, it can be obtained from a fiber and a papermaking binder by a papermaking method. In the case of cellulose fibers, paper can be used as it is.

This sheet is impregnated with a thermosetting resin liquid. The impregnation is performed by a method such as immersing the sheet in a resin solution. The amount of resin impregnation can be adjusted by the solid content concentration of the resin solution, the degree of pressure bonding after dipping and pulling the sheet in the resin solution, and the like. In order to make the content of the carbon fiber in the carbon plate 50-90% by weight, the carbon fiber 43-82% by weight, the remainder is impregnated resin (solid content), and the precursor fiber is 50-90% by weight, the remainder is 50-90% by weight. What is necessary is just to make it an impregnation resin. After impregnation, it is dried and cured according to a conventional method (the cured product is called a prepreg).

The prepreg is then perforated in the direction perpendicular to its surface, using a device similar to Kenzan for fresh flowers. The prepreg plate can be easily perforated unlike a fired carbon material.

The sintering is performed, for example, at a temperature of 800 ° C. or more according to an ordinary method by sandwiching a prepreg plate between graphite plates. If necessary, it can be graphitized.

In the present invention, when the sheet of carbon fiber or the like is thick, one sheet may be used, but it is preferable to adopt a laminated structure in order to make the resin impregnation uniform and to obtain a carbon plate for an electrode having good performance.
The method of lamination may be any of the above-mentioned. Lamination may be performed before or after curing, but all perforations are performed after curing.

[Action]

Drilling of the prepreg is easy, and since it is a thermosetting resin, even if the cured product is fired, the fine holes will not be blocked even if they are deformed. The fine holes pass through the plate in the vertical direction, but in the case of a laminated plate, if it is laminated after perforation, it does not become a through hole, but there are other pores in the carbon plate, so ventilation as a whole is perpendicular to the plate. And the performance as an electrode of a fuel cell is improved.

〔Example〕

Infusibilized polyacrylonitrile fiber of about 15 μm in thickness × about 3 mm in length (manufactured by Toho Rayon, trade name: Veslon) 70
Parts by weight and 30 parts by weight of a papermaking binder (trade name: Acrylic Binder A302, manufactured by Asahi Kasei Corporation) were converted into a 100 g / m ² sheet by a round mesh paper machine (TSS type sheet machine, manufactured by Toyo Seiki Seisaku-sho, Ltd.).

This sheet was impregnated with a phenol resin solution diluted to a concentration of 40% with ethanol, and dried and pre-cured at 100 ° C. for 7 minutes to obtain a prepreg having an impregnation amount of 40%.

The hole diameter of this prepreg is 0.7φm
m, was uniformly boring a hole about hole spacing 7 mm, and laminated 20 sheets, 20 minutes at 160 ° C., and thermocompression bonding at about 0.5 kg / cm ² condition,
The laminate was a 3 mm x 200 mm square laminate.

As a comparison, a prepreg without perforation was similarly used as a laminated plate.

The laminate thus obtained is sandwiched between graphite plates, treated at a temperature rising rate of 15 ° C./hr to 1000 ° C. by a conventional method, then heat-treated again in an Acheson furnace type graphitizing furnace, and 3,000 ° C. Graphitization was performed to obtain a porous carbon plate.

Table 1 shows the results of examining various physical properties of the porous carbon plate. As is clear from the results in Table 1, the porous carbon plate according to the present invention was found to have excellent gas permeability in the direction perpendicular to the plane.

[Effect] As can be seen from the results of the examples, the porous carbon plate obtained by the present invention has physical properties that can be sufficiently used as a porous electrode carbon plate for a phosphoric acid type fuel cell similarly to a conventional porous carbon plate. doing. Further, gas permeability in the direction perpendicular to the surface is superior to conventional products.

This feature is considered to contribute greatly to the performance improvement of the cell as a porous carbon plate for a phosphoric acid type fuel cell. Although it is optional, the method for producing a porous carbon plate according to the present invention is useful for improving the yield and productivity in the papermaking process, and is therefore useful for obtaining a stable and uniform product.

Claims (5)

(57) [Claims] 1. A carbon plate comprising a carbon fiber and a carbide of a thermosetting resin, the carbon plate having a large number of fine holes in a direction perpendicular to the surface of the plate. 2. A carbon sheet characterized in that a sheet of carbon fiber or a precursor thereof is impregnated with a thermosetting resin liquid, and after curing, a large number of fine holes are formed in the surface of the sheet in a vertical direction, and then fired. Manufacturing method. 3. A sheet of carbon fiber or a precursor thereof is impregnated with a thermosetting resin liquid, a plurality of the sheets are laminated and pressed, and after curing, a large number of fine holes are formed in a direction perpendicular to the surface of the laminated sheet.
Then, a method for producing a carbon plate, characterized by firing. 4. A sheet of carbon fiber or a precursor thereof is impregnated with a thermosetting resin liquid, and after curing, a plurality of the sheets are laminated and pressed to form a large number of fine holes in a direction perpendicular to the surface of the laminated sheet. And then calcining the carbon plate. 5. A sheet of carbon fiber or a precursor thereof is impregnated with a thermosetting resin liquid, and after curing, a large number of fine holes are drilled in a direction perpendicular to the surface of the sheet. Then, a method for producing a carbon plate, characterized by firing.