JPH0491229A - Production of pitch-based carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber by infusiblizing pitch fiber, stretching, the infusiblized fiber simultaneously with heat-treating under a specific condition, pre-carbonizing, carbonizing and graphitizing to prevent fiber break in a pre- carbonizing furnace and reduce degree of fusion and agglutination of pre- carbonized fiber. CONSTITUTION:Pitch fiber obtained by spinning of carbonaceous pitch is infusiblized and the infusiblized fiber is subjected to heat treatment by passing through an oxygen-containing atmosphere at 300-500 deg.C, preferably 350-480 deg.C for 1-200sec, preferably 10-100sec simultaneously with stretching at 50-100% by applying tension to the infusiblized fiber, then pre-carbonized, carbonized and graphitized to afford the aimed fiber.

Description

[Detailed Description of the Invention] No. 1 The present invention generally refers to carbon fibers (in this specification, unless otherwise specified, "carbon fibers" is used to include not only carbon fibers but also graphite fibers). The present invention relates to a method for producing carbon fibers from various carbonaceous pitches, and particularly to a method for producing carbon fibers from various carbonaceous pitches extremely efficiently and in large quantities.

[釆Ω且I Pitch-based carbon fibers manufactured from carbonaceous pitches such as petroleum-based pitch and coal-based pitch have a lower carbonization rate than rayon-based and PAN-based carbon fibers, which are currently produced in large quantities. It has attracted attention in recent years because it has a high modulus, excellent physical properties such as elastic modulus, and can be manufactured at low cost.

Currently, pitch-based carbon fibers are produced by: (1) preparing carbonaceous pitch suitable for carbon fiber from petroleum-based pitch, coal-based pitch, etc., heating and melting the carbonaceous pitch, spinning it in a spinning machine, and converging it; (2) The pitch fibers are heated to 150 to 350°C in an oxidizing atmosphere in an infusible furnace to make them infusible. (3) The infusible fibers are then carbonized. It is manufactured by heating to 3000°C or less in a furnace under an inert atmosphere to carbonize or graphitize it.

However, depending on the conventional technology, pitch fibers and infusible fibers have a low tensile strength of approximately 0.01 GPa and are brittle, making them difficult to handle. It was extremely difficult to obtain it in large quantities.

As one method to solve these problems, the present inventors have developed a method of increasing the strength of fiber bundles by doubling pitch fibers obtained by spinning carbonaceous pitch and applying a straight oil. proposed a method of making the fiber bundle infusible by passing it continuously in a linear manner in a hydrogen chloride gas having an oxygen concentration of 30% or more (see JP-A-63-264917).

However, the infusible fibers were linearly passed through a preliminary carbonization process in which the temperature was raised to 500 to 1000°C in an atmosphere of chemically inert argon or nitrogen gas to perform initial carbonization. In some cases, as disclosed in JP-A-59-15517, by the time the temperature of the fiber bundle reaches 700 to 800°C, the strength of the fiber bundle is significantly reduced from the strength at room temperature, A major drawback was that the fiber bundles were easily cut in the furnace during the preliminary carbonization process and became fluffy.

The invention described in JP-A No. 63-264917 cannot fundamentally solve this problem, and in the pre-carbonizing furnace, the infusible fibers frequently break in the furnace, and the yarn threading yield decreases. There was a problem in that it deteriorated and fuzzed easily.

Furthermore, one infusible fiber is in the form of a fiber bundle Q, which is made up of 100 to 100,000 filaments, and therefore, each filament may fuse or stick together during preliminary carbonization. This resulted in a major drawback in that the quality of the carbon fiber product after firing treatment was affected.

One way to improve the yarn breakage in the pre-carbonization furnace is to increase the degree of infusibility of the infusible fibers in the infusibility furnace, but as a result of research experiments conducted by the present inventors, According to this method, the physical properties of the carbon fiber deteriorated, and it was found that this method was not suitable.

In the process of researching a method for producing carbon fibers using a continuous firing process, the present inventors heat-treated normally infusible fibers in a high-temperature oxygen-containing atmosphere, and then By pre-carbonizing, breakage of the infusible fibers in the pre-carbonization furnace is prevented and threading yield is improved, and furthermore, the degree of fusion and agglutination of the pre-carbonized fibers is reduced, resulting in high quality carbon fibers. It was discovered that it is possible to produce

Furthermore, surprisingly, during such heat treatment,
By heat-treating the infusible fibers and simultaneously applying tension to the infusible fibers and drawing them, the physical properties of the resulting carbon fibers, that is, the tensile strength and tensile modulus, are dramatically improved, and the compressive strength is also increased. I discovered that.

The present invention has been made based on this new knowledge.

Therefore, it is an object of the present invention to prevent yarn breakage of infusible fibers in a pre-carbonizing furnace, improve yarn threading yield, reduce the degree of fusion stickiness of pre-carbonized fibers, and achieve high tensile strength. An object of the present invention is to provide a method for producing pitch-based carbon fibers for producing high-quality carbon fibers having high tensile modulus and high compressive strength.

Another object of the present invention is to reduce the preliminary carbonization time from 115 to
It is an object of the present invention to provide a method for producing pitch-based carbon fibers that can be shortened to about 1/10 and efficiently produce carbon fibers having high tensile strength, high tensile modulus, and high compressive strength.

The above-mentioned objectives are achieved by the method for producing pitch-based carbon fiber according to the present invention. In summary, the present invention involves infusible pitch fibers obtained by spinning carbonaceous pitch, and heat-treating the infusible infusible fibers by passing them through an oxygen-containing atmosphere at 300 to 500°C for 1 to 200 seconds. However, at the same time, tension is applied to the infusible fibers and a stretching treatment of 5 to 100% is performed, followed by preliminary carbonization, and then carbonization or black complexation. It is.

That is, according to the present invention, in a method for producing carbon fibers by a continuous firing process, normally infusible fibers are exposed to oxygen at a high temperature, that is, from 300 to 500°C, preferably from 350 to 480°C. For a very short time in a containing atmosphere,
That is, heat treatment is performed for 1 to 200 seconds, preferably 10 to 100 seconds, and at the same time tension is applied to the infusible fibers to stretch them by 5 to 100%, followed by preliminary carbonization. This prevents the infusible fibers from breaking in the pre-carbonization furnace and improves the threading yield. Further, according to the present invention, the degree of fusing and agglutination of the pre-carbonized fibers after the pre-carbonization treatment is reduced, and therefore the degree of fusing and agglutination of the carbon fibers after the subsequent carbonization or graphitization treatment is reduced and extremely high. You can get quality carbon fiber. At the same time, according to the present invention, since the infusible fibers are heat-treated and stretched at the same time by applying tension to the infusible fibers, the physical properties of the obtained carbon fibers, that is, tensile strength and tensile modulus, are dramatically improved. Not only does the compressive strength increase.

The reason why the manufacturing method of the present invention can achieve the above-mentioned effects is considered to be due to the following reasons.

In other words, before pre-carbonizing the infusible fibers,
By performing heat treatment in an oxygen-containing atmosphere at 00 to 500°C for 1 to 200 seconds, only the thread surface of the infusible fiber is selectively oxidized, and the inside of the thread undergoes further thermal polymerization due to high temperature heat. As a result, the infusible fiber consisting of a large number of filaments becomes stronger, and during the subsequent preliminary carbonization treatment, yarn breakage in the furnace is prevented, the threading yield is improved, and at the same time, the degree of fusion and agglutination on the yarn surface is reduced. It is thought that this will reduce the Furthermore, according to the present invention, the infusible fiber is oxidized before preliminary carbonization, but only the surface of the thread is oxidized, so the physical properties of the carbon fiber product are not deteriorated.

Further, according to the present invention, only the yarn surface of the infusible fiber is selectively oxidized, and thermal polymerization further progresses inside the yarn, resulting in an increase in the strength of the infusible fiber. It is thought that applying tension to the fibers, that is, making it possible to perform a drawing process, improves the orientation of the fibers and improves the physical properties of the resulting carbon fibers.

Next, the method for producing pitch-based carbon fiber according to the present invention will be explained in more detail.

First, carbonaceous pitch can be spun by methods well known to those skilled in the art. For example, by heating and melting carbonaceous pitch suitable for manufacturing carbon fiber such as petroleum-based pitch and coal-based pitch,
2000 filaments, preferably 50 to 1000 filaments are spun, and a sizing agent is applied to each filament using a commonly used oiling roller to bundle these many filaments into one yarn. It is wound onto a bobbin.

Examples of the sizing agent include water, alcohols such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol, or alcohols with a viscosity of 5 to 1000 cs.
Dimethylborisiloxane, alkylphenylpolysiloxane, etc. at 25℃ are mixed with low boiling point silicone oil (
Polysiloxane) or diluted with a solvent such as paraffin oil, or dispersed in water with an emulsifier added; Similarly, graphite or polyethylene glycol or hindered esters are dispersed; surfactants are diluted with water. It is also possible to use other ordinary fibers, such as those that do not harm pitch fibers among the various oils used for polyester fibers.

The amount of the sizing agent applied to the pitch fibers is usually 0.01 to 1% by weight, particularly preferably 0.05 to 5% by weight.

The yarn consisting of a large number of filaments once wound onto bobbins as described above can be unwound by simultaneously unwinding a plurality of bobbins, for example, 2 to 50 bobbins, or by dividing it into multiple times, for example, the first time. By repeatedly unwinding and doubling 2 to 10 yarns, then the remaining yarn,
2 to 50 yarns are bundled (paired) to make 100 to 1ooo
oo filaments, preferably 500 to 10,000 filaments to a pitch fiber bundle (hereinafter simply referred to as "pitch fiber")
) is produced and wound onto another bobbin.

During such doubling, a heat-resistant oil agent is applied to the pitch fibers in consideration of treatments during infusibility and preliminary carbonization. As the heat-resistant oil agent, alkylphenylpolysiloxane is preferable, and the phenyl group content is 5 to 80%, preferably 10 to 50%.
In addition, the alkyl group is preferably a methyl group, ethyl group, or propyl group, and the same molecule may contain two or more types of alkyl groups. Also, the viscosity is 10 to 10 at 25°C.
00cst is used. Furthermore, an antioxidant as described later can also be added.

Other preferred oils include dimethylpolysiloxane containing an antioxidant, and a viscosity of 5 to 1 ooocst at 25°C is preferred.As the antioxidant, amines, organic selenium compounds, etc. , phenols, etc., such as phenyl-α-naphthylamine, dilaurylselenide, phenothiazine, iron octolate, and the like. As mentioned above, these antioxidants can also be added to the alkylphenylpolysiloxane for the purpose of further increasing heat resistance.

Further, as preferred oils, each of the above oils has a boiling point of 60.
It is also possible to use an emulsified product using a surfactant having a temperature of 0° C. or lower. At this time, as the surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene modified silicone,
Polyoxyalkylene-modified silicones and the like may be used.

These oil agents are applied to the pitch fibers in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, by roller contact, spray coating, foam coating, or the like.

As mentioned above, by applying a heat-resistant oil agent to the pitch fibers that have been doubled, the strength of the pitch fibers becomes significantly stronger and the yarn handling properties are greatly improved.

The pitch fibers produced as described above are unwound from a bobbin and sent to an infusibility furnace.

The temperature inside the infusibility furnace can be set at a constant temperature within the range of 150 to 350°C, but it should be set so that it has a temperature gradient that gradually increases from 150°C to 350°C from the furnace inlet to the furnace outlet. You can also do it.

In addition, the inside of the infusibility furnace is made into an oxidizing atmosphere, and oxidizing gas such as air, oxygen, a mixed gas of air and oxygen, or air and nitrogen is supplied into the infusibility furnace, and a preferable gas is an oxygen concentration of 30 ~90% oxygen rich gas is used.

According to the present invention, the infusibility treatment can be carried out without applying any tension to the fiber bundle, but the slackness of the fiber bundle in the infusibility furnace can cause drag scratches caused by rubbing the furnace bottom and furnace wall. In order to prevent carbon fibers from occurring, to have a good appearance, and to improve the physical properties of carbon fibers such as tensile strength and tensile modulus, it is preferable to carry out infusibility while applying a tension of 0.001 to 0.2 g per filament.

In this way, the infusible fibers are infusible so that the oxygen concentration is 7 to 12% by weight.

According to the present invention, the infusible fibers having an oxygen concentration of 7 to 12% by weight, which have been infusible as described above, are heat-treated before being sent to the pre-carbonization furnace and subjected to the pre-carbonization treatment. .

The temperature in the heat treatment furnace is 100 to 200 degrees lower than the infusibility temperature.
A higher temperature is preferable, and is generally set at a constant temperature within the range of 300 to 500°C, for example, it can be 450°C, but it should be set so that it has a temperature gradient that gradually increases from the furnace inlet to the furnace outlet. Also, the maximum temperature in this case should not exceed 300-500°C. For example, the temperature at the furnace inlet may be set to 350°C, and the temperature may be set to gradually increase to 500°C at the furnace outlet. If the heat treatment temperature exceeds 500°C, the oxidation of the infusible fibers will be excessive, which is undesirable. If the heat treatment temperature is less than 300°C, the heat treatment time will become longer or the surface oxidation of the infusible fibers will be insufficient. It is difficult to obtain the desired effect.

Further, the inside of the heat treatment furnace is set to have an oxygen-containing atmosphere, and air, a mixed gas of air and oxygen, or nitrogen and oxygen is supplied into the furnace, and the oxygen concentration is 5 to 80%, preferably 10 to 50%.
It is said that Generally, air is preferred. Depending on the case, a mixed gas containing air containing No, So, C°C2, etc. may be used.

Further, according to the present invention, the residence time of the infusible fibers in the heat treatment furnace is 1 to 200 seconds, preferably 10 to 200 seconds.
It is 100 seconds. The residence time is set in relation to the above heat treatment temperature; if it exceeds 200 seconds, the oxidation of the infusible fibers will be excessive even if the heat treatment temperature is set to 300°C, which is undesirable, and if it is less than 1 second, the heat treatment temperature will not exceed 500°C. However, the surface oxidation of the infusible fibers becomes insufficient, making it difficult to obtain the expected effect.

Furthermore, according to the present invention, at the same time as the above heat treatment, tension is applied to the infusible fibers and a stretching process of 5 to 100% is performed. Therefore, the tension applied to the infusible fibers is usually 10 to 500 g/3000 filaments, that is, 0.003 to 0.17 g per filament.

Stretching may be set by adjusting the magnitude of tension, or may be adjusted by differential movement of two or more rolls.

With the above structure, only the yarn surface of the infusible fiber is selectively oxidized, and thermal polymerization due to high temperature heat further progresses inside the yarn, and as a result, the strength of the infusible fiber consisting of a large number of filaments increases. . Therefore, according to the present invention, the infusible fiber is oxidized before preliminary carbonization, but only the surface of the thread is oxidized, so the physical properties of the carbon fiber product are not deteriorated.

Further, according to the present invention, by oxidizing the surface of the infusible fiber, the degree of fusion adhesion on the yarn surface of the infusible fiber in the subsequent pre-carbonization furnace is reduced, and the quality of the carbon fiber is improved. At the same time, the preliminary carbonization time is 115 to 1
It was found that the time can be shortened to about /10.

Furthermore, according to the present invention, only the yarn surface of the infusible fiber is selectively oxidized, and thermal polymerization further progresses inside the yarn, resulting in an increase in the strength of the infusible fiber. By stretching the fused fibers, the orientation of the fibers is improved, and the physical properties of the resulting carbon fibers are improved.

Next, the infusible fibers that have been heat-treated and drawn in this way are sent to a pre-carbonization furnace and subjected to a pre-carbonization process.

The inside of the preliminary carbonization furnace is heated to a maximum temperature of 500 to 1100° C., and chemically inert nitrogen gas or argon gas is supplied to create an inert atmosphere inside the furnace.

The infusible fibers threaded through such a pre-carbonization furnace are pre-carbonized to obtain pre-carbonized fibers having a strength of about 0.2 GPa or more and an elastic modulus of about 4 GPa or more.

According to the present invention, as described above, the preliminary carbonization time is 115% compared to the preliminary carbonization treatment time according to the conventional manufacturing method.
It was found that the time can be shortened to about 1/10.

The pre-carbonized fibers are then fed to a carbonization furnace. Carbonization furnace at 1000-2000'C or 1000-2000'C
The furnace is heated to 3000° C., and chemically inert nitrogen gas or argon gas is supplied to create an inert atmosphere inside the furnace.

The pre-carbonized fibers passed through a carbonization furnace where the temperature was raised to 1500℃ are carbonized and have a strength of about 2℃ or more, 5GPa or more.
Carbon fibers with an elastic modulus of about 200 GPa or more are obtained, and the pre-carbonized fibers passed through a carbonization furnace where the temperature is raised to 3000°C are graphitized, and carbon fibers with a strength of about 3.0 GPa or more and an elastic modulus of about 500 GPa or more are obtained. Graphite fibers are obtained.

Incidentally, the infusible fibers have been explained as linear pitch fibers that are continuously infusible, but can-shaped fibers (pitch fibers placed in a wire mesh container and deposited, or similar) The present invention can be carried out in the same manner, and the same effects can be achieved with the following methods: those made infusible by placing pitch fibers on a mesh belt, or made infusible while still being wound on a bobbin.

Hereinafter, the method for producing pitch-based carbon fiber according to the present invention will be described with reference to Examples.

Example 1 In producing pitch fiber, an optically anisotropic phase of about 55%
% and a softening point of 232° C. was used as the precursor pitch. This precursor pitch was centrifuged to successively separate pitches containing many optically anisotropic phases and pitches containing many optically isotropic phases, and each was extracted.

The resulting pitch contained 98% of the optically anisotropic phase, the softening point was 270°C, and the quinoline solubility was 30.0%. 500
Melt spinning machine with hole spinneret (nozzle hole diameter: diameter 0
．． 3 mm) and was extruded and spun at 355° C. under a nitrogen gas pressure of 200 mmHg.

The 500 spun filaments are roughly converged by an air sucker and guided to an oiling roller, with a ratio of about 0.2 to the yarn.
A focusing oil was supplied in a proportion of 500% by weight to form a pitch fiber consisting of 500 filaments. As an oil agent, 25
A methylphenylpolysiloxane having a viscosity of 14 cst at °C was used.

The pitch fibers were wound onto a stainless steel bobbin with a diameter of 210 mm and a width of 200 mm that was provided at the bottom of the nozzle and rotated at high speed, and spun for 10 minutes at a winding speed of about 500 m/min. The pitch of the traverse per revolution of the bobbin was 10 mm/rotation. No yarn breakage occurred during spinning.

Next, the six bobbins wound with pitch fibers were unwound,
Then, the fibers were combined using an oiling roller while applying a heat-resistant oil to form a pitch fiber (bundle) consisting of 3,000 filaments, which was wound onto another stainless steel bobbin.

Methylphenylpolysiloxane (phenyl group content: 45 mol %) of 40 cst at 25° C. was used as an oil agent during yarn doubling. The amount applied was 0.5% to the yarn.

While unwinding the bobbin-wound pitch fiber thus obtained from the bobbin, the furnace inlet temperature was 180°C, and the maximum temperature was 295°C.
Oxygen-rich atmosphere with a temperature gradient of (oxygen/nitrogen = 60/4
0) was continuously introduced in a linear manner into the continuous infusibility furnace. The temperature increase rate was 6° C./min, and the infusibility time was 19 minutes. The tension applied to the fiber bundle is 0.007 g per 1 filament.
(20 g for a fiber bundle of 3000 filaments). The oxygen concentration of the infusible fiber after infusibility was 9.5% by weight.

During the infusibility process, the pitch fibers were unraveled from the bobbin smoothly, and the infusibility treatment was carried out smoothly without any breakage of the fiber bundle in the infusibility furnace.

The thus obtained infusible fibers were supplied to a heat treatment furnace maintained at 450° C. before being threaded to a pre-carbonization furnace. The fiber bundle has a tension of 0.00 per filament.
7g added. Air was introduced into the furnace.

With the above configuration, the time required to heat treat the infusible fibers was 25 seconds.

The heat treatment was carried out smoothly without any breakage of the fiber bundle in the heat treatment furnace. The stretching ratio of the yarn in this heat treatment was 20%.

The fibers heat-treated in this oxygen-containing atmosphere were linearly and continuously introduced into a pre-carbonization furnace having a temperature gradient of 600° C. at the furnace entrance and 900° C. at the maximum temperature.

The atmosphere inside the furnace was a nitrogen atmosphere. A tension of 0.007 g per filament was applied to the fiber bundle. Preliminary carbonization time was 25 seconds.

Although the treatment was continued for 24 hours, no yarn breakage or breakage occurred in the furnace during this period.

This pre-carbonized fiber was heated to 1500° C. in a nitrogen gas atmosphere to obtain carbon fiber. Carbon fiber thread diameter is 8.8μm
The tensile strength is 3°3GPa and the tensile modulus is 330.
GPa, and the compressive strength was 1.2 GPa. Further, the degree of fusion and adhesion of this carbon fiber was 6%.

In addition, graphite carbon fiber obtained by heating carbon fiber to 2500°C in an argon gas atmosphere has a thread diameter of 8.7 μm, a tensile strength of 3°9 GPa, and a tensile modulus of 810 GPa.
, the compressive strength was 0.5 GPa. Further, the degree of fusion and adhesion of this graphite fiber was 10%.

In this specification, the degree of fusion adhesion (%) is determined by cutting a fiber bundle consisting of 3000 filaments to a width of 3 mm, immersing it in ethanol, blowing air for 30 seconds, and then melting it under a microscope at 20x magnification. It is determined by the following formula by counting the total number (N) of stuck filaments.

Melting adhesion degree = (N/3000)
The treatment was carried out in the same manner as in Example 1, except that the heat treatment was performed for seconds.

In this case, the fiber bundle broke in the furnace during the heat treatment, making it impossible to obtain long fibers.

Comparative Example 2 In Example 1, the infusible fibers were directly and continuously introduced into the pre-carbonization furnace in a linear manner without being subjected to heat treatment prior to pre-carbonization to perform pre-carbonization. The preliminary carbonization furnace had a temperature gradient with a furnace inlet temperature of 400°C and a maximum temperature of 900°C, and the preliminary carbonization treatment was performed for 250 seconds. A tension of 0.007 g per filament was applied to the fiber bundle. Other than that, the process was the same as in Example 1.

In case 2, there was no yarn breakage in the preliminary carbonization furnace, and continuous operation for one hour was possible. However, the obtained pre-carbonized fiber had a lot of fuzz.

This pre-carbonized fiber was heated to 1500° C. in a nitrogen gas atmosphere to obtain carbon fiber. Carbon fiber thread diameter is 9.8μm
The tensile strength is 2°6 GPa and the tensile modulus is 270.
GPa, and the compressive strength was 1.0 GPa. Further, the degree of fusion and adhesion of this carbon fiber was 15%.

Furthermore, graphite carbon fiber obtained by heating carbon fiber to 2500°C in an argon gas atmosphere has a thread diameter of 9.7 μm, a tensile strength of 3.3 GPa, and a tensile modulus of 690 GPa.
a. The compressive strength was 0.4 GPa. Further, the degree of fusion and adhesion of this graphite fiber was 35%.

Example 2 In Example 1, the heat treatment performed prior to pre-carbonizing the infusible fibers was carried out at a rate of 0.033 g per filament.
The process was carried out in the same manner as in Example 1, except that a tension of . The stretching ratio at this time was 40%.

When this fiber was subjected to the next pre-carbonization treatment, there was no yarn breakage in the pre-carbonization furnace during 24 hours of continuous operation, and the obtained pre-carbonized fiber had almost no fuzz.

This pre-carbonized fiber was heated to 1500° C. in a nitrogen gas atmosphere to obtain carbon fiber. Carbon fiber thread diameter is 8.4μm
The tensile strength is 3°7 GPa and the tensile modulus is 340.
It was GPa.

Further, the degree of fusion and adhesion of this carbon fiber was 7%.

Further, graphite carbon fiber obtained by heating carbon fiber to 2500° C. in an argon gas atmosphere had a thread diameter of 8.3 μm, a tensile strength of 42 GPa, and a tensile modulus of 850 GPa.

Further, the degree of fusion and adhesion of this graphite fiber was 12%.

1. Mamerikou 1 As explained above, the method for producing pitch-based carbon fibers according to the present invention has a structure in which the infusible fibers are heat-treated at high temperature for a short period of time before being pre-carbonized, and at the same time, they are subjected to a drawing treatment. In order to prevent the infusible fibers from breaking in the pre-carbonization furnace,
It is possible to improve the threading yield, further reduce the degree of fusion and agglutination of pre-carbonized fibers, and produce high-quality carbon fibers with high tensile strength, high tensile modulus and high compressive strength,
Furthermore, the preliminary carbonization time can be shortened to about 115 to 1/10 of the conventional time, and carbon fibers having high tensile strength, high tensile modulus, and high compressive strength can be efficiently produced.

Claims (1)

[Claims] 1) Infusible pitch fibers obtained by spinning carbonaceous pitch are heat-treated by passing the infusible fibers through an oxygen-containing atmosphere at 300 to 500°C for 1 to 200 seconds. 5-1 by applying tension to the melted fiber
1. A method for producing pitch-based carbon fiber, which comprises subjecting it to a 00% stretching treatment, followed by preliminary carbonization, and then carbonization or graphitization.