JPH0645446B2 - Method for producing high-purity graphite fine powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing high-purity fine graphite powder having an impurity content of 50 ppm or less.

[Conventional technology]

Fine graphite powder has been widely used for a long time as a lubricant, conductive filler, etc., but recently it has come to be applied to fields such as electronics and nuclear power, and the impurity content is 50 ppm.
The demand for the following fine graphite powder having high purity is increasing.

Conventionally, a method of pulverizing a graphite material and treating it with a high-temperature halogen gas has been adopted as a means for producing high-purity graphite fine powder to meet this requirement, and the following specific processes are known.

(1) A graphite material was placed in a deashing treatment furnace and subjected to a high-purification treatment (hereinafter referred to as “high-temperature halogen gas treatment”) in which chlorine-containing gas such as freon was heated while being fed into the furnace. After that, coarse pulverization is performed using a pulverizer such as a hammer crusher, and then fine pulverization is performed using an atomizer or the like.

(2) The graphite material is first roughly pulverized and finely pulverized by the same means as described above, and then filled in a graphite container and subjected to high temperature halogen gas treatment.

In these processes, "graphite material" means a particle size of 10
mm block material, "coarse crushing" means several mm to several 100μ
Grinding to a granule with a particle size of m, and "fine grinding"
Means to pulverize to an average particle size of 1 μm or less.

[Problems to be Solved by the Invention]

Among the above-mentioned conventional techniques, the process (1) can efficiently and inexpensively purify (impurity content 50 ppm or less) because the block-shaped graphite material can be treated with a high-temperature halogen gas as it is. There are advantages. However, there is a drawback that the target high-purity graphite powder cannot be obtained due to a contamination phenomenon due to wear of a hammer crusher or an atomizer in the subsequent coarse pulverization and fine pulverization steps.

Further, in the case of the process (2), the coarse pulverization and fine pulverization steps accompanied by contamination are performed in the preceding stage, so that high-purity graphite powder exceeding the target level can be obtained by the high temperature halogen gas treatment in the next step. However, the finely pulverized graphite powder is extremely bulky and difficult to handle, and there is a problem that the amount of filling into the graphite container becomes small during the high temperature halogen gas treatment.

The present invention has been made in order to solve these problems, and provides a method for efficiently producing high-purity graphite fine powder having an impurity content of 50 ppm or less.

[Means for Solving the Problems]

That is, the method for producing high-purity graphite fine powder according to the present invention,
In the method of converting graphite material into high-purity graphite fine powder by pulverization and high-temperature halogen gas treatment, the first step of coarsely pulverizing the graphite material to a particle size of several mm or less, the first step of high-purifying the coarse-pulverized material with high-temperature halogen gas The constitutional feature is composed of two steps, that is, a third step of adding ethanol to the coarsely pulverized product after the high-purification treatment and pulverizing by jet mill pulverization to an average particle size of 1 μm or less.

As the graphite material used as a raw material, a block material of artificial graphite obtained by a usual manufacturing method is used, but for example, a residual material or a processing waste of a graphitized product generated in the process of manufacturing a large graphite electrode for electric steelmaking. You may use the waste materials of. For coarse crushing of these graphite materials, use a conventional coarse crusher such as a hammer crusher, and use a particle size of several mm to several mm.
Grind to a size of 100 μm (first step).

The coarsely crushed material is filled in a container made of high-purity graphite material and set in a deashing furnace. While the halogen-containing gas such as chlorine or freon is fed into the furnace, it is heated to a temperature of about 2000 ° C. Purify (second step).

Then, ethanol is added to the coarsely pulverized product after the high-purification treatment, and finely pulverized into particles having an average particle diameter of 1 μm or less using a jet mill pulverizer (third step). There are two types of jet mill crushers, one of which makes the raw materials collide with each other by a jet stream, and the other of which the raw material is sprayed onto the collision plate by the jet stream. In the third step, a machine belonging to the former type is used. Is desirable.

[Work]

In the present invention, the material to be treated with the high-temperature halogen gas in the second step is a powder material obtained by coarsely crushing a graphite material and having a particle size of several millimeters to several hundreds of micrometers. The amount will also increase significantly. Therefore, it works effectively in order to improve the work efficiency of the purification treatment and the treatment efficiency.

In addition, since the subsequent pulverization in the third step is performed by jet mill pulverization by adding ethanol to the coarse pulverized product, the pulverization efficiency is improved, and the secondary contamination due to the inclusion of impurities from the pulverizer system is effective. Be prevented. For this reason, the target average particle size is 1 μm or less and the impurity content is 50 pp.
High-purity graphite fine powder of m or less is produced.

〔Example〕

200 kg of a granular material with a particle size of 8 mm or less obtained by coarsely crushing a graphite material is filled in a cylindrical crucible-shaped high-purity graphite container, set in an electric resistance heating type deashing furnace, and chlorine gas is circulated at a flow rate of 50 / min. Meanwhile, the temperature was raised to 2000 ° C at a temperature rising rate of 400 ° C / hour. After maintaining at this temperature for 10 hours to perform a purification treatment, it was naturally cooled.

The graphite powder after high-purification treatment is then jet mill crusher (jet crusher manufactured by Seishin Enterprise, STJ-2000).
Was used to perform fine pulverization treatment four times. At the time of crushing, ethanol (special grade reagent) was added to the graphite powder to be treated to improve the crushing efficiency by increasing the own weight.

The high-purity graphite fine powder thus obtained was analyzed by a particle size analyzer (manufactured by Seishin Enterprise, Micron Fort Sizer SK
C-2000S) and the average particle size was measured using ethanol as the dispersion medium. At the same time, the content of impurities was measured using a fluorescent X-ray analyzer (3370, manufactured by Rigaku Denki Co., Ltd.).

These measurement results are shown in Table 1 in comparison with the measurement results of commercially available high-purity graphite fine powder according to the prior art.

[Effects of the Invention] As described above, according to the present invention, high-purity graphite fine powder having an average particle size of 1 µm or less and an impurity content of 50 ppm or less can be efficiently manufactured at all times, and thus, it is possible to improve the efficiency in fields such as electronics and nuclear power. It can be safely supplied for any application requiring purity performance.

Claims (1)

[Claims] 1. A method of pulverizing a graphite material and converting it into high-purity graphite fine powder by high-temperature halogen gas treatment. High-purity graphite, comprising a second step of purifying treatment, and a third step of adding ethanol to the coarsely pulverized product after the high-purification treatment and pulverizing by jet mill pulverization to an average particle size of 1 μm or less. Method for producing fine powder.