JPH0158125B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to high strength and
This invention relates to a method for producing high-density carbon material. [Conventional technology] Among carbon materials, high strength and high density carbon materials are
It is used in a wide variety of fields, including various electrodes, nuclear graphite crucibles, heaters, mechanical sealing materials, sliding materials, current collector materials, and hot press dies. Conventionally, the manufacturing method of high-strength, high-density carbon materials has been to use coke, graphite, etc. with a particle size of 10 μm.
After finely pulverizing the powder, adding a binder such as coal tar pitch, and hot kneading, pulverizing again, molding, firing, and further impregnating with tar pitch, etc.
Carbon material with a bulk density of about 1.8 is produced by repeated re-firing, and the process is extremely complicated and time-consuming. Furthermore, the occurrence of microcracks due to the difference in shrinkage rate between aggregates such as coke or graphite and the binder, pores in the aggregate remaining after firing, generation of pores due to gasification of volatiles contained in the binder, or oxidation of the binder. There have been various problems such as partial development of non-graphitizable properties due to carbon dioxide, making it difficult and expensive to produce high-strength, high-density carbon materials. Therefore, various studies have been made in the past in order to obtain cheaper, high-grade, high-strength, high-density carbon materials. For example, (1) Tokuko Sho 53-
In Publication No. 18359, specific raw materials specified by the atomic ratio of hydrogen and carbon, quinoline soluble content, thermal deformation shrinkage rate, carbonization rate, etc. are finely pulverized to an average particle size of 10 μm or less,
They have proposed a method for producing a high-density, high-strength carbon molding material obtained by calcination carbonization and graphitization after molding. We are proposing a method for producing carbon material raw materials suitable for producing high-density carbon materials by heat-treating pitch and isolating the optically anisotropic spherules produced using a solvent fractionation method. [Problems to be solved by the invention] In all of these methods, the raw material powder itself has both aggregate and binder properties, and has self-sintering properties to prevent the generation of cracks and pores and to achieve high strength.・This is an attempt to manufacture high-density carbon material. However, method (1) involves mechanically crushing a coke-like carbon precursor material that has a porous, optically anisotropic flow pattern structure and a spherulite structure. The purpose is to manufacture high-density, high-strength carbon materials, which requires a special pulverizer to pulverize to an average particle size of 10 μm or less, and requires a large amount of operating cost and time. Furthermore, due to pulverization, it is difficult for the air contained in the product to escape during molding, making it impossible 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 that are extracted by the solvent are present inside the optically anisotropic small spheres that have been separated by the solvent, and the carbon material that has been molded and fired from the optically anisotropic small spheres also contains cracks. Internal cracks remain, making it difficult to obtain high-strength, high-density products. The present invention solves the above conventional problems, has self-sintering properties (can be molded and sintered without using a binder), does not generate intraparticle cracks, and has an average particle size of 10 to 40 μm. The purpose of this invention is to provide a method for producing high-strength, high-density carbon materials from relatively coarse-grained raw materials. [Means for Solving the Problems] In order to solve the above problems, the present invention provides that pitches are heated under a reduced pressure of 10 to 70 Torr or at 400 to 600°C.
Raise the temperature while blowing heated steam to 400~
By heating to 530℃ and removing low molecular components and decomposed oil, the carbon content is 92% by weight or more.
A raw material with a volatile content of 7 to 13% by weight up to 900℃ and a linear shrinkage rate of 6% or less when heated to 500℃ is crushed to an average particle size of more than 10μm and less than 40μm, then molded and fired. We are taking measures to do so. [Function] 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 more (all component amounts below are expressed simply as %), the volatile content up to 900℃ is 7 to 13%, and the linear shrinkage rate when heated to 500℃ is 6%. Raw materials with the following properties have the following characteristics during the firing process. (a) It is easily graphitized and can be easily increased in density. (b) It has self-bonding properties and does not cause internal foaming. (c) Internal cracks do not occur. Therefore, the average particle size with the above properties is 10~
A high-strength, high-density carbon material can be obtained by molding and firing raw materials with relatively coarse grains of 40 μm. [Specific Examples of the Invention] The present invention will be further explained in detail. In order to obtain the above-mentioned carbonaceous raw material, it is insufficient to simply heat coal tar or pitch at 350 to 550°C, or to modify the raw material by extracting it with a solvent after heat treatment. Raw materials with special characteristics can be produced by heating pitch to 400 to 530 degrees Celsius under reduced pressure of 10 to 70 Torr or while blowing heated steam at 400 to 600 degrees Celsius, and removing low molecular components and cracked oil components. can get. The decompression here is 10 to 70Torr, which means 400 to 70Torr.
By simultaneously heating to 530°C and reducing the pressure to 70 Torr or less, the removal efficiency of low molecular components and cracked oil components is increased, and the increase in carbon content is promoted.
Furthermore, it is difficult to achieve a reduced pressure of less than 10 Torr due to the generation of cracked gas, and there is no need to increase the reduced pressure more than necessary since there is no significant difference in quality from a reduced pressure of 10 to 70 Torr. In addition, the temperature of the heating steam was set at 400 to 600°C because if the temperature is lower than 400°C, the lower limit temperature of the heat treatment temperature range of 400 to 530°C, which is the original objective of the present invention, cannot be achieved. , a raw material exhibiting the characteristics of the present invention cannot be obtained. If the temperature exceeds 600°C, the heat treatment by steam blowing will proceed too much, and the volatile content will drop significantly, making it impossible to obtain a raw material exhibiting the characteristics of the present invention. Furthermore, the heating temperature was set at 400 to 530℃.
If the temperature is less than 400℃, the polycondensation will be insufficient, and the increase in carbon content and decrease in volatile content will not progress. On the other hand, if the temperature exceeds 530℃, polycondensation will proceed too much and the volatile content will decrease significantly. Raw materials exhibiting the characteristics of the invention cannot be obtained. 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, making it difficult to achieve high density. In addition, a range of 7 to 13% is suitable for the volatile content up to 900℃; if the volatile content is less than 7%, particles will not fuse or coalesce during the firing process, resulting in insufficient self-sintering properties and solidification. do not. 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 a large amount of volatile matter generated from inside the molded body causes foaming, making it impossible to achieve high density. Furthermore, the linear shrinkage rate of the molded product when heated to 500°C is required to be 6% or less. This value is usually 2t/cm ²
This value was measured by taking a sample from the molded body made by the above pressure molding. If this linear shrinkage rate exceeds 6%, it is because the shrinkage of the pores in the molded object is large.
Volatile matter generated up to 500°C becomes difficult to escape through the pores, creating pressure inside the molded body and causing cracks. Figure 1 shows a raw material with a linear shrinkage rate of 4% when heated to 500°C (Example 1 below), and Figure 2 shows a 10% raw material (Comparative Example 2 below), each pulverized to 100 μm and heated to 1000°C. A polarized light microscope photograph of carbon powder obtained by firing is shown. In FIG. 1, it can be seen that no cracks have occurred inside the particles, and in FIG. 2, it can be seen that cracks have occurred inside the particles. Carbonaceous raw materials with such properties have an average particle size of 10~
40μm (excluding 10μm), preferably 12-30μm
Grind it until it becomes. If the average particle size is less than 10 μm, not only will it be difficult for the contained air to escape during molding, making it impossible to increase the molding speed, but 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 crack. Not only is this easy to cause, but also a special crusher is required, 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 may be any method such as a vibrating ball mill, rotary mill, or hammer mill, but is not limited to any particular method. Furthermore, after molding the raw materials with the properties and particle size described above by a method such as injection molding or extrusion molding by adding oil or the like to give fluidity, the raw materials are fired for carbonization and graphitization in a non-oxidizing atmosphere. I do. [Examples and Comparative Examples] Coal tar and petroleum-based raw coke were treated under the conditions shown in the left column of Table 1 to obtain carbonaceous raw materials having the properties shown in the right column of Table 1. Examples are shown that satisfy the physical properties specified in the present invention, and comparative examples are shown that do not.

【table】

[Table] The mixture was centrifuged to separate and collect the insoluble matter. Next, the carbonaceous raw material with the properties in the right column of Table 1 was ground with a hammer mill to an average particle size of 10 μm to 40 μm, and 2 t/cm After molding into a rectangular parallelepiped of 90 x 50 x 50 mm at a pressure of ² , it was heated to 1000 °C at a rate of 12 °C/Hr in a nitrogen atmosphere in a container filled with coke powder, and then carbonized, and then in an argon atmosphere. 2500℃ at 10℃/min
A graphitized product was obtained. The results are shown in Table 2. In addition, carbide obtained in the same manner as above using the carbonaceous raw material of Example 1 in Table 1 and changing the average particle size,
Table 3 shows the properties of the graphitized product.

【table】

【table】

[Table] (Discussion) As is clear from Table 2, the properties of the carbide and graphitide obtained in the example of the method of the present invention are larger than those of the comparative example in terms of bulk density, shore hardness, and bending strength. The specific resistance is low, making it possible to obtain the desired high-strength, high-density carbon material. Further, as is clear from Table 3, good results cannot be obtained even if the average particle diameter is larger or smaller than the 10 to 40 μm specified in the present invention. [Effects of the Invention] As described above, when the specific carbonaceous raw material specified in the present invention is used, self-sintering properties can be achieved with relatively coarse grained raw material without pulverizing it with a special pulverizer. with high strength and no intra-particle cracks.
High-density carbon material can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a polarized light micrograph of carbon powder obtained using the raw material of Example 1, and FIG. 2 is a polarized light micrograph of carbon powder obtained using the raw material of Comparative Example 2.

Claims (1)

[Claims] 1 Pitch under reduced pressure of 10 to 70 Torr or 400 Torr
The temperature is raised while blowing heated steam at ~600℃.
When heated to 400-530℃, low-molecular components and decomposed oil are removed, and the molded product has a carbon content of 92% by weight or more, a volatile content of 7-13% by weight up to 900℃, and a molded product when heated to 500℃. A method for producing a high-strength, high-density carbon material, which comprises pulverizing a raw material with a linear shrinkage rate of 6% or less to an average particle size of more than 10 μm and less than 40 μm, followed by molding and firing.