JPS61218687A - Production of pitch for impregnation of high-density carbon material - Google Patents

Abstract

PURPOSE:A pitch containing a trace amount of the fraction insoluble in quinoline is heat-treated to increase the content of the quinoline-insoluble fraction up to a specific level whereby the titled pitch for impregnation is obtained by improvement in impregnating properties. CONSTITUTION:Impregnation pitch containing a trace amount, e.g. 0.01-0.03% of quinoline-insoluble fraction is heat-treated in a polymerization tank 15 to effect polymerization to obtain pitch 17 containing 0.1-1.0%, preferably 0.1-0.5% of quinoline-insoluble fraction. Impregnation into a carbon material of higher than 1.7 bulk density is remarkably improved to produce high-density carbon material of high quality, namely densified from the surface to the core part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing an impregnated pitch for a high-density carbon material (having a bulk density of 1.7 or more) that has excellent impregnating properties.

BACKGROUND OF THE INVENTION A general method for manufacturing a carbon material 1, such as an artificial graphite electrode for an electric furnace, is as follows. That is, first, aggregate coke and binder pitch are kneaded and molded to form a green electrode, and the green electrode is fired. During this firing process, the low molecular weight components in the binder pitch vaporize, making the electrode extremely porous and, if graphitized as it is, an electrode with poor mechanical strength and electrical resistance will be produced. .

Therefore, an impregnation step is performed in which the pores are impregnated with pitch to increase the bulk specific gravity. The impregnated electrode thus obtained is further fired, and the low molecular weight components of the impregnated pitch are vaporized and become porous again with many pores.

As this impregnation and firing process is repeated, the pores gradually decrease, creating a dense electrode.

Generally, this impregnation and firing process is repeated one to three times until a sufficiently dense electrode is obtained. This sufficiently dense electrode is further graphitized at high temperatures to produce a product electrode. The product electrode is best if it is dense, has high mechanical strength, high spalling resistance, and low electrical resistance.

One of the major factors that determines the compactness, mechanical strength, spalling resistance, and electrical resistance of a product electrode is the impregnation and firing steps in the electrode manufacturing process mentioned above. , various properties of the product electrode are also improved.

A major factor in determining the bulk density after impregnation and firing in Section L is the properties of the impregnated pitch used in this impregnation step.

That is, by using an impregnated pitch that impregnates the pores of the electrode quickly, impregnates even the minute pores, and has a high carbonization yield during firing, it becomes possible to manufacture a high-quality electrode. Furthermore, if such high-quality impregnated pitch is used, the time required for the impregnation process can be shortened due to the high impregnation rate.

In addition, if even minute pores are impregnated and the carbonization yield during firing is high, it is possible to reduce the number of impregnation-firing cycles required to reach a predetermined bulk density of the electrode.

Conventionally, the impregnating pitch used in this impregnation process has usually contained about 5 to 20% of quinoline insoluble matter. However, it has been known that the quinoline insoluble content in this pitch limits its impregnating properties.

Therefore, recently, the impregnated pitch manufacturing method disclosed in Japanese Patent Application Laid-open No. 53-147694, or the centrifugation method (Japanese Patent Application No. 59-141884) by the present applicant, has been developed to produce pitch in which the insoluble quinoline content is reduced to a melon trace amount. has come to be used. However, such pitch shows good impregnating properties for carbon materials with a bulk density of less than 1.7;
As described above, it was found that the impregnating property for harmful carbon materials was insufficient.

As a result, in the high-density carbon material manufacturing process, it is impossible to reduce the number of impregnation and firing cycles, as well as shorten the impregnation time, which causes high manufacturing costs for high-density carbon materials. It was also found that this was the cause of the manufacturing of non-uniform products with different densities on the surface and inside of the carbon material.

Problems to be Solved by the Invention As a result of intensive studies to solve the above problems, the present inventor clarified the influence of the amount of solid components in the impregnated pitch on the impregnation rate and saturated impregnation amount. In other words, the conventional theory that the smaller the amount of quinoline insoluble matter in the pitch, the better the compatibility is broken, and for high-density carbon materials with a bulk density of 1.7 or more, it is better to have an appropriate amount of particles of an appropriate size. It was discovered that the impregnating properties were dramatically improved.

That is, Figure 1 shows the relationship between the amount of solid particles of 0.5μ to 50g in pitch and the impregnating property, and the impregnating property of pitch containing 0.1% to 1% of solid particles is the best. I found that. The experimental conditions shown in FIG. 1 are as shown in Table 1.

The reason why the impregnability is improved when the pitch shown in Table 1 contains the above solid components is not clear, but it is thought to be as follows. Coal tar and pitches are often said to be mixtures of several thousand hydrocarbons and carbons, among which solid particles with a size of about 0.1 l or more are called quinoline insoluble matter. . Particles smaller than 0.1 square are also included in pitch, but current separation technology (Japanese Unexamined Patent Publication No. 147894/1983, Japanese Patent Application No. 141884/1984) removes these particles smaller than 061 square to trace amounts. As shown schematically in Figure 2, the particles (3) of 081 or less particles in the pitch from which trace amounts of quinoline insoluble matter have been removed convert the pitch into a carbon material (1). When impregnating, the fine pores of the carbon material (2)
This causes the impregnation rate and saturation impregnation rate to decrease.

Furthermore, when a large amount of solid particles called +Norin insoluble matter is contained in a large amount of 5% or more, as in conventional pitch, a thick layer of solid particles that do not impregnate the pores is formed.

The impregnation resistance increases and the impregnation rate also decreases.

However, if 0.1% to 1% of solid particles of 0.5 JL to 50 JL are present in the pitch, it is assumed that these solid particles move (move) of the filter aid used during filtration. That is, as shown in Figure fjS3, in filtration, by adding solid particles of an appropriate particle size to the stock solution (5) as a filter aid (4), fine particles that cause clogging of the filter medium (6) can be removed. (7) is removed in advance by the cake portion (8) of the filter aid (4).This makes it possible to perform filtration in a short time without clogging the i material (8). In FIG. 3, (11) is a filter tank;
(12) represents a filter medium support, and (13) represents a filtrate.

0.1% to 1% present in pitch, 5p, ~50
Solid particles of IL are also believed to play the role of filter aids in filtration. That is, as shown in FIG. 4, the solid particles in the pitch form a thin layer (9) on the surface (1) of the carbon material, causing clogging of the pores (2) of the carbon material (1). It is thought that because the fine particles (10) were removed in advance, the impregnation rate was fast and the saturation impregnation rate was high.

Most of the quinoline insoluble content in the pitch is 0.5~
In practice, the amount of quinoline insolubles in the pitch may be equal to the amount of 0.5 g solid particles in the pitch.

The present invention has been made based on the above-mentioned new findings, and provides a method for producing impregnated pitch for high-density carbon materials with excellent impregnating properties.

Means for Solving the Problems The gist of the present invention is to heat-treat pitch for impregnation with a quinoline insoluble content of less than 0.1% to produce a quinoline insoluble content, and to produce a quinoline insoluble content of 0.1-1.0%. %, preferably 0.1-0
Bulk density 1 characterized by having pitch for impregnation of ゜5%
．． A method for producing a pitch for impregnating a high density carbon material of 7 or more.

In the production method of the present invention, the pitch used as a raw material contains a trace amount of quinoline insoluble matter, more specifically, the pitch containing a trace amount of quinoline insoluble matter, for example, 0.01 to 0.03%, is 1. For example, it can be manufactured by the impregnated pitch manufacturing method disclosed in Japanese Patent Application Laid-Open No. 53-147894 or the centrifugation method proposed by the present applicant (Japanese Patent Application No. 511-1411384).

In addition, the quinoline insoluble content in the pitch produced by the method of the present invention is reduced to 0.
．． The reason why it is preferable to set it to 1 to 0.5% is as follows.

The pitch impregnating property for carbon materials with a bulk density of 1°7 or more is:
In the range of 0.61% to 1.0%, the quinoline insoluble content is approximately the same, and in the method of the present invention, the quinoline insoluble content is reduced to a melon trace amount, for example, 0.0%. By heat-treating pitch with an O content of 1 to 0.03%, a polymerization reaction is caused to produce quinoline insoluble content, and the target quinoline insoluble content in the pitch is 0.
．． 1-0.5% is better.

This is because the amount produced is smaller than 0.5 to 1.0%, and pitch with excellent impregnation properties can be obtained at low heat treatment costs and high productivity, that is, at low cost.

The present invention will be explained in detail below. FIG. 5 shows an example of the manufacturing process of the present invention, and 14 indicates a trace amount of quinoline insoluble matter used as a raw material in this manufacturing process, for example, 0.01 to 0.0.
The impregnated pitch contains 3%, and 15 is a polymerization tank in which the impregnated pitch 14 is heat-treated and subjected to a polymerization reaction. 1B is a pitch heating device, and 17 is pitch impregnated with a quinoline insoluble content of 0.1 to 1.0%, which is produced as a result of heat treatment.

The polymerization tank 15 used in this manufacturing method is not special, but when performing heat treatment operations, it is generally difficult to control the quality of the product if there is a temperature distribution in the tank.
A stirring type tank is preferable, in which raw materials are continuously charged and products are taken out, and a stirring blade 18 is attached.

Next, regarding the heat treatment conditions, when the impregnated pitch 14 is heat treated, a polymerization reaction occurs and quinoline insoluble matter is produced as shown in FIG.

As mentioned above, impregnated pitch containing 0.1% to 1% of quinoline insoluble matter shows extremely good impregnating properties, so in the final method, the heat treatment temperature and heat treatment time are appropriately selected based on Figure 6. If you do this, the quinoline insoluble content will be 0.1%~
It becomes possible to produce 1% impregnated pitch. Also, as mentioned above, it is desirable that the heat treatment equipment be of a continuous type, so in this case,
The average residence time is used as the heat treatment time.

The present invention will be explained in detail below.

Example 1 The pitch for impregnation (conventional pitch (1)) shown in Table 2 was heat treated at 370°C for 12 hours. As a result, a pitch (invention pitch (I)) having properties shown in Table 3 was obtained.

Table 2: Conventional pitch (1) Table 3: Invention pitch (1) Example 2 The pitch for impregnation (conventional pitch (1)) shown in Table 2 was heat treated for 38G"0.80 minutes. Results.

A pitch (invention pitch (2)) having the properties shown in Table 4 was obtained.

Table 4 Invention Pitch (2) Impregnation properties of the above Invention Pitch (1), Invention Pitch (2), the above Conventional Pitch (1), and pitch with a quinoline insoluble content of 5% (Conventional Pitch (2)) is shown in Figure 7. The experimental conditions are as shown in Table 1.

Experimental results show that the pitch of the present invention has no drawbacks such as slow impregnation speed and low saturation impregnation rate of conventional pitch, and the impregnation rate increases dramatically, and furthermore, the saturation impregnation rate is 5% (the theoretical value). The porosity of the electrode was almost the same as the porosity of the electrode.

Furthermore, Figures 8 and 9.10111 show the impregnated states of conventional pitch (1), conventional pitch (2), present invention pitch (1), and present invention pitch (2) into the electrode after an impregnation time of 4 hours, respectively. FIG.

In Figure 8.9.1O111, the central part of the electrode used in the experiment was cut in the radial direction and the impregnation state was measured (the measurement method was the method proposed in Japanese Patent Application No. 103243/1983). indicates the area impregnated with pitch.

From these, it is clear that the pitch of the present invention is uniformly impregnated from the surface to the inside.

Effects of the Invention As detailed above, the present invention uses a simple method that only heat-treats conventional pitch containing trace amounts of quinoline insoluble matter, and improves the impregnation properties (impregnation rate, saturation rate, etc.) of conventional pitch into high-density carbon materials. impregnation rate) can be dramatically improved.

As a result, in the high-density carbon material manufacturing process, it is possible to reduce the number of impregnation and firing cycles and shorten the impregnation time, thereby reducing the manufacturing cost of the high-density carbon material.

In addition, a high-quality, high-density carbon material that is uniformly densified from the surface to the inside can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the amount of solid particles of 0.5p to 50l in pitch for impregnation and impregnating property, and Fig. 2.3.4 is an explanatory diagram of the mechanism for improving the impregnating property of pitch according to the present invention. Fig. 5 is an explanatory diagram of an example of the manufacturing process of the present invention, Fig. 6 is a diagram showing the relationship between heat treatment temperature and quinoline insoluble matter production rate, and Fig. 7 is an illustration of impregnation time to explain the impregnation characteristics of conventional pitch and pitch according to the method of the present invention. Figure 8.9.1O111 is a cross-sectional view of the impregnation situation. 1... Carbon material, 2... Pore, 3-... Particle, 4...
- Cancer support agent, 5...Standard solution, 6...Filtering medium, 7...Fine particles, 8.φΦcake part. 9. No. layer, lO...fine particles in pitch, 11...
Filtration tank, 12, Φ, filter support, 1311...filtrate, 1
4...Pitch with trace amount of quinoline insoluble matter, 15・Φ
e Polymerization tank, IB... Pitch heating device, 17... Pitch with quinoline insoluble content of 0.1 to 1.0%, 18... Stirring blade.

Claims (1)

[Claims] The pitch for impregnation with a quinoline insoluble content of less than 0.1% is heat-treated to produce a quinoline insoluble content, and the quinoline insoluble content is 0.1%.
A method for producing pitch for impregnation of a high-density carbon material having a bulk density of 1.7 or more, characterized in that the pitch for impregnation is 1 to 1.0%.