JP2008190056A - Method for producing flameproof fiber bundle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a flameproof fiber bundle and a carbon fiber bundle in which suppression of deterioration in bundling properties of the fiber bundle with static electricity and suppression of formation of fine powder derived from a silicone-based compound can simultaneously be achieved. <P>SOLUTION: The method for producing the flameproof fiber bundle is carried out as follows: A spinning finish composition containing the silicone-based compound in an amount of 0.1-3.0 mass% based on the fiber mass of a carbon fiber precursor acrylic fiber bundle is applied thereto and a flameproofing finish composition containing 60-90 mass% of a specific aromatic ester, 1-10 mass% of an antioxidant, and 9-35 mass% of a nonionic surfactant with a residual ratio of ≤1.0 mass% after heating at 250°C for 2 h in an amount of 0.1-3.0 mass% based on the fiber mass, is applied to the carbon fiber precursor acrylic fiber bundle just before carrying out a flameproofing treatment thereof. The resultant fiber bundle is then heated in an oxidizing atmosphere at 200-300°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a flameproof fiber bundle.

  Generally, as a method for producing a carbon fiber bundle using a carbon fiber precursor acrylic fiber bundle, a fiber bundle obtained by bundling thousands to tens of thousands of single fibers of an acrylic fiber under an oxidizing atmosphere at 200 to 300 ° C. After heat treatment (hereinafter referred to as flame resistance treatment or flame resistance process) to obtain a flame resistant fiber bundle, heat treatment (hereinafter referred to as pre carbonization process or pre carbonization process) in an inert gas atmosphere at 300 to 1000 ° C. Then, a method of performing a heat treatment (hereinafter, carbonization treatment or carbonization step) in an inert gas atmosphere at 1000 ° C. or higher is known.

  Since this flameproofing treatment is an oxidation reaction accompanied by heat generation, a fusion phenomenon is likely to occur between the single fibers due to the temperature during the treatment and the large amount of heat generation accompanying the oxidation reaction. The quality of the flame-resistant fiber bundle in which the fusion phenomenon has occurred is remarkably lowered. For example, in the subsequent carbonization process, troubles such as generation of fluff and yarn breakage occur.

  In order to avoid this fusion, it is known that the oil agent applied to the carbon fiber precursor acrylic fiber bundle is important, and many oil agents have been studied. Among these, a silicone compound-containing oil agent is often used because it has high heat resistance and effectively suppresses fusion (for example, Patent Document 1).

  In the flameproofing step of converting the carbon fiber precursor acrylic fiber bundle into the flameproofed fiber bundle, an oxidizing gas heated by a heater or the like is circulated in the flameproofing furnace by a fan. In this case, a part of the silicone compound-containing oil agent volatilizes into the oxidizing gas during the flameproofing step, and the volatilized silicone compound stays in the flameproofing furnace for a long time.

  Further, the silicon-based compound that has remained in the flameproofing furnace for a long time is solidified and adheres to the fiber bundle being processed as a fine powder. The adhesion point of the fine powder becomes a starting point of generation of fluff and single yarn breakage in the subsequent high-temperature carbonization step, and remarkably deteriorates the performance of the obtained carbon fiber.

  Oil components other than silicone compounds, tar components derived from acrylonitrile copolymer components, dust, etc. are also factors that reduce the strength of carbon fiber, but the influence of fine powder of the silicone compounds caused by silicone compounds Is particularly prominent.

  Therefore, it is difficult to keep the flameproofing process in operation for a long period of time, and it is sometimes necessary to stop the operation and clean the inside of the furnace. However, it is difficult to completely remove fine particles having a particle size of about several μm, and particularly in the case of a large facility, a great amount of personnel and time are required for cleaning the inside of the furnace.

  In addition, there are many fine powders on the surface of the single fiber of the flame resistant fiber bundle obtained at the initial stage of restart after cleaning the inside of the furnace, and the strength of the carbon fiber obtained by carbonizing the flame resistant fiber bundle is remarkably high. A decreasing phenomenon has been confirmed.

  Further, when a silicone oil is used, static electricity is likely to occur due to the water repellency of the silicone compound. For this reason, static electricity is generated in a metal roller or the like disposed in the manufacturing process, the convergence property of the fiber bundle is lowered, and winding of the roller is also a problem.

In Patent Document 2, in order to suppress static electricity, a silicone-based oil agent is attached to the carbon fiber precursor acrylic fiber bundle, and the moisture content is adjusted so that the water content is 10% by mass or more, thereby preventing moisture divergence. In order to do so, it has been proposed to supply and burn to a flameproofing furnace while preserving it under high humidity.
However, immediately after being supplied into a flameproofing furnace that is heat-treated in an atmosphere of 200 to 300 ° C., water evaporation occurs, maintaining the convergence of the fiber bundle in the flameproofing process, and winding around the roller. It was not enough to suppress.

  In Patent Document 3, a silicone compound and a non-silicone compound are blended in order to suppress generation of fine powder derived from a silicone compound in a flameproofing furnace and to suppress a decrease in convergence of a fiber bundle due to static electricity. Used as a spinning process oil.

However, since the oil agent for the spinning process is usually applied to the fiber bundle in a water-swollen state, it easily penetrates into the fiber. Since the non-silicone compound that has penetrated into the fiber is inferior in heat resistance to the silicone compound, it tends to be defective when converted to carbon fiber, and there is a concern that the quality of the obtained carbon fiber is lowered.
In addition, when a silicone compound and a non-silicone compound are blended, the migration of the silicone compound and the non-silicone compound occurs with the passage of time until being put into the flameproofing treatment furnace, and the carbon fiber precursor acrylic fiber bundle is transferred to the bundle. It is difficult to maintain uniform adhesion. Furthermore, the silicone present in the vicinity of the fiber surface tends to volatilize in an oxidizing atmosphere during the flame resistance process.

Japanese Patent Laid-Open No. 11-12855 JP 61-132632 A JP 2000-199183 A

  An object of the present invention is to provide a method for producing a flame-resistant fiber bundle and a carbon fiber bundle, which can simultaneously achieve suppression of decrease in convergence of a fiber bundle due to static electricity and suppression of generation of fine powder derived from a silicone compound. To do.

（式中、Ｒ^１及びＲ^２は、それぞれ独立して炭素数７〜２１のアルキル基であり、Ａ^１及びＡ^２は、それぞれ独立してエチレン基又はプロピレン基であり、ｍ及びｎは、それぞれ独立して１〜５の整数を表す） That is, the gist of the present invention is to provide an oil agent composition containing a silicone compound in an amount of 0.1 to 3.0% by mass per fiber mass of the carbon fiber precursor acrylic fiber bundle, and then immediately before the flame resistance treatment, An oil-resistant composition comprising the following mixture A is further added to the fiber precursor acrylic fiber bundle in an amount of 0.1 to 3.0% by mass per fiber mass and heated in an oxidizing atmosphere at 200 to 300 ° C. It is a manufacturing method.
Mixture A:
Nonionic interface having an aromatic ester represented by the following (1) of 60 to 90% by mass, an antioxidant of 1 to 10% by mass, and a residue ratio after heating at 250 ° C. for 2 hours of 1.0% by mass or less. Contains 9-35% by weight of activator.

(Wherein R ¹ and R ² are each independently an alkyl group having 7 to 21 carbon atoms, A ¹ and A ² are each independently an ethylene group or a propylene group, and m and n are Each independently represents an integer from 1 to 5)

  According to the present invention, it is possible to simultaneously suppress the decrease in the convergence of the fiber bundle due to static electricity and the suppression of the generation of fine powder derived from the silicone compound, the operability in the flameproofing process, the process passability is significantly improved, At the same time, it is possible to produce flame-resistant fiber bundles and carbon fiber bundles that have excellent physical properties and quality and are stable.

The present invention is described in detail below.
In the method for producing a flame-resistant fiber bundle of the present invention, an oil agent composition containing a silicone compound is applied in an amount of 0.1 to 3.0% by mass per fiber mass of the carbon fiber precursor acrylic fiber bundle, and then subjected to flame resistance treatment. Immediately before, 0.1 to 3.0% by mass of the oil agent composition consisting of the mixture A is further added to the carbon fiber precursor acrylic fiber bundle per mass of the fiber and heated in an oxidizing atmosphere at 200 to 300 ° C.

Hereinafter, the manufacturing method of the flame-resistant fiber bundle of this invention is demonstrated sequentially.
(spinning)
The carbon fiber precursor acrylic fiber bundle of the present invention is prepared by dissolving an acrylonitrile-based polymer in an organic solvent or an inorganic solvent and spinning by a commonly used method, and the spinning method and conditions are not particularly limited. . Here, although there is no restriction | limiting in particular as an acrylonitrile-type polymer, The polymer containing 85 mass% or more of acrylonitrile, More preferably, 90 mass% or more is used. As the acrylonitrile-based polymer, a homopolymer or copolymer of acrylonitrile or a mixed polymer thereof can be used. The acrylonitrile copolymer is a copolymerized product of a monomer that can be copolymerized with acrylonitrile and acrylonitrile. Examples of the monomer that can be copolymerized with acrylonitrile include methyl (meth) acrylate and ethyl (meth) acrylate. -(Meth) acrylic acid esters such as propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and vinyl halides such as vinyl chloride, vinyl bromide and vinylidene chloride , Acids such as (meth) acrylic acid, itaconic acid, crotonic acid and their salts, maleic imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, vinyl acetate, and styrene sulfonic acid , Allyl sulfonic acid soda, β-styrene sulfonic acid soda, methallyl sulfonic acid Examples thereof include polymerizable unsaturated monomers containing a sulfone group such as soda, polymerizable unsaturated monomers containing a pyridine group such as 2-vinylpyridine and 2-methyl-5-vinylpyridine, etc. It is not limited to.

  As the polymerization method, conventionally known solution polymerization, suspension polymerization, emulsion polymerization and the like can be applied. As the solvent used in the acrylic polymer solution, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, an aqueous zinc chloride solution, nitric acid, or the like can be used.

  As the spinning method, a wet spinning method, a dry wet spinning method, a dry spinning method, or the like can be employed. The coagulated yarn obtained by spinning is preferably subjected to primary stretching. In primary stretching, the coagulated yarn may be stretched in a coagulation bath or a stretching bath, or may be stretched in the bath after partially stretching in the air. When extending | stretching in a bath, it can carry out by dividing | segmenting into multiple steps of 1 time or 2 times or more normally in a 50-98 degreeC extending | stretching bath. You may perform washing | cleaning before or after that, or simultaneously.

(Granting of oil composition containing silicone compound)
Next, the process of providing the oil agent composition containing the silicone compound to the carbon fiber precursor acrylic fiber bundle as an oil agent for the spinning process will be described. Oil composition containing a silicone-based compound is used as a spinning process oil, providing convergence in the spinning process of the carbon fiber precursor acrylic fiber bundle, imparting flexibility, smoothness and antistatic properties, and converging in the firing process. Is imparted to the carbon fiber precursor acrylic fiber bundle in order to prevent fusion and to prevent fusion.

  In order to uniformly apply the carbon fiber precursor acrylic fiber bundle, it is preferable to apply the oil composition containing the silicone compound to the fiber bundle in a water-swollen state after being stretched and washed in a bath. The method for applying the oil agent composition is not particularly limited, but a method of immersing and attaching the carbon fiber precursor acrylic fiber bundle to the oil agent treatment tank containing the treatment liquid containing the oil agent composition and water is preferable from an industrial viewpoint. .

  The amount of the oil agent composition attached to the carbon fiber precursor acrylic fiber bundle is such that the oil agent composition is attached to the dry fiber bundle in an amount of 0.1 to 3.0% by mass. It is desirable to adjust by adjusting the treatment liquid by squeezing the treatment liquid with a nip roll or the like.

  Examples of the silicone compound used in the present invention include silicone oils such as amino-modified silicone and epoxy-modified silicone, and amino-modified silicone is particularly preferable. Examples of the amino-modified silicone include side-chain primary amino-modified silicone, side-chain 1, secondary amino-modified silicone, and both-end amino-modified silicone.

  The viscosity of the silicone oil is preferably 50 centistokes (hereinafter cSt) or more and 3,000 cSt or less, more preferably 2,000 cSt or less as measured at 25 ° C. If it is 3,000 cSt or less, a solvent having excellent dispersibility in water and / or solubility is present, so that it can be uniformly applied to the fiber surface. In this case, the heat resistance of the oil base is also improved. Moreover, if it is 50 cSt or more, it will not decompose | disassemble and volatilize easily at a flame-proofing process, and the fusion prevention effect between single fibers will not be lost.

  The functional group equivalent (such as amine equivalent or epoxy equivalent) of the silicone oil is preferably 1000 g / mol or more and 10000 g / mol or less, and more preferably 2000 g / mol or more and 8000 g / mol or less. If it is 1000 g / mol or more, the silicone skeleton will not be easily decomposed at a high temperature of 200 ° C. or more, so that the heat resistance is excellent. Moreover, if it is 10,000 g / mol or less, it will not bring about the fall of the strand strength resulting from the physical property of carbon fiber, especially the fusion | melting in a flame-proofing process.

  When the oil composition for the spinning process is used as an aqueous dispersion, a surfactant can be used to uniformly disperse the silicone compound in water into fine particles, for example, a size of 0.1 to several tens of μm. Surfactants include ionic and nonionic types, and ionic types include anionic surfactants, cationic surfactants, and amphoteric surfactants. As the surfactant used in the present invention, a nonionic surfactant that does not contain a metal that becomes a defect formation point in the firing step is preferably used.

  Nonionic surfactants include, for example, higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, and fatty acid amide ethylenes. Examples include oxide adducts, fat and oil ethylene oxide adducts, and polypropylene glycol ethylene oxide adducts. Higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts and polypropylene glycol ethylene oxide adducts are preferred, and polypropylene glycol ethylene oxide adducts are particularly preferred. Is more preferable. The structure of the polypropylene glycol ethylene oxide adduct is preferably a block copolymer type polyether.

  An antioxidant may be added to the oil composition for the purpose of preventing thermal deterioration of the silicone compound in the oil composition. Here, a known antioxidant can be used as the antioxidant. Specifically, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl) -4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris (4-tert-butyl-3-hydroxy-2) , 6-Dimethylbenzyl) isocyanuric acid, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 4,4′-butylidenebis (3-methyl- 6-t-butylphenyl-ditridecyl phosphite) and the like are preferably used, and these may be used alone or in combination.

  The antioxidant is suitably contained in an amount of 1 to 10% by mass based on the total mass of the oil composition for the spinning process. If it is 1% by mass or more, the effect of improving heat resistance is sufficiently obtained, and if it is 10% by mass or less, the emulsification stability of the oil composition is not impaired, and the carbon fiber precursor acrylic fiber bundle. In the firing step, the antioxidant residue does not remain on the carbon fiber. Moreover, if it is about 10 mass%, the heat resistant improvement effect is fully acquired.

  In addition, an antistatic agent, a penetrating agent, an antifoaming agent, a preservative, and the like may be appropriately blended in the oil composition for the spinning process in order to improve the properties of the carbon fiber precursor acrylic fiber bundle and the carbon fiber.

  Next, the fiber bundle provided with the oil agent composition for the spinning process is dried and densified with a heating roller or the like. Although drying temperature and time can be selected as appropriate, it is preferable to dry and densify with a heating roller of 120 to 190 ° C. When the temperature of the heating roller is less than 120 ° C, it is necessary to increase the number of heating rollers, and when the temperature of the heating roller exceeds 190 ° C, fusion between single fibers occurs, and the performance of the carbon fiber decreases. Tend to.

  The fiber bundle obtained by the above-mentioned dry densification is dried because it can be stretched at a high magnification, can further increase the final spinning speed, and contributes to improvement in the density and orientation of the obtained fiber. Heat stretching or steam stretching is preferred. Dry heat drawing may be performed between two hot rolls, or may be performed by bringing a fiber bundle into contact with a hot plate installed between the hot rolls. The steam stretching is preferably performed by a pressurized steam stretching method in which stretching is performed in a pressurized steam atmosphere.

(Granting of oil composition comprising mixture A)
Next, immediately before subjecting the obtained carbon fiber precursor acrylic fiber bundle to flame resistance treatment, 0.1 to 3.0% by mass of an oil agent composition comprising the mixture A is imparted as an oil agent for the flame resistance process. To do.

（式中、Ｒ^１及びＲ^２は、それぞれ独立して炭素数７〜２１のアルキル基であり、Ａ^１及びＡ^２は、それぞれ独立してエチレン基又はプロピレン基であり、ｍ及びｎは、それぞれ独立して１〜５の整数を表す） The oil agent composition comprising the mixture A of the present invention comprises 60 to 90% by mass of the aromatic ester represented by the formula (1), 1 to 10% by mass of the antioxidant, and a residue after heating at 250 ° C. for 2 hours. A nonionic surfactant having a ratio of 1.0% by mass or less is contained in an amount of 9 to 35% by mass.

(Wherein R ¹ and R ² are each independently an alkyl group having 7 to 21 carbon atoms, A ¹ and A ² are each independently an ethylene group or a propylene group, and m and n are Each independently represents an integer from 1 to 5)

The high heat resistance in the flameproofing process of the aromatic ester represented by the formula (1) and the effect of improving the heat resistance of the aromatic ester by the antioxidant can effectively suppress the decrease in convergence of the fiber bundle due to static electricity. it can.
The aromatic ester represented by the formula (1) is almost decomposed in the subsequent pre-carbonization step and does not generate a tar component. Furthermore, a nonionic surfactant having a residue rate of 1.0% by mass or less after heating at 250 ° C. for 2 hours is obtained by finely dispersing an aromatic ester or an antioxidant represented by the formula (1) in water to obtain a carbon fiber. While being able to adhere uniformly to a precursor acrylic fiber bundle, it decomposes | disassembles almost completely in a flame-proofing process, and does not generate | occur | produce a tar component.

  Moreover, the oil agent which consists of mixture A as an oil agent for flameproofing processes immediately before performing a flameproofing to the carbon fiber precursor acrylic fiber bundle which provided the oily agent composition containing a silicone type compound as an oil agent for a spinning process Since the composition is applied, it is difficult to penetrate into the fiber. Therefore, it is possible to improve the convergence property of the fiber bundle in the flameproofing process even if it is not applied excessively, and no defects are generated when it is converted into carbon fibers.

  In addition, the oil agent composition containing the silicone compound and the oil agent composition composed of the mixture A cause the surface of the carbon fiber precursor acrylic fiber bundle to which the silicon compound adheres to the mixture A without causing migration. Since it coats with the oil agent composition which becomes, it can suppress that a silicone type compound volatilizes in an oxidizing atmosphere at a flame-proofing process.

Specifically, the alkyl group having 7 to 21 carbon atoms forming R ¹ part or R ² part of the formula (1) may be selected from higher fatty acids such as lauric acid, myristic acid, palmitic acid and stearic acid. preferable. Moreover, if m and n are within the above-mentioned ranges, the heat resistance and the convergence property of the fiber bundle due to static electricity can be satisfied. When a plurality of A ¹ and A ² are present, an ethylene group and a propylene group may be mixed. In addition, the aromatic ester shown by Formula (1) may be a mixture of a some compound, Therefore, m and n may not be an integer.

  The content rate of the aromatic ester shown by Formula (1) in the mixture A exists in the range of 60-90 mass%. If it is 60% by mass or more, it is possible to obtain the effect of improving the convergence of the flameproofing process, suppressing defects when converted to carbon fiber, and suppressing the volatilization of silicone into the oxidizing atmosphere in the flameproofing process. it can. Moreover, the said aromatic ester can be finely disperse | distributed to water as it is 90 mass% or less, and can be made to adhere uniformly to a carbon fiber precursor acrylic fiber bundle. The range of the content rate is preferably 65 to 80% by mass.

As the antioxidant in the mixture A, a known antioxidant can be used as in the case of the oil composition for the spinning process described above.
The content rate of the antioxidant in the mixture A of this invention exists in the range of 1-10 mass%. If it is 1 mass% or more, the heat resistance improvement effect of the said aromatic ester can be acquired. Moreover, if it is 10 mass% or less, it can prevent that antioxidant remains as a heating residue in a flame-resistant thread | yarn or a carbonized thread | yarn, and stability of an emulsion falls.

  The nonionic surfactant in the mixture A has a residue rate of 1.0% by mass or less after heating at 250 ° C. for 2 hours. Preferable examples include polyoxyalkylene glycol fatty acid esters and alkylene oxide adducts of aliphatic alcohols, and the alkyl chain in the hydrophobic part may be linear or branched. These may be used alone or in combination. The nonionic surfactant preferably has an HLB of 6 to 16. Such nonionic surfactants, for example, the number of repeating hydrophilic oxyalkylene units, the type of oxyalkylene units and the form of repeating oxyalkylene units are such that the aqueous dispersion of mixture A becomes a stable emulsion. It can be selected appropriately.

  The content of the nonionic surfactant in the mixture A of the present invention is in the range of 9 to 35% by mass. If it is 9 mass% or more, stability of an emulsion will fall and the adhesion spot to a carbon fiber precursor acrylic fiber bundle will not arise. Moreover, if it is 35 mass% or less, the convergence improvement of a flameproofing process, the suppression of the defect at the time of converting to carbon fiber, and the effect which suppresses volatilization to the oxidizing atmosphere of a silicone compound can be acquired. it can. The content of the nonionic surfactant is preferably 15 to 30% by mass.

    In addition, an antistatic agent, a penetrating agent, an antifoaming agent, a preservative, and the like are appropriately blended in the oil agent composition comprising the mixture A of the present invention to improve the properties of the carbon fiber precursor acrylic fiber bundle and the carbon fiber. May be.

  Application of the oil composition composed of the mixture A to the carbon fiber precursor acrylic fiber bundle is performed immediately before the carbon fiber precursor acrylic fiber bundle is flameproofed, that is, immediately before being supplied to the flameproofing furnace. As generally used, the method of applying the oil composition is to immerse the carbon fiber precursor acrylic fiber bundle in an oil treatment tank containing a treatment liquid containing the oil composition and water, and attach the oil composition to the oil solution treatment tank. The method is preferable from an industrial viewpoint. At this time, it is preferable to uniformly disperse the oil agent composition in a size of, for example, 0.1 to 0.3 μm in the treatment liquid.

  The amount of the oil agent composition consisting of the mixture A to the carbon fiber precursor acrylic fiber bundle is such that the oil agent composition is contained in an amount of 0.1 to 3.0% by mass with respect to the dry fiber bundle. It is desirable to adjust by adjusting the concentration of the oil composition in squeezing or by squeezing the treatment liquid with a nip roll or the like. Moreover, after giving the oil agent composition which consists of the mixture A, the water contained in a carbon fiber precursor acrylic fiber bundle may be dried using a drying roll etc., and you may flame-proof after that.

(Flame resistance)
After applying the oil agent composition comprising the mixture A, the conditions for obtaining a flame-resistant fiber bundle by flame-treating the carbon fiber precursor acrylic fiber bundle are as follows: tension or stretching in an oxidizing atmosphere at 200 to 300 ° C. Under the conditions, it is preferable to heat until the density of the flameproof fiber after the flameproofing treatment is 1.30 g / cm ³ or more. The oxidizing atmosphere is not particularly limited as long as it contains oxygen, but air is particularly excellent in terms of industrial production and economy and safety. Further, the oxygen concentration in the oxidizing atmosphere can be changed for the purpose of adjusting the oxidation ability.

If the density of the flame-resistant fiber is 1.30 g / cm ³ or more, the progress of flame resistance is sufficient, and the high-temperature heat treatment such as pre-carbonization and carbonization treatment in an inert gas atmosphere to be performed later is performed. No fusing between single yarns.

After performing the flame resistance treatment, when the carbon fiber bundle is obtained by pre-carbonization or carbonization treatment in an inert gas atmosphere, if the density of the flame resistant fiber is 1.40 g / cm ³ or less, Since excessive oxygen is not introduced into the flameproof fiber, the final internal structure of the carbon fiber becomes dense, and a carbon fiber with excellent performance can be obtained.
On the other hand, when the flame-resistant fiber bundle is processed and further baked at a high temperature to produce a product for heat resistance, the density of the flame-resistant fiber bundle may exceed 1.40 g / cm ³ . If the density of the flameproofing fiber is 1.50 g / cm ³ or less, the time required for the flameproofing treatment will not be prolonged.

As a heating method and a furnace structure in the flameproofing treatment, a hot air circulation method, a fixed hot plate method having a perforated plate surface, or the like can be used, but other methods are also applicable.
The hot air circulation type flameproofing furnace is generally used in the industrial production of the flameproofing process, and this is achieved by spraying an oxidizing gas heated in the hot air circulation system to heat oxygen and heat into thousands of filaments. Can be uniformly supplied, heat generated by the oxidation reaction can be efficiently removed, and a stable flameproofing reaction can proceed.

(Carbonization)
The flameproof fiber bundle obtained by the flameproofing treatment is carbonized by heating in an inert atmosphere. Carbonization can be pre-carbonized under tension in an inert atmosphere having a maximum temperature of 550 to 800 ° C., and then carbonized in an inert atmosphere at 1200 to 3000 ° C.
Here, in the temperature range of 300 to 500 ° C. of the pre-carbonization and in the temperature range of 1000 to 1200 ° C. of the carbonization, the heating rate is 500 ° C./min or less, preferably 300 ° C./min or less. It is preferable.

  Nitrogen, argon, helium, etc. can be adopted for the inert atmosphere, but nitrogen is desirable from the viewpoint of economy.

  The carbon fiber bundle or graphitized fiber bundle thus obtained is subjected to an electrolytic oxidation treatment in a conventionally known electrolytic solution, or an oxidation treatment in a gas phase or a liquid phase, so that the carbon fiber in the composite material It is preferable to improve the affinity and adhesiveness with the matrix resin. Furthermore, a sizing agent can be applied by a conventionally known method as necessary.

  Hereinafter, the present invention will be described more specifically with reference to examples.

<Nonionic surfactant heated residue>
A nonionic surfactant 2.0 g is precisely weighed in an aluminum petri dish (diameter 60 mm, depth 10 mm), and the residue after heating at 250 ° C. in air for 2 hours is precisely weighed to calculate the residue rate.

<Amount of silicone compound contained in carbon fiber precursor acrylic fiber bundle and flameproof fiber bundle (amount of Si contained)>
The measurement sample is uniformly wound in the horizontal direction on an acrylic resin plate having a length of 2 cm, a width of 4 cm, and a width of 0.5 cm so that there is no gap. At this time, the winding length of the fiber bundle is the same. Thereafter, the fluorescent X-ray intensity is measured by a fluorescent X-ray analysis method. Considering the adhesion spot of the oil agent on the fiber bundle or measurement error, the number of measurements is set to n = 100 for one measurement sample, and the average value is obtained.
Value obtained by calculating by the following formula (2), assuming that the amount of silicone contained in the carbon fiber precursor acrylic fiber bundle (fluorescent X-ray intensity: unit cps) is A ₁ and the amount of Si contained in the flame-resistant fiber bundle is A _2. Is defined as “Si residual ratio”.
“Si residual ratio (%)” = A ₂ / A ₁ × 100 (2)
In addition, Rigaku Denki / Model ZSX was used for the measurement of fluorescent X-ray intensity.

<Measurement of moisture content of carbon fiber precursor acrylic fiber bundle>
The fiber bundle is dried at 105 ° C. for 1.5 hours, the mass before and after drying is measured (mass W ₁ before drying, mass W ₂ after drying), and the “water content” is calculated according to the following formula (3). .
“Moisture content (%)” = (W ₁ −W ₂ ) / W ₂ × 100 (3)

<Adhesion amount of oil agent composition of carbon fiber precursor acrylic fiber bundle>
The amount of oil composition adhering to the carbon fiber precursor acrylic fiber bundle after application of the oil composition was measured by a Soxhlet extraction method using methyl ethyl ketone. The extraction time was 1 hour.

<Resin impregnated strand characteristics>
The strand characteristics (strength, elastic modulus) of the carbon fiber are physical properties of the epoxy resin-impregnated strand measured according to JIS-R-7601, and are obtained from the average of the number of measurements n = 10.

<Preparation of treatment liquid for oil composition>
The oil composition for the spinning process is a mixture of a base agent (base oil), an antioxidant, and a nonionic surfactant (polyoxyethylene stearyl ether [EO (ethylene oxide): 12 mol, HLB: 13.9]). A process in which the oil agent composition is dispersed in water by adding ion-exchanged water, emulsifying with a homomixer, and adjusting the pressure with a high-pressure homogenizer so that the emulsified particle size is about 0.3 μm and performing secondary emulsification. Obtain a liquid.
The oil agent composition for the flameproofing process consists of a base agent (base oil), an antioxidant, a nonionic surfactant (polyoxyethylene lauryl ether [EO (ethylene oxide) unit number: 10, HLB: 14.0, heated residue ( Ion-exchanged water is added to a mixture obtained by mixing at 250 ° C. for 2 hours): 0.4 mass%, emulsified with a homomixer, and further pressurized with a high-pressure homogenizer so that the emulsion particle size is about 0.2 μm. And a secondary emulsification is performed to obtain a treatment liquid in which the oil composition is dispersed in water.

<Manufacture of carbon fiber precursor acrylic fiber bundle>
An acrylonitrile copolymer is dissolved in dimethylacetamide so as to have a copolymer concentration of 21% by mass to obtain a spinning dope. This spinning dope is discharged into a dimethylacetamide aqueous solution having a concentration of 70% by mass and a temperature of 35 ° C. using a 12,000-hole nozzle to perform wet spinning. Next, the coagulated fiber is stretched 1.5 times in the air, washed and desolvated while being stretched 3 times in boiling water.
Then, after immersing the coagulated yarn in an oil agent treatment tank containing an aqueous dispersion of the oil agent composition for the spinning process shown in Table 1 (Example 1), and attaching the spinning process oil, a heating roller at 140 ° C. Was dried and densified with, and stretched 3 times in pressurized steam to obtain a carbon fiber precursor acrylic fiber bundle having a single fiber fineness of 1.2 dtex. The amount of Si (fluorescent X-ray intensity: unit cps) contained in the carbon fiber precursor acrylic fiber bundle provided with the spinning process oil was 5762 cps.

<Manufacture of flame-resistant fiber bundle>
Then, after immersing the carbon fiber precursor acrylic fiber bundle in the oil agent treatment tank containing the aqueous dispersion of the flameproofing process oil agent shown in Table 1 (Example 1), and applying the flameproofing process oil agent, treatment with a nip roll A liquid squeezing step (hereinafter referred to as nip treatment) was passed through and immediately heated in air at 230 to 260 ° C. under tension to obtain a flame-resistant fiber bundle having a density of 1.35 g / cm ³ . The amount of Si contained in the flame-resistant fiber bundle (fluorescent X-ray intensity: unit cps) was 5097 cps. Moreover, Si residual rate calculated by Formula (2) was 88.5%.

<Manufacture of carbon fiber bundles>
The obtained flame-resistant fiber bundle was pre-carbonized by heating under tension at 700 ° C. in a nitrogen atmosphere. The heating rate at 300 to 500 ° C. in the pre-carbonization treatment was 200 ° C./min.
Subsequently, it heated under tension at 1300 degreeC in nitrogen atmosphere, and was set as the carbonized fiber bundle. The rate of temperature increase at 1000 to 1200 ° C. in this carbonization treatment was 400 ° C./min.

  The obtained carbonized fiber bundle was subjected to surface treatment, and then a sizing agent was applied to obtain a carbon fiber bundle. During the firing step, almost no single fiber breakage or fluffing was observed. The strand characteristics of the obtained carbon fiber bundle are shown in Table 1 together with other measured values (the moisture content of the fiber bundle, the amount of Si contained, etc.).

<Examples 2 to 6>
With the composition shown in Table 1, the oil agent composition for the spinning process and the oil agent composition for flame resistance were applied. Other than that, a carbon fiber bundle was produced and evaluated in the same manner as in Example 1.
In either case, almost no single fiber breakage or fluff was observed during the firing process. The strand characteristics of the obtained carbon fiber bundle are shown in Table 1 together with other measured values (the moisture content of the fiber bundle, the amount of Si contained, etc.).

<Examples 7 to 8>
In the same manner as in Example 1, except that the oil composition for the spinning process and the oil composition for flame resistance were applied under the conditions shown in Table 1, and the drying treatment with a hot roll was performed after the nip treatment. Carbon fiber bundles were manufactured and evaluated. In either case, almost no single fiber breakage or fluff was observed during the firing process.
The strand characteristics of the obtained carbon fiber bundle are shown in Table 1 together with other measured values (the moisture content of the fiber bundle, the amount of Si contained, etc.).

<Comparative Examples 1-4>
A carbon fiber bundle was produced and evaluated in the same manner as in Example 1 except that the spinning process oil application conditions were as shown in Table 1 and the flameproofing process oil was not applied.
In Comparative Examples 1 to 3, the convergence property of the fiber bundle in the firing process is lower than that of the example, and fluff and bundle breakage are observed, and the quality of the obtained carbon fiber bundle is also inferior to that of the example. It was. In Comparative Example 4, the convergence property of the fiber bundle during the firing process was equivalent to that of the example, but the quality of the obtained carbon fiber bundle was inferior to that of the example.

<Comparative Examples 5-10>
Under the conditions shown in Table 1, spinning process oil application and flameproofing process oil application were performed. Other than that, a carbon fiber bundle was produced and evaluated in the same manner as in Example 1.
In Comparative Examples 5 to 8, the convergence property of the fiber bundle in the firing process is lower than that of the Example, and fluff and bundle breakage are observed, and the quality of the obtained carbon fiber is also inferior to that of the Example. . In Comparative Examples 9 to 10, the convergence property of the fiber bundle during the firing process was equivalent to that of the example, but the quality of the obtained carbon fiber was inferior to that of the example.

In addition, about each component (main agent, additive, surfactant) of spinning process oil agent and flameproofing process oil agent of Table 1,
Component A (base oil)
Both end amino-modified silicone (viscosity at 25 ° C. 450 cSt, amino equivalent 5700),
Component B (base oil)
Side chain 1, secondary amino-modified silicone (viscosity at 25 ° C. 250 cSt, amino equivalent 5200),
Component C (base oil)
Side chain primary amino-modified silicone (viscosity at 25 ° C. 110 cSt, amino equivalent 5000),
Component D (base oil)
Dilauryl ester of bisphenol A ethylene oxide 2 mol adduct. m = 1, n = 1,
Component E (base oil)
Dilauryl ester of ethylene oxide 4 mol adduct of bisphenol A. m = 2, n = 2,
Component F (base oil)
Dilauryl ester of bisphenol A ethylene oxide 12 mole adduct. m = 6, n = 6,
Component G (base oil)
Polybutene, average molecular weight of about 1350,
Component H (antioxidant)
Pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate],
Component I (surfactant)
Polyoxyethylene stearyl ether [EO (ethylene oxide): 12 mol, HLB: 13.9, heating residue (mass after heating at 250 ° C./2 hours): 8.0 mass%],
Component J (surfactant)
Polyoxyethylene lauryl ether [EO (ethylene oxide) unit number: 10, HLB: 14.0, heating residue (mass after heating at 250 ° C./2 hours): 0.4 mass%],
Component K (surfactant)
Polyoxyethylene hydrogenated castor oil [number of EO units: 10, HLB: 12.5, heating residue (mass after heating at 250 ° C./2 hours): 15% by mass],
It is.

Claims (1)

An oil agent composition containing a silicone compound is applied to the carbon fiber precursor acrylic fiber bundle in an amount of 0.1 to 3.0% by mass per fiber mass of the carbon fiber precursor acrylic fiber bundle, and then immediately before the flameproofing treatment. Furthermore, the manufacturing method of the flame-resistant fiber bundle which provides the oil agent composition which consists of mixture A 0.1-3.0 mass% per fiber mass, and heats in 200-300 degreeC oxidizing atmosphere.
Mixture A:
Nonionic interface having an aromatic ester represented by the following (1) of 60 to 90% by mass, an antioxidant of 1 to 10% by mass, and a residue ratio after heating at 250 ° C. for 2 hours of 1.0% by mass or less. Contains 9-35% by weight of activator.

(Wherein R ¹ and R ² are each independently an alkyl group having 7 to 21 carbon atoms, A ¹ and A ² are each independently an ethylene group or a propylene group, and m and n are Each independently represents an integer from 1 to 5)