JPS62133121A - Production of pitch carbon fiber - Google Patents

Abstract

PURPOSE:Pitch fibers are preoxidized in an oxidative gas atmosphere, precarbonized under specific conditions, then the fibers are stacked in a refractory container and sent to the carbonizer or graphitizer to produce the titled fibers of high performance and high productivity. CONSTITUTION:First, carbonaceous pitch, preferably petroleum pitch is melt- extruded into fibers and the fibers are preoxidized in an oxidative gas atmosphere, preferably air or oxygen containing 0.1-20vol% of nitrogen dioxide, preferably at 100-350 deg.C. Then, the preoxidized fibers are precarbonized in an inert gas atmosphere at a temperature lower than 800 deg.C and placed in a heat-resistant or refractory container so that the bulk density of the fibers becomes 0.01-0.2g/cm<3>. The containers are continuously sent into the carbonizer or graphitizer to effect carbonization or graphitization whereby the objective fibers are obtained. The material of the containers is preferably stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing pitch-based carbon fibers, and particularly to a method for efficiently producing high-performance carbon fibers.

The title that the conventional - and would do.

Pitch-based carbon fibers are produced by subjecting pitch fibers obtained by melt-spinning carbonaceous pitch to infusibility, carbonization, or further graphitization.

However, the production costs required for carbonization and graphitization are extremely high, which inevitably leads to high prices, and despite its high performance, the uses of carbon fiber are limited.

The present invention provides a method for manufacturing carbon fibers with high productivity, that is, at a lower cost than conventional methods, by improving the efficiency of carbonization and graphitization steps.

Conventionally, various processes have been proposed for the purpose of improving productivity (Japanese Patent Application Laid-Open No. 58-60019゜60-2191)
1) These methods have not reached the point where carbon ta fibers with high performance and excellent productivity as in the present invention can be obtained.

Mouth 1. The present invention is to produce carbon fibers with high performance and excellent productivity. That is, the present invention (11) pitch m fibers obtained by melt spinning carbonaceous pitch are infusible in an oxidizing gas atmosphere, and the infusible m fibers are infusible in an inert gas atmosphere.
After pre-carbonizing in a temperature range of 00°C or lower, the pre-carbonized fibers are placed in a heat-resistant or refractory container with a bulk density of 0.0.
A method for producing pitch-based carbon fiber, characterized by depositing it naturally or regularly so that it becomes 1 to 0.20 g/ew +, and then continuously feeding the container to a carbonization or graphitization device, and ( 2) Pitch fibers obtained by melt-spinning carbonaceous pitch are naturally or regularly deposited in an oxidation-resistant container and treated to be infusible in an oxidizing gas atmosphere, and the infusible fibers are heated to 800% in an inert gas atmosphere. After pre-carbonizing in a temperature range below ℃, the pre-carbonized fibers are placed in a heat-resistant or refractory container with a bulk density of 001 to 0.20.
The present invention relates to a method for producing pitch-based carbon fiber, which is characterized in that it is deposited naturally or regularly in a manner such that g/c+/ is deposited, and then the container is continuously fed into a carbonization or graphitization device.

The carbonaceous pitch used in the present invention includes various pitches such as coal tar pitch, coal-based pitch such as SRC, petroleum-based pitch such as ethylene tar pitch, and decant oil pitch, or synthetic pitch, but especially petroleum-based pitch. is preferred.

Modified pitch, for example treated with a hydrogen donor such as tetralin, 20-350 kg/c/
Various modified pitches such as those hydrogenated under hydrogen pressure, those modified by heat treatment, and those modified by an appropriate combination of these methods are also considered carbonaceous pitches in the present invention.

That is, the carbonaceous pitch of the present invention is used to generically refer to precursor pitch that can form pitch fibers.

The carbonaceous pitch of the present invention may be an optically isotropic pitch or an optically anisotropic pitch.

Optically anisotropic pitch means that the pitch is usually heated to 340 to
It is a pitch containing an optically anisotropic phase (so-called mesophase) obtained by heat treatment at 450°C, and in particular, one having a mesophase content of 5 to 100%, preferably 60 to 100% is preferable.

The carbonaceous pitch used in the present invention has a softening point of 240 to 400.
℃ is preferable, and 260 to 300℃ is particularly preferable.

Pitch fibers are obtained by melt-spinning the carbonaceous pitch by a known method. For example, carbonaceous pitch is melted at a temperature 30 to 80°C higher than its softening point, and is extruded through a nozzle with a diameter of 0.1 to 0.5 gates to
The pitch fibers are obtained by winding at ~2000 m/min or by natural or regular deposition on an oxidation-resistant container.

When depositing pitch fibers on a container, the pitch to be deposited is l! ! The number of miscellaneous items is 10 to 20,000 per east.
books, preferably 100 to 10,000 books. Also, its bulk density is 001~0.20g/en? , preferably 0.05 to 0.15 g/car. If the bulk density does not fall within the above range, the fiber deposits will move during processing and suffer losses. On the other hand, if the bulk density exceeds the above range, the fibers may coalesce together due to thermal decomposition components generated during heat treatment. The oxidation-resistant container mentioned here may be any container made of a material that can withstand infusibility and pre-carbonization treatment conditions, but is not limited to the following.
For example, stainless steel or ceramic with bubbles can be preferably used.

The infusibility treatment of pitch fibers is usually carried out at a temperature of 400°C or lower, preferably 50 to 380°C, more preferably 100 to 350°C. If the processing temperature is too low, the processing time becomes long, and if the processing temperature is too high, phenomena such as fusion of pitch contaminants or consumption occur, which is not preferable. As the oxidizing gas, one or more oxidizing gases such as oxygen, ozone, air, nitrogen oxides, sulfur gas, or halogens are usually used. Air or oxygen containing % by volume is preferred. Also, the processing time is 1 minute ~
20 hours, preferably 2 minutes to 10 hours.

The infusible fibers were heated at 800°C under an inert gas atmosphere.
Below, preferably 400 to 700°C, more preferably 4
It is processed at 50 to 600°C to obtain pre-carbonized fibers. Although the treatment time is not limited, it is usually 10 seconds to 2 hours, preferably 1 minute to 1 hour.

The precarbonized fibers are deposited naturally or regularly in a heat-resistant or refractory container, which is subsequently fed into a carbonizer or graphitizer. The number of pre-carbonized fibers deposited on the container is 10 to 20 per bundle.
000, preferably 100 to 10,000. In addition, its bulk density is 0.01~020g/cl,
Preferably 0.0S to 0.0S. ISg/ct+! It is. If the bulk density is less than the above range, the fiber deposits will migrate and be damaged during heat treatment. On the other hand, if the bulk density exceeds the above range, the ta particles may coalesce together due to thermal decomposition components generated during heat treatment. The material of the heat-resistant or refractory container referred to herein is not limited to any material as long as it can withstand the above conditions, but for example, refractories such as stainless steel, ceramic with bubbles, carbon, and graphite materials are preferably used.

Carbonization treatment is usually carried out at a temperature of 800 to 20°C under an inert gas atmosphere.
Perform at 00°C. Generally, the treatment time required for carbonization is 1 minute to 10 hours. When graphitizing is carried out, it is carried out at a temperature of 2000 to 3500° C. in an inert gas atmosphere for 1 second to 1 hour.

K give! EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Example 1 and Comparative Example 1] Optically anisotropic pitch having a softening point of 280°C was spun,
A pitch fiber bundle with an average yarn diameter of 12 μm was obtained.

This pitch fiber bundle was heated for 2 hours in air containing 5% N02.
After being infusible at 25°C for 1 hour, it was pre-carbonized at 700°C. Bulk density of 500g pre-carbonized fiber bundle is 0.10g/e
It was deposited in a graphite container so that it became Il, and was sent to the graphitization apparatus shown in FIG. 1, and treated at 2500°C for 10 seconds. The results are shown in Table 1 as Example 1. On the other hand, while applying tension to the pre-carbonized fibers, the fibers are fed out from the drawing device.
It was introduced into the graphitization apparatus shown in No. 2, and treated at 2500° C. for 10 seconds (Comparative Example 1). The results are shown in Table-1.

1 bow iFJEU (kmmm') 3
30 320 1 bow 9 bow birth rate 0 N/kaku 2) 65
67 string (μm) 9.
5 9.5 Processing amount 500g/
Graphitized m-fibers with almost the same performance can be obtained at a processing speed 250 times faster than the 1.6 g/10 second unwinding-winding method.

[Example 2 and Comparative Example 2] Optically anisotropic Bi-Sochi having a softening point of 265° C. was spun to obtain a pitch fiber bundle with an average yarn diameter of 12 μm.

This pitch fiber bundle was heated for 2 hours in air containing 5% NO2.
After being rendered invulnerable at 25°C for 1 hour, it was pre-carbonized at 700°C. Bulk density of 500g pre-carbonized fiber bundle is 0.15g/c
The mixture was deposited in a graphite container so as to have a temperature of d, and then fed into the graphitization apparatus shown in Figure 1, where it was treated at 2500°C for 20 seconds. The results are shown in Table 2 as Example 2. On the other hand, the pre-carbonized fiber is fed out with tension as shown in Figure-2.
It was introduced into the graphitization apparatus shown in Fig. 2 and treated at 2500°C for 20 seconds (Comparative Example 2). The results are shown in Table-2.

Table-2 Bow 1 tension rida ridge mark - υ depression 2) 320
315 pull 'J') ¥'R
Rate CmN/wn2) 70 68 Thread diameter (μm+) 9.5
9.5 fried rice 500 g/20
1.6 g/20 seconds Graphitized fibers with almost the same performance can be obtained with a processing degree of 250 times as compared to the edge-rolling-winding method.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of transition from pitch fiber to graphitized fiber, and FIG. 2 is a schematic diagram showing an example of transition from pre-carbonized fiber to graphitized fiber. ]・・Pitch fiber, 2...oxidation-resistant container,
3... Pre-carbonized fiber, 4... Refractory container, 5... Graphitization device, 6... Kurofune taa. Patent applicant Nippon Oil Co., Ltd. Agent Patent attorney Takeshi Saito Patent attorney Ryo Kawase Harutsu Figure-2

Claims (2)

[Claims] (1) Pitch fibers obtained by melt-spinning carbonaceous pitch are infusible in an oxidizing gas atmosphere, and the infusible fibers are pre-carbonized in an inert gas atmosphere at a temperature of 800°C or less. , the pre-carbonized fibers are naturally or regularly deposited in a container made of heat-resistant or refractory material to a bulk density of 0.01 to 0.20 g/cm^3, and then the container is continuously carbonized or deposited with graphite. 1. A method for producing pitch-based carbon fiber, which method comprises feeding the pitch carbon fiber into a oxidizing device. (2) Pitch fibers obtained by melt-spinning carbonaceous pitch are naturally or regularly deposited in an oxidation-resistant container, treated to be infusible in an oxidizing gas atmosphere, and the infusible fibers are placed in an inert gas atmosphere. After pre-carbonizing in a temperature range of 800°C or lower, the pre-carbonized fibers are naturally or regularly deposited in a heat-resistant or refractory container so that the bulk density is 0.01 to 0.20 g/cm^3. 1. A method for producing pitch-based carbon fibers, which comprises curing the container, and then continuously feeding the container into a carbonization or graphitization device.