JPS60110925A - Manufacture of high-performance carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having extremely high strength and high modulus, by subjecting an acrylonitrile fiber to the flame-resisting treatment, and carbonizing the treated fiber in a specific atmosphere at a specific rate of temperature increase under elongation. CONSTITUTION:A synthetic acrylonitrile fiber is subjected to the flame-resisting treatment in an oxidizing atmosphere, and carbonized in an oxidizing atmosphere containing a hydrogen halide gas. The carbonization is carried out at the peak temperature of >=1,000 deg.C, at the rate of the temperature increase of 200- 3,000 deg.C/min in the temperature range of 300-1,000 deg.C, under the condition to keep the elongation ratio of the fiber to -4-+25% in the carbonization process. The atmosphere for the carbonization process is preferably a combination of hydrogen chloride, oxygen and nitrogen. EFFECT:Even the surface treatment of the carbon fiber can be carried out simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for producing high-performance carbon fibers having high strength and high modulus of elasticity from acrylonitrile-based synthetic fibers.

(b) Prior Art Generally, when producing carbon fibers from acrylonitrile synthetic fibers, flame-resistant fibers obtained by heat treatment in an oxidizing atmosphere at 200 to 300 °C are heated to carbon fibers at a higher temperature in an inert atmosphere. There are known methods of oxidation treatment.

To date, much research has been carried out to obtain carbon fibers with higher performance, and some results have been achieved. It is known for its strength and high modulus.

However, it is difficult to obtain carbon fibers with high strength and high modulus. As is generally known, the strength of carbon fiber is at a maximum temperature of 1000 to 1500
This is because the highest value is obtained in the carbonization treatment at .degree. C., and decreases at higher temperatures, but the elastic modulus increases as the carbonization temperature increases.

It is known that applying an appropriate heating rate and elongation operation under specific conditions during carbonization treatment contributes to improving the performance of carbon fibers.
8-292, etc., and the expansion operation is described in Japanese Patent Application Laid-open No. 5
Although this method is disclosed in Japanese Patent No. 4-147222, etc., it has not yet achieved sufficient effects.

In addition, a method using hydrogen halide gas as the carbonization treatment atmosphere is disclosed in Japanese Patent Publication No. 47-1G36,
Although these methods are disclosed in Japanese Patent No. 7-40575, etc., these methods have not yet achieved sufficient effects.

The purpose of the present invention is to provide high performance carbon fibers with high elasticity and high modulus.

(d) Structure of the Invention The method for producing high-performance carbon fibers according to the present invention involves carbonizing acrylonitrile-based synthetic fibers at a maximum temperature of 1000°C or higher after flame-retardant treatment in an oxidizing atmosphere.
The temperature increase rate in the temperature range of 0°C to 1000°C is 200°C/min to 3000°C/min, the elongation rate during carbonization is 14% to 25%, and the carbonization process is performed using halogen. It is characterized by being carried out in an oxidizing atmosphere containing hydrogen chloride gas.

(E) Embodiment The acrylonitrile synthetic fiber used in the present invention is a fiber made of a polymer containing acrylonitrile 90]Ti in an amount of % or more. If it is 10% by weight or less, conventionally known monomers copolymerizable with acrylonitrile, such as unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, esters of these acids, vinyl chloride, vinyl acetate, Styrene, acrylamide, diacetone acrylamide, methacrylamide, α-chloroacrylonitrile, allylsulfonic acid, etc. can be advantageously used as the partner component to be copolymerized with acrylonitrile.

Conventionally known methods are used for the flameproofing treatment in the present invention, but generally the acrylonitrile synthetic fiber is heat treated at 200 to 300°C in an oxidizing atmosphere. At this time, it is more preferable to perform an appropriate elongation operation.

In the carbonization treatment in the present invention, the maximum temperature of carbonization treatment is 300℃ or higher and 1000℃ or higher.
Temperature increase rate of 200℃/min or more in the following temperature range3
000°C/°C min or less. 200℃
If the heating rate is less than 3000℃/min, defects will easily occur inside the fiber, making it impossible to obtain high-performance carbon fiber.
If the heating rate exceeds 1 minute, troubles such as fiber bundle breakage will occur due to rapid thermal decomposition reaction.

In addition, the elongation rate during carbonization treatment should be increased from 14% to 25%.
It is necessary to do the following. If the elongation rate is less than -4%, the internal orientation of the fibers will not improve, so high-performance carbon fibers will not be obtained, and if the elongation rate exceeds 25%, problems with fiber bundle breakage will occur.

Although the above-mentioned operations during carbonization treatment improve the strength and elastic modulus compared to the untreated ones,
The strength and modulus contemplated in this invention cannot be achieved. In the present invention, in addition to the operations described above, it is necessary to carry out the carbonization treatment in an oxidizing atmosphere containing hydrogen halide gas.

Oxidizing atmosphere containing hydrogen halide gas can be used even if diluted with inert gas, but hydrogen halide gas is 0.1% by volume or more, and oxidizing gas is 0.05 to 5% by volume.
, the remainder is preferably an inert gas. However, it is not particularly limited to this. Hydrogen halide gases include hydrogen chloride, hydrogen fluoride, hydrogen bromide, etc. Oxidizing gases include oxygen, air, carbon dioxide, water vapor, etc. Inert gases include nitrogen, argon, helium, etc. , hydrogen, etc. can be used.

Among these, hydrogen chloride,
Preferably, a combination of oxygen and nitrogen is used.

Conventionally, carbonization treatment is performed in an atmosphere containing as little oxidizing gas as possible, such as oxygen, and it has been thought that the presence of oxygen reduces the performance of carbon fibers. However, in the present invention, the carbonization treatment after the flameproofing treatment is performed in an oxidizing atmosphere containing hydrogen halide gas, and a feature of the present invention is that high-performance carbon fibers having much higher strength and higher elastic modulus than conventional ones are manufactured. has.

All carbonization treatments in the method of the present invention can be performed in a single furnace, which is advantageous from the viewpoint of operability and economy. However, if a furnace is added due to the introduction of graphitization treatment to further improve productivity or achieve a higher elastic modulus, an atmosphere different from that used in the present invention may be used for the added furnace. You can also do it.

(f) Effects of the Invention As described above, the present invention provides a special atmosphere as described above in carbonization treatment in which individual operations such as heating rate and elongation operation or a combination thereof cannot produce sufficient effects. By using this method, it has become possible to produce high-performance carbon fibers that have much higher strength and modulus of elasticity than conventional methods.

Furthermore, in the present invention, by using an oxidizing gas in the carbonization treatment, the glabella shear strength, which is an important factor when using carbon fibers as a reinforcing material for a composite abrasive material, was improved. This means that the present invention also has the excellent effect of simultaneously performing surface treatment on carbon fibers.

(g) Examples The present invention will be explained in more detail by examples below.
The present invention is not limited to this.

The strength and elastic modulus of carbon fiber in the following examples are JISR7.
It was measured by the strand test method specified in 601.

Example 1 An acrylonitrile polymer fiber bundle consisting of 6000 filaments with a single yarn fineness of 1.3 denier was heated at 250°C.
The fibers were heat-treated in air for 1 hour while being given an elongation rate of 12% to obtain flame-resistant fibers. This flame resistant fiber has an elongation rate of 0%
The carbonization treatment was carried out by heating to a maximum temperature of 1350°C and staying at 1350°C for 2 minutes. At this time, 300℃
The temperature increase rate in the temperature range above 1000℃ is 90℃.
The temperature was set at 0°C/min. With the above conditions being the same, the proportions of hydrogen halide gas, oxygen gas, and nitrogen gas are the volume percentages listed in Table 1.
Table 1 shows the strength and elastic modulus of carbon fibers obtained by carbonization treatment. These results show that high-performance carbon fibers having high strength and high elastic modulus can be obtained by performing carbonization treatment in an oxidizing atmosphere containing hydrogen halide gas.

Table 1 □□□□□□□■ Example 2 Carbonization elongation rate at 4 in Example 1 Table 1 is 13%
Table 2 shows the strength and elastic modulus of carbon fibers obtained by performing the same treatment except that the heating rate in the temperature range of 300 ° C to 1000 ° C was set to the values listed in Table 2. . These results show that high-performance carbon fibers having high strength and high elastic modulus can be obtained when the heating rate is in the range of 200° C./min or more and 3000° C./min or less.

Table 2 Example 3 The strength and elastic modulus of carbon fibers obtained by performing all the same treatments except that the carbonization elongation rate in column 4 in Table 1 of Example 1 was changed to the value listed in Table 3. It is shown in Table 3. These results show that high-performance carbon fibers having high strength and high modulus of elasticity can be obtained when the carbonization elongation rate is in the range of 14% to 25%.

Table 3 Example 4 The carbon fiber bundle obtained in item 4 in Table 3 of Example 3 was impregnated with epoxy resin (Epicote 828) to create a prepreg, which was laminated and cured by heating to produce a composite material molded product. It was created. The glabella shear strength of the obtained composite material molded article was measured and found to be 9.1 kg/m+''. This value is comparable to the value of commercially available surface-treated carbon fibers.

Claims (1)

[Claims] When acrylonitrile-based synthetic fibers are flame-resistant treated in an oxidizing atmosphere and then carbonized at a maximum temperature of 1 ooo"C or higher, the heating rate in the temperature range of 300"C to 1000"C is set to 200"07 minutes or more and 3000"C or more. "C/min or less, the elongation rate during carbonization treatment is 14% or more and 25%
A method for producing a high-performance carbon fiber as follows, and the carbonization treatment is performed in an oxidizing atmosphere containing hydrogen halide gas.