JP2000230178A - Production of mesophase microbeads - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing mesophase microbeads in high yield. SOLUTION: This method for producing mesophase microbeads comprises heat treatment of mixed pitch which is prepared by heat treatment of coal tar pitch to form mesophase microbeads which are then removed, followed by admixing the resultant residual pitch into coal tar pitch and preferably adjusting quinoline insolubles to 0.5-2 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing mesophase microspheres which can produce mesophase microspheres with a high yield.

[0002]

2. Description of the Related Art When heat treatment of coal tar pitch, 35
From 0 ° C. or higher, a mesophase microsphere exhibiting optical anisotropy is generated by the development of a carbon crystal structure in the pitch isotropic matrix and lamination. When the heat treatment is further advanced, the particles of the mesophase small sphere gradually grow, and the small spheres are united into a bulk to finally become coke.

[0003] The mesophase spheres formed in this process have excellent electrical properties and mechanical strength due to the development of a planar crystal structure of carbon, and utilize raw materials of various carbon materials and their electrical properties. It is used as a raw material for a negative electrode material of a lithium ion secondary battery. Various methods have been proposed for producing the mesophase microspheres. In general, coal tar pitch having a certain range of quinoline-insoluble matter (: QI) is selected as a raw material, and heat treatment is performed. Methods are known.

As the coal tar pitch, various types of coal tar pitch containing quinoline-insoluble components obtained by distilling coal tar collected from a coke oven have been used. Therefore, in the case of the conventional production method, it is necessary to select a raw material having a quinoline-insoluble content in a specific range as a coal tar pitch, and there is a restriction on the raw material source.

When producing mesophase microspheres having a uniform particle size from coal tar pitch, it is necessary to suppress the formation and bulking of the mesophase microspheres, and therefore it is necessary to reduce the incidence of mesophase microspheres. is there. Therefore, the yield of mesophase spherules based on the raw material pitch is as low as at most about 33 wt%, and improving the yield has been a major issue in industrial implementation.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method for producing mesophase spheres capable of producing mesophase spheres with a high yield.

[0007]

According to the present invention, a coal tar pitch is heat-treated, and the remaining pitch after removing the generated mesophase spherules is added to the coal tar pitch, mixed, and the mixed pitch is heat-treated. A method for producing mesophase microspheres, which comprises producing mesophase microspheres.

In the present invention, it is preferable that the quinoline insoluble content of the mixed pitch is adjusted to 0.5 to 2% by weight.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, a mixture of a coal tar pitch (hereinafter also referred to as a straight pitch) obtained by distillation of coal tar and a remaining pitch (unreacted component) after removing the mesophase globules is referred to as a mixed pitch.

The residual pitch may contain a solvent component used for separating and removing the mesophase spherules described later. The present inventors have conducted intensive studies to solve the above-described problems, and as a result, have found the following (1) and (2), and have accomplished the present invention. (1) Effective use of residual pitch (unreacted components) after removal of mesophase spherules: heat treatment of coal tar pitch (: straight pitch) obtained by distillation of coal tar to generate mesophase spherules, solvent extraction, etc. The mesophase microspheres can be produced in high yield by separating the mesophase microspheres, adding the collected residual pitch (unreacted component) to the straight pitch, mixing and heat-treating the mixed pitch. .

(2) Control of the amount of quinoline-insoluble matter (QI) in the mixed pitch: Controlling the amount of quinoline-insoluble matter (QI) in the mixed pitch to be within a specific range can be achieved by controlling the particle size distribution of mesophase microspheres. Is an important factor in controlling the characteristics of In the case of the conventional production method, in order to produce mesophase microspheres by heat-treating coal tar pitch having a wide range of molecular weight components derived from coal tar, only specific high molecular weight components undergo a polycondensation reaction by heat treatment to form mesophase. Therefore, if the heat treatment temperature is increased or the heat treatment time is lengthened in order to improve the yield, the growth and coalescence of the spheres are promoted, and the spheres are formed into a bulk, which further causes coking.

Thus, the yield of mesophase microspheres is 33
The limit was about wt%. According to the present invention, the mesophase microspheres are separated from the generated pitch, the mesophase microspheres are separated, and the remaining pitch removed is added to the raw material for heat treatment.
Since the amount of the mesophase precursor component in the raw material for heat treatment can be increased, mesophase microspheres can be selectively generated.

That is, according to the present invention, since the concentration of the high molecular weight component in the raw material for heat treatment is increased, the reactivity of the raw material for heat treatment is improved, and as a result, the yield of mesophase small spheres is improved. It is preferable to adjust the amount of the mesophase spherule-removing component (remaining pitch) so that the quinoline-insoluble matter (QI) in the mixed pitch is 0.5 to 2% by weight.

This is because, when the quinoline-insoluble content is as low as less than 0.5% by weight, the effect of inhibiting coalescence for selectively obtaining mesophase microspheres is reduced, and excessively grown mesophase microspheres are easily produced. The particle size distribution of the mesophase spheres is widened, making it difficult to obtain mesophase spheres having a uniform particle size distribution. Conversely, the quinoline insoluble content is 2% by weight.
This is because, when it exceeds, the generation and growth of mesophase microspheres are likely to be inhibited.

Therefore, adjusting the amount of quinoline-insoluble matter in the mixed pitch within the above range, preferably by adjusting the blending amount of the straight pitch and the remaining pitch, is an important factor in controlling the characteristics of the obtained mesophase microspheres. Become. In the present invention, coal tar pitch (straight pitch) is used as a raw material for heat treatment other than the mesophase small sphere removing component (residual pitch). In addition to the straight pitch and the residual pitch, petroleum pitch is added and blended. It is also possible.

As the straight pitch, it is preferable to use a pitch having a quinoline insoluble content of 1 to 5% by weight.
When the quinoline-insoluble content is less than 1% by weight, the amount of the remaining pitch is limited and the effect of improving the yield is reduced, and when it exceeds 5% by weight, the generation and growth of mesophase microspheres are inhibited.

The heat treatment temperature of the mixed pitch is 360 to
Preferably it is 480 ° C. The above heat treatment temperature is 360 ℃
When the temperature is less than 480 ° C., the rate of generation and growth of mesophase microspheres decreases, and the productivity decreases.
Mesophases grown in a bulk form are mixed, and it is difficult to selectively generate mesophase spheres.

The method for separating and removing the formed mesophase spheres is not particularly limited, but the straight pitch or the mixed pitch after the heat treatment is extracted with a solvent, and the liquid after the solvent extraction is solidified by filtration, centrifugation or the like. Liquid separation is preferred. In addition, as the solvent used for the above-mentioned solvent extraction, coal tar medium oil, coal tar light oil, aromatic solvent, or a mixed oil thereof can be used, and the mesophase small spheres are not dissolved, and the remaining pitch (in the pitch) The type of the solvent is not limited as long as it is a solvent having excellent extraction power of the unreacted component).

[0019]

EXAMPLES The present invention will be described below more specifically based on examples. The quinoline-insoluble matter in this example
(QI) amount (hereinafter referred to as QI), toluene insoluble matter (TI) amount (hereinafter
The quantification of TI) was performed according to JIS K 2425-1983. (Comparative Example 1) Coal tar pitch (A) obtained by distilling coal tar generated in a coke oven and having a QI of 2.3% by weight and a TI of 9.5% by weight was heated to 400 ° C. to generate mesophase microspheres. .

The analysis value of the pitch after the heat treatment was QI = 30.5% by weight and TI = 92.8% by weight. Observation of the structure with a polarizing microscope showed formation of mesophase microspheres having a particle size of 15 to 35 μm. The obtained heat-treated pitch was extracted with tar-based medium oil (coal-tar medium oil), insoluble components were filtered and collected, and then dried to obtain mesophase microspheres.

The yield of mesophase spherules based on the raw coal tar pitch was 33.1% by weight. Tables 1 and 2 show the production conditions and the obtained results in this comparative example. (Example 1) The extract obtained after the solvent extraction in Comparative Example 1 was distilled to obtain a residual pitch (B), which is an extracted component (solvent soluble).

The obtained residual pitch (B) was QI = 0.1% by weight and TI = 7.8% by weight. Next, the above-mentioned comparative example 1
The coal tar pitch (A) and the remaining pitch (B) used in the above were mixed and mixed at a weight ratio of 2: 1 and QI = 1.6% by weight, TI
= 8.9% by weight of a raw material for heat treatment (mixing pitch). Next, the mixed pitch was heat-treated at 400 ° C. in the same manner as in Comparative Example 1. As a result, a pitch of QI = 35.8% by weight and TI = 94.2% by weight was obtained.

Observation of the resulting heat-treated pitch with a polarizing microscope revealed that mesophase microspheres having a particle size of 20 to 40 μm were formed. Next, the obtained heat-treated pitch was extracted with a tar-based medium oil in the same manner as in Comparative Example 1, and the insoluble component was filtered.
It was recovered and then dried to obtain mesophase microspheres. The yield of mesophase small spheres based on the heat treatment raw material pitch (mixed pitch) was 36.5% by weight.

Tables 1 and 2 show the manufacturing conditions and the results obtained in this example. (Example 2) The coal tar pitch (A) used in Comparative Example 1 and the remaining pitch (B) obtained in Example 1 were 1: 2.
And QI = 0.9% by weight, TI = 8.8
A raw material for heat treatment (mixing pitch) was prepared by weight%.

Next, the mixed pitch was adjusted to 40
As a result of heat treatment at 0 ° C., QI = 37.2% by weight, TI = 94.5%
A weight percent pitch was obtained. Observation of the obtained heat-treated pitch with a polarizing microscope revealed formation of mesophase spherules having a particle size of 25 to 45 μm. Next, the obtained heat-treated pitch was extracted with a tar-based medium oil in the same manner as in Comparative Example 1, and the insoluble components were filtered and collected, followed by drying to obtain mesophase microspheres.

The yield of mesophase microspheres based on the heat treatment raw material pitch (mixed pitch) was 40.5% by weight.
Tables 1 and 2 show the production conditions and the results obtained in this example. (Example 3) The coal tar pitch (A) used in Comparative Example 1 and the remaining pitch (B) obtained in Example 1 were 1: 3.
At a weight ratio of QI = 0.7% by weight, TI = 8.2
A raw material for heat treatment (mixing pitch) was prepared by weight%.

Next, the mixed pitch was set to 40
As a result of heat treatment at 0 ° C., QI = 35.6% by weight, TI = 93.8
A weight percent pitch was obtained. Observation of the obtained heat-treated pitch with a polarizing microscope revealed formation of mesophase microspheres having a particle size of 20 to 40 μm. Next, the obtained heat-treated pitch was extracted with a tar-based medium oil in the same manner as in Comparative Example 1, and the insoluble components were filtered and collected, followed by drying to obtain mesophase microspheres.

The yield of mesophase spherules based on the heat treatment raw material pitch (mixed pitch) was 38.8% by weight.
Tables 1 and 2 show the production conditions and the results obtained in this example. (Example 4) The coal tar pitch (A) used in Comparative Example 1 and the remaining pitch (B) obtained in Example 1 were 1: 9.
And QI = 0.3% by weight, TI = 7.9
A raw material for heat treatment (mixing pitch) was prepared by weight%.

Next, the mixed pitch was adjusted to 40
As a result of heat treatment at 0 ° C., QI = 33.1% by weight, TI = 93.4%
A weight percent pitch was obtained. Observation of the obtained heat-treated pitch with a polarizing microscope revealed that mesophase small spheres having a particle diameter of 20 to 100 μm were formed, and the particle diameter was uneven. Next, the obtained heat-treated pitch was extracted with a tar-based medium oil in the same manner as in Comparative Example 1, and the insoluble components were filtered and collected, followed by drying to obtain mesophase microspheres.

The yield of mesophase spherules based on the heat treatment raw material pitch (mixed pitch) was 34.3% by weight.
Tables 1 and 2 show the production conditions and the results obtained in this example. (Comparative Example 2) The coal tar pitch (A) used in Comparative Example 1 was heat-treated at 420 ° C.

The analysis value of the obtained heat treatment pitch is QI = 4
8.3% by weight, TI = 97.8% by weight. As a result of observing the obtained heat-treated pitch with a polarizing microscope, the mesophase microspheres and the mesophase grown in a bulk form showed an optical structure mixed with an isotropic structure, and the mesophase microspheres were not selectively generated, and subsequent extraction was performed. Separation could not be performed.

The production conditions and the results obtained in this comparative example are shown in Tables 1 and 2. As is clear from the examples described above, the yield of the mesophase small spheres can be improved by preparing the raw material pitch for the heat treatment by the method of the present invention and producing the mesophase small spheres. Further, after the heat treatment, the mesophase small spheres are separated and collected, the remaining pitch is collected and recycled, and used again as a heat treatment raw material. Therefore, the raw material can be effectively utilized with a very high yield.

Further, by preparing the mixing pitch so that the quinoline-insoluble content of the mixing pitch is within a specific range, it has become possible to obtain mesophase microspheres having a uniform particle size distribution.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

According to the present invention, it is possible to improve the yield of mesophase spheres, and it is possible to produce mesophase spheres having a uniform particle size distribution.

Claims (2)

[Claims] 1. A method of producing a mesophase small sphere by heat-treating a coal tar pitch, adding a remaining pitch after removing the generated mesophase small spheres to the coal tar pitch, and heat-treating the mixed pitch. A method for producing mesophase microspheres. 2. The quinoline insoluble content of the mixed pitch is set at 0.
The method for producing mesophase microspheres according to claim 1, wherein the content is adjusted to 5 to 2% by weight.