JPH038809A - Production of carbon fiber and graphite fiber - Google Patents

Abstract

PURPOSE:To obtain the title filamentous fiber of both high mechanical strength and modulus with good appearance, good in its coherent winding, causing no fusing or sticking by imparting melt-spun carbonaceous pitch fiber with a specific cohering agent followed by infusibilization, carbonization and graphitization. CONSTITUTION:Melt-spun carbonaceous pitch fiber is imparted with, as cohering agent, an aqueous dispersion of an alkylphenylpolysiloxane (pref. containing 1-80mol% of phenyl group with the alkyl group being methyl, ethyl or propyl) 10-1000cst in viscosity at 25 deg.C, followed by infusibilization, carbonization and graphitization, thus obtaining the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing carbon fibers and graphite fibers from carbonaceous pitch. More specifically, the present invention relates to a method for producing long carbon fibers and graphite fibers by spinning carbonaceous pitch and subjecting it to infusibility, carbonization, and graphitization.

[Conventional technology]

Traditionally, in a wide range of technical fields related to automobiles, aircraft, and other industrial fields, there has been a demand for the development of high-performance materials with properties such as light weight, high strength, and high modulus of elasticity. Materials are attracting attention.

Currently, commercially available carbon fibers are still PAN-based carbon fibers made from polyacrylonitrile, but carbon fibers made from coal or petroleum pitches are cheaper raw materials, have a higher yield in the carbonization process, and have more elasticity. It is regarded as important due to its advantages such as the ability to obtain fibers with high fiber content, and active research and development efforts are being carried out.

However, depending on the conventional technology, the pitch fibers have a small tensile strength of about 0.01 GPa and are extremely brittle, so the static electricity generated when the pitch fibers are bundled in the spinning process causes the yarn to become loose and difficult to bundle. Also, during the infusibility process, carbonization process, etc., fusion and agglutination occur between fibers, resulting in fiber bundles being cut, fluffing, and being wrapped around rollers, making it difficult to handle the yarn.
It has been extremely difficult to obtain the long fibers necessary to obtain high performance products.

Therefore, various sizing agents (oil agents) have been proposed as means for solving these problems.

For example, Japanese Patent Publication No. 51-12379, Japanese Patent Publication No. 54-13
Publication No. 1032 discloses a method of using a silicone-based oil agent for flame-retardant treatment in the production of polyacrylonitrile-based carbon fibers. However, when this method is directly applied to carbonaceous pitch fibers, fusion and agglutination occur during the infusibility process, and the decomposition of the oil disturbs the convergence, causing the fibers to become tattered, resulting in fiber bundle breakage and fluffing. The desired effect may not be achieved due to the occurrence of problems such as generation and wrapping around the guide roller.

On the other hand, as a sizing agent for carbonaceous pitch fibers, a method using an aqueous solution of a water-soluble surfactant (Japanese Patent Publication No. 51-12740
No. 2) has been proposed. Although this method improves the cohesiveness of fibers during spinning, the infusibility process
When exposed to a high temperature of 0° C., the surfactant decomposes, deteriorates, or turns into tar, resulting in severe adhesion, resulting in frayed fibers and breakage of fiber bundles.

Further, as a sizing agent for carbonaceous pitch fibers, silicone oils having a viscosity of 2 to 10,000 cst at 25°C or diluted silicone oils with solvents are used (Japanese Patent Laid-Open No. 59-223315), One using dimethylpolysiloxane (dimethylsilicone oil) having a viscosity of 0.5 to 500 cst at 25°C (Japanese Patent Application Laid-Open No. 1986-88
No. 124) is disclosed. However, these methods use a solvent or low-viscosity silicone oil, which has no electrical conductivity, so when pitch fibers are bundled and wound during melt spinning, abnormal static electricity is generated due to friction of the threads, causing the bundled winding to fail. Not only is it difficult to remove the fibers, but the fibers tend to break and become fluffy, making operation difficult. Furthermore, there is a drawback that the threads are easily damaged due to the solubility of the solvent, and furthermore, the fibers are likely to fuse and stick together during the infusibility process, and the fibers are likely to become fluffy. Furthermore, since a low-boiling point solvent or silicone oil is used as a diluent, the diluent evaporates during work, which poses a major problem in terms of work and environmental protection, as well as high costs.

In addition, a method of emulsifying silicone oil with a surfactant and using it as a water emulsion type oil agent (Japanese Patent Application Laid-Open No. 61-70017
However, since the oil agent is conductive, this method avoids the problem of difficulty in converging and winding due to the generation of static electricity during spinning and winding. Due to the decomposition and deterioration of the bundled oil agent, the fibers become significantly stuck, the bundle becomes disordered, and the fibers lose their flexibility. This has the disadvantage that the fibers become tattered and the fiber bundles break, making it difficult to handle the yarn.

As a method to overcome these drawbacks, the present inventors first conducted a boiling point of 600% by distilling a nonionic surfactant under reduced pressure.
℃ or less (boiling point equivalent to atmospheric pressure) as an emulsifier, and an alkylphenylpolysiloxane with good heat and oxidation stability, which has a viscosity of 10 to 1000 cst at 25℃, is emulsified to form a water emulsion type oil agent. (Japanese Unexamined Patent Publication No. 133122/1982).

This sizing agent is a water emulsion-based oil and is electrically conductive, so it can avoid the problem of difficulty in focusing and winding due to static electricity generated during spinning and winding. It has the advantage of suppressing fusion and adhesion between fibers and making it easier to handle pitch fibers in the firing process.

The present inventors have further improved the surfactant to produce a polyoxyethylene alkyl ether with a higher performance boiling point of 600°C or lower (atmospheric pressure equivalent) and a polyoxyethylene alkyl ether with an added mole of oxyethylene of 6 or lower. one or more nonionic surfactants selected from the group of esters and polyoxyethylene alkylphenol derivatives;
proposed a sizing agent consisting of an alkylphenylpolysiloxane having a viscosity of 10 to 1000 cst at 5°C (Japanese Patent Application Laid-Open No. 63-288219).

[Problem to be solved by the invention]

However, the sizing agents described in JP-A-62-133122 and JP-A-63-288219 have good sizing and winding properties during spinning, and also induce cutting of pitch fiber bundles and fluffing during the infusibility process. Since no fusion or strong adhesion occurs, the fiber bundle has good thread handling properties, but since it contains a surfactant, pre-carbonization following the infusibility treatment,
During the carbonization and graphitization process, stickiness occurs in fiber bundles,
The disadvantage is that it increases.

In this specification, "fusion" refers to a state in which multiple filaments are bonded and integrated to the extent that they form a single tissue; "adhesion" refers to a state in which multiple filaments are simply in contact with each other. This means that the structures of each filament are not integrated but exist separately.

If there is a stalemate.

This is not preferable because it results in a decrease in the physical properties of the carbon fibers or a decrease in homogeneity when used as a composite material.

Therefore, an object of the present invention is to avoid the problem of difficulty in converging and winding due to the generation of static electricity during melt spinning, and also to form pitch fiber bundles without causing fusion, stiffness, or agglutination even during infusibility treatment. The yarn has good handling properties, and it can also be pre-carbonized and carbonized.

It is an object of the present invention to provide a method for producing pitch-based carbon fibers and graphite fibers that suppresses agglutination when subjected to graphitization treatment and that allows a product of high quality and high strength to be obtained after firing treatment.

[Means to solve the problem]

According to the present invention, in a method for producing carbon fibers and graphite fibers, in which a sizing agent is added to melt-spun carbonaceous pitch fibers and subjected to infusibility, carbonization, and graphitization treatment, the sizing agent is
Provided is a method for producing carbon fibers and graphite fibers, characterized in that an aqueous dispersion of alkylphenylpolysiloxane having a viscosity of 10 to 1000 cst is used.

The present inventors have found that, in a method for producing pitch-based carbon fibers and graphite fibers, the bundle winding is good during melt spinning, and pitch fiber bundles do not cause fusion or strong adhesion even during infusibility treatment. Pitch-based carbon fiber and graphite that have good yarn handling properties, prevent sticking when subjected to preliminary carbonization, carbonization, and graphitization treatments, and can yield high-quality, high-strength products after firing treatment. As a result of intensive studies on the method for manufacturing fibers, it was discovered that the above object can be achieved when the aqueous dispersion of the alkylphenylpolysiloxane (without addition of a surfactant) is used as a sizing agent, and the present invention has been achieved. It has been completed.

The present invention will be explained in more detail below.

(1) Carbonaceous pitch The carbonaceous pitch used in the present invention is not particularly limited, and includes coal tar pitch obtained by dry distilling coal;
Various pitches such as coal-based pitch such as coal liquefied products, naphtha cracked tar pitch, catalytic cracked tar pitch, petroleum-based pitch such as atmospheric distillation residue, vacuum distillation residue, synthetic pitch obtained by decomposing synthetic resin, or these. It is also possible to use pitch that has been hydrogenated with hydrogen or a hydrogen donor, or that has been modified by heat treatment, solvent extraction, etc. These carbonaceous pitches may be isotropic pitches or optically anisotropic pitches, such as neomesofaces.

Although the present invention can also be applied to pitches called pre-mesofaces, optically anisotropic pitches described below are particularly preferred.

Optically anisotropic carbonaceous pitch contains about 95% or more of an optically anisotropic phase as measured by a polarizing microscope, and has a softening point of 2.
Preferably, the temperature is 30 to 320°C.

i) Method for producing optically anisotropic pitch The optically anisotropic pitch preferably used in the present invention may be produced using any production method, but heavy carbonization, which is a common raw material for pitch production, Hydrogen oil, tar, commercially available pitch, etc. are stirred in a reaction tank at a temperature of 380°C to 500°C, and sufficiently pyrolyzed and polycondensed while degassing with an inert gas to form an optically anisotropic phase of the residual pitch ( Conventional methods for increasing AP (hereinafter abbreviated as AP) can be used. However, if a product with AP of 80% or more is produced by this method, the thermal decomposition polycondensation reaction may proceed too much, and the quinolinated content may increase to 70% by weight or more and the softening point may reach 330°C or more. Further, since the optically isotropic phase (hereinafter abbreviated as IP) is also difficult to form a microspherical dispersed state, this method is not necessarily preferred.

Therefore, a preferred method for producing the optically anisotropic pitch used in the present invention is to abort the pyrolysis polycondensation reaction in the middle,
The polycondensate is held at a temperature in the range of 350°C to 400°C and left to stand still, and AP with a high density is deposited in the lower layer while growing and ripening. This is a method of separating and extracting the waste. Details of this method are described in JP-A-57-119984.

A more preferable method for producing the optically anisotropic pitch used in the present invention is to use a carbonaceous material that contains an appropriate amount of AP and is not yet excessively heavy, as described in JP-A-58-180585. In this method, the pitch is centrifuged in a molten state to rapidly sediment the AP portion. According to this method, the AP phase accumulates in the lower WJ (R in the direction of centrifugal force) while coalescing, forming a continuous layer with approximately 80% or more of AP, and a small amount of IP in the crystalline or microscopic layer. The pitch in which the pitch is dispersed in the form of spherical bodies is the lower layer, while the upper layer is the pitch in which the majority of the IP is IP, and the AP is dispersed therein in the form of minute spheres. In this case, the boundary between both layers is clear, and only the lower layer can be separated from the upper layer and taken out.
Optically anisotropic pitch that has a large AP content and is easy to spin can be easily produced. According to this method, AP
Carbonaceous pitch having a content of 95% or more and a softening point of 230°C to 320°C can be obtained economically in a short time. Such optically anisotropic carbonaceous pitch has excellent melt spinning processing properties, and due to its homogeneity and high orientation, the tensile strength and elastic modulus of carbon fibers and graphite fibers obtained by spinning it are excellent. will be extremely excellent.

(2) Production of fibers i) Spinning The above-mentioned pitch having a high AP content and a low softening point can be spun by a known method. Such a method is applicable to 1, for example, diameters of 0.1 mm to 0,5+a
Pitch is placed in a metal spinning container with a spinneret of 1 to 1,000 mm at the bottom, and the pitch is maintained at a constant temperature between 280 and 370°C in an inert gas atmosphere until it is in a molten state. The pressure of the inert gas is kept at several hundred −
mHH and extrude the molten pitch from the mouthpiece,
The pitch fibers that flow down are wound onto a bobbin that rotates at high speed while controlling the temperature and atmosphere.

Alternatively, it is also possible to adopt a method in which pitch fibers spun from a spinneret are collected in a can-like manner in a lower collecting case while being collected by an air current. In this case, continuous spinning is possible by supplying pitch to the spinning container under pressure using pre-melted pitch or a gear pump or the like. Furthermore, in the above method, in the vicinity of the cap.

It is also possible to use a method in which pitch fibers are drawn and taken up using a gas that is controlled at a constant temperature and descends at high speed to produce long fibers on a belt conveyor below.

Furthermore, a cylindrical spinning vessel having a spinneret on the peripheral wall is rotated at high speed, molten pitch is continuously supplied to the spinning vessel, the pitch is pushed out from the peripheral wall of the cylindrical spinner by centrifugal force, and the spinning vessel is drawn by the action of rotation. It is also possible to adopt a spinning method that accumulates pitch fibers.

In the present invention, the melt-spun pitch fibers are guided to an oiling roller while converging through an air sucker,
Add a focusing agent (oil) to further focus.

it) Sizing agent (oil agent) In the present invention, as described above, an aqueous dispersion of alkylphenylpolysiloxane, which does not contain a surfactant and has a viscosity of 10 to 1000 cst at 25° C., is used as the sizing agent. In this case, the alkylphenylpolysiloxane preferably contains 1 to 80 moles of phenyl group, particularly preferably 5 to 50 moles, and examples of the alkyl group include methyl group, ethyl group, propyl group. The alkyl group is preferable, and the same molecule may contain two or more types of alkyl groups.

Since this alkylphenylpolysiloxane has a certain degree of self-emulsifying property, it is possible to prepare an aqueous dispersion with a low concentration. Dispersions are preferably used. If the concentration is less than 0.01% by weight, the pitch fiber bundles will not have sufficient cohesiveness after water evaporation, which is undesirable.On the other hand, if it exceeds 1.0% by weight, the water dispersibility of the alkylphenylpolysiloxane will be impaired. This is not desirable because it can cause

In the aqueous dispersion, alkylphenylpolysiloxane is usually dispersed in water with a particle size of about 1 to 5 ρ.

The aqueous dispersion of alkylphenylpolysiloxane is prepared using a high-speed emulsifying dispersion machine (e.g., TK Auto Homo Mixer N type, manufactured by Tokushu Kika Kogyo ■), an ultrasonic homogenizer (e.g., RUS-300 type, manufactured by Nippon Seiki Seisakusho), It can be easily produced by emulsifying for 2 minutes to 1 hour, preferably 5 to 30 minutes, using an ultrasonic cleaner (eg, Sono Cleaner 200a, manufactured by Kaiyo Denki) or a colloid mill. When emulsifying with ultrasonic waves, a frequency of 15 to 100 K)lZ is used.

By using an aqueous dispersion of the alkylphenylpolysiloxane as a sizing agent without containing a surfactant, the decomposition and deterioration of the compound during the infusibility treatment are significantly reduced, and the sizing of the fiber bundle is also good. stalemate is greatly suppressed. In addition, dimethyl polysiloxane (dimethyl silicone oil)
Not only is it difficult to prepare an aqueous dispersion, but even when used in an aqueous dispersion system, the thermal oxidation stability of dimethylpolysiloxane itself is inferior to that when an aqueous dispersion of alkylphenylpolysiloxane is used. Therefore, decomposition and deterioration of the oil agent occur during the infusibility treatment, resulting in fusion and sticking of the fiber bundles, and therefore, it cannot be used in the present invention.

Further, in the present invention, in order to further improve the heat resistance of the alkylphenylpolysiloxane, it is possible to use a compound in which an antioxidant such as amines, organic selenium compounds, and phenols is added to the alkylphenylpolysiloxane. In this case, as the antioxidant, phenyl-α-naphthylamine, dilaurylselenide, phenothiazine, iron octolate, etc. are used.

As a method of applying a sizing agent to pitch fibers.

Conventionally known application methods such as a method of applying through a U-shaped guide, an oiling roller method, and a spray method can be employed.

Although the sizing agent can be applied at any time between the spinning process and the infusibility process, it is preferable to apply the sizing agent between the spinneret and the winder in order to stably handle the fragile pitch fibers.

The adhesion fi of the sizing agent to the fibers (after water evaporation) is o, oo
s to 1.0% by weight, preferably 0.01 to 0.5
Weight%.

(2) Infusibility of pitch fibers The pitch fibers to which the above-mentioned sizing agent has been applied and are bundled are infusible by a known method.

In the present invention, the carbonaceous pitch has a softening point of 230~
When using optically isotropic carbonaceous pitch at 320°C,
1 because it has a lower softening point than known optically anisotropic carbon pitches.
It is necessary to perform the oxidation reaction starting at a lower temperature than usual to prevent the pitch fibers from fusing. The temperature of the infusibility step is 150°C to 400°C, preferably 200°C to 350°C.
The temperature is increased stepwise or gradually in the range of 10°C, usually 10°C.
Process for minutes to 5 hours. The treatment time may be as long as 1 to 3 days so that the infusibility reaction proceeds sufficiently and uniformly.

The infusibility can be achieved using air, oxygen, a mixed gas of air and oxygen or nitrogen, or the like.

In the present invention, halogen and N
o, the treatment is carried out for a short time in an atmosphere containing an oxidizing agent such as ozone, or in an oxygen gas atmosphere at a temperature 30 to 50 degrees Celsius lower than the softening point of the pitch, i.e., at a temperature of 150 to 240 degrees Celsius. It is preferable to maintain the temperature for 5 minutes to 1 hour until melting is achieved, and then raise the temperature to about 300° C. if necessary to complete the infusibility. The latter method is particularly preferred because it is easy and reliable.

2) Heat treatment process Next, this infusible carbonaceous pitch fiber is heated in an atmosphere of chemically inert argon gas or nitrogen gas, etc.
After preliminary carbonization by raising the temperature to 500-1000℃,
Carbon fibers are obtained by carbonization by raising the temperature to a temperature in the range of 0 to 2000°C, and the graphitization process is accelerated by raising the temperature to a temperature in the range of 2000 to 3000°C.

Graphite fibers are obtained.

In the present invention, the details of the carbonization and graphitization methods are not particularly limited, and generally known methods can be used.

Also, during infusibility, carbonization, and graphitization treatments, it prevents scratches from rubbing against the furnace walls and furnace bottom, avoids shrinkage and deformation of the yarn, or produces carbon fibers and graphite fibers with good appearance and high physical properties. For these purposes, when processing a fiber bundle coated with a sizing agent, it is preferable to apply a load or tension to the fiber bundle.

〔Effect of the invention〕

The method for producing pitch-based carbon fiber and graphite fiber of the present invention includes:
10-1.0OOcst at 25°C without surfactant
Since the sizing agent is made of an aqueous dispersion of alkylphenylpolysiloxane with a viscosity of The yarn handling properties of fragile pitch fiber bundles are good, and even when pre-carbonization, carbonization, and graphitization treatments are performed, sticking is suppressed, and high-quality, high-strength fibers can be obtained after firing. You can get the product. In particular, when optically anisotropic carbonaceous pitch is used as the carbonaceous pitch, it is possible to produce long-fiber carbon fibers and graphite fibers with extremely high strength, high elastic modulus, good properties, and good appearance. I can do it.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A carbonaceous pitch containing approximately 55% optically anisotropic phase and having a softening point of 235° C. was used as a precursor pitch. This precursor pitch was separated using a cylindrical centrifugal separator at 370° C. to obtain a pitch with high optical anisotropy.

The optically anisotropic pitch obtained is 98 times the optically anisotropic phase.
%, and the softening point was 265°C.

The obtained optically anisotropic pitch was passed through a spinning machine having a spinneret with 500 holes, and extruded and spun at 355° C. under a nitrogen gas pressure of 200 nmHg.

The spun pitch fibers are wound onto a bobbin that rotates at high speed provided at the bottom of the nozzle, and the fibers are wound at a winding speed of about 500 m/min for 10 minutes.
Spun for minutes. At this time, the spun yarn was substantially converged by an air sucker and guided to an oiling roller, and a convergence oil was applied thereto.

As the oil agent, an aqueous dispersion of methylphenylpolysiloxane (phenyl group content: 25 mol %) having a viscosity of 40 cst at 25° C. was applied. An aqueous dispersion of methylphenylpolysiloxane was prepared by combining methylphenylpolysiloxane and water using a high-speed emulsifying and dispersing machine (Tokushu Kika Kogyo AI, TK Autohomogen Mixer H type).

It was prepared by stirring and dispersing at 7500 rpm+m for 10 minutes.

The degree of methylphenylpolysiloxane in the water-dispersed oil agent was 0.1% by weight, and the amount attached to the yarn was 0.05% by weight. There was no difficulty in focusing and winding due to the generation of static electricity during spinning, and the focusing and winding was good.

A part of the pitch fiber bundle thus obtained was taken out and infusible while being heated in air from 150°C to 330°C over 60 minutes. During infusibility, there was no breakage of the fiber bundle and no fluffing was observed. The fiber bundle after infusibility was flexible and easy to handle. When the degree of adhesion of the infusible thread was measured, it was 0%.

This infusible pitch fiber was heated for 15 minutes in an inert gas atmosphere.
The temperature was raised to 00°C to obtain carbon fibers. This fiber had a thread diameter of 10.0 μm, a tensile strength of 3.0 GPa, a tensile modulus of 270 GPa, and a degree of adhesion of 9%.

In addition, this carbon fiber was heated to 2500°C in an inert gas atmosphere.
The graphite fiber obtained by raising the temperature to 100% had a thread diameter of 9.8 μm, a Q tensile strength of 3.5 GPa, a tensile modulus of 700 GPa, and a degree of adhesion of 21%.

In addition, the degree of adhesion (%) is determined by cutting the fiber bundle into 3 mm pieces,
This was determined using the following formula by immersing this in ethanol, blowing air into it for 30 seconds, and then counting the total number of stuck filaments (N) under a microscope at 20x magnification. .

Adhesion degree = (N/X)X100 (%) However, X indicates the total number of filaments counted, and N indicates the total number of stuck filaments.

Comparative Example 1 As an oil agent, a polyoxyalkyl ether with a number average molecular weight of 290 to which 2 moles of oxyethylene was added (final boiling point 4
85℃...atmospheric pressure) as an emulsifier, at 25℃
The same treatment as in Example 1 was carried out, except that a water emulsion-based oil agent in which methylphenylpolysiloxane (phenyl group content: 25%) having a viscosity of 0 cst was emulsified was applied.

The above number average molecular weight was calculated using gel permeation chromatography LCO8 (manufactured by Nippon Analytical Industry Co., Ltd.).
(2) This is the value obtained by measuring with a column and converting it to a standard polystyrene molecular weight.

The concentration of the water emuldimine oil agent is 0.1% by weight,
The amount of adhesion was 0.05% by weight based on the yarn.

Good focusing and winding during spinning was achieved.

A part of the pitch fiber bundle obtained in this way was taken out,
Infusibility was carried out while raising the temperature from 150° C. to 330° C. in 60 minutes in air. During infusibility, there was no breakage of the fiber bundle and no fluffing was observed. The fiber bundle after infusibility was flexible and easy to handle. The sticky dust of the infusible thread is 5%
Met.

This infusible pitch fiber was heated in an inert gas atmosphere for 1
The temperature was raised to 500°C to obtain carbon fibers. The diameter of the fiber is 1
0.07a, tensile strength is 2.7GPa, tensile modulus is 2
The pressure was 70 GPa, and the amount of stuck dust was 41%.

In addition, graphite fiber obtained by heating this carbon fiber to 2500°C in an inert gas atmosphere has a thread diameter of 9.8 μm, a tensile strength of 3.0 GPa, a tensile modulus of 710 GPa, and an adhesive dust of 55. %Met.

Comparative Example 2 Number average molecular weight 6 with an average of 10 moles of oxyethylene added
The process was carried out in the same manner as in Example 1, except that a water emulsion-based oil emulsified with methylphenyl polysiloxane having a viscosity of 40 cst at 25° C. was applied using a nonionic surfactant consisting of polyoxyethylene alkyl ether of 50 as an emulsifier. .

In this case, because the surfactant has a high molecular weight, 50% is distilled off at a boiling point of 600°C (atmospheric pressure), but the remaining components decompose and cannot be distilled out in the air. During the infusibility treatment, the fiber bundles were significantly stuck, and the fiber bundles were cut during the infusibility treatment. The adhesive dust of the infusible thread was 90%, and it was partially fused.

Comparative Example 3 When an attempt was made to obtain an aqueous dispersion of dimethylpolysiloxane having a viscosity of 40 cst at 25° C. in the same manner as in Example 1, water dispersion was not successful. When the mixture was applied as an oil agent and treated in the same manner as in Example 1, adhesion and fusion occurred during infusibility, and the fiber bundles were cut.

Comparative Example 4 The methylphenylpolysiloxane used in Example 1 was
It was treated in the same manner as in Example 1, except that it was diluted with dimethylpolysiloxane of 0.5cst (boiling point 100°C) at 25°C and an oil agent was applied during spinning. The concentration of oil is 0.1
% by weight.

In this case, a large amount of static electricity was generated during spinning, and the yarn became loose, making it impossible to collect and wind the yarn.

Claims (4)

[Claims] (1) In a method for producing carbon fibers and graphite fibers, in which a sizing agent is added to melt-spun carbonaceous pitch fibers and subjected to infusibility, carbonization, and graphitization treatment, the sizing agent is added to
A method for producing carbon fibers and graphite fibers, which comprises using an aqueous dispersion of alkylphenylpolysiloxane having a viscosity of 0.000 cst. (2) The method for producing carbon fibers and graphite fibers according to claim (1), wherein the alkylphenylpolysiloxane contains 1 to 80 mol% of phenyl groups. (3) The alkylphenylpolysiloxane has, as the alkyl group, any one of a methyl group, an ethyl group, a propyl group, or two or more groups that are the same or different selected from these groups. (1) The method for producing carbon fibers and graphite fibers. (4) Claim (1) wherein the sizing agent contains an antioxidant in the alkylphenylpolysiloxane.
) The method for producing carbon fibers and graphite fibers described in .