JPS6144704A - Production of high-strength and high-density carbonaceous material - Google Patents

Abstract

PURPOSE:To obtain easily a high-strength and high-density carbonaceous material without causing cracks in particles, by pulverizing a carbonaceous raw material having a specific carbon content, volatile content, linear shrinkage of a molded article, etc., to a relatively coarse particle size, molding the pulverized material, and firing the resultant molded material. CONSTITUTION:Pitch is heated under about 10-70Torr reduced pressure to about 400-530 deg.C, and the carbon content is increased. Low-molecular weight components and decomposed oil are removed at the same time to prepare a carobnaceous material having >=92wt% carbon content, 7-13wt% volatile content up to 900 deg.C and <=6% linear shrinkage of the resultant molded article when heated to 500 deg.C. The resultant carbonaceous material is then pulverized to give >10mum-<=40mum average particle diameter, molded and fired to afford the aimed high-strength and high-density carbonaceous material suitably used for sliding materials, dies for hot-pressing, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a high-strength, high-density carbon material using a specific carbonaceous material as a raw material.

[Conventional technology]

Among carbon materials, high-strength and high-density carbon materials are used in a wide variety of fields, including various electrodes, nuclear graphite crucibles, heaters, mechanical run materials, sliding materials, current collector materials, and hot press dies. Conventionally, the method for producing high-strength, high-density carbon materials is to pulverize coke or graphite to a particle size of 10 tz or less, add a binder such as coal tar pitch to the mill, hot knead it, and then It is manufactured as a carbon material with a bulk density of about 18 by repeating pulverization, molding, firing, impregnation with tar pitch, etc., and re-firing, and the process is extremely complicated and requires flat bending. Furthermore, the occurrence of minute cracks and cracks due to the difference in shrinkage rate between aggregates such as coke or graphite and the binder, pores in the aggregate remaining after firing, and the occurrence of pores due to the gasification of volatiles contained in the binder. In addition, there are various problems such as partial non-graphitization due to oxidation of the binder, making it difficult to produce high-strength, high-density carbon materials and expensive. Therefore, various studies have been made to obtain a 7-ton carbon material of high quality, high strength, and high density at a lower cost. For example, in ('i) Japanese Patent Publication No. 53-18359, specific raw materials defined by the atomic ratio of hydrogen and carbon, quinone-11 soluble content, thermal deformation shrinkage rate, carbonization rate, etc.
They have proposed a method for producing a high-density, high-strength carbon molding material obtained by pulverizing the material to 0 μm or less, then calcination carbonization after molding, and comparing it with graphite. A method for producing carbon material raw materials suitable for producing high-density carbon materials by heat-treating petroleum-based heavy oil or coal tar pitch and isolating the optically anisotropic spherules produced using a solvent fractionation method. is suggesting.

[Problem that the invention seeks to solve]

In all of these methods, the raw material powder itself has both aggregate and binder properties, and it has self-sintering properties to prevent cracks and pores from forming, producing high-strength, high-density carbon materials. This is an attempt to

However, method (1) mechanically crushes a coke-like carbon precursor material that has a porous, gaseous structure that exhibits optical anisotropy, and a coke-like carbon precursor material that contains a spherulite structure. The aim is to produce a high-density, high-strength carbon material by pulverizing the particles to an average particle size of 0 μm or less, which requires a special pulverizer and requires a large amount of operating cost and time. During molding, it is difficult for the contained air to escape, making it difficult to increase the molding speed, and the pores through which gas generated during the firing process can escape become smaller, resulting in gas pressure being applied to the inside of the molded product, which tends to cause cracks in the fired product.

In addition, in method (2), cracks generated by extraction with a solvent are present inside the optically anisotropic small spheres separated by the solvent.
These internal cracks remain in the carbon material produced by molding and firing these optically anisotropic small spheres, making it difficult to obtain high-strength, high-density Kashima.

The present invention solves the above-mentioned conventional problems, has self-sintering properties (can be molded and sintered without using a binder), does not generate intra-particle cracks, and has an average particle size of 1 (1 to 1). 4
The object of the present invention is to provide a method for producing a high-strength, high-density carbon material from a raw material with a relatively coarse particle size of 0/z m.

[Means for solving problems]

In order to solve the above problems, the present invention provides a carbon content of 9
2% by weight or more, volatile content at 900℃1 is 7 to 13% by weight
A method is adopted in which a raw material whose linear shrinkage rate of a molded body when heated to 500° C. is 6 or less is pulverized to an average particle size of more than 10 μm and 40 μm or less, then molded and fired.

[Effect]

The present inventor investigated the correlation between the quality of the carbon material raw material, the shrinkage behavior of the molded body during the heating process, and the crack generation behavior within the particles, and obtained the following knowledge.

The carbon content is 92% or higher (hereinafter, all component amounts are simply referred to as "Jyuuta"), the volatile content up to 900℃ is 7-13%, and the linear shrinkage rate when heated to 50011 is 6. Raw materials with properties below have the following characteristics during the firing process: (a) They are easily graphitized and can be easily densified. (b) They have self-fusing properties and do not cause internal foaming. do not have.

(c) Internal cracks do not occur.

Therefore, the average particle size having the above-mentioned properties is 10 to 40μ.
A high-strength, high-density carbon material can be obtained by molding and firing a relatively coarse-grained raw material of nO [Specific Example of the Invention] The present invention will be further described in detail.

In order to obtain the above-mentioned carbonaceous raw material, conventional thermal polycondensation in which coal tar or pitch is simply heated at 350 to 550°C is insufficient, and the raw material having the characteristics of the present invention
The temperature was raised under reduced pressure of θ~70 Torr, and the temperature was increased to 400~530
℃ to increase the carbon content and remove low molecular components and cracked oil.Also, as a method equivalent to reduced pressure heat treatment, benzene, toluene, xylene, decrystallized naphthalene can be obtained after heat treatment under normal pressure. It is also possible to use a method in which the volatile content is adjusted by extraction with an aromatic solvent such as oil, decrystallized anthracene oil, or crude benzene.

The carbon content of the carbonaceous raw material according to the present invention must be 92% or more, and if the carbonaceous raw material is less than 92%, atoms other than carbon will decompose and gasify during the firing process, resulting in an increase in weight loss. Atoms other than carbon inhibit graphitization, resulting in
Change becomes difficult.

In addition, the volatile content up to 900°C is suitable for a range of 7 to 13 parts. If the volatile content is less than 7 parts, particles will not fuse or separate during the firing process, resulting in insufficient self-sintering properties. Does not solidify. On the other hand, if it exceeds 13%, the molded body undergoes too much softening and fusion during the firing process, the pores between the particles are closed, and the multi-I volatiles generated from inside the molded body cause foaming, making it impossible to achieve high density.

In addition, the linear shrinkage rate of the molded product when heated to 500℃ is 6
Persons in charge or below are required. This value is usually measured by taking a specimen from a molded product made by pressure molding at a pressure of 2 or more. If this linear shrinkage rate exceeds 6, the shrinkage of the pores in the molded body is large, and volatile matter generated up to 500°C passes through the pores and escapes. Figure 1 shows a raw material with a linear shrinkage rate of 4 when heated to 500°C (Example 1 below)
And in Figure 2, the raw materials for Section 10 (Comparative Example 2 described later) are shown.
Figure 1 shows no cracking inside the particles, and Figure 2 shows a polarized light microscope photograph of carbon powder obtained by crushing to ln n )t m and firing at 1000°C. It can be seen that internal cracks have occurred.

The carbonaceous raw material having such properties has an average particle size of 10 to 40
μm (excluding 10 μm), preferably 12 to 30 μm
Grind to a vc consistency. If the average particle size is less than 10 tt m, the contained air will not escape easily during molding, making it difficult to increase the molding speed, and the pores through which gas generated during the firing process can escape will also become smaller, causing the pressure of the gas generated inside the molded body to increase. Not only is it easy to cause cracking, but it also requires a special crusher, which requires a lot of labor and operating costs.

Moreover, if the average particle size exceeds 40 μm, the molding density will not increase even if pressure molded, and it will be difficult to increase the density.

The pulverization method is not limited and may be any method such as a vibrating ball mill, a rotary mill, or a thermometer mill.

Furthermore, the raw materials with the above properties and particle size are molded into molds,
Alternatively, after adding oil or fat to give fluidity and molding by a method such as extrusion molding, baking is performed for carbonization and graphitization in a non-oxidizing atmosphere0 [Example and Comparative Example] Coal tar and petroleum-based The raw coke was treated under the conditions shown in the left column of Table 1 to obtain a carbonaceous raw material having the properties shown in the right column of Table 1. Examples are shown for those that satisfy the physical properties specified for wood shells, and comparative examples are for those that do not. Next, the carbonaceous raw materials having the properties in the right column of Table 1 were milled with an average particle size of 10 μm to 40 μm in a hammer mill. Grind within the range, 2t/
After molding into a 90x50x50 rectangular parallelepiped with a pressure of d,
In a container filled with coke powder, heated at 12°C in a nitrogen atmosphere.
After carbonizing by raising the temperature to 1000°C at a rate of 1 hour, the temperature was raised to 2500°C at a rate of 10°C in an argon atmosphere to obtain a graphitized product. The results are shown in Table 2.

Table 3 shows the properties of carbides and graphitized products obtained in the same manner as above using the shredded carbonaceous raw material of Example 1 in Table 1 and changing the average particle size.

(Discussion) As is clear from Table 2, A
The properties of the carbonaceous material and graphitized material are that the bulk density, hardness, and bending strength are higher than those of the comparative example, and the electrical resistivity is lower, thereby obtaining the desired high strength and high density carbon material. be able to.

Furthermore, as is clear from Table 3, the average particle size may also be larger or smaller than 0 to 40 μm, which is defined in the present invention.

〔Effect of the invention〕

As described above, when one specific carbonaceous raw material specified in the present invention is used, the relatively coarse raw material has self-sintering properties and has intragranular cracks even without being pulverized by a special pulverizer. It is possible to easily obtain a high-strength, high-density carbon material that does not cause rips or rips.

[Brief explanation of drawings]

Figure 1 shows the raw material whose linear shrinkage rate of the molded product is 6 or less when heated to 5()0°C, and Figure 2 shows the raw material whose linear shrinkage rate exceeds 6 when heated to about 100 μm and heated to 1000°C. Fig. 2 is an yL microscopic photograph of a cross section of a particle of carbon powder obtained by firing the carbon powder. Patent applicant: Sumitomo Metal Industries, Ltd. Drawing J-1
F; (no barbarism in the content) Figure 1 Figure 2 Procedural amendment (-j5 formula) % formula % 2 Title of the invention Method for manufacturing high-strength, high-density carbon material 3,
Relationship with the case of the person making the amendment Patent applicant name 4 Agent 〒136 8 Contents of amendment (1) From page 12, line 17 of the specification to page 12, line 1 [Figure 1 is 500°C...Polarized light micrograph. "Figure 1 is a polarized light micrograph of carbon powder obtained using the raw material of Example 1, and Figure 2 is a polarized light micrograph of carbon powder obtained using the raw material of Comparative Example 2. Yes,” he corrected. (2) Replace and correct Figures 1 and 2 with the attached ones. that's all

Claims (1)

[Claims] (1) A raw material with a carbon content of 92% by weight or more, a volatile content of 7 to 13% by weight up to 900°C, and a linear shrinkage rate of 6% or less of the molded product when heated to 500°C, with an average particle size of 10 μm. A method for producing a high-strength, high-density carbon material, which comprises pulverizing the material to a size exceeding 40 μm or less, then molding and firing.