JPS62171908A - Production of carbon plate - Google Patents

Abstract

PURPOSE:To make it possible to keep the fiber shape even after carbonization treatment and thereby sufficiently play a role in fiber reinforcement, by using infusibilized pitch fibers. CONSTITUTION:20-80wt% thermosetting resin, 10-70wt% graphite powder having <=50mu maximum particle size and 10-50wt% infusibilized pitch fibers are pressurized and molded into a plate form. The resultant plate is then completely cured within a temperature region of 150-200 deg.C and carbonized to afford the aimed carbon plate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a carbon plate, and this specification describes a method for stabilizing a carbon thin plate with excellent mechanical properties, which is preferably used for a phosphoric acid fuel cell separator. We propose a manufacturing method using

A phosphoric acid fuel cell has a unit cell consisting of an electrolyte layer holding phosphoric acid and a porous electrode substrate supporting a platinum catalyst disposed on both sides of the electrolyte layer, and each unit cell is stacked with a separator in between. Such a separator separates the fuel gas and oxidizing gas supplied to the gas distribution grooves on both sides of the separator.
Since it is necessary to function as a boundary and a connecting conductor between unit cells, the material has properties such as high gas impermeability, electrical conductivity, thermal conductivity, mechanical strength, and resistance to phosphoric acid at operating temperatures. This is required.

(Prior Art) Conventionally, as a manufacturing method for the above-mentioned battery separator, that is, carbon plate, phenolic resins, such as those disclosed in Japanese Patent Application Laid-open No. 59-26907 and Japanese Patent Application Laid-Open No. 59-127377, have been used. There is a method in which a thermosetting resin and graphite powder are kneaded, molded using a hot roll or hot press, and then carbonized if necessary. The carbon material produced by this known method has excellent gas impermeability and electrical conductivity. However, it had poor mechanical strength and was easily damaged during battery manufacture, leaving problems with workability.

In addition, there is a method proposed in Japanese Patent Application Laid-Open No. 57-207883. This known technique is a method of firing and carbonizing a molded article made of a thermosetting resin such as a phenolic resin, graphite powder, and carbon fiber. This method yields carbon plates for fuel cell separators that have excellent gas impermeability, electrical conductivity, and mechanical strength. However, since carbon fibers are used as reinforcing materials, the carbon fibers and matrix are bonded to each other during firing. Due to the difference in thermal contraction rate of the resins, cracks are likely to occur, and as mentioned above, it has been difficult to industrially and stably manufacture carbon plates.

Although they have excellent gas permeability and electrical conductivity, they have poor workability due to poor mechanical strength, and the use of fiber reinforcement hinders stable production, which is a problem faced by each of the above conventional technologies. However, these problems are regarded as problems to be solved, and the purpose of the present invention is to propose a method for overcoming them.

(Means for resolving the problems) The objectives listed in item 1 will be realized through a structure that has the following points as its main points. That is, the method for manufacturing a carbon plate according to the present invention includes 20 to 80% by weight of a thermosetting resin, 10 to 70% by weight of graphite powder with a maximum particle size of 50 μm or less, and 10 to 50% by weight of infusible pitch fibers. It is characterized in that it is pressurized and heated to be formed into a plate shape, completely cured in a temperature range of 150 to 200°C, and then carbonized.

(Function) First, the starting materials used in the production method of the present invention will be explained.

The thermosetting resin is preferably a phenol resin, but other resins such as furan resin, epoxy resin, unsaturated polyester resin, and polyimide resin can also be used. The reason why phenolic resin is preferable is that the resin is easy to handle, the molded product has properties, and the price is low. The blending amount of this thermosetting resin is 20 to 80% by weight. If it is less than 20% by weight, a uniform molded product cannot be obtained, and voids are generated inside the molded product, resulting in a decrease in gas impermeability. Moreover, when it exceeds 80% by weight, electrical conductivity decreases.

The graphite powder may be a natural product, an artificial product, or a mixture thereof. The maximum particle size of the powder used must be 50 μm or less. If more than 50 μM is used, the density will not increase and satisfactory gas impermeability and electrical conductivity cannot be obtained. In addition, the blending amount is 10~
70% by weight. If it is less than 10% by weight, electrical conductivity will be poor, while if it exceeds 70% by weight, gas impermeability and mechanical strength will decrease.

The infusible pitch fibers can be obtained by melting coal tar pitch or petroleum pitch at 250 to 400°C, spinning the fibers using a take-out spinning method or a centrifugal spinning method, and then treating the fibers in an oxidizing atmosphere. . Its blending amount is 10 to 50% by weight. This is because if it is less than 10% by weight, the effect of fiber reinforcement is low, and if it exceeds 50% by weight, gas impermeability will be reduced.

Next, a method for forming and carbonizing the above blended raw materials will be explained.

The method for manufacturing resin moldings is to process infusible pitch fibers into felt or cloth shapes using conventional methods, impregnate them in a graphite powder and phenol resin mixture, dry them, and then laminate them to the desired thickness. Then, it can be molded under pressure and heat using a roll or press, or it can be molded in the same way after uniformly mixing infusible pitch fibers, graphite powder, and phenolic resin powder cut to a certain length. A method of molding under pressure heating is used.

Next, the resin molded body produced in this way was
After being completely cured in a temperature range of 00°C, the desired carbon thin plate can be obtained by heating to about 1000°C and carbonizing it.

(Example) (1) Phenol resin (manufactured by Gunei Chemical Co., Ltd.: Regitop PL2211. Non-volatile content - 56%, viscosity - 100 cp
s), a felt material of infusible pitch fiber (100 g/n?) was impregnated into a methanol solution containing artificial graphite powder (pulverized with a pulverizer for 200 mesh baths) and dried at room temperature. The composition is shown in Table 1.

Two sheets of the impregnated material are laminated, sandwiched between flat molds, and heat pressed at a pressing temperature of 160°C and a pressing pressure of 70 kg/c.
Hot pressure molded with d, thickness 0.91m 3'0OX300I
It was molded into 11 thin plates.

Next, the molded body was left at 180°C for 10 hours to completely cure the phenolic resin, and then placed between graphite plates at 10°C/h.
Carbonization treatment was carried out by heating to 1000° C. at a heating rate of r.

Table 2 shows the properties of the obtained carbon thin plate. Furthermore, carbon F
Table 3 shows the proportion of defects such as regular cracks and cracks in the iQ board in comparison with Comparative Example 5.

(2) Phenol resin (manufactured by Gunei Kagaku Shishasha; Resitop P
After uniformly mixing G (A)-2400 fine powder, natural graphite powder (pulverized with a pulverizer at 200 meso-syuba), and 6 mm long infusible pitch fibers according to the composition shown in Table 1, the mixture was fed to a flat mold. Thereafter, the same treatment as in Example 1 was carried out to obtain the desired carbon thin plate.

Its characteristics are also shown in Table 2.

(Comparative Example 1) Blend composition 1. 'i As shown in Table 1, carbon thin plates for comparison were obtained by processing in the same manner as in Example (]) without the infusible pitch fibers. Its characteristics are shown in Table 2.

(Comparative Example 2) As shown in Table 1, a carbon thin plate for comparison was obtained by processing in the same manner as in Example (1), with an excess of phenol resin and an insufficient amount of infusible pinch fiber. Its characteristics are shown in Table 2.

(Comparative Example 3) As shown in Table 1, the blending composition is as shown in Table 1.
A carbon thin plate for comparison was obtained by processing in the same manner as in 2). Its characteristics are shown in Table 2.

(Comparative Example 4) As shown in Table 1, a comparative carbon thin plate was obtained by processing in the same manner as in Example (2) except that the blended composition was insufficient in phenol resin and infusible pitch fiber. Its characteristics are shown in Table 2.

(Comparative Example 5) The blending composition was that the infusible pitch fiber of Example (1) was mixed with PAN.
Example (1, 1,
) to obtain a carbon thin plate for comparison.

Table 3 shows the number of defective products.

As is clear from comparing the above examples and comparative examples, according to the present invention, the gas permeability is 10-5 mA/m1n-
cn! (NZ gas, 1 atm, room temperature) or less, a carbon thin plate that is stable in high temperature phosphoric acid with an electrical specific resistance of 5 mΩ or less and a bending strength of 1 kg/ram2 or more was industrially and stably produced.

Table 3 Number of defective products = Number of defective products with cracks, cracks, etc. when manufacturing 50 sheets of carbon thin plate of 30 squares.

(Effects of the Invention) As explained above, according to the present invention, since infusible pitch fibers are used, the shape of the fibers can be maintained even after carbonization, and therefore the role of fiber reinforcement can be sufficiently fulfilled. The mechanical strength, which is a drawback of conventional carbon thin plates manufactured using phenolic resin-graphite powder, is improved.

On the other hand, according to the present invention using this infusible pitch fiber, there is little difference in heat shrinkage rate from the phenolic resin of the matrix, so it is manufactured from the above-mentioned thermosetting resin such as phenolic resin, graphite powder, and carbon fiber. This eliminates the occurrence of warps and the like caused by distortion during firing, which are the drawbacks of conventional carbon thin plate manufacturing methods, and makes it possible to stably manufacture carbon plates.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the structure of a single cell of a phosphoric acid fuel cell. 1... Separator 1'... Separator 2
...Negative electrode 2'...Positive electrode 3...Electrolyte (phosphoric acid)

Claims (1)

[Claims] 1. Thermosetting resin 20-80% by weight, maximum particle size 50%
10 to 70% by weight of graphite powder of 10 to 70% by weight or less and 10 to 50% by weight of infusible pitch fibers are heated under pressure, formed into a plate shape, and completely cured in a temperature range of 150 to 200°C. A method for manufacturing a carbon plate, characterized by carbonization treatment.