JPH09268437A - Continuous production of carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing carbon fibers, capable of preventing the carbon fibers from wrapping around a roller or breaking and capable of continuously obtaining the carbon fibers little in fuzzes and excellent in handling in downstream processings in improved production efficiency by subjecting a precursor fiber bundle to a flame-resistant treatment, imparting water to the flame-resistant fiber bundle and subsequently carbonizing the treated fiber bundle. SOLUTION: This method for continuously producing carbon fibers comprises heating the precursor fiber bundle of polyacrylonitrile, etc., in an oxygen- containing atmosphere, such as air, heated at 200-300 deg.C, imparting water (preferably in an amount of 0.1-2.0 times the weight of the obtained flame-resistant fiber bundle) to the flame-resistant fiber bundle and subsequently carbonizing the fiber bundle into the carbon fibers. The density of the fibers is preferably controlled to >=500 filaments/mm, and a plurality of the precursor fiber bundles are preferably allowed to run side by side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method suitable for producing high-quality carbon fiber by preventing winding and breakage of a yarn in a carbon fiber manufacturing process, preventing occurrence of defects such as fluffing. .

[0002]

2. Description of the Related Art Conventionally, carbon fibers are prepared by heating various carbon fiber precursor fiber bundles in a flameproof fiber bundle by heating them in an oxidizing atmosphere at about 200 to 300 ° C. A method of carbonizing by heating in a high temperature inert gas atmosphere is adopted as a general industrial manufacturing method. However, in such a production method, in the step of heating various precursor fiber bundles in an oxidizing atmosphere of about 200 to 300 ° C. to convert them into flame-resistant fiber bundles, the fiber bundles come into contact with a plurality of rollers. Therefore, there is a problem that the fiber bundle is loosened due to rubbing with the roller, fluffing occurs, and yarn winding is likely to occur during the next step. Such a problem not only lowers the production efficiency of the carbon fiber but also deteriorates the quality of the carbon fiber and causes a problem of handling property such as fuzz and yarn breakage during high-order processing molding.

Conventionally, in order to solve such a problem, for example, in Japanese Patent Publication No. 62-3246, a yarn is entangled by a fluid jet method, and then 10 times / m.
Although the following method of imparting the twist and imparting the yarn converging property has been disclosed, in recent years, the expansibility in the high-order processing step of the carbon fiber bundle has been required, and such a process stabilizing technique is advantageous. There is a limit such as the spreadability of the carbon fiber bundles deteriorated. In particular, in the manufacturing process of the untwisted carbon fiber bundle, the fact that the flame-resistant fiber is made to have a bundling property and then produced is hardly studied.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, that is, in the step of continuously producing carbon fibers, the roller of the fiber bundle in the flameproofing step. The purpose of this is to prevent the fiber bundle from flaking due to repeated contact, and to prevent the fiber bundle from fluffing and winding around the next process roller. Another object of the present invention is to provide a carbon fiber having excellent quality.

[0005]

In order to achieve the above object, the present invention has the following constitution. That is, it is a continuous production method of carbon fibers, which comprises carbonizing after imparting water to a flameproof fiber bundle obtained by flameproofing a precursor fiber bundle.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the present invention, as the precursor fiber bundle,
A fiber bundle made of polyacrylonitrile (hereinafter abbreviated as PAN type), pitch, rayon or the like can be used, but it is particularly preferable to use a PAN type fiber bundle because it is easy to obtain high-strength carbon fibers. Further, the present invention, by using a so-called untwisted precursor fiber bundle, which is substantially untwisted,
It can be applied to the case of producing a non-twisted carbon fiber bundle or the case of producing a carbon fiber bundle using a twisted precursor fiber bundle fiber, but in the production of a non-twisted carbon fiber bundle having poor focusing properties. It produces a greater effect.

The term "flame-proof fiber bundle" means that the precursor fiber bundle is about 200 in the above-mentioned carbon fiber manufacturing process.
It is a fiber obtained by heating in an oxygen-containing atmosphere such as air at 300 ° C.

In the present invention, water is applied to the flame-resistant fiber bundle before carbonizing the fiber bundle. The water used in the present invention is preferably water of a water quality that does not substantially cause a chemical reaction as carbon in the carbonization step, for example, water containing few impurities such as alkali metals and alkaline earth metals, and purified by ion exchange or distillation. Good thing.

In the present invention, the dose of water into the fiber bundle is such that the flame-resistant fiber bundle can be imparted with a focusing property,
Specifically, the weight of the traveling flame-resistant fiber bundle is 0.
It is preferable to administer 1 to 2.0 times the weight ratio. If the dose of water is less than 0.1 times, the flame-resistant fibers will not be sufficiently bundled, and the amount of solution applied between yarns will easily vary. Further, if the amount of water administered is more than 2.0 times, the amount of water entering the carbonization step increases, and the problem of quality deterioration and fuzz formation tends to occur. Further, if a large amount of water enters the carbonization furnace, it is likely to cause a failure of the carbonization furnace equipment. In order to optimize the amount of water added to the fiber bundle, place a nip roller before the carbonization process, and squeeze the flame resistant fiber bundle entering the carbonization process with a nip roller to make it flame resistant. It is preferable to control the content of water in the fiber bundle.

Water can be applied to the flameproof fiber bundle by continuously spraying water, immersing the flameproof fiber bundle in water, or contacting the water-imparted roller with the flameproof fiber bundle. Etc., and is not particularly limited.

The location where water is applied to the flame-resistant fiber bundle is usually more effective when applied to the fiber bundle immediately after the flame-proofing step, but a plurality of driving points are provided between the flame-proofing step and the carbonization step. When a roller (hereinafter referred to as a drive station) is provided, it may be provided there.

The present invention exerts a greater effect when firing a plurality of yarns in parallel, but it is particularly effective when firing a yarn having a high yarn density of 500 filaments / mm or more. Easy to demonstrate. Here, the yarn density means the number of filaments of one yarn and the distance between adjacent yarns (m
Say the value divided by m). In addition, usually, the yarn density is preferably 5000 filaments / mm or less from the viewpoint of preventing fluffing of the yarn due to rubbing between adjacent yarns. Further, when the number of yarns is 50 or more, the application of the present invention exerts a further effect.

When a grooved roller is used in the drive station between the flameproofing process and the carbon process,
The effect of the present invention becomes more prominent when five or more drive rotating rollers or free rotating rollers are used between the flameproofing step and the carbonization step.

[0015]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, the fluff of the carbon fiber is 1
It is the number of fluffs when 0 m is visually observed, and the physical properties (strength) of the carbon fiber are JIS R-7601.
The physical properties of the resin-impregnated strand measured according to
It was determined from the average of the number of measurements N = 10.

(Examples 1 to 6) Single fiber fineness of 1 denier,
An untwisted PAN-based precursor having 12,000 filaments was run in parallel with 200 yarns and fired as follows to obtain an untwisted carbon fiber bundle. The carbon fiber manufacturing process includes a creel process, a flameproofing process, a carbonization process, and a post-treatment process.
A plurality of drive rollers (drive stations) for sending the yarn to the next step were arranged between the steps. Approximately 40 yarns drawn from the creel in an oxygen atmosphere at 250 ° C
Treated for minutes to make it flame resistant, then in a nitrogen atmosphere at 300 ° C
Then, the temperature is gradually increased from
Furthermore, after a surface treatment, a sizing agent application, and a post-treatment process of drying, the carbon fiber bundle was wound up with a winder.

FIG. 1 shows the arrangement of equipment from the flameproofing process to the carbonization process. The drive station arranged between the flameproofing process and the carbonization process has a grooved roller
The number of books and the number of flat rollers were 5, and the grooved rollers and the flat rollers were arranged alternately. As shown in FIG. 1, among the rollers arranged between the flameproofing process and the carbonization process, a water spray is installed on the roller portion closest to the flameproofing process, and all running yarns are subjected to ion exchange and filtration, Water, substantially free of impurities, was applied continuously. The amount of water is controlled by the valve of the water spray device and changed.
The number of times the yarn is wound around a plurality of rollers provided between the flameproofing step and the carbonization step when firing is continuously performed for 4 hours, and the fluff and mechanical properties of the obtained carbon fiber ( Strand strength) was evaluated. Table 1 shows the evaluation results.
Shown in

Comparative Example 1 A carbon fiber bundle was obtained and evaluated in the same manner as in Example except that water was not applied to the flameproof fiber bundle. Table 1 shows the evaluation results.

[0019]

[Table 1] The symbols in Table 1 mean the following.

A: Flame resistant fiber amount per unit time (kg)
Ratio of water (liter) to: B: Frequency of winding of yarn around the driving roller and the free roller during the flameproofing process and the carbonization process (number / 24
Time) C: Number of fluffs of the obtained carbon fiber (pieces / 10 m) D: Strength of the obtained carbon fiber (MPa)

[0021]

According to the production method of the present invention, by converging the flame-resistant fiber bundle, the winding of the yarn in the carbon fiber production process is greatly reduced, the production efficiency is improved, and the obtained carbon fiber bundle is obtained. A high-quality product with less fluff can be obtained, which in turn contributes to an improvement in the handling property of the carbon fiber bundle during high-order processing.

[Brief description of drawings]

FIG. 1 is a schematic side view of a flameproofing process, a drive station, and a carbonization process in the present invention.

[Explanation of symbols]

 1: Water spray 2: Water spray water control valve 3: Water spray water meter (rotor meter) 4: Drive station 4a, 4c, 4e, 4g, 4i: Grooved rollers 4b, 4d, 4f, 4h, 4j: Flat roller

Claims (2)

[Claims] 1. A method for continuously producing carbon fibers, which comprises carbonizing carbonization after applying water to a flameproof fiber bundle obtained by flameproofing a precursor fiber bundle. 2. The continuous production method for carbon fibers according to claim 1, wherein a plurality of precursor fiber bundles are run in parallel with a yarn density of 500 filaments / mm or more.