JPS60246821A - Preparation of carbon yarn - Google Patents

Abstract

PURPOSE:To obtain carbon yarn having high performance and a small amount of fluff, by arranging plural rollers in a flame-resistant treatment process, setting degrees of elongation and shrinkage between rollers at specific values determined by a specific method, subjecting acrylonitrile polymer yarn to flame-resistant treatment, followed by carbonizing it. CONSTITUTION:In subjecting acrylonitrile polymer yarn to flame-resistant treatment by drawing it in an oxidizing atmosphere at 200-400 deg.C by multiple stages, each ratio of elongation of multiple stages is set at the elongation and shrinkage point En+ or -3% range showing the inflection Pn determined from load and degree of elongation and shrinkage, preobtained from an experiment of a batch furnace on yarn, the yarn is subjected to flame-resistant treatment, and carbonized. A retention time of yarn between rollers is preferably 2-15min.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing high-performance carbon fibers in which acrylonitrile polymer fibers are flame-resistant treated under specific conditions and carbonized after fC.

[Prior art]

Generally, to produce carbon fiber from acrylic fiber, 2
A method is used in which a heat treatment is performed in an oxidizing atmosphere at a temperature of 00 to 400°C to form a flame-resistant structure, and then carbonization is performed in an inert atmosphere at a temperature of 400°C or higher. that time,
The application of tension or elongation during the flame-retardant process is effective in producing carbon fibers with excellent strength and elastic modulus. For example, Japanese Patent Application Laid-Open No. 49-54632 discloses a method of producing high-performance carbon fiber by distributing the elongation during flameproofing treatment between an early region and a late region.

However, in acrylic fibers, due to differences in the initial degree of molecular orientation or molecular cohesive force, carbon fibers with excellent performance may not be obtained even if they are elongated or contracted during the flame-retardant treatment process. be. Therefore, in the above method, excessive elongation may promote fuzzing and structural defects. As described above, the optimum elongation rate or shrinkage rate for flame resistance differs depending on the elongation cursor and is also influenced by the ambient temperature, so it is currently extremely difficult to optimize the amount.

[Purpose of the invention]

Therefore, the present inventors set the expansion/contraction rate between all the plurality of driving rollers in the flameproofing process to a random value in advance for the fibers at the supply roller point between them through batch experiments. The inventors have discovered that carbon fibers with extremely superior performance can be obtained by the above method, and have completed the present invention.

[Structure of the invention]

The gist of the present invention is that PAN-based polymer fibers are
In a flameproofing furnace having a plurality of driving rollers, 20
When flame-proofing is achieved by multi-step elongation in an oxidizing atmosphere at 0 to 400°C, the ratio of multi-step elongation is determined in advance by actual measurement, and the inflection point Pn is determined by the load and the expansion/contraction rate. This is a method for producing high-performance carbon fiber, which is characterized by setting the fibers within ±3% of each other, subjecting them to flame-retardant treatment, and then carbonizing them. The stay time is 20 minutes or less.

An example of a flameproofing furnace having a plurality of drive rollers according to the present invention f! : Shown in Fig. FIG. 2 shows an example of the expansion/contraction behavior of the starting yarn, acrylic fiber, in 240C1 nitrogen atmosphere with respect to time under various constant loads.

The manufacturing method in the present invention will be described below.

In Figure 1, the time the fiber stays in the furnace from roller Ro to R11 is 10 minutes, and the ambient temperature is 240°C.
Suppose that Next, by plotting the expansion/contraction rate and its load at the same time of 10 minutes from FIG. 2, a @Muku relationship with an inflection point approximately equal to Pn is obtained as shown in FIG.

However, in general, even though the ambient temperature is the same between a flameproofing furnace and a batch furnace in the firing process, due to differences in equipment characteristics,
Normally, the temperature and time dependence of changes in physical properties of fibers is different.

Therefore, rather than making the stay time in the furnace the same as described above, it may be better to make the physical property parameters, especially the density of the fibers, which is one measure of the progress of flame resistance, the same. Then, find the elongation rate F+' corresponding to the inflection point P. According to the degree of orientation determined by wide-angle X-ray diffraction, the elongation rate E
.

The degree of orientation increases with increasing elongation up to Fi,
Above this, the increase has reached a plateau, and the appearance of fuzz is also observed. That is, this elongation rate El becomes the optimum elongation rate between the rollers Ro and R1.

Next is the setting of the elongation rate between rollers R and R2. In this case, the fibers and tabs v2
40 tl: Elongated during processing for 10 minutes.

The relationship between load and elongation rate as shown in Figure 4 was plotted in the same batch experiment as described above for the fibers to which elongation rate F! Enter z'.

Hereinafter, the elongation rate between each roller is determined in the same manner. The elongation rate Kn (n = 1.2...
), the optimum point appears on the contraction side depending on the acrylic fiber. At this time, it is desirable that the time for the fibers to stay between each roller is within ti2o minutes, preferably 2 to 15 minutes. If it is longer than 20 minutes, the length of the stretching region will increase and the stretching rate between the rollers will also increase according to 7n, causing uneven stretching and increasing the tension difference between the next roller. , slipping occurs on the rollers at the border, increasing the frequency of fluff. When the time is less than 2 minutes, the number of times of contact with the roller increases, which also causes the generation of fuzz, and the number of CO-rollers becomes extremely large, so there is no advantage in terms of the equipment.

〔Example〕

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

Strand strength and strand elastic modulus are JI8R7601
Measured according to the method.

Example 1 Acrylonitrile 98 wt4. Acrylic yarn fibers (total denier 4560,3000 filaments, single fiber strength 5.0 t/d, elongation 150%) having a composition of 1 wt% methyl acrylate and 1 wt% methacrylic acid were
3-step temperature profile from 0-240-260℃? When performing heat treatment in a hot air circulation type flame retardant furnace with 20 minutes, the elongation rate E, by the method according to the invention in a batch furnace.

As a result, the elongation rate of the first zone was 15.0±1.0% or less, and the second zone was found to be E2.

The elongation rate of the third zone is 5.2, α6%, α0±1.
It was 2%. After flame-retardant treatment under the above conditions, the flame-retardant II
5 when passed through the first carbonization furnace at 0°C for 3 minutes.
% elongation and further 400 m in the same atmosphere at 1200°C in the second carbonization furnace. Heat treatment was performed under a tension of /denier. Table 1 shows the strand strength and strand elastic modulus of the obtained carbon fibers.

Example 2 In the same flameproofing furnace as in Example 1, the free roller located in the center was changed to a driving roller between each driving roller, and the time the fibers stayed between each driving roller was reduced to 1.
It was set to 0 minutes. Using the same method, the elongation rate F! ,,K2...
・E6 Request result: 12.0±1.2 in order from K.
%, 5.4 α6%, 54 ± 0.9%, 2.0 ± 1.0
%, 0.8±1.0 ratio, -α80.8%. A carbon edge # was obtained under the same conditions as in Example 1 except for this flame-resistant elongation condition. Its performance is shown in Table 1.

Comparative Example 1 In Example 1, the elongation rate "! + "2 and Hz t
1 (LO%, 2.0% and 0%, and all other conditions were the same as in Example 1 to obtain carbon fibers. The performance is shown in Table 1.

Comparative Example 2 In Example 1, all drive rollers during the flameproofing process were changed to free rollers, and 20% elongation was applied only to the godet rollers at the entrance and exit of the flameproofing furnace. Its performance is shown in Table 1.

Table 1 [Effects of the Invention] By employing all the methods of the present invention, a product with significantly improved strength and elastic modulus can be obtained.

[Brief explanation of the drawing]

(2) Figure 1 is an example of a flameproofing furnace used to carry out the present invention. FIG. 2 shows the total expansion and contraction of acrylic fibers under various loads at 240° C. in 9 atmospheres, with the horizontal axis representing time and the vertical axis representing contraction rate. I used denier and breaker denier. FIG. 5 is a plot of the expansion/contraction y$ for each total load at the time of 10 minutes in FIG. Figure 4 Co., Ltd., the same prong I as in Figure 3 for the fibers on the supply roller R1.

Claims (1)

[Claims] When LEAN polymer fiber is made flame resistant by being stretched in multiple stages in an oxidizing atmosphere at 200 to 400°C in a flame resistant furnace having a plurality of driving rollers, each ratio of the multiple stages of stretching is The carbon is characterized in that the elongation in which indicates the inflection point Pn or the elongation rate determined by actual measurements in advance or within ±3% of the value thereof is subjected to flameproofing treatment 1, and then carbonized. Fiber manufacturing method. λ I! between each drive roller of multistage extension! The method for producing carbon fibers according to claim 1, wherein the fiber stays for less than 20 minutes.