JPH0360415A - Production of high density and high strength isotropic carbon material and starting material of carbon material for injection molding - Google Patents

Abstract

PURPOSE:To easily obtain a high density and high strength isotropic carbon material used for a heat resistant material of a complex shape by baking and graphitizing a molded body of a mixture of carbonaceous mesophace spherules having self-sintering property with a pitch binder satisfying prescribed conditions. CONSTITUTION:Coal tar pitch or petroleum pitch is heated at a prescribed temp. to form mesophase spherules in the optically isotropic pitch. These carbonaceous mesophase spherules having self-sintering property are mixed with 25-75wt.% pitch having <=200 deg.C softening point as a binder. This mixture is injection-molded, then baked and graphitized.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is an invention of a method for manufacturing an isotropic high-density, high-strength carbon material used for crucibles, nozzles, heat-resistant materials with complicated shapes, etc., and the invention of the method. This relates to carbon material raw materials that are directly used in the implementation of

<Conventional technique> Carbonaceous mesophase spherules are known as raw materials for isotropic high-density, high-strength carbon materials. Carbonaceous mesophase spherules are carbonaceous mesophase spherules with coal tar pitch and right-handed pitch of 350 to 50.
Mesophase spherules are produced in optically isotropic pitch during heat treatment at a temperature of 0°C, and are separated from the pinge matrix by solvent fractionation.

For example, according to Japanese Patent Publication No. 60-25364, by using a solvent with a slightly low extraction power for pitch, such as benzene or oil in tar, to separate small spheres, β
It has been shown that a raw material with excellent self-sintering properties can be obtained by allowing some of the components to remain together with the small spheres and further calcining the material in an inert atmosphere at a temperature of 200 to 450°C. If the raw material obtained by this method is used, an isotropic, high-density, high-strength carbon material with a high density of 1.85 g/cd or more and a sprouting strength of 800 kg/cd or more can be easily obtained.

However, the conventional manufacturing method for carbon materials is to first form the carbon material into a rectangular or cylindrical shape by rubber molding, etc., then perform firing and graphitization treatment to produce the carbon material, and then obtain the product shape by cutting, etc. As a result, the yield of the carbon material used was poor, and a lot of time was wasted in the cutting process.

A molding method using injection molding may be considered as a solution to the above problem. By the way, injection molding has traditionally been used to make plastic decks, ceramics, etc. In this case, the normal process is to add resin as a molding binder to the raw materials and knead them, then injection mold, then degrease, sinter, and precision I have been processing it. In particular, since a thermoplastic resin is used as a molding binder, a degreasing process is essential, and a lot of time is spent on this process.

In addition to using carbonaceous mesophase small spheres as a raw material, conventional methods for manufacturing carbon materials include using coke as a raw material, adding pitch to it, molding it with a mold or rubber, and then repeating the firing and pitch impregnation steps. It is publicly known. However, when this material is injection molded, since the injection molding is uniaxial molding, the resulting carbon material not only exhibits anisotropy, but also requires complicated steps of repeated impregnation and firing during the manufacturing process.

<Problem to be solved by the invention> What is the purpose of the invention? j! When manufacturing isotropic high-density, high-strength carbon materials with rough shapes, there is a cost-effective manufacturing method that can reduce product processing steps and improve product yield! The purpose is to come up with a plan.

Another object of the present invention is to provide a carbon material raw material that can be used directly in the manufacturing method.

<Means for Solving the Problems> The present invention is characterized in that carbonaceous mesophase small spheres having self-sintering properties are mixed with a pitch-based binder, then injection molded, and then subjected to firing and graphitization treatment. This is a method for producing an isotropic high-density, high-strength carbon material, in which the raw material for injection molding is carbonaceous mesophase spherules having self-sintering properties, and a pinch of 25°C with a Europeanization point of 200°C or less. A mixture of up to 75% by weight is preferred.

<Function> The carbonaceous mesophase spherules having self-sintering properties used in the present invention are those in which a caking component is retained on the surface of the mesophase spherules, as shown in Japanese Patent Publication No. 60-25364, for example. It is a raw material powder for carbon materials that can be molded, fired, and graphitized without using a binder.

In the molding of the small spheres of the present invention, injection molding is performed using a pitch having a softening point of preferably 200° C. or less, more preferably 100'C or less as a binder, and the molded object obtained thereby is similar to the small spheres. High-density and high-strength carbon materials can be easily obtained without repeating firing and impregnation. In addition, although the individual particles of the small spheres exhibit anisotropy, since they are arranged randomly during molding, it is easy to obtain an isotropic material as a whole.Furthermore, since the small spheres are spherical, in injection molding, a -layer It has the effect of improving fluidity. In order to make better use of these effects, it is desirable that the average particle diameter of the small spheres be 1μ or more and 30/7m or less.

In the present invention, as a molding binder, the softening point is preferably 200°C or lower, and preferably 100°C from the viewpoint of handling.
It is desirable to use the following coal-based or Ishibari-based pitch, and it is further desirable that the residual coal percentage at 800° C. be at least 40%. By using these pitches with a high residual carbon content and good affinity with the small spheres as a molding binder, the degreasing process that was necessary after molding can be omitted.
It has become possible to easily produce a high-density, high-strength carbon material by directly firing and graphitizing the compact.

Here, the pitch used as the binder is preferably 25% by weight or more and 75% by weight or less based on the small spheres. 25
If it is less than 75% by weight, the fluidity during injection molding will be poor, and if it is more than 75% by weight, there will be too much volatile content during firing, making it impossible to obtain a good carbon material.

Furthermore, compared to the conventional method of cutting the product shape from the block by cutting, the present invention uses injection molding, which not only improves the product yield for raw material powder but also significantly reduces the processing steps. It becomes possible to supply products at a cost advantage. In addition, although it was possible to manufacture simple shapes such as crucibles by cold isostatic pressure (CIP) molding using rubber, the injection molding of the present invention can also be used to mold more complex shapes, which was previously difficult. It became possible.

<Examples> Example 1 Coal tar pitch was heat-treated at 450°C to generate meso-phase spherules, which were extracted and filtered using 6 times the volume of oil in tar, and further calcined at 360°C for 3 hours. Mesophase spherules with an average particle size of 15 μm were obtained. The mesophase small spheres were given a softening point of 80°C by the ring ball method.
, FC (fixed carbon) 50%.

Coal cool pitch containing 16% Bl (benzene insoluble content) and 4% Ql (quinoline soluble content) was mixed at the blending ratio shown in Table 1, and was heated to 30 x 100 x with a hydraulic pressure of 600 kg/ca.
It was injection molded into a 100 m plate at 110°C. 1 molded body
After treatment at 000''C for 3 hours, a fired body was obtained by further treatment at 2500°C for 2 hours.Table 1 shows the physical property values of the obtained carbon material.

Example 2 Mesophase small spheres having the same self-sintering properties as in Example 1 had a softening point of 90"C, FC5 by the ring ball method.
Pitch of 5%, BI of 30%, and QI of 9% were mixed at the compounding ratio shown in Table 1, injection molded in the same manner as in Example 1, and then heat treated to obtain a fired body. Table 1 shows the physical property values of the obtained carbon material.

In addition, the measurement of each physical property value was performed on the fired body at 10 x 10 x
The zero bending strength was measured by cutting a 50m5+ sample using a compression testing machine, setting the distance between the supports to 40, and applying a load directly to the button at a uniform speed of 5 kgf per second to the center of the test piece, and calculating the maximum load at the time of failure. For strength calculation, JIS
The formula of R7202 was used. Is electrical resistivity JISI? 72
The hardness was measured by the voltage drop method described in 02 using a Schzier hardness meter.

<Effects of the Invention> As described above, according to the present invention, an isotropic high-density, high-strength carbon material can be obtained with a simple process that requires few processing steps and is advantageous in terms of cost, and can be used in crucibles, nozzles, sealing materials, etc. This opens up a wide range of uses for carbon materials that require complicated processing, and has great industrial benefits.

Claims (1)

[Claims] 1. Highly isotropic, carbonaceous mesophase small spheres having self-sintering properties are mixed with a pitch-based binder, then injection molded, and then fired and graphitized. A method for producing a high-density, high-strength carbon material. 2. A carbon material raw material for injection molding, characterized in that 25 to 75% by weight of pitch having a softening point of 200° C. or lower is mixed with carbonaceous mesophase small spheres having self-sintering properties.