Treatment agent for carbon fiber precursor and use of same

Abstract

The purpose of the present invention is to provide: a treatment agent that is for a carbon fiber precursor and that can impart to the carbon fiber precursor a property such that single yarn breakages that could occur in a flame resistance imparting process are suppressed; a carbon fiber precursor obtained by the use of the treatment agent; and a method for producing a carbon fiber using the carbon fiber precursor.　This treatment agent for a carbon fiber precursor contains a smooth component (A), a radical scavenger (B), and a peroxide decomposition agent (C). The radical scavenger (B) is at least one selected from a phenol-based radical scavenger (B1) and an aromatic amine-based radical scavenger (B2). The peroxide decomposition agent (C) is at least one selected from a sulfur-based peroxide decomposition agent (C1) and a phosphorus-based peroxide decomposition agent (C2).

Description

Treatment agent for carbon fiber precursor and its use

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

[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 is to convert a carbon fiber precursor into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C (hereinafter sometimes referred to as the flame-resistant process), followed by carbonization in an inert atmosphere at 300 to 2000°C (hereinafter sometimes referred to as the carbonization process). (Hereinafter, the flame-resistant process and carbonization process will be collectively referred to as the calcination process.) To efficiently perform these calcination processes and improve the physical properties of carbon fibers, methods have been proposed in which various treatment agents are applied to the carbon fiber precursor. (See Patent Documents 1 to 3.)

[0003] Japanese Unexamined Patent Publication No. 2011-202336 Japanese Unexamined Patent Publication No. 2012-46855 Japanese Unexamined Patent Application No. 11-012856

[0004] However, when carbon fibers are produced using carbon fiber precursors to which such a treatment agent has been applied, a problem of reduced passability through the calcination step often occurs. The cause of this problem was investigated and it was found to be due to single-fiber breakage occurring in the flame-resistant treatment step. Therefore, an object of the present invention is to provide a treatment agent for carbon fiber precursors that can impart to carbon fiber precursors the ability to suppress single-fiber breakage in the flame-resistant treatment step, a carbon fiber precursor using the treatment agent, and a method for producing carbon fibers using the carbon fiber precursor.

[0005] As a result of intensive research to solve the above problems, the present inventors have found that a treatment agent for carbon fiber precursors containing a smoothing component (A), a specific radical scavenger (B), and a specific peroxide decomposer (C) can impart excellent single yarn breakage suppression properties to the carbon fiber precursor in the flame retardation step.

[0006] That is, the treating agent for carbon fiber precursors of the present invention includes the following embodiments. <1> A treating agent for carbon fiber precursors containing a smoothing component (A), a radical scavenger (B), and a peroxide decomposer (C), wherein the radical scavenger (B) is at least one selected from a phenol-based radical scavenger (B1) and an aromatic amine-based radical scavenger (B2), and the peroxide decomposer (C) is at least one selected from a sulfur-based peroxide decomposer (C1) and a phosphorus-based peroxide decomposer (C2). <2> The treating agent for carbon fiber precursors according to <1>, wherein the sulfur-based peroxide decomposer (C1) includes at least one selected from a sulfur-containing ester compound (C1-1) represented by the following general formula (1) and a sulfur-containing ester compound (C1-2) represented by the following general formula (2): (In formula (1), m and n are each independently an integer of 1 to 4, and R １ and R ２ are each independently a hydrocarbon group having 12 to 32 carbon atoms. (In formula (2), m and n each independently represent an integer of 1 to 4, and R ３ is a hydrocarbon group having 12 to 32 carbon atoms.) <3> The sulfur-based peroxide decomposer (C1) is １ and the R ２ are each independently a hydrocarbon group having 14 to 22 carbon atoms, and ３is a hydrocarbon group having 14 to 22 carbon atoms. <4> The treatment agent for carbon fiber precursors according to <2> or <3>, wherein the sulfur-based peroxide decomposer (C1) contains the sulfur-containing ester compound (C1-1) and the sulfur-containing ester compound (C1-2). <5> The treatment agent for carbon fiber precursors according to any one of <1> to <4>, wherein the weight ratio ((B) / (C)) of the radical scavenger (B) to the peroxide decomposer (C) is 0.49 or less. <6> The treatment agent for carbon fiber precursors according to any one of <1> to <5>, wherein the total proportion of the radical scavenger (B) and the peroxide decomposer (C) in the non-volatile content of the treatment agent for carbon fiber precursors is more than 5.0 wt%. <7> The treatment agent for carbon fiber precursors according to any one of <1> to <6>, wherein the smoothing component (A) contains at least one selected from an amino group-containing silicone (A1) and an ester compound (A2). <8> The treatment agent for carbon fiber precursors according to any one of <1> to <7>, wherein the smoothing component (A) contains a nonionic surfactant (D). <9> A carbon fiber precursor obtained by adhering the treatment agent for carbon fiber precursors according to any one of <1> to <8> to a raw material carbon fiber precursor for the carbon fiber precursor. <10> A method for producing carbon fibers, comprising: a flame-resistant step of converting the carbon fiber precursor according to <9> into a flame-resistant fiber; and a carbonization step of carbonizing the flame-resistant fiber.

[0007] The treating agent for carbon fiber precursors of the present invention can impart excellent single-fiber breakage suppression properties to the carbon fiber precursor in the flame-resistant treatment step. According to the carbon fiber precursor using the treating agent for carbon fiber precursors of the present invention and the method for producing carbon fiber using the carbon fiber precursor, the carbon fiber precursor produced by applying the treating agent has excellent single-fiber breakage suppression properties in the flame-resistant treatment step, and therefore high-quality carbon fiber can be obtained.

[0008] 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. [Smooth Component (A)] The treating agent of the present invention contains a smooth component (A). As the smooth component (A), a known smooth component used in treating agents can be used. Examples of known smooth components include silicone compounds, mineral oils, polyolefins, and ester compounds (A2). These smooth components may be used alone or in combination of two or more. Among these, the smooth component (A) preferably contains at least one selected from silicone compounds and ester compounds (A2), and more preferably contains a silicone (A1) having an amino group.

[0009] The silicone compound is not particularly limited as long as it has an inorganic siloxane bond (—Si—O—Si—) main chain and an organic group in the side chain, and examples thereof include silicone (A1) having an amino group, silicone having a polyether group, dimethyl silicone, epoxy-modified silicone, amide-modified silicone, alkyl-modified silicone, aralkyl-modified silicone, phenyl-modified silicone, silanol-modified silicone, carbinol-modified silicone, mercapto-modified silicone, etc. In terms of achieving the effects of the present application, it is preferable to include at least one selected from silicone (A1) having an amino group, silicone having a polyether group, dimethyl silicone, alkyl-modified silicone, phenyl-modified silicone, and aralkyl-modified silicone, it is more preferable to include at least one selected from silicone (A1) having an amino group and silicone having a polyether group, and it is even more preferable to include silicone (A1) having an amino group. As the silicone compound, known compounds can be used.

[0010] [Silicone (A1) Having an Amino Group] The amino group-containing silicone (A1) is not particularly limited as long as it has an inorganic siloxane bond (—Si—O—Si—) main chain and an organic group having an amino group on the side chain and / or terminal, and known silicones having an amino group can be appropriately used. Examples of silicones having an amino group include amino-modified silicones and amino polyether-modified silicones, and in terms of achieving the effects of the present application, it is more preferable to include an amino-modified silicone. One or more types of silicones having an amino group (A1) may be used. Note that the amino polyether-modified silicone is a silicone having an amino group (including an organic group having an amino group) and a polyether group (including an organic group having a polyoxyalkylene group).

[0011] The amino group-containing silicone (A1) has a kinematic viscosity at 25°C of 50 to 20,000 mm from the viewpoints of uniform adhesion to fibers, suppression of scattering of the treatment agent, and imparting sizing properties to fibers. ２ The upper limit of the kinematic viscosity is more preferably 15,000 mm ２ / s, more preferably 12000 mm ２ / s, particularly preferably 10,000 mm ２ On the other hand, the lower limit of the kinematic viscosity is more preferably 100 mm ２ / s, more preferably 150 mm ２ / s, particularly preferably 200 mm ２ / s. For example, 100 to 15,000 mm ２ / s is more preferable, and 150 to 10,000 mm ２ / s is more preferred.

[0012] The amino group (including an organic group having an amino group) which is the modified group of the amino group-containing silicone (A1) may be bonded to a side chain of the silicone main chain, to an end, or to both, but from the viewpoint of protecting the fibers in the flame-proofing treatment step, it is preferable that it be bonded to a side chain (having an amino group on the side chain). Furthermore, the amino group may be any of a monoamine type, a diamine type, or a polyamine type, and both may coexist in one molecule, but from the viewpoint of uniformly applying the treatment agent to the inside of the fiber bundle in the flame-proofing treatment step and forming a film with the treatment agent to protect the fibers, the monoamine type or diamine type is preferred, and the diamine type is more preferred.

[0013] The amino equivalent of the amino group-containing silicone (A1) is preferably 300 to 10,000 g / mol from the viewpoint of preventing adhesion or fusion between fibers. The upper limit of the amino equivalent is more preferably 9,500 g / mol, even more preferably 9,000 g / mol, and particularly preferably 8,000 g / mol. Meanwhile, the lower limit of the amino equivalent is more preferably 500 g / mol, even more preferably 1,000 g / mol, and particularly preferably 1,500 g / mol. Furthermore, for example, 500 to 9,000 g / mol is more preferable, and 1,000 to 8,000 g / mol is even more preferable. Here, the amino equivalent refers to the mass of the siloxane skeleton per amino group or ammonium group. The unit of g / mol is a value converted to per mol of amino groups or ammonium groups. Therefore, a smaller amino equivalent value indicates a higher ratio of amino groups or ammonium groups in the molecule.

[0014] The amino group-containing silicone (A1) may be a combination of multiple amino group-containing silicones with different amino equivalents and kinematic viscosities (25°C). When two or more types of amino group-containing silicones are used, the amino equivalent refers to the amino equivalent of the entire amino group-containing silicone (A1) (mixture), and the kinematic viscosity at 25°C refers to the kinematic viscosity of the entire amino group-containing silicone (A) (mixture).

[0015] [Ester Compound (A2)] The ester compound (A2) is not particularly limited as long as it is a compound having a structure in which an alcohol compound (X) and a carboxylic acid compound (Y) are esterified, but from the viewpoint of sizing ability, at least one selected from an ester of a monohydric alcohol compound and a monocarboxylic acid, an ester of a polyhydric alcohol compound and a monocarboxylic acid, and an ester of a polycarboxylic acid and a monohydric alcohol is preferred, at least one selected from an ester of a polyhydric alcohol compound and a monocarboxylic acid, and an ester of a polycarboxylic acid and a monohydric alcohol is more preferred, and an ester of a polyhydric alcohol compound and a monocarboxylic acid is even more preferred. One or more types of ester compound (A2) may be used.

[0016] The number of ester bonds that the ester compound (A2) has in its molecule is not particularly limited, but from the viewpoint of sizing ability, it is preferable that the number be 2 or more. The upper limit of the number of ester bonds is preferably 10, more preferably 8, and even more preferably 6. On the other hand, the lower limit of the number of ester bonds is more preferably 3, more preferably 4, and particularly preferably 5. Furthermore, for example, 2 to 10 are more preferable, and 2 to 8 are even more preferable.

[0017] The number of hydroxyl groups contained in the ester compound (A2) molecule is not particularly limited, but from the viewpoint of sizing ability, it is preferably 15 or less. The upper limit of the number of hydroxyl groups is preferably 12, more preferably 10, and even more preferably 8. On the other hand, the lower limit of the number of hydroxyl groups is more preferably 1, more preferably 2, and particularly preferably 4. Furthermore, for example, 0 to 10 hydroxyl groups are more preferred, and 1 to 8 hydroxyl groups are even more preferred.

[0018] The molecular weight of the ester compound (A2) is not particularly limited, but is preferably 650 or more from the viewpoint of sizing ability. The upper limit of the molecular weight is preferably 5000, more preferably 4500, and even more preferably 4000. On the other hand, the lower limit of the molecular weight is more preferably 700, more preferably 750, and particularly preferably 800. Also, for example, 700 to 4500 is more preferable, and 750 to 4000 is even more preferable. Note that the molecular weight of the ester compound (A) in the present invention is the sum of the atomic weights of the atoms constituting the compound, calculated using the standard atomic weights published by IUPAC.

[0019] The alcohol compound (X) is not particularly limited as long as it is a compound that can react with the carboxylic acid compound (Y) to form an ester bond, and known compounds can be used. The number of carbon atoms in the alcohol (X) is preferably 6 to 40 in terms of convergence, and the upper limit of the carbon number is more preferably 35, even more preferably 30, and particularly preferably 20. On the other hand, the lower limit of the carbon number is more preferably 7, even more preferably 8, and particularly preferably 9. Furthermore, for example, the number is more preferably 6 to 35, and even more preferably 6 to 20.

[0020] The number of hydroxyl groups possessed by the alcohol compound (X) is preferably 3 to 20 in terms of sizing ability. The upper limit of the number of hydroxyl groups is more preferably 15, even more preferably 12, and particularly preferably 10. On the other hand, the lower limit of the number of hydroxyl groups is more preferably 4, even more preferably 5, and particularly preferably 6. Also, for example, the number is more preferably 3 to 15, and even more preferably 4 to 12.

[0021] The alcohol compound (X) is not particularly limited, but specific examples thereof include monohydric alcohol compounds such as octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, isocetyl alcohol, oleyl alcohol, and isostearyl alcohol, phenol, alkylene oxide adducts of octyl alcohol, alkylene oxide adducts of 2-ethylhexyl alcohol, alkylene oxide adducts of decyl alcohol, alkylene oxide adducts of lauryl alcohol, and myristyl alcohol. Examples of the alkylene oxide adducts include alkylene oxide adducts of oleyl alcohol, alkylene oxide adducts of isocetyl alcohol, alkylene oxide adducts of oleyl alcohol, alkylene oxide adducts of isostearyl alcohol, and alkylene oxide adducts of phenol. Examples of the polyhydric alcohol compounds include trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, sorbitol, xylitol, mannitol, diglycerin, triglycerin, tetraglycerin, decaglycerin, bisphenol A, trimethylol Alkylene oxide adducts of sorbitan, alkylene oxide adducts of trimethylolpropane, alkylene oxide adducts of pentaerythritol, alkylene oxide adducts of sorbitan, alkylene oxide adducts of sorbitol, alkylene oxide adducts of xylitol, alkylene oxide adducts of mannitol, alkylene oxide adducts of diglycerin, alkylene oxide adducts of triglycerin, alkylene oxide adducts of tetraglycerin, alkylene oxide adducts of decaglycerin, bisphenol Examples of the alkylene oxide adducts of A include, from the viewpoint of sizing ability, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, sorbitol, xylitol, mannitol, diglycerin, triglycerin, tetraglycerin, and decaglycerin are preferred, and trimethylolpropane, sorbitan, sorbitol, mannitol, diglycerin, triglycerin, tetraglycerin, and decaglycerin are more preferred, and trimethylolpropane, sorbitan, sorbitol, triglycerin, tetraglycerin, and decaglycerin areBisphenol A is particularly preferred. The alcohol compound (X) may be used alone or in combination of two or more.

[0022] The carboxylic acid compound (Y) is not particularly limited, but from the viewpoint of sizing ability and fuzz suppression, a carboxylic acid compound having 4 to 24 carbon atoms is preferred. The upper limit of the carbon number is more preferably 22, even more preferably 20, and particularly preferably 18. On the other hand, the lower limit of the carbon number is more preferably 6, even more preferably 8, and particularly preferably 10. Also, for example, 6 to 22 is more preferred, and 8 to 20 is more preferred.

[0023] The carboxylic acid compound (Y) is not particularly limited, and specific examples thereof include monocarboxylic acids such as butyric acid, crotonic acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, myristoleic acid, pentadecanoic acid, palmitic acid, palmitoleic acid, isocetylic acid, margaric acid, stearic acid, isostearic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linolenic acid, tuberculostearic acid, arachidic acid, isoeicosaic acid, gadoleic acid, eicosenoic acid, docosanoic acid, isodocosanoic acid, erucic acid, tetracosanoic acid, isotetracosanoic acid, nervonic acid, cerotic acid, montanic acid, and melissic acid, and examples of polycarboxylic acids include citric acid, isocitric acid, malic acid, and aconitic acid. , oxaloacetic acid, oxalosuccinic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, diphenyl ether dicarboxylic acid, naphthalenedicarboxylic acid, phenylmalonic acid, phenylsuccinic acid, β-phenylglutaric acid, α-phenyladipic acid, β-phenyladipic acid, biphenyl-2,2'- or 4,4'-dicarboxylic acid, trimellitic acid, pyromellitic acid, etc., and from the viewpoint of sizing ability, phthalic acid, isophthalic acid, terephthalic acid, biphenyl-2,2'- or 4,4'-dicarboxylic acid, trimellitic acid, pyromellitic acid are preferred, and biphenyl-2,2'- or 4,4'-dicarboxylic acid, trimellitic acid, pyromellitic acid are more preferred. Carboxylic acid compound (Y) may be used alone or in combination.

[0024] The ester compound (A2) is not particularly limited as long as it is a compound having an esterified structure between the alcohol compound (X) and the carboxylic acid compound (Y). From the viewpoint of sizing ability, however, a compound having an esterified structure between an aliphatic alcohol compound and an aromatic carboxylic acid compound and a compound having an esterified structure between an aromatic alcohol compound and an aliphatic carboxylic acid compound are preferred, and an aliphatic alcohol compound and an aromatic carboxylic acid compound are more preferred.

[0025] The compound having a structure in which an aliphatic alcohol compound and an aromatic carboxylic acid compound are esterified is not particularly limited, but examples thereof include trimellitic acid esters, pyromellitic acid esters, phthalic acid esters, and benzoic acid esters, and from the viewpoint of sizing ability, trimellitic acid esters and pyromellitic acid esters are preferred.

[0026] The compound having an ester structure of an aromatic alcohol compound and an aliphatic carboxylic acid compound is not particularly limited, and examples thereof include esters of bisphenol A and fatty acids, esters of polyoxyalkylene adducts of bisphenol A and fatty acids, esters of phenol and fatty acids, and esters of naphthol and fatty acids. From the viewpoint of sizing ability, the esters of bisphenol A and fatty acids and the esters of phenol and fatty acids are preferred.

[0027] The method for obtaining the ester compound (A2) is not particularly limited, but a commercially available ester compound can be used.

[0028] [Radical Scavenger (B)] The treating agent of the present invention contains a radical scavenger (B). The radical scavenger (B) is at least one selected from a phenolic radical scavenger (B1) and an aromatic amine radical scavenger (B2). In terms of heat generation suppression, it is preferable to include a phenolic radical scavenger (B1). In the present invention, heat generation suppression refers to suppressing heat generation generated during the flame-stabilizing reaction of the carbon fiber precursor. In the present invention, the radical scavenger refers to a compound that captures radicals such as alkoxy radicals and peroxy radicals.

[0029] The phenol-based radical scavenger (B1) is not particularly limited, and examples thereof include hindered phenol-based radical scavengers, etc. Examples of the hindered phenol-based radical scavengers include monophenol-based radical scavengers, bisphenol-based radical scavengers, and polymeric phenol-based radical scavengers, and from the viewpoint of suppressing heat generation, it is preferable to include at least one selected from bisphenol-based radical scavengers and polymeric phenol-based radical scavengers, and it is more preferable to include a polymeric phenol-based radical scavengers.

[0030] Examples of monophenol radical scavengers include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

[0031] Examples of bisphenol radical scavengers include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, and the like.

[0032] Examples of polymeric phenolic radical scavengers include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocophenol.

[0033] The aromatic amine-based radical scavenger (B2) is not particularly limited, but from the viewpoint of suppressing heat generation, it preferably contains at least one selected from naphthylamine-based radical scavengers and phenyleneamine-based radical scavengers, and more preferably contains a naphthylamine-based radical scavenger.

[0034] Examples of naphthylamine-based radical scavengers include 1-naphthylamine, phenyl-1-naphthylamine, phenyl-α-naphthylamine, etc. Examples of phenyleneamine-based radical scavengers include N,N'-diisopropyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, etc. Examples of aromatic amine-based radical scavengers (B2) other than naphthylamine-based radical scavengers and phenyleneamine-based radical scavengers include diphenylamine, N-phenyl-p-toluidine, bis-p-toluylamine, p,p'-dioctyldiphenylamine, etc.

[0035] [Peroxide Decomposer (C)] The treating agent of the present invention contains a peroxide decomposer (C). The peroxide decomposer (C) is at least one selected from sulfur-based peroxide decomposers (C1) and phosphorus-based peroxide decomposers (C2). In terms of suppressing heat generation, it is preferable to include a sulfur-based peroxide decomposer (C1). In the present invention, the peroxide decomposer refers to a compound that inactivates peroxides generated by thermal decomposition, oxidation, or the like.

[0036] The sulfur-based peroxide decomposer (C1) is not particularly limited, but examples thereof include sulfur-containing ester compounds, and thiodipropionate esters are more preferred in terms of suppressing heat generation.

[0037] Examples of the sulfur-based peroxide decomposer (C1) include 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-(dodecylthio)propionate], ditridecyl 3,3'-thiobispropionate, 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis[(octylthio)methyl]-o-cresol, and 2,4-bis[(laurylthio)methyl]-o-cresol.

[0038] The sulfur-containing ester compound is not particularly limited as long as it is an ester compound that has a sulfur atom and is a peroxide decomposer. However, from the viewpoint of suppressing heat generation, the sulfur-based peroxide decomposer (C1) preferably contains, as the sulfur-containing ester compound, at least one selected from the group consisting of a sulfur-containing ester compound (C1-1) represented by the following general formula (1) and a sulfur-containing ester compound (C1-2) represented by the following general formula (2), and more preferably contains both the sulfur-containing ester compound (C1-1) and the sulfur-containing ester compound (C1-2).

[0039] (In formula (1), m and n are each independently an integer of 1 to 4, and R １ and R ２ are each independently a hydrocarbon group having 12 to 32 carbon atoms.

[0040] (In formula (2), m and n each independently represent an integer of 1 to 4, and R ３ is a hydrocarbon group having 12 to 32 carbon atoms.

[0041] In formula (1), m and n each independently represent an integer of 1 to 4, and from the viewpoint of suppressing heat generation, preferably 2 to 3. １ and R ２ are each independently a hydrocarbon group having 12 to 32 carbon atoms, and from the viewpoint of suppressing heat generation, the upper limit of the number of carbon atoms is preferably 30, more preferably 26, and even more preferably 22. On the other hand, the lower limit of the number of carbon atoms is preferably 12, more preferably 13, and even more preferably 14. Also, for example, 12 to 30 is more preferable, and 14 to 22 is even more preferable.

[0042] In formula (2), m and n each independently represent an integer of 1 to 4, and from the viewpoint of suppressing heat generation, preferably 2 to 3. ３ is a hydrocarbon group having 12 to 32 carbon atoms, and from the viewpoint of suppressing heat generation, the upper limit of the number of carbon atoms is preferably 30, more preferably 26, and even more preferably 22. On the other hand, the lower limit of the number of carbon atoms is preferably 12, more preferably 13, and even more preferably 14. Also, for example, 12 to 30 is more preferable, and 14 to 22 is more preferable.

[0043] The sulfur-based peroxide decomposer (C1) is a compound represented by the formula (1) R １ and the R ２ are each independently a hydrocarbon group having 14 to 22 carbon atoms, and ３ is a hydrocarbon group having 14 to 22 carbon atoms, and １ and the R ２ are each independently a hydrocarbon group having 14 to 22 carbon atoms, and ３ It is more preferable that the compound contains a hydrocarbon group having 14 to 22 carbon atoms.

[0044] The sulfur-containing ester compound (C1-1) is not particularly limited as long as it is a compound represented by formula (1). From the viewpoint of suppressing heat generation, preferred are di-linear thiodiethanoic acid esters such as di(n-dodecyl)thiodiethanate, di(n-tridecyl)thiodiethanate, di(n-tetradecyl)thiodiethanate, di(n-pentadecyl)thiodiethanate, and di(n-hexadecyl)thiodiethanate; di(isododecyl)thiodiethanate, di(isotridecyl)thiodiethanate, di(isotetradecyl)thiodiethanate, and di(isopentadecyl)thiodiethanate; di-branched esters of thiodiethanoic acid such as di(n-dodecyl)thiodipropionate, di(n-tridecyl)thiodipropionate, di(n-tetradecyl)thiodipropionate, di(n-pentadecyl)thiodipropionate, di(n-hexadecyl)thiodipropionate, and di(oleyl)thiodipropionate; di-linear esters of thiodipropionic acid such as di(isododecyl)thiodipropionate and di(isotridecyl)thiodipropionate di-branched esters of thiodipropionic acid such as di(n-dodecyl)thiodibutanate, di(n-tridecyl)thiodibutanate, di(n-tetradecyl)thiodibutanate, di(n-pentadecyl)thiodibutanate, di(n-hexadecyl)thiodibutanate; di-linear esters of thiodibutanoic acid such as di(isododecyl)thiodibutanate, di(isotetradecyl)thiodipropionate, di(isopentadecyl)thiodipropionate, di(isohexadecyl)thiodipropionate, and di(2-hexyldecyl)thiodipropionate; di-linear esters of thiodibutanoic acid such as di(n-dodecyl)thiodibutanate, di(n-tridecyl)thiodibutanate, di(n-tetradecyl)thiodibutanate, di(n-pentadecyl)thiodibutanate, and di(n-hexadecyl)thiodibutanate; di(isododecyl)thiodibutanoic acid branched-chain thiodibutanoic acid diesters such as di(n-dodecyl)thiodipentanate, di(n-tridecyl)thiodipentanate, di(n-tetradecyl)thiodibutanate, di(n-pentadecyl)thiodibutanate, di(isohexadecyl)thiodibutanate, and di(2-hexyldecyl)thiodibutanate; linear-chain thiodipentanoic acid diesters such as di(n-dodecyl)thiodipentanate, di(n-tridecyl)thiodipentanate, di(n-tetradecyl)thiodipentanate, di(n-pentadecyl)thiodipentanate, and di(n-hexadecyl)thiodipentanate;Examples of suitable thiodipentanoic acid dibranched esters include di(isododecyl)thiodipentanate, di(isotridecyl)thiodipentanate, di(isotetradecyl)thiodipentanate, di(isopentadecyl)thiodipentanate, di(isohexadecyl)thiodipentanate, and di(2-hexyldecyl)thiodipentanate. Among these, from the viewpoints of sizing ability and operability during firing, preferred are dilinear thiodipropionic acid esters and dibranched thiodipropionic acid esters, with di(n-dodecyl)thiodipropionate, di(2-hexyldecyl)thiodipropionate, di(oleyl)thiodipropionate, and di(behenyl)thiodipropionate being more preferred.

[0045] The sulfur-containing ester compound (C1-2) is not particularly limited as long as it is a compound represented by formula (2). From the viewpoint of suppressing heat generation, preferred are thiodiethanoic acid mono-linear esters such as thiodiethanoic acid mono(n-dodecyl) ester, thiodiethanoic acid mono(n-tridecyl) ester, thiodiethanoic acid mono(n-tetradecyl) ester, thiodiethanoic acid mono(n-pentadecyl) ester, and thiodiethanoic acid mono(n-hexadecyl) ester; thiodiethanoic acid mono(isododecyl) ester, thiodiethanoic acid mono(isotridecyl) ester, and thiodiethanoic acid mono(isotetradecyl) ester. thiodiethanoic acid mono-branched esters such as thiodiethanoic acid mono(isopentadecyl) ester, thiodiethanoic acid mono(isohexadecyl) ester, and thiodiethanoic acid mono(2-hexyldecyl) ester; thiodipropionic acid mono(n-dodecyl) ester, thiodipropionic acid mono(n-tridecyl) ester, thiodipropionic acid mono(n-tetradecyl) ester, thiodipropionic acid mono(n-pentadecyl) ester, thiodipropionic acid mono(n-hexadecyl) ester, and thiodipropionic acid mono(oleyl) ester. thiodipropionic acid mono-linear esters such as esters; thiodipropionic acid mono-branched esters such as thiodipropionic acid mono(isododecyl) ester, thiodipropionic acid mono(isotridecyl) ester, thiodipropionic acid mono(isotetradecyl) ester, thiodipropionic acid mono(isopentadecyl) ester, thiodipropionic acid mono(isohexadecyl) ester, and thiodipropionic acid mono(2-hexyldecyl) ester; thiodibutanoic acid mono(n-dodecyl) ester, thiodibutanoic acid mono(n-tridecyl) ester, thiodi Linear thiodibutanoic acid monoesters such as butanoic acid mono(n-tetradecyl) ester, thiodibutanoic acid mono(n-pentadecyl) ester, and thiodibutanoic acid mono(n-hexadecyl) ester; branched thiodibutanoic acid monoesters such as thiodibutanoic acid mono(isododecyl) ester, thiodibutanoic acid mono(isotridecyl) ester, thiodibutanoic acid mono(isotetradecyl) ester, thiodibutanoic acid mono(isopentadecyl) ester, thiodibutanoic acid mono(isohexadecyl) ester, and thiodibutanoic acid mono(2-hexyldecyl) ester;

[0033] Examples of the thiodipentanoic acid monoester include linear thiodipentanoic acid mono(n-dodecyl)ester, mono(n-tridecyl)ester, mono(n-tetradecyl)ester, mono(n-pentadecyl)ester, and mono(n-hexadecyl)ester; and branched thiodipentanoic acid monoester such as mono(isododecyl)ester, mono(isotridecyl)ester, mono(isotetradecyl)ester, mono(isopentadecyl)ester, mono(isohexadecyl)ester, and mono(2-hexyldecyl)ester. Among these, from the viewpoints of sizing ability and operability during firing, linear thiodipropionic acid monoesters and branched thiodipropionic acid monoesters are preferred, and mono(n-dodecyl) thiodipropionic acid ester, mono(2-hexyldecyl) thiodipropionic acid ester, mono(oleyl) thiodipropionic acid ester, and mono(behenyl) thiodipropionic acid ester are more preferred.

[0046] The phosphorus-based peroxide decomposer (C2) is not particularly limited, but a phosphite ester is preferred in terms of suppressing heat generation.

[0047] Examples of the phosphorus-based peroxide decomposer (C2) include di(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, 2,2'-methylenebis(4,6-di-t-butylphenyl)2-ethylhexyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, tetra(C12 to C15 alkyl)-4,4'-isopropylidene diphenyl diphosphite, di Phenyl mono(2-ethylhexyl)phosphite, diphenyl isodecyl phosphite, tris(isodecyl)phosphite, triphenyl phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4-biphenyl diphosphonate, tris(tridecyl)phosphite, phenyl isooctyl phosphite, phenyl isodecyl phosphite, phenyl di(tridecyl) phosphite, diphenyl isooctyl phosphite, diphenyl tridecyl phosphite, 4,4'-isopropyl propylidenediphenol alkyl phosphite, trisnonylphenyl phosphite, trisdinonylphenyl phosphite, tris(biphenyl) phosphite, di(2,4-di-t-butylphenyl)pentaerythritol diphosphite, di(nonylphenyl)pentaerythritol diphosphite, phenyl bisphenol A pentaerythritol diphosphite, tetratridecyl 4,4'-butylidenebis(3-methyl-6-t-butylphenol) diphosphite, hexatridecyl Examples of suitable phosphate compounds include ethyl 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane triphosphite, 3,5-di-t-butyl-4-hydroxybenzyl phosphite diethyl ester, sodium bis(4-t-butylphenyl)phosphite, sodium 2,2-methylene-bis(4,6-di-t-butylphenyl)-phosphite, 1,3-bis(diphenoxyphosphonyloxy)-benzene, and ethyl bis(2,4-di-t-butyl-6-methylphenyl)phosphite.

[0048] [Nonionic Surfactant (D)] The treatment agent of the present invention preferably contains a nonionic surfactant (D) in terms of emulsifying properties and penetration. Examples of nonionic surfactants include polyoxyalkylene linear alkyl ethers such as polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, and polyoxyethylene cetyl ether; polyoxyalkylene branched primary alkyl ethers such as polyoxyethylene 2-ethylhexyl ether, polyoxyethylene isocetyl ether, and polyoxyethylene isostearyl ether; polyoxyalkylene secondary alkyl ethers such as polyoxyethylene 1-hexylhexyl ether, polyoxyethylene 1-octylhexyl ether, polyoxyethylene 1-hexyloctyl ether, polyoxyethylene 1-pentylheptyl ether, and polyoxyethylene 1-heptylpentyl ether; polyoxyalkylene alkenyl ethers such as polyoxyethylene oleyl ether; polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, and polyoxyethylene dodecylphenyl ether. polyoxyalkylene alkylphenyl ethers such as polyoxyethylene tristyrylphenyl ether, polyoxyethylene distyrylphenyl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene tribenzylphenyl ether, polyoxyethylene dibenzylphenyl ether, polyoxyethylene benzylphenyl ether; polyoxyalkylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monooleate, polyoxyethylene monostearate, polyoxyethylene monomyristate, polyoxyethylene dilaurate, polyoxyethylene diolate, polyoxyethylene dimyristate, polyoxyethylene distearate; sorbitan esters such as sorbitan monopalmitate and sorbitan monolaurate; polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monostearate and polyoxyethylene sorbitan monolaurate;Glycerin fatty acid esters such as glycerin monostearate, glycerin monolaurate, and glycerin monopalmitate; polyglycerin fatty acid esters such as diglycerin monocaprylate, tetraglycerin monolaurate, hexaglycerin tristearate, decaglycerin monomyristate, decaglycerin monostearate, decaglycerin tristearate, and decaglycerin decastearate; polyoxyalkylene sorbitol fatty acid esters; sucrose fatty acid esters; polyoxyalkylene hydrogenated castor oil ethers such as polyoxyethylene hydrogenated castor oil ether; polyoxyalkylene alkylamino ethers such as polyoxyethylene lauryl amino ether and polyoxyethylene stearyl amino ether; oxyethylene-oxy Examples of suitable polyoxyethylene-oxypropylene block or random copolymers include oxyethylene-oxypropylene block or random copolymers with terminal alkyl ethers; oxyethylene-oxypropylene block or random copolymers with terminal sucrose ethers; polyoxyalkylene alkylamides such as polyoxyethylene laurylamide and polyoxyethylene stearylamide; and polyoxyalkylene 4 to 60 mole adducts of bisphenols, such as a 4 mole polyoxyethylene adduct of bisphenol A, a 10 mole polyoxyethylene adduct of bisphenol A, a 30 mole polyoxyethylene adduct of bisphenol A, a 60 mole polyoxyethylene adduct of bisphenol A, and a 10 mole polyoxyethylene adduct of bisphenol F.

[0049] Among these nonionic surfactants, polyoxyalkylene branched primary alkyl ethers, polyoxyalkylene secondary alkyl ethers, polyoxyalkylene alkenyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene hydrogenated castor oil ethers, polyoxyalkylene fatty acid esters, oxyethylene-oxypropylene block copolymers, and terminal alkyl etherified products of oxyethylene-oxypropylene block copolymers are preferred in terms of their ability to uniformly impart sizing properties to fibers, and polyoxyalkylene branched primary alkyl ethers, polyoxyalkylene secondary alkyl ethers, polyoxyalkylene hydrogenated castor oil ethers, oxyethylene-oxypropylene block or random copolymers, and terminal alkyl etherified products of oxyethylene-oxypropylene block copolymers are more preferred. The number of moles of alkylene oxide added in the nonionic surfactant is preferably 3 to 40 moles in terms of emulsifying properties and penetrating properties. The upper limit of the number of moles added is more preferably 35 moles, even more preferably 30 moles, and particularly preferably 25 moles. On the other hand, the lower limit of the number of moles added is more preferably 5 moles, even more preferably 7 moles, and particularly preferably 9 moles. Also, for example, it is more preferably 5 moles to 35 moles, and even more preferably 7 moles to 30 moles.

[0050] [Bronsted Acid Compound] The treatment agent of the present invention preferably contains a Bronsted acid compound in terms of the stability of the treatment agent in an aqueous system. The Bronsted acid compound refers to a proton donor, and examples thereof include organic carboxylic acid compounds, inorganic acids, organic sulfonic acid compounds, organic phosphate ester compounds, organic sulfate ester compounds, and organic phosphonic acid compounds. As the Bronsted acid compound, it is preferable to use, for example, those described in International Publication No. 2018 / 163739.

[0051] [Other Surfactants] The treatment agent of the present invention may contain other surfactants. Examples of other surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. It is preferable to contain an anionic surfactant in order to impart uniform sizing properties.

[0052] Examples of anionic surfactants include fatty acids (salts) such as 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). ); N-acyl sarcosinic acids (salts) such as lauroyl sarcosinic 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); 2-ethylhexyl sulf alkyl sulfates (salts) such as polyoxyethylene 2-ethylhexyl ether sulfate (sodium salt); polyoxyalkylene sulfates (salts) such as polyoxyethylene 2-ethylhexyl ether sulfate (sodium salt); long-chain sulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate and sodium dioctyl sulfosuccinate; long-chain N-acyl glutamates such as sodium monosodium N-lauroyl glutamate and disodium N-stearoyl-L-glutamate; and the like.

[0053] 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.

[0054] 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.

[0055] [Treatment agent for carbon fiber precursor] The treatment agent for carbon fiber precursor of the present invention contains a smoothing component (A), a radical scavenger (B), and a peroxide decomposer (C). The mechanism by which the treatment agent for carbon fiber precursor of the present invention can impart excellent single-fiber breakage suppression properties to the carbon fiber precursor in the flame-resistant treatment step is not particularly limited, but it is thought that this is because, by uniformly adhering the radical scavenger (B) and the peroxide decomposer (C) to the surface of the carbon fiber precursor, the rapid heat generation accompanying the oxidation reaction and cyclization reaction of the precursor in the flame-resistant treatment step can be suppressed and the oxidative decomposition of the precursor can be made mild, and further, by uniformly adhering the smoothing component (A) to the surface of the precursor, it is possible to impart sizing properties to the precursor in the flame-resistant treatment step and reduce the frictional force when it comes into contact with a metal roller.

[0056] The proportion of the smoothing component (A) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of sizing ability, it is preferably 10 to 95% by weight. The upper limit of this proportion is more preferably 95% by weight, even more preferably 90% by weight, and particularly preferably 80% by weight. Meanwhile, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Furthermore, for example, 15 to 90% by weight is more preferable, and 20 to 80% by weight is particularly preferable. The non-volatile content concentration in the present invention is determined by spreading 2.0 to 3.0 g of the treatment agent evenly on an aluminum sheet (φ110 mm), drying at 110°C under irradiation with an infrared lamp, accurately weighing the weight of the residue on the aluminum sheet when the fluctuation range of the volatile content over 150 seconds is 0.15%, and calculating the ratio (percentage) of the remaining weight after heating to the weight before heating. The non-volatile content in the present invention refers to the residue on the aluminum sheet when the fluctuation range of the volatile content over 150 seconds is 0.15%, which was determined in the same manner as in the non-volatile content concentration measurement procedure.

[0057] The proportion of the amino group-containing silicone (A1) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 10 to 95% by weight from the viewpoint of preventing fusion between fibers. The upper limit of this proportion is more preferably 95% by weight, even more preferably 90% by weight, and particularly preferably 80% by weight. Meanwhile, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Furthermore, for example, 15 to 90% by weight is more preferred, and 20 to 80% by weight is particularly preferred.

[0058] The proportion of the ester compound (A2) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of sizing ability, it is preferably 10 to 95% by weight. The upper limit of this proportion is more preferably 95% by weight, even more preferably 90% by weight, and particularly preferably 80% by weight. On the other hand, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Furthermore, for example, 15 to 90% by weight is more preferable, and 20 to 80% by weight is particularly preferable.

[0059] The proportion of the radical scavenger (B) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 30% by weight. The upper limit of this proportion is more preferably 30% by weight, even more preferably 25% by weight, and particularly preferably 20% by weight. Meanwhile, the lower limit of this proportion is more preferably 0.1% by weight, even more preferably 0.5% by weight, and particularly preferably 3.0% by weight. Furthermore, for example, 0.5% by weight to 25% by weight is more preferable, and 3.0% by weight to 20% by weight is particularly preferable.

[0060] The proportion of the phenolic radical scavenger (B1) in the non-volatile content of the treating agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 30 wt%. The upper limit of this proportion is more preferably 30 wt%, even more preferably 25 wt%, and particularly preferably 20 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 25 wt% is more preferable, and 3.0 wt% to 20 wt% is particularly preferable.

[0061] The proportion of the aromatic amine radical scavenger (B2) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 30 wt%. The upper limit of this proportion is more preferably 30 wt%, even more preferably 25 wt%, and particularly preferably 20 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 25 wt% is more preferable, and 3.0 wt% to 20 wt% is particularly preferable.

[0062] The proportion of the peroxide decomposer (C) in the non-volatile content of the treating agent of the present invention is not particularly limited, but is preferably 0.1 to 60% by weight from the viewpoint of suppressing heat generation. The upper limit of this proportion is more preferably 60% by weight, even more preferably 55% by weight, and particularly preferably 50% by weight. Meanwhile, the lower limit of this proportion is more preferably 0.1% by weight, even more preferably 0.5% by weight, and particularly preferably 3.0% by weight. Furthermore, for example, 0.5% by weight to 55% by weight is more preferable, and 3.0% by weight to 50% by weight is particularly preferable.

[0063] The proportion of the sulfur-based peroxide decomposer (C1) in the non-volatile content of the treating agent of the present invention is not particularly limited, but is preferably 0.1 to 60 wt% from the viewpoint of suppressing heat generation. The upper limit of this proportion is more preferably 60 wt%, even more preferably 55 wt%, and particularly preferably 50 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 55 wt% is more preferable, and 3.0 wt% to 50 wt% is particularly preferable.

[0064] The proportion of the phosphorus-based peroxide decomposer (C2) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 0.1 to 60 wt% from the viewpoint of suppressing heat generation. The upper limit of this proportion is more preferably 60 wt%, even more preferably 55 wt%, and particularly preferably 50 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 55 wt% is more preferable, and 3.0 wt% to 50 wt% is particularly preferable.

[0065] The proportion of the sulfur-containing ester compound (C1-1) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 60 wt%. The upper limit of this proportion is more preferably 60 wt%, even more preferably 55 wt%, and particularly preferably 50 wt%. On the other hand, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 55 wt% is more preferable, and 3.0 wt% to 50 wt% is particularly preferable.

[0066] The proportion of the sulfur-containing ester compound (C1-2) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 60 wt%. The upper limit of this proportion is more preferably 60 wt%, even more preferably 55 wt%, and particularly preferably 50 wt%. On the other hand, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 55 wt% is more preferable, and 3.0 wt% to 50 wt% is particularly preferable.

[0067] The total proportion of the sulfur-containing ester compound (C1-1) and the sulfur-containing ester compound (C1-2) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 60 wt%. The upper limit of this proportion is more preferably 60 wt%, even more preferably 55 wt%, and particularly preferably 50 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.1 wt%, even more preferably 0.5 wt%, and particularly preferably 3.0 wt%. Furthermore, for example, 0.5 wt% to 55 wt% is more preferable, and 3.0 wt% to 50 wt% is particularly preferable.

[0068] The R in the general formula (1) accounts for the nonvolatile content of the treatment agent of the present invention. １ and the R ２ are each independently a hydrocarbon group having 14 to 22 carbon atoms, and ３The total proportion of compounds in which is a hydrocarbon group having 14 to 22 carbon atoms is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.1 to 60% by weight. The upper limit of this proportion is more preferably 60% by weight, even more preferably 55% by weight, and particularly preferably 50% by weight. On the other hand, the lower limit of this proportion is more preferably 0.1% by weight, even more preferably 0.5% by weight, and particularly preferably 3.0% by weight. Furthermore, for example, 0.5 to 55% by weight is more preferable, and 3.0 to 50% by weight is particularly preferable.

[0069] The weight ratio ((C1-1) / (C1-2)) of the sulfur-containing ester compound (C1-1) to the sulfur-containing ester compound (C1-2) is not particularly limited, but is preferably 1 to 10,000 from the viewpoint of suppressing heat generation. The upper limit of this ratio is more preferably 10,000, even more preferably 200, and particularly preferably 100. On the other hand, the lower limit of this ratio is more preferably 1, even more preferably 1.5, and particularly preferably 2.5. Furthermore, for example, it is more preferably 1.5 to 200, and particularly preferably 2.5 to 100.

[0070] The total proportion of the radical scavenger (B) and peroxide decomposer (C) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 0.5 wt% or more from the viewpoint of suppressing heat generation. The upper limit of this proportion is preferably 50 wt%, more preferably 40 wt%, even more preferably 30 wt%, and particularly preferably 20 wt%. Meanwhile, the lower limit of this proportion is more preferably 0.5 wt%, even more preferably more than 5 wt%, and particularly preferably 7 wt%. Furthermore, for example, more than 5 wt% is more preferable, more preferably more than 5 wt% to 30 wt%, and particularly preferably 7 wt% to 20 wt%.

[0071] The weight ratio ((B) / (C)) of the radical scavenger (B) to the peroxide decomposer (C) is not particularly limited, but is preferably 0.01 to 1 from the viewpoint of suppressing heat generation. The upper limit of this ratio is more preferably 1, even more preferably 0.49, and particularly preferably 0.33. On the other hand, the lower limit of this ratio is more preferably 0.01, even more preferably 0.02, and particularly preferably 0.04. Furthermore, for example, a range of 0.02 to 0.49 is more preferable, and a range of 0.04 to 0.33 is particularly preferable.

[0072] The weight ratio ((B) / (A)) of the radical scavenger (B) to the smoothing component (A) is not particularly limited, but is preferably 0.0001 to 0.1 from the viewpoint of suppressing heat generation. The upper limit of this ratio is more preferably 0.1, even more preferably 0.05, and particularly preferably 0.01. On the other hand, the lower limit of this ratio is more preferably 0.0001, even more preferably 0.0005, and particularly preferably 0.001. Furthermore, for example, a range of 0.005 to 0.05 is more preferable, and a range of 0.001 to 0.01 is particularly preferable.

[0073] The weight ratio ((C) / (A)) of the peroxide decomposer (C) to the smoothing component (A) is not particularly limited, but from the viewpoint of suppressing heat generation, it is preferably 0.001 to 1. The upper limit of this ratio is more preferably 1, even more preferably 0.5, and particularly preferably 0.1. On the other hand, the lower limit of this ratio is more preferably 0.001, even more preferably 0.003, and particularly preferably 0.005. Furthermore, for example, a range of 0.003 to 0.5 is more preferable, and a range of 0.005 to 0.1 is particularly preferable.

[0074] The weight ratio of the smoothing component (A) to the total of the radical scavenger (B) and the peroxide decomposer (C), ((A) / ((B)+(C))), is not particularly limited, but is preferably 1 to 99 from the viewpoint of suppressing heat generation. The upper limit of this ratio is more preferably 99, even more preferably 90, and particularly preferably 85. On the other hand, the lower limit of this ratio is more preferably 1, even more preferably 3, and particularly preferably 5. Furthermore, for example, a ratio of 3 to 90 is more preferable, and a ratio of 5 to 85 is particularly preferable.

[0075] The proportion of the nonionic surfactant (D) in the nonvolatile content of the treatment agent of the present invention is not particularly limited, but is preferably 1 to 50% by weight from the viewpoint of imparting uniform sizing properties to fibers. The upper limit of this proportion is more preferably 50% by weight, even more preferably 40% by weight, and particularly preferably 30% by weight. Meanwhile, the lower limit of this proportion is more preferably 1% by weight, even more preferably 3% by weight, and particularly preferably 5% by weight. Furthermore, for example, 3% by weight to 40% by weight is more preferable, and 5% by weight to 30% by weight is particularly preferable.

[0076] [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 antistatic agents, antibacterial agents, preservatives, rust inhibitors, and moisture absorbents.

[0077] 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 substituted. These low molecular weight silicones may be contained as a trace component of the silicone compound. The content of the low molecular weight silicone in the treatment agent of the present invention is preferably 5 parts by weight or less per 100 parts by weight of the silicone compound.

[0078] The carbon fiber precursor treatment agent of the present invention is preferably in a state in which the components of the treatment agent, including the smoothing component (A), the radical scavenger (B), and the peroxide decomposer (C), are dissolved, solubilized, emulsified, or dispersed in water. The weight percentages of water and nonvolatile matter in the entire carbon fiber precursor treatment agent are not particularly limited. These may be appropriately determined taking into consideration, for example, the transportation costs for transporting the carbon fiber precursor treatment agent of the present invention and the ease of handling due to the emulsion viscosity. The weight percentage of water in the entire carbon fiber precursor treatment agent is preferably 0.1 to 99.9 wt %, more preferably 10 to 99.5 wt %, and particularly preferably 50 to 99 wt %. The weight percentage (concentration) of nonvolatile matter in the entire carbon fiber precursor treatment agent is preferably 0.01 to 99.9 wt %. The upper limit of this percentage is more preferably 90 wt %, and even more preferably 50 wt %. On the other hand, the lower limit of the ratio is preferably 0.5% by weight, more preferably 1% by weight, and even more preferably 5% by weight, more preferably 0.5 to 90% by weight, and even more preferably 1 to 50% by weight, for example.

[0079] 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.

[0080] The treating agent for carbon fiber precursors of the present invention can be suitably used as a treating agent for carbon fiber precursors.

[0081] [Carbon Fiber Precursor, Its Manufacturing Method, and Carbon Fiber Manufacturing Method] The carbon fiber precursor of the present invention is obtained by adhering the above-described carbon fiber precursor treating agent to a raw carbon fiber precursor of a carbon fiber precursor and spinning it into a fiber. The carbon fiber precursor manufacturing method of the present invention includes a spinning step in which the above-described carbon fiber precursor treating agent is adhered to a raw carbon fiber precursor of a carbon fiber precursor and spinning it into a fiber. The carbon fiber manufacturing method of the present invention includes a flame-resistant step in which the carbon fiber precursor having the above-described carbon fiber precursor treating agent adhered thereto is converted into a flame-resistant fiber, and a carbonization step in which the flame-resistant fiber is further carbonized. The flame-resistant step is preferably a flame-resistant step in which the carbon fiber precursor is converted into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C, and the carbonization step is preferably a step in which the flame-resistant fiber is further carbonized in an inert atmosphere at 300 to 2000°C. The carbon fiber manufacturing method of the present invention uses the carbon fiber precursor treating agent of the present invention, which provides excellent suppression of single fiber breakage in the flame-resistant step, thereby enabling the production of high-quality carbon fiber.

[0082] The spinning process is a process of spinning a carbon fiber precursor by adhering a treatment agent for a carbon fiber precursor to a raw material carbon fiber precursor of the carbon fiber precursor, and preferably includes an adhering process and a drawing process. The adhering process is a process of adhering a treatment agent for a carbon fiber precursor after spinning the raw material carbon fiber precursor of the carbon fiber precursor. That is, in the adhering process, the treatment agent for a carbon fiber precursor is adhered to the raw material carbon fiber precursor of the carbon fiber precursor. Furthermore, when the raw material carbon fiber precursor of the carbon fiber precursor is stretched immediately after spinning, the high-magnification drawing after the adhering process is particularly referred to as 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 raw material carbon fiber precursor immediately after spinning.

[0083] The carbon fiber precursor is not particularly limited as long as it is a precursor used in the production of carbon fibers, but is preferably composed of acrylic fibers whose main component is polyacrylonitrile obtained by copolymerizing at least 95 mol% or more of acrylonitrile and 5 mol% or less of a flame retardant-promoting component. A vinyl group-containing compound copolymerizable with acrylonitrile can be suitably used as the flame retardant-promoting component. The single fiber fineness of the carbon fiber precursor 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 fiber bundle of the carbon fiber precursor is also not particularly limited, but is preferably 1,000 to 96,000 in terms of the balance between performance and production costs.

[0084] The treating agent for carbon fiber precursors may be applied to the raw material carbon fiber precursor of the carbon fiber precursor at any stage in the spinning 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 again at any stage after the drawing process, for example, immediately after the drawing process, or at the winding stage, or immediately before the flame-resistant process. The application method may be by using a roller or the like, or by a dipping method, a spraying method, or the like.

[0085] 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 an effect of preventing fiber-to-fiber sticking and fusion, and preventing deterioration in the quality of the carbon fiber due to tar products of the treatment agent in the carbonization 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 content of the treatment agent for carbon fiber precursors adhered to the weight of the carbon fiber precursor.

[0086] The flame-resistant treatment is a process in which a carbon fiber precursor having a treatment agent for carbon fiber precursors attached thereto is converted into a flame-resistant fiber in an oxidizing atmosphere at, for example, 200 to 300°C. The oxidizing atmosphere may usually be an air atmosphere. The temperature of the oxidizing atmosphere is preferably 230 to 280°C. In the flame-resistant treatment, the carbon fiber precursor 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.

[0087] The carbonization step is a step in which the flame-resistant fiber is further carbonized in an inert atmosphere at, for example, 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] <Treatment Agent Application Rate> The application rate of the treatment agent for carbon fiber precursors was calculated by the ethanol extraction method using a Soxhlet extractor. However, for treatment agents containing silicone, the application rate was calculated using 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 application rate (wt%) of the carbon fiber precursor treatment agent was calculated using the silicon content determined here and the silicon content in the treatment agent previously determined by the same method.

[0092] <Number of fluffs after flame-proofing process> The number of fluffs after the flame-proofing process was determined by counting the number of fluffs of 2 mm or more at the outlet of the flame-proofing furnace when 1,000 m of the carbon fiber precursor was passed using a fluff counting device (manufactured by Toray Engineering Co., Ltd.). The number of fluffs was judged according to the following criteria, with ◎ and ○ being considered acceptable. ◎: 5 ​​or less ○: 6 to 10 △: 11 to 20 ×: 21 or more

[0093] <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).

[0094] <Preparation of a sample of non-volatile content of the treatment agent> 2.0 to 3.0 g of the treatment agent was spread evenly on an aluminum sheet (φ110 mm) and dried at 110°C under irradiation with an infrared lamp. When the fluctuation range of the volatile content over 150 seconds reached 0.15%, the residue on the aluminum sheet was taken as the non-volatile content of the treatment agent.

[0095] Example 1 A treatment agent for carbon fiber precursors having a nonvolatile content of 20 wt% was prepared by mixing and emulsifying a water-based emulsion of smoothing agent A-1, radical scavenger B-1, peroxide decomposer C-1, nonionic surfactants D-1, D-2, and D-3, and water so as to have the nonvolatile content composition of the treatment agent shown in Table 1. The weight percentage of smoothing agent A-1 in the nonvolatile content of the treatment agent was 79 wt%, the weight percentage of radical scavenger B-1 was 0.3 wt%, the weight percentage of peroxide decomposer C-1 was 0.7 wt%, the weight percentage of nonionic surfactant D-1 was 10 wt%, the weight percentage of nonionic surfactant D-2 was 5 wt%, and the weight percentage of nonionic surfactant D-3 was 5 wt%. The prepared treatment agent was then further diluted with water to obtain a diluted solution having a nonvolatile content of 3.0 wt%. The dilution solution was applied to a raw material carbon fiber precursor obtained by copolymerizing 97 mol% acrylonitrile and 3 mol% itaconic acid, so that the non-volatile content of the treatment agent was 1.0 wt%. The carbon fiber precursor was then subjected to a drawing process (steam drawing, draw ratio 2.1 times) to produce a carbon fiber precursor (single fiber fineness 0.8 dtex, 24,000 filaments). This carbon fiber precursor was flame-resistant treated in a 250°C flame-resistant furnace for 60 minutes, and then calcined in a carbonization furnace with a temperature gradient of 300 to 1400°C under a nitrogen atmosphere to convert it into carbon fiber. The results of evaluation of each property value are shown in Table 1.

[0096] [Examples 2 to 68, Comparative Examples 1 to 26] Treating agents for carbon fiber precursors, carbon fiber precursors, and carbon fibers were prepared and evaluated in the same manner as in Example 1, except that the treating agents were prepared so that the non-volatile compositions of the treating agents were as shown in Tables 1 to 7. The results of evaluation of each property value are shown in Tables 1 to 7.

[0097] The details of the nonvolatile composition in Tables 1 to 7 are as follows: <Smoothing Agent (A)> (A-1) Amino-modified silicone A-1: ​​Kinematic viscosity at 25°C: 1,300 mm ２ / s, amino equivalent: 2,000 g / mol, side chain amino-modified silicone (A-2) Amino-modified silicone A-2: 25°C kinematic viscosity: 120 mm ２ / s, amino equivalent: 5,000 g / mol, side chain amino-modified silicone (A-3) Polyether-modified silicone A-3: 25°C kinematic viscosity: 920 mm ２ / s, HLB: 10, EO / PO = 70 / 30 (molar ratio, EO is oxyethylene unit, PO is oxypropylene unit), side chain polyether modified silicone (A-4) Isotridecyl trimellitate (A-5) Coconut oil

[0098] <Radical Scavenger (B)> (B-1) Triethylene glycol bis 3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] (B-2) Tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (B-3) 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid (B-4) N,N'-diphenyl-p-phenylenediamine (B-5) N-phenyl-2-naphthylamine (B-6) N,N'-diphenylquinone diimine

[0099] <Peroxide decomposer (C)> (C-1) Thiodipropionic acid diolate (C-2) Thiodipropionic acid monoolate (C-3) Thiodipropionic acid dilaurate (C-4) Thiodipropionic acid monolaurate (C-5) Tris(2,4-di-t-butylphenyl)phosphite (C-6) 2-2'-methylenebis(4,6-di-t-butylphenyl)octylphosphite

[0100] <Nonionic surfactants (D)> (D-1) POE (25) hydrogenated castor oil ether (D-2) POE (9) C12-15 secondary alkyl ether (D-3) POE (7) C12-15 secondary alkyl ether POE is polyoxyethylene, and the number in parentheses indicates the number of moles added.

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] As can be seen from Tables 1 to 7, the carbon fiber precursor treating agents of Examples 1 to 68 were treating agents for carbon fiber precursors containing a smoothing agent (A), a radical scavenger (B), and a peroxide decomposer (C), where the radical scavenger (B) was at least one selected from a phenol-based radical scavenger (B1) and an aromatic amine-based radical scavenger (B2), and the peroxide decomposer (C) was at least one selected from a sulfur-based peroxide decomposer (C1) and a phosphorus-based peroxide decomposer (C2), and therefore were able to impart excellent single-yarn breakage suppression properties to the carbon fiber precursor in the flame-stabilizing step. On the other hand, the carbon fiber precursor treating agents of Comparative Examples 1 to 26 were not treating agents for carbon fiber precursors according to the present invention, and therefore were unable to impart excellent single-yarn breakage suppression properties to the carbon fiber precursor in the flame-stabilizing step.

[0109] The treating agent for carbon fiber precursors of the present invention is a treating agent used in producing a treating agent for carbon fiber precursors, and is useful for producing high-quality carbon fibers. The treating agent for carbon fiber precursors of the present invention is treated 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 smoothing component (A), a radical scavenger (B), and a peroxide decomposer (C), wherein the radical scavenger (B) is at least one selected from a phenol-based radical scavenger (B1) and an aromatic amine-based radical scavenger (B2), and the peroxide decomposer (C) is at least one selected from a sulfur-based peroxide decomposer (C1) and a phosphorus-based peroxide decomposer (C2).

2. The treatment agent for carbon fiber precursors according to claim 1, wherein the sulfur-based peroxide decomposer (C1) comprises at least one selected from the group consisting of a sulfur-containing ester compound (C1-1) represented by the following general formula (1) and a sulfur-containing ester compound (C1-2) represented by the following general formula (2): (In formula (1), m and n are each independently an integer of 1 to 4, and R １ and R ２ are each independently a hydrocarbon group having 12 to 32 carbon atoms. (In formula (2), m and n each independently represent an integer of 1 to 4, and R ３ is a hydrocarbon group having 12 to 32 carbon atoms.

3. The sulfur-based peroxide decomposer (C1) is a compound represented by the formula (1) R １ and the R ２ are each independently a hydrocarbon group having 14 to 22 carbon atoms, and ３ The treating agent for carbon fiber precursors according to claim 2, comprising at least one compound selected from the group consisting of compounds in which 4. The treatment agent for carbon fiber precursors according to claim 2 or 3, wherein the sulfur-based peroxide decomposer (C1) contains the sulfur-containing ester compound (C1-1) and the sulfur-containing ester compound (C1-2).

5. The treatment agent for carbon fiber precursors according to any one of claims 1 to 4, wherein the weight ratio ((B) / (C)) of the radical scavenger (B) to the peroxide decomposer (C) is 0.49 or less.

6. The treatment agent for carbon fiber precursors according to any one of claims 1 to 5, wherein the total proportion of the radical scavenger (B) and the peroxide decomposer (C) in the non-volatile content of the treatment agent for carbon fiber precursors is more than 5.0 wt%.

7. The treatment agent for carbon fiber precursors according to any one of claims 1 to 6, wherein the smoothing component (A) contains at least one selected from the group consisting of an amino group-containing silicone (A1) and an ester compound (A2).

8. The treating agent for carbon fiber precursors according to any one of claims 1 to 7, which contains a nonionic surfactant (D).

9. A carbon fiber precursor obtained by adhering the treating agent for carbon fiber precursors according to any one of claims 1 to 8 to a raw material carbon fiber precursor of the carbon fiber precursor.

10. A method for producing carbon fiber, comprising a flame-retardant step of converting the carbon fiber precursor according to claim 9 into a flame-retardant fiber, and a carbonization step of carbonizing the flame-retardant fiber.

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