JPH0260992A - Production of pitch - Google Patents

Abstract

PURPOSE:To obtain a pitch substantially freed of impurities, having a high softening point and being excellent as a raw material for the production of carbon fiber by heating a heavy oil obtained by hydrocracking pulverized coal under specified conditions. CONSTITUTION:Coal is finely pulverized to 100mesh or finer, and hydrocracked in a hydrogen atmosphere under conditions of an elevated pressure and a temperature of 600-1000 deg.C, and the formed heavy oil is heated at 320-360 deg.C. The coal used need not be specified in kind, and any of anthracite, bituminous coal, brown coal lignite, peat can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing pitch for carbon fibers, which substantially does not contain quinolinated components, has uniform properties, and has a high softening point.

Prior art and its problems Carbon fibers made from pitch are broadly classified into petroleum-based carbon fibers and coal-based carbon fibers.

Coal-based carbon fibers are obtained by heat-treating coal tar produced during coal carbonization at high temperatures, or by distilling light fractions from coal liquefied oil, using pitch with a softening point of about 80 to 120°C as a starting material. There is. However, this pitch has the following problems.

(a) The properties of coal tar obtained by carbonization etc. vary greatly depending on the raw coal and reaction conditions. Therefore, the pitch obtained by further heat-treating this pitch also has inconsistent properties, contains many insoluble components, has a low softening point, and has a very wide molecular weight distribution.

(b) Methods for removing impurities from the above pitch include heating the pitch to about 250 to 300°C and filtering it, or mixing the pitch with an organic solvent such as an aliphatic solvent and filtering it. . However, these methods cause severe clogging and wear and tear of the filtration filter; a large amount of diluting solvent is required; and additional steps such as solvent addition, extraction, separation and purification are required, and the overall process Processing costs increase due to increased complexity.

(C) As a method of increasing the softening point of the above-mentioned pitch, heating bi-sochi in contact with a gas such as air or an inert gas is a simple and commonly used method. In this method, increasing the severity of the heat treatment increases the softening point of the pitch. However, when the severity of the heat treatment is increased, the amount of quinolinine dissolved increases and forms coke that adheres to and grows on the reactor walls, interfering with the heat treatment operation.

Therefore, a method of adding a polymerization accelerator and heat treatment has been proposed as a method of increasing the softening point of pitch while suppressing the formation of quinoline-soluble components. However, when the softening point of pitch is low, Requires a polymerization accelerator.

(d) In order to reduce the molecular weight of the pitch and make it uniform, and at the same time reduce the quinolinated content, it is also possible to mix expensive hydrogen or a solvent with hydrogenation ability and perform heat treatment.
It is being done. However, this method also has the disadvantage of high processing costs.

Means for Solving the Problems In view of the problems of the prior art as described above, the present inventor has
As a result of extensive research, we have found that when heat-treating pi-sochi obtained by hydrogenolyzing pulverized coal under specific conditions, it contains virtually no impurities (such as quinolinine and metals).
It was discovered that pitch can be obtained with a high softening point, and that this pitch has excellent properties as a raw material for producing carbon fibers.

That is, the present invention provides the following method: (1) A method for producing pi-sochi, which comprises pulverizing coal, then hydrogenolyzing it, and heat-treating the produced heavy oil.

■ In the method for producing pitch described in the above item 1, coal is finely pulverized to 100 mesh or less, and then hydrogenated under pressure in a hydrogen atmosphere at a temperature of 600 to 1000°C to produce heavy oil. A method of heat treatment at 320-360°C.

The type of coal used in the present invention is not particularly limited, and anthracite, bituminous coal, lignite, lignite, peat, and the like can be used. In particular, a great advantage of the present invention is that low-grade coal such as lignite, lignite, and peat can be used.

In hydrogen cracking, coal is finely pulverized to less than 100 mesh at a temperature of 600 to 1000°C and a pressure of 1 to 100 kg/cJ・G.
It is preferable to carry out the heat treatment under moderate conditions. The reaction oil thus obtained is subjected to distillation according to a conventional method,
The light fraction is distilled off, and the remaining fraction with a boiling point of 400° C. or higher is obtained as pitch. The softening point of this distilled pitch is
Although it varies depending on the type of raw coal and the thermal decomposition conditions, it is usually about 80 to 120°C, which is about the same as that of existing coal tar.

This distilled pitch was heated at a temperature of 320 to 36°C under atmospheric pressure in a nitrogen stream without filtration and without adding a polymerization accelerator.
It is subjected to a slow heat treatment at about 0° C. for about 1 to 3 hours. By this treatment, it is possible to obtain a thermally modified pitch that does not contain impurities (quinolinated content, metals, etc.) and has a high softening point of about 230 to 250°C and is suitable for spinning.

By spinning, infusible, and carbonizing this thermally modified pitch according to a conventional method, high-quality carbon fibers can be obtained.

Effect of the invention According to the present invention, the following remarkable effects are achieved.

(1) Low-grade coal such as peat, lignite, and brown coal can also be used as raw materials.

(2) By thermally decomposing coal powder in a hydrogen atmosphere, thermal decomposition and hydrogenation treatment are performed at the same time, so the resulting heavy oil contains substantially no quinoline solvent due to the hydrogenation effect. However, other metals remain in the unreacted coal. Therefore, a thermally modified pitch with extremely low impurity content is finally obtained.

(3) Since the obtained heavy oil has extremely uniform properties, it is easy to fractionate it by distillation, and the molecular weight of the obtained distilled pitch can be reduced to 300% without depending on the type of raw material or thermal decomposition conditions. It can be adjusted to a narrow width of about ~500.

(4) The obtained distilled pitch can be directly subjected to thermal modification without separating and removing insoluble matter or adding a polymerization accelerator.

(5) Although the thermal modification process can be simplified in this way, the obtained thermally modified pitch has a high softening point and is suitable as a raw material for carbon fibers.

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Example 1 Australian coal pulverized to 100 mesh or less was thermally decomposed in a hydrogen atmosphere at a temperature of 800° C. and a pressure of 35 kg/cJ@G to obtain a reaction oil.

A light fraction was distilled off from the reaction oil by a distillation operation to obtain distilled pitch having a softening point of 83° C. and a quinoline solubility of 0%. This reaction oil had uniform properties and was easily fractionated by distillation.

Next, the above-mentioned distilled pitch was heat-treated in a nitrogen stream at atmospheric pressure and at a temperature of 360°C for 11 hours.
A heat-treated pitch with a softening point of 247°C was obtained.

By heating this pitch to the softening point +50°C and spinning it with a rotary spinning machine, it is made infusible at 300°C in an air atmosphere for 3 hours, and then carbonized at 1200°C for 5 minutes in a nitrogen atmosphere. Strength 76kg/mm2, thread diameter 14.8
am, elastic modulus 4, 0 ton/mrn2, elongation 1.
9% carbon fiber was obtained.

Example 2 Coal powder similar to that used in Example 1 was thermally decomposed in a hydrogen atmosphere at a temperature of 800° C. and a pressure cuff of 0 kg/cJ-G to obtain a reaction oil.

Light fractions were removed from the reaction oil by distillation to obtain distilled pitch with a softening point of 87°C and a quinoline solvent content of 0%. This reaction oil also had uniform properties and was easily fractionated by distillation.

Next, the above-mentioned distilled pitch was heat-treated in a nitrogen stream at atmospheric pressure and at a temperature of 360°C for 1 hour to obtain heat-treated pitch with a softening point of 250°C.

By heating this pitch to the softening point +50°C and spinning it with a rotary spinning machine, it is made infusible at 300°C in an air atmosphere for 3 hours, and then carbonized at 1400°C for 5 minutes in a nitrogen atmosphere. Strength 125kg/mm2, thread diameter 6.6
μm, elastic modulus 5, 3 ton/mm2, elongation 2.
4% carbon fiber was obtained.

Example 3 American coal pulverized to 100 mesh or less was thermally decomposed under hydrogen atmosphere and atmosphere at a temperature of 700° C. and a pressure cuff of 0 kg/cJ-G to obtain a reaction oil.

Light fractions were distilled off from the reaction oil by distillation to obtain distilled pitch with a softening point of 97° C. and a quinoline solubility of 0%. This reaction oil had uniform properties and was easily fractionated by distillation.

Next, the above-mentioned distilled pitch was heat-treated in a nitrogen stream at atmospheric pressure and at a temperature of 350°C for 3 hours to obtain heat-treated pitch with a softening point of 240°C.

By heating this pitch to the softening point +50°C and spinning it with a rotary spinning machine, it is made infusible at 300°C in an air atmosphere for 3 hours, and then carbonized at 1400°C for 5 minutes in a nitrogen atmosphere. Strength 75kg/mm2, thread diameter 15.2
ttm, elastic modulus 3, 4 ton/mm", elongation 2
．． 2% carbon fiber was obtained.

Example 4 British coal pulverized to 100 mesh or less was thermally decomposed in a hydrogen atmosphere at a temperature of 900° C. and a pressure of 42 kg/cTl-G to obtain a reaction oil.

Light fractions were distilled off from the reaction oil by distillation to obtain distilled pitch with a softening point of 110° C. and a quinoline solubility of 0%. This reaction oil had uniform properties and was easily fractionated by distillation.

Next, the above-mentioned distilled pitch was heat-treated in a nitrogen stream at atmospheric pressure and at a temperature of 350°C for 3 hours to obtain heat-treated pitch with a softening point of 250°C.

This heat-treated pitch was heated to the softening point +50°C, spun using a rotary spinning machine, and then infusible at 300°C in an air atmosphere for 3 hours, and carbonized at 1400°C for 5 minutes in a nitrogen atmosphere. , strength 79kg/mm2, thread diameter 1
Carbon fibers having an elastic modulus of 5.9 ttm, an elastic modulus of 3.4 ton/mm2, and an elongation of 2.3% were obtained.

Comparative Example 1 Coal tar at a temperature of 400°C and a pressure of 15kg/cJ-G
After primary heat treatment for 5 hours, distilled pitch with a softening point of 125°C (a fraction with a boiling point of 500°C or higher) was obtained.

A heat-treated pitch with a softening point of 170° C. was obtained by heat-treating this pitch without filtration (and without adding a polymerization accelerator) in a nitrogen stream at atmospheric pressure and at a temperature of 360° C. for 3 hours.

As shown in Table 1 below, the obtained heat-treated pitch has a low softening point and a high quinoline soluble (QI) content.
Thread breakage was severe and spinning was practically impossible.

Table 1 softening point ('C) QI (%) distilled pitch heat treated pitch (that's all)

Claims (2)

[Claims] (1) A method for producing pitch, which comprises pulverizing coal, then hydrogenolyzing it, and heat-treating the resulting heavy oil. (2) In the pitch manufacturing method according to the first claim,
Coal is finely pulverized to 100 mesh or less and hydrogenolyzed under pressure in a hydrogen atmosphere at a temperature of 600 to 1000°C,
A method of heat-treating the produced heavy oil at 320-360°C.