JPH0941226A - Precursor for carbon fiber production and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon fiber having a high tensile strength by applying an organic compound and/or a silicone compound formed as particles on the surface of a precursor fiber to suppress the adhesion among monofilaments. SOLUTION: This method for producing a carbon fiber is to form an organic compound and/or a silicone compound as particles and to apply the particles on the surface of a precursor fiber for producing the carbon fiber in order to suppress the direct contact among monofilaments. It is preferable to use the particles of a thermosetting resin or a thermoplastic resin having >=300 deg.C melting point, having <=70% carbonized residual ratio. The particles having 0.05-50μm mean particle diameter and 0.001-10wt.% attached amount to the precursor are preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precursor for producing carbon fiber capable of obtaining carbon fiber having excellent tensile strength, a method for producing the same, and a method for producing carbon fiber using the precursor.

[0002]

2. Description of the Related Art Since carbon fibers have excellent specific strength and specific elastic modulus as compared with other fibers, they are industrially widely used as reinforcing fibers for composite materials with resins by utilizing their excellent mechanical properties. It's being used. In recent years, the superiority of the carbon fiber composite material has been further increased, and particularly in sports and aerospace applications, there is a strong demand for high performance of the carbon fiber composite material. The properties of the composite material largely depend on the properties of the carbon fiber itself, and this demand is, of course, a demand for higher performance of the carbon fiber itself.

[0003] In order to produce such high-performance carbon fibers, it is necessary to suppress the generation of defects which may be the starting point of breakage. In particular, it can be seen that the breaking of the carbon fiber mostly started from the surface, and the contribution of surface defects was large. On the other hand, conventionally, there has been proposed a technique of removing surface defects by etching the surface layer by subjecting carbon fiber to various post-treatments such as vapor-phase treatment, liquid-phase treatment, and electrolytic treatment (for example, Japanese Patent Laid-Open No. 2000-242242). JP-A-58-214527 and JP-A-61-225330). However, although the strength is improved by the above technique, the operation and the process become very complicated, and it is difficult to adopt as an actual production technique,
Moreover, there is a problem that the cost increases.

The cause of the surface defect may be adhesion of foreign matter, generation of scratches by a roller or the like, adhesion between single yarns due to heat, and the like. US Pat. No. 35088
It is stated in the specification of No. 74 that carbon black is added to the precursor to suppress the adhesion between single yarns and improve the strength. However, this is the case of carbon fibers having a low strength level, and in a system having a high strength level, there is a problem that the strength is rather lowered when carbon black is applied. It is considered that the hard fine particles cause scratches on the precursor.

The inventor of the present invention provides a carbon fiber having a high strength level by providing particles made of one or more kinds selected from organic compounds and silicone compounds in order to provide a gap between the single yarns and suppress the adhesion between the single yarns. The present invention has been achieved by finding that the strength of the is further improved.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carbon fiber having a high tensile strength, which cannot be achieved by the above-mentioned prior art, and a composite material using the carbon fiber.

[0007]

The above object of the present invention is: (1) A precursor for producing carbon fiber, characterized in that the fiber surface has particles comprising at least one selected from organic compounds and silicone compounds.

(2) A precursor for producing carbon fiber, which has particles having a carbonization residual rate of 70% or less on the surface.

(3) The average particle size of the particles is 0.05 to 50.
The precursor for carbon fiber production according to (1) or (2) above, wherein the precursor is carbon.

(4) The precursor for producing carbon fiber according to any one of the above items (1) to (3), characterized in that the amount of particles attached is 0.001 to 10% by weight.

(5) The particles are polytetrafluoroethylene, tetrafluoroethylene-6-fluoropropylene copolymer, phenol resin, melamine resin, polystyrene, polyethylene,
(1) to (1), which contains any one of polyacrylonitrile, silicone rubber, and silicone resin.
The precursor for producing carbon fiber according to any one of (4).

(6) The precursor for producing carbon fiber according to any one of the above items (1) to (5), wherein the particles contain fluorine or silicon.

(7) A method for producing a precursor for producing carbon fiber, characterized in that particles comprising one or more kinds selected from organic compounds and silicone compounds are provided on the fiber surface.

(8) A method for producing a precursor for producing carbon fiber, characterized in that particles having a carbonization residual rate of 70% or less are provided on the fiber surface.

(9) A method for producing a carbon fiber, which comprises firing a precursor for producing a carbon fiber having particles of one or more kinds selected from organic compounds and silicone compounds on the fiber surface.

(10) A method for producing a carbon fiber, which comprises firing a precursor for producing a carbon fiber having particles having a carbonization residual rate of 70% or less on the fiber surface.

It can be solved by

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below.

The precursor for producing carbon fiber of the present invention is
Since the particles have particles on the surface, they enter between the single yarns and direct contact between the single yarns is suppressed, so that high-strength carbon fibers can be obtained.

However, inorganic particles such as silica, alumina, and metals are generally hard and easily damage the precursor, and the metal forms carbides to form defects.

The particles according to the present invention comprise at least one selected from organic compounds and silicone compounds.

Specific examples of the organic compound and the silicone compound include polytetrafluoroethylene, tetrafluoroethylene-6-fluoropropylene copolymer, phenol resin, melamine resin, polystyrene, polyethylene, polyacrylonitrile, silicone rubber and silicone. Examples thereof include resins.

The particles in the present invention are preferably a thermosetting resin or a thermoplastic resin having a melting temperature of 300 ° C. or higher because it is preferable to keep the particle shape at the flameproofing temperature from the viewpoint of suppressing the adhesion between single yarns. . Specific examples thereof include polytetrafluoroethylene, tetrafluoroethylene-6-propylene propylene copolymer, phenol resin, melamine resin, crosslinked polystyrene, crosslinked polyethylene, polyacrylonitrile, silicone rubber, and silicone resin. . Among them, particles containing fluorine such as polytetrafluoroethylene and tetrafluoroethylene-6-fluoropropylene copolymer have a low coefficient of friction and are unlikely to cause scratches on the precursor. large. Therefore, the particles in the invention preferably contain fluorine. The content is preferably 1% by weight or more, more preferably 10% by weight or more, still more preferably 50% by weight or more.

Particles containing silicon such as silicone rubber and silicone resin have a large improvement in strength, probably because the particles have high heat resistance. Therefore, the particles in the present invention preferably contain silicon. The content is preferably 1% by weight or more, more preferably 10% by weight or more, further preferably 35% by weight or more.

Furthermore, if the carbonization residual ratio of the particles is too high, the yarn slips on the roller during firing to generate fluff, or the draw ratio cannot be increased, so that the carbon fiber having high physical properties is obtained. May be difficult to obtain. Therefore, the carbonization residual rate of the particles in the present invention is preferably 70% or less, more preferably 50% or less, and further preferably 30% or less.

The carbonization residual rate is measured as follows.

Rigaku TAS-300 high temperature differential TG
-Using DTA, once evacuated and recompressed with nitrogen,
Under a nitrogen stream of 30 ml / min, the carbonization loss is measured up to 800 ° C. at a heating rate of 500 ° C./min. At this time, the carbonization residual rate is defined as follows from the ratio of the sample weight W1 at room temperature and the sample weight W2 at 700 ° C.

Carbonization residual rate (%) = (W2 / W1) × 100 Further, the particles in the present invention have such a softness that the precursor is not scratched, and are deformed by the tension during the process or the like. It is preferable to have appropriate hardness so that the effect of suppressing the adhesion between yarns is not reduced.

Further, the particles in the present invention, if containing a metal, may react with the precursor during carbonization to form a carbide, which may lower the strength, and therefore it is preferable that the particles do not contain a metal. 1000 as the total metal content
ppm or less is preferable, 100 ppm or less is more preferable, 10 ppm or less is further preferable, and ideally no content is preferable.

If the amount of the particles adhered in the present invention is too small, the effect will be poor, and if it is too large, the production process will be contaminated by falling off, so 0.001 to 10% by weight is preferable, and 0.005 to 5% by weight. % Is more preferable, and 0.0
1 to 1% by weight is more preferable.

The shape of the particles in the present invention is not particularly limited, but particles having sharp corners are not preferable because they may damage the precursor and reduce the strength.

In the present invention, if the average diameter of the particles is too small, the gap between the single yarns becomes small, and conversely if it is too large, it becomes difficult for the particles to enter between the single yarns and the strength improving effect becomes small.
5 to 50 μm is preferable, 0.07 to 10 μm is more preferable, and 0.1 to 1 μm is further preferable.

Since it is desirable that the particles in the present invention are continuously applied in the spinning process as described later, it is preferable to use them by dispersing them in water. Since it is difficult to sufficiently disperse the particles once dried in water, it is preferable to use an aqueous dispersion originally produced by a method such as emulsion polymerization or emulsion polymerization in water.

To define the particles in the present invention,
The particles need to be separated from the precursor by the following method.

When the particles are not dissolved in dimethyl sulfoxide, the following method is used. About 5 g of the precursor according to the present invention was immersed in 200 cc of dimethyl sulfoxide,
Heat at 0 ° C. for 2 hours to dissolve the precursor. Then, it is filtered with a glass fiber filter, and further 100cc
The above dimethyl sulfoxide and 100 cc or more of pure water are washed in this order and dried at 120 ° C. for 2 hours to separate particles,
Used for weighing and thermal analysis.

When the particles are dissolved in dimethyl sulfoxide, the following method is used. About 5g of precursor 5mm
Cut into pieces and put in 1000 cc of 1% aqueous solution of polyethylene glycol monooctyl phenyl ether,
Heat and stir for 2 hours. Then, the fibers are separated by a 50-mesh stainless steel wire mesh filter and washed with 100 cc or more of pure water to obtain a filtrate. The obtained filtrate is filtered with a glass fiber filter, further washed with 100 cc or more of pure water, and dried at 120 ° C. for 2 hours. Further, the fibers separated by the wire mesh filter are similarly dried, further put in toluene and heated and stirred at 80 ° C. for 2 hours. Then, separate the fibers with a 50 mesh stainless steel wire mesh filter,
A filtrate is obtained by washing with cc or more of toluene. The filtrate is filtered through the glass fiber filter described above, and then 100
It is washed with cc or more toluene and dried at 120 ° C. for 2 hours to separate the particles, which are then subjected to weighing, thermal analysis and the like.

The carbon fiber of the present invention may be any of acrylic type, pitch type, rayon type and the like, but an example of the acrylic type production method will be described.

The polyacrylonitrile constituting the precursor of acrylic carbon fiber is preferably a polymer containing 85% by weight or more of acrylonitrile and 15% by weight or less of a polymerizable unsaturated monomer copolymerizable with acrylonitrile. Examples of the polymerizable unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid and their alkali metal salts, ammonium salts and alkyl esters, acrylamide, methacrylamide and their derivatives, allylsulfonic acid, methallylsulfonic acid and Examples thereof include salts or alkyl esters thereof. In addition, it is preferable to copolymerize a polymerizable unsaturated monomer such as an unsaturated carboxylic acid which promotes a flame-resistant reaction. The copolymerization amount is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight, and 0.1 to 10% by weight.
More preferably, it is 5 to 3% by weight.

Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, ethacrylic acid, maleic acid and mesaconic acid. In order to obtain high-strength carbon fibers, it is preferable to copolymerize at least one selected from alkyl esters of unsaturated carboxylic acids and vinyl acetate. The copolymerization amount is preferably from 0.1 to 10% by weight, more preferably from 0.3 to 5% by weight,
It is more preferably 0.5 to 3% by weight. Specific examples of the alkyl ester of unsaturated carboxylic acid include methyl acrylate, methyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate,
Examples thereof include secondary butyl methacrylate, and among them, acrylic acid and propyl, butyl, isobutyl and secondary butyl methacrylates are preferred. .

As the polymerization method, suspension polymerization, solution polymerization,
A conventionally known method such as emulsion polymerization can be employed.
As the degree of polymerization, the intrinsic viscosity ([η]) is preferably 1.
It is 0 or more, more preferably 1.25 or more, and further preferably 1.5 or more. [Η] is preferably 5.0 or less from the viewpoint of spinning stability.

As the solvent in the case of solution spinning, known organic and inorganic solvents can be used, and specifically, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, nitric acid, an aqueous solution of rhodanese and an aqueous solution of zinc chloride are used as the solvent. The polymer solution to be used is the spinning dope.

The polymer can be made into a precursor by a known method. The spinning may be performed by a wet spinning method of directly spinning into a coagulation bath, a dry-wet spinning method of once spinning into air and then coagulating in a bath, or a dry spinning method or a melt spinning, but a high-strength carbon fiber Dry-wet spinning is preferred in order to obtain the desired properties.

In the case of the spinning method using a solvent and a plasticizer, the spun yarn may be drawn directly in the bath, or may be drawn in the bath after washing with water to remove the solvent and the plasticizer.
The condition of stretching in a bath is usually about 2 to 6 times stretching in a stretching bath at 50 to 98 ° C. The dried and densified yarn is dried by a hot drum or the like after drawing in a bath to achieve dry densification.
The drying temperature, time and the like can be appropriately selected. If necessary, the dried and densified yarn may be drawn at a higher temperature (for example, in pressurized steam), whereby a precursor having a predetermined fineness and orientation can be obtained. Also, prior to drying and densification,
It is preferable to add a silicone oil agent for the purpose of imparting heat resistance.

The particles may be applied at any time during the above-mentioned spinning process, but in order to uniformly apply the particles into the bundle of precursors, it is preferable to apply the particles in a region where the yarn width is widened, such as a washing bath and a drawing bath. It is preferable to impart particles dispersed or suspended in water in a process oil bath or the like.
It is also possible to apply a mixed liquid of the process oil and particles in the process oil bath. It is also possible to add particles before or after applying the step oil agent, and to insert a drying step therebetween.
The amount of particles at that time is preferably 0.001 to 100% by weight, more preferably 0.005 to 10% by weight, as a dry weight, in a weight ratio with respect to the process oil agent and the whole particles.
It is more preferably 0.01 to 1% by weight.

As a method of applying the oil agent and particles, a method of applying the thread to a driving or non-driving roller in an oil solution bath or a fixed or non-fixed guide bar and applying the thread to the thread, or an oil solution sprayed upward There are various methods such as a method of running and applying a yarn on the yarn, a method of dropping an oil solution onto the running yarn from above, a method of running the thread in a space sprayed with the oil solution, and the like can be appropriately selected. it can. Further, the particles can be provided on the surface by mixing and dispersing the particles in the polymer stock solution to be spun.

In the spinning step, particles may not be applied and may be applied prior to the subsequent firing step, but from the viewpoint of uniform application, application in the spinning step is preferred. The yarn width when imparting particles is preferably 3 mm or more per 3000 filaments, more preferably 10 mm or more, and further preferably 20 mm or more.

In order to obtain a carbon fiber having a high strength, a precursor having a high density is effective. As for elaboration,
A dense precursor having a lightness difference ΔL as measured by the iodine adsorption method is preferably 45 or less, more preferably 30 or less, and further preferably 15 or less. Means for obtaining a dense precursor having a ΔL of 45 or less include dry-wet spinning, increasing the concentration of the spinning dope, lowering the temperature of the spinning dope and the coagulating bath solution, and lowering the tension during coagulation. It is effective to keep the swelling degree of the bath drawn yarn low by optimizing the number of drawing steps, drawing ratio and drawing temperature during bath drawing.

ΔL is a value obtained by the following method. About 0.5 g of a dried sample having a fiber length of 5 to 7 cm was precisely weighed and placed in a 200 ml Erlenmeyer flask with a ground stopper, and an iodine solution (I ₂ : 51 g, 2,4-dichlorophenol 10 g, acetic acid 90 g and iodinated was added thereto. 100 g of potassium is precisely weighed, transferred to a 1-liter volumetric flask and dissolved in water to a constant volume) 100 ml is added, and adsorption treatment is performed at 60 ° C. for 50 minutes while shaking. The sample that adsorbed iodine was washed with running water for 30 minutes and then centrifugally dehydrated (2000 rpm x
1 minute) and air dry quickly. After opening this sample,
Hunter color difference meter [CM-25 manufactured by Color Machine Co., Ltd.
Type] to measure the lightness (L value) (L1). On the other hand, the corresponding sample not subjected to the adsorption treatment of iodine was opened, and similarly the lightness (L0) was measured by the Hunter type color difference meter to obtain L0.
The lightness difference .DELTA.L was obtained from -L1.

The single fiber fineness of the precursor is preferably thin so that firing unevenness does not occur in the subsequent flameproofing step from the viewpoint of improving strength, and preferably 1.5d.
Or less, more preferably 1.0 d or less, still more preferably 0.8 d or less.

By firing such a precursor, a high performance carbon fiber can be obtained. As the oxidizing condition, a conventionally known method can be adopted. Tension or stretching conditions are preferably used in an oxidizing atmosphere at a temperature of 200 to 300 ° C., and the density is preferably 1.25.
Heat treatment is performed until the amount reaches at least g / cm ³ , more preferably at least 1.30 g / cm ³ . This density is 1.60
Generally, the amount is not more than g / cm ³ , and if it is more than this, the physical properties may be deteriorated, which is not preferable. As the atmosphere, generally known air, oxygen, nitrogen dioxide, hydrogen chloride and the like oxidizing atmosphere can be used, but from the viewpoint of economy, air is preferable.

The flame-proofed yarn is carbonized in an inert atmosphere by a conventionally known method. The carbonization temperature is preferably 1000 ° C. or higher in view of the physical properties of the obtained carbon fiber, and can be graphitized at a temperature of 2000 ° C. or higher if necessary. Also, 350 to 500 ° C and 1
The heating rate at 000 to 1200 ° C. is preferably 50
0 ° C./min or less, more preferably 300 ° C./min or less, further preferably 150 ° C./min or less. Thereby, a dense carbon fiber having few internal defects such as voids can be obtained. If the heating rate is 10 ° C./min or less, the productivity is too low. 350-500 ° C
Alternatively, it is preferably 1% or more at 2300 ° C. or more,
It is more important to stretch 5% or more, more preferably 10% or more, from the viewpoint of improving the denseness.
Stretching exceeding 40% is not preferred because fluff is likely to occur.

The carbon fiber thus obtained is subjected to electrolytic oxidation treatment in an electrolytic cell made of an aqueous acid or alkali solution, or to vapor phase or liquid phase oxidation treatment to obtain a composite material. It is preferable to improve the affinity and adhesiveness between the carbon fiber and the matrix resin.

In particular, electrolytic oxidation is preferable because it can be oxidized in a short time and the degree of oxidation can be easily controlled. Both acidic and alkaline electrolytes can be used as the electrolytic solution for the electrolytic treatment. Any acidic electrolyte may be used as long as it exhibits acidity in an aqueous solution, and specific examples thereof include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, carbonic acid, acetic acid, butyric acid, oxalic acid, acrylic acid, and maleic acid. And organic acids such as ammonium sulfate, ammonium hydrogensulfate, and the like. Sulfuric acid and nitric acid which show strong acidity are preferred. Any alkaline electrolyte may be used as long as it shows alkalinity in an aqueous solution. Specifically, sodium hydroxide, potassium hydroxide,
Hydroxides such as barium hydroxide, inorganic salts such as ammonia, sodium carbonate and sodium hydrogen carbonate, organic salts such as sodium acetate and sodium benzoate, and potassium salts, barium salts or other metal salts thereof, and ammonium salts And organic compounds such as tetraethylammonium hydroxide and hydrazine. Preferred are ammonium carbonate, ammonium hydrogencarbonate, and tetraalkylammonium hydroxide which do not contain an alkali metal which causes a curing failure of the resin.

The amount of electricity is preferably optimized in accordance with the carbonization degree of the carbon fiber to be treated, and a high elastic modulus yarn requires a larger amount of electricity. From the viewpoint of improving the productivity while improving the crystallinity of the surface layer and preventing the strength of the carbon fiber substrate from decreasing, it is preferable to repeat the electrolytic treatment a plurality of times with a small amount of electricity. Specifically, the amount of electricity supplied to one electrolytic cell is preferably 5 coulombs / g · tank (1 g of carbon fiber, the amount of electricity per cell) to 100 coulombs / g · tank, and more preferably 10 coulombs / g. / G · tank or more, 80
Coulomb / g · tank or less, more preferably 20 coulomb / g · tank or more and 60 coulomb / g · tank or less. In addition, from the viewpoint of reducing the crystallinity of the surface layer to an appropriate range, the total amount of electricity in the energization treatment is preferably in the range of 5 to 1000 coulombs / g, and more preferably in the range of 10 to 500 coulombs / g.

After the electrolytic treatment or the washing treatment,
It is preferable to wash with water and dry. In this case, if the drying temperature is too high, the functional groups existing on the re-surface of the carbon fiber are likely to disappear by thermal decomposition. Therefore, it is desirable to dry at a temperature as low as possible. Specifically, the drying temperature is 250.
It is preferable to dry at a temperature of not higher than 0 ° C, more preferably not higher than 210 ° C.

Further, sizing can be performed by a conventionally known technique, if necessary.

The mechanical strength of the carbon fiber produced from the precursor for producing carbon fiber according to the present invention as described above is such that the resin-impregnated strand has a tensile strength of 300 kgf / mm ² or more. Preferably 4
00 kgf / mm ² or more, more preferably 500 kgf
/ Mm ² or more, more preferably 600 kgf / mm ²
The above is desirable. The tensile modulus of the carbon fiber is 20 ×
10 ³ kgf / mm ² or more, preferably 22 × 10 ³ k
gf / mm ² or more, more preferably 24 × 10 ³ kgf
/ Mm ² or more, more preferably 28 × 10 ³ kgf /
mm ² or more is desirable. The strand strength or elastic modulus, respectively 300 kgf / mm ² less than, or in the case of 20 × 10 ³ kgf / mm ² less of the carbon fibers, when a composite, may not desired characteristics as a structural material is there.

[0058]

EXAMPLES The present invention will be described in more detail below with reference to examples.

The tensile strength and elastic modulus in the present invention were obtained by the resin-impregnated strand method.

Tensile strength, elastic modulus: "Bakelite" ER
L-4221 (registered trademark, Union Carbide Co., Ltd.)
Made) / Boron trifluoride monoethylamine (BF ₃ · ME
A) / acetone = 100/3/4 part was impregnated into carbon fiber, the obtained resin-impregnated strand was heated at 130 ° C. for 30 minutes to be cured, and then according to the resin-impregnated strand test method specified in JIS-R-7601. It was measured.

Example 1 By a solution polymerization method using dimethyl sulfoxide as a solvent,
A spinning dope was obtained which was composed of 99% by weight of acrylonitrile and 1% by weight of itaconic acid and had [η] of 1.70 and a polymer concentration of 20%. This was once discharged into the air through a 3000 filament spinner and allowed to run in a space of about 3 mm, then coagulated in a 30% aqueous solution of dimethyl sulfoxide at 10 ° C, and the coagulated yarn was washed with water and then bathed up to 4 times. After stretching, a process oil agent containing 2% of amino-modified silicone oil agent and 0.1% of polytetrafluoroethylene (average particle size 0.3 μm) was applied, and then dried and densified. Furthermore, in pressurized steam 2.
Stretched up to 5 times, single yarn fineness 0.8d, total fineness 2400D
Got the precursor of. The adhered amount of particles was 0.1%. The carbonization residual rate of these particles was 0.1%.

The obtained precursor is 240 to 280 ° C.
In the air at a draw ratio of 1.05 and a density of 1.37 g
/ Cm ³ was obtained. Then, in a nitrogen atmosphere 35
The rate of temperature increase in the temperature range of 0 to 500 ° C. was set to 200 ° C./min, and the film was stretched at 2% and then fired to 1400 ° C.

Subsequently, an aqueous solution of sulfuric acid having a concentration of 0.1 mol / l was used as an electrolytic solution, electrolytic treatment was performed at 10 coulomb / g, and washing was performed with water.
It dried in 150 degreeC heating air. Table 1 shows the physical properties of the carbon fibers thus obtained.

Comparative Example 1 A carbon fiber was obtained in the same manner as in Example 1 except that the process oil was 2% of amino-modified silicone oil. The physical properties are shown in Table 1.

Example 2 A spinning stock solution having a copolymer composition of 98% by weight of acrylonitrile, 1% by weight of itaconic acid and 1% by weight of isobutyl methacrylate, [η] of 1.50 and a polymer concentration of 25% was used. A carbon fiber was obtained in the same manner as in Example 1 except for the above. The physical properties are shown in Table 1.

Comparative Example 2 A carbon fiber was obtained in the same manner as in Example 2 except that the process oil was 2% of amino-modified silicone oil. The physical properties are shown in Table 1.

Example 3 A carbon fiber was obtained in the same manner as in Example 1 except that the particles used were a tetrafluoroethylene-6 fluoropolypropylene copolymer (average particle size 0.2 μm). The physical properties are shown in Table 1. The carbonization residual rate of these particles was 0.1%.

Example 4 The particles used were phenol resin (particle size 1 to 10 μm)
A carbon fiber was obtained in the same manner as in Example 1 except that. The physical properties are shown in Table 1. Carbonization residual rate of these particles is 50%
Met.

Example 5 By a solution polymerization method using dimethyl sulfoxide as a solvent,
A spinning dope was obtained which was composed of 99% by weight of acrylonitrile and 1% by weight of itaconic acid and had [η] of 1.70 and a polymer concentration of 20%. This was once discharged into the air through a 3000 filament spinner and allowed to run in a space of about 3 mm, then coagulated in a 30% aqueous solution of dimethyl sulfoxide at 10 ° C, and the coagulated yarn was washed with water and then bathed up to 4 times. The film was stretched and a process oil solution containing 2% of an amino-modified silicone oil agent was applied.
Further, 10% of free rollers each having a diameter of 20 mm arranged in a zigzag shape by applying 30% of an aqueous dispersion containing 0.1% of fine particles (average particle diameter 0.3 μm) made of a crosslinked polystyrene resin to the dry weight of the yarn. The particles were squeezed to migrate into the yarn and then densified.
Further, it was drawn up to 2.5 times in pressurized steam to obtain a precursor having a single yarn fineness of 0.8 d and a total fineness of 2400D.
The adhered amount of particles was 0.02%.

The obtained precursor is 240 to 280 ° C.
In the air at a draw ratio of 1.05 and a density of 1.37 g
/ Cm ³ was obtained. Then, in a nitrogen atmosphere 35
The rate of temperature increase in the temperature range of 0 to 500 ° C. was set to 200 ° C./min, and the film was stretched at 2% and then fired to 1400 ° C.

Subsequently, an aqueous solution of sulfuric acid having a concentration of 0.1 mol / l was used as an electrolytic solution, electrolytic treatment was performed at 10 coulomb / g, and washing was performed with water.
It dried in 150 degreeC heating air. Table 1 shows the physical properties of the carbon fibers thus obtained.

Comparative Example 3 After applying a process oil solution consisting of 2% of amino-modified silicone oil agent, 30% of water per dry weight of yarn was applied and squeezed with 10 free rollers of 20 mm diameter arranged in zigzag. From the above, a carbon fiber was obtained in the same manner as in Example 5 except that the carbon fiber was dried and densified. The physical properties are shown in Table 1.

Example 6 The particles used were silicone resin (average particle size 0.5 μm).
A carbon fiber was obtained in the same manner as in Example 1 except that m) was used. The physical properties are shown in Table 1.

Example 7 The particles used were melamine resin (average particle size 0.5 μm)
A carbon fiber was obtained in the same manner as in Example 1 except that. The physical properties are shown in Table 1.

Example 8 The particles used were crosslinked polyethylene (average particle size 0.5 μm).
A carbon fiber was obtained in the same manner as in Example 1 except that m) was used. The physical properties are shown in Table 1.

Example 9 The particles used were polyacrylonitrile (average particle size: 0.
Carbon fiber was obtained in the same manner as in Example 1 except that the thickness was 5 μm). The physical properties are shown in Table 1.

Example 10 The spinning solution was directly discharged from the spinneret into a coagulation bath, stearyl alcohol ethylene oxide adduct 4%, amino-modified silicone 1%, polytetrafluoroethylene (average particle diameter 0.3 μm). A carbon fiber was obtained in the same manner as in Example 1 except that a 1% process oil was used. The physical properties are shown in Table 1.

Comparative Example 4 Neopentyl alcohol ethylene oxide adduct 4
% And amino modified silicone 1%, a carbon fiber was obtained in the same manner as in Example 10 except that a process oil agent was used.
The physical properties are shown in Table 1.

Comparative Example 5 The particles used were carbon black (average particle size 0.5 μm).
A carbon fiber was obtained in the same manner as in Example 1 except that m) was used. The physical properties are shown in Table 1. The carbonization residual rate of this particle is 90.
%Met.

[0080]

[Table 1]

[0081]

As described above, the precursor for producing carbon fiber of the present invention can efficiently provide carbon fiber having high strength.

Claims (10)

[Claims] 1. A precursor for producing carbon fiber, which has particles comprising one or more selected from an organic compound and a silicone compound on the fiber surface. 2. A precursor for producing carbon fiber, which has particles having a carbonization residual rate of 70% or less on the surface. 3. The average particle diameter of the particles is 0.05 to 50 μm.
The precursor for carbon fiber production according to claim 1 or 2, wherein 4. The adhered amount of particles is 0.001 to 10% by weight.
The precursor for carbon fiber production according to any one of claims 1 to 3, wherein 5. The particles contain any one of polytetrafluoroethylene, tetrafluoroethylene-6-fluoropropylene copolymer, phenol resin, melamine resin, polystyrene, polyethylene, polyacrylonitrile, silicone rubber and silicone resin. The precursor for carbon fiber production according to any one of claims 1 to 4, 6. The precursor for producing carbon fiber according to any one of claims 1 to 5, wherein the particles contain fluorine or silicon. 7. A method for producing a precursor for producing carbon fiber, which comprises applying particles comprising one or more selected from an organic compound and a silicone compound to the fiber surface. 8. A method for producing a precursor for producing carbon fiber, which comprises imparting particles having a carbonization residual rate of 70% or less to the fiber surface. 9. A method for producing a carbon fiber, which comprises firing a precursor for producing a carbon fiber, the precursor of which has particles made of one or more kinds selected from organic compounds and silicone compounds on the fiber surface. 10. A method for producing a carbon fiber, which comprises firing a precursor for producing a carbon fiber having particles having a carbonization residual rate of 70% or less on the fiber surface.