Treatment agent for carbon fiber precursor and usage thereof

Abstract

To provide a treatment agent for a carbon fiber precursor capable of imparting excellent convergence at a flame proofing step to a carbon fiber precursor manufactured through applying a treatment agent, and also to provide a carbon fiber precursor using the treatment agent and a method for producing a carbon fiber using the treatment agent.SOLUTION: A treatment agent for a carbon fiber precursor includes an ester compound (A) and a surfactant (B). The ester compound (A) is a compound having a structure including an esterification of an alcohol (X) having 5-40 carbon atoms and three or more hydroxyl groups, and a fatty acid (Y) including an unsaturated fatty acid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a treatment agent for carbon fiber precursors (hereinafter sometimes simply referred to as a treatment agent) and its use. 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. [Background technology]

[0002] Taking advantage of their excellent mechanical properties, carbon fibers are widely used as reinforcing fibers for composite materials with plastics called matrix resins in aerospace, sports, general industrial, and other applications. A common method for producing carbon fiber is to convert a 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 the carbonization process will be collectively referred to as the calcination process.) Conventionally, various treatment agents have been applied to the precursor to efficiently perform these calcination processes.

[0003] However, the treatment agent adhered to the precursor had problems such as adhesive matter derived from the treatment agent that fell off the fiber during the precursor manufacturing process causing the fiber to wrap around drying rollers or guides, resulting in yarn breakage and reducing operability, and scale derived from treatment agents such as silicon oxide generated in the flame-proofing process carried out in an oxidizing atmosphere and silicon nitride generated in the carbonization process using nitrogen as an inert gas, accumulating, reducing operability and operating efficiency and causing damage to the firing furnace. To avoid these problems, treatments using low-viscosity silicone compounds, treatments that combine aromatic compounds with amino-modified silicones, and treatments that contain aromatic esters as the main component have been proposed (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-46855 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-211240 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-143645 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when carbon fibers are produced using carbon fiber precursors to which such treatment agents have been applied, there has often been a problem that the fibers cannot pass the calcination step. The cause of this was investigated and it was found that interference with adjacent fiber bundles occurred due to insufficient bundling during the flame-proofing process. Therefore, an object of the present invention is to provide a treatment agent for carbon fiber precursors that can impart excellent sizing properties to carbon fiber precursors in a flame-resistant treatment step, a carbon fiber precursor using the treatment agent, and a method for producing carbon fibers using the carbon fiber precursor. [Means for solving the problem]

[0006] 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 specific ester compound (A) and a surfactant (B) can impart excellent sizing properties to the carbon fiber precursors in the flame-resistant treatment step.

[0007] That is, the treating agent for carbon fiber precursors of the present invention includes the following embodiments. <1> A treatment agent for carbon fiber precursors, comprising an ester compound (A) and a surfactant (B), The treatment agent for carbon fiber precursors, wherein the ester compound (A) is a compound having an esterified structure of an alcohol (X) having 5 to 40 carbon atoms and 3 or more hydroxyl groups and a fatty acid (Y) including an unsaturated fatty acid. <2> the ester compound (A) includes a compound having an ester structure of an alcohol (X) having 6 to 40 carbon atoms and 3 or more hydroxyl groups and the fatty acid (Y), <1> The treating agent for carbon fiber precursors according to claim 1. <3> the ester compound (A) includes a compound having an ester structure of an alcohol (X) having 5 to 40 carbon atoms and 4 or more hydroxyl groups and the fatty acid (Y), <1> or <2> The treating agent for carbon fiber precursors according to claim 1. <4> The ester compound (A) includes an ester compound having a hydroxyl group. <1> ~ <3> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <5> the ester compound (A) is a compound having an esterified structure of the alcohol (X) and the fatty acid (Y), in which the proportion of unsaturated fatty acids in the fatty acid (Y) is 15% by weight to 100% by weight; <1> ~ <4> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <6> The ester compound (A) includes an ester compound having two or more ester bonds in the molecule. <1> ~ <5> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <7> The ester compound (A) contains an ester compound having a molecular weight of 650 or more. <1> ~ <6> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <8> The proportion of the ester compound (A) in the non-volatile content of the treatment agent for carbon fiber precursors is 10 to 95% by weight, and the proportion of the surfactant (B) is 5 to 90% by weight. <1> ~ <7> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <9> the weight ratio (A / B) of the ester compound (A) to the surfactant (B) is 0.1 to 20; <1> ~ <8> The treating agent for a carbon fiber precursor according to any one of the preceding claims. <10> Carbon fiber precursor raw material carbon fiber precursor, <1> ~ <9> 1. A carbon fiber precursor having the treating agent for carbon fiber precursors according to any one of claims 1 to 9 adhered thereto. <11> <10> a flame-resistant step of converting the carbon fiber precursor according to claim 1 into a flame-resistant fiber; and a carbonization step of carbonizing the flame-resistant fiber. [Effects of the Invention]

[0008] The treating agent for carbon fiber precursors of the present invention can impart excellent sizing ability 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 sizing ability in the flame-resistant treatment step, and therefore high-quality carbon fiber can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[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. [Ester compound (A)] The treating agent of the present invention contains an ester compound (A). The ester compound (A) is not particularly limited as long as it is a compound having an esterified structure of an alcohol (X) having 5 to 40 carbon atoms and 3 or more hydroxyl groups and a fatty acid (Y) including an unsaturated fatty acid, and one or more types may be used.

[0010] The number of ester bonds that the ester compound (A) has in its molecule is not particularly limited, but from the viewpoint of sizing ability, it is preferable that it has two 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. Also, for example, 2 to 10 is more preferable, and 2 to 8 is even more preferable.

[0011] The number of hydroxyl groups in the molecule of the ester compound (A) 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. Also, for example, 0 to 10 is more preferable, and 1 to 8 is even more preferable.

[0012] The molecular weight of the ester compound (A) is not particularly limited, but from the viewpoint of sizing ability, it is preferably 650 or more. 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, it is more preferably 700 to 4500, and even more preferably 750 to 4000. 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.

[0013] The iodine value of the ester compound (A) is not particularly limited, but is preferably 20 or more from the viewpoint of focusing ability. The upper limit of the iodine value is preferably 130, more preferably 120, and even more preferably 110. On the other hand, the lower limit of the iodine value is more preferably 30, more preferably 40, and particularly preferably 50. Also, for example, 40 to 130 is more preferable, and 40 to 120 is even more preferable. The iodine value of the ester compound (A) refers to the iodine value of the entire ester compound (A), and when multiple ester compounds (A) are used, it means the iodine value of the entire mixture of the multiple ester compounds (A).

[0014] The alcohol (X) having 5 to 40 carbon atoms and 3 or more hydroxyl groups is not particularly limited, and known alcohols can be used. The number of carbon atoms in the alcohol (X) is preferably 6 or more and 40 or less from the viewpoint of convergence, and the upper limit of the number of carbon atoms is more preferably 35, even more preferably 30, and particularly preferably 20. On the other hand, the lower limit of the number of carbon atoms is more preferably 7, even more preferably 8, and particularly preferably 9. Furthermore, for example, the number of carbon atoms is more preferably 6 or more and 35 or less, and even more preferably 6 or more and 20 or less.

[0015] The number of hydroxyl groups possessed by the alcohol (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.

[0016] Any combination of preferable upper and lower limits for the number of carbon atoms and the number of hydroxyl groups in the alcohol (X) can be applied, but for example, alcohols having 5 to 40 carbon atoms and 3 to 20 hydroxyl groups, alcohols having 6 to 40 carbon atoms and 3 or more hydroxyl groups, alcohols having 5 to 40 carbon atoms and 4 or more hydroxyl groups, alcohols having 6 to 40 carbon atoms and 3 to 15 hydroxyl groups, alcohols having 5 to 40 carbon atoms and 4 to 15 hydroxyl groups, and alcohols having 6 to 40 carbon atoms and 4 to 12 hydroxyl groups are preferably used in terms of achieving the effects of the present application.

[0017] The alcohol (X) is not particularly limited, and specific examples thereof include trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, sorbitol, xylitol, mannitol, diglycerin, triglycerin, tetraglycerin, decaglycerin, an alkylene oxide adduct of trimethylolethane, an alkylene oxide adduct of trimethylolpropane, an alkylene oxide adduct of pentaerythritol, an alkylene oxide adduct of sorbitan, an alkylene oxide adduct of sorbitol, an alkylene oxide adduct of xylitol, an alkylene oxide adduct of mannitol, and an alkylene oxide adduct of diglycerin. Examples of the alcohol (X) include those obtained by adding an alkylene oxide to triglycerin, those obtained by adding an alkylene oxide to tetraglycerin, and those obtained by adding an alkylene oxide to decaglycerin. In terms of sizing ability, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, sorbitol, xylitol, mannitol, diglycerin, triglycerin, tetraglycerin, and decaglycerin are preferred, trimethylolpropane, sorbitan, sorbitol, mannitol, diglycerin, triglycerin, tetraglycerin, and decaglycerin are more preferred, and trimethylolpropane, sorbitan, sorbitol, triglycerin, tetraglycerin, and decaglycerin are particularly preferred. One or more types of alcohol (X) may be used.

[0018] The fatty acid (Y) is not particularly limited, but in terms of sizing ability and fuzz suppression, it preferably contains an unsaturated fatty acid having 4 to 24 carbon atoms. 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 preferable, and 8 to 20 is more preferable.

[0019] The unsaturated fatty acids contained in the fatty acid (Y) are not particularly limited, but examples thereof include crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, eicosenoic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, ricinoleic acid, etc. From the viewpoint of sizing ability and preventing fusion between fibers, crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, eicosenoic acid, linoleic acid, and arachidonic acid are preferred, with oleic acid and linoleic acid being particularly preferred. One or more types of fatty acid (Y) may be used.

[0020] The proportion of unsaturated fatty acids in the fatty acid (Y) is not particularly limited, but is preferably 15% to 100% by weight from the viewpoint of sizing ability. The upper limit of this proportion is more preferably 90% by weight, even more preferably 85% by weight, and particularly preferably 80% by weight. On the other hand, the lower limit of this proportion is more preferably 20% by weight, even more preferably 40% by weight, and particularly preferably 60% by weight. Also, for example, 20% to 100% by weight is more preferable, and 40% to 100% by weight is even more preferable.

[0021] The proportion of unsaturated fatty acids having 18 to 22 carbon atoms in the fatty acid (Y) is not particularly limited, but is preferably 15 to 100% by weight from the viewpoint of preventing fusion between fibers. The upper limit of this proportion is more preferably 90% by weight, even more preferably 85% by weight, and particularly preferably 80% by weight. Meanwhile, the lower limit of this proportion is more preferably 20% by weight, even more preferably 40% by weight, and particularly preferably 60% by weight. Also, for example, 20 to 100% by weight is more preferable, and 40 to 100% by weight is even more preferable.

[0022] The total proportion of oleic acid and linoleic acid in the fatty acid (Y) is not particularly limited, but is preferably 15% to 100% by weight from the viewpoint of preventing fusion between fibers. The upper limit of this proportion is more preferably 90% by weight, even more preferably 85% by weight, and particularly preferably 80% by weight. On the other hand, the lower limit of this proportion is more preferably 20% by weight, even more preferably 40% by weight, and particularly preferably 60% by weight. Also, for example, 20% to 100% by weight is more preferable, and 40% to 100% by weight is even more preferable. The proportion of unsaturated fatty acids in fatty acids (Y), the proportion of unsaturated fatty acids having 18 to 22 carbon atoms in fatty acids (Y), and the total proportion of oleic acid and linoleic acid in fatty acids (Y) refer to the proportion of each fatty acid in all fatty acids (Y) constituting the ester compound (A), and when multiple ester compounds (A) are used, they refer to the proportion of each fatty acid in all fatty acids (mixture) constituting the multiple ester compounds (A).

[0023] The ester compound (A) is not particularly limited as long as it is a compound having a structure in which the alcohol (X) and the fatty acid (Y) are esterified. From the viewpoint of sizing ability, sorbitan trioleate, pentaglycerin monooleate, pentaglycerin dioleate, pentaglycerin trioleate, decaglycerin monooleate, decaglycerin trioleate, decaglycerin pentaoleate, decaglycerin decaoleate, hexaglycerin trioleate, hexaglycerin pentaoleate, tetraglycerin trioleate, and tetraglycerin pentaoleate are preferred, and sorbitan trioleate, pentaglycerin dioleate, pentaglycerin trioleate, decaglycerin trioleate, decaglycerin pentaoleate, decaglycerin decaoleate, hexaglycerin trioleate, hexaglycerin pentaoleate, tetraglycerin trioleate, and tetraglycerin pentaoleate are more preferred.

[0024] The method for obtaining the ester compound (A) is not particularly limited, and it is possible to use an ester compound containing an unsaturated fatty acid as a constituent unit, which is generally available on the market, or a compound obtained by synthesizing an ester compound by a known method using a fatty acid containing an unsaturated fatty acid and a polyhydric alcohol, which is generally available on the market, through an esterification reaction.

[0025] [Surfactant (B)] The treating agent of the present invention contains a surfactant (B). The surfactant (B) is not particularly limited as long as it is a surfactant other than the ester compound (A), and known surfactants can be used. Examples include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. In terms of being able to uniformly impart sizing properties, it is preferable for the surfactant (B) to contain at least one selected from nonionic surfactants and anionic surfactants, and it is more preferable for the surfactant (B) to contain a nonionic surfactant.

[0026] 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; and polyoxyalkylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, and polyoxyethylene dodecylphenyl ether. esters; polyoxyalkylene alkylarylphenyl ethers such as polyoxyethylene tristyrylphenyl ether, polyoxyethylene distyrylphenyl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene tribenzylphenyl ether, polyoxyethylene dibenzylphenyl ether, and polyoxyethylene benzylphenyl ether; 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 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;Polyglycerol fatty acid esters such as diglycerol monocaprylate, tetraglycerol monolaurate, hexaglycerol tristearate, decaglycerol monomyristate, decaglycerol monostearate, decaglycerol tristearate, and decaglycerol 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-oxypropylene block or random copolymers; oxyethylene Examples of the oxyethylene-oxypropylene block or random copolymer with terminal alkyl etherification; oxyethylene-oxypropylene block or random copolymer with terminal sucrose etherification; polyoxyalkylene alkylamides such as polyoxyethylene laurylamide and polyoxyethylene stearylamide; and polyoxyalkylene 4-60 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.

[0027] 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 that they can 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. In terms of emulsifying ability and penetrability, the number of moles of alkylene oxide added to the nonionic surfactant is preferably 3 to 40. The upper limit of the number of moles added is more preferably 35, even more preferably 30, and particularly preferably 25. On the other hand, the lower limit of the number of moles added is more preferably 5, even more preferably 7, and particularly preferably 9.

[0028] 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). alkylphosphonic acids (salts) such as octylphosphonate (potassium salt); aromatic phosphonic acids (salts) such as phenylphosphonate (potassium salt); alkylphosphonic acid alkyl phosphate esters (salts) such as 2-ethylhexylphosphonate mono 2-ethylhexyl ester (potassium salt); nitrogen-containing alkylphosphonic acids (salts) such as aminoethylphosphonic 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); 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; and the like.

[0029] 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, and 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, and lauroylamidoethyl methyl diethyl ammonium methosulfate; alkylethenoxy quaternary ammonium salts such as dipalmityl polyethenoxyethyl ammonium chloride and distearyl polyethenoxymethyl ammonium chloride; alkylisoquinolinium salts such as lauryl isoquinolinium chloride; benzalkonium salts such as lauryl dimethylbenzyl ammonium chloride and stearyl dimethylbenzyl 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.

[0030] 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.

[0031] [Silicone compound (C)] The treatment agent of the present invention may contain a silicone compound (C). There are no particular limitations on the silicone compound (C) as long as it has an inorganic siloxane bond (-Si-O-Si-) in the main chain and an organic group in the side chain, but it is preferable for the silicone compound (C) to contain a silicone having an amino group in order to prevent fusion between fibers. The silicone compound (C) may contain silicones other than those having an amino group. Examples of other silicones include polyether-modified silicone, dimethyl silicone, epoxy-modified silicone, amide-modified silicone, alkyl-modified silicone, aralkyl-modified silicone, phenyl-modified silicone, silanol-modified silicone, carbinol-modified silicone, and mercapto-modified silicone, and in terms of achieving the effects of the present application, it is preferable to include at least one selected from polyether-modified silicone, dimethyl silicone, alkyl-modified silicone, phenyl-modified silicone, and aralkyl-modified silicone, and it is more preferable to include polyether-modified silicone, phenyl-modified silicone, and aralkyl-modified silicone. These other silicones can be known ones.

[0032] The silicone having an amino group is not particularly limited as long as it has an inorganic siloxane bond (-Si-O-Si-) in the main chain and an organic group having an amino group in 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 it is more preferable to include amino-modified silicones in terms of achieving the effects of the present application. One or more types of silicones having an amino group may be used. The aminopolyether-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).

[0033] The kinematic viscosity of the silicone having an amino group at 25°C is not particularly limited, but in terms of uniform adhesion to fibers, it is preferably 50 to 20,000 mm2 The upper limit of the kinematic viscosity is more preferably 15000 mm 2 / s, and 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, 150 to 10,000 mm 2 / s is even more preferable.

[0034] The amino group (including an organic group having an amino group), which is the modified group of the silicone having an amino group, may be bonded to a side chain of the silicone main chain, or to an end, or may be bonded to both, but from the viewpoint of protecting the fibers in the flame-proofing process, 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 process and forming a film with the treatment agent to protect the fibers, a monoamine type or a diamine type is preferred, and a diamine type is more preferred.

[0035] The amino equivalent of the silicone having an amino group 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, amino equivalent refers to the mass of the siloxane skeleton per amino or ammonium group. The unit of g / mol is the value converted to per 1 mol of amino or ammonium groups. Therefore, the smaller the amino equivalent value, the higher the proportion of amino or ammonium groups in the molecule.

[0036] The amino group-containing silicone 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 above amino equivalent refers to the amino equivalent of the entire amino group-containing silicones (mixture), and the above kinematic viscosity at 25°C refers to the kinematic viscosity of the entire amino group-containing silicones (mixture).

[0037] [Brønsted acid compounds] The treatment agent of the present invention preferably contains a Brønsted acid compound in terms of stability of the treatment agent in an aqueous system. The Brønsted 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.

[0038] The organic carboxylic acid compound refers to an organic compound having a carboxyl group in its molecular structure. Examples of the organic carboxylic acid compound include, but are not limited to, aliphatic monocarboxylic acids, alkyl ether carboxylic acids, aliphatic polycarboxylic acids, aromatic carboxylic acids, aromatic polycarboxylic acids, and amino acids.

[0039] Examples of aliphatic monocarboxylic acids include acetic acid, lactic acid, 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, isocetyl acid, margaric acid, stearic acid, isostearic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linolenic acid, arachidic acid, isoeicosalic acid, gadoleic acid, eicosenoic acid, docosanoic acid, isodocosanoic acid, erucic acid, tetracosanoic acid, isotetracosanoic acid, nervonic acid, cerotic acid, montanic acid, and melissic acid.

[0040] Examples of alkyl ether carboxylic acids include those in which the alkyl group has 8 to 18 carbon atoms and the number of moles of polyoxyalkylene added is 1 to 50. Examples of the alkyl group include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. Examples of the polyoxyalkylene group include polyoxyethylene, polyoxypropylene, and polyoxypolypropylene groups.

[0041] Aliphatic polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, and derivatives thereof.

[0042] The aromatic monocarboxylic acids include benzoic acid, cinnamic acid, naphthoic acid, toluic acid, and derivatives thereof.

[0043] Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and derivatives thereof.

[0044] An amino acid is a compound that has both an amino group and a carboxyl group in its molecular structure, and examples thereof include alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, proline, glycine, tyrosine, serine, threonine, cysteine, asparagine, glutamine, lysine, arginine, histidine, aspartic acid, and glutamic acid.

[0045] Inorganic acids are acids containing non-metallic atoms, such as sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.

[0046] Examples of the organic sulfonic acid compound include alkylbenzene sulfonic acid, polyoxyalkylene alkyl ether sulfonic acid, higher fatty acid amide sulfonic acid, alkyl sulfate monoester, and polyoxyalkylene sulfate monoester.

[0047] Examples of the organic phosphate ester compound include alkyl phosphate monoesters, alkyl phosphate diesters, polyoxyalkylene alkyl ether phosphate monoesters, polyoxyalkylene alkyl ether phosphate diesters, polyoxyalkylene alkyl phenyl ether phosphate monoesters, and polyoxyalkylene alkyl phenyl ether phosphate diesters.

[0048] Examples of the organic sulfate compound include alkyl sulfate, polyoxyalkylene alkyl sulfate, alkylphenyl sulfate, and polyoxyalkylene alkylphenyl sulfate.

[0049] Examples of the organic phosphonic acid compound include alkyl phosphonic acid, aromatic phosphonic acid, and polyoxyalkylene alkyl ether phosphonic acid.

[0050] The pKa of the Bronsted acid compound is preferably 0 to 7, more preferably 1 to 6.5, and even more preferably 2 to 6, from the viewpoint of the stability of the treatment agent in an aqueous system.

[0051] In terms of the stability of the treatment agent in an aqueous system, the Bronsted acid compound preferably includes at least one selected from an organic carboxylic acid compound, an inorganic acid, and an organic phosphate ester compound, more preferably includes at least one selected from lactic acid, an alkyl ether carboxylic acid, an organic phosphate ester compound, phosphoric acid, and acetic acid, and even more preferably includes at least one selected from an alkyl ether carboxylic acid, an organic phosphate ester compound, acetic acid, and phosphoric acid. One or more Bronsted acid compounds may be used.

[0052] [Treatment agent for carbon fiber precursor] The treating agent for carbon fiber precursors of the present invention contains an ester compound (A) and a surfactant (B). The reason why the treatment agent for carbon fiber precursors of the present invention can impart excellent sizing properties to carbon fiber precursors in the flame-resistant treatment process is believed to be that the ester compound (A), which is uniformly and evenly adhered to the fibers by the surfactant (B), reacts and thickens in the flame-resistant treatment process, thereby preventing the fibers from falling apart.

[0053] The proportion of the ester compound (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 90% by weight, even more preferably 80% by weight, and particularly preferably 70% by weight. Meanwhile, the lower limit of this weight proportion is more preferably 20% by weight, even more preferably 30% by weight, and particularly preferably 40% by weight. Also, for example, 20% by weight to 90% by weight is more preferable, and 30% by weight to 80% by weight is particularly preferable. The non-volatile content concentration in this invention is determined by spreading 2.0 to 3.0 g of the treatment agent evenly on an aluminum sheet (φ110 mm), drying it at 110°C under infrared lamp irradiation, 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 this 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.

[0054] 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 90% by weight from the viewpoint of imparting uniform sizing properties to fibers. The upper limit of this proportion is more preferably 80% by weight, even more preferably 70% by weight, and particularly preferably 60% by weight. Meanwhile, the lower limit of this weight proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Also, for example, 10% by weight to 80% by weight is more preferable, and 15% by weight to 70% by weight is particularly preferable.

[0055] The proportion of nonionic surfactant in the nonvolatile content of the treatment agent of the present invention is not particularly limited, but is preferably 5 to 90% by weight from the viewpoint of imparting uniform sizing properties to fibers. The upper limit of this proportion is more preferably 80% by weight, even more preferably 70% by weight, and particularly preferably 60% by weight. Meanwhile, the lower limit of this weight proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Furthermore, for example, 10% by weight to 80% by weight is more preferable, and 15% by weight to 70% by weight is particularly preferable.

[0056] The proportion of the silicone compound (C) in the nonvolatile content of the treatment agent of the present invention is preferably 0% by weight to 50% by weight, from the viewpoints of preventing fusion between fibers and improving spinning operability. The upper limit of this proportion is more preferably 45% by weight, even more preferably 40% by weight, particularly preferably 35% by weight, and most preferably 30% by weight. Meanwhile, the lower limit of this proportion is more preferably 5% by weight, even more preferably 10% by weight, and particularly preferably 15% by weight. Furthermore, for example, 0% by weight to 45% by weight is more preferable, 0% by weight to 40% by weight is even more preferable, and 0% by weight to 35% by weight is particularly preferable.

[0057] The proportion of silicone having an amino group in the nonvolatile content of the treatment agent of the present invention is preferably 0% by weight to 50% by weight, from the viewpoints of preventing fusion between fibers and operability in spinning. The upper limit of this proportion is more preferably 45% by weight, even more preferably 40% by weight, particularly preferably 35% by weight, and most preferably 30% by weight. Meanwhile, the lower limit of this proportion is more preferably 5% by weight, even more preferably 10% by weight, and particularly preferably 15% by weight. Furthermore, for example, 0% by weight to 45% by weight is more preferable, 0% by weight to 40% by weight is even more preferable, and 0% by weight to 35% by weight is particularly preferable.

[0058] When the treatment agent of the present invention further contains a Brønsted acid compound, the proportion of the Brønsted acid in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 0.01% to 10% by weight from the viewpoint of emulsion stability of the treatment agent. The upper limit of this proportion is more preferably 8% by weight, even more preferably 6% by weight, and particularly preferably 4% by weight. Meanwhile, the lower limit of this weight proportion is more preferably 0.05% by weight, even more preferably 0.10% by weight, and particularly preferably 0.20% by weight. Furthermore, for example, 0.05% to 8% by weight is more preferable, and 0.10% to 6% by weight is particularly preferable.

[0059] The weight ratio (A / B) of the ester compound (A) to the surfactant (B) is preferably 0.1 to 20 in order to provide uniform sizing properties to the fibers. The upper limit of this weight ratio is more preferably 18, even more preferably 16, and particularly preferably 14. On the other hand, the lower limit of this weight ratio is more preferably 0.5, even more preferably 1.0, and particularly preferably 2.0. Also, for example, it is more preferably 0.5 to 18, and even more preferably 1.0 to 16.

[0060] The viscosity of the nonvolatile content of the treatment agent of the present invention is not particularly limited, but is preferably 10,000 mPa·s or less in terms of imparting uniform sizing properties to fibers. The upper limit of the viscosity is more preferably 5,000 mPa·s, even more preferably 2,500 mPa·s, and particularly preferably 1,000 mPa·s. On the other hand, the lower limit of the viscosity is more preferably 50 mPa·s, even more preferably 75 mPa·s, and particularly preferably 100 mPa·s. Furthermore, for example, a range of 50 mPa·s to 5,000 mPa·s is more preferable, and 75 mPa·s to 2,500 mPa·s is particularly preferable. The method for measuring the viscosity of the nonvolatile content of the treatment agent refers to the method described in the Examples.

[0061] The acid value of the treatment agent of the present invention is preferably 20 mgKOH / g or less in terms of the stability of the treatment agent in an aqueous system. The upper limit of the acid value is more preferably 18 mgKOH / g, even more preferably 16 mgKOH / g, particularly preferably 14 mgKOH / g, and most preferably 12 mgKOH / g. Meanwhile, the lower limit of the acid value is more preferably 0.01 mgKOH / g, even more preferably 0.03 mgKOH / g, particularly preferably 0.05 mgKOH / g, and most preferably 0.07 mgKOH / g. Furthermore, for example, a range of 0.03 to 18 mgKOH / g is more preferable, and a range of 0.03 to 14 mgKOH / g is even more preferable. The acid value of the treatment agent of the present invention is a value calculated in accordance with JIS 0070:1992.

[0062] [Other ingredients] 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 phenol-based, amine-based, sulfur-based, phosphorus-based, and quinone-based antioxidants, antistatic agents, smoothing agents, antibacterial agents, preservatives, rust inhibitors, and moisture absorbents.

[0063] Examples of smoothing agents include ester compounds of aliphatic monoalcohols and aliphatic monocarboxylic acids, such as oleyl oleate, octyl stearate, octyl palmitate, and oleyl laurate; and triglycerides of coconut oil, soybean oil, linseed oil, sunflower oil, rapeseed oil, sesame oil, palm oil, and palm kernel oil.

[0064] 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 trace components of the silicone compound (C). 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 (C).

[0065] The treating agent for carbon fiber precursors of the present invention is preferably in a state in which the components of the treating agent, including the ester compound (A) and the surfactant (B), are dissolved, solubilized, emulsified, or dispersed in water. There are no particular limitations on the weight percentage of water and the weight percentage of nonvolatile matter in the entire carbon fiber precursor treatment agent. For example, these may be appropriately determined taking into consideration factors such as the transportation costs for transporting the carbon fiber precursor treatment agent of the present invention and the ease of handling due to 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%. Meanwhile, the lower limit of this percentage is preferably 0.5 wt%, preferably 1 wt%, and even more preferably 5 wt%. Furthermore, for example, 0.5 to 90 wt% is more preferably 0.5 to 50 wt%, and even more preferably 1 to 50 wt%.

[0066] 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 cause phase inversion emulsification. Alternatively, a method in which some components are emulsified and then the remaining components are dissolved and dispersed may be used.

[0067] The treating agent for carbon fiber precursors of the present invention can be suitably used as a treating agent for carbon fiber precursors.

[0068] [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-mentioned treating agent for carbon fiber precursors to a raw material carbon fiber precursor of the carbon fiber precursor, and spinning the resultant into a fiber. The method for producing a carbon fiber precursor of the present invention includes a spinning step of adhering the above-mentioned treating agent for carbon fiber precursors to a raw material carbon fiber precursor of the carbon fiber precursor, and spinning the resultant into a fiber. The method for producing a carbon fiber of the present invention includes a flame-retardant step of converting the carbon fiber precursor having the above-mentioned treatment agent for a carbon fiber precursor attached thereto into a flame-retardant fiber, and a carbonization step of further carbonizing the flame-retardant fiber. The flame-resistant process is preferably a process of converting a carbon fiber precursor into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C, and the carbonization process is preferably a process of further carbonizing the flame-resistant fiber in an inert atmosphere at 300 to 2000°C. According to the carbon fiber manufacturing method of the present invention, the treatment agent for carbon fiber precursor of the present invention is used, which improves bundling ability, reduces fiber bundle disorder and uneven drawing, and enables the production of high-quality carbon fibers.

[0069] The spinning step is a step of spinning the carbon fiber precursor by adhering a treatment agent for carbon fiber precursors to a raw material carbon fiber precursor of the carbon fiber precursor, and preferably includes an adhering treatment step and a drawing step. The adhesion treatment step is a step of adhering a treatment agent for a carbon fiber precursor after spinning the raw carbon fiber precursor of the carbon fiber precursor. That is, in the adhesion treatment step, the treatment agent for a carbon fiber precursor is adhered to the raw carbon fiber precursor of the carbon fiber precursor. When the raw carbon fiber precursor of the carbon fiber precursor is stretched immediately after spinning, the high-magnification stretching after the adhesion treatment step is particularly called the "stretching step." The stretching step may be a wet heat stretching method using high-temperature steam, or a dry heat stretching method using a heated roller. The stretching ratio in the stretching step is preferably 2 to 20 times the total stretching ratio of the raw carbon fiber precursor immediately after spinning.

[0070] 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 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 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.

[0071] 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.

[0072] 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.

[0073] 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 is usually 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.

[0074] 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, a preliminary carbonization step (first carbonization step) is preferably performed by heat-treating the flame-resistant fiber 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 the second carbonization step, thereby carbonizing the flame-resistant fiber. The heat treatment temperature in the second carbonization step is preferably controlled by applying a temperature gradient and setting the maximum temperature to 1000°C or higher (preferably 1000 to 2000°C). This maximum temperature is appropriately selected and determined depending on the desired properties (tensile strength, elastic modulus, etc.) of the carbon fiber.

[0075] 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 following 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.

[0076] 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. [Example]

[0077] 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.

[0078] <Treatment agent application rate> The application rate 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 application rate was calculated by the following method. The carbon fiber precursor after the treatment agent was 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 the silicon content was determined by colorimetric quantification of silicomolybdenum blue (wavelength 815 mμ). The silicon content determined here and the silicon content in the treatment agent previously determined by the same method were used to calculate the application rate (wt%) of the carbon fiber precursor treatment agent.

[0079] <Acid value> The acid value of the ester compound (A) was measured in accordance with the neutralization titration method specified in JIS K0070, and the average value of five measurements was used.

[0080] <Iodine value> The iodine value of the ester compound (A) was measured in accordance with JIS K0070, and the average value of five measurements was used.

[0081] <Hydroxyl value> The hydroxyl value of the ester compound (A) was measured in accordance with the neutralization titration method specified in JIS K0070, and the average value of five measurements was used.

[0082] <Bundling of carbon fiber precursor> The degree of bundling of the carbon fiber precursor was observed at the time of winding and unwinding in the spinning process of the carbon fiber precursor, and at the inlet and outlet of the flame-resistant furnace in the flame-resistant process, and was visually evaluated overall according to the following evaluation criteria, with ◎ and ○ being considered as passing. ◎: The fiber bundle is of uniform thickness, and no loosening of the individual fibers is observed, showing excellent bundling properties. ◯: The fiber bundle is of uniform thickness, and there is almost no loosening of the single fibers, showing excellent bundling properties. △: The fiber bundle is of uniform thickness, but the individual fibers are loose and the bundling ability is somewhat poor. ×: Many single fibers are loosened, some single fibers are broken, and the bundling ability is poor.

[0083] <Abrasion resistance> Using a TM-type frictional embracing force tester TM-200 (manufactured by Daiei Scientific Instruments Co., Ltd.), a carbon fiber precursor strand (24K) was rubbed 1,000 times (reciprocating 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 fuzzing of the carbon fiber precursor strand was visually evaluated according to the following criteria, with ⊚ and ◯ representing pass. Samples that had poor processability and could not yield carbon fiber precursor strands suitable for evaluation were marked with "-" in the table. ⊚: No fluffing was observed, just like before rubbing, and the abrasion resistance was very good. ◯: Only a few fluffs are observed, and the abrasion resistance is excellent. △: There is a little bit of fluffing and the abrasion resistance is a little poor. ×: Much fuzzing, significant single yarn breakage, and poor abrasion resistance.

[0084] <Spinning operation> After applying the treatment agent to 50 kg of carbon fiber precursor, the degree of contamination of the drying roller was evaluated according to the following evaluation criteria, with ⊚ and ◯ being considered acceptable. ⊚: There is no roller contamination due to gum-up, and the spinning operability is very excellent. ◯: Roller contamination due to gum-up is minimal, and spinning operability is excellent. △: Roller contamination due to gum-up occurs, and spinning operability is slightly poor. ×: Significant roller contamination due to gum-up, single yarns being taken out during spinning, and curling up, resulting in poor spinning operability.

[0085] <Carbon fiber strength> The carbon fiber strength (GPa) was determined by the epoxy resin impregnated strand method specified in JIS-R-7608, and the average value of 10 measurements was used as the carbon fiber strength (GPa). Samples that had poor processability and could not produce carbon fiber strands suitable for evaluation were marked with "-" in the table.

[0086] <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. The amount of the treatment agent remaining on the aluminum sheet when the fluctuation range of the volatile content over 150 seconds reached 0.15% was taken as the non-volatile content of the treatment agent.

[0087] <Viscosity> The non-volatile content of the treatment agent obtained by the above method was used as the measurement sample, and the viscosity was measured using a rheometer (HAAKE MARS 40, manufactured by ThermoFisher Scientific) under the following conditions: measurement mode: rotation mode, parallel plate jig (φ25 mm), plate distance: 0.500 mm, sample temperature: 25°C, rotation speed: 100 rpm. Samples with a viscosity exceeding 10,000 mPa·s are marked in the table as "10,000↑."

[0088] [Production of ester compound (A-6)] 13.5 parts of trimethylolpropane, 84.3 parts of linoleic acid, and 1.0 part of paratoluenesulfonic acid as a reaction catalyst were mixed. Under a nitrogen stream, the temperature was raised to 210°C and the reaction was carried out for 1 hour. The temperature was then raised to 250°C and the reaction was carried out for 8 hours. The reaction catalyst and unreacted fatty acid were removed from the ester after the reaction, and an ester compound (A-6) with an iodine value of 165, an acid value of 0.7 mg KOH / g, a hydroxyl value of 6.0 mg KOH / g, and a molecular weight of 921 was obtained.

[0089] Example 1 A treatment agent for carbon fiber precursors with a nonvolatile content of 20% by weight was prepared by mixing and emulsifying ester compound A-1, surfactants B-1 and B-3, and water so as to obtain the nonvolatile content composition of the treatment agent shown in Table 1. The weight percentages of ester compound A-1, surfactant B-1, and surfactant B-3 in the nonvolatile content of the treatment agent were 70% by weight, 25% by weight, and 5% by weight, respectively. Next, the prepared treatment agent was further diluted with water to obtain a diluted solution with a nonvolatile content of 3.0% by weight. 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.

[0090] [Examples 2 to 37, Comparative Examples 3 to 9] A treating agent for carbon fiber precursors, a carbon fiber precursor, and carbon fibers were prepared and evaluated in the same manner as in Example 1, except that the treating agent was prepared so that the non-volatile composition of the treating agent was as shown in Tables 1 to 4. The results of evaluation of each property value are shown in Tables 1 to 4.

[0091] [Comparative Examples 1, 2, 10, and 11] The treatment agents of Comparative Examples 1, 2, 10, and 11 could not be emulsified into an aqueous system, so a treatment liquid was prepared by mixing them to obtain the composition shown in Table 4. The prepared treatment liquid was applied to a carbon fiber precursor by straight oil supply so that the application rate of the non-volatile content of the treatment agent was 1.0 wt %. Otherwise, in the same manner as in Example 1, a treatment agent for carbon fiber precursors, a carbon fiber precursor, and carbon fibers were prepared and evaluated. The results of evaluation of each property value are shown in Table 4.

[0092] The details of the nonvolatile compositions in Tables 1 to 3 are as follows. <Ester compound (A)> (A-1) Sorbitan trioleate (iodine value: 78.6, hydroxyl value: 60.3 mg KOH / g, molecular weight: 957) (A-2) Decaglycerin decaoleate (iodine value: 79.1, hydroxyl value: 30.3 mg KOH / g, molecular weight: 3403) (A-3) Pentaglycerin trioleate (iodine value: 65.3, hydroxyl value: 207.3 mg KOH / g, molecular weight: 1182) (A-4): Ester compound of 1 mole of trimethylolpropane with 1 mole of oleic acid and 2 moles of lauric acid (ratio of unsaturated fatty acids in the fatty acids constituting the ester compound: 41.3% by weight, iodine value: 33.3, hydroxyl value: 3.7 mg KOH / g, molecular weight: 763) (A-5) POE(6) sorbitan monooleate (iodine value: 38.6, hydroxyl value: 240 mg KOH / g, molecular weight: 675) (A-6) Ester compound of 1 mole of trimethylolpropane and 3 moles of linoleic acid (iodine value: 165, hydroxyl value: 6.0 mg KOH / g, molecular weight: 921) (A-7) Ester compound of 1 mole of pentaerythritol with 1 mole of linoleic acid, 1 mole of stearic acid, and 2 moles of myristic acid (ratio of unsaturated fatty acids in the fatty acids constituting the ester compound: 27.4% by weight, iodine value: 46.8, hydroxyl value: 5.2 mg KOH / g, molecular weight: 1086) Incidentally, POE(6) indicates that 6 moles of polyoxyethylene have been added, and different values ​​in parentheses indicate different numbers of moles of polyoxyethylene added.

[0093] <Surfactant (B)> (B-1) POE(20) hydrogenated castor oil ether (B-2) POE(9) C12-14 secondary alkyl ether (B-3) POE(5) cetyl ether (B-4) Ester compound of 1 mole of polyethylene glycol (molecular weight 600) and 2 moles of oleic acid (B-5) An ether-type nonionic surfactant in which 12 moles of polyoxyethylene and 15 moles of polyoxypropylene are randomly added to 1 mole of stearyl alcohol (B-6) Potassium oleate (B-7) Sorbitan monolaurate (B-8) Decaglycerin deca stearate (B-9) Polyoxyethylene 10 mole adduct of bisphenol A

[0094] <Silicone Compound (C)> (C-1) Amino-modified silicone (25°C kinematic viscosity: 1,300 mm 2 / s, amino equivalent: 2,000 g / mol, modified type: diamine) (C-2) Amino-modified silicone (25°C kinematic viscosity: 4,500mm 2 / s, amino equivalent: 1,000 g / mol, modified type: diamine) (C-3) Amino-modified silicone (25°C kinematic viscosity: 120mm 2 / s, amino equivalent: 5,000 g / mol, modified type: monoamine)

[0095] <Other ingredients (D)> (D-1) Oleyl oleate (D-2) Coconut oil (ratio of unsaturated fatty acids to fatty acids constituting ester compounds: 7.8% by weight) (D-3) Soybean oil (ratio of unsaturated fatty acids to the fatty acids constituting the ester compound: 83.7% by weight) (D-4) Linseed oil (ratio of unsaturated fatty acids to the fatty acids constituting the ester compound: 90.6% by weight)

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] As can be seen from Tables 1 to 4, the treating agents for carbon fiber precursors of Examples 1 to 37 are treating agents for carbon fiber precursors containing an ester compound (A) and a surfactant (B), where the ester compound (A) is a compound having an ester structure of an alcohol (X) having 5 to 40 carbon atoms and 3 or more hydroxyl groups and a fatty acid (Y) including an unsaturated fatty acid, and therefore can impart excellent sizing ability to the carbon fiber precursor in the flame-stabilizing step. On the other hand, the treating agents for carbon fiber precursors of Comparative Examples 1 to 11 are not treating agents for carbon fiber precursors according to the present invention, and therefore could not impart excellent sizing ability to the carbon fiber precursor in the flame-stabilizing step.

Claims

1. A treatment agent for carbon fiber precursors, comprising an ester compound (A) and a surfactant (B), the ester compound (A) is a compound having an esterified structure of an alcohol (X) having 5 to 40 carbon atoms and 3 or more hydroxyl groups and a fatty acid (Y) including an unsaturated fatty acid.

2. 2. The treatment agent for carbon fiber precursors according to claim 1, wherein the ester compound (A) comprises a compound having an esterified structure of an alcohol (X) having 6 to 40 carbon atoms and 3 or more hydroxyl groups and the fatty acid (Y).

3. 2. The treatment agent for carbon fiber precursors according to claim 1, wherein the ester compound (A) comprises a compound having an esterified structure of an alcohol (X) having 5 to 40 carbon atoms and 4 or more hydroxyl groups and the fatty acid (Y).

4. The treatment agent for carbon fiber precursors according to claim 1 , wherein the ester compound (A) includes an ester compound having a hydroxyl group.

5. 2. The treatment agent for carbon fiber precursors according to claim 1, wherein the ester compound (A) is a compound having an esterified structure of the alcohol (X) and the fatty acid (Y), in which a ratio of unsaturated fatty acids in the fatty acid (Y) is 15% by weight to 100% by weight.

6. The treatment agent for carbon fiber precursors according to claim 1 , wherein the ester compound (A) includes an ester compound having two or more ester bonds in the molecule.

7. The treatment agent for carbon fiber precursors according to claim 1 , wherein the ester compound (A) comprises an ester compound having a molecular weight of 650 or more.

8. 2. The treatment agent for carbon fiber precursors according to claim 1, wherein a proportion of the ester compound (A) in the non-volatile components of the treatment agent for carbon fiber precursors is 10 to 95% by weight, and a proportion of the surfactant (B) in the non-volatile components of the treatment agent for carbon fiber precursors is 5 to 90% by weight.

9. 2. The treatment agent for carbon fiber precursors according to claim 1, wherein a weight ratio (A / B) of the ester compound (A) to the surfactant (B) is 0.1 to 20.

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

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

Images