JPS6081319A - Infusibilization of pitch fiber - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber having excellent properties, in shortened infusibilization time, by applying cobalt bromide to the surface of a pitch fiber obtained by the melt-spinning of carbonaceous pitch, and infusibilizing the fiber in an oxidizing gas atmosphere. CONSTITUTION:Carbonaceous pitch such as ethylene tar pitch is melted at a temperature higher than the softening point by 30-80 deg.C, extruded from a nozzle having a diameter of 0.1-0.5mm., and wound at a rate of 100-200m/min to obtain a pitch fiber. Cobalt bromide is applied to the fiber by spraying, etc. at a rate of 0.1-20wt%, preferably 5-10wt%, based on the pitch fiber, and the fiber is infusibilized at <=400 deg.C, preferably 200-350 deg.C. The objective carbon fiber can be produced by carbonizing and graphitizing the above fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making pitch fibers infusible.1. A method for producing carbon fibers entirely as pitch gold raw material is cheaper than raw materials and has a high carbonization yield, compared to polyacrylonitrile-based methods. In addition, it is possible to shorten the processing time and cost in heat treatment processes such as infusibility, carbonization, and graphitization after spinning, making the price advantage over the IJ system even clearer. can.

Until now, various catalysts or promoters have been studied to shorten the infusibility treatment time, including metal salts, ammonium salts,
Inorganic acids, halogens, nitrogen oxides, etc. have been proposed, but nothing satisfactory has yet been obtained in terms of their infusibility promotion effect or the physical properties of the final product, carbon fiber. For example, if pitch fibers are contact-treated with an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, and then subjected to a complete infusibility treatment, some may show an effect of promoting infusibility, but the physical properties of the final product, carbon fiber, may deteriorate. It has the disadvantage of being

As a result of extensive research, the present inventors have found that when pitch fibers are infusible in an oxidizing gas atmosphere, by applying all cobalt bromide to the surface of the pitch fibers in advance, the infusibility time can be significantly shortened, and an excellent It has been discovered that carbon fibers with excellent performance can be obtained.

That is, the present invention relates to a method for making pitch fibers infusible, which comprises completely applying cobalt bromide to the surface of pitch fibers obtained by melt-spinning carbonaceous pitch, and then treating the pitch fibers to make them infusible in an oxidizing gas atmosphere. .

The present invention will be explained in detail below.

The carbonaceous pitch used in the present invention includes various pitches such as coal tar pitch, coal-based pitch such as SRC, petroleum-based pitch such as ethylene tar pitch, and decant oil pitch, or synthetic pitch, but petroleum-based pitch is particularly preferred. It's sad.

The pitch has been completely modified, for example, the pitch has been treated with a hydrogen donor such as tetralin, the pitch has been hydrogenated under a hydrogen pressure of 20 to 350 kg/-, the pitch has been modified by xp during heat treatment,
Various modified pitches, such as those modified by p-modification by means such as solvent extraction, or modified by an appropriate combination of all of these methods, are also considered carbonaceous pitches in the present invention.

That is, the carbonaceous pitch of the present invention is used to collectively refer to precursor pinches that can form pitch fibers entirely.

The carbonaceous pitch of the present invention may be an optically isotropic pitch or an optically anisotropic pitch.

When the pitch is optically isotropic, the reflectance is 9.0~
Those exhibiting a value within the range of 11.0 inches are preferred. Here, the reflectance is measured by embedding the pitch in a resin such as acrylic resin, polishing it, and measuring it in air using a reflectance measuring device.

Optically anisotropic pitch refers to a pitch that is normally 340 to 300 m
It is a pitch that completely contains an optically anisotropic phase (so-called membrane phase) obtained by heat treatment at 450° C., and a pitch with a membrane phase content of 5 to 100% is particularly preferable.

The carbon pitch used in the present invention has a softening point of 240 to 400.
A temperature of 1:1 is preferable, and a temperature of 260 to 300°C is preferable.

Pitch fibers can be obtained by melt-spinning the carbonaceous pitch by a known method. For example, carbonaceous pitch is melted at a temperature 30 to 80 degrees Celsius higher than its softening point and extruded through a nozzle with a diameter of 0.1 to 0.5 mm.
The entire pitch fiber is obtained by winding at ~2000 m/min.

The present invention requires that after applying cobal bromide)']l- to the pitch fiber surface, an infusibility treatment is performed in an oxidizing gas atmosphere.

Cobalt bromide) The method of applying it to the pitch fiber surface is not particularly limited, but for example, cobalt bromide is dissolved in an organic solvent such as methanol, ethanol, or acetone, or in water, and this solution is sprayed or applied on the pitch fiber surface. , is preferably achieved by drying off the solvent. The amount of cobalt bromide applied is 0 to pitch fiber.
．． It is 1 to 2 Qwt%, preferably 0.5 to 10wt%.

Cobal bromide on the surface)? The applied pitch fibers are then treated to be infusible in an oxidizing gas atmosphere. The infusibility treatment is usually carried out at a temperature of 400°C or lower, preferably at a temperature of 150°C or lower.
-380°C, more preferably 200-350°C. If the treatment temperature is too low, the treatment time becomes long, and if the treatment temperature is too high, phenomena such as fusing or consumption of the pitch fibers occur, which is not preferable.

As the oxidizing gas, one or more oxidizing gases such as oxygen, ozone, air, nitrogen oxide, halogen, or sulfur dioxide gas are usually used.

The infusible pitch fibers are then subjected to carbonization treatment or further graphitization treatment in an inert gas atmosphere to obtain carbon fibers.

Carbonization treatment is usually carried out at a temperature of 800 to 2000°C, and the treatment time generally required for carbonization is 0.1 minute to 10 hours. Furthermore, if graphitization is performed completely, the temperature is 2000 to 350.
It is carried out at 0 C for usually 1 second to 1 hour. Furthermore, during carbonization or graphitization, a slight load or tension may be applied to the object to be treated, if necessary, in order to prevent shrinkage, deformation, etc.

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 A petroleum precursor pitch containing 80% of an optically anisotropic phase and having a softening point of 280° C. was completely melt-spun to obtain pitch fibers with an average yarn diameter of 13 μm. 3.5 weight l for this pitch fiber,
% of cobalt bromide was applied as a 5% by weight methanol solution, and after being completely dried, it was heated in oxygen at 50°C/i to 3400°C to make it infusible, and then carbonized at 1000°C to produce carbon fibers. did. The obtained carbon fiber has an average thread diameter of 10μ and an elastic modulus of 60TON/mn? , tensile strength 250
It was 9/m-.

Example 2 A petroleum precursor pitch containing 65% of total optically anisotropic phase and having a softening point of 252° C. was melt-spun to obtain pitch fibers with an average yarn diameter of 11 μm. To this pitch fiber, 7.2% by weight of cobalt bromide was applied as a 12% by weight aqueous solution, which was dried and then heated to 300°C at 80°C/- in oxygen to make it infusible. Carbon fibers were produced by carbonization treatment at 1000°C. Obtained carbon fiber'z 2500
When graphitized at ℃, the obtained graphitized fiber had an average thread diameter of 9μ and an elastic modulus of 70TON/my? , tensile strength 310
It was V4/n-.

Example 3 Optically isotropic petroleum precursor pitch with a reflectance of 10.3% and a softening point of 260° C. was melt-spun to obtain pitch fibers with an average yarn diameter of 12 μm. 1.7% by weight based on this pitch fiber
Cobalt bromide of 3 wt. Manufactured. The obtained carbon fiber had an elastic modulus of 10 TON/rnrl and a tensile strength of 98 Kg/mn.
? Met. When this carbon fiber k was graphitized at 2500°C, the physical properties of the graphitized fiber obtained were an elastic modulus of 60 T.
ON/mtr? , tensile strength 250 to 97 mrr? And ivy.

Example 4 An isotropic petroleum precursor pitch having a reflectance of 9.8% and a softening point of 270° C. was melt-spun to obtain pitch fibers with an average yarn diameter of 11 μm. To this pitch fiber, 2.4% by weight of cobalt bromide was applied as an 8% by weight aqueous solution, and after drying, the temperature was raised to 300°C in an order of 80°C in oxygen to make it infusible. Carbon fibers were produced by carbonization treatment at i, ooo°C. The elastic modulus of the obtained carbon fiber is 1t TON/m
rr? , tensile strength is 102 Kf/mrr? Met. When graphitized with this carbon fiber K2500C,
The physical properties of the graphitized fiber obtained were an elastic modulus of 50 TON/material and a tensile strength of 270 Kq/m.

Comparative Example 1゜The pitch fiber used in Example 1 was heated in oxygen at 50℃/- for 3
When the temperature was raised to 40°C, the fibers were fused during the infusibility treatment and could not be isolated as fibers.

Comparative Example 2゜To the pitch fiber used in Example 1, 2.4% by weight of cobalt acetate was applied as an 8% by weight aqueous solution, and after being completely dried, the temperature was raised to 340°C at 50°C/boiler in oxygen. In both cases, the fibers deteriorated and were damaged during the infusibility treatment, making it impossible to obtain excellent graphitized fibers.

Comparative Example 3゜The pitch fiber used in Example 1 was brought into contact with nitric acid for 5 minutes, and then infusible, carbonized, and graphitized by the method described in Example 1. The physical properties of the graphitized fiber were as follows. Elastic modulus 301'ON/m-1 Tensile strength 120 Ks+/mr
r? It was nothing more than

Claims (1)

[Claims] A method for infusibleizing pitch fibers obtained by melt-spinning carbonaceous pitch in an oxidizing gas atmosphere, characterized in that the pitch fibers are made infusible after applying cobalt bromide to the surface of the pitch fibers. Method.