JPS593495B2 - How to process graphite for charging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes graphite, particularly tetrafluoroethylene resin (
The present invention relates to a method for treating graphite used for filling TFE resin (hereinafter abbreviated as TFE resin).

Various fillers are added to TFE resin to improve its mechanical properties and other properties, one of which is graphite.

TFE resin filled with graphite improves the wear resistance of TFE resin molded products without significantly increasing the coefficient of friction, and at the same time, when used as a sliding material, it has the advantage of not damaging the mating material. . However, TFE resin filled with graphite has the disadvantage of being prone to minute cracks during the normal molding process. However, there is a known method of pre-treating with mineral acid, especially hydrofluoric acid. It is. (Unexamined Japanese Patent Publication No. 49-76793).
Although this method has solved the problem of cracks occurring in the molded product, it has been found that when the molded product is a film, it has the following problems. That is, in order to manufacture a TFE resin film, first a large block-shaped molded product is made by compression molding, and then this is cut into a film by peeling and cutting. The resulting film often has pinholes, and may also have cracks or scratches along the length of the film. It goes without saying that a film with scratches has no value as a product, but since the strength of the scratched area is low, the film tends to tear during use as a film.
Therefore, a film with such scratches has no commercial value. As a treatment method for refining carbon products such as graphite, hydrofluoric acid, nitric acid, hydrochloric acid, or two of these are used.
It is also known that immersion in a mixed acid containing more than
No. 9-24351, U.S. Patent No. '03501272)
However, the present inventors have found that even if graphite treated by these methods is used as a filler, the above-mentioned problem cannot be solved.

The present invention provides a 5TF that does not cause such problems.
This method was developed to provide graphite suitable for filling into E-resin, and is characterized by bringing graphite powder into contact with hydrogen fluoride gas.

The graphite used in the method of the invention may be either natural or man-made.

There is no particular limitation on the particle size, but since the finer the particle size, the better it is for filling, it is usually preferable to use a particle size of about 200 mesh or smaller. In order to bring hydrogen fluoride-15 gas into contact with such graphite powder, the powder is placed in a container resistant to corrosion against hydrogen fluoride, the inside of the container is evacuated, and hydrogen fluoride gas is sucked and sealed into the container. Alternatively, it may be sealed in a container in the form of hydrofluoric anhydride, gasified by heating, left in that state for a while, and then the gas in the container may be removed by means such as depressurization. Hydrogen fluoride gas may be passed through a container containing graphite powder. In any case, it is desirable to stir the graphite powder to enhance the contact effect. In the former, that is, one mode of batch type processing, hydrogen fluoride gas is sealed in a transport container containing graphite powder, and the product is transported in that state, so that the processing of the present invention is completed during transport. You can also do it. The temperature for such processing is generally room temperature, but dry heating can shorten the processing time. A processing time of at least 30 minutes is required. Care must be taken because if the heating temperature is too high, undesirable deterioration of the graphite may occur. As the material for the processing container, materials known as corrosion-resistant materials against hydrogen fluoride can be used, but in the case of processing at low temperatures, synthetic resins such as polyethylene may be used.

T filled with graphite powder treated in this way
Types of FE resins include molding grade polymers of tetrafluoroethylene and copolymers with polytetrafluoroethylene containing 2% by weight or less of ethylene monomer as a modifier.

The TFE resin is pulverized to about 5 to 100 μm in a conventional manner and mixed with the graphite powder after the above treatment. Example 10 parts by weight of natural graphite crushed to a particle size of 200 mesh or less was placed in a polyethylene-lined steel sealed container, and 0.2 parts by weight of hydrofluoric anhydride was added. It was held at the temperature and time indicated in the table.

After that, the gas in the container was removed, the treated graphite powder was taken out, and it was uniformly mixed with TFE resin powder with an average particle size of 50μ in the usual manner, and then graphite 2 was prepared.
A TFE resin powder containing 0% by weight was prepared. This blended powder was preformed at a pressure of 400 kg/Crl and then fired at 370° C. for 10 hours to produce a graphite-filled TFE resin block with a diameter of about 250 mm and a height of about 200 U.

This block was then peeled and cut to obtain a cut film with a thickness of 0.1 mm. The number of scratches in the length direction and the number of cracks in the length direction were counted for each 600 m length of the obtained cut film (referred to as tape judgment).
The results are also listed in Table 1. Trial numbers 1 to 3 are comparative examples, and trial numbers 4 to 7 are examples.
In the same table, trial number 1 is the same graphite powder as the example graphite powder, but without any treatment, and trial numbers 2 and 3 are graphite powders that were not subjected to any treatment. Alternatively, graphite powder was immersed in a 5% hydrofluoric acid aqueous solution, treated at the temperature and time specified in the same table, and then separated and dried at about 100°C.

Both the printing process and film cutting in the comparative example were the same as in the example. As is clear from Table 1,
In Examples 4 to 7, the number of scratches was significantly lower than in Comparative Example 1 in which no treatment was performed, and there was no crack compared to Comparative Examples 1 to 3.

Claims (1)

[Claims] 1. A method for treating graphite for filling with tetrafluoroethylene resin, which comprises bringing graphite powder into contact with hydrogen fluoride gas.