JPH0227302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a carbon molded body, and more specifically, it is possible to obtain a high-density and high-strength molded body without deformation of the molded body and by suppressing the generation of air bubbles. Regarding the method.

Conventionally, as a method for manufacturing high-strength carbon molded bodies, a method has been proposed in which a molded body is produced using carbon fibers as a binder using a thermosetting resin, pitch, etc., and then fired under pressure (Japanese Patent Application Laid-Open No. 1989-1999). - No. 52912).

However, with this method, the molded product tends to lose its shape during firing, and the gas generated during firing creates bubbles in the product, making it impossible to obtain a product with sufficient strength. .

Therefore, as a result of intensive studies to solve the problems in the conventional technology, the inventor of the present invention found that
By appropriately oxidizing pitch powder or pitch fiber, and then molding the resulting oxidized pitch with appropriate molding pressure and then firing, the molded product does not lose its shape and can suppress the formation of air bubbles. The present invention was completed based on this finding.

That is, in the present invention, firstly, the oxygen content is 3 to 5.
% by weight of pitchchi powder or pitchchi fiber, and then the obtained oxidized pitchchi
The present invention provides a method for producing a carbon molded body, which is characterized by molding at a molding pressure of 100 Kg/cm ² G or more and less than 500 Kg/cm ² G, and firing the obtained molded body.

In addition, the present invention secondly oxidizes pitch powder or pitch fiber so that the oxygen content is 3 to 5% by weight, and then blends carbon fiber or infusible pitch fiber into the obtained oxidized pitch. 100 after
The present invention provides a method for producing a carbon molded body, which is characterized by molding at a molding pressure of Kg/cm ² G or more and less than 500 Kg/cm ² G, and firing the obtained molded body.

The pitch used as a raw material in the present invention may be either petroleum-based pitch or coal-based pitch. The softening point of the pitch is preferably 250 to 380°C, and in some cases, a mesophase pitch having an optically anisotropic phase content of 80% or more or substantially 100% is used.

In the present invention, such a pitch has a diameter of 50 mm.
Pitch powder obtained by grinding to ~500μ, preferably 100 to 300μ, or yarn diameter obtained by melt spinning such pitch to 5 to 30μ, preferably 10 to
Use 20μ pitch fiber. The conditions for melt spinning vary depending on the type of pitch used as the raw material.
Although it cannot be determined unambiguously, conventional conditions may generally be used. Specifically, the spinning temperature is 250 to 400°C, preferably 260 to 400°C.
380℃, spinning speed 100-1500m/min, preferably
Pitch fibers are obtained by performing the process at a speed of 200 to 1000 m/min.

In the present invention, the pitch powder or pitch fiber thus obtained is first subjected to an oxidation treatment.
In this oxidation treatment, the temperature is usually raised to 300-400°C, preferably 325-375°C in an oxidizing gas atmosphere, and the oxygen content in the pitchi powder or pitchi fiber is 3-5% by weight, preferably 3.5-5%. Do this so that the amount is 4.5% by weight. The temperature increase rate may be 1 to 50°C/minute, preferably 10 to 20°C/minute. Here, examples of the oxidizing gas include oxygen, ozone, air, nitrogen oxides, sulfur dioxide gas, and mixtures thereof. In addition, as oxidation promoters, inorganic acids such as hydrogen chloride, hydrogen bromide, sulfuric acid, nitric acid, etc.; metal salt compounds such as sodium nitrate, potassium nitrate, sodium sulfate, potassium sulfate, aluminum chloride, etc.; metal oxides such as sodium oxide, Potassium oxide, potassium permanganate, etc.; ammonium salt compounds such as ammonium sulfate may also be used.

The oxidized pitch powder or pitch fiber is molded into a pulverized product. Therefore, the oxidized pitch powder can be left as is, but the oxidized pitch fiber can be reduced in length by 50 to 50 mm in a mortar.
Grind it to a length of 1000μ, preferably 50 to 200μ.

Next, the pulverized oxidized pitch product thus obtained is molded into a desired shape. Here the molding is usually
This is carried out by compression molding at a molding pressure of 100 Kg/cm ² G or more and less than 500 Kg/cm ² G. Molding pressure is 100
If it is less than Kg/cm ² G, the strength after sintering will be insufficient, which is not preferable. On the other hand, even if the molding pressure is 500 kg/cm ² G or more, no further effect can be expected.

Furthermore, the obtained molded body is fired. That is, the obtained molded body was heated for 800 min in an inert gas atmosphere.
Carbonization is carried out by raising the temperature to ~1500°C, preferably 1000~1200°C. Examples of the inert gas include nitrogen gas, helium gas, and argon gas. Note that this firing may be performed under vacuum. Furthermore, if necessary, it may be graphitized by heating to 2000 to 2500°C.

In this way, the first carbon molded body of the present invention can be manufactured.

In addition, the second aspect of the present invention is to oxidize pitch powder or pitch fiber so that the oxygen content becomes 3 to 5% by weight, and then add carbon fiber or non-carbon fiber to the obtained oxidized pitch powder. It is unique in that it is blended with fused pitch fibers and molded under a specific molding pressure.

There are no particular restrictions on the carbon fiber, but for example, petroleum pitch or pitch fiber obtained by melt-spinning petroleum pitch may be infusible and fired, and a yarn diameter of 5 to 20 μm may be used. be able to. Further, as the infusible pitch fiber, one obtained in the infusible process when producing carbon fibers can be used. Here, carbon fibers or infusible pitch fibers are blended in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the oxidized pitch pulverized product. If the blending amount of carbon fiber or infusible pitch fiber is less than the above ratio, sufficient addition effect cannot be obtained, and if the blending amount of carbon fiber or infusible pitch fiber exceeds the above ratio, the molded product The internal bonding force is weak and a molded product with high mechanical strength cannot be obtained.

By blending carbon fibers or infusible pitch fibers, it becomes possible to further improve the strength of the molded product produced.

In the second aspect of the present invention, the molded body may be molded in the same manner as in the first aspect of the present invention, and the obtained molded body may be fired.

According to the first aspect of the present invention as described above, a molded article that does not lose its shape can be obtained. Moreover, there are no air bubbles in the molded product, and a molded product with high density and high strength can be obtained.

Furthermore, according to the second aspect of the present invention, a molded article with further improved strength can be obtained.

Therefore, the present invention can be effectively used in manufacturing mechanical parts, electrical/electronic equipment parts, and the like.

Example 1 Petroleum-based pitch with a softening point of 280°C was melt-spun to obtain pitch fiber with a thread diameter of 10 μm. This pitch fiber was heated in air from room temperature to 350° C. at a heating rate of 20° C./min to obtain oxidized pitch fiber. The oxygen content in this oxidized pitch fiber was 4.0% by weight. Next, this oxidized pitch fiber was crushed in a mortar, and the resulting crushed product was compression-molded at a pressure of 400 kg/cm ² G to obtain a disk with a diameter of 12 mm and a wall thickness of 2 mm. This disk was heated to 1000° C. in a nitrogen gas atmosphere at a heating rate of 10° C./min and fired. As a result, a high-density carbon molded body having a density of 1.75 g/ml (density of raw material pitch 1.31 g/ml) without deformation was obtained.

Example 2 Petroleum-based pitch with a softening point of 280°C is crushed to a diameter of 100μ or less, and the resulting pitcher powder is accelerated from room temperature to 350°C at a heating rate of 10°C/min under air circulation to contain oxygen. Oxidized pitch powder with an amount of 3.8% by weight was obtained. 400Kg/of the obtained oxidized pitch powder
Compression molding was performed at a pressure of cm ² G to obtain a disc with a diameter of 12 mm and a wall thickness of 2 mm. This disk was placed in a nitrogen gas atmosphere for 10
The material was heated to 1000°C at a heating rate of 0°C/min for firing. As a result, a high-density carbon molded article having a density of 1.74 g/ml without deformation was obtained.

Comparative Example 1 Pitch powder obtained by pulverizing petroleum pitch with a softening point of 280° C. to a diameter of 100 μm or less was compression molded at a pressure of 400 Kg/cm ² G to obtain a disc with a diameter of 12 mm and a wall thickness of 2 mm.
This disk was heated to 400°C at a heating rate of 10°C/min to oxidize the surface. Next, this disk was heated at a heating rate of 10°C/min in a nitrogen gas atmosphere.
It was heated to 1000℃ and fired. As a result, the disc lost its shape and foamed, making it impossible to measure the bulk density of the molded product.

Example 3 A mixture of 50 parts by weight of carbon fibers and 100 parts by weight of the pulverized oxidized pitch fiber in Example 1 was heated to a pressure of 400 kg/cm ² G to form a mixture with a diameter of 12 mm and a wall thickness of 2.
Compression molded into a mm disc and placed in a nitrogen atmosphere.
It was fired by heating to 1000°C at a heating rate of 10°C/min. As a result, a high-density carbon molded body having a density of 1.76 g/ml without deformation was obtained.

Example 4 A mixture of 100 parts by weight of oxidized pitch powder in Example 2 and 50 parts by weight of carbon fiber was mixed into 400 parts by weight.
It was compression molded into a disc with a diameter of 12 mm and a wall thickness of 2 mm at a pressure of Kg/cm ² G. The obtained disk was heated at a heating rate of 10°C/min in a nitrogen gas atmosphere,
Fired at 1000℃. As a result, a high-density carbon molded article having a density of 1.75 g/ml without deformation was obtained.

Comparative Example 2 A mixture of 50 parts by weight of carbon fiber mixed with 100 parts by weight of pitch powder obtained by crushing petroleum pitch with a softening point of 280°C to a diameter of 100 μ or less was compression molded at a pressure of 400 kg/cm ² G. A disk with a diameter of 12 mm and a wall thickness of 2 mm was obtained. The obtained disk was placed in a nitrogen gas atmosphere.
It was heated to 1000°C at a heating rate of 10°C/min and fired. As a result, the disc was deformed and foamed, so that the bulk density of the molded product could not be measured.

Claims (1)

[Claims] 1. Pitch powder or pitch fiber is oxidized so that the oxygen content is 3 to 5% by weight, and then the resulting acid pitch is oxidized to 100 Kg/cm ² G or more, 500 Kg/
1. A method for producing a carbon molded body, which comprises molding at a molding pressure of less than cm ² G and firing the resulting molded body. 2. Pitch powder or pitch fiber is oxidized so that the oxygen content is 3 to 5% by weight, and then carbon fiber or infusible pitch fiber is blended with the obtained oxidized pitch, and then 100Kg/cm ² G More than 500Kg/
1. A method for producing a carbon molded body, which comprises molding at a molding pressure of less than cm ² G and firing the resulting molded body. 3 5 parts of carbon fiber per 100 parts by weight of oxidized pitch
50 parts by weight of the manufacturing method according to claim 2.