JPS59112029A - Manufacture of carbon fiber - Google Patents

Abstract

PURPOSE:To manufacture high quality carbon fiber having extremely small amounts of fluffs, end breakages, welds, etc., by preparing an oxide filament from a precursor filament, and carbonizing the oxide filament with a vertical carbonization furnace having a gas vent hole at a specific position. CONSTITUTION:A precursor filament such as acrylic precursor filament is heated in an oxidizing atmosphere, and the obtained oxidized filament is carbonized with a vertical carbonization furnace having a maximum temperature of >=700 deg.C and having a gas vent hole at the central part having a temperature range of 400-600 deg.C. A high quality carbon fiber having remarkably reduced amounts of defects such as fluff, end breakage, welding, etc. can be manufactured by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carbon fibers, and more specifically, the present invention relates to a method for producing carbon fibers, and more specifically, it reduces the deterioration of the physical properties of carbon fibers caused by exhaust gas, particularly tar-like substances, in the production of carbon fibers, and reduces fuzz, thread breakage, and This invention relates to a method for producing high-quality carbon fiber with significantly fewer defects such as fusion.

Carbon fiber has excellent mechanical properties such as specific strength,
Due to its specific modulus of elasticity and its excellent chemical and electrical properties, it is used in a wide range of fields, from aviation and space applications to golf shirts, fishing rods, tennis rackets, etc., as well as ships, automobiles, etc. It is being used in various fields.

Conventionally, carbon fibers are produced by thermally stabilizing precursor fibers (hereinafter referred to as precursors), typically acrylic fibers or pitch fibers, by heating them in an oxidizing residue such as air.
It is then produced by heating at a higher temperature in an inert atmosphere such as nitrogen, helium, argon, etc. to convert it into carbonaceous or graphite fibers. In such a carbon fiber manufacturing method, the precursor, especially fiber made of a high molecular weight polymer such as acrylic fiber, is heated in an oxidizing atmosphere to evaporate or heat the oil agent applied during the manufacturing of the precursor. As it is decomposed and removed, it undergoes complex chemical reactions such as oxidation and crosslinking, and is converted into thermally stable oxidized fibers.

In this oxidation process, the weight loss of the precursor is smaller than the weight loss in the subsequent carbonization process, and this oxidation process usually requires a large amount of oxidizing atmospheric gas or waste gas treatment. It is said that there is little contamination of the pre-load by thermal decomposition products such as oils and the like. The process of heating and converting into carbon fiber, especially low-temperature carbonization with a maximum temperature of 700 to 1000'C.
In the heated atmosphere called the pre-IJ carbonization region, the oxidized fibers show a significant weight loss, about 50% of the weight loss of the pre-carburization.
-C is said to occur in this region. Moreover, the hi of the inviscid gas supplied to this carbonization process is usually much lower than that of the oxidation process, and the inert gas in the low (1) carbonization region contains a large amount of thermal decomposition products, especially It is extremely necessary to prevent carbonization draughts caused by tar-like substances in carbon fiber production.For example, in the vertical carbonization furnace, an inert gas is introduced downward from the top of the furnace, and the waste gas is passed through the furnace. When extracting from the hot section, use the chimney of a vertical furnace.
It is difficult to prevent accumulation and scaling, which obstructs the smooth flow of inert gas in the furnace and causes fluctuations in the furnace pressure. If you introduce an inert gas from the bottom of the furnace to the top and extract the waste from the upper part of the furnace, the temperature of the waste gas at the outlet should be removed.
Since the temperature is close to the maximum temperature, the extraction port is easily damaged by heat, resulting in energy loss. Furthermore, when the thread runs from the bottom to the top, the thread runs in the same direction as the gas containing decomposition residue, so the running thread or the inert gas may be contaminated by tar-like substances. As a result, it is difficult to stably produce high-quality, high-performance carbon fiber.

The Ministry of the Invention and others have developed a carbon fiber using the above-mentioned vertical carbonization furnace.

That is, in the present invention, when carbonizing the oxidized fibers obtained from the precursor, a vertical carbonization furnace with a maximum temperature of at least 700C is used, and the crystallinity range of carbonization power 1 is 4.
The above problem is solved by providing an iJ+ waste extraction port in the central part of the furnace where the temperature is 00 to 600'C.

The vertical carbonization furnace used in the present invention is a well-known furnace, and although not particularly limited, oxidized fibers are preferably introduced from the lower part of the furnace and taken out from the upper part of the furnace, and the upper and lower seal parts of the furnace are equipped with an inert gas sealing mechanism. It is preferable to use a furnace of the type in which the scraps can be introduced both from above and from below.

In the present invention, the non-talking gas in the vertical carbonization furnace is maintained at a high temperature from the bottom of the furnace to the top, and
Its maximum temperature is at least 700℃, preferably 70℃
It is necessary that the temperature is 0 to 1000°C, and that there is a temporal temperature distribution in the direction of 6 degrees. In other words, according to the inventors' test i.1, carbon fibers or ICs obtained by pre-stamping oxidized fibers, heating and carbonizing them at such a temperature range, and further treating them at high temperatures have significantly superior physical properties and quality to graphite fibers. Not only improved, but also within the temperature range of 400~6oo
Thermal decomposition of oxidized fibers proceeds rapidly and mostly in the temperature range of ℃.
The progress of thermal decomposition of the oxidized fiber is 400 to 600.
By setting the temperature range of 'C in the center of the furnace and installing an exhaust gas outlet in the center, exhaust gas containing a large content of pyrolysis products can be extracted from the furnace. By extracting inert gas in the temperature range of 400 to 60°C as exhaust gas, it is possible to fully reflect the improvement in the physical properties of carbon fibers. This is because contamination by tar-like substances, which are thermal decomposition products of NJ and navy blue, can be significantly reduced.

The exhaust gas m extracted from the central outlet is 20 to 50% by volume of the inert gas supplied to the oil furnace.
is appropriate, but preferably 30 to 40%.

One specific embodiment of the present invention will be explained below with reference to the drawings.

Figure 1 is a schematic side view C of the vertical carbonization furnace used in the present invention.
1 is a vertical carbonization furnace, 2 is installed both on the lower side and below the furnace (inert gas supply), 3 is an oxidized fiber braided yarn, and 4 is a gas vent The outlet, 5I, is a device for decomposing or burning exhaust gas, and 6 is a suction 10W.

The fermented fiber yarn 3 is introduced from the lower part of the furnace 1 at a temperature of a3°C in the figure, subjected to firing treatment, and then taken out from the upper part of the furnace.

As for the temperature distribution inside the carbonization furnace, for example, block C shown by sharp lines is 300 to 400°C, block I] 4
00~600℃, A block 600~1000''C. In this case, the maximum temperature inside the furnace is at least 700
It is not possible to produce carbon fiber in an industrial manner unless the atmosphere is ``C''.The exhaust gas extracted from the outlet 4 in the center of the furnace is treated in a decomposition or combustion device 5, and then passed through a suction blower 6. released into the atmosphere through

The oxidized fibers carbonized in the carbonization furnace used in the present invention are not particularly limited, but for example, if the precursor is acrylic [[, the specific gravity is 1.34 to 1, '45
, a moisture content of 5 to 9%, and a strength and elongation of 2 to 5 g/d and 5 to 12%, respectively.

Further, the carbon fibers carbonized in the carbonization furnace can be heated in an inert atmosphere at a relatively high temperature, for example, 1000 to 2000'C, to more completely carbonize or graphitize the fibers.

According to the present invention, troubles when trying to improve the physical properties of carbon fiber obtained by employing low-temperature preliminary carbonization with a maximum temperature of at least 700 ° C., especially troubles caused by tar-like substances that are thermal decomposition products thereof, are solved, The quality stabilization, operability, and physical properties of the resulting carbon fibers can be greatly improved.

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

Example 1 Acrylic precursor yarn (1 d/filament, 10,000 filaments) was heat-treated in an oxidizing atmosphere at a maximum temperature of 260° C. to obtain oxidized fibers.

This oxidized fiber has a specific gravity of 1.38, a moisture content of 8.0%, and a strength of 3.
．． b/d, elongation 10.0%.

Next, the oxidized fiber braid was introduced into a vertical (low temperature) carbonization furnace shown in FIG. 1 at a speed of 5 m/min and subjected to firing treatment. Naa
3. At this time, the supply amount of inactive Shinai su (nitrogen scum) is 12 ONT
11″/hr, exhaust gas extraction fJ) 4 is 40 N T
11'/br, extraction I+A Iu was 450'C.

The yarn taken out from a part of the furnace was then treated in a nitrogen gas atmosphere at 1400°C.

Table 1 shows the results of investigating the workability, quality and quality of the carbon fiber thus obtained.

Table 1 Comparative Example 1 Carbon fibers were obtained in the same manner as in Example 1 except that the exhaust gas extraction was changed to A block (temperature 800°C) or C block (temperature 350°C).

Table 2 shows the results of investigating the operability, quality, and grade of the obtained carbon fibers.

Table 2

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a vertical carbonization furnace showing one embodiment of the present invention. 1 Vertical carbonization furnace 2, small waste supply port 3: Oxidized fiber braided yarn 4: Paper waste removal port 5: Exhaust gas decomposition or combustion device 6: Exhaust gas suction 10W Patent applicant Toshi Co., Ltd.

Claims (1)

[Claims] When carbonizing the oxidized fiber yarn obtained from the precursor edge @1 yarn in a vertical carbonization furnace having a maximum temperature of at least 700°C, the temperature range of 400 to 600'C in the center of the carbonization furnace is A method for producing carbon fiber assembly, characterized by using a carbonization furnace with one exhaust gas outlet.