JPS61113878A - 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 [Field of Industrial Application] The present invention relates to a method for oxidizing the surface of carbon fibers.

[Conventional technology]

Carbon fibers are generally subjected to surface oxidation treatment to improve wettability with matrix resin and increase adhesive strength, and in industrial cases, electrolytic oxidation is used. However, because it is a wet method, there are many problems such as the complexity of the process, problems with waste electrolyte treatment, and troubles caused by residual electrolyte in the treatment system. This method is superior from an industrial perspective.

The basic technique for vapor phase indoctrination is heat treatment in air, and many improved methods have been proposed, one of which is known as a vapor phase oxidation reaction using ozone.

When performing °C gas phase oxidation using ozone, ozonized air is usually introduced into a chamber equipped with a heater to treat the °C carbon fibers.

Ozone is very easy to decompose, and the decomposition is particularly severe at high temperatures, so it is common to carry out the oxidation reaction at low temperatures, but in this case the oxidation reaction is extremely slow. Ozone diffuses into the tow (steps are rate-determining), so it has the disadvantage that non-uniform reactions tend to occur within the tow.

For this reason, the oxidation reaction using ozone is not currently used industrially, but since gas phase oxidation using ozone is simple and has a large oxidizing effect, its significance would be immense if it were used industrially. (ゝ0 [Problems to be Solved by the Invention] The present invention aims to find a treatment method that allows the oxidation reaction of carbon fibers to occur while minimizing the decomposition of ozone as much as possible. It is in.

[Failure to solve the problem]

That is, in the present invention, when treating the surface of carbon fibers running in an oxidizing atmosphere containing ozone, the oxidizing gas flow direction in the surface treatment chamber is set to be parallel to the running of the fibers. After treatment at 160-250 °C, heat to 160 °C or higher at a rate of 10-250 °C.
It is to be processed at ℃.

The advantage of the present invention is that the direction of the oxidizing gas flow is parallel to the running direction of the fibers, and by creating a temperature gradient during the treatment, the oxidation reaction can proceed efficiently.

The first feature of the present invention is that the treatment is performed at a temperature range of 20 to 40°C where ozone concentration does not substantially decrease, thereby replacing the air contained in the tow and allowing ozone to sufficiently diffuse into the tow. There is a particular thing.

The second feature is that the ozone is forcibly thermally decomposed in a short period of time by heating it to 160℃ or higher within an extremely short period of time.
The excited molecules generated at this time cause the carbon fiber ′lj! :t
In the present invention, in order to preliminarily replace the air in the tow with ozonized air, the treatment is preferably carried out at a temperature range of 20 to 40° C. in which ozone is not substantially decomposed. The residence time at this temperature is appropriately selected depending on the number of filaments and tows of the carbon fiber tow and the processing speed, but is usually within several minutes.
It is desirable that the temperature increase rate to 1V1120°C be as fast as possible, but the final processing rate and time, which are in the range of 10 to b seconds, should be selected depending on the processing speed and target processing level.
Preferably, the temperature is 60 to 250°C for 10 seconds to 3 minutes.

In the present invention, the ozone treatment temperature is set at a low temperature (not less than 160° C.), and substantially a part of the ozone is decomposed to generate active excited molecules, so that the temperature is in the low temperature range.

The carbon fibers referred to in the present invention may be PAN-based, pitch-based, or cellulose-based carbon fibers, and may also be heat-treated graphite fibers at ℃.

The ozone concentration is within a range where the oxidation reaction can proceed industrially efficiently (there is no particular limit).

〔Example〕

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 When the effective treatment length is 3 m, the internal temperature of the chamber is set to have the temperature distribution shown in Figure 1, and the elastic modulus is 24 tom/
- the carbon fibers are run through at a processing speed of 3 k/min, and 1
Air with an ozone concentration of 2 vol% at a rate of m”/hr?
The carbon fibers were supplied from the inlet side of the chamber in a parallel flow with respect to the running direction of the carbon fibers, and the carbon fibers were exhausted from the outlet side to perform surface treatment. When the amount of oxygen introduced into the surface of the obtained carbon fiber was determined using ESCAg, the composition ratio of 015101g was α
20, and it became clear that the surface treatment was carried out effectively.

Example 2 ESC'A'i measurement of carbon fiber obtained by surface treatment in the same manner as in Example 1 except that the processing speed was 1 m/min, the composition ratio of Is/Cps was 0.25. became.

Example 3 Carbon fiber with an elastic modulus of 30 ton/m" was subjected to surface treatment in the same manner as in Example 1, except that the temperature distribution was set as shown in Figure 2. The OIs/C1s composition ratio by ESCA was Q, It was 25.

Comparative Example 1 Example 1 except that the running direction of the fibers was reversed in Fig. 1
When surface treatment was carried out in the same manner as above, the ratio of O1s/C,s by gs CA was (L13).

〔Effect of the invention〕

The carbon fibers oxidized on one surface according to the present invention have excellent adhesion to a matrix, and a composite material with high peel strength can be obtained.

[Brief explanation of drawings]

Figures 1 and 2 illustrate the present invention and show the temperature distribution in the running direction of the fibers.
Exit chamber length upper (rrLI
ヮ-'rf Figure entry Exit Teyannogu-&ya (m)
. +2 times

Claims (1)

[Claims] When treating the surface of carbon fibers running in an oxidizing atmosphere containing ozone, the flow direction of the oxidizing gas in the surface treatment chamber is set to be parallel to the running of the fibers.
After treatment at 40°C, the heating rate was 10-50°C/sec.
A method for oxidizing carbon fibers, which comprises heating to 60°C or higher and subsequently treating at 160 to 250°C.