JPS59152989A - Preparation of impregnating material - Google Patents

Abstract

PURPOSE:To obtain an impregnating material for parent materials such as graphite electrode, high-density carbon material, refractory, etc., by distilling away a crystalline oil component from a coaly heavy oil to give concentrated pitch having a small amount of quinoline-insoluble substance, blending the pitch with a specific noncrystalline aromatic oil component. CONSTITUTION:(A) Concentrated pitch having a small amount of quinoline-insoluble substance obtained by distilling away a crystalline oil component having <=500 deg.C boiling point from a coaly heavy oil such as coal tar, etc. is blended with (B) usually 5-40wt% noncrystalline aromatic oil component (preferable example, naphthalene oil freed from crystal, anthracene oil freed from crystal, creosote oil) having <=20 deg.C freezing point, >=200 deg.C boiling point, and H/C=0.7- 1.3, to give the desired impregnating agent. EFFECT:Having a large amount of fixed carbon, low softening point, improved flow properties and wetting properties, and good heat stability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an impregnating material for a base material such as a graphite electrode, a high-density carbon material, or a refractory material.

Base materials such as graphite electrodes, high-density carbon materials, and refractories themselves have some pores, so by impregnating these base materials with an impregnating agent, performance can be improved depending on the application. The main properties required for O-impregnated materials are as follows.

(a) There is a lot of fixed carbon.

Graphite electrodes, high-density carbon materials, refractories, etc. are usually used at high temperatures of 1000°C or higher, so the more the impregnated material remains in the base material as fixed carbon even after carbonization at 1000°C or higher, the
The generation of pores is small, preventing the bulk density of the base material from decreasing and protecting the base material.

(b) Low softening point, good fluidity and wettability.

Impregnation work is usually carried out by immersing the base material in molten impregnating material, reducing the pressure to remove air in the pores of the base material, and then applying pressure to promote the infiltration of the impregnating material into the base material. edge,
The lower the softening point and the better the fluidity and wettability of the impregnating material, the easier it can penetrate into the pores, the faster the impregnation rate, and the lower the impregnation temperature.

(c) The quinoline soluble content (hereinafter abbreviated as QI) is low.

QI refers to polymers with a molecular weight of 5,000 or more, spherulites produced by the orientation of polymer components, or a few μm in diameter such as soot.
carbonaceous matter, ash of silica, alumina, etc.
If there are too many of these impurities, impregnation into the pores of the base material will be inhibited,
The lower the QI, the better since it causes a decrease in the impregnation rate.

(d) Good thermal stability.

Since the impregnating material is used for a long period of time in a heated molten state at 200 to 300°C, the softening point increases, the fluidity decreases, and the Q
It is necessary to have good thermal stability without causing thermal alteration such as generation of I.

Various methods have been studied to produce impregnating materials that satisfy the properties (a) to (d) above. The following four methods are mainly used for this purpose.

(1) Polymerization method using air oxidation 0 (2) Polymerization method using addition of a polymerization accelerator or heat treatment.

(3) A combination of (1) or (2) and a distillation method.

(4) A combination of (1) or (2) and the tar oil cut bank method.

Although the materials obtained by these methods exhibit excellent performance as binder pitches for electrodes, they have the following problems when used as impregnating materials.

Methods (1) and (2) increase the amount of fixed carbon, but the softening point increases significantly, resulting in a decrease in fluidity and wettability, and the generation of quinolinous components is significant, resulting in a decrease in the impregnation rate. This causes a decrease in the impregnability of the base material. Although methods (3) and (4) have been proposed to improve the problems of (1) and (2), they cannot be expected to have any effect on improving the quality of the impregnating agent.

The present inventors have developed pitch (
The relationship between softening point, amount of fixed carbon, and amount of QI generated was investigated in detail, and the results were as follows: (a) contains a large amount of fixed carbon, (b)
We have discovered a method for producing an impregnating material that satisfies all of the following quality conditions: low softening point, good fluidity and wettability, (C) low quinolinated content, and (d) good thermal stability.

That is, in the method of the present invention, coal-based heavy oil is used as a raw material, crystalline oil with a boiling point of 500°C or less is removed from it to obtain a concentrated pinch with a low quinolinous content, and this concentrated pitch and a solidified pitch with a freezing point of 20°C are obtained. Below, when the boiling point is 200℃ or higher, H/c-0
7 to 1.3 of a non-crystalline aromatic oil.

The method of the present invention will be explained in more detail below.

In obtaining concentrated pitch, coal-based heavy oil is used as a raw material.Coal-based heavy oil includes coal tars such as high-temperature tar and low-temperature tar that are produced as by-products during coal carbonization, i! Heavy components of bamboo coal liquefaction products and those from which QI has been removed by filtration or centrifugation are used. This type of coal-based heavy oil is rich in aromatic properties and contains a large amount of compounds with good crystallinity such as anthracene (boiling point 342°C), pyrene (boiling point 404°C), benzpyrene (boiling point 480°C), etc. These crystalline oils do not become the fixed carbon component of pitch, and are solid at room temperature, raising the softening point of pitch and strongly reducing fluidity, making it unsuitable for use as an impregnating material. oTherefore, it is necessary to remove the crystalline oil.This point will be explained with reference to Figure 1.The figure shows the following:
This graph shows the relationship between the softening point and fixed carbon when pitch is produced using coal tar as a raw material. ), the increase in the softening point is smaller than in the case of the conventional polymerization method (line C).

For removing and concentrating crystalline oil with a boiling point of 500° C. or lower from coal-based heavy oil, methods such as vacuum distillation or steam distillation at a heating temperature of 400° C. or lower, or solvent extraction can be employed. In the case of concentration treatment that involves heating, the heating temperature should be 400°C or less, in order to prevent the occurrence of QI due to heat treatment during concentration treatment.0 In order to increase the fixed carbon of the impregnating material, concentration It is effective to raise the softening point of concentrated pitch, but considering the need to ensure the necessary quality and economic efficiency, the softening point of concentrated pitch is 130 to 20.
It is desirable to adjust the temperature to 0°C.

It is desirable for concentrated pitch to have a QI of 5 parts by weight or less. This is because if the QI is large, the impregnating property will be reduced as described above. In order to reduce the QI to less than 5% by weight, it is necessary to remove the QI acid component before the concentration process, or to prevent QI from occurring during the concentration process as described above.
-Condensation is carried out at a heating temperature below 0° C. (in the absence of oxygen).

Usually, the QI amount of the impregnating material obtained by concentrating coal tar by the method of the present invention and mixing it with amorphous oil is 5% or less.

Adjustment of the softening point of the concentrated pitch is also an important factor. For this purpose, a non-crystalline aromatic oil component, which will be described later, is mixed with the concentrated pitch. By this mixing, as shown by line D in Figure 1, it is possible to adjust the softening point without significantly lowering fixed carbon compared to the conventional tar oil cutback method (line D). If the method of the present invention is followed, the QI will also be concentrated as the coal-based heavy oil is concentrated, and the amount will apparently increase (line E in Figure 2). If the oil has no QI, no QI will occur in the concentrated pitch (
In the conventional method (oxidation heat treatment method, line G in Figure 2), the amorphous aromatic oil mixed with the concentrated pitch has a freezing point of 20°C or less, and H/c = 0.7-13
The boiling point is required to be 200° C. or higher, and examples that meet this condition include decrystallized naphthalene oil, decrystallized anthracene oil, creosote oil, cleaning oil, and petroleum-based pyrolysis oil.

The reason why the freezing point is required to be 20° C. or lower is that the amorphous oil, which is liquid at room temperature, is effective as a softening point regulator.

If the I [ratio exceeds 1.3, the miscibility with the concentrated pitch will be poor, and the polymer components in the pitch will separate as insoluble matter, making it impossible to produce a uniform pitch. On the other hand, if the ratio is less than 0. As the crystallinity of the oil increases, the amount of oil mixed to adjust the softening point increases, resulting in a decrease in the amount of fixed carbon. When used for a long time, the softening point increases, making it unsuitable for use as an impregnating material.

On the other hand, the amount of aromatic oil mixed with the concentrated pitch is generally preferably 5 to 40% by weight, but in order to adjust the softening point to the required level, the amount of amorphous aromatic oil mixed is It is only necessary to select one, and there is no particular limitation.

In the method of the present invention, since air oxidation or polymerization accelerator is basically added, at an impregnation temperature of 200 to 300°C,
Even if it is kept for several tens of days, there is no decrease in fluidity and it has excellent thermal stability.

By the way, when removing crystalline oil, boiling point 5
The reason for limiting the temperature to 00°C or lower is that if oil with a boiling point exceeding 500°C is to be removed, a high vacuum will be required if a distillation method is used, which is disadvantageous from an industrial economic standpoint. Furthermore, if oils with a boiling point exceeding 500°C are removed, the softening point of the pitch will rise too much and the addition rate of amorphous aromatic oil will increase, resulting in increased costs.Furthermore, this will lead to a decrease in pitch yield. This is because the effects of the present invention can be obtained by removing oil with a boiling point of 500° C. or lower.

In addition, the fixed carbon, softening point, and quinoline solubility in the present invention are measured based on JIS, -K 2425.

Examples and comparative examples of the present invention will be shown below.

(Example 1) Add 10 times the amount of toluene to coal tar,
After stirring at ℃ for 30 minutes, the toluene insoluble portion was recovered by centrifugation, and the toluene in the insoluble portion was removed using an evaporator to obtain a concentrated pitch with a softening point of 185℃. Add 30 parts by weight of creosote oil, which is liquid at room temperature with a boiling point of 270 to 320°C, and add 250 parts by weight.
The mixture was heated to ℃ and uniformly mixed. It is clear from Table 1 that the obtained impregnating material has a large amount of fixed carbon and a low QI amount, and is excellent as an impregnating material.

(Comparative Example 1) Low boiling point oil was removed from the coal tar of Example 1 by atmospheric distillation so that the softening point of the pitch would be 90°C. The obtained pitch had a low QI, but the fixed carbon content was significantly lower than that of Example 1.0 (Example 2) 100 parts by weight of quinoline was added to 10 parts by weight of coal tar, heated to 80°C and uniformly mixed. Dissolve and remove the quinolinine solution by centrifugation, then gradually heat to 350°C,
Quinoline and crystalline oil were removed by vacuum distillation to obtain concentrated pitch with a softening point of 140°C. For 100 parts by weight of this concentrated pitch, H/c = 0.76 boiling point 320-38
20 parts by weight of liquid decrystallized anthracene oil was added at room temperature of 0°C and heated to 200°C to uniformly mix. As shown in Table 1, the obtained pitch contained no quinoline solubles at all and had a high fixed carbon content.

(Comparative Example 2) Coal tar from which the quinoline solvent was removed by the method of Example 2 and the quinoline was further removed by atmospheric distillation was heated at 440°C for 80 minutes.
Heat for an hour, remove the oil that evaporates during this time, and soften the temperature to 8.
A pitch of 7°C was obtained. This pitch is 10 under a polarizing microscope.
The occurrence of anisotropic spherulites of about μm size was observed. As shown in Table 1, approximately 10 QIs occurred.

(Example 3) QI acid component was removed by centrifugation from the coal liquefaction product obtained by hydrogenating and extracting coal with a hydrogen-donating solvent (tetralin),
Next, it was heated to 380°C, and the hydrogen-donating solvent and crystalline oil with a boiling point of 400°C or lower were removed by steam distillation to obtain a concentrated pitch with a softening point of 166°C. To this concentrated pitch, 20 parts by weight of /c-097 ethylene pyrolysis bottom oil, which is liquid at room temperature with a boiling point of 300 to 400°C, is added to 100 parts by weight of the concentrated pitch, heated to 230°C, mixed uniformly, and softened to a softening point. An impregnated material at 80°C was obtained.

(Comparative Example 3) Coal liquefaction product 201 (9) from which QI was removed from Example 3 was heated at 420°C for 5 hours by blowing air at 1 l/min and distilled so that the softening point was 80°C. As is clear from Table 1, the amount of fixed carbon was reduced in Comparative Example 3, and the amount of quinoline solubles was 122%.

(11) Further, the pitch of Example 3 and the pitch of Comparative Example 3 were left at 250°C for 30 days, and changes in the softening point of the pitches were investigated. However, the softening point of the pitch of Comparative Example 3 increased by 19° C. It can be seen that the method of the present invention yields a pitch with excellent thermal stability.

Furthermore, the pitch of Example 2 and Comparative Example 2 was approximately 2
It was melted in an autoclave at 50°C, a test piece of graphite electrode was put there, the pressure was reduced to 10.0 +++ mI (g), and then the pressure was increased to 10 ~ with a compressor to perform the impregnation treatment. After impregnation, each piece was removed from the autoclave. A test piece of the graphite electrode was taken out, excess pitch was removed, and it was fired.

Table 2 shows the properties of the test piece after firing.

As is clear from Table 2, even if the fixed carbon content is the same, the material obtained by the method of the present invention that does not contain QI has a larger bulk specific gravity, a smaller total pore volume, a larger bending strength, and superior performance as an impregnating material. It can be seen that

(12) As shown in Table 1 and Table 2, according to the method of the present invention, impregnation with a large amount of fixed carbon, a low softening point, good fluidity and wettability, a small amount of quinoline solubles, and good thermal stability can be achieved. material can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are correlation diagrams for explaining the method of the present invention in comparison with the conventional method. Patent Applicant: Sumitomo Metal Industries, Ltd. Figure 1 Time Nine Friends% (%) Figure 2

Claims (1)

[Claims] (1) Made from coal-based heavy oil, with a boiling point of 500℃
The following crystalline oil components are removed to obtain a concentrated pitch with a small quinolinated content, and this concentrated pitch has a freezing point of 20°C or lower, a boiling point of 200°C or higher, and H/c = 0.7 to 1.3. 1. A method for producing an impregnating material, which comprises mixing a non-crystalline aromatic oil with a non-crystalline aromatic oil.