JPS61119768A - Oxidation treatment of carbon fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for surface treatment of script fibers by vapor phase oxidation.

[Conventional technology]

Carbon fibers generally have excellent specific strength and specific elasticity and are used as reinforcing fibers for composite materials, but in order to fully express the mechanical properties of the fibers, it is necessary to appropriately control the adhesive strength at the interface with the matrix. There is a need to.

In order to control the adhesive strength between carbon fibers and the matrix, methods that improve the surface properties of the fibers are generally used. There are methods of introducing functional groups with high properties.

A method of heating carbon fibers in an oxidizing atmosphere to increase their affinity with the matrix was published in Japanese Patent Publication No. 45-12.
In addition, Japanese Patent Publication No. 47-24976 discloses that the oxidation reaction can be accelerated by carrying out the oxidation reaction under light irradiation. However, when surface treating carbon fibers by heating them in an oxidizing atmosphere, the reaction is rapid and the multi-fibers are seriously damaged, making it difficult to control the reaction. On the other hand, when the reaction temperature is low, the reaction rate is slow, so it is not suitable for use as an industrial surface treatment method. Special Public Service 1977-24
Although the method disclosed in Japanese Patent No. 976, in which light irradiation is used in combination to promote the reaction, has been somewhat effective, it has the disadvantage that it tends to cause heterogeneous reactions.

Furthermore, Japanese Patent Publication No. 47-55022 discloses a method of surface treating carbon fibers in an air stream containing excited and activated oxygen.
This is proposed in Japanese Patent Application Laid-Open No. 49-87891.

These methods allow the reaction to occur homogeneously over the entire fiber bundle without causing treatment unevenness, but the oxidation reaction is extremely slow, so even when combined with the light irradiation method, it is not possible to promote an effective oxidation reaction, resulting in a low oxidation level. At present, it is difficult to obtain carbon fibers that have undergone a high surface treatment.

[Problem that the invention seeks to solve]

Therefore, the present inventors did not reduce the strength of the carbon fiber matrix,
The present invention was achieved as a result of extensive research aimed at finding a gas-phase oxidation reaction for carbon fibers that allows the oxidation reaction to proceed uniformly at relatively low temperatures.

Means for Solving Problems c] The present invention resides in a method for treating carbon fibers, which is characterized in that the carbon fibers are surface-treated in an oxidizing atmosphere containing ozone while being irradiated with light.

The oxidizing atmosphere used in carrying out the present invention is an atmosphere containing ozone, especially air containing ozone,
In this oxidizing atmosphere, oxygen is excited by light irradiation, making it possible to more effectively oxidize the surface of carbon fibers, and the oxidation reaction rate and intensity can be controlled by adjusting the ozone concentration and light irradiation amount. is possible,
Carbon fibers with desired surface treatments can be easily produced.

The irradiation light used in carrying out the present invention is preferably ultraviolet light, particularly 200 to 600 ru++, and examples of the light source include low pressure, medium pressure, or high pressure mercury lamps. The temperature of the tube wall of the light source is preferably adjusted to between room temperature and 10°C.

The carbon fibers treated in the present invention may be polyacrylonitrile-based, pitch-based, or cellulose-based carbon fibers,
Furthermore, heat-treated graphite fibers may be used.

〔Example〕

The present invention will be explained in detail by way of examples below. 1 Example 1 A carbon fiber with an elastic modulus of 24 ton/IEli2 was made to run through the surface treatment chamber at a constant speed so that the residence time in the chamber was 5 minutes, and an ozone concentration of 2 vo1% was applied from the exit side of the yarn. Air was supplied at a rate of 1 m/hr and exhausted from the yarn inlet side to keep the ozone concentration in the chamber constant. Surface treatment was performed by lighting a 500 W medium pressure mercury lamp provided in the chamber. Oxygen introduced into the surface layer by gscm of the obtained carbon fiber IIk/l1O48/
Cl8=0.16.

Example 2 Carbon fibers obtained by performing surface treatment in the same manner as in Example 1 by changing the residence time of the carbon fibers in the chamber and the ozone concentration in the chamber as shown in Table 1.
The amount of oxygen introduced into the surface layer at 0A was measured. The result is the first
Shown in the table.

In Table 1, Experiments A5 and 6i1: Comparative Examples show that the oxidation treatment according to the present invention has a great effect in these cases.

Table 1 [Effects of the Invention] In the present invention, due to the mutual effect of ozone and light irradiation, the effect of oxidation treatment on the surface of carbon fibers is greatly improved compared to a treatment using ozone alone.

Claims (1)

[Claims] A method for oxidizing carbon fibers, which comprises treating carbon fibers in an oxidizing atmosphere containing ozone while being irradiated with light.