JP2016160560A - Method for manufacturing carbon fiber bundle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon fiber bundle excellent in physical properties and quality, which suppresses generation of fuzzes of the fiber bundle, and breakage of the fiber bundle by applying a flame resistance-modifying process oil solution composition separately at a plurality of times to a carbon fiber precursor acrylic fiber bundle before and on a way of flame resistance treatment.SOLUTION: The method for manufacturing a carbon fiber bundle includes introducing a carbon fiber precursor acrylic fiber bundle into not less than two flame resistance-modifying furnaces disposed in series and capable of independently controlling temperature, and heat-treating at 200°C-300°C in an oxidation atmosphere. In between the two flame resistance-modifying furnaces, a flame resistance-modifying process oil solution composition is applied to the fiber bundle on a way of flame resistance-modifying obtained by heat-treating the precursor fiber bundle in a primary stage flame resistance-modifying furnace, and thereafter the fiber bundle is heat-treated in a secondary stage flame resistance-modifying furnace.SELECTED DRAWING: None

Description

  The present invention relates to a production method for stably producing high-quality carbon fibers.

  As a method of producing a carbon fiber bundle using a carbon fiber precursor acrylic fiber bundle (hereinafter abbreviated as “precursor fiber bundle”), a fiber bundle in which thousands to tens of thousands of acrylic fibers are bundled. Is heated in an oxidizing atmosphere at 200 to 300 ° C. (hereinafter referred to as “flame-proofing treatment”) to obtain a flame-resistant fiber bundle, and then heat-treated in an inert gas atmosphere at 300 to 1000 ° C. (Hereinafter, referred to as “pre-carbonization treatment”) and then a heat treatment (hereinafter referred to as “carbonization treatment”) in an inert gas atmosphere at 1000 ° C. or higher is known.

  The flameproofing treatment is an oxidation reaction accompanied by heat generation, and it is necessary to perform heat treatment at a relatively low temperature of 200 to 300 ° C. for a long time so that the reaction heat is accumulated in the fiber bundle and the fiber bundle is not ignited. In a heat treatment apparatus (hereinafter referred to as a “flame-proofing furnace”) that performs a flame-proofing process in order to perform a long-time heat treatment, both ends of the flame-proofing furnace are passed so that the precursor fiber bundle repeatedly passes through the flame-proofing furnace. In general, a plurality of folding rollers are arranged.

  Due to the temperature at the time of the flameproofing treatment and the large amount of heat generated by the oxidation reaction, fusion easily occurs between the single fibers of the flameproofed fiber. When the flame-resistant fiber bundle in which the fusion has occurred is subsequently carbonized, the obtained carbon fiber has problems such as generation of fuzz and yarn breakage.

  In addition, when the convergence and smoothness (scratch resistance) of the precursor fiber bundle are insufficient, a single yarn is wound around the folding rollers disposed at both ends of the flameproofing furnace, or the fiber bundle is in contact with or rubbed. Problems such as fiber breakage occur.

  In order to solve the above-mentioned problems, it is known that an oil agent to be applied to the precursor fiber bundle (hereinafter, an oil agent to be applied at the production stage of the precursor fiber bundle is referred to as “spinning process oil agent”) is important. Many oil agents have been studied.

  Among them, since it has high heat resistance, fiber fusion can be effectively suppressed, and good fiber bundle convergence and smoothness (scratch resistance) can be obtained. Is often used.

  Further, after the flameproofing step, an oil agent is further applied to further improve the convergence and smoothness of the fiber bundle (hereinafter, the oil agent applied in the flameproofing step of the precursor fiber bundle is referred to as “flameproofing step oil agent”). (Patent Document 2 and Patent Document 3).

  A part of the spinning process oil and the flameproofing process oil are volatilized during the flameproofing process, and it is known that the initial volatilization amount is particularly large in the flameproofing process. Therefore, in order to efficiently perform the flameproofing process from the initial stage to the latter stage of the flameproofing process, a certain amount of spinning process oil and flameproofing process oil (hereinafter collectively referred to as “oil”) are added to the precursor fiber bundle. It is necessary to give above. However, if the applied amount of the oil agent is too large, sticking between fibers due to the oil agent composition tends to occur. When the sticking occurs, the oxidizing gas cannot enter the vicinity of the center portion of the fiber bundle, so that the fibers in the vicinity of the center portion are not sufficiently flame-resistant and cause flame-resistant spots. In the carbonization treatment performed after the flameproofing treatment, the yarn breakage, the partial cut of the fiber bundle, or the total cut (hereinafter collectively referred to as “bundle cut”) A), and further, the strength of the carbon fiber is reduced.

  As means for improving the performance of carbon fibers, it has been proposed to make the surface wrinkle structure of the single fibers constituting the carbon fiber bundle shallow and smooth, or to make the cross-sectional shape of the single fibers close to a perfect circle (patent) Reference 4). However, as the cross-sectional shape of the single fiber approaches a perfect circle, the convergence property of the fiber bundle becomes stronger, so that the problem of the above-mentioned sticking becomes remarkable, and the problem of the above-mentioned oil agent bundle breakage becomes more remarkable. When the bundle breaks, it often leads to production stop, and as a result, the oil agent, particularly the flameproofing process oil agent, cannot be applied in an amount capable of maximizing the original effect.

JP-A 61-146817 Japanese Patent Laid-Open No. 2008-190056 JP 2013-060680 A JP 2010-285710 A

  In the flameproofing treatment of the carbon fiber precursor acrylic fiber bundle, the present invention provides a flameproofing process oil agent by giving the flameproofing process oil composition in a plurality of times, while avoiding troubles derived from the flameproofing process oil. To provide a method for producing flame-resistant fibers and carbon fibers that maximizes the effect of imparting the composition, significantly improves operability and processability in the flame-proofing process, and at the same time has excellent physical properties and quality. Objective.

  The present invention relates to a method for producing a carbon fiber bundle, wherein the carbon fiber precursor acrylic fiber bundle is introduced into two or more flameproofing furnaces installed in series capable of independent temperature control, and an oxidizing atmosphere. A method for producing a carbon fiber bundle, comprising heat treatment at 200 ° C. to 300 ° C. below, between two flameproofing furnaces arranged in series, and a carbon fiber precursor acrylic in a preceding flameproofing furnace It relates to a method for producing a carbon fiber bundle, characterized by applying a flameproofing step oil agent composition to a flameproof fiber bundle obtained by heat-treating the fiber bundle, and then heat-treating in a subsequent flameproof furnace. .

Furthermore, the manufacturing method of this invention can be made into the conditions of following (1)-(4).
(1) Immediately before the carbon fiber precursor acrylic fiber bundle is first introduced into the flameproofing furnace, the flameproofing process oil agent composition is applied to the fiber bundle.
(2) A spinning process oil composition containing a silicone compound is applied to the carbon fiber precursor acrylic fiber bundle.
(3) A flameproofing step oil agent composition is applied to the carbon fiber precursor acrylic fiber bundle or the flameproof fiber bundle, and then the moisture content of the fiber bundle is set to 1.0% or less, followed by flameproofing treatment.
(4) The average unevenness Ra of the carbon fiber precursor acrylic fiber bundle is 5 nm or more and 70 nm or less, and the major axis dL and minor axis dS of the fiber cross section perpendicular to the fiber axis of the single fiber constituting the fiber bundle, Ratio (dL / dS) is 1.05 or more and 1.50 or less.

  According to the present invention, it becomes possible to efficiently impart a flameproofing oil composition to the fiber, the operability and processability of the flameproofing treatment are remarkably improved, and at the same time, the flameproofing fiber bundle is excellent in physical properties and quality. And a carbon fiber bundle can be manufactured stably.

  The present invention is described in detail below.

  The carbon fiber precursor acrylic fiber bundle is obtained 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.

The acrylonitrile-based polymer is preferably a polymer containing acrylonitrile units of 85% by mass or more, more preferably 90% by mass or more.
As the acrylonitrile-based polymer, a homopolymer or copolymer of acrylonitrile or a mixed polymer of these polymers 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, ethyl (meta ) (Meth) acrylates such as acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, halogens such as vinyl chloride, vinyl bromide, vinylidene chloride Acids such as vinyl chloride, (meth) acrylic acid, itaconic acid, crotonic acid and their salts, maleic acid imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, vinyl acetate, styrenesulfonic acid -Sodium, allylsulfonic acid soda, beta-styrenesulfonic acid soda, methallylsulfonic 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.

  The obtained acrylonitrile-based polymer is dissolved in dimethyl sulfoxide, dimethylacetamide, dimethylformamide, an aqueous zinc chloride solution, nitric acid, etc., and discharged into a coagulating liquid through a spinneret to obtain a coagulated yarn. As a spinning method for obtaining a coagulated yarn, a wet spinning method, a dry wet spinning method, a dry spinning method, or the like can be employed.

  Next, the obtained coagulated yarn is subjected to drawing treatment. At this time, the coagulated yarn may be stretched in a coagulation bath or a stretching bath, or may be partially stretched in the air and then stretched in the bath. Stretching in the bath is usually performed in a stretching bath at 50 to 98 ° C. by dividing it into multiple stages of once or twice, and washing may be performed before or after or simultaneously.

  In this spinning process, if an oil agent is added to the carbon fiber precursor acrylic fiber bundle (precursor fiber bundle), the convergence, flexibility and smoothness of the precursor fiber bundle in the spinning process can be improved, and charging can be prevented. Can do.

  Spinning process for fiber bundles in a water-swelled state after stretching in a bath and washing in order to uniformly apply the oil composition applied in the spinning process (hereinafter abbreviated as “spinning process oil agent”) to the fiber bundle. It is preferable to apply an oil agent.

  There are no particular limitations on the method of applying the spinning process oil, and any known method can be used. A method of immersing the carbon fiber precursor acrylic fiber bundle in an oil agent treatment tank containing a treatment liquid in which an oil agent is dispersed in water and attaching the oil agent is preferable from an industrial viewpoint.

  The coagulated yarn to which the spinning process oil is adhered is dried and densified using, for example, a heating roller. 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. If the temperature of the heating roller is 120 ° C. or higher, there is no need to increase the number of heating rollers, and if the temperature of the heating roller is 190 ° C. or less, no fusion occurs between the single fibers, and carbon The fiber performance is not deteriorated.

  Since it is possible to stretch at a high magnification, it is possible to increase the final spinning speed, and contribute to improving the density and orientation of the resulting fiber, the acrylic fiber bundle obtained by the above-mentioned dry densification, Furthermore, you may perform a dry heat extending | stretching process or a steam extending | stretching process. The dry heat stretching treatment may be performed between two hot rolls, or may be performed by bringing the fibers 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.

  The precursor fiber bundle thus obtained is further provided with a flameproofing process oil agent composition for the purpose of improving the convergence of the fiber bundle and preventing fusion between the fibers during the flameproofing treatment (hereinafter referred to as “flameproofing”). Chemical process oil ”. .

  At this time, by including a silicone compound in at least one of the spinning process oil and the flameproofing process oil, the process passability in the firing process performed after the flameproofing process is improved, and the fiber is treated during the carbonization process. Fusion can be prevented.

Examples of combinations of the spinning process oil and the flameproofing process oil include the following three. The following “silicone compound-containing oil agent” refers to an oil agent containing a silicone compound.
(1) Spinning process oil: Silicone compound-containing oil / flame resistance process oil: Silicone compound-containing oil (2) Spinning process oil: silicone compound-containing oil / flame resistance process oil: Oil containing no silicone compound (3 ) Spinning process oil: Oil containing no silicone compound / Flame resistance process oil: Silicone compound-containing oil In the case of (1), for example, in the spinning process oil, the fiber bundle is prevented from being wound around the roll or between single fibers. Use a silicone-based oil suitable for preventing fusion, etc., and use a silicone-based compound suitable for maintaining the convergence of the fiber bundle as the flameproofing process. be able to. In the case of (2) and (3), the amount of the silicone compound applied to the acrylic fiber bundle can be reduced, and the amount of fine powder derived from the silicone compound can be reduced.

  Examples of the silicone compound used in the oil 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 primary and secondary amino-modified silicone, and both-end amino-modified silicone.

  The viscosity of the silicone compound (measured at 25 ° C.) is preferably 50 centistokes (cSt) or more and 3,000 cSt or less, more preferably 2,000 cSt or less. If it is 3,000 cSt or less, it can be uniformly applied to the surface of the fiber without causing problems in dispersibility in water or solubility. Moreover, if it is 50 cSt or more, the oil agent in the flameproofing process can efficiently prevent fusion between single fibers without being decomposed and volatilized.

  The functional group equivalent (amine equivalent, epoxy equivalent, etc.) of the silicone compound is preferably 1000 g / mol or more and 10,000 g / mol or less, more preferably 2000 g / mol or more and 7000 g / mol or less. If it is 1000 g / mol or more, the silicone skeleton will not be decomposed in the flameproofing step. Moreover, if it is 10000 g / mol or less, it can suppress the physical property fall of carbon fiber, such as the fall of the strand strength of the carbon fiber finally obtained resulting from the fusion | melting between fibers in a process during a flame-proofing process. .

  Examples of the oil component other than the silicone compound include a reaction product obtained by converting a alkylene oxide adduct of bisphenol A into a monoalkyl ester and further reacting with a saturated aliphatic dicarboxylic acid, or a dibasic acid and an oxyalkylene unit. It is possible to use an adduct having a terminal amide group obtained by reacting an aliphatic alkanolamide with a polyol condensate, an alkylene oxide adduct of an amide compound obtained by reacting a polyamine and a fatty acid, or the like.

  In addition, heat resistance is impaired when an ester compound is used that has a mass residual rate of 5% by mass or less when heated at 700 ° C. for 5 minutes in an inert atmosphere after heat treatment at 250 ° C. in air for 2 hours. It is preferable because there is no

When using an oil agent in which an oil agent component is dispersed in water, a known method may be used.
For example, a surfactant can be used to uniformly disperse the oil component in water as particles having 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.

  Nonionic surfactants are preferred because they do not contain a metal that is the starting point for the formation of defects in the fiber during carbonization. Specific examples of nonionic surfactants include 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, Examples include fatty acid amide ethylene oxide adducts, fat and oil ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, and polypropylene glycol ethylene oxide adducts. Oxide adducts are more preferred.

  The structure of the polypropylene glycol ethylene oxide adduct is preferably a block copolymer type polyether.

  In order to prevent thermal deterioration of the ester compound in the oil agent, an antioxidant may be used. Specific examples of the antioxidant include 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-t-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris (4-t-butyl) -3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 4,4'- Butylidenebis (3-methyl-6-tert-butylphenyl-ditridecyl phosphite) and the like, as well as combinations thereof.

  The content of the antioxidant in the oil is preferably in the range of 1 to 10% by mass. If it is 1% by mass or more, the effect of preventing thermal deterioration of the ester compound is sufficiently obtained, and if it is 10% by mass or less, the oxidation derived from the precursor fiber bundle is carried out without impairing the emulsion stability of the oil agent. The residue of the inhibitor does not remain on the carbon fiber.

  In addition, an antistatic agent, a penetrating agent, an antifoaming agent, an antiseptic, and the like can be appropriately blended with the spinning process oil and the flameproofing process oil to improve the properties of the precursor fiber bundle and the carbon fiber.

  The application amount of the spinning process oil agent is preferably 0.1 to 3.0% by mass of the oil agent with respect to the dried fiber bundle. The application amount of the spinning process oil can be adjusted, for example, by adjusting the concentration of the oil in the treatment liquid in which the oil is dispersed in water, or by adjusting the squeezing of the liquid using a nip roll or the like.

  In the present invention, the application of the flameproofing process oil is performed in multiple steps. There is no restriction | limiting in particular in the frequency | count of providing a flame-resistant oil agent. Flameproofing process From the viewpoint of narrowing the installation space of the oiling equipment and the drying equipment described later, the flameproofing process is divided into 2 to 4 sections, and each section is provided with oiling equipment and flameproofing. It is sufficient if the process oil can be applied.

As a specific operation, the flame resistance process oil can be applied using the density range of the fiber bundle during flame resistance as a guide. For example, a normal carbon fiber precursor acrylic fiber bundle has a density of about 1.18 g / cm ³ and a flame-resistant fiber bundle has a density of about 1.36 g / cm ^3. When the flameproofing process oil is applied only once, the flameproofing process oil may be applied when the density of the fiber bundle is about 1.27 g / cm ³ during the flameproofing. In addition, when the flameproofing process oil agent is applied to the fiber bundle in the middle of flameproofing only twice, the flameproofing process oil has a density of the fiber bundle in the middle of flameproofing of around 1.24 g / cm ^{3 and} around 1.30 g / cm ^3. Can be given. The position where the equipment to which the flameproofing process oil is applied is not particularly limited. Immediately before the precursor fiber bundle is introduced into the flameproofing furnace or the flameproofing process is divided into 2 to 4 sections, and an oil agent application facility can be installed in each section.

  When applying the flameproofing process oil in multiple times, it is sufficient that the amount of oil applied each time is sufficient to maintain the effect of applying the oil during the flameproofing process until the next oil application. It is. Specifically, depending on the length of the flameproofing treatment time until the next oil agent application, the oil agent application amount is determined, or the oil agent application amount is determined in consideration of the occurrence of yarn breakage or fiber bundle breakage. You may do it. Specifically, although it depends on the number of times the oil agent is applied, the application amount with respect to the fiber bundle before the oil agent application can be adjusted in a range of 0.02 to 1.0 mass%.

  After the carbon fiber precursor acrylic fiber bundle or the flame resistant fiber bundle is immersed in the aqueous dispersion of the flameproofing process oil, the excess aqueous dispersion can be removed by squeezing the fiber bundle with a nip roll or the like. However, even after the aqueous dispersion is squeezed, the fiber bundle contains a large amount of water.

  It is very important to remove moisture contained in the fiber bundle before supplying the carbon fiber precursor acrylic fiber bundle or the flame-proofing fiber bundle to the flame-proofing furnace.

  The reason is not clear, but when the flame retardant treatment is performed on the precursor fiber bundle to which the silicone-based oil agent is applied, the amount of fine powder derived from the silicone-based oil agent when the fiber side is subjected to the flame resistance treatment in a state containing a large amount of moisture. Tend to increase.

  In addition, since the fiber bundle in the middle of flame resistance easily absorbs water inside the fiber bundle, the strength of the carbon fiber bundle finally obtained is greatly reduced when the fiber bundle is subjected to flame resistance treatment in a state containing water.

  Therefore, the moisture content of the precursor fiber bundle just before being introduced into the flameproofing furnace and the moisture content of the flameproofing fiber bundle being reintroduced into the flameproofing furnace are both preferably less than 1.5% by mass. More preferably, the content is not more than 0.0% by mass. By setting the moisture content in the fiber bundle to less than 1.5% by mass, the generation of the fine powder described above can be effectively suppressed, and the strength reduction of the finally obtained carbon fiber bundle can be prevented.

  The treatment temperature at the time of drying the moisture is preferably set to a temperature at which the flame resistance reaction of the precursor fiber bundle does not occur, specifically, the fiber bundle using a drying roll adjusted to a temperature range of 140 to 210 ° C. Can be dried.

The flameproofing treatment is carried out by oxidizing at a temperature of 200 to 300 ° C. in an oxidizing atmosphere, heating the fiber bundle while tensioning or stretching, and the density of the flameproofing fiber after the flameproofing treatment is 1.30 g / cm ³ or more 1 Heating may be performed in a range of 50 g / cm ³ or less. As the heating method and the structure of the flameproofing furnace when the fiber bundle is flameproofed, a hot air circulation method, a fixed hot plate method having a porous plate surface, or the like can be used.

  The flame-resistant fiber bundle thus obtained is then pre-carbonized and carbonized under an inert gas atmosphere to obtain a carbon fiber bundle. As pre-carbonization conditions, the maximum temperature is in the range of 550 to 800 ° C., and the fiber bundle is tensioned in an inert atmosphere, and in the temperature range of 300 to 500 ° C., 500 ° C. / In order to improve the mechanical properties of the carbon fiber, it is effective to pre-carbonize the flame-resistant fiber bundle at a temperature rising rate of 300 ° C./min or less.

  The carbonization condition of the pre-carbonized fiber bundle is carbonization treatment at a temperature rising rate of 500 ° C./min or less, preferably 300 ° C./min or less in a temperature range of 1000 to 1200 ° C. in an inert atmosphere of 1200 to 3000 ° C. It is effective to improve the mechanical properties of the carbon fiber. A known inert gas such as nitrogen, argon or helium can be used for the inert atmosphere of the pre-carbonization treatment and the carbonization treatment, and nitrogen is desirable from the viewpoint of economy.

  The obtained carbon fiber bundle is subjected to an electrolytic oxidation treatment in an electrolytic solution, or an oxidation treatment in a gas phase or a liquid phase, so that the affinity between the carbon fiber and the matrix resin when made into a carbon fiber resin composite material And the adhesiveness can be improved. After the treatment, a sizing agent can be added as necessary.

  In the production examples, examples, and comparative examples, the following spinning process oils and flameproofing process oils were used.

[Spinning process oil A]
-Side chain 1, secondary amino-modified silicone (viscosity 250cSt at 25 ° C, amino equivalent 7600) 52 parts by mass-Pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionate] 2 parts by mass-polyoxyethylene stearyl ether [EO (ethylene oxide): 12 mol, HLB: 13.9] 40 parts by mass of deionized water was added to a mixture of 6 parts by mass (total 60 parts by mass). First emulsification with a homomixer. Subsequently, the pressure was adjusted using a high-pressure homogenizer, and secondary emulsification was performed so that the emulsified particle size was about 0.3 μm, and a spinning process oil was obtained.

[Flameproofing process oil B]
-In 190 degreeC under a p-toluenesulfonic acid catalyst, 1.1 mol of polyoxyethylene (2 mol) addition bisphenol A monolaurate is added to 1 mol of adipic acid, and an ester compound is obtained.
Next, 48 parts by mass of a compound obtained by adding polyoxyethylene (10 mol) -added stearylaminoether (1 mol) to the ester compound. Pentaerythrityl-tetrakis [3- (3,5-di-t-butyl -4-hydroxyphenyl) propionate] 2 parts by mass polyoxyethylene stearyl ether [EO (ethylene oxide): 12 mol, HLB: 13.9] 10 parts by mass (total 60 parts by mass) mixed with deionized water (40 parts by mass) was added and primary emulsification was performed with a homomixer. Subsequently, the pressure was adjusted using a high-pressure homogenizer, and secondary emulsification was performed so that the emulsified particle size was about 0.3 μm, and a flameproofing process oil was obtained.

<Average unevenness Ra of the fiber surface>
For the single fiber constituting the carbon fiber precursor acrylic fiber bundle, the average unevenness Ra of the fiber surface is measured by acquiring and analyzing two 3D images under the following conditions using a nanosearch laser microscope. It was. A 3D image was obtained for 5 single fibers per sample, the unevenness Ra was determined for each image, and the average value was taken as the average unevenness Ra of the sample.
[Measurement conditions of 3D image of fiber surface]
Measuring device: Nanosearch laser microscope (product name: LEXT OLS3500, manufactured by Olympus Corporation),
Probe: Cantilever (Product name: OMCL-AC240TS-C2, manufactured by Olympus Corporation)
Measurement environment: performed in air at room temperature.
Scanning range (circumferential direction × fiber axis direction): 600 nm × 600 nm Scanning condition: Measurement was performed by scanning (scanning) the fiber surface with a laser in a direction perpendicular to the fiber axis direction of the fiber sample to be measured. The scanning speed was 1.0 Hz, and the number of pixels was 512 × 512.

[3D image analysis conditions]
Under the above conditions, one 3D image was obtained for one single fiber. Using the image analysis software, the acquired 3D image of the fiber surface was converted from a curved surface image to a planar image (planar fitting correction). With respect to the planar image, a cross-sectional profile in a direction perpendicular to the fiber axis was measured, surface roughness analysis was performed, and an average unevenness Ra was obtained.

<Long diameter / short diameter ratio (dL / dS) of fiber cross section of single fiber>
Measurement was performed by the following method using a scanning electron microscope (SEM). After passing a carbon fiber bundle for measurement through a tube made of a vinyl chloride resin having an inner diameter of 1 mm, a sample is prepared by cutting the tube with a knife so that a fiber bundle having a length of about 10 mm can be obtained. Next, the sample was adhered to the SEM sample stage with the fiber cross section facing upward, and Au was sputtered to a thickness of about 10 nm, and then a scanning electron microscope (product name: XL20, manufactured by Philips) was used. The fiber cross section was observed under conditions of an acceleration voltage of 7.00 kV and a working distance of 31 mm. The major axis dL and minor axis dS of the fiber cross section of the single fiber were measured, and dL / dS was calculated.

<Moisture content of fiber bundle>
The fiber bundle cut into a predetermined length is dried at 105 ° C. for 1.5 hours, and the weight W1 (g) before drying and the weight W2 (g) after drying are measured to the last three digits, respectively, according to the following calculation formula (2) The water content was measured.
Moisture content (%) = (W1−W2) / W2 × 100 (2)

<Amount of spinning process oil A>
The carbon fiber precursor acrylic fiber bundle was measured by a Soxhlet extraction method (hereinafter abbreviated as “extraction”) using methyl ethyl ketone. The extraction time was 1 hour. The mass W3 (g) of the fiber bundle before extraction and the mass W4 (g) of the fiber bundle after extraction were measured to the last three digits, respectively, and the amount of the spinning process oil agent was measured by the following formula (3).
Spinning process oil amount (%) = (W3−W4) / W4 × 100 (3)

<Applied amount of flameproofing process oil B>
Carbon fiber precursor acrylic fiber bundle, fiber bundle mass W5 (g) after applying flameproofing process oil agent to fiber bundle during flameproofing ~ drying treatment, mass W6 of fiber bundle before applying the flameproofing process oil agent (G) was measured to the last 3 digits, and the adhesion amount of the flameproofing process oil agent was measured by the following calculation formula (4). In the case of applying the flameproofing process oil agent in two or more times, the adhesion amount was measured for each application process.

Amount of adhesion of flameproofing process oil (%) = (W5−W6) / W6 × 100 (4)
<Appearance of fiber bundle>
Flame proofing fiber bundle after treatment in flame proofing furnace 1, flame proof fiber bundle after treatment in flame proofing furnace 2, carbonization furnace (first carbonization furnace and second carbonization furnace) The generation of fluff was observed for the carbon fiber bundle). The obtained fiber bundle was illuminated with an LED light, the number of fluff observed per 10 m length of the fiber bundle was measured, and evaluated in the following three stages (◎, ○, Δ). When a bundle of fiber bundles was broken during the treatment, it was marked as x.
A: The number of fluff is 0-5.

○: The number of fluff is 6 to 15 Δ: The number of fluff is 16 or more ×: Fiber bundle is broken <Strand strength of carbon fiber bundle>
Preparation of strand test pieces of resin-impregnated carbon fiber bundles and measurement of strength were measured and evaluated according to JIS R7601. The measurement was performed with the number of measurements n = 10, and the average value was calculated.

[Production example]
Production Example 1 shows a carbon fiber acrylic precursor fiber bundle af1, and Production Example 2 shows a production example of a carbon fiber acrylic precursor fiber bundle af2.

[Production Example 1]
Acrylonitrile, acrylamide and methacrylic acid are put into water and copolymerized by aqueous suspension polymerization in the presence of ammonium persulfate-ammonium hydrogen sulfite and iron sulfate, and acrylonitrile unit / acrylamide unit / methacrylic acid unit = 97/2/1 ( An acrylonitrile polymer consisting of (mass ratio) was obtained. This acrylonitrile-based polymer was dissolved in dimethylacetamide to prepare a spinning dope with a solid concentration of 21% by mass.

  From the spinneret having a discharge hole having a diameter of 50 μm and a hole number of 30,000, the spinning solution is discharged into a coagulation liquid filled with a 67% by mass dimethylacetamide aqueous solution adjusted to 38 ° C. to solidify the coagulated yarn. Obtained. Next, the coagulated yarn was passed through a five-stage stretch washing tank whose temperature was set in the range of 60 to 98 ° C., and a total 2.6 times stretching treatment and washing treatment were simultaneously performed. Next, the spinning process oil agent A mainly composed of the above-mentioned amino-modified silicone was applied to the fiber bundle so as to be 1.1% by mass with respect to 100% by mass of the fiber bundle, and then a dry densification treatment was performed. The fiber bundle after the drying densification treatment was stretched 3.5 times under steam at a temperature of about 150 ° C. Next, after applying deionized water to the fiber bundle after plasticizing and drawing with a touch roll, the fiber bundle was supplied to the entanglement applying device and entangled, and then wound on a bobbin. The obtained carbon fiber acrylic precursor fiber bundle (af1) had a single fiber fineness of 1.0 dtex, an average unevenness Ra of 15.0 nm, and a long fiber / long diameter ratio (dL / dS) of a single fiber of 1.17. It was.

[Production Example 2]
The spinning dope prepared in Production Example 1 was discharged from a spinneret having a discharge diameter of 75 μm in diameter and 24,000 holes into a coagulating liquid filled with a 67% by mass dimethylacetamide aqueous solution adjusted to 38 ° C. And coagulated to obtain a coagulated yarn. Next, the coagulated yarn was passed through a 5-stage drawing / washing tank whose temperature was set in the range of 60 to 98 ° C., and a total of 3.2 times of drawing and washing were simultaneously performed. Next, the spinning process oil A described above was applied to the fiber bundle so as to be 1.1% by mass with respect to 100% by mass of the fiber bundle, and dry densification treatment was performed. The fiber bundle after the dry densification treatment was stretched 2.6 times under steam at a temperature of about 150 ° C. Next, after applying deionized water with a touch roll to the fiber bundle after plasticizing and stretching, it was wound around a bobbin after being entangled by the same method as in Production Example 1. The obtained carbon fiber acrylic precursor fiber bundle (af2) has a single fiber fineness of 1.2 dtex and an average roughness Ra of 31.0 nm, and the long / short diameter ratio (dL / dS) of the fiber cross section of the single fiber is 1.18. there were.

[Example 1]
After immersing the precursor fiber bundle af1 in the oil treatment tank containing the aqueous dispersion of the above-mentioned flameproofing process oil B, a liquid squeezing process (hereinafter referred to as a nip process) by a nip roll is performed, and then a heating roller at 150 ° C. By applying the drying treatment, the first application of the flameproofing process oil was performed. The application amount of the flameproofing process oil agent B to the precursor fiber bundle was 0.03% by mass, and the moisture content of the precursor fiber bundle after drying treatment with a heating roller was 0.28%.

The carbon fiber precursor acrylic fiber bundle af1 provided with this flameproofing process oil B is introduced into the flameproofing furnace 1, and air heated to 230 to 240 ° C. is sprayed onto the precursor fiber bundle af1, and the density is 1.27 g. A fiber bundle of1-1 having a flame resistance of / cm ³ was obtained. The elongation rate during the flameproofing treatment was -3.0%, and the treatment time was 40 minutes.

  Next, the flameproofing process fiber bundle of1-1 was introduced into the flameproofing furnace 2, and the second application of the flameproofing process oil B was performed in the same manner as the method of applying the first flameproofing process oil B. . The amount of flameproofing process oil B applied to the flameproofing process fiber bundle of1-1 is 0.03% by mass, and the moisture content of the flameproofing fiber bundle of1-1 after being dried by a heating roller is 0. 32%.

Further, this flameproofing fiber bundle of1-1 is introduced into a flameproofing furnace, and air heated to 250 to 260 ° C. is blown onto the flameproofing fiber bundle of1-1, thereby obtaining a density of 1.35 g / cm ^3. The flame-resistant fiber bundle of1-2 was obtained. The elongation rate during the flameproofing treatment was -3.0%, and the treatment time was 40 minutes.

  Next, the flame-resistant fiber bundle of1-2 was pre-carbonized by passing through a first carbonization furnace having a temperature gradient of 300 to 700 ° C. in a nitrogen atmosphere while applying an extension of + 3.0%. The temperature change in the first carbonization furnace was set to increase linearly, and the treatment time was 1.3 minutes. Next, a second carbonization furnace having a temperature gradient of 1000 to 1600 ° C. in a nitrogen atmosphere was passed through under the condition of an elongation rate of −4.5% for carbonization treatment. The processing time was 1.3 minutes. In this second carbonization furnace, the rate of temperature increase between 1000 ° C. and 1200 ° C. was 400 ° C./min.

  Next, surface treatment was performed, and a sizing agent was further applied to obtain a carbon fiber bundle. The fiber bundles, flame resistant fiber bundles, and carbonized fiber bundles in the course of flameproofing showed almost no single fiber breakage or fluffing, and no significant reduction in strength was observed.

[Examples 2-3]
Flame resistance in the same manner as in Example 1 except that the application amount of the first and second flameproofing process oil B and the moisture content of the fiber bundle after applying the oil and drying treatment were as shown in Table 1. (On the way) fiber bundles and carbonized fiber bundles were produced. The evaluation results are shown in Table 1. In the fiber bundle, single fiber breakage and fluff were hardly observed, and no significant reduction in strength was observed.

[Examples 4 to 6]
Flame-resistant (on the way) fiber bundle and carbonized fiber bundle in the same manner as in Example 1 except that the flame-proofing process oil B was applied under the conditions shown in Table 1 using the carbon fiber precursor acrylic fiber bundle af2. Manufactured. The evaluation results are shown in Table 1. In the fiber bundle, almost no single fiber breakage or fluff was observed, and no significant strength reduction was observed between Examples 4-6.

[Comparative Example 1]
Flameproofing (on the way) fiber bundles and carbonized fiber bundles are manufactured in the same manner as in Example 1 except that the application of the oil resistance B is not performed (the drying treatment is not performed). did. The evaluation is shown in Table 1. Compared with the Examples, the convergence of the fiber bundle was lowered, and fuzz was scattered. The quality of the carbon fiber bundle was inferior to the carbon fiber bundle of the example.

[Comparative Example 2]
Flameproofing (on the way) fiber bundles and carbonized fiber bundles were produced in the same manner as in Example 1 except that the second flameproofing process oil B was not applied. The evaluation results are shown in Table 1. Fluff was scattered after the second flameproofing treatment (flameproofing furnace 2), and the quality of the carbon fiber bundle was inferior to the carbon fiber bundle of the example.

[Comparative Example 3]
A flame-resistant (on the way) fiber bundle and a carbonized fiber bundle were produced in the same manner as in Example 1 except that the application amount of the first flame-resistant step oil B was changed to the conditions shown in Table 1. The evaluation results are shown in Table 1. Fluff did not occur in the first and second flameproofing treatments (flameproofing furnaces 1 and 2), but the occurrence of bundle breakage was observed after the carbonization treatment. The quality of the carbon fiber bundle was inferior to that of the carbon fiber bundle of the example, and the strand strength was greatly reduced.

[Comparative Example 4]
Flame-resistant (on the way) fiber bundles and carbonized fiber bundles are produced in the same manner as in Example 1 except that after the first and second flame-proofing process oil agent B is applied, the drying treatment with a heating roll is not performed. did. The evaluation results are shown in Table 1. Fluff did not occur in the first and second flameproofing treatments (flameproofing furnaces 1 and 2), but the occurrence of bundle breakage was observed after the carbonization treatment. The quality of the carbon fiber bundle was inferior to that of the carbon fiber bundle obtained in the examples, and the strand strength was greatly reduced.

  Here, in Comparative Example 4, since the flameproofing treatment was performed without performing the drying treatment with the heating roll after the application of the flameproofing process oil, the fiber bundle immediately after the flameproofing process oil was applied and the nip treatment was performed. The moisture content was defined as the moisture content of the fiber bundle before flame resistance.

[Comparative Example 5]
Flame resistant (on the way) fiber bundles and carbonized fiber bundles were produced in the same manner as in Example 4 except that the second flame resistant step oil agent B was not applied. The evaluation results are shown in Table 1. The convergence property of the fiber bundle was lower than that of the example, and some fluff was observed. The quality of the obtained carbon fiber bundle was slightly inferior to the carbon fiber bundle of Example 4.

[Comparative Example 6]
Flameproofing (on the way) fiber bundles and carbonized fiber bundles are manufactured in the same manner as in Example 4 except that the first and second flameproofing step oil agent B is not applied (no drying treatment is applied). did. The evaluation results are shown in Table 1. The convergence property of the fiber bundle was greatly reduced as compared with the example, and a lot of fluff was generated, and the occurrence of bundle breakage was observed after the carbonization treatment. The quality of the carbon fiber bundle was greatly inferior to the carbon fiber bundle of Example 4, and the decrease in strand strength was also reduced.

Claims (5)

Including introducing a carbon fiber precursor acrylic fiber bundle into two or more flameproofing furnaces installed in series capable of independent temperature control and heat-treating at 200 ° C. to 300 ° C. in an oxidizing atmosphere, A method of manufacturing a carbon fiber bundle,
Between the two flameproofing furnaces arranged in series, the flameproofing fiber bundle obtained by heat-treating the carbon fiber precursor acrylic fiber bundle in the preceding flameproofing furnace out of the two flameproofing furnaces. The method for producing a carbon fiber bundle is characterized in that after applying the flameproofing process oil composition, heat treatment is performed in a subsequent flameproofing furnace out of the two flameproofing furnaces. The manufacturing method of the carbon fiber bundle of Claim 1 which satisfy | fills following (1).
(1) Immediately before the carbon fiber precursor acrylic fiber bundle is first introduced into the flameproofing furnace, the flameproofing step oil agent composition is applied to the fiber bundle. The manufacturing method of the carbon fiber bundle of Claim 1 or 2 which satisfy | fills following (2).
(2) The spinning process oil composition containing the silicone compound is applied to the carbon fiber precursor acrylic fiber bundle before the application of the flameproofing process oil composition. The manufacturing method of the carbon fiber bundle as described in any one of Claims 1-3 which satisfy | fills following (3).
(3) Applying the flameproofing step oil agent composition to the carbon fiber precursor acrylic fiber bundle or flameproofing fiber bundle, and then setting the moisture content of the fiber bundle to 1.0% or less, followed by flameproofing treatment To do. The manufacturing method of the carbon fiber bundle as described in any one of Claims 1-4 which satisfy | fills following (4) (5).
(4) The average unevenness Ra of the carbon fiber precursor acrylic fiber bundle is 5 nm or more and 70 nm or less.
(5) The ratio (dL / dS) of the major axis dL and minor axis dS of the fiber cross section in the direction perpendicular to the fiber axis of the single fiber constituting the carbon fiber precursor acrylic fiber bundle is 1.05 or more and 1.50. Less than.