JPH0362197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pitch suitable for producing carbon materials, particularly carbon fibers. 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. For this reason, in recent years, many methods have been proposed for producing carbon fibers using pitch as a raw material. However, when producing carbon fibers using pitch as a raw material, high quality carbon fibers cannot be obtained unless the pitch contains substantially 100% mesophase pitch. That is, if the mesophase pitch content is 40 to 90%, uniform spinning cannot be achieved due to poor compatibility between the mesophase pitch and isotropic pitch, and the mechanical strength of the product is also insufficient. Therefore, in order to obtain high-quality pitches, various proposals have been made regarding the properties of raw pitches, heat treatment conditions, and methods for separating mesophase pitches and isotropic pitches, but none of these methods have problems with spinnability or This method has advantages and disadvantages in terms of performance and productivity, and no fully satisfactory method has yet been found. The present invention solves these conventional problems and enables the production of carbon fibers that can shorten the time for infusibility treatment, have a high mesophase content, and have excellent performance such as spinnability, strength, and elastic modulus. The purpose of this invention is to provide a method for manufacturing pitches for carbon materials suitable for. That is, in producing pitch by heat-treating petroleum-based residual oil, the present invention heats raw material pitch from which the light oil content in petroleum-based residual oil has been removed at a temperature of 400°C.
After performing the first heat treatment under the conditions of ~440℃ and pressure of 5 to 30 mmHg, and separating and removing the mesophase pitch in the generated pitch, the isotropic pitch was heated to temperature of 450 to 500℃ and pressure.
The present invention provides a method for producing a pitch for a carbon material, which is characterized by performing a second heat treatment under conditions of 0.1 to 5 mmHg to obtain a pitch containing substantially 100% mesophase. The raw material oil used in the method of the present invention is a petroleum-based residual oil, and examples of the petroleum-based residual oil include catalytic cracking residual oil of petroleum fractions, pyrolysis residual oil such as naphtha, etc. with a high aromatic hydrocarbon content. A high one is preferably used. In the method of the present invention, such petroleum-based residual oil is previously distilled under reduced pressure to remove light oil components with a boiling point of about 400°C or less, and the residual oil is used as a raw material pitch.
In addition, in carrying out the vacuum distillation, it is preferable to remove the ash content in the petroleum residual oil in advance using a filter or the like. Next, the raw material pitch is subjected to a first heat treatment.
This first insulation treatment is performed at a temperature of 400 to 440℃ and a pressure of 5 to 30℃.
mmHg, preferably temperature 410-430℃, pressure 7-20
It is performed under mmHg conditions. Note that the heat treatment time is usually 0.2 to 10 hours, preferably 0.5 to 5 hours. This first stage heat treatment yields a mixture of isotropic pitch and mesophase pitch having a mesophase pitch content of 5 to 50% by weight. Here, the temperature of the first stage heat treatment is
If the temperature is less than 400°C, the reaction will be slow and the heat treatment will take a long time, while if it exceeds 440°C, the amount of volatile matter removed will increase and the yield will decrease, which is not preferable. In addition, if the pressure in the first stage heat treatment is less than 5 mmHg, the amount of volatile matter removed will increase and the yield will decrease;
If it exceeds mmHg, the content of light components in the pitch will increase, and foaming will be severe, making it difficult to separate the difference in specific gravity by standing still, which is not preferable. In addition, this first stage heat treatment is carried out so that the content of toluene insoluble matter in the isotropic pitch produced by this first stage heat treatment is 10 to 70% by weight, more preferably 20 to 60% by weight. It is preferable to carry out the adjustment. The content of toluene-insoluble matter in the isotropic pitch can be adjusted, for example, by increasing the heat treatment temperature and by increasing the reaction time. In this way, the content of toluene-insoluble matter in the isotropic pitch is adjusted by the first heat treatment, and then, as described later, the mesophase pitch is separated and removed at this point, thereby reducing the amount of low quality without causing a decrease in yield. Mesophase pits can be removed. Therefore, it becomes possible to finally obtain a mesophase pitch that is homogeneous and has good spinnability. Next, the mesophase pitch in the pitch thus generated is separated and removed. The method for separating and removing this mesophase pitch is not particularly limited and may be carried out by specific gravity separation or by using a solvent such as toluene or quinoline, but it is preferably carried out by specific gravity separation. Specific gravity separation is 350~
It is carried out at a temperature of 420°C either by standing still or with gentle stirring. In this way, heavy mesophase pitches accumulate at the bottom of the reactor and are completely removed. The isotropic pitch thus obtained is subjected to a second heat treatment. In this second stage heat treatment, the isotropic pitch after the mesophase pitch has been separated and removed is subjected to more severe conditions than the first stage heat treatment, usually at a temperature of 450 to 500.
℃, pressure 0.1~5mmHg, preferably temperature 460~490
The test is carried out under conditions of temperature and pressure of 0.5 to 3 mmHg. If the temperature of the second stage heat treatment is less than 450℃, it will be difficult to remove light components and the heat treatment time will be longer.
If the temperature exceeds 500°C, coking occurs and it becomes difficult to control the reaction rate, which is not preferable. In addition, if the pressure in the second stage heat treatment is less than 0.1 mmHg, the yield will decrease and the vacuum equipment will be large-scale;
Exceeding Hg is not preferable because the content of light components increases and the performance as a product becomes insufficient. The pitch thus obtained has substantially 100% mesophase (optical anisotropy) and is of extremely good quality. Therefore, the pitch obtained by the present invention can be effectively used in the production of carbon fibers as well as various carbon products such as carbon films, filaments, and yarns. Substantially 100% mesophase obtained by the present invention
To produce pitch-based carbon fiber from pitch, the pitch may be first spun using a conventional method, then subjected to infusibility treatment, and then fired. According to the present invention, pitches having a high mesophase content and substantially 100% mesophase can be obtained. Therefore, there is no need to further separate the mesophase pitch and the isotropic pitch after the second heat treatment, and the product can be used as is for producing carbon products. In addition, since the second stage heat treatment is performed under severe conditions in terms of the manufacturing method, the softening point of the pitch is relatively high, and the time for the infusibility treatment can be significantly shortened compared to the conventional method. Furthermore, in the present invention, high molecular weight substances contained in the mesophase pitch initially generated are removed,
Moreover, since the heat treatment is performed in a high vacuum state, low molecular weight substances are also removed. Therefore, the resulting pitch has a narrow molecular weight distribution and good fluidity, so even though the softening point is high, the spinnability is good. Furthermore, the carbon fiber obtained from this pitch has excellent tensile strength and high modulus of elasticity. Therefore, the present invention can be effectively utilized in the production of carbon materials, particularly carbon fibers. Next, the present invention will be explained by examples. Example 1 The ash content of the catalytic cracking residual oil obtained from the catalytic cracking equipment for heavy gas oil was removed using a filter, and then the light oil content was removed by vacuum distillation. It was used as 100 g of this raw material pitch was subjected to a first stage heat treatment at 420° C. for 1 hour under a vacuum of 10 mmHg. The content of mesophase pitch in the produced pitch was 8% by weight. The content of toluene insoluble matter (according to JIS-K-2425) in the produced isotropic pitch was 35% by weight. The generated pitches are allowed to stand still, and due to the difference in specific gravity, the heavier mesophase pitches accumulate at the bottom of the reactor.
I removed g. Next, remove the isotropic pitch remaining at the top of the reactor by 1 mm.
A second heat treatment was performed for 12 minutes under Hg and 460°C conditions, resulting in 65 g of pitch (yield: 65
%) was obtained. The quinoline insoluble content of this mesophase pitch was 26% by weight, and the softening point was 320°C. Moreover, the number average molecular weight was 1100. Next, the obtained mesophase pitch was spun at a spinning temperature of 360°C.
The fibers were spun at 700 m/min at a spinning speed of 700 m/min. There was no yarn breakage during the spinning process. The infusibility treatment of the obtained fibers was completed by simply raising the temperature from room temperature to 350°C in 100 minutes. Next, carbon fibers were obtained by firing at 1500°C for 10 minutes in an argon atmosphere.
Table 1 shows the physical properties of the obtained carbon fiber. Example 2 In Example 1, the first stage heat treatment was performed at 15 mmHg,
Same as Example 1 except that the treatment was carried out at 420°C for 2 hours and the amount of mesophase pitch separated and removed was 20g, and the second stage heat treatment was carried out at 3mmHg and 480°C for 7 minutes. , substantially mesophase
60 g (60% yield) of 100% pitch was obtained. The quinoline insoluble content of this product is 30% by weight, and the softening point is
It was 320℃. Moreover, the number average molecular weight was 1150. Next, this mesophase pitch was treated in the same manner as in Example 1 to obtain carbon fibers. Table 1 shows the physical properties of the obtained carbon fiber. Comparative Example 1 In Example 1, the first stage heat treatment was performed at 10 mmHg,
Example 1 except that the treatment was carried out at 420°C for 1 hour, and the amount of mesophase pitch separated and removed was 6 g, and the second stage heat treatment was carried out at 10 mmHg and 420°C for 6 hours. In the same manner as above, 65 g of pitch (yield: 65%) containing substantially 100% meso phase was obtained. The quinoline-insoluble content of this product was 60% by weight, and the softening point was 280°C. This pitch is spun at 350℃,
Infusibility treatment was carried out in air at 270°C for 2 hours,
Carbon fibers were obtained by firing at 1500°C for 10 minutes. Table 1 shows the physical properties of the obtained carbon fiber. Comparative Example 2 In Example 1, the first stage heat treatment was performed at 3 mmHg,
The procedure was the same as in Example 1, except that the treatment was carried out at 430°C for 1 hour, and the amount of mesophase pitch separated and removed was 25g, and the second stage heat treatment was carried out at 20mmHg and 420°C for 5 hours. Mesophase pitch content
20 g of 60% pitch (yield 20%) was obtained. The quinoline insoluble content of this product is 65%, and the softening point is 290℃.
It was hot. This pitch is spun at 370℃,
Infusible at 270℃ in air for 2 hours, 1500℃
Carbon fibers were obtained by firing at ℃ for 10 minutes. Table 1 shows the physical properties of the obtained carbon fiber. 【table】

Claims (1)

[Claims] 1. When producing pitch by heat-treating petroleum-based residual oil, the raw material pitch from which the light oil content in petroleum-based residual oil has been removed is heated at a temperature of 400 to 440°C and a pressure of 5 to
After performing the first stage heat treatment under the condition of 30 mmHg and separating and removing the mesophase pitches in the produced pitches, the isotropic pitch was subjected to the second stage heat treatment under the conditions of the temperature of 450 to 500℃ and the pressure of 0.1 to 5 mmHg. A method for producing pitch for carbon materials, which is characterized by obtaining pitch containing substantially 100% mesophase.