JPS6366325A - Production of carbon fiber for high-performance cfrp - Google Patents

Abstract

PURPOSE:To obtain the titled higher-performance fibers useful as a high- performance carbon fiber composite material which is a raw material for structural materials of aircraft, by heat-treating carbon fibers having strong resin dependence of strand tensile breaking strength in a special atmosphere. CONSTITUTION:Carbon fibers having >=80kg/mm<2> resin dependence of strand tensile breaking strength are heat-treated at 800-1,250 deg.C in an atmosphere containing a hydrogen halide, preferably hydrogen chloride and steam to afford the aimed fibers. The carbon fibers which are a raw material are preferably obtained by flameproofing fibers prepared from an acrylonitrile polymer containing >=90wt% acrylonitrile at 240-350 deg.C, carbonizing the flameproofed fibers and oxidizing the surface under severe condition. Steam generated from heated water is preferably used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to high performance carbon fiber composite materials (hereinafter referred to as rCFR).
Regarding the method for producing carbon fiber for PJ), more specifically, it is a method for producing carbon fiber with higher performance by processing carbon fiber whose strand tensile breaking strength is strongly dependent on resin under a special ambient atmosphere. Regarding.

In general, carbon fibers have excellent mechanical properties such as specific strength and specific modulus, and therefore carbon fibers are used as reinforcing materials.
FRP is being widely used for aircraft structural materials, space development equipment, automobile parts, and sporting goods. In recent years, particularly for aircraft and space development equipment, there has been a demand for higher performance CFRP that has increased strength and excellent heat resistance and weather resistance.

[Conventional technology]

In order to obtain high-performance CFRP as mentioned above, many high-performance polymers (IJ Fuchs resin) have been developed (
For example, JP-A-60-197722).

In addition, many methods for increasing the strength of carbon fibers themselves have been developed (for example, JP-A-60-88128).
. Research is increasingly being conducted to develop higher performance CF RP by combining these high-performance polymers with IJ Fuchs resin and high-strength anti-carbon fibers.

[Problem that the invention seeks to solve]

The combinations of high-performance matrix resins and high-strength carbon fibers that have been proposed so far have not been able to fully demonstrate the characteristics of both. That is, if the two are simply combined, the characteristics of the obtained CFRP are often lower than expected values. As a result, the dependence of the strand tensile strength at break on the resin (this property will be defined later) appears.

[Means for solving problems]

The present inventors used plastic as a matrix ('
As a result of intensive research into the mechanical fracture mechanism of FRP, we found that such tensile fracture of CFRP is caused by carbon n! found that there is a close relationship between the interface state between fibers and matrix plastic, and based on this knowledge, we developed high-performance CFRP.
As a result of efforts to develop carbon fiber for use in carbon fibers, the present invention was completed.

The method for producing high-performance carbon fiber for CFRP of the present invention has a resin dependence of strand tensile breaking strength of 80 kg/1as.
2 or more carbon fibers are heat-treated at a temperature of 800°C to 1250°C in an atmosphere containing hydrogen halide and water vapor.

Here, "resin dependence J of strand tensile breaking strength is
In the strand test method described in JIS-R7606, bisphenol A type epoxy resin 1 Epicor) 828 (manufactured by Yuka Shell Co., Ltd.) 100 times certified section,
150° C. using a resin formulation (referred to as “resin formulation (&)”) having a composition consisting of 90 parts by weight of methylnazic anhydride, 2.5 parts by weight of benzyldimethylamine, and 21 parts by weight of methishthyl ketone.

Tensile strength of the strand obtained by curing for 30 minutes (
A ky, /am2) and the same bisphenol A as above
Using a resin formulation (referred to as "resin formulation (b)") having a composition consisting of 100 parts by weight of type epoxy resin, 3 parts by weight of borofluoride monoethylamine, and 43 parts by weight of methyl ethyl ketone, the mixture was heated at 130'C for 1 hour. 2 at 180℃
Tensile strength of strands obtained by time-curing treatment (B
kFi/van”) and the absolute value of the difference (IA-B 1k
g/J).

The carbon fibers used in the method of the present invention are obtained by subjecting a raw material precursor to flame resistance treatment and subsequent carbonization treatment. As the precursor, those commonly used in the production of carbon fibers such as acrylonitrile synthetic fibers, pitch fibers, cellulose fibers such as rayon, and pheno-#It& fibers can be used. Among them, at least 90
Preference is given to fibers produced by known methods from acrylonitrile-based polymers containing 1% of acrylonitrile units. In particular, a fiber bundle with a single fiber fineness of 0.5 to 1.5 deniers and a number of single fibers of 1,000 to 12,000 is preferable, and a fiber bundle with few impurities and defects, a dense structure, and a highly oriented fiber bundle is more preferable.

The flame-retardant treatment is carried out by heating the above-mentioned Nolicasa in an oxidizing atmosphere, typically at 200 to 400°C, preferably at 240°C, using a hot air circulation furnace and/or a heating roller.
This can be done by heat treatment at ~350°C for a predetermined period of time.

The carbon fibers used in the present invention whose strand tensile strength at break depends on the resin are 80 kgZ- or more are obtained by surface oxidation after carbonizing the fibers by a conventional method or in the same process as the carbonization. It can be obtained by processing. That is, carbonized and unoxidized carbon fibers are subjected to gas phase oxidation treatment in an oxidizing gas according to a conventional method, or
Alternatively, the carbonization process is performed in an atmosphere containing an oxidizing gas to oxidize the fiber surface in a gas phase (for example, see Japanese Patent Application Laid-open No. 52-53092), or the carbonized unoxidized carbon fiber is subjected to an electrolysis reaction. A method of oxidizing the fiber surface by electrolytic oxidation using
222), or by a method in which carbonized unoxidized carbon fibers are treated with a solution containing an oxidizing agent to oxidize the fiber surface in a liquid phase (see, for example, VF Patent Publication No. 52-25199).

Further, it is also possible to use vapor-grown carbon fibers produced in the vapor phase using hydrocarbon gas as a raw material.

In particular, the above-described highly resin-dependent carbon fibers used in the present invention can be obtained by surface oxidation treatment under relatively severe conditions. Appropriate conditions for surface oxidation treatment can be easily found through repeated experiments.

Heat treatment temperature Visoo"c~1 in the method of the present invention
The temperature is 250°C, preferably 1000°C to 1200°C. In other words, the resin-dependent reduction in strand breaking strength, which is the objective of the present invention, occurs at a heat treatment temperature of 800°C to 1250°C, and particularly at a heat treatment temperature of 1000°C to 1200°C, the interlaminar shear strength of the resulting CFRP decreases. (hereinafter rI
It is preferable because there is little decrease in LssJ (abbreviated as LssJ) and the strand breaking strength is improved.

However, the treatment time at the above heating temperature is preferably 10 seconds or more, particularly preferably 20 to 100 seconds. That is, when the heating time is 10 seconds or more, the effect of reducing strand strength and resin dependence is sufficiently recognized, and when the heating time is 100 seconds or less, the treatment can be carried out without greatly reducing the In and SS values, which is preferable.

The hydrogen halide gas used as the atmospheric gas includes hydrogen halide gases such as hydrogen fluoride gas, hydrogen chloride gas, and hydrogen bromide gas, or the hydrogen halide gases described above are generated by thermal decomposition at the heat treatment temperature of carbon fibers. Practically speaking, it is preferable to use hydrogen chloride gas rather than using hydrogen halide generated by adding a halogen compound to the heat treatment system.

In addition, water vapor may be generated from heated water, or may be dispersed in gas as minute moisture particles by ultrasonic waves, but water vapor may be generated from water by heating. It is preferable to use water in the form of water. Furthermore, in addition to hydrogen halide gas and water vapor, other gases can be used as diluents in the atmospheric gas.

As the diluent, an inert gas such as carbon dioxide gas, nitrogen gas, argon gas, etc. is preferable.

As for the amount of water vapor, the water vapor concentration in the atmosphere is 0.
．． It is preferable that it is 1 volume ratio or more, and especially it is more preferable that it is 1-10 volume ratio or more. Water vapor concentration is 0.1
When the capacity is 10 cm or more, the effects of reducing the dependence of the strand breaking strength on the resin and improving the strand breaking strength, which are the objectives of the present invention, are well exhibited. And there is little water condensation inside the piping leading to it, making it possible to perform the next operation stably. Further, as for the ratio of water vapor to hydrogen halide gas, it is preferable that the volume ratio of hydrogen halide gas to water vapor is 0.1 or more, and furthermore, when the volume ratio is 1.0 to 4.0, it is more preferable. I like it. When the capacity ratio is 0.1 or more, the effect of reducing the dependence of the strand breaking strength on the resin, which is the object of the present invention, is particularly sufficiently achieved.

〔Effect of the invention〕

The carbon fiber obtained by the method of the present invention has a sharp decrease in resin dependence of strand breaking strength,
'cm' or less, and the absolute value of the strand strength is improved compared to the raw material carbon fiber before applying the method of the present invention.Furthermore, the ILSS of CFRP thermoformed using the carbon fiber obtained by the present invention Fall indicates a value that is sufficient for practical use.

For example, 100 parts by weight of N, N, N', N'-tetraglycidyldiaminodiphenylmethane (Aralgate MY720, manufactured by Chipa Iggy), 1 part by weight of 4.4'-diaminodiphenylsulfone 201iJ, 1.5 parts by weight of 37 boron fluoride monoethylamine. A prepreg is prepared from the carbon fiber obtained by the method of the present invention using a resin consisting of
The value remains at a high level of approximately 12.0 kg/c1rL2 or higher.

〔Example〕

Hereinafter, one method of the present invention will be specifically explained with reference to Examples.

Example 1 Acrylonitrile synthesis! 1! , fiber (single yarn denier 1.
3d, 6000 filaments) was heated in air at 240°C for 40 minutes and then at 260°C for 20 minutes to obtain a flame-resistant fiber, which was further carbonized at a maximum treatment temperature of 1350°C in a non-oxidizing atmosphere. After that, this carbon fiber was used as an anode, 1N nitric acid aqueous solution was used as an electrolyte, and 500 mA was applied.
The surface treatment was performed electrochemically using a direct current '1E current.
(hereinafter abbreviated as "resin dependence") was 85 kg/vm'', and the ILSS value was 12.5 kli7m''.

Based on the method of the present invention, this raw material carbon fiber is
．． At 900°C in an atmosphere consisting of 3 volumes of hydrogen, 2.0 volumes of hydrogen chloride gas, and 93.7 volumes of nitrogen gas,
When heat treated for 0 seconds, the resin dependence was 32 Yu/min.
, 1112, I A high performance carbon fiber for CFRP with an LSS value of 12.1 kg7m'' was obtained. The results are shown in Table 1.

Example 2 The same flame-resistant fiber used in Example 1 was carbonized in a non-oxidizing atmosphere at a maximum treatment temperature of 1300°C, and then the obtained carbonized fiber was treated with oxygen gas containing 0.5 volume ffi%. When gas phase oxidation was performed at 1300°C in an atmosphere, the strand tensile strength at break of the obtained carbon fiber was 110% depending on the resin.
Yu/12, the ILSS value is 12.4 kg/w'', so this raw carbon fiber is heated to 4 kg/w with water vapor based on the method of the present invention.
．． At 1100°C in an atmosphere consisting of 0 volume titanium, 1.0 volume titanium hydrogen chloride gas, and 95 volume titanium nitrogen gas,
When heat treated for 0 seconds, resin dependence was 30 k
g7m", and the ILSS value was 12.0 wrinkle-3.

Comparative Example 1 In Example 2, water vapor 4.0 volume and nitrogen gas 9
When the same treatment was performed except that an atmosphere consisting of 6 volumes of carbon fibers was used, the tensile strength of the strands of the obtained carbon fibers was drastically reduced, and CFRP for ILSS could not be formed.

Comparative Example 2 In Example 2, all the same treatments were performed except that the heating temperature was 500°C when heating in an atmosphere consisting of hydrogen chloride gas, water vapor gas, and nitrogen gas. The value was 12.4.9□2, but the resin dependence was 105'Q/1m'', which was hardly improved compared to the raw carbon fiber.

Example 3 The same flame-retardant FI1 used in Example 1. When carbonizing the fibers at a maximum treatment temperature of 1400°C, oxidizing gas is used to perform surface oxidation treatment at the same time as firing to obtain carbon fibers. The results are shown in Table 1. Using this carbon fiber as a raw material, heat treatment was performed at 1000°C for 90 seconds in an atmosphere consisting of 4.3 volumes of water vapor, 0.9 volumes of hydrogen chloride gas, and 94.8 volumes of nitrogen gas, based on the method of the present invention. When applied, the resin dependence was 41 kl/mx2, ILSS
was 12.2 kg/m2.

Comparative Example 3 In Example 3, the same treatment was performed using an atmosphere consisting of 0.9 volumes of hydrogen chloride gas and 99.1 volumes of nitrogen gas, except for the following, and the resin dependence was 92 kg/ My asthma was 2, and my ILSS value was 12.4 YA♂.

Example 4 The same flame-retardant RA fiber used in Example 1 was carbonized at a maximum treatment temperature of 1350°C in a non-oxidizing atmosphere, and then this carbon lR1 fiber was treated with potassium permanganate (KMn Oa).
) 0.2 double ff%, sulfuric acid (H2S04) double ffi
% in an aqueous solution at 80° C. for 10 minutes to obtain raw carbon fibers.

Based on the method of the present invention, this raw material carbon fiber is
．． 0 volume liquid, hydrogen chloride 1.2 volume and nitrogen gas 94
．． When heat treated for 40 seconds at 1000°C in an atmosphere consisting of 8-capacity silicon, the resin dependence was 45 kg/2, IL
SS value is 12.2kl? /- high performance carbon fiber for CFRP was obtained.

Example 5 The same treatment as in Example 4 was performed except that hydrogen bromide gas was used instead of hydrogen chloride, and the resin dependence was 6.
A high-performance carbon fiber for CFRP with an ILSS value of 0 kg/■2 and 12.3 kg/wj was obtained.

Table 1 summarizes the treatment conditions and characteristic values of untreated and treated carbon fibers in each of the above Examples and Comparative Examples.

Margin below

Claims (2)

[Claims] (1) Resin dependence of strand tensile breaking strength is 80 kg
A method for producing carbon fibers for high-performance carbon fiber composite materials, which comprises heat-treating carbon fibers having a carbon fiber diameter of /mm^2 or more at a temperature of 800°C to 1250°C in an atmosphere containing hydrogen halide and water vapor. . (2) The high-performance carbon fiber composite according to claim 1, wherein the water vapor concentration in the atmosphere is 0.1% by volume or more, and the volume ratio of hydrogen halide gas to water vapor is 0.1 or more. Method for producing carbon fiber for materials.