JPS58156023A - Production of carbon fiber - Google Patents

Abstract

PURPOSE:Coal is depolymerized in a hydrocarbon solvent under hydrogen pressure, the product is subjected to distillative separation to give a coal depolymerization product, then the product is made into fibers, infusibilized and carbonized to produce carbon fibers of uniform quality and high strength. CONSTITUTION:Coal crushed into particles of appropriate sizes is mixed with a hydrocarbon solvent for depolymerization to form a slurry and a catalyst is added to the slurry. The mixed slurry is heated in a temperature range from 300 to 500 deg.C under hydrogen pressure to effect dissolution, then insoluble solids are separated by filtration. The remaining coal solution is heat-treated at 350-450 deg.C for 1-320min under 1-70mm.Hg pressure to separate the distillates, thus giving a coal depolymerization product. The product is made into fibers, infusibilized with air and calcined at higher temperatures to effect carbonization and graphitization, thus producing the objective carbon fiber.

Description

[Detailed Description of the Invention] In terms of raw materials, the production of can be roughly divided into methods using natural fibers or synthetic fibers as raw materials, methods using petroleum pitch or coal tar pitch as raw materials, and methods using coal depolymerized products as raw materials. Can be classified. The present invention is a method for producing carbon fiber using coal depolymerized material as a raw material. The coal depolymerized product in the present invention is a coal depolymerized product produced by depolymerizing coal in a solvent under hydrogen pressure.

When using natural fibers or synthetic fibers such as polyacrylonitrile as raw materials, which is one of the conventional methods for producing carbon fibers,
When using petroleum pitch or coal tar pitch as a raw material, problems include the high price of raw material fiber and the low carbonization yield of raw material fiber. In addition, in the case of coal tar pitch, an operation for separating and removing insoluble solids is required.

Moreover, the composition of petroleum pitch or coal tar pitch becomes significantly non-uniform due to heat treatment, making it difficult to maintain uniform properties of carbon fibers made from these pitches.

Therefore, when petroleum pitch or coal tar pitch is used as a raw material, several complicated steps are required to modify it into a pitch with desirable properties as a raw material for carbon fiber production, and as a result, the carbon fiber production process < (IJ becomes coarse. Moreover, the properties of the modified pitch cannot be said to completely satisfy the necessary conditions as a raw material for producing carbon fibers.

The operating conditions for the infusibility process, which is one of the carbon fiber manufacturing processes, are largely controlled by the softening point of the carbon fiber raw material.By raising the softening point of the carbon fiber raw material, the infusibility treatment of the spun fibers becomes easier. This is well known. This is because the infusibility treatment is air oxidation, and in order to increase the oxidation rate,
This is based on the fact that it is more advantageous to carry out the non-melting treatment at a higher temperature.

One of the controlling factors for the softening point of the coal depolymerized product is the amount of residual depolymerization solvent, and the other factor is the degree of polymerization or molecular weight. For example, by tightening the conditions for distillation and recovery of the depolymerization solvent, it is possible to obtain a depolymerized coal having a high softening point and suitable as a raw material for producing carbon fibers. Here, the depolymerization solvent refers to a solvent used to depolymerize coal and convert it into a coal depolymerized product.

Coal depolymerized products are more susceptible to oxidation than petroleum pitch and coal tar pitch because they have an alicyclic structure inherent in coal or introduced into the coal depolymerized products by hydrogenation during depolymerization. However, coal depolymerized products are not completely free from problems. In other words, in the production of coal depolymerized products using conventional production methods, the coal depolymerized products produced under mild depolymerization conditions have a relatively high softening point, and the operation to increase the softening point of the carbon fiber raw material is comparatively difficult. This can be easily achieved under mild solvent recovery conditions, as shown in JP-A-55-90620. However, recently, coal depolymerization conditions have become more demanding.
This is due to economic demands such as the use of low-grade coal, which has poor solubility but low price, as a raw material, and the need to advance depolymerization to increase the yield of oily components. This is also due to operational requirements such as preventing line blockages and facilitating the separation of insoluble solids in coal depolymerization plants.

Stricter depolymerization conditions specifically include lowering the coal concentration in the slurry, increasing hydrogen pressure, using catalysts, increasing depolymerization temperature, increasing depolymerization time, and using solvents with improved hydrogenation ability, e.g. This refers to the use of recovered solvents or solvents that have been hydrogenated in the presence of a hydrogenation catalyst in the same process.

The coal depolymerized product obtained under such severe depolymerization conditions becomes a highly hydrogenated coal depolymerized product. Its properties are lower overall in molecular weight than depolymerized products obtained under conventional mild depolymerization conditions. For example, if the solvent fraction is 1~, BI (benzene 4 soluble)! and a decrease in THF-T (detrahydrofuran insoluble matter)-° was observed. Also, when viewed as a raw material for carbon fibers, the softening point is reduced.

This kind of coal depolymerized product hydrogenated in Koryeo was published in Japanese Patent Application Publication No. 5
5-90620, that is, when removing hydrocarbon solvents by distillation, it is difficult to obtain the softening point desired as a carbon fiber raw material under conditions where the distillation bottom temperature is 350°C or less. Therefore, it is necessary to keep the holding temperature and temperature increase rate low during the infusibility treatment.

This not only increases processing time but also often causes fusion and the like.

The present invention provides a method for producing a carbon fiber raw material from such highly hydrogenated coal depolymerized product.

As a result of extensive research on highly hydrogenated coal depolymerized products, the present inventors have found that highly hydrogenated coal depolymerized products have comparatively excellent thermal stability even under K conditions. The present invention was achieved by discovering that it is possible to make the solvent recovery conditions stricter, and that it is possible to reform coal depolymerized products with desired physical properties because rapid sequestration condensation polymerization does not occur. This is what led to this. By carrying out the present invention, even if the coal depolymerized product is produced under advanced coal depolymerization conditions, it is possible to obtain a coal depolymerized product as a raw material for carbon fibers that has good mobility and is easily infusible. be able to. The properties of carbon fiber made from this raw material are uniform and high in strength, and the carbonization yield relative to the spinning raw material is also high.

That is, the present invention processes coal under hydrogen pressure in the presence or absence of a catalyst, and then converts it into a coal-based solvent, a recovered solvent recovered by the present invention, etc., a highly hydrogenated solvent, or a highly hydrogenated recovered solvent. By subjecting the depolymerized coal produced by depolymerization inside the carbon fiber to substantially mild decomposition and condensation polymerization, and removing the solvent and decomposed oil by distillation at the same time, the material and properties of the coal as a raw material for carbon fiber can be improved. This method of producing carbon fibers is characterized in that the coal depolymerized product is melted and spun, and then subjected to infusibility treatment and carbonization treatment.

The coal decomposition 1 compound targeted by the present invention is the depolymerization of bituminous coal, bituminous coal, lignite, brown coal, lignite, and grass coal under hydrogen pressure in the presence of a catalyst or in the absence of pores 1 in W + polymerization agent. It was manufactured by

Further, the catalyst targeted by the present invention is a hydrogenation catalyst mainly composed of iron, or a Co-Mo catalyst which is a common coal liquefaction catalyst.
Halokenization catalysts such as Ni-Mo based catalysts, ZnCl2 Refers to certain solicar alumina, alumina, zeolite, synthetic zeolite, etc.

In addition, the target depolymerization solvent is the middle oil fraction of coal yarn, that is, the region with a boiling point range of 200 to 400°C, and the recovered oil recovered after using this fraction in the coal depolymerization process, or the oil that has been prepared in advance under hydrogen pressure. This is a depolymerization solvent that has been hydrogenated in the temperature range of 300 to 500°C without a catalyst or using the hydrogenation catalyst described above.

The present invention will be explained in further detail.

The boiling point range of the above-mentioned coal pulverized to an appropriate particle size and a hydrocarbon depolymerization solvent, such as coal carbonization tar, is 2 (] 0 to 4).
00℃ distillate or the solvent already used in this process and recovered in the recovery process are mixed so that the coal/depolymerization solvent ratio (weight basis) is 1:1 to 1:10 to make a slurry. shall be as follows. In some cases, 0.3 to 10 wt% of catalyst is added to this slurry. This mixed slurry was heated under hydrogen pressure of 3 to 300 μg/cr/IG.
Melt by heating in a temperature range of 500°C. Hydrogen pressurization is effective in depolymerizing the coal component into the depolymerization solvent, and the coal dissolution rate is significantly reduced. The use of recovered solvents or (9) further hydrogenated solvents is equally effective, and catalysts added for various purposes are effective in accelerating dissolution and depolymerization reactions. It is.

The heating time is set so that the slurry has a viscosity that can be sufficiently filtered, and although it varies depending on the amount of coal or solvent catalyst added, it is usually 10 to 240 ml. With the above processing,
After the soluble components of the coal are sufficiently dissolved, undissolved residues are separated and removed using, for example, a filter or a centrifugal separator. The obtained filtrate or supernatant was heated to 350°C to 450°C.
heat-treated at a temperature range of It is preferable to perform heat treatment and distillation in a short time under cumulative pressure, but specifically, the degree of vacuum should be 1 to 70, which is the industrial standard.
wnHgabs, and the heat treatment and the holding time at the distillation temperature are carried out at 11 to 320 -, but preferably 1 to 380 -
5-20 wnHg ab in a temperature range of 400℃
It is advantageous to carry out the process under a pressure of about 5 to 80 JIIm. If the temperature is less than 350°C (10), not only will the holding time become longer, but it will also be difficult to raise the softening point, and if it exceeds 450°C, there is a risk that rapid polycondensation will proceed in the distillation bottom. , generation of insoluble carbon precursors may be observed. Needless to say, the production of insoluble carbon precursors not only adversely affects spinning but also causes a decrease in the strength of carbon fibers. These operations remove low molecular weight 1-1 low softening point components in the distillation bottom and lower the softening point to 200 to 3.
0〇I℃, BI 45-70wt%, T)l F/l 15
~40wt%, and the insoluble solid content is 0.5wt% or less.

Here, the softening point was measured using a micro melting point measuring device under a nitrogen stream. Moreover, BI complies with JIS-2425. T
HF-I was measured under the reflux temperature of TI (F) in the same manner as BI.The insoluble solid content was determined according to JIS-M-8801.
Compliant with.

If the softening point of the coal depolymerized product is less than 200°C, BI (11) less than 45 wt%, and THF-115 wt%, it will take a long time to make the fibers infusible, and the softening point will be 3()0°C.
, B I 70 wt%, THF-140 wt%, melt spinning is difficult and special equipment is required for melt spinning.

Furthermore, if the insoluble solid content exceeds 0.5 wt%, continuous spinning will be hindered, and voids will increase in the carbon fibers, resulting in a decrease in strength, making them unsuitable as raw materials for carbon fibers.

The coal depolymerized product is then spun using a conventional melt spinning method. The spun fiber is 03, NOx.

Although the infusibility treatment time can be shortened by pretreatment with SOx, a halide oxidizing agent, etc., in the present invention, the temperature is started to rise from room temperature to the same temperature as the softening point of the coal depolymerized product, or about 130℃. The temperature is raised to a temperature higher than 30°F and infusible treatment is performed by air oxidation. The temperature increase rate during infusibility treatment is 0.5
℃/more than 20 degrees Celsius/below.

After the infusibility treatment, the fibers are placed under tension or without tension.
Carbon fibers can be obtained by raising the temperature to 1000° C. in an inert gas atmosphere at a temperature increase rate of less than 40° C. (12)/cm and firing and carbonizing it. Further, graphite fibers can be obtained by further firing and graphitizing carbon fibers at a temperature of 2000° C. or higher.

Examples are shown below, but the present invention is not limited thereto.

Example 1 Australian average lignite was oxidized with 3x 1st: (vehicle volume basis) hydrogenated recovery solvent (hydrogenated in the main disintegration process and recycled 12 times) and as a catalyst. 1.5 wt % of iron ore (loess) containing iron hydrate as a main component was added, and the reaction temperature was maintained at 450° C. for 60 hours under hydrogen pressure of 150 and 9/iG. This coal bath solution was filtered by a pressure filtration method (3 Kg/crA G ), and was separated into an insoluble substance containing iron ore, ash in lignite, and undissolved lignite, and a filtrate (coal solution).

This filtrate was held at a bottom temperature of 390° C. for 20 hours under reduced pressure of 8 wnHg a ba to recover the depolymerization (13) solvent. After the holding time had elapsed, the distillate was immediately cooled. The obtained distillate, that is, the coal depolymerized product, has a softening point of 235°C, a BI of 56.5 wt%, and a T)IF-I of 18.
．． 6 wt%, and the ash content was 0.05 wt%. This was melt-spun at 280° C., heated from room temperature to 270° C. in an air stream at a rate of 3° C./degree, and maintained at 15 mm in the same FA laboratory. Then, in a nitrogen stream, the temperature was raised to 1000°C at a heating rate of 10°C/10°C, and then 301° at the same temperature.
dR was maintained to obtain carbon fibers. The yield of this carbon fiber was 77.7 wt% based on the coal depolymerized product, the fiber diameter was 8 to 10μ, and the tensile strength was 13.2 ton/ca.

Example 2 Australian lignite was mixed with 5-fold hydrogenated recovered oil that had been previously hydrogenated using a hydrogenating insect medium, and 2 wt % of a hydrogenation catalyst (Co-Mo catalyst) was added. This mixed slurry was held and dissolved at a reaction temperature of 430° C. under a hydrogen pressure of 200 Kf/cAG (14), and then the catalyst and undissolved residue were separated and removed using a filter. A liquid (coal molten tL) was obtained.

The solvent recovery conditions for the filtrate were as follows: 8 + mn Hgabs, bottom temperature 410° C., and 20-order maintenance. No formation of carbon precursors was observed in the obtained coal depolymerized product,
It was optically isotropic throughout. The shredded coal depolymerized product has a softening point of 260°C, a BI of 63.5 wt%, and a THF-
I is 25.6wt1! , the ash content was 0.03 wt%. This was melt-spun at 305°C, and the temperature was raised from room temperature to 270°C in an air stream at a rate of 44°C/H.

After holding at the same temperature for 30 minutes, it was replaced under a nitrogen flow, and then heated at a temperature increase rate of 4.4°C/10 degrees under the same nitrogen flow.
The temperature was raised to 00°C and maintained at the same temperature for 30 orchards. The obtained carbon fiber has a fiber diameter of 8 to 10μ and a tensile strength of 14.1.
ton/ctl.

Example 3 Domestic bituminous coal was made into a slurry by adding four times the amount of coal tar medium oil, and then held at 410° C. for 30 minutes under a hydrogen pressure of 60 g (15)/cnI G to obtain a coal solution. This was separated into a supernatant and a residue using a centrifuge. 3 wt% of silica-alumina catalyst was added to this supernatant liquid, and hydrogen pressure was again increased to 100 Kg/c.
The pressurizer reaction temperature of rl G was maintained at 450° C. for 30 minutes. Thereafter, filtration was performed using a filter to obtain a filtrate.

The solvent recovery conditions for this filtrate were maintained at 430° C. and 1 ON at 5 mm Hgabs. The obtained coal deweighted product had a softening point of 230°C, a BI of 56.5 wt%, and a THF-
1 is 20.2 wt%, and the ash content is 0. Oi wt%. In addition, no carbon precursors were observed in the de-weighted coal, and it was completely optically isotropic. After melt-spinning this coal depolymerized product at 270°C,
The temperature was increased at 1° C. in an air stream at a rate of 3° C./m.

After holding at the same temperature for 60 minutes, the temperature was then raised to 1000°C at a heating rate of 3°C/low under a nitrogen stream, and held at the same temperature for 30 m. The resulting carbon fibers had a diameter of 8-1° (16) μ and a tensile strength of 15.6 tons/ctil.

Example 4 The properties of a depolymerized coal produced in a coal road polymerization plant using Australian lignite as a raw material do not have properties suitable as a raw material for carbon fibers, with a softening point of 156°C and a BI of 38.
．． 6 wt%, and THF-I was 5.3 wt%. This was melted at 250°C under a nitrogen stream, stirred, heated to 400°C at a rate of 2°C/decoy at 15 mm Hgaba, and kept at the same temperature for 10 minutes to obtain a redistilled product. Ta. The yield of this redistillate is 85.2 wj point at 237°C and BI is 57.8 w with respect to the raw material coal depolymerized product.
t%, THF-I. This redistilled charcoal depolymerized product is softened, has a weight of 20.1wt, and has an ash content of 0.06.
wj%.

□ Also, no formation of carbon precursors was observed. After melt spinning this at 2851:
The temperature was raised from room temperature to 260℃ in an air stream, and the temperature was increased to 15℃ at the same temperature.
It was held for a minute. This infusible fiber was further heated to 1000 (17)° C. at a heating rate of 10° C./m and held at the same temperature for 30 minutes to obtain carbon fiber. The yield of this carbon fiber based on the raw material coal γfE polymer was 65.9%, the fiber diameter was 8 to 10μ, and the tensile strength was 1
The ship had a capacity of 14.5 tons/crl.

Comparative Example 1 Filtrate (coal solution) in Example 1 total 8+mnHgabs
When the temperature was raised to 300°C and maintained at 60°C, 14% of the M polymerization bath agent was recovered, and the resulting coal decomposition product had a softening point of
BI is 43.3 wt%, 'l'' HF-■ is 10.1
wt%, and the ash content was 0.05 wt%.

When this coal depolymerized product was melt-spun at 250°C, fusion between fibers was observed.

Comparative Example 2 Using the coal depolymerized product produced in the coal depolymerization plant in Example 4, the temperature was raised at a temperature increase rate of 1 °C / 1 °C to the distillation temperature of 470 °C at 20 un Hgabs. After arrival, it was cooled down. Fine carbon precursors were generated in this double-distilled coal cracked product, making continuous melt spinning impossible.

Judgment issued by 1 person Mitsui Coke Ashi Co., Ltd. Agent Patent Attorney Hide Hirazawa E1 (19)

Claims (1)

[Claims] 1) After treating coal under hydrogen pressure in the presence or absence of a hydrocarbon solvent and a catalyst, the coal solution from which insoluble solids have been removed is heated at a temperature of 350°C to 450°C. Holding time: 1 minute to 320 minutes, pressure: 1 mmHg at the same temperature
A method for producing carbon fibers, in which a coal depolymerized product obtained by heat-treating under conditions of abs to 70 mmHgabs and simultaneously distilling and separating distilled components is infusible after melt-spinning, and then carbonized or graphitized. 2. The coal depolymerized product according to claim 1 has a softening point of 200°C to 300°C, a benzene insoluble content of 45 wt% to 7 Owt, and a tetrahydrofuran insoluble content of 15 wt% to 7 Owt. 40 wt% and an insoluble solid content of 0.5 wt% or less.