JPS6065090A - Preparation of pitch for carbon fiber spinning - Google Patents

Abstract

PURPOSE:To prepare a pitch for spinning capable of forming high strength carbon fiber, by heat treating a carbonaceous raw material in the presence of an oxidizing gas. CONSTITUTION:A carbonaceous raw material is heat treated at about 350-500 deg.C for 2min-50hr in the presence of an oxidizing gas (e.g. air or oxygen) to prepare a pitch for spinning having an optically anisotropic phase content of about 30% or higher. In the heat treatment, it is preferable that an inert gas such as nitrogen be blown in the early stage and an oxidizing gas be blown in an amt. of about 10l or larger (in terms of oxygen) per kg of pitch after the start of formation of meso phase. The resultant pitch is spun and spun fiber is oxidized and carbonized into carbon fiber and, when necessary, is further converted to graphite fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carbon fR6aR6 pitch, and more particularly, to a method for producing a spinning pinch useful for producing pitch-based carbon fibers having excellent properties.

Carbon fiber is a material with extremely high specific strength and specific modulus.
Recently, it has been attracting attention as a filler fiber for high-performance composite materials. This carbon fiber contains polyacrylonitrile carbon fiber made from polyacrylonitrile, heavy oil,
Pinch carbon al! made from carbonaceous materials such as tar and pitch! There is a meaning.

By the way, when carbonaceous raw materials such as heavy oil, tar, and pitch are heated to a temperature of 350 to 500°C, small particles with particle sizes ranging from several microns to several hundred microns exhibit optical anisotropy under polarized light. It is known that when spheres are formed and further heated, these small spheres grow and coalesce, and eventually the entire body exhibits optical anisotropy. This anisotropic structure is composed of a layered structure of high-molecular aromatic hydrocarbons produced by the thermal-gravitational reaction of carbonaceous originals and is oriented in a Mfl manner45, and is thought to be a precursor of the graphite crystal structure. ing.

A heat-treated product containing such an anisotropic structure is usually called mesophase pitch9, and after melt-spinning it through a nozzle, it is insolubilized, carbonized, and optionally graphitized to form pitch. It is possible to obtain carbon fibers with high properties.

Although this pitch-based high-performance carbon fiber has various advantages over polyacrylonitrile-based carbon fiber, such as low raw material cost, high yield in the carbonization process, and high fiber elastic modulus, Pitch-based carbon fibers produced from menphasic pitch obtained by well-known methods generally have many disadvantages in terms of strength compared to polyacrylonitrile-based carbon fibers.

The inventors of the present invention have made extensive studies to improve these drawbacks and provide a spinning pitch that yields pitch-based carbon fibers with improved strength. discovered that the object could be achieved by performing the heat treatment in the presence of an oxidizing gas, and based on this knowledge, the present invention was completed.

That is, the present invention is characterized in that the heating treatment is performed in the presence of an oxidizing gas on the same day that the carbonaceous raw material is heat-treated to form a complete spinning pitch containing an optically anisotropic phase. A method for producing spinning pitch for carbon fibers is provided.

Examples of the carbonaceous raw material used in the method of the present invention include coal-based coal tar, coal tar pitch, coal liquefied products, and petroleum-based heavy oil, tar, and pitch. These carbonaceous raw materials usually contain impurities such as free carbon, undissolved coal, and ash, and these impurities can be removed by well-known methods such as filtration, centrifugation, or static sedimentation using a solvent. , it is desirable to remove them in advance.

The carbonaceous raw material may still be pretreated, for example, by the following method.

That is, (1) the carbonaceous raw material is heated to a temperature of 350 to 500°C.
.

Pressure normal pressure ~ 10 to 2/c#! G for about 0.5 to 20 hours to obtain a heat-treated product containing an optically anisotropic part, usually at least 30%, preferably at least 50%, particularly preferably at least 70%. and an aromatic oil such as anthracene oil having a boiling point or initial boiling point of 150° C. or higher, 9 aromatic oils 1 to 3 per 1 part by weight of the heat-treated product.
(2) A method of contacting the carbonaceous raw material or the aromatic oil soluble component in the above (1) with a compound such as tetralin, decalin, tetrahydroquinoline, hydrogenated In addition to soluble carbonaceous raw materials or aromatic oils, quinoline, naphthalene oil, anthracene oil, etc., which can be easily converted into hydrogen-donating solvents, by adding a solvent such as and an iron-based or molybdenum-based catalyst, and under pressure of hydrogen gas.
After hydrogenation at a temperature of 60 to 500°C, the solid matter is removed by filtration if necessary, and the solvent is removed by distillation if necessary to obtain a residue. You may also do so.

In the method of the present invention, the carbonaceous raw material or the pretreated carbonaceous raw material is usually heated at 350 °C in the presence of an oxidizing gas.
The spinning pitch containing the optically anisotropic phase is obtained by heat treatment at a temperature in the range of ~500°C, preferably 380-450°C for 2 minutes to 50 hours, preferably 5 minutes to 5 hours.

Specifically, this heat treatment is performed using the oxidizing gas as it is or at a concentration of 0.5 to 30 volumes, preferably 0.
This is carried out by appropriately diluting with an inert gas such as nitrogen or argon to a volume of 5 to 20 volumes, particularly preferably 0.5 to 5 volumes, and blowing into the carbonaceous raw material.

Dilution with this inert gas is preferable because it can prevent a sudden increase in the softening and melting temperature of the spinning pitch.

Examples of the oxidizing gases include air, oxygen, chlorine, sulfur, carbon dioxide, nitrogen oxides, and sulfur oxides. Air and oxygen are preferred.

This blowing of the oxidizing gas or its diluent gas may be carried out during the entire period of the heat treatment or at any desired period, but it is particularly effective to carry out the blowing during the period when the menphase is being formed. In other words, the blowing of an oxidizing gas or its diluent gas accelerates the increase in the softening and melting temperature of the carbonaceous raw material during heat treatment, and the degree of this increase increases the earlier the blowing occurs. It is preferable to blow in an inert gas such as nitrogen, and then blow in an oxidizing gas or its diluent gas at a time when the menphase is being formed.

The optimal amount of oxidizing gas to be used varies depending on the type of gas, but generally speaking, the larger the amount of any gas, the better the spinning pitch that will give carbon fibers with greater strength. However, if the amount is too large, the softening and melting temperature of the spinning pitch becomes too high, making spinning difficult. On the other hand, if the amount is too small, the effect of improving strength cannot be expected. For example, when blowing air or oxygen, or a gas made by diluting them with an inert gas, the amount is usually 1 kg per spinning pitch obtained by heat treatment, converted to oxygen in the standard state.
0 or more, preferably 10 to 3000 t, particularly preferably 30 to 100 t.

The spinning pitch thus obtained usually has an optical anisotropy ratio of 30% or more, preferably in the range of 50 to 99%. The optical anisotropy ratio of the spinning pitch as used in the present invention is a value determined as the area ratio of a portion exhibiting optical anisotropy in a spinning pinch sample under a polarizing microscope at room temperature. Specifically, a spinning pitch sample crushed to several angles was embedded almost entirely on the surface of a resin with a diameter of approximately 2 (7) according to a conventional method, and after polishing the surface, the entire surface was thoroughly examined using a polarizing microscope ( It is determined by observing the sample under a magnification of 100 times) and measuring the area ratio of the optically anisotropic portion to the entire surface of the sample.

The spinning pitch thus obtained by the method of the present invention can be spun, infusible, carbonized, and optionally graphitized according to conventional methods to provide carbon fibers or graphite fibers with improved strength.

Generally, if an oxidizing gas is present during heat treatment of pitch, the resulting spinning pitch will exhibit female graphitizability, that is,
It is thought that even when carbonized graphitization is performed, properties are imparted that make it difficult to convert into good graphitized crystals.
I), C Carbon, 16.439 (19
78) On the other hand, in the production of carbon fibers, when the viscosity and softening melting temperature of the spinning pitch increases, the spinning temperature rises and a heat treatment reaction occurs during spinning, causing the pitch to change in quality. It was believed that such conditions should be avoided when manufacturing. However, unexpectedly, when the pitch obtained by heat treatment in the presence of an oxidizing gas according to the method of the present invention is used as spinning pitch, carbon fiber with improved strength and elongation without any particular decrease in spinnability. It turns out that you can get

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Coal tar pitch (Q work = 13
Add 800 f of hydrogenated aromatic oil and 450 f of hydrogenated aromatic oil while stirring under autogenous pressure.
The temperature was raised to .degree. C., maintained for 1 hour, and then immediately cooled to room temperature. This treated product was filtered under reduced pressure using qualitative filter paper, and the filtrate was further distilled under reduced pressure to obtain pitch 5381 as a residue.

Next, this residual pitch 622 was heat-treated at 420° C. for 60 minutes to obtain spinning pitch 337. At that time, N2 gas was blown into the pitch at a rate of 6 tons/minute for the first 10 minutes, and a mixed gas of air and N2 gas mixed at a rate of xty minutes and 5 tons/minute, respectively, was blown into the pitch for the remaining 50 minutes. This means that 380% of standard oxygen was blown into the resulting spinning pitch iK9'l').

The anisotropy ratio of the spinning pitch obtained in this way is approximately 7
It was 0%, and QI = 35 weight ratio, weight - 88 weight ratio. This spun pitch is evaporated and melt-spun to obtain pitch fibers, and then the pitch fibers are
After infusibility at 0°C, carbonization was performed at 1400°C in a nitrogen atmosphere to obtain carbon fibers. This carbon fiber had an average diameter of 9.3 μm, a tensile strength of 28.2 tons/d, and an elongation of 1.83%. Furthermore, this carbon fiber was graphitized at 2800° C. in an argon atmosphere to obtain a graphite fiber. This graphite fiber 1 has an average diameter of 8.5μ, 27.8 tons/c,
It had a tensile strength of 1 and an elongation of 0.5%.

Comparative Example 1 In the same manner as in Example 1, 6 per minute was
A spinning pitch of 307 was obtained by heat treatment at 420° C. for 60 minutes while blowing only N2 gas at t. The anisotropy ratio of the obtained spinning pitch is about 70%, and Q knee 1
2% by weight, B process = 88% by weight.

This spinning pitch was melt-spun to obtain pitch fibers, which were then infusible and carbonized in the same manner as in Example 1 to obtain carbon fibers. This carbon fiber has an average diameter of 10.5μ, and has an average diameter of 16.4μ/
It had a tensile strength of tri and an elongation of 1.23%.

Furthermore, this carbon fiber was graphitized in the same manner as in Example 1 to obtain graphite fiber. This graphite fiber has an average diameter of 9.6μ and 1.2
It had a tensile strength of 2 tons/Cd and an elongation of 0.5%.

Example 2 The residual pitch 60F of Q knee 0.8 weight ratio and B work = 28 weight ratio obtained according to Example 1 was heat-treated at 420° C. for 85 minutes to obtain a spinning pitch of 302.

At that time, for the first 75 minutes, 6 tons of N2 gas was supplied per minute, and for the remaining 10 minutes, air and N2 gas were supplied at 1 la/min and 5 t/min, respectively.
The mixed gas was blown into the pitch at a rate of t/min. This means that 701 liters of standard oxygen was blown into each I kg of spinning pinch obtained. The anisotropy ratio of the obtained spinning pitch was approximately 90%, QI = 25% by weight, and BI = 92% by weight. This spinning pitch was melt-spun to obtain pinch fibers, and then in the same manner as in Example 1,
Carbon fibers were obtained by infusibility and carbonization. This carbon fiber had an average diameter of 9.0μ, a tensile strength of 1.29.5 tons/tri, and an elongation of 1.81%.

Comparative Example 2 Heat treatment was carried out in the same manner as in Example 2, except that only 6 tons of N2 gas was blown into the residue pinch per minute. The anisotropy ratio of the obtained spinning pitch was approximately 90%, QI = 19 weight ratio, and BI = 90 weight ratio.

This spinning pitch was melt-spun to obtain pitchle cut fibers, which were then infusible and carbonized in the same manner as in Example 1 to obtain carbon fibers. This carbon fiber has an average diameter of 11.6μ and 21.0 tons/
c++! It had a tensile strength of 1.40% and an elongation of 1.40%. Patent applicant: Director of the Agency of Industrial Science and Technology Hirobe Yoda (and one other person) Sub-agent: Akira Agata Continued from page 1 0 Inventor: Kouhei Okuyama, Yokohama 0 in the Kamoshida-cho Research Institute, Midori-ku, Ichimori-ku Author: Akio Kato 100 lots in the Kamoshida-cho Research Institute, Midori-ku, Yokohama City 100 lots in the Mitsubishi Chemical Industries, Ltd. Comprehensive procedure amendment document August 3, 1980 Manabu Shiga, Commissioner of the Japanese Patent Office1, Indication of the case, Patent Application No. 172142 of 1982, Title of the invention, Method for producing spinning pitch for carbon fibers3, Person making the amendment Relationship with the case Patent applicant: Chiyoda, Tokyo 1-3-1 Kasumigaseki-ku (114) Director of the Institute of Industrial Science and Technology 1) Hirobe (1 person)
4. Designated Agent: 807-1 Nonoshita, Shuku-cho, Tosu City, Saga Prefecture Yoshibe Shimizu, Director of the Kyushu Industrial Technology Research Institute, Agency of Industrial Science and Technology5. Sub-Agent: 6. Date of amendment order. Number of 0 8, Subject of amendment Details of the invention in the specification 11A & Explanation column 9
, Contents of the amendment (1) "Insolubilization" in the bottom line of page 2 of Book I3 will be corrected to "infusibility."

(2) “38o1” in the 8th line of the 10th beno [31S
Corrected to NJ.

Claims (1)

[Claims] ] In the production of a spinning pinch containing an optically anisotropic phase by heat-treating a carbonaceous raw material, 1. A method for producing spinning pitch for carbon fibers, characterized in that the heat treatment is performed in the presence of an oxidizing gas. 2. The method according to claim 1, wherein the oxidizing gas is air or oxygen. 3 Spinning pitch I obtained by heat treatment of oxidizing gas
3. The method according to claim 2, wherein the amount of oxygen per kg is ioz or more as standard oxygen.