JPH0124724B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing high-density graphite material. (Prior art and its problems) High-density graphite materials are usually made by extrusion molding a mixture obtained by heating and kneading aggregates such as coke powder, graphite powder, and oil smoke with the addition of binders such as tar pitch, coal tar, and phenolic resin. Alternatively, the kneaded material is pulverized, the particle size is adjusted, and the molded powder is molded into a predetermined shape by means such as pressure molding or isostatic pressing to obtain a molded product, which is then heated in a firing furnace such as a Matsufuru furnace or a tunnel furnace.
Fire at 1000℃. This fired product is then impregnated with pitch and fired again. After performing this pitch impregnation and re-firing process a necessary number of times, a method is used in which the material is graphitized at a temperature of about 3000°C. This pitch impregnation work is
This method is expensive and takes a long time to produce high-density graphite material because it requires batch work, it is time-consuming to remove the pitch around the fired product after impregnation, and there is no need for a long process for re-firing. There were such problems. Therefore, recently HIP using calcined coke as raw material has been developed.
A manufacturing method using hot isostatic pressing (hot isostatic pressing) or using mesocarbon microbeads has been developed. However, the method using HIP requires the use of expensive equipment, and the method using mesocarbon microbeads requires high raw material costs due to the complicated manufacturing method of the microbeads, and requires the firing of large products. It had drawbacks such as being difficult and having a high defective rate. (Object of the Invention) An object of the present invention is to provide a method for producing a high-density graphite material that solves the above-mentioned problems. (Structure of the Invention) The present invention heat-treats a kneaded material obtained by heating and kneading aggregate and a binder and coarsely pulverizing the material to a maximum particle size of 10 μm or less at a temperature of 300 to 550°C, and then After pulverizing to 18 μm or more at least 1.05 times the particle size, molding,
The present invention relates to a method for producing a high-density graphite material, which is characterized by firing and graphitizing the material. The aggregate in the present invention is carbon material powder such as coke powder, graphite powder, oil smoke, etc., and the binding material is tar pitch, coal tar, etc. The average particle size of the aggregate is preferably 15 μm or less. If it exceeds 15 μm, the pore size in the structure becomes large, which is disadvantageous for achieving high density. It is preferable that the binding material has fixed carbon content of 35% by weight or more. If it is less than 35% by weight, a large amount of volatile matter is released, which is disadvantageous for achieving high density. The proportion of binder is preferably 25 to 60% by weight. If it is less than 25%, it is not sufficient to achieve high density, and if it exceeds 60%, kneading tends to be insufficient. The aggregate and binder are first thoroughly mixed using a V-type mixer or the like, or are thoroughly mixed during kneading. This mixture is kneaded using a double-armed mixer, a continuous mixer, etc., and the kneading temperature is set so that the kneaded product has an optimum viscosity. This kneading temperature is not particularly limited, but is generally 150 to 300℃.
It is. Kneading should be carried out sufficiently so that the aggregate and binder are uniform and the binder covers the aggregate well. Since the kneaded material obtained in this way is in the form of a lump, the maximum
It is necessary to coarsely grind to a particle size of mm or less. This is because if the kneaded material exceeds 10 mm, it will be difficult for the volatile matter to be removed during heat treatment, and the volatile matter will not be released uniformly between the inside and the surface. The kneaded material obtained in this way is heat-treated at a temperature of
Heat treatment is performed at 300-550℃. Heat treatment temperature is 300℃
Below, the release of volatiles is prolonged;
This is because if the temperature exceeds 550°C, the sintering properties of the kneaded material will almost disappear and the desired product will not be obtained. Heat treatment is possible even in an oxidizing atmosphere, but the treatment temperature is
If the temperature exceeds 350°C and the treatment time exceeds 40 minutes, oxidation will become significant and physical properties will deteriorate, so a non-oxidizing atmosphere is preferred. The heat treatment is preferably carried out so that the volatile content of the kneaded product is 5 to 20% by weight. This is because if the volatile content is less than 5%, the physical properties of the graphite material are insufficient, and if it exceeds 20%, blisters and cracks are likely to occur. The kneaded material after the heat treatment is pulverized by a pulverizer. Examples of the crusher include a ball mill, a vibrating ball mill, a jet mill, a turbo mill, a pin mill, etc., but are not particularly limited. The average particle size of the pulverized powder must be at least 1.05 times the aggregate particle size and 18 μm or less. If it is less than 1.05 times, the amount of binding material on the surface of the aggregate is insufficient, the binding strength decreases, and a high-density material cannot be obtained. Furthermore, if the average particle size of the pulverized powder exceeds 18 μm, the pore size in the structure becomes large and a high-density material cannot be obtained. This pulverized powder is molded into a predetermined shape by known means such as pressure molding or isostatic pressing to obtain a molded body, which is then fired by a known method in a firing furnace such as a Matsufuru furnace or a tunnel furnace, and further heated to 2500°C. Graphitization is performed at the above temperature, but these methods are not particularly limited. (Example) Next, an example will be described. Example 1 50 parts by weight of pitch coke powder with an average particle size of 3 μm,
50 parts by weight of tar pitch powder crushed to an average particle size of 35 μm was added and thoroughly mixed using a V-type mixer. This mixed powder was sufficiently kneaded using a double-armed milling machine while heating at a temperature of 200°C, and after cooling, it was coarsely ground to a maximum particle size of 4 mm or less. This was heated at 450° C. for 10 minutes in a nitrogen atmosphere to reduce the volatile content to 14% by weight. After coarsely pulverizing this kneaded material, it was pulverized in a ball mill until the average particle size became powder of 10 μm, and the molded product obtained by pressure molding was fired at about 1000°C in a non-oxidizing atmosphere, and graphite was heated at about 3000°C. It became. The physical properties at this time are shown in Table 1. Example 2 To 55 parts by weight of pitch coke powder having an average particle size of 3 μm, 45 parts by weight of tar pitch powder crushed to an average particle size of 35 μm was added and thoroughly mixed using a V-type mixer. This mixed powder was sufficiently kneaded while being heated at a temperature of 170° C. using a continuous milling machine, and after cooling, it was coarsely ground to a maximum particle size of 4 mm or less. This was done at 400℃ in a nitrogen atmosphere.
It was heated for 10 minutes to bring the volatile content to 16% by weight. After coarsely grinding this kneaded material, it was milled with a jet mill until the average particle size was 8 μm.
The molded body obtained by pressure molding is then sintered at approximately 1000℃ in a non-oxidizing atmosphere, resulting in approximately
Graphitization was performed at 3000℃. The physical properties at this time are shown in Table 1. Example 3 To 45 parts by weight of carbon black having an average particle size of 20 nm, 55 parts by weight of tar pitch powder crushed to an average particle size of 10 μm was added and thoroughly mixed using a V-type mixer. This mixed powder was thoroughly kneaded using a double-armed softener while heating at a temperature of 190°C, and after cooling, it was coarsely pulverized to obtain coarse particles with a maximum particle size of 4 mm or less. This is carried out in a nitrogen atmosphere.
It was heated at 450°C for 25 minutes to reduce the volatile content to 12% by weight.
This kneaded material was pulverized with a vibration mill until the average particle size was 6 μm, and the powder was pressure-molded to obtain a molded body, which was then fired at approximately 1000°C in a non-oxidizing atmosphere.
Graphitization was performed at 3000℃. The physical properties at this time are shown in Table 1. Comparative Example 1 35 parts by weight of ground tar pitch powder was added to 65 parts by weight of pitch coke powder with an average particle size of 25 μm, and V
Thoroughly mixed using a mold mixer. This mixed powder was kneaded for 3 hours while being heated at a temperature of 200° C. using a double-arm kneading machine. This kneaded material is pulverized and the average particle size is
It was set to 35 μm. The volatile content was 9%, and molding, firing, and graphitization were performed in the same manner as in Example 1. The physical properties are shown in Table 1. Comparative Example 1 The fired body obtained in Comparative Example 1 was impregnated with pitch, and after re-firing, it was graphitized in the same manner as in Example 1. Their physical properties are shown in Table 1. Example 4 40 parts by weight of tar pitch powder crushed to an average particle size of 35 μm was added to 60 parts by weight of pitch coke powder with an average particle size of 10 μm.
Parts by weight were added and thoroughly mixed using a mixer. This mixed powder is thoroughly kneaded while being heated at a temperature of 220°C using a continuous milling machine, and after cooling, it is coarsely pulverized to a maximum particle size of 4.
Coarse particles of less than mm were obtained. This was heated in the air at 350°C for 25 minutes to reduce the volatile content to 11% by weight. This kneaded material was ground with a vibration mill until the average particle size was 12 μm,
The pulverized powder was press-molded and then calcined at about 1000°C in a non-oxidizing atmosphere, and graphitized at a temperature of about 3000°C. Table 1 shows the values of the physical properties at this time.

[Table] As is clear from Table 1, the graphite materials of the examples have a larger bulk density and also have higher bending strength and shore hardness than the graphite materials of the comparative examples. (Effects of the Invention) According to the present invention, it is possible to economically obtain a high-density graphite material with excellent properties without pitch impregnation and without using expensive equipment. Effective for manufacturing graphite products such as electrodes for electrical discharge machining and nozzles for continuous casting.

Claims (1)

[Claims] 1. Aggregate and binder are heated and kneaded to obtain a maximum particle size of 10 mm.
The coarsely pulverized kneaded material is heat treated at a temperature of 300 to 550℃, and then the average particle size is 1.05 of the average particle size of the aggregate.
A method for producing high-density graphite material, which comprises pulverizing the material to 18 μm or less by at least twice as much, followed by shaping, firing, and graphitization. 2. The method for producing a high-density graphite material according to claim 1, wherein the aggregate has an average particle size of 15 μm or less. 3. The method for producing a high-density graphite material according to claim 1, wherein the heat treatment is a heat treatment to reduce the volatile content of the kneaded material to 5 to 20% by weight.