JPH05330914A - Production of carbonaceous material having highly mirror finished surface - Google Patents

Abstract

PURPOSE:To readily obtain a dense carbonaceous material having a good highly mirror finished surface by heat-treating a mixture of a pitch or green cokes with an inorganic compound soluble in acids, then treading the heat-treated mixture with an acid, forming, burning and polishing the resultant carbonaceous powder. CONSTITUTION:An inorganic compound soluble in acids is added to pitches or green cokes and the resultant mixture is heat-treated. The heat-treated product is then treated with an acid and the obtained carbonaceous powder is formed and burned. The resultant compact is subsequently polished to afford the objective carbonaceous material. The mixture is preferably heat-treated at >=150 deg.C for 30min to 24hr. The heat-treated mixture can be burned at a higher temperature (350-1000 deg.C) and volatiles, as necessary, can be removed. In order to obtain a good molding, the average particle diameter of the raw material powder is <=30mum, preferably 0.1-5mum. The objective lighter carbonaceous material than metallic materials or glass materials, hardly damaged and good in thermal shock properties can readily be obtained and the labor and processes can be shortened according to this method for producing time carbonaceous material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon material having a high mirror surface, and more particularly to a method for producing a carbon material having an excellent polished surface used for a substrate of a magnetic disk or the like.

[0002]

2. Description of the Related Art Conventionally, metals such as aluminum, nickel, and titanium, and alloys thereof, glass-coated ceramics, inorganic substances such as glass plates, and carbon materials such as amorphous carbon have been used as substrates for magnetic disks. ing. These carbon materials are used as a substrate of a magnetic disk after molding, curing, carbonizing a thermosetting resin such as phenol resin, graphitizing if necessary, and then densifying and polishing.

Further, a thermosetting resin such as a phenol resin is cured and then molded, and after carbonization, a high temperature of 2,000 ° C. or higher,
It is isotropically molded (hereinafter referred to as HIP) at a high pressure of 1,000 atm or more, and is polished and used as a substrate of a magnetic disk.

[0004]

However, since these metal materials and inorganic materials are heavy, a large load is applied to the disk drive drive system, it is difficult to miniaturize the drive device, and the thermal expansion coefficient is large. There are problems such as poor stability, metal materials that are soft and easily scratched and chemically unstable, and inorganic materials such as glass that are brittle, easily cracked, and have poor thermal shock resistance. It was

Further, a carbon material such as amorphous carbon obtained by the conventional method is not sufficiently dense in structure, has a rough polished surface, and has poor characteristics as a magnetic disk substrate.
In the method using, the equipment becomes large, the production efficiency is poor,
There was a problem that the cost was high.

[0006]

In view of such a situation, the present inventors have made diligent studies and as a result, as a result of adding a specific inorganic compound to pitches or raw coke and subjecting the heat-treated product obtained by heat treatment to acid treatment. It was found that a dense special carbon material having a good high mirror surface can be obtained by using the carbonaceous powder treated by the method, and the present invention has been completed.

That is, the gist of the present invention is that carbon obtained by adding an acid-soluble inorganic compound to pitches or raw coke, heat-treating the resulting mixture, and then treating the heat-treated product with an acid. In another aspect of the present invention, there is provided a method for producing a carbon material having a high mirror surface, which comprises molding a fine powder, firing the powder, and polishing the molded body. The present invention will be described in detail below.

First, as pitches or raw coke (hereinafter referred to as "carbonaceous raw material") used in the present invention, tar pitch produced by distillation and heat treatment of coal tar, heavy petroleum oil, and its Catalytic cracked oil or distillation residual oil, heat-treated products such as hydrogenated cracked oil, or pitch and solvent-treated products obtained by polycondensing low molecular weight compounds such as naphthalene in the presence of a catalyst (hereinafter, these are referred to as “pitch”). , "And a delayed coker, an autoclave, etc., using these as raw materials for 300 to 50
Raw coke obtained by heat treatment at 0 ° C. for about 1 to 48 hours is used.

The carbonaceous raw material used in the present invention is 3
A fraction having a fraction of 00 ° C or less of 10% or less, preferably a fraction of 360 ° C or less of 10% or less, and most preferably a fraction of 360 ° C or less of 1 to 5% is used. The acid-soluble inorganic compound is preferably an alkaline earth metal compound, and examples thereof include chlorides such as calcium (Ca), barium (Ba), and magnesium (Mg), sulfates, carbonates, and oxides. Although it can be used, carbonates and oxides are preferable because they are easily treated.
In particular, oxides are preferable, and oxides of magnesium and calcium are most preferable.

The amount of the inorganic compound added is such that the ratio (weight ratio) of carbonaceous raw material: inorganic compound is 99: 1 to 1:99.
Is preferred, and more preferably 90:10 to 10:90.
And most preferably 80:20 to 20:80. As an addition method, a carbonaceous raw material and an acid-soluble inorganic compound co-powder are blended. In the case of pitches,
It is also possible to heat and melt it into a liquid state, and blend the inorganic compound powder with it. Further, the carbonaceous raw material can be dispersed or dissolved in a solvent and mixed in the solvent. Further, raw coke can be dispersed in a solvent and mixed.

The heat treatment of the mixture is preferably carried out at 150 ° C. or higher for 30 minutes to 24 hours, more preferably 180 to 350.
30 ° C. to 10 hours is preferred, most preferably 20
It is good to carry out at 0 to 300 ° C. for 30 minutes to 5 hours. Further, the heat-treated product can be fired at a higher temperature (350 to 1000 ° C.), and volatile matter can be removed as necessary.

The pressure during the heat treatment is high pressure (1 to 100a).
tm) is also possible, but it may be at atmospheric pressure. The atmosphere can be treated in an inert gas, in the presence of oxygen or even in coke breeze, but it is preferable that oxygen is present, and the concentration of oxygen can be adjusted to 10 to 50% for treatment.

The volatile matter (V
M) is preferably 30% by weight or less, more preferably 5 to 25
% Is preferred, most preferably 10 to 20%. The toluene-soluble content (γ resin amount) when measured by adjusting the average particle size to 15 to 20 μm is preferably 20% or less, more preferably 1 to 15%, and most preferably 2 to 10%.
Is.

The treated product thus obtained is, if necessary, pulverized and then treated with about 5 to 35% of an inorganic acid such as hydrochloric acid or sulfuric acid or about 5 to 50% of an organic acid such as acetic acid. Then, the inorganic compound can be dissolved and removed to obtain a product, but as the acid, an inorganic acid is advantageous because it has a strong dissolving power.
The dissolution may be performed at room temperature, but may be performed at a high temperature (50 to 100 ° C.) to accelerate the dissolution.

Further, the heat-treated product and the acid may be mixed and treated in a batch, but it is also possible to perform the treatment continuously while circulating the acid. If the treated product is a powder, it is in a tangible state, and if it is a lump, it is crushed if necessary. The pulverization of the heat-treated product can be carried out by a conventional method, such as compression force, shearing force,
Friction force, impact force, etc. can be used, and a combination thereof may be used.

In order to obtain a good molded product, the average particle size of the raw material powder is 30 μm or less, preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, and most preferably 0.
It is preferably 1 to 5 μm. Furthermore, if the maximum particle size of the carbonaceous powder is too large, the structure becomes inhomogeneous and the characteristics deteriorate. Therefore, the maximum particle size of the carbonaceous powder is 50 μm or less, more preferably 1 to 20 μm, and most preferably 1 to 10 μm.
μm.

The crushed product can be molded by ordinary molding, cold isostatic pressing or the like to produce a special carbon material. Firing of the molded body can be performed in an inert gas or in a coke breeze, and is performed at a temperature of 800 to 1000 ° C. for about 30 minutes to 4 days. These firings can be performed without a load, but it is also possible to perform firing in a state in which a load is applied with the weight of the carbon material so that the molded body is not deformed, and it is also possible to perform firing in a mold.

Further, if necessary, graphitization may be carried out in a Tammann furnace,
It is usually 200 by conventional methods such as Acheson furnace and induction heating furnace.
It is performed at 0 to 3000 ° C. for about 30 minutes to 4 days. These graphitizations can be performed without a load, but it is also possible to graphitize under a load with the weight of the graphite material so that the molded body will not be deformed. You can also do it.

The molded body can be graphitized as it is, but it can also be graphitized by processing it into a required size. The molded product produced by the above method is processed into a required size and polished by a conventional method to form a carbon material having a high mirror surface, which is used for a magnetic disk substrate or the like. For example, by polishing with an abrasive such as alumina or magnesia, the surface roughness is usually 2.0 μm or less, preferably 1.0 μm.
A carbon molded product having the following mirror surface can be obtained.

[0020]

【Example】

Example 1 Commercially available impregnated pitch powder and commercially available magnesia (MgO) powder were mixed at a ratio of 30/70, and then heat-treated in air at 250 ° C. for 1 hour. The heat-treated product was added with concentrated hydrochloric acid at room temperature.
The product was obtained by immersing it in 0-fold diluted hydrochloric acid for 1 day, then washed with hydrochloric acid and dried. The average particle size of the product is 1μ
m and the maximum particle size was 3 μm. The product was molded by a mold press into a disk having a diameter of 60 mm and a thickness of 10 mm, fired, graphitized (2400 ° C.), and then sliced to obtain a disk-shaped molded product having a thickness of 2 mm. The molded body was polished by a conventional method using alumina and then magnesia as an abrasive, to obtain a molded body having a mirror surface with a surface roughness of 0.1 μm or less. No defects were observed when the mirror surface was observed under a polarizing microscope at a magnification of 100 times.

Example 2 A commercially available impregnated pitch powder and a commercially available magnesia (MgO) powder were mixed at a ratio of 60/40 and then heat-treated at 250 ° C. in air. The heat-treated product was immersed in hydrochloric acid diluted with concentrated hydrochloric acid 10 times at room temperature for one day and then washed with hydrochloric acid and dried to obtain a product. The product is finely ground to an average particle size:
A pulverized product having a size of 1.3 μm and a maximum particle size of 4.0 μm was obtained. The pulverized product was molded in the same manner as in Example 1, and the molded product obtained was fired, graphitized, and sliced to obtain a molded product. The molded body was polished in the same manner as in Example 1. No defect was observed when the mirror surface of the molded body was observed under a polarizing microscope at a magnification of 100 times.

[0022]

According to the present invention, a dense carbon material, which is lighter in weight than conventional metallic materials and glass materials, is less likely to be scratched, and has good thermal shock resistance, can be easily manufactured, and the labor and the process can be shortened.

Claims (1)

[Claims] 1. A carbonaceous powder obtained by adding an acid-soluble inorganic compound to pitches or raw coke, heat-treating the resulting mixture, and then treating the heat-treated product with an acid to form a carbonaceous powder, A method for producing a carbon material having a high mirror surface, which comprises firing and polishing the molded body.