JPH03103490A - Coal tar-based impregnating pitch and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject pitch used for producing carbonaceous materials, such as graphite electrodes, or carbon/carbon composite materials by regulating pitch so as to provide low contents of portions, soluble in hexane and insoluble in benzene without containing any portion insoluble in quinoline. CONSTITUTION:The subject pitch, obtained by adding and mixing (A) 1 pts.wt. coal tar with (B) >=2 pts.wt. one or more selected from benzene, toluene and xylene, allowing the resultant mixture to stand, separating the formed superna tant liquid and heat-treating the obtained supernatant liquid at a temperature within the range of 300-380 deg.C and having <5wt.% content of a portion soluble in hexane and <=5wt.% content of a portion insoluble in benzene substantially without containing any portion insoluble in quinoline.

Description

[Detailed Description of the Invention] <Industrial Field of Icheon> The present invention relates to a coal-cooled base pitch used in the production of carbon materials such as graphite denmei or carbon/carbon composite materials, and a method for producing the same. It is. <Conventional technology> In general, impregnated bitch is used for artificial graphite electrodes, divine carbon materials,
It is well known that it is essential for the production of carbon/carbon composite 1fA. Artificial graphite Tr! ．． At the pole, first, a thermoplastic binder pitch is added to coke particles that do not fuse and bind by themselves, and the mixture is fired and carbonized. During the firing process, the binder pinch is Alternatively, due to a thermal reaction, the corresponding amount is released into the gas phase, and the resulting burning electrode is a porous body with low bulk density, which is insufficient in terms of strength and various properties. For this reason, burn rli. '? J. It is necessary to further impregnate and set the electrode using a pinch and burn it again to densify it, and this impregnation/burn process is repeated until the product properties are met. Such impregnation and re-firing steps are essential not only for artificial graphite electrodes, but also for the production of other carbon materials and carbon/carbon composites. This is because these products use coke particles, carbon fibers, etc. that do not fuse and bind themselves, so in order to obtain the final product, it is necessary to mix a binder with plasticity. It is. At this time, it is desirable to use a binder with a high carbonization yield during the firing process, but in any case, evaporation and thermal reactions proceed to varying degrees, so it is unlikely that the fired product will become porous. This cannot be avoided and an impregnation process is required. As is clear from the above explanation, the first characteristic that an impregnating material should have is that it does not contain solid particles. In other words, the impregnating material is required to penetrate into the pores of the porous material, and if solid particles are present in the impregnating material, the pores will be blocked during the impregnation process and impregnation into the interior will be inhibited. This is because it is done. The second type is a car with a high carbonization yield. No matter how well the impregnation progresses inside, if the carbonization yield of the impregnated material is low, void formation due to evaporation and thermal decomposition will occur during the burning process, resulting in repeated impregnation/burning. This is because the process needs to be repeated. For this reason, pitch with a relatively high carbonization yield is used industrially as an impregnating material after being subjected to an operation to remove solid particles. In known methods for manufacturing pinches for impregnation, various methods have been studied from the viewpoint of removing solid particles that cause void clogging. For example, Japanese Patent Publication No. 49-11609 describes a method for obtaining substantially solid tar or pitch with low quinoline insoluble content, which can be efficiently mixed with a solvent and then centrifuged in one step, in trace amounts or 0.4%. It is stated that it is possible to remove up to % of quinoline infusible matter. Also, JP-A-52-78201
The publication proposes a method in which particles containing insoluble quinoline are coarsened using a mixed solvent and then separated by sedimentation. Further, JP-A No. 52-28501 proposes that quinoline insolubles be removed by solvent mixing to reduce the quinoline insolubles to a substantially trace amount of less than 0.1%. In addition, in the current analytical method for quinoline insoluble content, less than 0.1% is considered to be within the error range for analytical values. If pitch is produced from a heavy oil-based raw material such as coal tar that does not contain or contains only a small amount of quinoline insoluble matter obtained by such known technology, pitch with good permeability into voids can be obtained. However, it is still not satisfactory as a pitch for impregnation. This rationale can be easily understood if we consider a car, which is a mixture with a boiling point distribution of four pitches. In other words, the temperature of the impregnated pitch that has penetrated into the pore structure is raised during the calcination carbonization process.
As the temperature rises, the pitch first softens and melts, and as the temperature rises further, some of the low boiling point in the pitch begins to vaporize. At this time,
The vaporized low boiling point gas acts as a vehicle to push the molten pitch out of the void structure, so even if the void structure is all filled with pitch for impregnation, most of it will be lost during the firing process. It is expelled from the void. As a result of this process, we were forced to repeat the impregnation and firing process multiple times, and were forced to accept economic disadvantages in the production of artificial graphite electrodes, various carbon materials, and carbon/carbon composites. It is. Problems to be Solved by the Invention> The problem with the known impregnated pift, namely, the discharge to the outside of the impregnated pift due to the vaporization of low-boiling components during the firing process, can be solved by The problem was solved by using pitch, but it could not be manufactured using known technology. This was because the following technical issues were difficult to solve. First, because low-boiling components have relatively small molecular weights, they make a large contribution to lowering the softening temperature or melting temperature, and if they are completely removed, the softening temperature or melting temperature will increase. This leads to an increase in viscosity at the same temperature, which deteriorates the inclusion property in the microporous structure. In addition, as is well known, the higher the molecular weight and the higher the boiling point, the greater the contribution to the increase in viscosity, so the increase in viscosity due to the removal of low boiling point components reduces the frost at the high boiling point.
Although it is possible to eliminate low-boiling point components and high-boiling point components at the same time, it is a contradictory technical direction.
This problem cannot be solved using known technology. If you try to remove low-boiling components by distillation, evaporation, etc., which are common industrial operations, it is inevitable that the temperature will rise, but if the temperature rises, it will become heavier due to thermal reaction. Therefore, not only does the amount of high-viscosity components such as benzene-insoluble components in the pidge increase, but in extreme cases, mesophase small Lj bodies are generated which are insoluble in quinoline and cause pore blockage during the impregnation process. On the other hand, if one were to proceed with the removal of low-boiling point substances under temperature conditions that suppressed the heavy-boiling reaction, their removal would inevitably be insufficient.

In view of this technical problem, the present invention aims to provide impregnated river pitch with a low content of low-boiling components and low viscosity, and a method for producing the same.

<Means for Solving the Problems> The high performance impregnated river pitch proposed by the present invention substantially has the following features:
A coal tar-based pitch for impregnation characterized by containing no tonoline insoluble matter, a hexane soluble matter of less than 5%, and a benzene insoluble matter of less than 5%. For the heavy ffi part, benzene,
One or more selected from toluene and xylene are added and mixed in a ratio of 2 parts by weight or more, and ff? The method is characterized in that the supernatant liquid produced by the heating process is separated, and then the supernatant liquid is heat-treated in a temperature range of 300 to 380°C. <Operation> Next, the present invention will be explained in more detail. The present inventors have discovered that a static separation operation by adding a solvent to coal-cool, which is known as a method for removing substantially solid quinoline-insoluble components, can only remove quinoline-insoluble components if appropriate conditions are set. Not heavy? [minute or
They discovered that it is also effective in removing impurities that can easily become heavy due to thermal reactions. In other words, by changing the mixing ratio of solvent to coal cool, we have created a vehicle that reduces the concentration of heavy components in the supernatant of static fractionation, or components that can easily become heavy due to thermal reactions. This vehicle is a vehicle that reduces the amount of heavy reaction that would inevitably occur in the devolatilization operation of low-boiling components required in the production of high-performance impregnated river pitch, and therefore This makes it possible to remove low boiling point components without causing rrX quality, that is, high viscosity of the product pitch. The present inventors have discovered that benzene,
toluene. Distillation equipment for xylene, etc. is often attached to
In view of the fact that cars with F Therefore, they found that it is necessary to add and mix 211 parts or more of the above solvent]1τ. In other words, when less than 2 parts of the above-mentioned solvent is added and stirred to 1 part of coal tar, the heavy components in the coal tar, represented by benzene-insoluble components, are not insolubilized or vomited to the solvent, but are dissolved in the supernatant liquid. It is undesirable because it is dissolved and becomes concentrated in the temperature atmosphere during the devolatilization process, causing high viscosity. Also, under these conditions, many components that tend to become heavy are dissolved. Under the temperature atmosphere during the devolatilization process, ゜ζbenzene insoluble matter is newly generated, which leads to an increase in the viscosity of Pinochi, which is undesirable.

In this way, as the addition and mixing ratio of the solvent increases, the benzene-insoluble content in the supernatant liquid decreases, but when the amount of the solvent added is 2 parts by weight or more relative to lfftffi parts of coal tar, The amount of benzene insoluble in the coal cool, which is recovered as a supernatant, is less than 0.5%. On the other hand, if low-boiling components, which are defined as hexane-soluble fractions in the present invention, are to be evaporated to less than 5%, a temperature of 300"C or higher is required. At temperatures below 300°C, the vapor pressure of low-boiling components, such as those soluble in hexane, is low. However, if the temperature is raised above 380°C, the thermal reaction will proceed extremely rapidly, and the heavy content represented by the benzene-insoluble content will increase rapidly. Therefore, pitch with a benzene insoluble content of less than 5%, which is the objective of the present invention, cannot be obtained.As can be easily understood here, if the benzene insoluble content in the raw material is originally large, the low boiling point Due to the concentration required for devolatilization, it is impossible to obtain a pinch of less than 5% benzene-insoluble matter.Also, in the temperature range of 300°C to 380°C, benzene-insoluble matter is typical. Although the production of heavy components is slow, if there are many components in the raw material that are easily converted to benzene-insoluble components, new benzene-insoluble components will be produced and a pitch with a benzene-insoluble component of less than 5% can be obtained. For this reason, in the present invention, the benzene-insoluble content of the supernatant liquid is reduced to zero.
．． It is desirable to keep it below 5%. By the above means,
For the first time, coal tar pitch containing substantially no quinoline insoluble matter, with both hexane soluble content and benzene insoluble content being less than 5%, can be obtained, but with pitch of this composition,
For the first time, the high quality quality of impregnated river beer 7ji is offered. In other words, by reducing the hexane soluble content, which is a low boiling point component, to less than 5%, the extrusion and outflow from the pitch voids due to the vaporization of the low boiling point component during the burning process after impregnation is reduced. be. Vaporization as the temperature rises during the firing process begins with the generation of fine bubbles in the molten pitch.
These bubbles continue to coalesce to form large bubbles, and a passage to the outside is established by making the large bubbles continuous. When the hexane soluble content is less than 5%, the rate of bubble formation is slow;
Before the pitch expands due to evaporation, a passage to the outside is formed, and the gas generated thereafter is exhausted through this passage, thereby reducing pitch outflow. However, when the hexane soluble content is 5% or more, the rate of bubble growth becomes rapid, and most of the pitch is expanded to the outside by the vaporized gas before a passage to the outside is formed. They are pushed out. In addition, the benzene insoluble content, which causes high viscosity, is 5%.
The viscosity characteristics required for pitch for impregnation are satisfied by the car with less than %. That is, the impregnated river pinch according to the present invention reduces the pitch outflow during the burning process by reducing the hexane soluble content, which is a low boiling point component, but the removal of the low boiling point component necessarily By reducing the components that cause high viscosity, such as benzene-insoluble components, it becomes possible to create a vehicle that maintains the viscosity characteristics required for impregnated pitch. If the benzene insoluble content is less than 5%, the increase in viscosity due to the reduction in hexane soluble content can be offset, but if the benzene insoluble content exceeds 5%, high viscosity cannot be avoided, and the impregnation temperature must be adjusted. It is necessary to ensure the inclusion property by increasing the viscosity and decreasing the viscosity. However, an increase in the impregnating degree increases the vapor pressure of the pitch components at the impregnating temperature, and even if the voids in the material to be impregnated are kept in a vacuum, the impregnated pitch cannot be introduced into the impregnation equipment. Since the vapor pressure of the pitch increases at this point, it has the disadvantage of poor inclusion into the voids. From this rationale, the benzene insoluble content is limited to less than 5%. <Example> The following is a detailed explanation based on an example. Example! 3 parts by weight of benzene was added to 1 mffi part of ordinary coal tar having the properties shown in Table 1, and the mixture was charged into a container to a height of 2 m, allowed to stand still for 2 mouths, and then the supernatant liquid was drained. The benzene contained in the supernatant was removed from the supernatant by distillation. The analytical values of this coal tar cleaned by static separation are as shown in Table 2, and no substantially solid quinoline-insoluble matter was detected, which was below the lower limit of analysis. Furthermore, the benzene insoluble content was 0.5% or less. (ffiffl%) Coal tar having the properties shown in Table 2 was charged into a stainless steel reaction vessel and heated until the liquid temperature rose from room temperature to 340°C.
The temperature was raised at a rate of 3°C/min, and after reaching 340°C, it was held for 2 hours. During this heat treatment process, the evaporated components were distilled out of the reaction vessel through a technical pipe connected to the top of the reactor. Through this operation, pitch with the properties shown in Table 3 was obtained as a residue in the reaction vessel. The hexane soluble content was less than 5%, the benzene insoluble content was also less than 5%, and no adverse effects on quinoline insoluble content were observed. In addition, the softening point is the same as commercially available impregnated bitch, and no increase in viscosity is observed. The content of this pitch! ! /In order to evaluate the burning command characteristics, the following experiment was conducted. That is, by preparing a test firing electrode in advance from commercially available petroleum-based coke and commercially available binder pitch, impregnating this firing electrode, and then firing it,
The impregnation/burning characteristics of the pitch were tested. The incineration electrode used for the test was made with a softening point of 93% for 1 part by weight of petroleum coke crushed so that the particle size 1+w was 90% or more.
Add 0.30 parts by weight of a commercially available binder pitch at
After kneading at a temperature of 160°C, a green electrode with a diameter of 2.5 cm was molded with a piston using an electric furnace.
a) It was fired and carbonized at a final temperature of 950°C. The bulk density of this test electrode was 1.04-1.12 g/cd. This test fired electrode was placed in a stainless steel container, which was then sealed tightly and maintained at a temperature of 160°C, and evacuated using a vacuum bomb to reduce the pressure to 5 millimeters of mercury. After this, the pitch shown in Table 3, which had been preheated to 160°C, was introduced, and after being held for 1 hour after introduction, the inside of the container was returned to normal pressure.
The test m pole that had settled in the molten pitch liquid was pulled up. This impregnated test electrode was heated to a final temperature of 105% using an electric furnace.
It was burned at 0°C and its bulk density was measured. This test was conducted three times and the average value was used for evaluation. When the pitch of the present invention was used, as shown in Table 4, an improvement in bulk density of 0.20 B/cd was observed. Comparative example! Pitch was produced using the same slaked coal tar shown in Table 2 as prepared in Example 1, and the heat treatment conditions were the same as in Example 1, except that the final temperature was changed to 280°C. Table 5 shows the properties of the pitch obtained. Manufactured pitch. Table 7 shows the properties of the obtained pitch. When this pitch was subjected to an impregnating/firing test on a test electrode under the same conditions as in Example 1, as shown in Table 8, the bulk density was improved compared to the results of the Example in Table 4. It was extremely low. When this pitch was subjected to an impregnation/firing test on a test electrode under the same conditions as in Example 1, as shown in Table 6, the improvement in bulk density was significantly greater than in the results of the Example shown in Table 4. It was low. Comparative Example 2 Example 2 was prepared using the same clean coal tar shown in Table 2 as prepared in Example 1 and using the same heat treatment conditions as Example 1 except that the final temperature was changed to 390°C. In advance, the pitch with the properties shown in Table 7 and the commercially available PAN
A carbon/carbon woven fiber fired body was produced using high-strength carbon fiber fabric (one direction) under the following conditions.

That is, the volume ratio of pitch and carbon fiber cloth is 7:3,
Take turns lirr! ! After that, pressurize and mold at a temperature of 220°C, then cool to room temperature, and heat at a rate of 3°C/min from room temperature to 650°C, and hold for 5 hours after reaching 650°C. did. The bulk density of this carbon/carbon fiber fired body is 1
．． 32 (g/c+1).

This test fired body was placed in a stainless steel container, which was then sealed tightly and maintained at a temperature of 160°C, and the pressure was reduced to 5 mm of mercury using a vacuum pump. After this, the pitch shown in Table 3, which had been preheated to lGO'c, was introduced, and after being held for 1 hour after introduction, the inside of the container was returned to room pressure, and the test fired body that had settled in the molten pitch liquid was pulled out. Ta. This impregnated test fired body was heated to a final temperature of 10% using an electric furnace.
It was burned at 50°C and its bulk density and sprouting strength in the carbon fiber direction were measured. This test was conducted three times and the average value was used for evaluation. When the pitch of the present invention was used, as shown in Table 9, an improvement in bulk density of O-18 g/ctl was observed, and the bending strength reached 940 (kg/cd). Table 9 Comparative Example 3 Using the pitch with the properties shown in Table 5, an impregnation/burning test was conducted on the test fired body under the same conditions as in Example 2. As shown in Table 10, the bulk density was The improvement range is shown in Table 9.
This was significantly lower than the results of the examples. In addition, the strength after impregnation/burning was also lower than that of the hydrocarbons of the Examples in Table 9. Table 10 Comparative Example 4 Using the pitch with the properties shown in Table 7, an impregnation/burning test was conducted on the test fired body under the same conditions as in Example 2. As shown in Table 11, the bulk density was The improvement range is shown in Table 9.
This was significantly lower than the results of the examples. Further, the strength after impregnation/calcination was also lower than that of water 11B of Example in Table 9. Table 11 Effects of the invention> In recent years, there has been a demand for high-performance impregnating materials in the field of manufacturing carbon products. This makes it possible to reduce the number of times and increase the density and strength of the product.
The effects on related industrial fields are significant.

Claims (1)

[Scope of Claims] 1. A coal tar-based impregnating pitch characterized by substantially no quinoline-insoluble content, less than 5% hexane-soluble content, and less than 5% benzene-insoluble content. . 2. Add and mix one or more selected from benzene, toluene, and xylene at a ratio of 2 parts by weight or more to 1 part by weight of coal tar, and separate the resulting supernatant liquid by standing. Then, the supernatant liquid was heated to 300 to 380
A method for producing coal tar-based pitch for impregnation, characterized by heat treatment at a temperature range of ℃.