JP2005281883A - Method for producing flameproofed fiber and carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing carbon fiber with excellent properties including tensile strength through enabling drawing of unconventionally high draw ratio in the flameproofing step. <P>SOLUTION: A method for producing acrylic flameproofed fiber is provided, comprising flameproofing acrylic fiber in air and then drawing the resultant fiber under heating at 50-150°C in the presence of at least one organic compound. The method for producing the carbon fiber comprises treating the above-obtained acrylic flameproofed fiber at 300-3,000°C in an inert atmosphere. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to flame-resistant fibers, carbon fibers, and methods for producing them. More specifically, the present invention relates to a carbon fiber excellent in cost performance, a flame-resistant fiber suitable for obtaining the carbon fiber, and a method for producing them at a low cost.

  Carbon fibers are used in various applications because of their excellent mechanical and electrical properties. In recent years, in addition to conventional golf clubs, fishing rods and other sports and aircraft applications, development of so-called general industrial applications such as automobile members, CNG tanks, seismic reinforcement of buildings, ship members, etc. has progressed. Performance is required.

  Industrially, carbon fibers are manufactured through flameproofing of precursor fibers such as polyacrylonitrile by heat treatment in air at 200 to 300 ° C. and carbonization by heat treatment in an inert atmosphere at 300 to 3000 ° C. At this time, it is known that the strand strength and the strand elastic modulus, which are generally basic physical properties of carbon fiber, increase as the film is highly stretched in the firing step. However, as the draw ratio is increased, fluffing and single fiber breakage occur, and the processability decreases, so that there is a limit to the draw ratio for stable operation.

  On the other hand, it is known that the strand strength and strand elastic modulus of carbon fiber increase as the single fiber diameter is reduced. Reducing the single fiber diameter of the resulting carbon fiber can be achieved by reducing the single fiber diameter of the precursor fiber used or increasing the draw ratio in the firing step. Up and the latter are problematic as described above, and it is difficult to improve cost performance further.

  On the other hand, in order to improve stretchability in the flameproofing process of the firing process, several techniques have been proposed.

  For example, a technique of highly stretching by controlling the stretching profile in the flameproofing process is disclosed (for example, see Patent Document 1).

  According to such a technique, although a high draw ratio of 1.6 times can be obtained, according to the study by the present inventors, (1) increase the copolymerization of polyacrylonitrile precursor fiber, (2) polyacrylonitrile precursor There is a problem that it is necessary to reduce the draw ratio at the time of fiber production, and (3) to reduce the yarn running speed at the time of flame resistance, both of which cannot be avoided.

Moreover, the technique of extending | stretching highly by making flame resistance in the organic compound except an amine compound is disclosed (for example, refer patent document 2). According to such a technique, although a draw ratio of 1.7 times can be obtained, there is a problem that the equipment cost in terms of disaster prevention is unavoidable because treatment at a high temperature of 180 ° C. to 300 ° C. is necessary. It was.
JP 58-186614 A International Publication No. 02/095100 Pamphlet

  An object of the present invention is to provide a carbon fiber excellent in cost performance and a flame-resistant fiber suitable for obtaining the carbon fiber. Furthermore, it is providing the flame-resistant fiber and the manufacturing method of carbon fiber with high productivity suitable for manufacturing these.

  In order to solve the above problems, the present invention employs the following means. That is, after making an acrylic fiber flame resistant in air, it is a method for producing an acrylic flame resistant fiber that is stretched by heating at 50 to 150 ° C. in the presence of at least one organic compound.

  Furthermore, it is the manufacturing method of carbon fiber which heat-processes the flameproof fiber obtained by the said method at 300-3000 degreeC by inert atmosphere.

  According to the method for producing flame-resistant fibers and carbon fibers of the present invention, the draw ratio in the flame-proofing process can be improved, thereby improving the productivity of the firing process. That is, a carbon fiber having a thin single fiber diameter can be obtained without reducing the single fiber diameter of the precursor fiber to be used, and a carbon fiber having excellent strand strength and strand elastic modulus can be obtained at low cost.

  The inventors of the present invention have found that the stretchability of the flameproofing step can be greatly improved by performing a heat-stretching treatment in the presence of an organic compound after the flameproofing treatment in air that is generally performed. In the prior art, since the precursor fiber is stretched while making it flame resistant in heated air, the stretching is difficult as the flame resistant structure is developed. On the other hand, in the present invention, after making flame resistant in heated air, by heating in an organic compound, a part of the organic compound penetrates into the inside of the air flame resistant fiber and plasticizes the fiber. The draw ratio can be greatly improved by the time treatment. As a result, it is possible to reduce the single fiber diameter of the obtained carbon fiber without reducing the single fiber diameter of the precursor fiber, and it is possible to produce a high-performance carbon fiber without reducing productivity. Hereinafter, the method for producing flame-resistant fibers and carbon fibers of the present invention will be described in detail.

  In the method for producing flame-resistant fibers of the present invention, acrylic fibers are flame-resistant in air, then heated to 50 to 150 ° C. in the presence of at least one organic compound, and stretched. In the following, fibers obtained by flame-proofing acrylic fibers in air are air-flame-resistant fibers, and fibers obtained by heating and drawing the air-flame-resistant fibers in the presence of at least one organic compound are drawn and flame-resistant fibers. Is written.

In the present invention, if the compound used for heat-stretching the air flame-resistant fiber is at least one organic compound, a certain stretchability improving effect is exhibited. From the viewpoint of further enhancing the stretchability, it is preferable to appropriately select a compound having a high affinity with the precursor fiber. As an affinity index, solubility parameters can be preferably used. Here, the solubility parameter δ is the solubility parameter δ = c ^1/2 where c is the cohesive energy density of the solvent.
The cohesive energy density c is expressed by the following equation: c = (ΔHv−RT) / Vm where ΔHv is the heat of evaporation per unit volume of the solvent, Vm is the molar volume, T is the temperature, and R is the gas constant.
Defined.
The closer this dissolution parameter is to the air flame resistant fiber, the higher the affinity and the better. The specific numerical range of the solubility parameter of the organic compound is preferably 5 to 15, more preferably 7 to 13, and still more preferably 8 to 12.

  From the viewpoint of further increasing the affinity, the organic compound preferably contains at least one selected from an amino group, an imino group, a nitrilo group, and a hydroxyl group, more preferably two or more, and more preferably three or more. It is further preferable to include it.

  The boiling point of the organic compound is preferably higher than the heat treatment temperature because it can be processed at normal pressure. Specifically, the boiling point is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, and further preferably 200 ° C. or higher.

  Specific examples of the organic compound include amines, alcohols, phenols, amino alcohols, and the like. More specifically, octylamine, dioctylamine, trioctylamine, ethanediamine, propanediamine, butanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, aminoethylpiperazine, 1,8-diaza Aliphatic amines such as bicycloundecene (5,4,0) -7, aromatic amines such as aniline and toluidine, glycols such as ethylene glycol, diethylene glycol, triethylene glycol and glycerin, phenols such as phenol, cresol and aminophenol More preferred are amino alcohols such as monoethanolamine, diethanolamine, triethanolamine and 2- (2-aminoethylamino) ethanol.

  Moreover, from the viewpoint of economically removing the organic compound from the viewpoint of washing and removing the extra portion adhering to the outside of the fiber after the heat-drawing treatment, it is preferable from the economical aspect.

  In the present invention, it is necessary to appropriately adjust the temperature and time of the heat treatment in order to heat and stretch the air flameproof fiber together with the organic compound described above. Basically, the higher the temperature, the longer the time, the higher the draw ratio. However, depending on the compound used, if the temperature is raised too much or if the time is too long, the fiber may decompose, and the draw ratio may decrease.Considering the reactivity and affinity between the compound and the fiber The temperature and time for heat treatment should be set. The optimum values of the temperature and time during the heat treatment vary depending on the compound, and thus cannot be limited to one, but the heat treatment temperature needs to be set to 50 to 150 ° C. If the temperature is below 50 ° C., it becomes impossible to achieve the above-mentioned draw ratio in a practical time. If the temperature exceeds 150 ° C., the plasticization of the fiber becomes excessive and the degradation loss becomes remarkable, and the high stretch intended by the present invention is achieved. The magnification cannot be obtained. The heat treatment temperature is more preferably 70 to 145 ° C, and further preferably 90 to 140 ° C. The heat treatment time may be set to the time necessary to achieve the above-mentioned draw ratio, but is preferably a short time economically, more preferably 1 second to 300 minutes, and more preferably 5 seconds. More preferably, it is -120 minutes.

  In the method for producing flame-resistant fibers of the present invention, the draw ratio of the flame-resistant fibers in the presence of an organic compound is preferably 1.1 to 3 times, more preferably 1.2 to 2.5 times. More preferably 3 to 2 times. If the ratio is less than 1.1 times, not only the effect of reducing the single fiber diameter will be reduced, but also the processing tension will be lowered, the yarns will adhere to each other and the rollers will come off the groove, the quality will be lowered and the operation will deteriorate. There is. Moreover, when it exceeds 3 times, the fineness nonuniformity will generate | occur | produce in the fiber longitudinal direction, and the quality and quality of the carbon fiber obtained may fall.

  The acrylic fiber used in the present invention may be 100% acrylonitrile, but is preferably a copolymer from the viewpoint of improving flame resistance efficiency and from the viewpoint of yarn production. As the copolymerization component, acrylic acid, methacrylic acid, itaconic acid and the like are preferably mentioned as so-called flame resistance promoting components, and more preferably, a part or all of these are neutralized with ammonia, acrylic acid, methacrylic acid, Or the copolymer which consists of an ammonium salt of itaconic acid is mentioned. From the viewpoint of improving the yarn production, methacrylic acid esters, acrylic acid esters, allyl sulfonic acid metal salts, methallyl sulfonic acid metal salts, and the like are preferably copolymerizable.

  The total amount of the above-mentioned copolymer is preferably 0 to 10 mol%, more preferably 0.1 to 6 mol%, and further preferably 0.2 to 2 mol%. If the amount of the copolymer is small, the yarn-forming property is lowered, and if the amount of the copolymer is large, the heat resistance is lowered and the fusion process is likely to occur in the subsequent flameproofing process. It is good to do.

  A method for polymerizing such a copolymer is not particularly limited, and a solution polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be applied.

  When spinning the acrylic copolymer, an organic or inorganic solvent can be used, but it is preferable to use an organic solvent, and specific examples include dimethyl sulfoxide, dimethylformamide, dimethylacetamide and the like.

  As described above, a spinning dope comprising an acrylic copolymer and a solvent is spun from a die by a wet spinning method, a dry wet spinning method, a dry spinning method, or a melt spinning method, preferably a wet spinning method or a dry wet spinning method. And introduced into a coagulation bath to coagulate the fiber.

  In the wet spinning method and the dry and wet spinning method, the surface roughness of the precursor fiber surface can be controlled by appropriately controlling the coagulation rate, the stretching method, and the like. For example, when the coagulation rate is increased, a coagulated fiber having a thick skin layer formed on the fiber surface and a small fibril unit constituting the fiber can be obtained, and the coagulated fiber is drawn by a method as described later. A precursor fiber suitable for obtaining a carbon fiber having a smooth surface and high strand strength is preferable. However, if the coagulation rate is too high, the internal structure of the coagulated yarn becomes coarse, and carbon fibers having high strand strength may not be obtained. Therefore, it is preferable to set the coagulation rate in consideration of both.

  In the present invention, the coagulation bath can contain a so-called coagulation promoting component, and the coagulation rate can be controlled by the temperature of the coagulation bath and the concentration of the coagulation promoting component. Specifically, the higher the coagulation bath temperature and the greater the amount of the coagulation promoting component, the faster the coagulation rate. As the coagulation accelerating component, a component that does not dissolve the acrylic copolymer and is compatible with the solvent used in the spinning dope can be used. Specifically, it is preferable to use water.

  After being introduced into a coagulation bath and coagulating the yarn, acrylic fibers are obtained through washing with water, stretching, application of oil, drying and the like. Moreover, it can also extend | stretch with steam after oil agent provision. Here, the solidified yarn may be stretched directly in a stretching bath without being washed with water, or may be stretched in a bath after removing the solvent by washing. Such stretching in a bath is usually performed in a single or a plurality of stretching baths whose temperature is adjusted to 30 to 98 ° C., and in these washing baths and stretching baths, inclusion of the solvent used in the spinning dope described above in an aqueous solution. The rate should be the upper limit of the content of the solvent in the coagulation bath.

  After the bath stretching, it is preferable to apply an oil agent made of silicone or the like to the yarn. Such a silicone oil agent is preferably a modified silicone and an amino-modified silicone having high heat resistance.

  The yarn stretched in the bath and provided with the oil agent is preferably dried by heating. It is efficient to carry out the drying treatment by bringing it into contact with a roll heated to 50 to 200 ° C. It is preferable to dry the yarn until the moisture content of the yarn is 1% by weight or less, thereby densifying the fiber structure.

  The acrylic fiber used in the present invention is preferably a bundle-like acrylic fiber, and the number of filaments per yarn is preferably 1,000 to 300,000, more preferably 3,000 to 100,000. More preferably, it is 6,000-50,000, Most preferably, it is 12000-24000.

  The single fiber fineness of the acrylic fiber used in the present invention is preferably 0.5 to 20 dtex, more preferably 0.7 to 15 dtex, and further preferably 1 to 10 dtex. The finer the single fiber fineness is, the more preferable from the viewpoint of increasing the strand strength of the carbon fiber to be obtained, but at the same time the productivity is lowered.

In the present invention, the air flame-resistant fiber can be obtained by heat treatment at 200 to 300 ° C. in an oxidizing atmosphere, preferably in air, using the acrylic fiber described above. The temperature and time can be appropriately selected, but the specific gravity of the obtained flame-resistant fiber is preferably 1.3 to 1.5, more preferably 1.32 to 1.45, and still more preferably 1.34 to 1.4. It is preferable to heat-treat until. If the specific gravity of the flame resistant fiber is less than 1.3, the flame resistant structure is not yet developed, so that there is a tendency for thread breakage to occur during heating and stretching in the presence of the organic compound. It may be too developed and difficult to stretch.
0.85 to 1.05 is preferable, 0.9 to 1.02 is more preferable, and 0.95 to 1 is even more preferable.

  After the heat treatment in the presence of the organic compound, the extra organic compound adhering thereto can be removed. As a removal method, heating, drying treatment under reduced pressure, washing with a low boiling point solvent, or the like can be used. It is preferable from an economical point of view to remove excess organic compounds and further recover and reuse them.

  Carbon fiber can be produced by heat-treating and carbonizing the stretched flame-resistant fiber obtained by the above-described method in an inert atmosphere at 300 to 3000 ° C. From the viewpoint of equipment, the carbonization treatment is performed by dividing it into a preliminary carbonization step of 300 ° C or higher and lower than 1000 ° C, a carbonization step of 1000 ° C or higher and lower than 2000 ° C, and a graphitization step of 2000 ° C or higher and 3000 ° C or lower. preferable. The maximum treatment temperature of the carbonization treatment can be selected according to the desired physical properties of the carbon fiber, and the graphitization step can be omitted.

  The carbonization treatment is preferably performed on stretched flame resistant fibers under tension or stretching conditions. More preferably, the draw ratio is 0.8 to 1.3, and more preferably 0.9 to 1.2. If the draw ratio is less than 0.8, the resulting carbon fiber strand strength may be insufficient, and if it exceeds 1.3, fluff and yarn breakage tend to increase.

  The carbon fiber obtained by the above-described method can be subjected to electrolytic treatment for surface modification. As an electrolytic solution used for the electrolytic treatment, an acidic solution such as sulfuric acid, nitric acid, and hydrochloric acid, an alkali such as sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, or a salt thereof can be used as an aqueous solution. Here, the amount of electricity required for the electrolytic treatment can be appropriately selected depending on the carbon fiber to be applied.

  By such electrolytic treatment, the adhesion between the carbon fiber and the matrix resin can be optimized in the obtained composite material, and balanced strength characteristics can be expressed in the obtained composite material.

  Thereafter, a sizing treatment can be performed to impart convergence to the obtained carbon fiber. As the sizing agent, a sizing agent having good compatibility with the resin can be appropriately selected according to the type of resin used.

  The carbon fiber obtained in this way can be prepreg and then molded into a composite material. After forming a preform such as a woven fabric, it is combined by a hand lay-up method, a pultrusion method, a resin transfer molding method, etc. It can also be formed into a material. Further, it can be formed into a composite material by a filament winding method or by injection molding after chopped fiber or milled fiber.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example, this invention is not limited at all by these Examples. The production conditions of each example are shown in Table 1, the processability evaluation results at the time of heating and stretching in the presence of an organic compound are shown in Table 2, and the characteristics of the obtained carbon fibers are summarized in Table 3. Each measured value in this example was measured by the following method.

<Specific gravity of flame resistant fiber>
The specific gravity of the air flame-resistant fiber was measured according to the method described in JIS R7601 (1986). As a reagent, ethanol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was used without purification. 1.0 to 1.5 g of flameproof fiber bundle was collected and dried at 120 ° C. for 2 hours. After the absolute dry weight (A) was measured, it was impregnated with ethanol having a known specific gravity (specific gravity ρ), and the flame-resistant fiber bundle weight (B) in ethanol was measured. The specific gravity was calculated according to the following formula (7).
Flameproof yarn specific gravity = (A × ρ) / (A−B)
<Maximum stretch ratio at the time of heat stretching in the presence of an organic compound (maximum stretch ratio)>
The film is heated and stretched in the presence of an organic compound, the draw ratio is changed by 0.05, the presence or absence of yarn breakage when operating for 30 minutes is visually confirmed, and the maximum draw ratio at which no yarn breaks is taken as the maximum draw ratio.

<Process stability during heat stretching in the presence of organic compounds>
The operation was continued for one week, and the occurrence of fluff and yarn breakage was visually confirmed, and the evaluation was made according to the following criteria. In addition, fluff generation | occurrence | production counted the number of fluff after a heat-stretching process for 10 yarn * 60 minutes, and represented it with the number per length.
○: Yarn break 0 times, fluff 0-0.1 co / m
Δ: Thread breakage 0 times, fluff 0.2-3 co / m
X: One or more thread breaks <Measurement of carbon fiber strength and elastic modulus>
It measured according to JIS R7601 (1986). The test piece was prepared by impregnating carbon fiber with the following resin composition and curing conditions of heat treatment at 130 ° C. for 35 minutes.

Resin composition: 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane-carboxylate (100 parts by weight) / 3 boron fluoride monoethylamine (3 parts by weight) / acetone (4 parts by weight)
As 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane-carboxylate, ERL-4221 manufactured by Union Carbide Corporation was used.

[Example 1]
A copolymer consisting of 99.5 mol% of acrylonitrile and 0.5 mol% of itaconic acid was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent, and ammonia gas was blown until the pH reached 8.5, and itaconic acid was added. While neutralizing, an ammonium group was introduced into the acrylic copolymer to obtain a spinning dope having a copolymer component content of 22% by weight.

  This spinning dope was discharged into air at 40 ° C. using a spinneret having a diameter of 0.15 mm and a hole number of 3,000, passed through a space of about 4 mm, and then 35% dimethyl controlled at 3 ° C. A coagulated yarn was obtained by a dry and wet spinning method introduced into a coagulation bath made of an aqueous solution of sulfoxide.

  The coagulated yarn was washed with water, then stretched 3.5 times in warm water, and further an amino-modified silicone-based silicone oil was applied to obtain a stretched yarn.

  The drawn yarn is dried and densified using a 160 ° C. heating roller, and drawn in 0.3 MPa-G pressurized steam, so that the total draw ratio of yarn production is 13 times, and the single fiber fineness is 1 An acrylic fiber having 1 dtex and 3000 single fibers was obtained.

  Four acrylic fibers obtained were combined to make 12,000 single fibers, and the first stage 240 ° C, the second stage 260 ° C, the draw ratio 1st stage 0.98, the second stage 1.02 in air. The flameproofing treatment was carried out until the specific gravity of the flameproofing fiber became 1.4 to obtain an air flameproofing fiber. Subsequently, a stretched flameproof fiber was obtained in a liquid composed of diethylenetriamine (manufactured by Tosoh Corporation) as an organic compound at 80 ° C. for 1 minute at a stretch ratio of 1.3.

  This stretched flameproof fiber is washed with water, dried, then heated in an inert atmosphere at a heating rate of 500 ° C./min from 300 ° C. to 1000 ° C., pre-carbonized, and then the highest temperature in the inert atmosphere Carbonization treatment was performed at 1400 ° C. to obtain bundled carbon fibers.

  The evaluated process properties and carbon fiber properties are summarized in Tables 2 and 3.

[Example 2]
Bundled flameproof fibers and carbon fibers were obtained in the same manner as in Example 1 except that the treatment temperature at the time of heating and stretching in the presence of an organic compound was 140 ° C. and the stretch ratio was 1.7. The results are summarized in Tables 2 and 3.

[Example 3]
A bundle of flame-resistant fibers was used in the same manner as in Example 1 except that diethanolamine (manufactured by Mitsui Chemicals, Inc.) was used as the organic compound to be used, and the draw ratio during heat drawing in the presence of the compound was 1.1. And carbon fiber was obtained. The results are summarized in Tables 2 and 3.

[Example 4]
A bundle of flame-resistant fibers was used in the same manner as in Example 2 except that diethanolamine (manufactured by Mitsui Chemicals, Inc.) was used as the organic compound to be used, and the draw ratio during heat drawing in the presence of the compound was 1.3. And carbon fiber was obtained. The results are summarized in Tables 2 and 3.

[Example 5]
A bundle-like flameproof fiber and carbon fiber were obtained in the same manner as in Example 2 except that the draw ratio at the time of heat drawing in the presence of an organic compound was 1.05. The results are summarized in Tables 2 and 3.

[Example 6]
An air flame-resistant fiber was obtained in the same manner as in Example 1 except that the flame resistance treatment was performed until the specific gravity of the air flame-resistant fiber reached 1.28. Subsequently, bundle-like flameproof fibers and carbon fibers were obtained in the same manner as in Example 2 except that the draw ratio at the time of heat drawing in the presence of an organic compound was 1.2. The results are summarized in Tables 2 and 3.

[Example 7]
An air flame-resistant fiber was obtained in the same manner as in Example 1 except that the flame resistance treatment was performed until the specific gravity of the air flame-resistant fiber became 1.51. Subsequently, bundle-like flameproof fibers and carbon fibers were obtained in the same manner as in Example 2 except that the stretch ratio at the time of heat stretching in the presence of the organic compound was 1.3. The results are summarized in Tables 2 and 3.

[Comparative Example 1]
The flameproofing treatment and carbonization treatment were carried out by the method described in Example 1 except that the temperature during heat drawing in the presence of an organic compound was 30 ° C. and the draw ratio was 1.05. Frequently, stretched flameproof fibers and carbon fibers could not be obtained.

[Comparative Example 2]
Flame-resistant treatment and carbonization treatment were carried out by the method described in Example 1 except that the temperature at the time of heat drawing in the presence of an organic compound was 180 ° C. and the draw ratio was 0.95. As a result, yarn breakage due to the occurrence of the fiber occurred frequently, and it was impossible to obtain stretched flameproofed fibers and carbon fibers.

[Comparative Example 3]
Acrylic fibers obtained by the method described in Example 1 were combined to obtain 12,000 single fibers, flame resistance in air was not performed, and the draw ratio in the presence of an organic compound was 1.0. Was subjected to a flameproofing treatment in the same manner as in Example 2. However, yarn breakage occurred frequently in the heating step, and stretched flameproofed fibers and carbon fibers could not be obtained.

[Comparative Example 4]
The air flame-resistant fiber obtained by the method described in Example 1 was further heat-treated in air at 140 ° C. for 1 minute at a draw ratio of 1.05. However, yarn breakage occurred frequently, and the flame-resistant fiber and carbon fiber were Couldn't get.

[Comparative Example 5]
Using air-flame-resistant fibers obtained by the method described in Example 1, heat-stretching in the presence of an organic compound was not performed, and carbonization was performed in the same manner as in Example 1 to obtain bundled carbon fibers. The results are summarized in Tables 2 and 3.

Claims (5)

A method for producing an acrylic flame-resistant fiber, which comprises making an acrylic fiber flame resistant in the air and then heating and stretching at 50 to 150 ° C. in the presence of at least one organic compound. The method for producing an acrylic flame resistant fiber according to claim 1, wherein the specific gravity after the acrylic fiber is flame resistant in air is 1.30 to 1.50. The method for producing an acrylic flameproof fiber according to claim 1 or 2, wherein the organic compound has at least one amino group. The method for producing an acrylic flameproof fiber according to any one of claims 1 to 3, which is stretched at least 1.1 times to 3 times. The manufacturing method of the carbon fiber which processes the acrylic flameproof fiber obtained by the manufacturing method in any one of Claims 1-4 at 300-3000 degreeC by inert atmosphere.