JPH0214877A - Production of carbon material - Google Patents

Abstract

PURPOSE:To obtain a carbon material dense and having excellent mechanical strength without deterioration of operation environment by crushing aqueous slurry comprising raw carbon powder and water-soluble resin with water-jet crusher, molding, drying and baking. CONSTITUTION:Raw carbon powder, e.g., pitch coke powder, smoke black, artificial or natural graphite power is mixed with water-soluble resin, preferably thermoset, water-soluble phenol resin and water, or further additive such as dispersing agent, release agent, deflocculant or wetting agent is added to obtain slurry. Said slurry is crushed with a water-jet crusher making average diameter of aggregate in the slurry smaller than 15mum. Resultant powder is molded by, for instance, injecting into porous plaster mold, dried, cured and baked under inert atmosphere to obtain carbon material such as crucible or electrode material. Besides, according to use and environment used, further graphitization is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a dense carbon material used for crucibles, electric discharge machining electrode material 2 machine parts, and the like.

(Conventional technology) Up until now, carbon materials have been produced by pulverizing raw material powder, blending it with a binder such as tar pitch, heating and kneading it (hereinafter referred to as kneading), and then pulverizing and kneading it into powder (hereinafter referred to as kneading). ) was obtained by molding and firing the binder powder using a hydraulic press or the like, or by further graphitizing it.

(Problems to be Solved by the Invention) However, as shown in Japanese Unexamined Patent Publication No. 51-30212, when fine aggregates having an average particle size of 15 μm or less are kneaded with a binder such as tar pitch.

It becomes difficult to judge the end point of kneading. As a result, the volatile content in the kneaded powder fluctuates, causing cracks and deformation after firing.

This caused problems such as blistering.

In addition, in order to obtain a dense carbon material structure, the aggregate particle size was adjusted to 5 μm.
When pulverizing to a size of less than m, the temperature of the aggregate increases during pulverization, oxidizing the surface of the aggregate, which causes a problem of deteriorating the physical properties of the resulting carbon material. Furthermore, if we review the kneading process from a health and hygiene perspective, the end point of kneading must be judged in a state where vapor from tar pitch in the carrier material is generated, which is not a desirable working environment. .

The purpose of the present invention is to solve these problems and provide a carbon material with good physical properties, without fluctuations in volatile content in kneaded powder, without cracking, deformation, or blistering after firing. It is.

(Means for Solving the Problems) As a result of repeated research on the manufacturing method of carbon materials, the present inventors omitted the kneading step and added a water-soluble resin and water to the carbon raw material powder to form a slurry, which was then mixed with water. It has been found that a carbon material with good physical properties can be obtained by pulverizing the aggregate in the slurry to an average particle size of 15 μm or less using a jet pulverizer, casting, drying, and further firing or graphitizing.

In the present invention, carbon raw material powder, a water-soluble resin, water, or further additives are added to form a slurry, and the slurry is processed by a water jet pulverizer to reduce the average particle size of the aggregate in the slurry to 15%.
The present invention relates to a method for producing a carbon material, which is characterized by pulverizing the material to micrometers or less, casting and then drying and firing or graphitizing the material.

The carbon raw material powder referred to herein includes, for example, pitch coke powder, oil-smoked artificial graphite powder, natural graphite powder, expanded graphite powder, etc., and these may be used alone or in combination of two or more types. There are no particular restrictions on water-soluble resins, but from the viewpoint of dimensional accuracy of the product.

Thermosetting water-soluble phenolic resins are preferred. Additives include dispersants, mold release agents, peptizers, wetting agents and inorganic additives. The dispersant is used to uniformly disperse the solid carbon raw material powder into the slurry.

There are various types of surfactants, including ionic and nonionic surfactants, but they are not specific. Mold release agents are used to extract molded objects from cast plaster molds without damaging them, and stearic acid, zinc stearate, calcium stearate, stearamide, etc. are known, but they are not specific. Peptizers and wetting agents are used to control the structure of the forming layer formed on the surface of the plaster mold used in casting molding, and to reduce the resistance of water flow to the plaster mold.

In other words, in the cast molding process, the particles are first pressed against the wall surface by the water flow caused by the water absorption of the plaster mold, forming a molding layer, so the greater the resistance due to the water absorption of the plaster, the stronger the molding layer is pressed against the mold surface. Build a meat layer. However, when the ink layer is packed tightly, the resistance to the water flow sucked into the mold increases, making it difficult for particles to move to the mold surface, and the ink layer does not grow. Therefore, peptizers and wetting agents are added. Examples of peptizers include polycarboxylic acid ammonium salts, but they are not specified. Inorganic additives are added depending on the purpose, and include silicon carbide, alumina, mica, etc., but are not specified. As additives, one or more of these dispersants, mold release agents, peptizers, wetting agents, and inorganic additives may be added depending on the purpose.

Water is added to these carbon raw material powders, water-soluble resins, or additives shown above to form a slurry. This slurry is processed using a water jet pulverizer to reduce the average particle size of aggregate to 1
Grind to 5 μm or less. The reason why the aggregate in the slurry is crushed by a water jet crusher is to prevent oxidation of the surface of the aggregate and to coat the newly generated surface of the aggregate with resin well. The surface produced by this grinding is a mechanochemically active surface, but oxidation does not progress as it does when grinding in the atmosphere. The reason why the average particle size of the aggregate is 15 μm or less is to make the structure of the carbon material dense.

Molding is performed by casting this slurry. The reason why the casting method is used is that it is possible to manufacture a complex and thin molded body that is impossible with conventional carbon material manufacturing methods. The casting method mentioned here is the usual method used for ceramics.

For example, it is a method of injecting slurry into a porous gypsum mold to make a molded body, and there are methods such as slurry casting and solid casting, but these are not specific. The molded body obtained here is placed in a dryer, and in the case of a thermosetting resin, it is dried and hardened at the same time.

A carbon product is obtained by firing this molded body in an inert atmosphere. These carbon products may be further graphitized depending on the application and environment in which they are used.

(Example) Next, the present invention will be explained in detail with reference to Examples.

Similarly, parts in the raw material formulations indicate parts by weight.

Example 1 50 parts of water and 2 parts of histearic acid emulsion were added to 150 parts of VP231N to make a slurry. The aggregate particle size of this slurry was reduced to 10 in a water jet pulverizer.
Milled by μmK. This slurry was poured into a split plaster mold 1 shown in FIG. 1, left for 10 hours, excess slurry was discharged, and the mold was demolded to obtain a molded body. Place this molded body in the dryer.

It was dried at a temperature of 105°C. 1 in a non-oxidizing atmosphere
It was fired at 000°C. Furthermore, this was graphitized at a temperature of 2500°C or higher. Table 1 shows the physical property values of this carbon material.

Comparative Example 1 50 parts of medium pitch with a softening point of 80° C. was added to 100 parts of coal-based pitch coke powder with an average particle size of 30 μm.

I kneaded both arms with knead. After crushing this mixture with a crusher, it is molded using a hydraulic press at a pressure of 1. It was molded at Ot/am2. This was fired at 1000°C in a non-oxidizing atmosphere. Furthermore, this was graphitized at a temperature of 2500°C or higher.

Table 1 shows the physical property values of this carbon material.

Example 2! ! ! , VP231N), 80 parts of water and 2 parts of zinc stearate emulsion were added to prepare a slurry. This slurry was pulverized to an aggregate particle size of 5 μm using a water jet pulverizer. This slurry was injected into the plaster part 1 shown in Figure 1, left for 10 hours, excess slurry was discharged, and the mold was demolded to obtain a molded body. This molded body was placed in a dryer and dried at a temperature of 105°C. This was fired at 1000°C in a non-oxidizing atmosphere. Table 1 shows the physical property values of this carbon material.

Table 1 As is clear from Table 1, the carbon material of the example has a higher bulk density and bending strength than the carbon material of the comparative example, indicating that it is a dense material with high mechanical strength. .

(Effects of the Invention) According to the present invention, since there is no kneading process, there is no generation of steam such as tar pitch, resulting in a good working environment, and there is no judgment on the completion of kneading, thereby providing a carbon material with excellent physical properties. can. The present invention is an excellent method for producing industrial carbon materials.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view of a plaster section used in an embodiment of the present invention. Code explanation 1...Gypsum mold

Claims (1)

[Claims] 1. Carbon raw material powder, water-soluble resin, water or further additives are added to form a slurry, the slurry is pulverized using a water jet pulverizer to reduce the average particle size of the aggregate in the slurry to 15 μm or less, and after casting, drying and firing or further graphite processing is performed. A method for producing a carbon material characterized by the following: