JPH0733513B2 - Method for producing high-viscosity pitch for carbon material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention produces a high-viscosity, high-remaining-coal rate, and uniform pitch, which is a raw material for carbon fibers, activated carbon fibers, and various other carbon materials. Regarding the method.

(Prior Art) Various carbon materials such as carbon fiber have excellent functionality such as heat resistance, chemical resistance, electrical conductivity, slidability, and strength, and are extremely useful as various industrial materials. is there.

In order to produce these carbon materials, tar pitch raw materials are often used as a carbon raw material source in terms of cost, quality, and quantity and occupy an important position. However, since the tar pitches differ in composition contained depending on the generation source, it is necessary to prepare the composition according to the desired application. For example, in order to produce carbon fiber, in order to perform spinning smoothly, free carbon derived from the raw material contained,
It is necessary to remove solids such as ash in advance. Also,
Considering the infusibilization and carbonization steps after spinning such a pitch, it was necessary to heat the pitch to make the pitch composition heavier and to increase the viscosity in order to prevent fusion between the fibers.

(Problems to be Solved by the Invention) Although many proposals have been made so far regarding the thermal reforming method, any of the conventional methods has spinnability,
It has not been possible to efficiently manufacture a high softening point pitch excellent in infusibility at low cost. That is, since the pitches have a very wide range of molecular weight distribution, if the softening point is increased only by a simple heat treatment, the polycondensation reaction of the high molecular weight component causes the formation of mesophase as a foreign substance, and conversely the formation of mesophase. When heat treatment was carried out while suppressing the pitch, it was not possible to obtain a pitch having a viscosity satisfying the infusibilizability. Therefore, for example, JP-A-55-98914 discloses the use of a special softening point raising agent, and JP-A-55-98
Japanese Patent No. 914 discloses the necessity of separating a specific component. On the other hand, a method of removing solid matter derived from the raw material and foreign matters such as mesophase generated during the heat treatment after the raw material is sufficiently heat-treated (JP-A-1-97215) is also proposed. Already has a high viscosity, the removal efficiency of such foreign matter is poor, and a special removal technique is required.

Further, the impregnating pitch used for the carbon / carbon (hereinafter referred to as “C / C”) material must have a high residual carbon rate and be capable of smoothly impregnating the base metal. Similar to pitch for carbon fiber, it is required to have high viscosity and homogeneity.

Therefore, an object of the present invention is to provide a method for advantageously solving the above-mentioned various problems, that is, without adding a special additive to the raw material or performing a special treatment technique, An object of the present invention is to provide a method for efficiently producing a highly viscous and homogeneous optically isotropic pitch.

(Means for Solving the Problems) As a result of intensive investigations by the present inventors to solve all of the above-mentioned various problems, the coal tar recovered from the generation source was filtered by a known method such as sedimentation separation. After separating and removing solids contained in tars, distillation is performed to prepare a heavy amount of pitch, and then a high viscosity useful as a raw material for various carbon materials by subjecting the prepared pitch to heat treatment, It has been found that a homogeneous optically isotropic pitch can be produced, and the present invention has been accomplished.

That is, the present invention, when the purified coal tar is distilled and pitched, by adjusting the distillation conditions by the raw material tar used, the heavy content is controlled to a constant concentration, during heat treatment It is possible to perform sufficient modification of the pitch composition in a temperature range in which no foreign matter such as mesophase is generated without the need for an additive or a special separation method.

Specifically, the present invention, after producing a high-viscosity isotropic pitch for a carbon material raw material from coal tar pitches as a raw material, after purifying the crude raw material tar by filtration, sedimentation separation or the like to remove solid content, It is characterized in that the refined pitch is obtained by distilling at a temperature of 370 ° C. or lower to remove the tar oil component to obtain a refined pitch, and further heat treating the refined pitch.

The present invention will be described in detail based on its configuration.

Generally, coal tars are by-produced by dry distillation of coal at the time of coke production, and therefore, inorganic matter such as ash derived from raw materials, free carbon, and insoluble solid matter such as coke powder are contained in the range of several to 20%. Therefore, if coal tars are directly prepared into pitch by distillation or the like and used as a raw material for the carbon material, it may cause a decrease in efficiency in the manufacturing process of the carbon material and a defect in the carbon material itself due to the influence of residual solids. These solids should be removed in advance before being used as a carbon material. The pitch prepared for such a carbon material has a high viscosity and separation of solid matter is usually very difficult, but the present invention has a low viscosity such that the raw material tar is in a stage, that is, the tar is liquid at room temperature. Since the solid matter is separated in this state, high temperature and high pressure are not required, and the separation can be efficiently performed by a commonly known method such as filtration and sedimentation separation.

Next, the tar, which is obtained by separating and purifying the solid matter, is distilled to remove the tar oil component to prepare pitch which is a thermal reforming raw material. Here, the tar oil component is a component that evaporates under a distillation condition of 370 ° C. or lower, which will be described later. In this step, by controlling the distillation conditions such that the content of heavy components of the obtained distillation pitch (refining pitch) is within a certain range, it is possible to suppress the mesophase that is secondarily generated during the heat treatment in the subsequent step. Here, the certain range of heavy components is the benzene insoluble component (B
It can be specified by the content of I) and is in the range of 3% by weight to 12% by weight. When the content of benzene insoluble matter is more than 12% by weight, the amount of the polymer component serving as a precursor of mesophase increases, so that the mesophase is likely to be generated during the heat treatment in the final step, which is not preferable. Is less than 3% by weight, high temperature or a long time is required to promote the heaviness during the heat treatment in the final step, and as a result, mesophase is easily generated, which is not preferable. Further, the distillation temperature at this time is required to be 370 ° C or lower. This is because at a temperature of 370 ° C. or higher, the polycondensation reaction of the high molecular weight component causes the composition of the heavy component to become more polymerized. Here, the mesophase is generated as fine spheres in the initial process when the pitches are heat-treated, grows and coalesces as the heat treatment progresses, and spreads throughout the pitch.
It finally becomes coke through the bulk mesophase. The pitch generated by this mesophase is non-uniform as a whole because the viscosities of the optically isotropic portion and the optically anisotropic mesophase portion are different. Therefore, yarn breakage in the spinning process during the production of fibers and the like, and nozzle clogging of the spinning device are likely to occur, and it becomes impossible to sufficiently impregnate the carbon base material during the production of the C / C material. In addition, the pitch that has been heat-treated until the mesophase is formed has an increased viscosity due to the heaviness, and since the mesophase itself is not a perfect solid and exhibits compressibility, clogging of the filter medium does not occur even when the mesophase is separated by filtration. It is easily generated and industrial separation and removal is difficult. On the other hand, when pitch is prepared by mild heat treatment so as to suppress the formation of this mesophase, volatile light components remain in the pitch and the pitch viscosity is low, so foaming during spinning, fusion during infusibilization or This is not preferable because it causes foaming during firing after impregnation and an increase in the number of impregnations.

Then, the polycondensation reaction of the pitch promotes the heaviness of the refined pitch to increase the viscosity (the temperature at which 100 poise is 270 to 330).
C., preferably in the temperature range of 290 to 310.degree. C.) and subjected to a heat modification treatment to remove low molecular weight components which are volatile at the spinning temperature. The treatment is carried out under normal pressure, under inert gas flow, or under reduced pressure, under inert gas flow, at 300 ° C to 420 ° C. At this time, if the treatment temperature exceeds 420 ° C., mesophase is likely to be generated, and conversely, if it is less than 300 ° C., low molecular weight components cannot be sufficiently removed, which is not preferable. Further, as the processing conditions, the processing time, the degree of vacuum, the flow rate of the inert gas, etc. can be set, but these are determined in consideration of the raw material pitch composition and the processing temperature. That is, it may be appropriately selected based on the viscosity which is the characteristic of the pitch for carbon material obtained by the method of the present invention.

Such a pitch obtained by the thermal modification treatment has a viscosity of 10
The temperature showing 0 poise is 270 to 330 ° C, preferably 290 to 310
Those in the temperature range of ° C are suitable for carbon materials. This is because, as described above, when the viscosity is less than 100 poise, foaming of volatile components, product defects, and reduction of the carbonization yield are likely to occur during processing, and conversely, when the viscosity is higher than this, the carbonization yield is good but during processing. This is not preferable because it has poor fluidity and is susceptible to thermal alteration.

As described above, the method of the present invention makes it possible to produce a homogeneous pitch having high viscosity and low impurities (ash content, quinoline insoluble content (QI), mesophase) using coal tar as a starting material.

(Example) Hereinafter, the present invention will be described in detail with reference to specific examples.

Examples 1 to 4, Comparative Examples 1 to 4 Coal tar (benzene insoluble content: (BI) = 2.5% by weight,
The quinoline insoluble matter ((QI) = 0.5% by weight) was filtered to remove solids, and then distilled at temperatures of 360 ° C., 340 ° C., 320 ° C. and 380 ° C. to obtain purified pitches A, B, C and D, respectively. Got Also,
The same coal tar was distilled as it was without filtration to obtain E. The results are shown in Table 1.

Pitches A, B and C could be pitches substantially free of quinoline insolubles and ash according to the conditions of the present invention. On the other hand, since D was distilled at a high temperature of 380 ° C., the benzene insoluble content was 13.5% by weight. Further, since E was not filtered in advance, the quinoline insoluble content was 2.35% by weight and the ash content was 0.22% by weight.

Next, each of the obtained pitches A to E is heat-treated to prepare a raw material pitch for a carbon material, and the results thus obtained are also shown in Table 1.

As a result of heat-treating the pitches A, B and C as raw materials at 390 ° C. under reduced pressure, it was possible to prepare high-viscosity pitch having no impurities as shown in Examples 1, 3 and 4. No formation of mesophase was confirmed by 400 times polarization microscope observation in any of these pitches.

On the other hand, with respect to the pitch D, quinoline insoluble matter was generated when heat-treated under the same conditions, and it was confirmed by microscopic observation with a 400-fold polarization microscope that fine mesophases (diameter of several μm) were generated.

Further, in Comparative Example 1, the quinoline insoluble matter and mesophase were both confirmed because the heat treatment temperature was high, and in Comparative Example 2, only a low-viscosity pitch was obtained because the heat treatment temperature was low.

Furthermore, in Example 2, the same pitch as that of Example 1 could be prepared using pitch A under normal pressure and under the condition of nitrogen gas 20 ml / min-g (charge pitch).

From the pitches of Examples 1 and 2 prepared according to the method of the present invention, excellent spinnability and infusibilizing property for carbon fiber production were obtained, and when carbon fiber was used, products having excellent strength and elastic modulus were obtained. Had characteristics.

(Effects of the Invention) As described above, by using the method of the present invention, coal tar as a starting material is refined, distilled, and heat-treated to thereby exhibit excellent handling properties and carbon material product characteristics. The effect that it becomes possible to manufacture a possible pitch is obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Kamishita 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division

Claims (6)

[Claims] 1. A method for producing a high-viscosity isotropic pitch for a carbonaceous material raw material from coal tar pitches as a raw material, wherein raw material tar is purified by filtration, sedimentation separation or the like to remove solids, and then 370 A method for producing a high-viscosity pitch for a carbon material, which comprises distilling at a temperature of ℃ or less to remove a tar oil component to obtain a refined pitch, and further heat-treating the refined pitch. 2. The benzene-insoluble content of the purified pitch is 12
The method for producing a high-viscosity isotropic pitch for a carbon material raw material according to claim 1, characterized in that the distillation treatment is carried out so that the content is from 3% by weight to 3% by weight. 3. The benzene-insoluble content of the refined pitch is 12
2. The method according to claim 1, wherein the purification and distillation treatments are carried out so that the quinoline insoluble content is substantially not contained and the ash content is less than 0.01% by weight. 4. The method according to claim 1, wherein the heat treatment is performed under normal pressure and in the flow of an inert gas. 5. The method according to claim 1, wherein the heat treatment is performed under a reduced pressure and an inert gas flow. 6. The heat treatment so that the temperature showing 100 poises of the high-viscosity isotropic pitch obtained by the heat treatment is within a temperature range of 270 to 330 ° C. and the entire surface is optically isotropic. The method of claim 1, wherein the method is performed.