JPS5913613A - Manufacture of carbonaceous material of high density and low elasticity - Google Patents

Abstract

PURPOSE:To obtain easily a high density carbonaceous material with low elasticity by adding a material formed by expanding natural graphite granules to a mixture of a carbonaceous material with a binder, kneading them, and molding and calcining the kneaded material. CONSTITUTION:To a mixture of a carbonaceous material with a binder is added about 1-30wt% expanded graphite formed by expanding natural graphite granules by immersion in a strong oxidizing soln. or other method. They are kneaded, and the kneaded materialis molded, calcined, and optionally graphitized to obtain a molded body of a carbonaceous material or a graphitic material. By this method a high density carbonaceous material with low elasticity suitable for use as a sealing material, an electric brush, etc. is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a molded body of carbon material or graphite material, and an object thereof is to provide a molded body of carbon material or graphite material that has high density and low elasticity. It is in.

Conventionally, molded bodies of carbon or graphite materials are made by adding a binder such as coal tar, coal tar pitch, or synthetic resin to a carbon material such as petroleum coke, stone coke, pitch coke, or carbon black, and then kneading, molding, and baking the mixture. It is then produced by graphitizing it if necessary. In order to obtain a molded body of a high-density carbon material or graphite material by the above method, for example, the following methods +11 to (4) are employed.

(Increase the molding pressure in the 11 molding process.

(2) Increasing the processing temperature in the firing and graphitization process,
Increase processing time.

(3) Use carbon material with fine particles.

(4) Add natural graphite powder to the carbon material.

According to the above method, a highly densified carbon material or graphite material molded body can be obtained, but the elastic modulus of the molded body also tends to increase. When a carbon material or graphite material molded body is used for sealing materials such as packing, gaskets, valve seats, electric brushes, etc., the molded body is required to have high density and low elasticity. However, with conventionally known methods, it is impossible to obtain a carbon or graphite material molded body that satisfies both physical properties of high density and low elasticity. Therefore, at present, molded bodies of carbon or graphite materials that are insufficient in one or both of these physical properties are intentionally used for the above-mentioned purposes.

In view of the current situation, the present inventor has conducted extensive research in order to develop a method for producing molded bodies of carbon or graphite materials that have both high density and low elasticity, and have finally completed the present invention. Ta.

That is, the present invention involves adding a mixture of a carbon material and a binder and expanded graphite obtained by subjecting natural graphite particles to an expansion treatment, self-kneading, molding and firing, and further graphitizing as necessary. The present invention relates to a method for producing a characterized carbon material or graphite material molded article.

According to the method of the present invention, it is possible to produce a molded body of carbon or graphite material that has high density and low elasticity at the same time. Moreover, the method is extremely simple and does not require advanced technology. The molded product obtained by the method of the present invention can be used in fields where carbon material or graphite material molded products are required to have high density and low elasticity, such as sealing materials such as packings, gaskets, and valve seats, and electrical appliances. It can be suitably used in fields such as brushes.

As the carbon material used in the present invention, a wide variety of conventionally known carbon materials can be used, such as petroleum coke, pinch coke,
Examples include carbon black. These carbon materials are preferably in the form of fine powder with an average diameter of 200 to 825 meshes (Tyler).

Furthermore, as the binder used in the present invention, a wide variety of conventionally known binders can be used, such as coal tar, coal tar pitch, synthetic resins, and the like.

According to the present invention, the ratio of the carbon material and the binder to be used is not particularly limited and can be appropriately selected from a wide range, but it is usually about 25 to 50% by weight of the latter to the former. good. If the amount of binder used is less than 25% by weight, the bond between aggregate particles will be weak and the mechanical strength will tend to decrease. On the other hand, if the amount of binder used is more than 50% by weight, the molded product will not be formed during firing. This results in softening and deformation of the bonding material, and also tends to become porous due to the large amount of gas generated from the bonding material.

In the present invention, expanded graphite obtained by subjecting natural graphite particles to an expansion treatment is added to the mixture of the carbon material and the binder.

The expanded graphite is produced, for example, by immersing natural graphite particles in a strongly oxidizing solution, washing with water, and then heating the graphite particles. As the natural graphite particles used here, a wide variety of conventionally known ones can be used, and examples thereof include flaky graphite, earthy graphite, and the like. Strongly oxidizing solutions include, for example, oleum, concentrated sulfuric acid, nitric acid, fuming nitric acid, concentrated nitric acid, a mixture of concentrated sulfuric acid and concentrated nitric acid, a mixture of concentrated nitric acid and nitric acid, concentrated sulfuric acid and hydrogen peroxide, and perchloric acid. Examples include a mixture with an oxidizing agent such as manganese dioxide (the content of the oxidizing agent is usually Iy-50 Ho-5). The amount of the strongly oxidizing solution to be used is not particularly limited and can be appropriately selected within a wide range, but it is sufficient that the natural graphite particles to be treated can be sufficiently immersed in the strongly oxidizing solution. Usually, the amount of strong oxidizing solution used is about 8 to 80 times, preferably 5 to 20 times, the amount of the natural graphite particles by weight. The subsequent washing with water is carried out at a heating temperature that is aimed at partially hydrolyzing the graphite J-intercompounds to elute the reactants, and trapping the remainder within the graphite interlayers as a material necessary for expansion. Although not particularly limited, generally 200℃ or higher, usually 2oo to 14℃
oo°C, preferably within the range of 800-1100°C.

Further, although the heating time varies depending on the heating temperature and the like and cannot be generalized, it is usually about 2 to 60 seconds. Furthermore, in the present invention,
Instead of immersing natural graphite particles in a strongly oxidizing solution, the graphite particles may be immersed in dilute nitric acid for electrolytic treatment. In this way, expanded graphite in which natural graphite particles are expanded approximately 20 to 400 times is produced. The amount of expanded graphite to be added is not particularly limited and can be appropriately selected within a wide range, but it is usually about 1 to 100% for the total amount of carbon material and binder.
It is preferable to add 80% by weight, preferably 5 to 20% by weight. When the amount of expanded graphite added is less than 11% by weight, the effect of addition on the elastic modulus tends to be small, and when it is more than 80% by weight, the mechanical strength tends to decrease significantly.

In producing the high-density, low-modulus carbon material of the present invention, conventional techniques can be applied as they are to cross-wire, molding, firing, and graphitization. The mixing can be carried out using a conventional kneading machine such as a kneader or roller. Further, when performing molding, any conventionally known molding method such as die pressing, extrusion molding, rubber press molding, etc. can be employed. For example, stamp molding or extrusion molding can yield a molded product with anisotropic crystal orientation, while rubber press molding can yield a molded product with isotropic crystal orientation. The pressure during molding is not particularly limited, but a surface pressure of 500 to 1500 Kg/am2 is usually sufficient. Firing is usually 700-1200°C, preferably 900-1100°C.
It is preferable to carry out the firing at a temperature of about C, and the firing time is generally about 40 to 80 hours, including the time for raising the temperature from room temperature. Graphitization is usually carried out at a temperature of 2000 to 3000°C, preferably 2500°C.
It is best to carry out the process at a temperature of ~2900°C, and the time required for graphitization is generally 20 to 40°C, including the time required to raise the temperature from room temperature.
It is 0 hours. In this way, a desired carbon material or graphite material molded body can be obtained.

Reference examples and examples are listed below.

Reference example Natural flaky graphite with an average diameter of 150 μm was dissolved in concentrated sulfuric acid (97 degrees
(weight% or more): Concentrated nitric acid (concentration 60% or more by weight) -9:l
The sample was immersed in a mixed acid having a volume ratio of (10 times the amount by weight) at a temperature of 100° C. for 10 minutes while stirring with a glass rod. Thereafter, it was heated in an electric furnace to a temperature of 1000° C. for 60 seconds to expand its volume by 200 times. Expanded graphite was thus obtained.

Example Petroleum coke with an average diameter of 10 μm and coal tar pitch were mixed and ground at a ratio of 1:1 (by weight) for 8 hours while heating to 200° C. to give a particle size of 115 μm or less.

To 100 parts by weight of this pulverized material, 1 to 30 parts by weight of expanded graphite having an average diameter of 200 μm and several lengths were added, and the mixture was mixed for 30 minutes using a ■ type mixing machine.

tl) Manufacture of anisotropic molded product The above mixture was placed in an embossing type mold, and a surface pressure of 1000 was applied.
Pressure molded from two opposing sides for 60 seconds at Kg/cm2,
A carbon material molded body was created by firing at 1000°C. The physical properties of the obtained molded product are shown in Table 1 below. Further, the graphite material molded body was prepared by heat-treating the above-mentioned carbon material molded body in an electric furnace at a maximum temperature of 2700° C. for 120 hours of current application. The physical properties of the obtained molded product are shown in Table 2 below.

(2) Manufacture of isotropic molded product The above mixture was placed in a rubber press device, and a surface pressure of 1000 was applied.
It was pressure-molded for 60 minutes at 2 Kg/Boron and fired at 1000°C to create a carbon material molded body. The physical properties of the obtained molded body are shown in Table 8 below.
It was created by heat treatment for 120 hours per current application time. The physical properties of the resulting molded product are shown in Table 4 below.Table 3 Table 4The following can be seen from the above examples. In other words, in embossing molding, as the amount of expanded graphite added increases, the anisotropy of electrical resistivity and thermal expansion coefficient increases, which means that the packing of petroleum coke particles becomes more dense. It shows that it is heading towards. Furthermore, as the amount of expanded graphite added increases, the apparent specific gravity increases, which means that the pore volume becomes smaller, indicating that the density is increasing. Furthermore, as the amount of expanded graphite added increases, the elastic modulus decreases. A similar tendency is shown in the case of rubber press molding.

[Brief explanation of the drawing]

Figures 1 to 8 show pore effort curves for the anisotropic graphite material molded bodies obtained in the above examples. FIG. 1, FIG. 2, and FIG. 8 show the results when the amount of expanded graphite added was 0%, 10%, and 80%, respectively. In the figure, D is the pore diameter, and ■ is the pore volume. (Above) Diagram 1 h3D (p) Diameter of electric hole 2 Diagram Technique D

Claims (1)

[Claims] ■ A carbon material characterized by adding expanded graphite obtained by subjecting natural graphite particles to an expansion treatment to a mixture of a carbon material and a binder, kneading, molding and firing, and further graphitizing if necessary. Or a method for producing a graphite material molded body.