JPS6099009A - Carbon fiber manufacturing method - Google Patents

Abstract

PURPOSE:To obtain carbon yarn having high strength and high modulus of elasticity, by purifying and distilling coal tar pitch, fractionating it in to mesophase pitch and distillate, treating the distillate under specific conditions to improve it, remixing the treated distillate with the mesophase pitch, spinning the mixture. CONSTITUTION:A large amount of coal tar (pitch) prepared as a by-product during carbonization of coal is extracted with an aromatic solvent such as toluene, etc., and heat-treated to give purified pitch. The purified pitch is then distilled under reduced pressure to fractionate it into mesophase pitch and distillate, the distillate is further treated with molecular hydrogen in an aliphatic hydrocarbon such as n-pentane, etc. in the presence of extremely strong acid such as hydrobromic acid, etc. as a catalyst to improve it. The treated distillate is blended with the mesophase pitch, and heat-treated, to give spinning pitch. Then, the spinning pitch is spun, made infusible, and carbonized, to give the desired carbon yarn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carbon fiber from a large amount of coal tar or coal tar pitch that is reproduced during carbonization of coal.

Charcoal) + 4 *jk The method for producing 'j'lf includes synthesis of polynacryloni 1 to lyl, etc. 1! There are two methods: one uses I II as a raw material, and the other uses petroleum pitch or coal tar pitch as a raw material.

The former method uses the l! The price of miscellaneous materials is high, and the carbonization yield is low. Therefore, there is a drawback that the manufacturing cost I- becomes high.

On the other hand, the latter method uses inexpensive raw materials and has a high carbonization yield. Furthermore, it is known that the carbon structure produced from mesophase pitch derived from these pitches has significantly developed aromatic plane crystals, has high strength, and has a higher modulus of elasticity than polyacrylonitrile carbon 111N. There is. For this reason, many methods have been proposed for producing carbon fibers using these pitches as raw materials, particularly methods for hydrogenating pitch when producing mesophase pitch from coaltarim pitch.

These hydrogenation methods include N i -MO, /'A I
20s, Go-MO/A I203, Fe2O3,
A method of hydrogenating pitch with hydrogen molecules under a solid catalyst such as N 101M003, and a method of hydrogenating pitch using hydrogen-donating solvents such as tetralin, tetrahydroxylin, 9.10-dihydroan I-rahine, etc. as a hydrogenation agent. There is a method for hydrogenating pitch.

The former method using hydrogen molecules is a simple process, but it is difficult to remove the catalyst from the hydrogenated pitch.

Furthermore, during hydrogenation, coking and metaphase are produced on the catalyst, which may be mixed into the pitch produced, lowering the strength of the carbon fibers, and causing non-uniformity. In addition, this method requires hydrogenation to be carried out in a low viscosity state, either by using coal tar itself as a raw material or by adding a solvent to the pitch, but in this case, the amount of hydrogen consumed increases and the hydrogenation There is a possibility that the yield of pitch will decrease. On the other hand, in the latter method using a hydrogen-donating solvent,
Problems such as catalyst separation and coking can be easily avoided, and hydrogen is not wasted. Furthermore, since the state of mesoface pitch differs depending on the hydrogen-donating solvent, it is possible to control the quality of the product by changing the type. However, while this method can be effectively applied to petroleum-based pitches, synthetic bigs, and those that mix and dissolve well with hydrogen-donating solvents, coal tar pitch with a high aromatic content has low solubility and There is a tendency for the mesophase pitch to become non-uniform.

From this, a method using tetrahydroquinoline, which is highly soluble in coal tar pitch, has been proposed, and according to this method, an extremely excellent pitch for spinning can be obtained.

However, in this method, since unrefined pitch is used as a raw material, the amount of low molecular weight mobilization and super heavy 71 substances contained in the pitch increases, resulting in an increase in production cost.

In view of the above circumstances, the present invention aims to provide a method for producing high-strength, high-modulus carbon V&miscellaneous from coal tar pitch.

That is, the present invention extracts coal tar pitch with an aromatic solvent, heat-treats it to remove refined pitch, distills it and separates it into mesophase pitch and an extract, and then extracts the extract into aliphatic hydrocarbons and hydrogen. After being modified by molecules using a super strong acid as a catalyst, it is mixed with the mesoface pitch and heat treated to give it a U Uj yarn upper pitch at, t.Then, this spinning big is skewered into a fj yarn to make it invincible. Characterized by carbonization.

The present invention will be explained in detail below.

First, soft pitch and medium pitch obtained by distilling coal tar are extracted with an aromatic solvent and heat treated to obtain purified pitch.

1. Coal tar and coal tar pitch include:
It contains components with a molecular weight of 500 or less to 1,000 or more, and has an extremely wide molecular distribution, and also contains quinoline-soluble components such as free carbon, coke powder, and coal powder. Therefore, in order to convert lutarubicin into big for spinning, it is necessary to narrow the molecular weight distribution by removing both the low boiling point substances and the quinoline solvent. Therefore, in the present invention, purified pitch is obtained by dissolving coal tar pitch and an aromatic solvent in advance, removing the material equivalent to the quinoline solvent by coagulation and precipitation, and then removing the aromatic solvent by heat treatment.

Here, as the aromatic solvent, benzene, toluene, xylene, methylnaphthalenes, etc. or a mixture thereof is used. Further, the solvent is preferably used in an amount ranging from room temperature to boiling point in an amount of 1 to 20,000 parts by weight, particularly 2 to 10 parts by weight per 1 part by weight of pitch.

Next, the purified pitch thus obtained is distilled under reduced pressure and separated into mesophase pitch and a distillate. In this case, the distillation conditions are such that the distillation temperature is 350 to 500℃, especially 380℃.
~480"C, distillation pressure 0°1~100#+#lH
It is particularly preferable to take a period of 5 to 50 mm HQ, a period of 1M to 11M, and a period of 1 to 10 hours, particularly 0.5 to 5v1. Here, it is preferable to set the distillation temperature to 500℃ or less because the temperature is high! When this occurs, the polycondensation reaction becomes active,
This is because mesophase tends to solidify and turn into coke.

Note that the mesophase pitch referred to here is measured under a polarizing microscope.
It shows optical anisotropy, and the distillation residue contains 0.1 to 95%,
[10 to 8096] Show what is contained.

The pitch thus adjusted (hereinafter referred to as MAI7'-pitch) contains 50 to 80% mesophase. Here, in order to obtain carbon au with a high tensile modulus, it is necessary to have a mesophase content of 50% or more σ), but in order to improve spinnability, it is better to have less mesophase.

On the other hand, the distillate obtained by distillation under reduced pressure is reformed (hydrogenated, alkylated) with aliphatic hydrocarbons and hydrogen molecules using a super strong acid as a catalyst. In this case, it is separated into components with temperatures above 350℃ and components with temperatures below 350℃ using a normal pressure exchange sieve.
It is preferable to use a fraction with a temperature of 50°C or higher. The reason for this is that it is preferable to have three or more aromatic rings in view of compatibility with pitch, and also because it has high reforming reactivity. Here, aliphatic hydrocarbons have 1 to 50 carbon atoms, and may be linear or branched paraffins, but branched ones have no induction period and are easier to react with. be. Furthermore, a super strong acid is a combination of a Brønsted acid such as hydrogen fluoride and a Lewis acid such as aluminum chloride, and using Hammett's acidity function HO, H
o<-11,93. For example, HF-TaF
5, (1: 1'E/L/ratio), HBr-AlBr3
, Fe2O3-8042-1SbFs -FSO3H(
1:1 molar ratio), +SLFterMma03 (1:1 molar ratio), etc. are used.

These include not only liquid carriers but also various carriers such as graphite, -8i02-AI20a, 5iO2-Ti02, S
102-Zr02, etc.) and 7j solid superacids are also included. These are easy to separate after the reaction and are particularly effective in the present invention.

In addition, the amount of super strong acid and aliphatic hydrocarbon added to the distillate (35
0.01 to 1M parts of super strong acid (boiling point above 0℃)
10 parts by weight, especially 0.05 to 5 parts by weight, and in the presence of 0.01 to 10 parts by weight, especially 0.01 to 10 parts by weight of aliphatic hydrocarbons.
．． It is preferable to add 5 to 5 equal parts. The heat treatment is carried out under a hydrogen atmosphere (for example, normal pressure to 150 kg/cd), preferably at a treatment temperature of 500°C or lower, particularly 300°C or lower, and for 0.5 to 50 hours, particularly 1.0 to 20 hours.

Next, the reformed distillate is filtered, washed with an aqueous alkali solution and water to stop the reaction, and after removing the super strong acid, the fraction having a temperature of 300° C. or higher in terms of normal pressure is fractionated by distillation. According to NMR measurements, the distillate modified under these conditions contained naphthene rings and alkyl groups, and had a high proportion of heavy parts.

Next, the distillate thus modified is mixed with the mother bidet and subjected to heat treatment. In this case, the treatment conditions are such that 1 to 1 part of hydrogenated distillate is added to 100 parts by weight of mother pitch.
00 parts by weight, especially 5 to 50 parts by weight, and heat treatment temperature 3
It is preferable to carry out the heat treatment at a temperature of 0.00 to 500°C, particularly 350 to 450°C, and a heat treatment temperature of 0.1 to 10 hours, particularly 1 to 5 hours.

Further, the heat treatment atmosphere is not limited to hydrogen or inert gas or autogenous pressure (normal pressure to 50 kg/ci), but may be atmospheric pressure.

In this treatment, the modified distillate is
, 10-dihydroanthracene, it has higher compatibility with MAI7'-bidge, and a uniform reaction can be carried out. Moreover, this distillate is not only a mere hydrogenating agent, but also has an additional effect by itself.

This pitch is then distilled under reduced pressure under the same conditions as the above-mentioned vacuum distillation to remove low-boiling substances produced by hydrogenation to obtain pitch for spinning. It can be seen that this spinning pitch has less fragility than the mesophase in the ma+f- pitch, and has good spinnability.

Then, this spinning bitch is spun to obtain pitch fibers of about 10 to 15 μm, which are infusible and converted into vJ. Here, the spinning temperature is usually about 250 to 380"C. Infusibility is achieved by a known method, for example, by heating in air (below the softening point). Carbonization is carried out in an inert gas atmosphere. It can be carried out at a temperature of about 1000° C. below, but if necessary, graphitization by heating to 2000° C. or higher may also be used.

As described above, according to the present invention, in order to adjust the mesophase pitch by polycondensation without any particular hydrogenation treatment, taking advantage of the property that -rutal pitch easily generates mesophase, Examples of the invention will be described.

Example 1 Five times the amount of toluene was added to a soft pip obtained by distilling coal tar, heated to 90°C, stirred and dissolved, and insoluble matter was filtered under reduced pressure. At this time, the insoluble content was 4% by weight based on the raw material soft pitch.

Then, after removing toluene by distillation,! - The toluene soluble content was subjected to vacuum heating under a reduced pressure of 15 mm HO, and the kettle oil temperature was maintained at 420° C. for 2 cycles to obtain a mother pitch and a distillate containing 50% mesophase. Note that the yields were 25% and 72%, respectively. Put the fraction of 350°C or higher based on normal pressure 1@ into a Hastelloy-CO 1~crepe,
Add aluminum bromide and hydrogen bromide to the distillate, add 3 (8M) n-pentane to the distillate, inject hydrogen at 501 (f/cA), and react at 70°C for 10 hours. After the reaction, the mixture was washed with water and an alkaline aqueous solution, heated under reduced pressure, and a fraction of 350"C or higher was obtained. 20% by weight of this reformed distillate was added to each pitch. The mother pitch was heat-treated at 350°C for 2 hours under a nitrogen stream to hydrogenate the mother pitch.Next, 20% by weight was added to the reduced pressure at 15mHQ, and at 350°C for 2 hours under a nitrogen stream. Heat treatment was performed to hydrogenate the mother pitch.Next, 1
Distillation is carried out until the pitch temperature under pressure reaches 420°C to remove low fractions produced by hydrogenation,
The spinning pitch was (q). At this time, the mesophase was 45%,
The softening point was 275°C. This is processed using the melt spinning method.
Spinning was carried out at 20'C to obtain pitch m fibers. Obtained 15μ
A fiber having a diameter of 250° C. was heated in air at 2° C./min to 250° C. and held at that temperature for one period to make it infusible. The obtained invulnerable m-thickness was infusible to 1000° C. at an infusibility rate of 5° C., . . . minutes under a nitrogen stream, and held at that temperature for 2 hours. The tensile strength of the obtained carbon fiber 15μ is 240
The elastic modulus was 251-ton/2.

Example 2 To medium pitch with a softening point of 73°C obtained by distilling coal tar pitch, 3 pieces of :1 Norin 4 were added and heated to 75°C.
Dissolved while stirring. This material was applied to 111 liters of centrifugal valve to obtain an insoluble content of 5% based on the medium pitch. After removing quinoline, distillation was carried out at 11 and 15, and the kettle oil temperature reached 400° C. at 1-1a. Furthermore, at 420°C, image retention between 2 Bi and mesophase was maintained at 6
A mother pitch containing 096 and a distillate were obtained. The yield is
They were 23% and 73%, respectively. The following steps were carried out in the same manner as in Example 1, and the tensile strength of the 1q carbon fiber (15μ) was 250 to 9/mm2, and the elastic modulus was 26 tons/mm.
It was 2.

Comparative Example 1 Mother pitch obtained in the same manner as in Example 1 [To this, 20% of a distillate treated in the same manner as in Example 1 without adding hydrogen bromide or aluminum bromide was added, and the mixture was heated at 350°C for 2 time,
After heat treatment in N2 atmosphere, heat treatment under reduced pressure (420°C, 15.
The spinning pitch obtained by wmHQ) cannot be formed into a thread shape,
Manufacturing carbon fiber has been difficult.

Claims (1)

[Claims] Coal tar pitch is extracted with an aromatic solvent and heat treated to obtain purified pitch, which is then distilled and separated into mesophase pitch and an extract. After being modified with hydrogen molecules using a super strong acid as a catalyst, it is mixed with the mesophase pitch and heat treated to obtain a spinning pitch, and then this spinning pitch is spun, infusible, and carbonized. A method for producing carbon fiber, characterized by: