JPH0257839B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pitch for carbon material, and more particularly, to a method for producing pitch for carbon material that improves the yield of mesophase pitch and is suitable as a raw material for carbon fibers and the like.

Carbon fiber, which is known as a composite material for plastics and metals, has traditionally been produced by firing polyacrylonitrile fibers, but the raw material fibers are expensive and the carbonization yield during firing is low. Ta. Therefore, in recent years, various methods have been proposed in which pitch, which has a good carbonization yield, is used as a carbon fiber material.

However, when pitch is used as a raw material, unless the mesophase content in the pitch is substantially 100%, the compatibility between mesophase pitch and isotropic pitch is poor, and uniform spinning cannot be achieved, resulting in the production of products. Mechanical strength is insufficient and high quality products cannot be obtained. For this reason, various methods have been proposed to obtain pitches with substantially 100% mesophase content, but each method has advantages and disadvantages, and no fully satisfactory method has yet been found.

Therefore, the present inventors have developed a method for producing pitches for carbon materials that improves the yield of mesophase pitches that are substantially 100% mesophase, and also improves the mechanical strength of the produced carbon fibers. As a result of intensive studies, we have found that the above objective can be achieved by aging and heat-treating the light oil produced when heat-treating heavy oil to obtain meso-phase pitch under specific conditions and further obtaining meso-phase pitch. Based on this finding, the present invention was completed.

That is, in producing pitch for carbon materials by heat-treating heavy oil, the present invention heats the raw material pitch from which the light oil content in the heavy oil has been removed to a temperature of 400 to 400°C.
By heat-treating at 550°C and a pressure of 0.1 to 20 mmHg, a mesophase pitch containing substantially 100% mesophase is obtained, and the light oil produced in the heat treatment process is aged at a temperature of 380 to 450°C, and then heated again to a temperature of 400°C.
The present invention provides a method for producing pitches for carbon materials, characterized in that mesophase pitches are obtained by heat treatment at ~550°C and pressures of 0.1~20mmHg.

The heavy oil that is the raw material oil in the present invention includes:
A variety can be used. Particularly suitable are heavy oils with a high aromatic hydrocarbon content, such as catalytic cracking residual oils of petroleum fractions and thermal cracking residual oils such as naphtha.

In the method of the present invention, light components are removed from the above-mentioned heavy oil to obtain raw material pitch. Light oils, especially those with a boiling point of 400° C. or lower (calculated under normal pressure), can be removed by conventional vacuum distillation. Note that at this time, it is preferable to remove ash from the heavy oil in advance using a filter or the like.

Next, the obtained raw material pitch is subjected to heat treatment. Heat treatment conditions are temperature 400~550℃, preferably
420~500℃, pressure 0.1~20mmHg, preferably 1~
It should be carried out at 10 mm Hg for 0.5 to 150 minutes, preferably 1 to 30 minutes.

Although the heat treatment of the raw material pitch may be carried out within the range of the above conditions, it is particularly preferable to carry out the heat treatment in two stages. When carrying out the process in two stages, the processing conditions for the second stage should be stricter than those for the first stage. Here, the first stage of heat treatment is
400-460℃, pressure 5-20mmHg, preferably temperature
0.1-20 at 410-450℃ and pressure 10-20mmHg
The treatment time is preferably 0.2 to 10 hours. In addition, the second stage heat treatment is performed at a temperature of 450-500℃ and a pressure of 0.1-
5mmHg, preferably temperature 460~500℃, pressure 0.5~
It may be carried out for 0.2 to 30 minutes under the condition of 3 mmHg.

By the above heat treatment, a mesophase pitch containing substantially 100% mesophase is obtained. During the heat treatment, the light oil produced is condensed and recovered.

Next, in the method of the present invention, the recovered light oil is aged and then heat treated again to obtain mesophase pitch. Here, the ripening conditions for the light oil may be carried out at a temperature of 380 to 450°C, preferably 390 to 420°C, and conditions such as pressure and time may be appropriately determined in consideration of the components of the light oil. Usually the pressure is 100~
1-10 at 1500mmHg, preferably 750-770mmHg
It may be carried out for an hour, preferably 4 to 6 hours.

If the temperature is below 380°C, the light oil content will not become heavy enough, and if it exceeds 450°C, the weighting will proceed too much, which is not preferable.

After aging, the same heat treatment as above is performed. The heat treatment conditions are the same as those for the raw material pitch, temperature 380-450°C, preferably 420-500°C, pressure 0.1
~20mmHg, preferably 0.5-150 at 1-10mmHg
It may be carried out for 1 to 30 minutes, preferably 1 to 30 minutes.

By this heat treatment, a mesophase pitch containing substantially 100% mesophase can be obtained again. The mesophase pitch thus obtained can be suitably used as pitch for carbon material together with the mesophase pitch obtained from the raw material pitch described above.

In order to produce pitch-based carbon fibers from these pitches for carbon materials, the pitches are first spun by a conventional method, then treated to be infusible, and then fired.

According to the method of the present invention, both the mesophase pitch obtained from the heat treatment of the raw material heavy oil and the mesophase pitch obtained from the recovered light oil can be effectively used as pitch for carbon materials, and the mesophase pitch for the raw material is The yield of phase pitches is extremely improved, and it is highly economical.

Furthermore, the mesophase pitch obtained from heat treatment of light oil is completely free of impurities, and products such as carbon fiber obtained from such pitch have excellent mechanical strength, such as tensile strength and elastic modulus. It is something that

Therefore, the present invention can be extremely advantageously used in the production of carbon materials, particularly various carbon products such as carbon films, filaments, and yarns including carbon fibers.

Next, the present invention will be explained in detail with reference to examples.

Example 1 The residual oil obtained by fluid catalytic cracking of heavy gas oil was distilled under reduced pressure to remove the fraction with a boiling point (normal pressure equivalent) of 500°C or lower to obtain a residue pitch. The softening point of this residue pitch was 100°C. This residue pitch is 420
A pitch with 100% mesophase was obtained by heat treatment at 10 mmHg and 10 mmHg for 2 hours. The yield of mesophase pitch relative to the residue pitch was 30%. on the other hand,
Light oil vapor generated during this heat treatment was condensed and collected, and this was aged at 400°C for 5 hours at normal pressure to obtain aged pitches. The softening point of the aged pitcher obtained was 120°C. 2mm of this aged pitch
Pitch with 100% mesophase was obtained by heat treatment at 460°C for 10 minutes. The yield of mesophase pitch based on the light oil content was 30%. The softening point of the resulting pitcher was 330°C.

The mesophase pitch obtained in this way was heated to 360°C.
Pituchi fiber obtained by melt spinning in the air
After being infusible at 300°C for 1 hour, carbon fibers with a thread diameter of 8 μm were obtained by firing at 1500°C for 5 minutes.
The obtained carbon fiber had a tensile strength of 300 Kg/mm ² and an elastic modulus of 25 t/mm ² .

In addition, the mesophase pitch obtained by heat treatment of the above-mentioned residue pitch was melt-spun at 320°C, and
The carbon fibers obtained by infusibility at 1500° C. for 1 hour and then firing at 1500° C. for 5 minutes had a tensile strength of 200 Kg/mm ² and an elastic modulus of 20 t/mm ² .

Example 2 The light oil component in Example 1 was aged at normal pressure at 400 °C.
℃ for 7 hours, and heat-treated the aged pitcher for 2 hours.
A pitch for carbon material and carbon fibers were obtained in the same manner as in Example 1 except that the heating was carried out at mmHg and 460° C. for 15 minutes.

The softening point of the mesophase pitch obtained was 335℃,
After melt spinning at 365°C, it was made infusible in air at 300°C for 1 hour, and then fired at 1500°C for 5 minutes to obtain carbon fibers with a thread diameter of 7 μm. This material had a tensile strength of 320 Kg/mm ² and an elastic modulus of 27 t/mm ² .

Claims (1)

[Scope of Claims] 1. When manufacturing pitch for carbon materials by heat treating heavy oil, raw material pitch from which light oil content in heavy oil has been removed is heated at a temperature of 400 to 550°C and a pressure of 0.1 to
By heat-treating at 20 mmHg, a mesophase pitch containing substantially 100% mesophase is obtained, and the light oil produced in the heat treatment process is heated at a temperature of 380 to 450℃.
After aging at temperature 400-550℃, pressure 0.1
A method for producing pitches for carbon materials, characterized in that heat treatment is performed at ~20 mmHg to obtain mesophase pitches. 2 Aging of light oil at a temperature of 380 to 450℃ and a pressure of 100℃.
The manufacturing method according to claim 1, which is carried out at a temperature of ~1500 mmHg.