Treatment agent for carbon fiber precursor and use thereof

Abstract

The purpose of the present invention is to provide: a treatment agent for a carbon fiber precursor, with which fusion between fibers can be stably suppressed in a flameproofing treatment process; a carbon fiber precursor using the treatment agent; and a method for producing a carbon fiber using the carbon fiber precursor.　A treatment agent for a carbon fiber precursor according to the present invention contains a wax (A) and a surfactant (B). In the treatment agent for a carbon fiber precursor, the melting point of the wax (A) is preferably 50-140°C. In the treatment agent for a carbon fiber precursor, the content ratio of the wax (A) to the nonvolatile content in the treatment agent is preferably 20-95% by weight.

Description

Treatment agent for carbon fiber precursor and its use

[0001] The present invention relates to a treating agent for carbon fiber precursors and uses thereof. More specifically, the present invention relates to a treating agent used in producing a carbon fiber precursor, a carbon fiber precursor (hereinafter sometimes referred to as a precursor) using the treating agent, and a method for producing a carbon fiber using the carbon fiber precursor.

[0002] Taking advantage of their excellent mechanical properties, carbon fibers are widely used as reinforcing fibers for composite materials with plastics known as matrix resins in aerospace, sports, general industrial, and other applications. A common method for producing carbon fibers involves converting a precursor into a flame-resistant fiber in an oxidizing atmosphere at 200-300°C, followed by carbonization in an inert atmosphere at 300-2000°C. These high-temperature firing processes can cause fusion between individual fibers, resulting in a deterioration in the quality and grade of the resulting carbon fiber. To prevent this fusion, numerous techniques have been proposed and widely used industrially: The precursor is treated with a silicone-based treatment agent, which has excellent heat resistance and excellent releasability due to interfiber smoothness. In particular, an amino-modified silicone-based treatment agent, which can further improve heat resistance through a crosslinking reaction, is added to the precursor.

[0003] However, the silicone-based treatment agent adhered to the fibers tends to fall off and become sticky, which can accumulate on drying rollers and guides during the precursor production process, causing problems such as fiber curling and breakage, resulting in reduced operability. Furthermore, some of the silicone-based treatment agent forms silicon oxide in the oxidizing atmosphere of the flame-proofing process, and silicon nitride in the inert atmosphere of the carbonization process when nitrogen is used as an inert gas. These scales accumulate, resulting in problems such as reduced operability and operational efficiency and damage to the firing furnace. Furthermore, while the excellent release properties of silicone-based treatment agents, due to their fiber-to-fiber smoothness, are effective in preventing fusion between individual fibers, in the firing process, where a large number of fiber bundles run parallel to one another, the smoothness of the silicone-based treatment agent can widen the width of each fiber bundle, narrowing the spacing between adjacent fiber bundles and potentially causing fuzz due to interference. To avoid these problems, treatment agents with reduced silicone compound content or treatment agents that do not use silicone-based compounds have been proposed. For example, there are treatment agents that combine an aromatic compound with an amino-modified silicone, and treatment agents that contain an aromatic ester as the main component (see Patent Documents 1 and 2).

[0004] Japanese Patent Publication No. 2001-172879 Japanese Patent Publication No. 2002-129481

[0005] However, although these treating agents have a certain degree of operability, they are not satisfactory because their anti-fusing properties are uneven and partial fusion occurs in some cases. An object of the present invention is to provide a treating agent for carbon fiber precursors that can stably suppress fusion between fibers in the flame-resistant treatment step, a carbon fiber precursor using the treating agent, and a method for producing carbon fibers using the carbon fiber precursor.

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a carbon fiber precursor treatment agent containing a wax (A) and a surfactant (B) can solve the above-mentioned problems, and have arrived at the present invention.

[0007] That is, the present invention includes the following embodiments. <1> A treatment agent for carbon fiber precursors, comprising a wax (A) and a surfactant (B). <2> The treatment agent for carbon fiber precursors according to <1>, wherein the wax (A) has a melting point of 50 to 140°C. <3> The treatment agent for carbon fiber precursors according to <1> or <2>, wherein the wax (A) accounts for 20 to 95 wt% of the non-volatile content of the treatment agent. <4> The treatment agent for carbon fiber precursors according to any one of <1> to <3>, wherein the wax (A) comprises at least one wax selected from animal waxes, plant waxes, polyolefin waxes, paraffin waxes, microcrystalline waxes, and Fischer-Tropsch waxes. <5> The treatment agent for carbon fiber precursors according to any one of <1> to <4>, wherein the surfactant (B) comprises a surfactant having a hydrocarbon group having 6 to 40 carbon atoms. <6> A carbon fiber precursor to which the treatment agent for carbon fiber precursors according to any one of <1> to <5> adheres. <7> A method for producing a carbon fiber, comprising: a flame-resistant treatment step of converting the carbon fiber precursor according to <6> into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C; and a carbonization treatment step of further carbonizing the flame-resistant fiber in an inert atmosphere at 300 to 2000°C.

[0008] The treating agent for carbon fiber precursors of the present invention can stably suppress inter-fiber fusion in the flame-resistant treatment process of a carbon fiber precursor when a carbon fiber precursor produced by applying the treating agent is used. The carbon fiber precursor of the present invention can stably suppress inter-fiber fusion in the flame-resistant treatment process. According to the carbon fiber production method of the present invention, inter-fiber fusion in the flame-resistant treatment process can be stably suppressed, and high-quality carbon fiber can be obtained.

[0009] Each component of the treating agent for carbon fiber precursors of the present invention (hereinafter sometimes simply referred to as the treating agent) will be described. [Wax (A)] The treating agent of the present invention contains wax (A). Wax (A) is an organic substance that is solid at room temperature and becomes liquid when heated. In order to achieve both sizing and anti-fusing properties, the melting point of wax (A) is preferably 50 to 140°C. The upper limit of the melting point is more preferably 135°C, even more preferably 130°C, and particularly preferably 120°C. On the other hand, the lower limit of the melting point is more preferably 53°C, even more preferably 55°C, and particularly preferably 60°C. Furthermore, for example, 53 to 135°C is more preferable, and 55 to 130°C is even more preferable. Examples of wax (A) include animal waxes, vegetable waxes, polyolefin waxes, paraffin waxes, microcrystalline waxes, and Fischer-Tropsch waxes. In order to achieve both sizing and anti-fusing properties, the wax (A) preferably contains at least one selected from animal waxes, vegetable waxes, polyolefin waxes, paraffin waxes, microcrystalline waxes, and Fischer-Tropsch waxes, more preferably at least one selected from vegetable waxes, polyolefin waxes, and paraffin waxes, even more preferably at least one selected from vegetable waxes and paraffin waxes, and particularly preferably paraffin waxes. One or more types of wax (A) may be used in combination.

[0010] Examples of animal waxes include beeswax, lanolin, and spermaceti. Examples of plant waxes include carnauba wax, candelilla wax, rice wax, Japan wax, and jojoba oil. Examples of polyolefin waxes include polyethylene wax, oxidized polyethylene wax, acid-modified polyethylene wax, polypropylene wax, oxidized polypropylene wax, acid-modified polypropylene wax, polybutylene wax, oxidized polybutylene wax, acid-modified polybutylene wax, ethylene-acrylic acid copolymer wax, ethylene-vinyl acetate copolymer wax, acid-modified ethylene-vinyl acetate copolymer wax, ethylene-maleic anhydride copolymer wax, and propylene-maleic anhydride copolymer wax. Examples of paraffin waxes include waxes containing normal paraffin as the main component. Examples of microcrystalline waxes include waxes containing isoparaffin as the main component. Among these waxes, in terms of achieving both sizing and anti-fusing properties, it is preferable to include at least one selected from beeswax, carnauba wax, candelilla wax, rice wax, oxidized polyethylene wax, acid-modified polyethylene wax, oxidized polypropylene wax, acid-modified polypropylene wax, and normal paraffin, it is more preferable to include at least one selected from carnauba wax, candelilla wax, oxidized polyethylene wax, acid-modified polyethylene wax, and normal paraffin, and it is particularly preferable to include normal paraffin.

[0011] [Surfactant (B)] The treatment agent of the present invention contains a surfactant (B). The surfactant (B) is not particularly limited, but examples include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant (B) preferably contains at least one selected from nonionic surfactants and anionic surfactants, and more preferably contains a nonionic surfactant, in order to uniformly impart anti-fusing properties. The surfactant (B) preferably contains a surfactant having a hydrocarbon group containing 6 to 40 carbon atoms, in order to uniformly impart anti-fusing properties. The upper limit of the carbon number is more preferably 35, even more preferably 30, and particularly preferably 20. Meanwhile, the lower limit of the carbon number is more preferably 8, even more preferably 10, and particularly preferably 12. Furthermore, for example, a range of 8 to 35 is more preferable, and a range of 10 to 30 is even more preferable.

[0012] Nonionic surfactants include polyoxyalkylene linear alkyl ethers such as polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene tetradecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene behenyl ether; polyoxyalkylene branched primary alkyl ethers such as polyoxyethylene 2-ethylhexyl ether, polyoxyethylene isocetyl ether, and polyoxyethylene isostearyl ether; polyoxyethylene 1-hexylhexyl ether, polyoxyethylene 1-octylhexyl ether, polyoxyethylene 1-hexyloctyl ether, polyoxyethylene 1-pentylheptyl ether, polyoxyethylene 1-heptylpentyl ether, and polyoxyethylene polyoxyalkylene secondary alkyl ethers such as polyoxyethylene 1-hexylheptyl ether, polyoxyethylene 1-heptylhexyl ether, polyoxyethylene 1-pentylcaptyl ether, and polyoxyethylene 1-captylpentyl ether; polyoxyalkylene alkenyl ethers such as polyoxyethylene oleyl ether; polyoxyalkylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, and polyoxyethylene dodecylphenyl ether; polyoxyalkylene alkylarylphenyl ethers such as polyoxyethylene tristyrylphenyl ether, polyoxyethylene distyrylphenyl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene tribenzylphenyl ether, polyoxyethylene dibenzylphenyl ether, and polyoxyethylene benzylphenyl ether; acetylene surfactants in which alkylene oxide is added to acetylene alcohol or acetylenic diol;Polyoxyalkylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monooleate, polyoxyethylene monostearate, polyoxyethylene monomyristate, polyoxyethylene dilaurate, polyoxyethylene diolate, polyoxyethylene dimyristate, and polyoxyethylene distearate; sorbitan esters such as sorbitan monopalmitate, sorbitan monooleate, sorbitan distearate, and sorbitan tristearate; polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan monooleate Examples include alkylene sorbitan fatty acid esters; glycerin fatty acid esters such as glycerin monostearate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmitate, glycerin distearate, and glycerin tristearate; polyoxyalkylene sorbitol fatty acid esters; sucrose fatty acid esters; polyoxyalkylene castor oil ethers such as polyoxyethylene castor oil ether; polyoxyalkylene hydrogenated castor oil ethers such as polyoxyethylene hydrogenated castor oil ether; oxyethylene-oxypropylene block or random copolymers; and oxyethylene-oxypropylene block or random copolymers with terminal sucrose ethers.

[0013] Among these, in terms of being able to uniformly impart anti-fusing properties, it is preferable to include at least one selected from polyoxyalkylene linear primary alkyl ethers, polyoxyalkylene linear secondary alkyl ethers, polyoxyalkylene branched primary alkyl ethers, polyoxyalkylene branched secondary alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene alkylaryl phenyl ethers, and acetylene surfactants, and it is preferable to include at least one selected from polyoxyalkylene linear primary alkyl ethers, polyoxyalkylene linear secondary alkyl ethers, polyoxyalkylene branched primary alkyl ethers, and polyoxyalkylene branched secondary alkyl ethers. In terms of emulsifying properties and penetrating properties, the number of carbon atoms in these alkyl groups is preferably 12 or more, more preferably 18 or more. Meanwhile, the upper limit of the alkyl group is preferably 30, and even more preferably 25. The alkyl group preferably has a carbon number of 12 to 30, more preferably 18 to 25. It is preferable that the alkyl group has a linear structure. The weight average molecular weight of the nonionic surfactant is preferably 2000 or less, more preferably 200 to 1800, more preferably 300 to 1500, and even more preferably 500 to 1000. One or more types of nonionic surfactants may be used.

[0014] Examples of anionic surfactants include fatty acids (salts) such as stearic acid, arachidic acid, behenic acid, lignoceric acid, oleic acid, palmitic acid, sodium oleate, potassium palmitate, and triethanolamine oleate; hydroxyl group-containing carboxylic acids (salts) such as hydroxyacetic acid, potassium hydroxyacetate, lactic acid, and potassium lactate; polyoxyalkylene alkyl ether acetic acids (salts) such as polyoxyethylene tridecyl ether acetic acid (sodium salt); salts of carboxyl group-polysubstituted aromatic compounds such as potassium trimellitate and potassium pyromellitate; alkylbenzene sulfonic acids (salts) such as dodecylbenzene sulfonic acid (sodium salt); polyoxyalkylene alkyl ether sulfonic acids (salts) such as polyoxyethylene 2-ethylhexyl ether sulfonic acid (potassium salt); higher fatty acid amide sulfonic acids (salts) such as stearoyl methyl taurine (sodium), lauroyl methyl taurine (sodium), myristoyl methyl taurine (sodium), and palmitoyl methyl taurine (sodium); lauroyl sal N-acyl sarcosinic acid (salts) such as cosinic acid (sodium); alkyl phosphonic acids (salts) such as octyl phosphonate (potassium salt); aromatic phosphonic acids (salts) such as phenyl phosphonate (potassium salt); alkyl phosphonic acid alkyl phosphate esters (salts) such as 2-ethylhexyl phosphonate mono 2-ethylhexyl ester (potassium salt); nitrogen-containing alkyl phosphonic acids (salts) such as aminoethyl phosphonic acid (diethanolamine salt); alkyl sulfate esters (salts) such as 2-ethylhexyl sulfate (sodium salt); Polyoxyalkylene sulfate esters (salts) such as polyoxyethylene 2-ethylhexyl ether sulfate (sodium salt); alkyl phosphate esters (salts) such as lauryl phosphate (potassium salt), cetyl phosphate (potassium salt), stearyl phosphate (diethanolamine salt); polyoxyalkylene alkyl (alkenyl) ether phosphate esters (salts) such as polyoxyethylene lauryl ether phosphate (potassium salt), polyoxyethylene oleyl ether phosphate (triethanolamine salt);Examples include polyoxyalkylene alkylphenyl ether phosphate esters (salts) such as polyoxyethylene nonylphenyl ether phosphate (potassium salt) and polyoxyethylene dodecylphenyl ether phosphate (potassium salt); long-chain sulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate and sodium dioctyl sulfosuccinate; and long-chain N-acyl glutamates such as sodium monosodium N-lauroyl glutamate and disodium N-stearoyl-L-glutamate.

[0015] Among these, in terms of being able to uniformly impart anti-fusing properties, it is preferable to include at least one selected from polyoxyalkylene alkyl ether acetic acid (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), alkylbenzene sulfonic acid (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), and alkyl phosphate ester (salt), and it is also preferable to include at least one selected from polyoxyalkylene alkyl ether acetic acid (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), and alkyl phosphate ester (salt). In terms of emulsifying properties and penetrating properties, the number of carbon atoms in these alkyl groups is preferably 12 or more, more preferably 18 or more. Meanwhile, the upper limit of the alkyl group is preferably 30, and even more preferably 25. For example, the alkyl group is preferably 12 to 30, more preferably 18 to 25.

[0016] Examples of cationic surfactants include alkyl quaternary ammonium salts such as lauryl trimethyl ammonium chloride, myristyl trimethyl ammonium chloride, palmityl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, oleyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, behenyl trimethyl ammonium chloride, coconut oil alkyl trimethyl ammonium chloride, beef tallow alkyl trimethyl ammonium chloride, stearyl trimethyl ammonium bromide, coconut oil alkyl trimethyl ammonium bromide, cetyl trimethyl ammonium methosulfate, oleyl dimethyl ethyl ammonium ethosulfate, dioctyl dimethyl ammonium chloride, dilauryl dimethyl ammonium chloride, distearyl dimethyl ammonium chloride, and octadecyl diethyl methyl ammonium sulfate; (polyoxyethylene) lauryl amino ether lactate, stearyl amino ether lactate, and di(polyoxyethylene) lauryl methyl amino ether. (Polyoxyalkylene) alkylamino ether salts such as ether dimethyl phosphate, di(polyoxyethylene) lauryl ethyl ammonium ethosulfate, di(polyoxyethylene) hardened beef tallow alkylethylamine ethosulfate, di(polyoxyethylene) lauryl methyl ammonium dimethyl phosphate, di(polyoxyethylene) stearylamine lactate; acylamidoalkyl quaternary ammonium salts such as N-(2-hydroxyethyl)-N,N-dimethyl-N-stearoylamidopropyl ammonium nitrate, lanolin fatty acid amidopropyl ethyl dimethyl ammonium ethosulfate, lauroylamidoethyl methyl diethyl ammonium methosulfate; alkylethenoxy quaternary ammonium salts such as dipalmityl polyethenoxyethyl ammonium chloride, distearyl polyethenoxymethyl ammonium chloride; alkylisoquinolinium salts such as lauryl isoquinolinium chloride; benzalkonium salts such as lauryl dimethyl benzyl ammonium chloride, stearyl dimethyl benzyl ammonium chloride;benzethonium salts such as benzyldimethyl{2-[2-(p-1,1,3,3-tetramethylbutylphenoxy)ethoxy]ethyl}ammonium chloride; pyridinium salts such as cetylpyridinium chloride; imidazolinium salts such as oleylhydroxyethylimidazolinium ethosulfate and laurylhydroxyethylimidazolinium ethosulfate; acyl basic amino acid alkyl ester salts such as N-cocoylarginine ethyl ester pyrrolidone carboxylate and N-lauroyllysine ethyl ester chloride; primary amine salts such as laurylamine chloride, stearylamine bromide, hardened beef tallow alkylamine chloride and rosinamine acetate; cetylmethylamine sulfate secondary amine salts such as dilauryl methylamine sulfate, lauryl methylamine chloride, dilaurylamine acetate, stearyl ethylamine bromide, lauryl propylamine acetate, dioctylamine chloride, and octadecylethylamine hydroxide; tertiary amine salts such as dilauryl methylamine sulfate, lauryl diethylamine chloride, lauryl ethyl methylamine bromide, diethanol stearyl amidoethylamine trihydroxyethyl phosphate salt, and stearyl amidoethylethanolamine urea polycondensate acetate salt; fatty acid amide guanidinium salts; and alkyl trialkylene glycol ammonium salts such as lauryl triethylene glycol ammonium hydroxide.

[0017] Examples of amphoteric surfactants include imidazoline-based amphoteric surfactants such as 2-undecyl-N,N-(hydroxyethylcarboxymethyl)-2-imidazoline sodium and 2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt; betaine-based amphoteric surfactants such as 2-heptadecyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, lauryl dimethylaminoacetic acid betaine, alkyl betaine, amido betaine, and sulfobetaine; and amino acid-based amphoteric surfactants such as N-lauryl glycine, N-lauryl β-alanine, and N-stearyl β-alanine.

[0018] (Modified Silicone Having a Nitrogen-Atom-Containing Modifying Group) The carbon fiber precursor treating agent of the present invention may further contain a modified silicone having a nitrogen-atom-containing modifying group in order to provide excellent fiber-to-fiber smoothness. The type of modified silicone having a nitrogen-atom-containing modifying group is not particularly limited, as long as it is a nitrogen-atom-containing modifying group. Examples of the nitrogen-atom-containing modifying group include a modifying group containing an amino bond or an imino bond (e.g., an amino group), and a modifying group containing an amide bond (e.g., an amide group). A modifying group containing a plurality of different bonds, such as an amino bond and an amide bond, may also be used. The nitrogen-atom-containing modifying group preferably contains at least one selected from an amino group, an amide group, and a nitro group, and more preferably an amino group, in order to provide excellent emulsion stability when emulsified in an aqueous system and to achieve excellent effects when used in combination with wax (A). The nitrogen-atom-containing modifying group may be bonded to a side chain of the silicone main chain, to a terminal, or to both. Furthermore, the polymer may have a polyoxyalkylene group (for example, a polyoxyethylene group, a polyoxypropylene group, a polyoxybutylene group, etc.) in the molecule.

[0019] Examples of modified silicones having a modifying group containing a nitrogen atom include amino-modified silicones, aminopolyether-modified silicones, amide-modified silicones, and amidepolyether-modified silicones, and at least one selected from amino-modified silicones and amide-modified silicones is preferred, with amino-modified silicones being more preferred, in that they provide excellent emulsion stability when emulsified in an aqueous system and are effective when used in combination with wax (A).As the modified silicone having a modifying group containing a nitrogen atom, one type of modified silicone may be used, or multiple modified silicones may be used in combination.

[0020] Furthermore, the nitrogen atom content in the modified silicone having a nitrogen atom-containing modifying group is preferably 0.35 to 3.2 wt %, in terms of excellent emulsion stability when emulsified in an aqueous system and excellent effects of the present invention when used in combination with wax (A). The upper limit of this content is more preferably 2.2 wt %, and even more preferably 1.3 wt %. Meanwhile, the lower limit of this content is more preferably 0.37 wt %, and even more preferably 0.40 wt %. Furthermore, for example, 0.37 to 2.2 wt % is more preferable, and 0.40 to 1.3 wt % is even more preferable.

[0021] When the modified silicone having a modifying group containing a nitrogen atom contains an amino-modified silicone, the structure of the amino-modified silicone is not particularly limited. That is, the amino group, which is the modifying group, may be bonded to a side chain of the silicone main chain, or to an end, or may be bonded to both. Furthermore, the amino group may be a monoamine type or a polyamine type, and both may coexist in one molecule.

[0022] The amino group content in the amino-modified silicone (hereinafter referred to as "amino weight %") is preferably 0.4 to 3.7 weight % in terms of excellent emulsion stability when emulsified in an aqueous system and excellent effects of the present application when used in combination with wax (A). The upper limit of this content is more preferably 2.5 weight %, and even more preferably 1.5 weight %. Meanwhile, the lower limit of this content is more preferably 0.42 weight %, and even more preferably 0.46 weight %. Furthermore, for example, 0.42 to 2.5 weight % is more preferable, and 0.46 to 1.5 weight % is even more preferable.

[0023] The kinematic viscosity at 25°C of the modified silicone having a modifying group containing a nitrogen atom is not particularly limited, but in terms of emulsion stability and uniform application to fibers, it is preferably 100 to 15,000 mm ２ The upper limit of the kinematic viscosity is preferably 10,000 mm ２ / s is more preferable, and 5,000 mm ２ On the other hand, the lower limit of the kinematic viscosity is 500 mm ２ / s is more preferable, and 1,000 mm ２ / s is more preferable.２ / s is more preferable, and 1,000 to 5,000 mm ２ / s is more preferred.

[0024] [Treatment Agent for Carbon Fiber Precursors] The treatment agent for carbon fiber precursors of the present invention contains wax (A) and surfactant (B). It is believed that the inclusion of wax (A) and surfactant (B) in the treatment agent enables stable suppression of interfiber fusion during the flame-retardant treatment process because surfactant (B) uniformly and evenly adheres wax (A) to the fibers, thereby stably suppressing interfiber fusion. Furthermore, if the treatment agent for carbon fiber precursors does not contain wax (A), the anti-fiber fusion properties are insufficient, resulting in fusion of fiber bundles or scumming and tarring, which reduces spinning operability and prevents the production of high-quality carbon fibers. If surfactant (B) is not contained, the surface tension cannot be sufficiently reduced, preventing uniform adhesion to the interior of the fiber bundles, and therefore, uniform anti-fiber fusion properties cannot be obtained.

[0025] The proportion of wax (A) in the nonvolatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of anti-fusing properties, it is preferably 20 to 95 wt%. The upper limit of this weight percentage is more preferably 90 wt%, even more preferably 85 wt%, particularly preferably 83 wt%, and most preferably 80 wt%. On the other hand, the lower limit of this weight percentage is more preferably 25 wt%, even more preferably 28 wt%, particularly preferably 30 wt%, and most preferably 35 wt%. Furthermore, for example, 25 to 90 wt% is more preferable, and 35 to 80 wt% is even more preferable. In the present invention, the nonvolatile content refers to the residue on an aluminum sheet (φ12 cm) when 2.0 to 3.0 g of the treatment agent is spread evenly on the aluminum sheet, dried at 110°C under infrared lamp irradiation, and the fluctuation range of the volatile content over 150 seconds reaches 0.15%.

[0026] When the wax (A) contains normal paraffin, the proportion of normal paraffin in the non-volatile content of the treatment agent is preferably 5 to 95% by weight from the viewpoint of anti-fusing properties. The upper limit of this proportion is more preferably 90% by weight, even more preferably 80% by weight, and particularly preferably 70% by weight. Meanwhile, the lower limit of this proportion is more preferably 8% by weight, even more preferably 10% by weight, and particularly preferably 15% by weight. Also, for example, 8 to 90% by weight is more preferable, and 10 to 80% by weight is even more preferable.

[0027] The proportion of surfactant (B) in the nonvolatile content of the treatment agent of the present invention is not particularly limited, but is preferably 5 to 80% by weight, in order to allow the wax (A) to be uniformly and evenly adhered to the fibers. The upper limit of this proportion is more preferably 50% by weight, even more preferably 45% by weight, particularly preferably 43% by weight, and most preferably 40% by weight. On the other hand, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, particularly preferably 17% by weight, and most preferably 20% by weight. Furthermore, for example, 10 to 43% by weight is more preferable, and 15 to 45% by weight is even more preferable.

[0028] When the treatment agent of the present invention contains a nonionic surfactant, the weight percentage of the nonionic surfactant in the nonvolatile content of the treatment agent is preferably 5 to 35 wt % from the viewpoint of emulsion stability. The upper limit of this weight percentage is more preferably 30 wt %, even more preferably 25 wt %, and particularly preferably 20 wt %. Meanwhile, the lower limit of this weight percentage is more preferably 7 wt %, even more preferably 9 wt %, and particularly preferably 10 wt %. Furthermore, for example, 7 to 35 wt % is more preferable, and 10 to 20 wt % is even more preferable.

[0029] When the treatment agent of the present invention contains a modified silicone having a modifying group containing a nitrogen atom, the proportion of the silicone in the non-volatile content of the treatment agent is not particularly limited, but is preferably 5 to 50 wt% in order to provide excellent smoothness between fibers. The upper limit of this proportion is more preferably 47 wt%, even more preferably 45 wt%, particularly preferably 43 wt%, and most preferably 40 wt%. Meanwhile, the lower limit of this proportion is more preferably 10 wt%, even more preferably 15 wt%, particularly preferably 17 wt%, and most preferably 20 wt%. Furthermore, for example, 10 to 43 wt% is more preferable, and 15 to 45 wt% is even more preferable.

[0030] The weight ratio (B / A) of the surfactant (B) to the wax (A) contained in the treatment agent of the present invention is not particularly limited, but is preferably 0.11 to 2.5, in order that the surfactant (B) can uniformly and evenly adhere the wax (A) to the fibers, thereby stably suppressing fusion between fibers. The upper limit of this ratio is more preferably 2.3, even more preferably 2.0, particularly preferably 1.8, and most preferably 1.5. Meanwhile, the lower limit of this ratio is more preferably 0.15, even more preferably 0.18, particularly preferably 0.20, and most preferably 0.25. Furthermore, for example, a ratio of 0.2 to 5.0 is more preferable, and a ratio of 0.25 to 1.8 is even more preferable.

[0031] [Other Components] The treating agent for carbon fiber precursors of the present invention may contain other components in addition to the above-mentioned components, as long as the effects of the present invention are not impaired. Examples of other components include antioxidants such as phenols, amines, sulfurs, phosphorus, and quinones; antistatic agents such as quaternary ammonium salt-type cationic surfactants and amine salt-type cationic surfactants; smoothing agents such as alkyl esters of higher alcohols and higher alcohol ethers; antibacterial agents; preservatives; rust inhibitors; solvents; and moisture absorbents.

[0032] Furthermore, the treatment agent of the present invention may contain modified silicones other than the modified silicones having a modifying group containing a nitrogen atom, as long as the effects of the present invention are not impaired. Examples of other modified silicones include epoxy-modified silicones, polyether-modified silicones, epoxy polyether-modified silicones (see, for example, Japanese Patent No. 4616934), carbinol-modified silicones, alkyl-modified silicones, phenol-modified silicones, methacrylate-modified silicones, alkoxy-modified silicones, and fluorine-modified silicones. One type of modified silicone may be used, or multiple modified silicones may be used in combination.

[0033] The treatment agent of the present invention may also contain one or more low molecular weight silicones. Examples of low molecular weight silicones include linear or cyclic silicones having 2 to 7 silicon atoms. Specific examples of low molecular weight silicones include octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, heptamethyloctyltrisiloxane, hexamethyldisiloxane, decamethyltetrasiloxane, and dodecamethylpentasiloxane. These low molecular weight silicones may be included as trace components of modified silicones having a nitrogen atom-containing modifying group. The content of low molecular weight silicones in the treatment agent of the present invention is preferably 5 parts by weight or less per 100 parts by weight of modified silicones having a nitrogen atom-containing modifying group.

[0034] In order to uniformly adhere the treatment agent for carbon fiber precursors to the interior of the fiber bundle and stably prevent fusion, the wax (A), surfactant (B), and, if necessary, modified silicone having a modifying group containing a nitrogen atom, etc., are preferably dissolved, solubilized, emulsified, or dispersed in water. The weight percentage of water and the weight percentage of nonvolatile matter in the entire treatment agent for carbon fiber precursors of the present invention are not particularly limited. The weight percentage of water in the entire treatment agent for carbon fiber precursors is preferably 0.1 to 99.9 wt % in terms of transportation costs when transporting the treatment agent and handleability due to emulsion viscosity. The upper limit of this percentage is more preferably 90 wt %, even more preferably 80 wt %, and particularly preferably 50 wt %. Meanwhile, the lower limit of this weight percentage is more preferably 1 wt %, even more preferably 5 wt %, and particularly preferably 10 wt %. For example, 1 to 80 wt % is more preferred, and 5 to 50 wt % is even more preferred.

[0035] The treating agent for carbon fiber precursors of the present invention can be produced by mixing the components described above. The method for emulsifying and dispersing the components described above is not particularly limited, and known techniques can be used. Examples of such methods include a method in which each component constituting the treating agent for carbon fiber precursors is added to warm water under stirring to emulsify and disperse the components, and a method in which each component constituting the treating agent for carbon fiber precursors is mixed and then subjected to mechanical shear force using a homogenizer, homomixer, ball mill, or the like while gradually adding water to perform phase inversion emulsification. Alternatively, a method in which some components are emulsified and then the remaining components are dissolved and dispersed may be used.

[0036] The treating agent for carbon fiber precursors of the present invention can be suitably used as a treating agent (precursor treating agent) for acrylic fibers (precursors) for producing carbon fibers. It may also be used as a treating agent for carbon fiber precursors other than precursors.

[0037] [Carbon fiber precursor and method for producing carbon fiber using the carbon fiber precursor] The carbon fiber precursor of the present invention is produced by adhering the above-mentioned treating agent for carbon fiber precursor to a carbon fiber precursor and spinning it into a fiber. The method for producing carbon fiber of the present invention includes a flame-resistant treatment step of converting the carbon fiber precursor having the above-mentioned treating agent for carbon fiber precursor adhered thereto into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C, and a carbonization treatment step of further carbonizing the flame-resistant fiber in an inert atmosphere at 300 to 2000°C. According to the method for producing carbon fiber of the present invention, the treating agent for carbon fiber precursor of the present invention is used, so that fusion between fibers in the flame-resistant treatment step can be stably suppressed, and high-quality carbon fiber can be produced.

[0038] The spinning process is a process of spinning a carbon fiber precursor by adhering a treating agent for a carbon fiber precursor to the carbon fiber precursor, and preferably includes an adhering process and a drawing process. The adhering process is a process of adhering a treating agent for a carbon fiber precursor after spinning the carbon fiber precursor. That is, the treating agent for a carbon fiber precursor is adhered to the carbon fiber precursor in the adhering process. When the carbon fiber precursor is stretched immediately after spinning, the high-magnification drawing after the adhering process is particularly called the "drawing process." The drawing process may be a wet heat drawing method using high-temperature steam, or a dry heat drawing method using a heated roller. The draw ratio in the drawing process is preferably 2 to 20 times the total draw ratio of the carbon fiber precursor immediately after spinning.

[0039] The precursor is preferably composed of acrylic fibers whose main component is polyacrylonitrile obtained by copolymerizing at least 95 mol% or more of acrylonitrile with 5 mol% or less of a flame retardant-promoting component. A vinyl group-containing compound copolymerizable with acrylonitrile is preferably used as the flame retardant-promoting component. The precursor single fiber fineness is not particularly limited, but is preferably 0.1 to 2.0 dtex in terms of the balance between performance and production costs. The number of single fibers constituting the precursor fiber bundle is also not particularly limited, but is preferably 1,000 to 96,000 in terms of the balance between performance and production costs.

[0040] The treating agent for carbon fiber precursors of the present invention may be applied to the carbon fiber precursor at any stage in the carbon fiber production process, but is preferably applied once before the drawing process. It may be applied at any stage before the drawing process, for example, immediately after spinning. It may also be applied at any stage after the drawing process, for example, immediately after the drawing process, or at the winding stage, or immediately before the flame retardant treatment process. With regard to the application method, it may be applied using a roller or the like, or it may be applied by a dipping method, a spraying method, or the like.

[0041] In the adhesion treatment step, the application rate of the treatment agent for carbon fiber precursors is preferably 0.1 to 5 wt %, more preferably 0.3 to 1.5 wt %, based on the weight of the carbon fiber precursor, in order to strike a balance between obtaining the effect of preventing fusion between fibers and preventing deterioration in the quality of the carbon fiber due to tar products of the treatment agent in the carbonization treatment step. Note that the application rate of the treatment agent for carbon fiber precursors here is defined as the percentage of the weight of the nonvolatile components to which the treatment agent for carbon fiber precursors is attached relative to the weight of the carbon fiber precursor.

[0042] The flame-resistant treatment step is a step of converting a carbon fiber precursor having a carbon fiber precursor treating agent attached thereto into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C. The oxidizing atmosphere may typically be an air atmosphere. The temperature of the oxidizing atmosphere is preferably 230 to 280°C. In the flame-resistant treatment step, the acrylic fiber after the attachment treatment is heat-treated for 20 to 100 minutes (preferably 30 to 60 minutes) while applying a tension at a draw ratio of 0.90 to 1.10 (preferably 0.95 to 1.05). In this flame-resistant treatment, a flame-resistant fiber having a flame-resistant structure is produced through intramolecular cyclization and oxygen addition to the ring.

[0043] The carbonization step is a step in which the flame-resistant fiber is further carbonized in an inert atmosphere at 300 to 2000°C. In the carbonization step, it is preferable to first perform a preliminary carbonization step (first carbonization step) in which the flame-resistant fiber is heat-treated for several minutes in an inert atmosphere such as nitrogen or argon in a baking furnace having a temperature gradient from 300 to 800°C while applying a tension at a draw ratio of 0.95 to 1.15. Thereafter, to further promote carbonization and graphitization, the flame-resistant fiber is heat-treated for several minutes in an inert atmosphere such as nitrogen or argon while applying a tension at a draw ratio of 0.95 to 1.05, which is higher than that of the first carbonization step, to perform a second carbonization step, thereby carbonizing the flame-resistant fiber. Regarding the control of the heat treatment temperature in the second carbonization step, it is preferable to set the maximum temperature to 1000°C or higher (preferably 1000 to 2000°C) while applying a temperature gradient. This maximum temperature is appropriately selected and determined depending on the desired properties (tensile strength, modulus of elasticity, etc.) of the carbon fiber.

[0044] In the method for producing carbon fibers of the present invention, if a carbon fiber with an even higher elastic modulus is desired, a graphitization step can be carried out subsequent to the carbonization step. The graphitization step is usually carried out in an inert atmosphere such as nitrogen or argon at a temperature of 2000 to 3000°C while applying tension to the fiber obtained in the carbonization step.

[0045] The carbon fibers obtained in this manner can be surface-treated depending on the purpose to enhance the adhesive strength with the matrix resin when they are made into a composite material. Gas-phase or liquid-phase treatments can be used as the surface treatment method, and from the viewpoint of productivity, liquid-phase treatments using an electrolyte such as an acid or alkali are preferred. Furthermore, various sizing agents that are highly compatible with the matrix resin can be added to improve the processability and handling of the carbon fibers.

[0046] The present invention will be described in more detail below with reference to examples, but is not limited to these examples. In the following examples, percentages (%) and parts are by weight unless otherwise specified. Measurements of each property were carried out according to the methods described below.

[0047] <Applied ratio of treatment agent for carbon fiber precursor> The applied ratio of the treatment agent for carbon fiber precursor was calculated by the ethanol extraction method using a Soxhlet extractor. However, for treatment agents containing silicone, the applied ratio was calculated by the following method. The carbon fiber precursor to which the treatment agent had been applied was alkali-fused with potassium hydroxide / sodium butyrate, then dissolved in water and adjusted to pH 1 with hydrochloric acid. Sodium sulfite and ammonium molybdate were added to this to develop color, and colorimetric quantification of silicomolybdenum blue (wavelength 815 mμ) was performed to determine the silicon content. The applied ratio (wt%) of the treatment agent for carbon fiber precursor was calculated using the silicon content determined here and the silicon content in the treatment agent previously determined by the same method.

[0048] <Collision of fiber bundle> The degree of collimation of the fiber bundle was observed when winding and unwinding in the spinning process of the carbon fiber precursor, and at the inlet and outlet of the flame-proofing furnace in the flame-proofing process, and was visually evaluated overall according to the following evaluation criteria. ◎: The fiber bundle was of uniform thickness, and no loosening of single fibers was observed, showing very excellent collimation. ○: The fiber bundle was of uniform thickness, and almost no loosening of single fibers was observed, showing excellent collimation. △: The fiber bundle was of uniform thickness, but some loosened single fibers were observed, showing slightly poor collimation. ×: Many loosened single fibers were observed, and single fiber breakage was also observed, showing poor collimation.

[0049] <Spinning operability (roller staining)> The degree of staining (gum-up) of the drying roller after applying the treatment agent to 50 kg of carbon fiber precursor was evaluated according to the following evaluation criteria. ⊚: No roller staining due to gum-up, and spinning operability is very excellent. ○: Little roller staining due to gum-up, and spinning operability is excellent. △: Roller staining due to gum-up occurs, and spinning operability is slightly poor. ×: Roller staining due to gum-up is significant, and single yarns are taken out and wrapped around during spinning, and spinning operability is poor.

[0050] <Anti-fusing property> Fifty locations were randomly selected from 10 m of flame-resistant fiber, and 10 mm long short fibers were cut out from these locations. The number of fused fiber bundles was evaluated according to the following evaluation criteria: ◎: The number of fused fiber bundles was 0 to 1, indicating very excellent anti-fusing property. ○: The number of fused fiber bundles was 2 to 5, indicating excellent anti-fusing property. △: The number of fused fiber bundles was 6 to 10, indicating slightly poor anti-fusing property. ×: The number of fused fiber bundles was 11 or more, indicating poor anti-fusing property.

[0051] <Abrasion Resistance> Using a TM-type frictional embracing force tester TM-200 (manufactured by Daiei Scientific Instruments Co., Ltd.), a carbon fiber precursor strand (12K) was abraded 1,000 times (reciprocating motion speed: 300 times / min) with a tension of 50 g using three mirror-finish chrome-plated stainless steel needles arranged in a zigzag pattern, and the state of fluffing of the carbon fiber precursor strand was visually evaluated according to the following criteria. ⊚: No fluffing was observed, just like before abrasion, and the abrasion resistance was very excellent. ○: Only a few fluffs were observed, and the abrasion resistance was excellent. Δ: There was some fluffing, and the abrasion resistance was somewhat poor. ×: There was much fluffing, and significant single yarn breakage was observed, and the abrasion resistance was poor.

[0052] <Carbon Fiber Strength> Measurement was carried out in accordance with the epoxy resin impregnated strand method specified in JIS-R-7608, and the average value of 10 measurements was taken as the carbon fiber strength (GPa).

[0053] Example 1 Wax A-1, surfactants B-1 and B-4 were charged into a 2 L SUS autoclave equipped with a high-speed homogenizer so that the non-volatile content of the treatment agent would be as shown in Table 1. The autoclave was pressurized to 0.3 MPa with nitrogen gas and then released three times to completely replace the air in the autoclave with nitrogen gas. The contents were then heated to 150°C while stirring at high speed with the high-speed homogenizer and mixed with stirring for 1 hour. Next, hot water heated to 150°C was added dropwise over 2 hours from another SUS autoclave attached to the top of the autoclave containing the wax, etc., to the autoclave containing the wax, etc., for phase inversion emulsification. After the entire amount of hot water was added dropwise, the mixture was stirred at 150°C for 1 hour, then cooled to 80°C, the autoclave was released to normal pressure, and further cooled to 40°C to prepare a treatment agent for carbon fiber precursors with a non-volatile content of 20 wt%. The weight ratio of wax A-1 to the nonvolatile content of the treatment agent was 75 wt %, the weight ratio of surfactant B-1 was 20 wt %, and the weight ratio of surfactant B-4 was 5 wt %. Next, the adjusted treatment agent was further diluted with water to obtain a diluted solution with a nonvolatile content concentration of 3.0 wt %. The diluted solution was applied to raw acrylic fiber of a carbon fiber precursor obtained by copolymerizing 97 mol % of acrylonitrile and 3 mol % of itaconic acid so that the nonvolatile content of the treatment agent was 1.0 wt %. A drawing process (steam drawing, draw ratio 2.1 times) was performed to produce a carbon fiber precursor (single fiber fineness 0.8 dtex, 24,000 filaments). This carbon fiber precursor was subjected to a flame-resistant treatment in a 250 °C flame-resistant furnace for 60 minutes to obtain a flame-resistant fiber. Subsequently, the flame-resistant fiber was converted into carbon fiber by calcining in a carbonization furnace with a temperature gradient of 300 to 1400 °C under a nitrogen atmosphere. The evaluation results of each characteristic value are shown in Table 1.

[0054] [Examples 2 to 32] Carbon fiber precursors and carbon fibers after treatment agent adhesion were obtained in the same manner as in Example 1, except that the treatment agent was adjusted so that the non-volatile composition of the treatment agent was as shown in Tables 1 to 3. The evaluation results of each property value are shown in Tables 1 to 3.

[0055] [Comparative Examples 1 to 6, 17] For Comparative Examples 1 to 6, and 17, the components and water were added and stirred to obtain the nonvolatile composition of the treatment agent shown in Tables 4 and 5, to prepare a treatment agent for carbon fiber precursors with a nonvolatile content of 20 wt%. The prepared treatment agent was then further diluted with water to obtain a diluted solution with a nonvolatile content of 3.0 wt%. The diluted solution was applied to raw acrylic fiber for a carbon fiber precursor obtained by copolymerizing 97 mol% acrylonitrile and 3 mol% itaconic acid at a 1.0% application rate, and a drawing process (steam drawing, draw ratio 2.1 times) was performed to prepare a carbon fiber precursor (single fiber fineness 0.8 dtex, 24,000 filaments). This carbon fiber precursor was subjected to a flame-resistant treatment in a 250°C flame-resistant furnace for 60 minutes to obtain a flame-resistant fiber. It was then converted into carbon fiber by calcination in a carbonization furnace with a temperature gradient of 300 to 1400°C under a nitrogen atmosphere. The evaluation results of each property value are shown in Tables 4 and 5. Note that the treatment agents of Comparative Examples 2 to 6 and 17 had poor spinning operability, and flame-resistant fibers and carbon fibers suitable for evaluation could not be obtained, so evaluation of fusion prevention properties, abrasion resistance, and carbon fiber strength could not be performed.

[0056] Comparative Examples 7-16: Using the respective treatment agents shown in Tables 4 and 5 for Comparative Examples 7-16, the treatment agents were heated above their melting points and uniformly dissolved in Comparative Examples 7-14, or at 30°C for Comparative Examples 15 and 16. The treatment agents were applied to raw acrylic fibers of a carbon fiber precursor obtained by copolymerizing 97 mol% acrylonitrile and 3 mol% itaconic acid by dip oiling at a 1.0% application rate. The fibers were then stretched (steam stretching, stretch ratio: 2.1 times) to produce carbon fiber precursors (single fiber fineness: 0.8 dtex, 24,000 filaments). The carbon fiber precursors were subjected to a flame-stabilizing treatment in a 250°C flame-stabilizing furnace for 60 minutes to obtain flame-stabilized fibers. The flame-stabilized fibers were then converted into carbon fibers by calcining in a carbonization furnace with a temperature gradient of 300-1400°C under a nitrogen atmosphere. The evaluation results for each property are shown in Tables 4 and 5. The treatment agents of Comparative Examples 15 and 16 had poor spinning operability, and flame-retardant fibers and carbon fibers suitable for evaluation could not be obtained, so evaluation of fusion resistance, abrasion resistance, and carbon fiber strength could not be performed.

[0057] The details of the volatile composition are as follows: <Waxes> Wax A-1: ​​Beeswax (melting point: 65°C) Wax A-2: Carnauba wax (melting point: 83°C, acid value: 8.3 mgKOH / g) Wax A-3: Candelilla wax (melting point: 71°C, acid value: 17.1 mgKOH / g) Wax A-4: Polyethylene wax (melting point: 130°C) Wax A-5: Oxidized polyethylene wax (melting point: 138°C, acid value: 30 mgKOH / g) Wax A-6: Paraffin wax 135F (melting point: 57°C) Wax A-7: Paraffin wax 150F (melting point: 66°C)

[0058] <Surfactants (B)> Surfactant B-1: POE (20) lauryl ether Surfactant B-2: POE (8) oleyl ether Surfactant B-3: POE (5) cetyl ether Surfactant B-4: stearic acid monoglyceride Surfactant B-5: oleic acid monoglyceride Surfactant B-6: behenic acid sodium salt Note that POE (20) indicates that 20 moles of polyoxyethylene have been added. Different values ​​in parentheses indicate different numbers of moles of polyoxyethylene added.

[0059] <Amino-modified silicone> Amino-modified silicone C-1: kinematic viscosity at 25°C: 1,300 mm ２ / s, amino equivalent: 2,000 g / mol Amino-modified silicone C-2: 25°C kinematic viscosity: 4,500 mm ２ / s, amino equivalent: 1,000 g / mol Amino-modified silicone C-3: 25°C kinematic viscosity: 120 mm ２ / s, amino equivalent: 5,000 g / mol

[0060] <Other ingredients> D-1: Isotridecyl trimellitate D-2: Oleyl oleate D-3: Polyoxyethylene 10 mole adduct of bisphenol A

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] As is clear from Tables 1 to 5, the treating agents for carbon fiber precursors in the Examples were excellent in anti-fusing properties because they were treating agents for carbon fiber precursors containing wax (A) and surfactant (B). On the other hand, when they did not contain wax (A) (Comparative Examples 1 to 6, 17), when they did not contain surfactant (B) (Comparative Examples 7 to 14), or when they did not contain wax (A) or surfactant (B) (Comparative Examples 15, 16), spinning operability was poor and they could not be used as treating agents for carbon fiber precursors (Comparative Examples 2 to 6, 15 to 17), or anti-fusing properties were poor (Comparative Examples 1, 7 to 14), and the problems of the present application could not be solved.

[0067] The treating agent for carbon fiber precursors of the present invention is a treating agent used when producing a carbon fiber precursor, and is useful for producing high-quality carbon fibers. The carbon fiber precursor of the present invention is provided with the treating agent of the present invention and is useful for producing high-quality carbon fibers. High-quality carbon fibers can be obtained by the carbon fiber production method of the present invention.

Claims

1. A treatment agent for carbon fiber precursors, comprising a wax (A) and a surfactant (B).

2. The treatment agent for carbon fiber precursors according to claim 1, wherein the melting point of the wax (A) is 50 to 140°C.

3. The treatment agent for carbon fiber precursors according to claim 1 or 2, wherein the wax (A) accounts for 20 to 95% by weight of the non-volatile content of the treatment agent.

4. The treatment agent for carbon fiber precursors according to any one of claims 1 to 3, wherein the wax (A) comprises at least one wax selected from the group consisting of animal-based waxes, vegetable-based waxes, polyolefin waxes, paraffin waxes, microcrystalline waxes, and Fischer-Tropsch waxes.

5. The treatment agent for carbon fiber precursors according to any one of claims 1 to 4, wherein the surfactant (B) includes a surfactant having a hydrocarbon group having 6 to 40 carbon atoms.

6. A carbon fiber precursor having the treating agent for carbon fiber precursors according to any one of claims 1 to 5 adhered thereto.

7. A method for producing carbon fibers, comprising: a flame-retardant treatment step of converting the carbon fiber precursor according to claim 6 into a flame-retardant fiber in an oxidizing atmosphere at 200 to 300°C; and a carbonization treatment step of further carbonizing the flame-retardant fiber in an inert atmosphere at 300 to 2,000°C.

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