JPH01111020A - Production of pitch-based carbon yarn - Google Patents

Abstract

PURPOSE:To facilitate stable handling of infusible pitch yanr, to eliminate end breakage of the yarn in a preliminarily carbonizing process and to obtain the title yarn having excellent quality, strength and elongation, by providing infusi ble pitch yarn with a compound finishing oil. CONSTITUTION:First, carbonaceous pitch yarn obtained by melt spinning is infusibilized and the prepared infusibilized yarn is provided with a finishing oil consisting of an alkylphenylpolysiloxane and/or dimethylpolysiloxane having 1,000-10,000cst at 25 deg.C. Then the infusibilized yarn provided with the finishing oil is preliminarily carbonized, carbonized and graphitized. A finishing oil containing an antioxidant such as phenol is preferable as the finishing oil. The infusibilization is preferably carried out by a method where the pitch yarn is maintained in an oxygen gas atmosphere at a temperature 30-50 deg.C lower than the softening point of the pitch for 10min-1hr and optionally heated to 300 deg.C to complete the infusibilization.

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 pitch-based carbon fibers by spinning carbonaceous pitch, making it infusible, carbonizing it, and graphitizing it to obtain long filament carbon fibers.

(Prior art) 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 in a wide range of technical fields related to automobiles, aircraft, and various other industrial fields. Carbon fiber or molded carbon materials are attracting attention. In particular, the method for producing carbon fiber from carbonaceous pitch is
It is regarded as an important method for producing carbon fiber with low cost and high performance.

However, depending on the conventional technology, pitch fibers have a small tensile strength of approximately 0.0 IGPa and are extremely brittle, so fiber bundles are cut during the infusibility process, carbonization process, etc., causing fuzz, roller wrapping, etc. It was extremely difficult to handle, making it extremely difficult to obtain the long filament fibers necessary to obtain high-performance products.

As a means of solving these problems, various sizing agents (oil agents) are used.
is proposed.

Special Publication No. 51-12379, Japanese Patent Publication No. 54-131032
No. 1, No. 2003-11-1193 discloses a method of using a silicone-based oil 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 breakage of the fiber bundles and generation of fuzz. , wrapping around the guide roller, etc., and the desired effect cannot be obtained.

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.) has been proposed. Although this method improves the cohesiveness of fibers during spinning, when exposed to high temperatures of 150-400°C during the infusibility process, the surfactant decomposes, deteriorates, or turns into tar, resulting in severe agglutination, causing the fibers to become tattered. There are disadvantages such as the possibility of breaking the bundle.

Furthermore, 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 (
JP-A No. 59-223315), dimethylpolysiloxane with a viscosity of 0.5 to 500 cst at 25°C (
Dimethyl silicone oil)
No. 8124) is disclosed. However, since these methods consist of solvents or low viscosity silicone oils.

The disadvantage is that the thread is easily damaged by solvent dissolution, etc.
In addition, during the infusibility process, the fibers tend to fuse and stick together, and they tend 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
(No. 2) has also been proposed, but this method
Due to the decomposition and deterioration of the oil agent that binds the fiber bundles, the fibers become significantly stuck, the bundle is disturbed, and the flexibility of the fibers is lost. This has the disadvantage that the fibers become tattered and the fiber bundles are cut, 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.
We proposed a sizing agent in which a water emulsion-based oil was prepared by using distillate below ℃ (atmospheric pressure equivalent boiling point) as an emulsifier and emulsifying alkylphenylpolysiloxane having a viscosity of 10-1000 cst at 25℃ (Japanese Patent Laid-Open No. 62 -133122
Publication No.).

This sizing agent is excellent in the working environment and has little deterioration of the oil, so it facilitates the handling of fragile carbon fibers during the sizing process during spinning, infusibility, pre-carbonization, carbonization and graphitization processes, and allows for easy handling of the fragile carbon fibers during the sizing process during spinning, as well as the infusibility, pre-carbonization, carbonization and graphitization processes. It has the advantage of suppressing fusion and adhesion.

However, according to subsequent research by the present inventors, although such a sizing agent has the function of preventing fusion and coalescence between filaments during the infusibility process, the oil agent decomposes during preliminary carbonization, resulting in a low viscosity. It has been found that there is a problem in that the convergence of the fiber bundle is reduced due to the carbon fibers being oxidized, and yarn breakage occurs in the furnace, making it difficult to produce high-quality and high-strength carbon fibers.

〔the purpose〕

The present invention enables stable handling of infusible fibers obtained from the infusible process, prevents fusion and coalescence of the infusible fibers that occur during the carbonization process, especially the pre-carbonization process, and eliminates yarn breakage in the furnace. An object of the present invention is to provide a method for producing pitch-based carbon fibers having excellent fiber quality, strength, and elongation after firing.

〔composition〕

According to the present invention, in a method for producing carbon fibers by infusibleizing melt-spun carbonaceous pitch fibers and then carbonizing or further graphitizing them, the infusible fibers obtained by the infusible treatment have a viscosity at 25°C. 1000~10,
A method for producing pitch-based carbon fiber is provided, which comprises applying an oil agent consisting of alkylphenylpolysiloxane or/and dimethylpolysiloxane of 0.000 cst, and carbonizing or further graphitizing the fiber.

The present inventors, in the manufacturing process of pitch-based carbon fiber,
It is possible to stably handle the infusible fibers obtained from the infusible process, prevent fusion and agglutination between the infusible fibers that occur during the carbonization process, especially the pre-carbonization process, and eliminate yarn breakage in the furnace, and furthermore, the firing process As a result of intensive studies on the production method of pitch-based carbon fibers having excellent strength and elongation, it was found that when an oil agent made of alkylphenyl polysiloxane having the above-mentioned specific viscosity is applied to the infusible fibers, the above-mentioned purpose can be achieved. The inventors have found that this can be achieved and have completed the present invention.

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, but includes coal tar pitch obtained by dry distilling one coal,
Coal-based pitch such as coal liquefied products, naphtha cracking tar pitch, catalytic cracking tar pitch, petroleum-based pitch such as atmospheric distillation residue, vacuum distillation residue, etc.

Various pitches such as synthetic pitches obtained by decomposing synthetic resins, pitches hydrogenated with hydrogen or hydrogen donors, and modified by heat treatment, solvent extraction, etc. can also be used. These carbonaceous pitches may be isotropic pitches or optically anisotropic pitches, and can also be applied to pitches called neomesoface and brimesoface, but in particular, the optical pitches described below are applicable. Anisotropic pitch is 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 thoroughly 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 manufactured using this method,
In some cases, the thermal decomposition polycondensation reaction progresses too much, and the quinoline dissolved content increases to 70% by weight or more, and the softening point reaches 330°C or higher, and the optically isotropic phase (hereinafter abbreviated as IP) also becomes microspherical. This is not necessarily a preferable method because it is difficult to achieve a dispersed state.

Therefore, a preferred method for producing the optically anisotropic pitch used in the present invention is to terminate the pyrolysis polycondensation reaction halfway and maintain the polycondensate at a temperature in the range of 350°C to 400°C to substantially This is a method in which AP is allowed to stand still and deposited in the lower layer while growing and ripening, and this is separated and taken out from the upper layer where there is a large amount of low-density IP. 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 layer (layer in the direction of centrifugal force) while coalescing, forming a continuous layer with about 80% or more of AP, and a small amount of IP in the crystalline or minute layer. The lower layer is a pitch that is dispersed in spherical bodies, while the upper layer is a pitch that is mostly IP and AP is dispersed therein in minute lines. In this case, the boundary between both layers is clear.

Only the lower layer can be separated and taken out from the upper layer, and optically anisotropic pitch that has a large AP content and is easy to spin can be easily produced. According to this method, carbonaceous pitch having an AP 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. In such a method, for example, pitch is placed in a metal spinning container having one or more spinnerets each having a diameter of 0.1 m to 0.5 mm below, and the pitch is heated in an inert gas atmosphere. The pitch is maintained at a constant temperature between 280-370℃, kept in a molten state, and the pressure of inert gas is applied for several hundred ms.
Increase the temperature to +Hg and push out the molten pitch from the nozzle,
The pitch fibers that flow down are wound onto a bobbin that rotates at high speed while controlling the temperature and atmosphere.

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, it is also possible to use a method in which the pitch fibers are drawn and drawn using gas that is controlled at a constant temperature and descends at high speed in the vicinity of the die, and long fibers are produced on the 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:

It is desirable that the particles be focused through an air sucker, guided to an oiling roller, and further focused with a focusing agent applied thereto. As the sizing agent, any conventionally known sizing agent can be used, and for example, the following compounds may be used.

[Specific examples of sizing agents]

Examples of the sizing agent include water, alcohols such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, and butyl alcohol, or dimethylpolysiloxane and alkylphenylpolysiloxane with a viscosity of 3 to 300 cst (25'C). Diluted with a solvent such as low boiling point silicone oil (polysiloxane) or fin oil; or dispersed in water with an emulsifier added; similarly dispersed with graphite, polyethylene glycol, or hindered esters: Interface The activator was diluted with water; other oils that do not harm the pitch fibers among the various oils used for conventional fibers, such as polyester fibers, can be used.

The method of applying these sizing agents to pitch fibers is as follows:
Conventionally known application methods such as 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 preferably applied between the spinneret and the winder in order to stably handle the fragile pitch fibers.

The amount of the sizing agent attached to the fibers is 0.01 to 10% by weight, preferably 0.05-5% by weight.

Furthermore, in the present invention, since infusibility is subsequently performed, a heat-resistant oil agent is preferably applied.

As a heat-resistant oil agent, alkylphenylpolysiloxane with a boiling point of 10 to 1000 cst or a boiling point of 60
Emulsified with a nonionic surfactant at 0°C or lower is used.

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

In the present invention, when optically isotropic carbonaceous pitch is used as the carbonaceous pitch, the softening point is lower than that of known optically anisotropic carbonaceous pitch, so the oxidation reaction starts at a lower temperature than usual and the pitch is It is necessary to prevent fiber fusion. The temperature of the infusibility step is 150 DEG C. to 400 DEG C., preferably 200 DEG C. to 300 DEG C., and the temperature is increased stepwise or gradually for usually 30 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.

Infusibility can be performed using air, oxygen, a mixed gas of air and oxygen or nitrogen, or the like.

In the present invention, halogen and N
Sufficient infusibility can be achieved by treatment for a single hour in an atmosphere containing an oxidizing agent such as O8 or ozone, or at a temperature 30 to 50 degrees Celsius lower than the softening point of pitch, i.e., 150 to 240 degrees Celsius, in an oxygen gas atmosphere. It is preferable to maintain the temperature for 10 minutes to 1 hour until the temperature is obtained, and then raise the temperature to about 300° C. if necessary to complete the infusibility, and the latter method is particularly preferred because it is easy and reliable.

(2) Treatment of infusible fibers with oil agent Next, in the present invention, an oil agent is applied to the carbonaceous pitch fibers that have become infusible.

As mentioned above, the oil has a viscosity of 1000 at 25°C.
-10.000cst, preferably 2000-5000
Alkylphenylpolysiloxane and/or dimethylpolysiloxane within the range of cst are essential components.

The viscosity at 25° C. is 1000 cst.

In the subsequent pre-carbonization process, the oil agent decomposes and deteriorates, which tends to cause yarn breakage in the furnace.On the other hand, if the viscosity at 25°C exceeds 10.000 cst, the viscosity of the infusible fiber increases, causing stickiness. Handling performance deteriorates,
Further, it is not preferable because the resulting carbon fibers will stick together.

In addition, the alkylphenylpolysiloxane used as an oil agent contains 5 to 80 moles of phenyl group as a component.
It is preferable that the alkyl group contains 10 to 50 moles, but 0 is preferable, and the alkyl group is preferably a methyl group, an ethyl group, or a propyl group. Also, as alkylphenylpolysiloxane or dimethylpolysiloxane, any one having the above-mentioned viscosity can be used, but in the present invention, in particular, amines, organic selenium compounds, and phenols are used in the compound. It is preferable to use one to which an antioxidant such as the like is added.

In this case, as the antioxidant, phenyl-α-naphthylamine, dilauryl selenide, phenothiazine, iron octolate, etc. can be used.

The oil agent of the present invention has alkylphenylsiloxane and/or dimethylsiloxane having the above-mentioned specific viscosity as an essential component, but water and a solid lubricant may be added as necessary.

As the solid lubricant, either an inorganic type or an organic type can be used.

Inorganic solid lubricants include graphite (C), molybdenum disulfide (MoS, ), and tungsten disulfide (WS, ).
.

Boron nitride (BN), graphite fluoride (CF), -lead oxide (PbO(n)), molybdenum dioxide (Mob, ),
Cobalt oxide (Go, 03), zinc oxide (ZnO)
, tin oxide (SnO)-suboxide steel (Cu, O), cadmium oxide (CdO), tungsten oxide (WO2), calcium fluoride (CaFz), barium fluoride (Ba
F2), lithium fluoride (LiF), sodium fluoride (NaF), silicon nitride (SiJ14), molybdenum telluride (MoTea), tungsten selenide (VS
ez), tungsten telluride (MTas)-niobium disulfide (NbS, ), β-niobium selenide (NbSa,
β), niobium telluride CNbTe5), β-tantalum sulfide (TaS, β), α-tantalum selenide (TaSa,
), tantalum telluride (TaTa*), titanium disulfide (TiS), titanium selenide (TiSez), titanium telluride (TiTez), zirconium disulfide (
ZrSe ), zirconium selenide (ZrSe, )
, zirconium telluride (ZrTez), bismuth iodide (BiIa), lithium hydroxide (LiOH), nickel iodide (NiIi), cadmium chloride (CdC)
1,), cadmium iodide (CdI2), cadmium bromide (CdBrz), tin sulfide (SnS, ), iron pyrophosphate, zinc pyrophosphate, calcium pyrophosphate, tin pyrophosphate, etc. Especially graphite (C), molybdenum nitride (MoS, ), tungsten disulfide (US,
) is preferred.

Examples of organic solid lubricants include adducts of melamine and cyanuric acid.

It is preferable to use these solid lubricants having an average particle size of 30 μm or less and a uniform particle size, and they may be used alone or as a mixture of two or more types.

These two oils are emulsified with a nonionic surfactant having a boiling point of 600° C. or lower (calculated at atmospheric pressure) and applied as an emulsion. In this case, there is almost no solubility in the infusible fiber,
Further, it is desirable to use an inexpensive solvent with a boiling point of 200° C. or lower, which is less likely to damage these fibers and has excellent handling properties, as the diluent.

Examples of such solvents include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane, and degan, unsaturated aliphatic alcohols, and saturated aliphatic alcohols such as propyl alcohol, isopropyl alcohol, and butyl alcohol.

Furthermore, as the surfactant, any surfactant can be used as long as it does not deteriorate the heat resistance of the base during the infusibility process, but in the present invention, nonionic surfactants with a boiling point of 600°C or less are particularly preferred. used for.

Specific examples of such nonionic surfactants include polyoxyalkylene alkyl ether, polyoxyalkylene alkyl ester, polyoxyalkylene alkyl phenyl ester, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxy Examples include propylene alkyl ether, polyoxyethylene polyoxypropylene alkylphenyl ester, etc., but preferably polyoxyethylene alkyl ether with an average added mole number of oxyethylene of less than 6 (for example, polyoxyethylene lauryl, which is an adduct of 2 moles of oxyethylene). ether), polyoxyethylene alkyl ester, and polyoxyethylene alkylphenyl ether.

Furthermore, silicone surfactants such as polyoxy-modified silicone surfactants and polyoquinoethylene-modified silicone surfactants can also be used.

Furthermore, in the present invention, a distillate having a boiling point of 600° C. or lower (in terms of atmospheric pressure) obtained by distilling the nonionic surfactant under reduced pressure can also be used.

In the present invention, siloxane having the specific viscosity,
Furthermore, if necessary, an oil agent with auxiliary components added thereto is applied to the infusible pitch fibers, but the order of application is not restricted, and each may be applied sequentially, or it may be applied individually. A treatment liquid may be applied at the same time.

As a method for applying these oils to the pitch fibers, conventionally known application methods such as an oiling roller method and a spray method can be employed.

The amount of the oil agent attached to the infusible fibers is 0.01 to 10% by weight2, preferably 0.05 to 5% by weight.

K) After the heat treatment process, the infusible carbonaceous pitch fibers to which an oil agent has been applied are
Preliminary carbonization is carried out by raising the temperature to 300 to 1000°C in a chemically inert atmosphere such as argon gas or nitrogen gas,
Furthermore, carbon fibers can be obtained by raising the temperature to a temperature in the range of 1000 to 2000°C and carbonizing it. 2000 again
By increasing the temperature to a temperature in the range of ~3000°C, a graphitization process is carried out to obtain graphite fibers.

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, pre-carbonization, carbonization, and graphitization treatments.

When processing fiber bundles with a sizing agent applied to prevent scratches from rubbing against the furnace walls and bottom, to avoid shrinkage and deformation of the yarn, or to obtain carbon fibers and graphite fibers with good appearance and high physical properties. It is preferable to apply a load or tension to the fiber bundle.

(Effects of the Invention) The method for producing pitch-based carbon fibers of the present invention provides the following steps: In the production process of pitch-based carbon fibers, infusible fibers can be handled stably, and in-fusible fibers can be suppressed from breaking in the furnace during the carbonization process, especially in the pre-carbonization process, and fusion and coalescence can be prevented. In addition, it is possible to obtain a method for producing pitch-based carbon fibers having excellent fiber quality, strength, and elongation after firing treatment.

In particular, when optically anisotropic carbonaceous pitch is used as the carbonaceous pitch, continuous filament carbon fibers and graphite fibers with extremely high strength, high elastic modulus, good properties, and good appearance can be produced. Can be done.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The present invention is not limited thereby.

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 containing a large amount of optically anisotropic phase. The obtained optically anisotropic pitch contained 9 g% of an optically anisotropic phase and had a softening point of 265°C.

The obtained optically anisotropic pitch was passed through a spinning machine having a 500-hole spinneret, and extruded and spun at 355° C. under a nitrogen gas pressure of 200 w+w+Hg.

The spun pitch fibers were wound onto a bobbin rotating at high speed provided at the bottom of the nozzle, and spun for 10 minutes at a winding speed of about 500 cm/min. At this time, the spun yarn was guided to an oiling roller that was substantially focused by an air sucker, and a sizing agent was applied thereto.

As a sizing agent, dimethylphenylpolysiloxane (phenyl group content 25 mol%) having a viscosity of 40 cst at 25°C was used.
)It was used.

The amount of sizing agent applied was 0.5% by weight based on the yarn.

A portion of the pitch fiber bundle thus obtained was taken out and infusible while being heated from 150° C. to 280° C. for 2 hours in air.

The tension applied to the fiber bundle at this time is 0 per filament.
．． 007 g of the infusible pitch fiber bundle was introduced into an oiling roller and an oil agent was applied thereto.

The oil agent is methylphenylpolysiloxane (phenyl group content 25 mol%) with a viscosity of 3000 cst at 25°C.
) as a nonionic surfactant with a boiling point of 600℃ or less (
Polyoxyethylene lauryl ether having an average molecular weight of 1000 was distilled under reduced pressure and emulsified at a distillate with a boiling point of 600°C (atmospheric pressure equivalent boiling point) or lower) to form a water emulsion. The amount of oil applied was 0.5% by weight based on the infusible fibers.

Next, the infusible fibers to which the oil agent had been applied were heated to 1000° C. at a rate of 1000° C./min in an inert gas atmosphere to be pre-carbonized. The tension applied at this time was 0.0 mm per filament.
It was 0.007g. No fusion or breakage was observed in the fiber bundles discharged from the preliminary carbonization process.

Next, the pre-carbonized fibers are supplied to a carbonization process.
The temperature was raised to 500°C to obtain carbon fibers. The diameter of the fiber is
The heel was 10μ, the tensile strength was 2.90Pa, and the tensile modulus was 265GPa.

Further, graphite fiber obtained by heating this carbon fiber to 2600° C. in an inert gas atmosphere had a thread diameter of 9.8 μm, a tensile strength of 3.3 GPa, and a tensile modulus of 710 GPa.

Comparative Example 1 In the case where the same treatment as in Example 1 was carried out except that the oil used for spinning was applied to the infusible fiber at a ratio of 0.5% by weight, the yarn was occasionally broken in the furnace during the preliminary carbonization treatment. This occurred, making stable operation impossible, and the quality of the obtained carbon fibers significantly deteriorated.

Patent applicant: Toa Fuel Industries Co., Ltd.

Claims (7)

[Claims] (1) In a method of manufacturing carbon fibers by infusibleizing melt-spun carbonaceous pitch fibers and then carbonizing or graphitizing them, the infusible fibers obtained by the infusible treatment have a viscosity of 1000 to 10 at 25°C. ,000cs
1. A method for producing pitch-based carbon fibers, which comprises applying an oil agent consisting of alkylphenylpolysiloxane or/and dimethylpolysiloxane, and pre-carbonizing, carbonizing, or further graphitizing the fiber. (2) Emulsifying the oil agent with a surfactant with a boiling point of 600°C or less,
The method for producing pitch-based carbon fiber according to claim 1, wherein the pitch-based carbon fiber is applied as a water emulsion. (3) The method for producing a pitch-based carbon fiber according to claim 1, wherein the alkylphenylpolysiloxane contains 5 mol% to 80 mol% of phenyl groups. (4) A patent claim characterized in that the alkyl group of the alkylphenylpolysiloxane has a methyl group, an ethyl group, a propyl group, or two or more same or different groups selected from these groups. A method for producing a pitch-based carbon fiber according to item 1. (5) A pitch system according to claim 1, characterized in that an antioxidant such as an amine, an organic selenium compound, or a phenol is contained in the alkylphenyl polysiloxane or/and dimethyl polysiloxane. Carbon fiber manufacturing method. (6) The antioxidant is phenyl-α-naphthylamine,
5. The method for producing pitch-based carbon fiber according to claim 4, characterized in that the fiber is one selected from dilauryl selenide, phenothiazine, and iron octrate, or a mixture of two or more thereof. (7) The carbonaceous pitch is an optically anisotropic pitch containing about 95% or more of an optically anisotropic phase and having a softening point of 230 to 320°C. 1
A method for producing pitch-based carbon fiber as described in Section 1.