JPS59137513A - Production of high-quality, high-performance carbon fiber - Google Patents

Abstract

PURPOSE:Acrylic fiber is preoxidized by heating it in an oxidative atmosphere in the presence of a specific amount of a reactive inorganic metal or metal-containing compound, then carbonization is effected in an inert atmosphere at high temperature to remove a trace amount of inorganic components in the atmosphere, thus producing the titled carbon fiber. CONSTITUTION:When acrylic fiber is converted into preoxidized fiber by heating it in an oxidative atmosphere and the resultant fiber is carbonized by heating it in an inert atmosphere at higher temperature, an oxidative gas and an inert gas containing a reactive inorganic metal or metal-containing compound that reacts with carbon to form metal-carbon solid solution, carbide and/or acetilide at at least 500 deg.C in an amount lower than about 0.5mg/Nm<3> are used as the oxidative and inert atmospheres to produce the objective high-quality, high-performance carbon fiber.

Description

[Detailed description of the invention] The present invention relates to a method for producing high quality, high performance carbon fiber.

Conventionally, carbon fibers obtained from precursors such as acrylic fibers have excellent mechanical properties such as specific strength and specific modulus, and are used for aviation, space applications, and fishing rods.

It is used in a wide variety of applications, including golf shafts and tennis rackets, and is produced in large quantities. One example of a manufacturing method is a method for manufacturing carbon fibers from acrylic fibers. The acrylic fibers are pre-lengthened and heated in an oxidizing atmosphere to transform the fibers into fibers with a defined structure. The process consists of a flame-retardant step or an oxidation step to convert the heat-stabilized fibers into carbon fibers, and a carbonization or graphitization step to convert the heat-stabilized fibers into carbon fibers by heating in a high-temperature inert gas atmosphere. The carbonization process is used in the industrial production of carbon fibers.The mechanical properties and raw acrylic fibers are exposed to a high-temperature oxidizing atmosphere, which chemically changes their molecular structure.
A variety of pyrolytic products are formed, and these pyrolytic products can contaminate the fiber surface, fuse the filaments together, and as flame resistance progresses, structural defects inside and outside the fibers can form, such as voids and cracks. The quality of the resulting carbon fiber manifests itself as defects such as.

It is said to reduce performance. Furthermore, in the carbonization step, the material is heated in an inert atmosphere at a higher temperature than the oxidation step, and thermal decomposition products are formed, causing the same problems as in the oxidation step. And the quality of carbon fiber in such flameproofing and carbonization processes.

In order to prevent the deterioration of performance, many proposals have been made for improving the acrylic fiber as a precursor, adding an oil agent to prevent fusion, and improving flame resistance and carbonization means. Among them.

JP-A-53-126325 discloses that precursor acrylic fibers contain, for example, impurities in the fibers due to the raw materials and manufacturing process.

It is stated that when metals, halogens, sulfur, etc. are contained, the oxidation resistance and electrical properties of the resulting carbon fibers are reduced.

The present inventors have conducted extensive studies on the influence of trace components contained in the heating atmosphere, particularly oxidizing gases and inert gases, on the physical properties of carbon fibers, rather than impurities contained in the fibers themselves. As a result, it was discovered that inorganic metals and their metal compounds, which are said to react with carbon to form solid solutions, carbides, and/or acetylides, etc. at the carbonization temperature of the oxidized fibers and their metal compounds have a large influence. That's all.

In other words, the oxidizing atmosphere generally used in the flameproofing process 1. For example, in the air there are organic substances, although there may be slight differences depending on the region or environment.

Contains minute components such as inorganic substances and dust. Furthermore, in the above-mentioned flameproofing step, the oxidizing atmosphere is treated with a catalyst and recycled for use in order to prevent contamination of the oxidizing atmosphere and from the viewpoint of environmental hygiene and energy saving. Inorganic metals and their compounds are mixed into the oxidizing atmosphere. Similarly, the inert atmosphere 9, for example, nitrogen, used in the carbonization process also contains minute components of inorganic substances and dust caused by piping and the like.

The present invention aims to clarify the effects of trace inorganic components in an oxidizing atmosphere and trace inorganic components in an inert atmosphere on the physical properties of carbon fibers, and to establish an industrial manufacturing method for high-quality, high-performance carbon fibers. The purpose is to

The object of the present invention is to achieve the invention described in the claims, that is, as an oxidizing atmosphere in the flameproofing process and an inert atmosphere in the carbonizing process, reacting with carbon at least in soo'c to form a solid solution, carbide, and This can be achieved by using an atmosphere in which the content of acetylide-forming inorganic metals and their compounds (hereinafter referred to as 1-reactive thermomechanical metals) is about 0.5 mg/N m3 or less. In the present invention, air is representative of the oxidizing atmosphere, and nitrogen is representative of the inert atmosphere, but the present invention is not limited to these.The feature of the present invention is that the oxidizing atmosphere has a low content of specific minute components. and the use of an inert atmosphere.
: At least 500' as defined in the present invention.
Inorganic metals and compounds thereof that react with carbon to form a solid solution in C include Fe and iron oxide.

Those that form carbide include Fe and Ni.

Typical examples include Co, Mn, Cr, Mo+Ca, and calcium carbonate, and furthermore, Zn forms an acetylide.

Examples include Cu, Mg, Cd, Au, Ag, and Hg.

, the content of the above-mentioned reactive inorganic metals in the oxidizing atmosphere and inert atmosphere used in the present invention is as small as possible9
It usually needs to be about 0.5 mg/Nm' or less, preferably about 0.1 mg/Nm'
Below, more preferably about 0.05 mg/N m'
It is best to do the following. If the content of the reactive inorganic metals exceeds about 0.5 mg/Nm', it is difficult to produce high quality, high performance carbon fibers, which is the object of the present invention, and especially the tensile strength and elongation are extremely low. This makes it difficult to improve. In particular, among direactive inorganic metals, one (Fe) that forms a solid solution has a large effect on the physical properties of carbon fibers, so it is preferable to limit the amount to 0.05 mg/N m' or less.

The content of such reactive inorganic metals is about 0.5 mg/
Methods for preparing the oxidizing atmosphere and inert atmosphere of Nm3 or less include, but are not particularly limited to, methods such as forced filtration of the atmospheric gas, and a method of blowing the atmospheric gas into the reacting liquid bath for cleaning.

Preferably, it is industrially advantageous to filter with a glass filter or a sintered metal filter.

One example is fiber diameter: 10 microns, thickness: 5
0mm, density: 8Kg/m3, and a dust collection efficiency of 0% or more (dust 7 microns, 2.5m/sec) glass filter ("MKR-10" manufactured by Nippon Glass Fiber ■).

In the present invention, the cleaning treatment of the oxidizing atmosphere and inert atmosphere needs to be performed on all the oxidizing gas supplied to the flameproofing process and the inert gas supplied to the carbonization process, for example.

Not only the air recycled to the flameproofing process, especially the catalytically treated one, but also the unused fresh air is treated. The conditions for producing the carbon fiber of the present invention using such an oxidizing atmosphere and an inert atmosphere are as follows: 2.
The breaker is heated at an elevated temperature of 30 to 320 C to convert it into flame resistant fibers.
The content of the reactive inorganic metals of 00C is about 0.5 mg
/Nm3 or less inert atmosphere (nitrogen, helium,
There is a method of carbonizing or graphitizing by heating at an elevated temperature in argon). When such conditions are adopted, the mechanical properties of the resulting carbon fibers are significantly improved. By flameproofing and carbonization using the oxidizing atmosphere and inert atmosphere of the present invention.

Physical properties 2 of the resulting carbon fibers are improved because the reactive inorganic metals that adhere and bond during the flame resistance process and carbonization process are converted into carbonaceous substances over time during the carbonization process (reacting with the fibers to form a solid solution and carbide). This is achieved by suppressing the formation of compounds foreign to carbon, such as carbon and acetylide.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the present invention, the method for detecting and quantifying reactive inorganic metals in an oxidizing atmosphere and an inert atmosphere uses a light scattering method digital dust meter RA-3 manufactured by Shibata Chemical Co., Ltd., and a known atomic absorption method. (For example, see pages 336 to 352 of "Atomic Absorption Spectrometry," co-authored by Kazuo Yasuda and Toshihiko Hase, published by Kodansha).

Example 1. Comparative example 1 Single yarn fineness 1d, number of single yarns 6000 2 strength 5.6g/
d. Acrylic fibers with an elongation of 11.5% are fired at 240 to 270 °C in a heating furnace with air as an oxidizing atmosphere,
We created flame-resistant fibers.

At this time, flame resistance was achieved using an oxidizing atmosphere containing various inorganic metal compounds shown in Table 1.

The total content of various inorganic metal compounds in the obtained flame-resistant fiber is 0.
．． Carbon fibers were produced by raising the temperature and carbonizing the carbon fibers in a carbonization step of 700 to 1500'C in an inert atmosphere of nitrogen of 01 mg/Nm' or less.

In test No. 1, the air used for the oxidizing atmosphere was filtered using a micro glass filter MKR-1 manufactured by Nippon Glass Fiber Co., Ltd.
Filter using A to reduce the amount of inorganic metal compounds in the air to 0.01
When it was set to mg/Nm3.

The physical properties of the obtained carbon fiber are strength: 340 kg/mm2
The elastic modulus was 23.8 t/mm2.

In Test Nos. 2 to 6, air was filtered using MKR-10 as in Test No. 1, and each inorganic metal compound was added to the air in the amount shown in Table 1.

Test No.'l and Test No. 31p
M n O.

, CaCOB, is a metal compound that forms carbide with carbon, and is present at 0.8 mg/N in the atmosphere.
m'.

1 and 0 mg/N m', the strength of the obtained carbon fibers is 265 kg/mm2, respectively.
, 203K g/mm'L, which is significantly lower than test No. 1.

In addition, Fe; z03 in Test No. 4 forms a solid solution and carbide with carbon, and has a concentration of 0.6 mg/N.
-The carbon fiber strength is 176Kg/m just by its presence.
ms decreases significantly.

ZnO in test No. 65 and test No. 016.

It is a metal compound that creates carbide with carbon and also reacts with acetylene to create acetylide.

As shown in test No. 005, ZnO was present in the atmosphere at 0.
6 mg/N - the strength of the obtained carbon fiber decreases to 280 Kg/mm''L, but test No. 6
At 0.4mg/Nm3, 1 strength is 325Kg/in2
No decrease in strength was observed.

- Comparative example 2 Single yarn fineness 1d, number of single yarns 6000 8 strength 5.6g
/d, acrylic fiber with elongation of 11.5% from 240
A flame-resistant fiber was produced by firing in a heating furnace using air at 270'C as an oxidizing atmosphere.

At this time, the air used for the oxidizing atmosphere was filtered using a microglass filter MKR-10 manufactured by Nippon Sheet Glass Fiber Co., Ltd. to reduce the amount of inorganic metal compounds in the air to 0.01 m
g/Nm3. The obtained oxidized fiber is F e
20 JO, 7 rn g/N rn' The carbon fibers were prepared by returning the carbon fibers at an elevated temperature in a carbonization process at 700 to 1500° C. in an atmosphere of nitrogen added. The obtained carbon fiber has a strength of 150 K g/mm'' and an elastic modulus of .

24.5 t/mm', and the 2 strength decreased significantly.

Example 2 Single yarn fineness 1d, number of single yarns 6000 9 strength 5.6g
/d, elongation 11.5% acrylic fiber yarn about 24
Oxidized in a hot air circulation heating furnace set at 0.00C, then placed in a nitrogen atmosphere carbonization furnace with a temperature increase gradient of 700 to 1500 @C and a total content of various inorganic metal compounds of 0.01mg/Nm3 or less. It was then carbonized to produce carbon fiber.

In this case, the air circulating in the hot air circulation type heating furnace was purified through the catalytic oxidation catalyst layer and then circulated as it was. The tensile strength of the obtained carbon fiber is 270 K g/m
It was m2.

Therefore, after the above-mentioned catalyst treatment, the air circulating in the hot air circulation type heating furnace was
After filtering using R-10.

The tensile strength of the obtained carbon fiber is 350 K g/m
It was m'.

Inorganic metals in the circulating air before being filtered with a microglass filter were analyzed using atomic absorption spectrometry.

When analyzed and quantified, Je, Cu, and Cr were detected.
Although the amount reached 1 mg/N-.

After filtering with the filter, O.01mg/Nm'
Met.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Claims] When heating acrylic fibers in an oxidizing atmosphere to convert them into flame-resistant fibers, and then heating the flame-resistant fibers at a higher temperature in an inert atmosphere to carbonize them, the oxidizing atmosphere and As an inert atmosphere, the content of primary reactive inorganic metals and their metal-containing compounds is approximately 0.5 m g
High quality, characterized by the use of oxidizing gases and inert gases of less than / N m3. A method for producing high-performance carbon fiber. Here, the above-mentioned reactive inorganic metals and their metal-containing compounds are those that react with carbon in an inert atmosphere at at least 500°C to form a solid solution of metallic carbon, carno(ide) and/or acarno(ide) and/or acarno(ide).