JPS6067A - Manufacture of sealing material for layer-built cell - Google Patents

Abstract

PURPOSE:To obtain a sealing material of layer-built cell which does not result in leak of reaction gas and electrolyte and least expansion or contraction for the heat by giving heat treatment to a sheet obtained by kneading fine particles of graphite fluoride to the fluoric resin powder. CONSTITUTION:Fine powder of graphite fluoride (CF)n with bulk density of about 0.65 is mixed in about 5-60% to the fluoric resin powder of bulk density of about 0.3-0.8, these are kneaded with addition of solvent, then it is formed as a sheet. The sheet is then dried by removing solvent and is then subjected to heat treatment at a temperature of 180-200 deg.C. It is then cut into the desired size to form the sealing materials for layer-built cell. Since this sealing material has sufficient strength and is flexible sealing characteristic of stacked surfaces of layer- built cell can be improved, and leak of reaction gas and electrolyte can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a sealing material used for a laminated sealing surface of a fuel cell.

(b) Prior art matrix fuel cells are constructed by stacking a large number of unit cells (1) and carbonaceous gas separation plates (2) alternately into a cell stack (
S) Chickens are grown. In this case, on both side sealing surfaces (3) and (4) of each gas separation plate (2), one gas electrode and (N) are clamped.

Conventional sealing materials - known as ``shims'' - used injection molded hard fluororesin sheets, but they lacked elasticity and flexibility, resulting in poor sealing properties and were easily formed on reactant gases and sealing surfaces. The electrolytic solution in the liquid storage groove leaks to the outside, and in particular, due to the expansion and contraction of the fluororesin sheet due to thermal cycles, gaps are created on the sealing surface, which further promotes the leakage.

For this reason, silicon carbide (S i C
) A method of improving elasticity and flexibility by mixing powders has also been proposed, but in this case, SIC powder has a high specific gravity (true specific gravity 3.2, bulk specific gravity 067-1.3), so it is difficult to mix it with fluororesin. The resulting sheet had poor strength and insufficient elasticity.

(c) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned reaction gas leakage and electrolyte leakage.
An object of the present invention is to provide a sealing material that expands and contracts less in response to heat.

B) Structure of the Invention The sealing material of the present invention is obtained by kneading fluorinated graphite powder into a fluororesin, forming a sheet, and then heat-treating the mixture.

(e) Examples A method for producing the sealing material of the present invention will be explained.

Heptadonated graphite KFi, molecular formula (CF)n and (C2')n
There are two types, both of which are scale-like fine powder compounds.

In the present invention, Csn, which has a smaller bulk specific gravity and smaller average particle size than (C2')n, was used.

(cq.) is a white scale-like fine powder (average particle size 10 μm), light with a true specific gravity of 2854 and a bulk specific gravity of 0.65, has a decomposition temperature of 370° C., and has excellent insulation and phosphoric acid resistance.

The bulk specific gravity of normal fluororesin fine powder is 0.3 to 0.8,
(CF) Since it is close to that of n, it is easy to mix it with fluorinated graphite. In addition, (CF')n has good compatibility with fluororesins, so it is suitable as a filler for fluororesins.
A sealing material with excellent elasticity and strength and low thermal expansion and contraction can be obtained.

Add 80 g of polytetrafluoroethylene (FT'FFI) resin powder (20 g of carbon fine powder) to the rod, and mix these with 500 mt of kerosene as a dispersion solvent in a mixer. Filter this mixture to After removing 80 pieces, the PTF pH is clarified by rolling repeatedly with a roller kept at 40°C.During this process, the roller interval is gradually decreased and each time the folded sheet is passed through several times. Finally, it is rolled into a sheet of desired thickness using rollers.

The sheet is then dried at 80° C. to completely remove kerosene, then heat treated at 200° C. for 20 minutes, and then cut into desired dimensions to form a sealing material (shim).

The appropriate mixing ratio of ('')n to PTF'E is in the range of 5 to 60%.If the mixing ratio is higher than this range, the flexibility will increase but the strength will decrease.On the other hand, if the mixing ratio is lower than this range, the strength will decrease. However, there are problems such as a lack of flexibility and elasticity and increased expansion and contraction due to heat.Particularly preferred is a range of 10 to 40.

(f) Effects of the Invention The sealing material of the present invention has better elasticity than conventional fluororesin sheets, and particularly has less expansion and contraction due to heat. Also, compared to a sheet made of SiC bound with fluororesin, fluorinated graphite C (C
Because it is compatible with fluororesin, it is strong and highly flexible. Therefore, the sealing performance of the battery stack stacking surface is significantly improved, and reaction gas leakage and electrolyte leakage can be prevented.

[Brief explanation of drawings]

The drawing shows a laminated battery (battery stack) that is the object of the present invention.
It is a 4-hirodogi slope view of the main part.

Claims (1)

[Claims] ■ Fluororesin powder and fluorinated graphite C (CF'). ] The mixture with the fine powder is heated and kneaded, the mixed material is made into a sheet, the solvent is removed, and the mixture is heated to a temperature of 180 to 200 ml.
A method for producing a laminated battery sealing material characterized by heat treatment at ℃. (2) The method for manufacturing a laminated battery sealing material according to claim 1, wherein the mixing ratio of the fluorinated graphite is in the range of 5 to 60%.