JPS61138721A - Production of carbon fiber - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber meltable uniformly at the spinning temperature and having excellent spinnability, etc., by extracting coal tar pitch with a solvent, hydrogenating and heat-treating the component isoluble in the solvent, spinning and infusibilizing the product, and carbonizing or graphitizing the obtained fiber. CONSTITUTION:Coal tar pitch is optionally heat-treated e.g. at 870-420 deg.C for 0.5-20hr, and is extracted with a solvent such as tolune for 8-12hr preferably under refluxing. The solvent-insoluble component is treated e.g. at 400-470 deg.C under a pressure between 5atm and the autogeneous pressure for 10-180min in the presence of a hydrogenation solvent (e.g. hydrogenated anthracene oil), and is heat-treated at 380-470 deg.C under normal pressure introducing nitrogen gas to the system to obtain a pitch having a quinoline-insoluble content of preferably <=20wt% and an anisotropy of >=90%. the pitch is subjectd to the spinning, the infusibilization, and the carbonization or graphitization to obtain the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing carbon fiber, and more specifically,
The present invention relates to a method for producing carbon fibers, in which coal tar pitch is evaporated by a novel method, and then spun, infusible and carbonized (or graphitized) according to conventional methods.

Conventional techniques and problems In order to produce high-strength carbon fiber using pitch (refined pitch that has been removed by filtration, centrifugation, etc., including the solid content that it initially contained) as a raw material, it is necessary to It is important to increase Skt'' containing menofuose and use it as a spinning material. Therefore, when heat-treating pitch to produce mesoface pitch, the light fraction in pitch that is difficult to convert into mesoface (normally 50% of pitch ~8Qffi
It accounts for %.

In addition, "X" in the following means that unless otherwise specified, it is necessary to remove 0), which indicates 9.4 weight X". Various methods have been proposed as methods for removing such light components. However, each has its own problems.

For example, there is a method of removing light components by subjecting the pitch to a reduced pressure state at a high temperature or by subjecting it to nitrogen bubbling at a high temperature.However, in this method, the boiling point is 40
There is a drawback that the mesophase itself changes in quality at high temperatures during the removal treatment of light components of about 0 to 65 G'O, and becomes heavier and does not melt uniformly at the spinning temperature. There is also a method in which pips for spinning are obtained by removing the soluble content by extraction with a solvent such as, and heat-treating the insoluble content (JP-A-54-160427). However, this method concerns the treatment of petroleum-based pitch, which differs markedly in its physical properties from the coal tar pitch of the present invention. Therefore, when applying this extraction method to =-Lutal pitch to obtain a spinning pitch, if the membrane pitch contains the optically anisotropic component t-90% or more, preferably 100X, the overchamber condensation reaction will proceed and the spinning This results in a pitch with extremely poor thread quality.

Furthermore, there is also the problem that insoluble components obtained by separation using a solvent do not melt at the spinning temperature or do not melt uniformly. That is, this method also has serious problems that should be improved as a method for producing mesoface pitch that melts uniformly at the spinning temperature.

Furthermore, after hydrogenating the pitch with a hydrogenation solvent such as tetrahydroquinoline, hydrogenated nine tar oil.

Perform filtration and bath agent recovery distillation, and then evaporate under reduced pressure or under illumination.
A method has also been proposed in which the spinning pitch is obtained by heat treatment while removing light components under a raw gas pump (normal pressure) (Japanese Unexamined Patent Publications No. 18421/1982, Japanese Unexamined Patent Application No. 58-2
14581). The advantage of this method is that by lightening the pitch by hydrogen-donating disintegration (hydrogenated solvent) and proceeding with some hydrogenation, the exit chamber condensation reaction of the pitch is suppressed, and the pitch is uniformly bathed at the spinning temperature. It is said to be at the point where it is possible to obtain a spinning pitch that melts and has good spinnability. However, even if this method is 2, you can convert to Menface and set 4! Since heat treatment is performed at high temperature for a long time in order to remove the purchased material, the polycondensation reaction of the pitch progresses, the amount of insoluble matter in the pitch increases, and the softening point of the pitch also rises. Therefore, the hydrogenation effect of pitch that has been hydrogenated is
It was found that the amount was significantly reduced. Therefore, even if pitch with a high light content is subjected to pitch hydrogenation pretreatment, spinning pitch with poor spinnability, or pitch with a spinning temperature so high that continuous spinning is virtually impossible. ``There is a problem that only a spinning pitch of B4g mesophase can be obtained.

Means for Solving the Problems As a result of repeated research taking into account the current state of the technology as described above, the inventor of the present invention extracted coal tar pitch with a solvent under mild temperature conditions to obtain mesoface pitch. After removing the light components that are difficult to dissolve, the resulting heavy components that cannot be dissolved are subjected to hydrogenation treatment. ! In the case of heat treatment, the light components are removed in advance as solvent-soluble components, so only a small amount of light components need to be removed during heat treatment, and the degree of heat escape is low, so the effects of heat treatment are minimized. Therefore, it has been found that a pitch for producing carbon fibers which has a lower spinning temperature than conventional products, melts uniformly at the spinning temperature, and has excellent spinnability can be obtained.

That is, 1 the present invention extracts coal tar pitch that has been heat-treated or not heat-treated in advance with a solvent, hydrogenates the resulting solvent-insoluble matter, and heat-treats the resulting hydrogenated escape pitch, and the resulting heat-treated pitch is The present invention relates to a method for producing carbon fiber, which is characterized by spinning according to a method, infusible treatment, and then carbonization treatment or graphitization treatment.

In the present invention, the coal tar pitch from which the solid content has been removed may be subjected to extraction treatment with a solvent as it is, or it may be heat-treated at about 870 to 420'C for about 0.5 to 20 hours to remove the solvent-insoluble heavy content. After increasing the amount, extraction processing using @ medium may be performed. Extraction is carried out using a solvent such as benzene, toluene, tetrahydrofuran, or a mixture thereof, or a mixture of these and n-hexane at a strength of 6 to 20 times the amount of coal tar pitch, followed by reductive boiling. 8 to 12 hours at or near the lower temperature 1! It is preferable to do this once in a while. The solvent-free fraction is obtained by filtering the obtained treated product.

Next, a hydrogen scavenger is added to the obtained heavy fraction that is insoluble in a good solvent, and the mixture is hydrogenated. In this case, the heavy content is 100 to 800
% of water bulking 7-note oil, tetrahydroquinol/
, add a hydrogenated solvent such as a hydrogenated aromatic compound (anthracene, pyrene, naphthazine, etc. 2 to 6 ring aromatic compounds are made bulky), temperature 400N470" 0 degrees, pressure 6 to 100 ml. The hydrogenated bath agent is recovered and hydrogenated pitch is obtained by distilling the flit liquid obtained by filtering the hydrogenated product.

Next, the obtained hydrogenated pitch is heat treated.

The heat treatment is carried out at about 880 to 470° C. under normal pressure or under reduced pressure. When using nitrogen gas, hydrogenation geopitch 1 kl@shi, 5 ~
It is preferable to have a 4o115+1a degree blowing.

This heat treatment reduces the memface content to at least 9
A pitch with a QI of 0% or more and a QI of 20% or less can be obtained. Since the pitch has a low softening point and is bathed uniformly at the spinning temperature, it has excellent spinnability and is suitable as a raw material for producing high-strength noble fibers. If the degree of hydrogenation by the above solvent is low, the QI of the pitch is 20%.
As the softening point increases, the stringiness decreases as the yarn wears.

The spinning operation of the heat-treated pitch is performed by the known bath melt extrusion spinning method,
It may be carried out in the same manner as the blow spinning method, centrifugal spinning method, etc. For example, when performing S-melt extrusion spinning, the heat-treated pitch described above is supplied to a spinning machine, heated to 800°C to 400°C, and extruded from a nozzle under pressure with inert gas to form spinning pitch 4a fibers. Just do it.

The spinning pinch NII #1 can be infusible by a conventional method. For example, in an oxidizing atmosphere!
! Although the general conditions are a temperature of about 0° C. to 400° C. and a holding time of about 1 to 3 hours, it is also possible to adopt conditions other than these. As the intensifying atmosphere gas, saR element,
Examples include oxygen-enriched gas, air, etc., and if measures are taken to prevent deterioration of the working environment and corrosion of equipment, chlorine gas, NO gas, N02 gas, etc. may also be added. good. still.

By increasing the pressure of the oxidizing atmosphere to 0.2 klF/am".G or higher, more preferably 1.0 OLcf/cm2.G or higher, the infusibility treatment time can be greatly shortened. In this case, although it depends on the properties of the heat-treated pitch, the thickness of the spun pitch fibers, etc., under optimal conditions, it is possible to complete the infusibility treatment within an extremely short time of, for example, once per minute. It is.

The obtained infusible pitch fibers are subjected to a carbonization treatment or a graphitization treatment according to a conventional method.In the case of performing a carbonization treatment, the infusible pitch fibers are exposed to side light or exposed to an inert gas such as nitrogen gas. It is sufficient to raise the temperature to 20 to 80 minutes below and maintain it at the same temperature for about 10 to 80 minutes. Effects of the Invention According to the present invention, a spinning material containing 90% or more of mesophase that does not substantially change the purchase due to heat treatment. You get the pitch. The pitch fFi is higher than that of the conventional method.
Since it is not excessively heavy, it melts uniformly at the spinning temperature, and has excellent spinnability when producing carbon fiber, and improves the strength and other properties of the final carbon fiber. It also has excellent physical properties.

EXAMPLES The following examples will be shown to further clarify the features of the present invention. Example 1 After centrifuging coal tar to remove primary QI,
The mixture was heat-treated at 00° C. and 3 klF/am” a Q for 6 hours, and distilled under reduced pressure (400° C. in terms of normal pressure) to obtain hard pitches.

The properties of the pitch are softening point (Metcou method) = IJO
°C %B I = 28.9%, Q I = 0.6%
Next, the hard pitch was extracted with 431 times the volume of toluene at 60 to 70°C, and the toluene-insoluble matter was filtered off. The properties of the toluene-insoluble matter were BI376.
5%% Q I = s, 5 x s fixed carbon = 64
．． It's 0X.

It did not soften even at about 500°C, and carbonized at higher temperatures.

Next, 40% hydrogenated anthracene oil (aromatic index (fa) = 0.6) was added to 200% by weight of the toluene insoluble matter obtained above.
Add 0 parts by weight, 480℃, 20 kl/Cm” 6
After heat treatment at G for 80 minutes, the solid was filtered at about 200°C to separate about 40 parts of the solid from the +lJ solution. It is considered that QI and a similar fraction in the above-mentioned toluene-insoluble matter were not dissolved in the hydrogenated anthracene oil. on the other hand,
By distilling the filtrate, hydrogenated anthracene oil was recovered and hydrogenated pitch was obtained. The properties of the hydrogenated pitch are as follows: Softening point (Metcou method) = 199°O*QI = 0
．． 0%, BI=66.7%.

A spinning pitch of 94.81 was obtained by heat treatment in a salt bath at 460°C for 6 minutes while the pitch was soaked in water.
=86.8%.

The anisotropy Ikg was 5% or more (according to a polarizing microscope).

Next, the diameter (to) of the spinning pitch obtained above: Q, j
li urn, length L) = 0.41m1 (L/D
=2 Winding speed from the nozzle! Continuous spinning was performed at 300 m/min to obtain pitch fibers.

The pitch fibers were then heated in air at a rate of 5°C/min.
The temperature was raised from 0.degree. C. to 200" at a rate of 2.degree. C./min to 800"C, and the same temperature was maintained for 80 minutes for infusibility treatment.

Next, the obtained infusible pitch fibers were heated in an il atmosphere for 5 minutes.
The temperature was raised at a rate of 0°C/min and held at 1200°C for 8 minutes to form a stranded fiber. At the 1st ff, the temperature was controlled by the temperature at the nozzle surface, the temperature in the melting tank, and the discharge linear velocity. Table 82 shows the physical properties of the carbon fiber obtained in Table 82. In addition, the physical property values in Table 2 are the average of 7 samples in one shift. A membrane pitch having an anisotropy t similar to that of the spinning pitch was obtained in a yield of 4063%. However, in order to obtain the membrane pitch, it took 80 minutes at the same nitrogen injection rate (C7.51/min) and the same temperature ((450"C) as in Example 1. The property of Menface pitch is its softening point (Metcou method)
= 812°C, QI = 82.0%, BI = 98.0%, anisotropy was 95% or more (as measured by a polarizing microscope).

The results corresponding to Tables 1 and 2 in Example 1 are shown as Tables 8 and 4.

Table 8 Table 4 (that's all)

Claims (2)

[Claims] (1) Coal tar pitch that has been previously heat-treated or not heat-treated is extracted with a solvent, the resulting solvent-insoluble matter is hydrogenated, and the resulting hydrogenated pitch is heat-treated,
A method for producing carbon fibers, which comprises spinning the obtained heat-treated pitch according to a conventional method, subjecting it to an infusible treatment, and then subjecting it to a carbonization treatment or a graphitization treatment. (2) The method for producing carbon fibers according to claim 1, wherein the heat-treated pitch has a quinoline insoluble content of 20% by weight or less and an anisotropy amount of 90% or more as measured by polarized light microscopy.