JP2982406B2 - Method for producing spinning pitch for carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a spinning pitch for carbon fibers, and more particularly to a method for producing a spinning pitch which gives carbon fibers exhibiting high strength and high elastic modulus.

[0002]

2. Description of the Related Art Since carbon fiber and graphite fiber have very high specific strength and specific elastic modulus, they are used as reinforcing materials for various composite materials such as fishing rods, sports equipment such as golf shafts, artificial hands, and the like.
It is widely used from medical instruments such as prostheses to aviation and spacecraft components such as aircraft wings and space shuttle doors.

[0003] The types of carbon fibers and graphite fibers having high characteristics are roughly classified into polyacrylonitrile (PAN) type and pitch type. In general, pitch type carbon fiber and graphite fiber are produced from coal, petroleum and the like as raw materials. ing. As is well known, carbonaceous materials such as heavy oil, tar,
Upon heating to 500 ° C., small spheres exhibiting optical anisotropy under polarization with a particle size of several to several hundred microns are formed in these materials. Then, when further heated, these small spheres grow and coalesce, and as a result, the whole becomes optically anisotropic. This anisotropic composition is obtained by stacking and orienting high molecular aromatic hydrocarbons formed by a thermal polycondensation reaction of a carbonaceous raw material, and is regarded as a precursor of a graphite crystal structure.

[0004] Such a heat-treated product is passed through a spinneret,
It has been proposed as a raw material for pitch-based high-performance carbon fibers having characteristics such as high strength and high elastic modulus by melt spinning, infusibilizing, carbonizing and, in some cases, graphitizing. In particular, when producing a spinning pitch containing a large amount of an optically anisotropic phase, JP-A-54-55625 and JP-A-57-4292 are useful.
4. It is already known to produce a spinning pitch by performing a heat treatment while stirring a carbonaceous raw material or further blowing an inert gas or the like as disclosed in JP-A-58-168687, JP-A-58-168687, and the like. Have been.

[0005]

However, in any of these various spinning pitches, conventional spinning pitches contain a low softening point component. If the pitch containing such a low softening point component is melt-spun and then infusibilized and carbonized to produce a carbon fiber, the increase in the elastic modulus of the carbon fiber obtained due to the presence of the low softening point component is not sufficient. In order to compensate for the shortage of the elastic modulus, the firing temperature must be increased, and when the elastic modulus is increased by increasing the firing temperature, the 0 ° compressive strength of the obtained carbon fiber is reduced, and the high-performance carbon fiber Shows a tendency that is difficult to achieve. The inventors of the present invention have conducted intensive studies in order to solve such a problem. As a result, the optically isotropic carbonaceous raw material is heat-treated at a temperature of 380 ° C to 450 ° C, and the optically anisotropic spinning is performed. Found that a spinning pitch that gives high-performance carbon fibers can be obtained by blowing an inert gas into the isotropic carbonaceous raw material at a certain speed or higher when manufacturing a pitch for use. did.

That is, an object of the present invention is to provide a spinning pitch which can be spun and which can exhibit a high modulus of elasticity by firing at a relatively low temperature and which can produce pitch-based carbon fibers having a high 0 ° compression strength. The purpose is to provide a way to gain.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to blow an inert gas into a carbonaceous material while heating the optically isotropic carbonaceous material at a temperature of 380 to 450 ° C. In a method for producing a carbon fiber spinning pitch having an optically anisotropic content of 95% by volume or more, the blowing rate of inert gas is at least 2.5 Nm ³ / hour or more per kg of carbonaceous raw material. It is easily achieved by being.

Hereinafter, the present invention will be described in detail. The carbonaceous raw material used in the present invention is not particularly limited as long as it is usually a carbonaceous raw material used to obtain a spinning pitch.For example, coal-based coal tar, coal tar pitch, coal liquefaction, petroleum-based pitch, for example, FCC oil, coker oil or a distillation residue thereof, or an aromatic resin produced by polycondensation reaction of naphthalene, anthracene, or the like with a catalyst or a formalin derivative, and having a benzene-insoluble content of 95% by weight or less, preferably 70% by weight or less, more preferably Is 5-4
5% by weight and a quinoline-insoluble matter of 40% by weight or less, preferably 30% by weight or less, more preferably 20% by weight or less.

Above all, in order to obtain high-performance carbon fibers, the content of aromatic carbon which is easily graphitized must be 80 wt%.
As described above, it is preferable to use a carbonaceous raw material of 90 wt% or more. In addition, the quinoline-insoluble matter of such a carbonaceous raw material may be composed of fine particles such as coke, carbon black, and ash, and when these are mixed into the spinning pitch, the spinnability is reduced, and the strength of the obtained carbon fiber is undesirably reduced. Therefore, it is desirable to remove the quinoline-insoluble matter of the carbonaceous raw material in advance by a preliminary treatment such as static separation, and then provide it to the production of the spinning pitch of the present invention. Further, the carbonaceous raw material from which the quinoline insolubles have been removed is further treated with tetralin,
Includes iron-based compounds and molybdenum as solvents with decalin, tetrahydroquinoline, solvents such as quinoline, naphthalene oil, and anthracene oil that can be easily converted to hydrogen-donating solvents with or together with hydrogen-donating solvents for hydrogenated aromatic oils. The mixture with the supported or unsupported catalyst is hydrogenated at 360 to 500 ° C. under hydrogen gas pressure, and then the solid content is removed by filtration or the like, and if necessary, the solvent is removed by distillation or the like. After the treatment, it may be subjected to the production of the spinning pitch of the present invention.

[0010] The carbonaceous raw material which has been subjected to the above-mentioned quinoline insoluble content removal or hydrogenation treatment is further treated with 380-45.
0 ° C, preferably 400 ° C to 430 ° C, reduced pressure to 10 kg
/ Cm ² · G, preferably 10 mmHg to normal pressure for 20 minutes to 10 hours, preferably about 1 to 6 hours.
2.5 Nm ³ / hour or more, preferably 10 N / kg
A pitch for spinning is manufactured by performing heat treatment while blowing an inert gas of Nm ³ / hour or more into the pitch. The pitch thus obtained contains almost no low softening point component, and when these pitches are melt spun, infusibilized and carbonized to produce carbon fibers, the elastic modulus is unlikely to increase, When the firing temperature is increased to increase the modulus of elasticity, the 0 ° compression strength decreases.

[0011] The spinning pitch for high-performance carbon fiber produced by such a method contains an optically anisotropic phase in an amount of 95% by volume or more, and has a shear viscosity of 200 poise at a temperature of 30 poise.
It is preferable to select a heat treatment temperature and a heat treatment time so as to be 0 ° C. to 370 ° C., preferably 310 ° C. to 350 ° C.
That is, a relatively long heat treatment time is required at a low temperature, and a short heat treatment time is selected at a high temperature. The spinning pitch produced by this method has a very low content of low molecular weight components having a low softening point, a toluene soluble content of 10% by weight or less, preferably 5% by weight or less, and a small amount of high molecular weight components produced. And a quinoline-insoluble content of 40% by weight or less, preferably 30% by weight or less.
% By weight or less.

[0012]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the examples unless it exceeds the gist. Example 1 (Example 1) A mixture of coal-based coal tar pitch 100 parts, creosote oil 100 parts, iron oxide 5 parts and sulfur 2.4 parts, excluding quinoline-insoluble solids, was continuously added to an autoclave equipped with a stirrer. Supply, hydrogen pressure 150kg / cm ²・
G, hydrogenation treatment at a temperature of 470 ° C. and an average residence time of 2 hours. After filtering the treated product to remove the iron catalyst and the like, the solvent was distilled off under reduced pressure to obtain an optically isotropic hydrogenated pitch.

[0013] The hydrogenated pitch under normal pressure, hydrogenated pitch 1kg
Was heated at 430 ° C. for 120 minutes while blowing nitrogen at a blowing rate of 4.5 Nm ³ / hour. The optically anisotropic phase of the obtained spinning pitch was 95%. This spinning pitch has a shear viscosity of 200 poise and a temperature of 335 °.
C. This was melt spun and the resulting yarn diameter was 10 μm.
Pitch fibers in air up to 310 ° C. for 160
After raising the temperature in a minute and infusibilizing the mixture, the mixture was heated at 1000 ° C. for 60 minutes in argon and then at 2000 ° C. for 30 minutes.
A carbon fiber was obtained by performing a two-stage carbonization treatment of heating for minutes. Table 1 shows the results of measuring the physical properties of the carbon fiber according to the single fiber tensile test method specified in JIS-R-7601.

Further, the infusible fiber was heated at a temperature shown in Table 1 for 1 hour.
The carbon fiber was carbonized and the physical properties of the carbon fiber were measured according to ASTM-D3410.
Table 1 also shows the results measured according to the 0 ° compressive strength test method specified in Table 1.

(Example 2) 1 kg / kg of hydrogenated pitch
Example 1 except that heat treatment was performed at 410 ° C. for 210 minutes while blowing steam corresponding to a blowing rate of 2 Nm ³ / hour.
A spinning pitch was obtained in exactly the same manner as described above. The optically anisotropic phase was 100% and the temperature at which the shear viscosity was 200 poise was 325 ° C. This was performed in exactly the same manner as in Example 1 to obtain a carbon fiber. Table 1 shows the measurement results of the physical properties of the carbon fiber.

(Comparative Example) 1. 1 kg of hydrogenated pitch
18 at 430 ° C. while passing ⁵ Nm ³ / hour of nitrogen.
A spinning pitch was obtained in the same manner as in Example 1 except that the heat treatment was performed for 0 minute. 95% of the optically anisotropic phase of the obtained spinning pitch
Was 345 ° C. at a shear viscosity of 200 poise. This was performed in exactly the same manner as in Example 1 to obtain a carbon fiber.
Table 1 shows the measurement results of the physical properties of the carbon fiber.

[0017]

According to the present invention, a spinning pitch which gives a carbon fiber capable of exhibiting a high elastic modulus and a high 0 ° compression strength can be produced by a simple method.

[0018]

[Table 1]

Continuation of front page (56) References JP-A-63-258982 (JP, A) JP-A-62-161888 (JP, A) JP-A-59-164386 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) C10C 3/02 C10C 3/04 C10C 3/10

Claims (2)

(57) [Claims] 1. An optically isotropic carbonaceous raw material of 380
An inert gas is blown into the carbonaceous raw material while heating at a temperature of from 450 ° C to 450 ° C, and the content of the optically anisotropic substance is 95%.
In the method for producing a spinning pitch for carbon fiber of at least volume%, the blowing speed of the inert gas is set to a value of
A method for producing a carbon fiber spinning pitch, wherein the spinning pitch is at least 2.5 Nm ³ / hour or more per kg. 2. The method according to claim 1, wherein the blowing rate is 10 Nm ³ / hour or more per 1 kg of the carbonaceous raw material.