Treatment agent for carbon fiber precursor and use thereof

Abstract

The purpose of the present invention is to provide: a treatment agent for a carbon fiber precursor, the treatment agent being configured such that when used to produce a carbon fiber precursor and carbon fibers, even after long-term post-preparation storage, successfully reduces fluff and yarn breakage; and methods for producing a carbon fiber precursor using the treatment agent, and carbon fibers using the treatment agent.　The treatment agent for a carbon fiber precursor according to the present invention contains a silicone (A) and a (poly)oxyalkylene derivative (B), and satisfies conditions 1 and 2. Condition 1: Absorbance (X1) at 600 nm when made into an aqueous dispersion having a non-volatile content concentration of 1 wt% is 0.07-1.0. Condition 2: Absorbance (X2) at 900 nm when made into an aqueous dispersion having a non-volatile content concentration of 5 wt% is 0.05-0.8.

Description

Treatment agent for carbon fiber precursor and its use

[0001] The present invention relates to a treatment agent for carbon fiber precursors and uses thereof. More specifically, the present invention relates to a treatment agent used in producing carbon fiber precursors, a carbon fiber precursor (hereinafter sometimes referred to as a precursor) using the treatment agent, and a method for producing carbon fibers 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 involves first producing a carbon fiber precursor (the carbon fiber precursor production process is sometimes referred to as the "spinning process"). This carbon fiber precursor is converted into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C (this process is sometimes referred to as the "flame-resistant treatment process" below), followed by carbonization in an inert atmosphere at 300 to 2000°C (this process is sometimes referred to as the "carbonization treatment process" below). (The flame-resistant treatment process and carbonization treatment process are collectively referred to as the "sintering process" below.) During this firing process, fusion between single fibers occurs, which can easily cause problems such as fluffing and thread breakage, hindering productivity improvement.

[0003] In order to prevent the fusing of single fibers together during the firing process, a silicone-based treatment agent is applied to the carbon fiber precursor during production, and many techniques have been proposed for applying the treatment agent in the form of an aqueous emulsion in order to apply the treatment agent uniformly (see Patent Documents 1 and 2).

[0004] Japanese Patent Publication No. 2012-46855 Japanese Patent Publication No. 2016-17231

[0005] However, with such a silicone-based treatment agent, even if there is no problem with the carbon fiber precursor and carbon fiber produced using the treatment agent immediately after preparation, there are cases in which fuzz and thread breakage occur in the carbon fiber precursor and carbon fiber produced using the treatment agent stored for a long period after preparation, resulting in a deterioration in productivity. Therefore, an object of the present invention is to provide a treatment agent for carbon fiber precursors that can reduce fuzz and thread breakage when producing carbon fiber precursors and carbon fibers, even when a treatment agent stored for a long period after preparation is used, a carbon fiber precursor using the treatment agent, and a method for producing carbon fibers using the treatment agent.

[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 that contains a silicone (A) and a (poly)oxyalkylene derivative (B) and satisfies specific conditions 1 and 2 can reduce fuzz and yarn breakage when producing carbon fiber precursors and carbon fibers, even when the treatment agent has been stored for a long period of time after its preparation.

[0007] 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 silicone (A) and a (poly)oxyalkylene derivative (B), and satisfying the following conditions 1 and 2. Condition 1: When the agent is dispersed in water with a nonvolatile content of 1% by weight, the absorbance (X1) at 600 nm is 0.07 to 1.0. Condition 2: When the agent is dispersed in water with a nonvolatile content of 5% by weight, the absorbance (X2) at 900 nm is 0.05 to 0.8. <2> The nonvolatile content of the treating agent is １ The treating agent for carbon fiber precursors according to <1>, wherein in a spectrum measured by H-NMR, the ratio (Y2 / Y1) of the area of ​​a peak (Y2) in the range of -0.3 to 0.3 ppm to the area (Y1) of a peak in the range of 0.4 to 0.7 ppm is 100 to 1200. <3> The treating agent for carbon fiber precursors according to <1>, １The treatment agent for carbon fiber precursors according to <1> or <2>, wherein the ratio (Z2 / Z1) of the area of ​​a peak (Z2) within a range of -0.3 to 0.3 ppm to the area of ​​a peak (Z1) within a range of 3.5 to 4.0 ppm in a spectrum measured by H-NMR is 5 to 13. <4> The treatment agent for carbon fiber precursors according to any one of <1> to <3>, wherein the treatment agent has a surface tension of 20 to 35 mN / m when dispersed in water to a non-volatile content concentration of 1% by weight. <5> The treatment agent for carbon fiber precursors according to any one of <1> to <4>, wherein the silicone (A) accounts for 50% by weight to 95% by weight, and the derivative (B) accounts for 5% by weight to 25% by weight of the non-volatile content of the treatment agent. <6> The treatment agent for carbon fiber precursors according to any one of <1> to <5>, further containing a Brønsted acid compound (C). <7> The treating agent for carbon fiber precursors according to any one of <1> to <6>, wherein the derivative (B) comprises a compound having a structure in which an alkylene oxide having 2 to 4 carbon atoms is added to at least one selected from alcohols having 6 to 20 carbon atoms and having 1 to 3 hydroxy groups and phenols having 6 to 20 carbon atoms and having 1 to 3 hydroxy groups. <8> A carbon fiber precursor obtained by adhering the treating agent for carbon fiber precursors according to any one of <1> to <7> to a raw material carbon fiber precursor for the carbon fiber precursor. <9> A method for producing carbon fibers, comprising: a flame-resistant treatment step of converting the carbon fiber precursor according to <8> into a flame-resistant fiber; and a carbonization treatment step of further carbonizing the flame-resistant fiber.

[0008] The treating agent for carbon fiber precursors of the present invention can reduce fuzz and thread breakage when producing carbon fiber precursors and carbon fibers, even when a treating agent that has been stored for a long period after preparation is used. According to a carbon fiber precursor using the treating agent for carbon fiber precursors of the present invention and a method for producing carbon fibers using the treating agent, fuzz and thread breakage of carbon fibers can be reduced, even when a treating agent for carbon fiber precursors that has been stored for a long period after preparation is used.

[0009] The components of the treating agent for carbon fiber precursors of the present invention (hereinafter sometimes simply referred to as the treating agent) are described below. [Silicone (A)] The treating agent of the present invention contains silicone (A). There are no particular limitations on the silicone (A), as long as its main chain is an inorganic siloxane bond (—Si—O—Si—) and it has organic groups in its side chains. However, it is preferable for the silicone (A) to contain a modified silicone having a modifying group, in order to achieve the effects of the present invention, to easily satisfy conditions 1 and 2, and to easily satisfy the (Y2 / Y1) ratio of 100 to 1200. Examples of modified silicones include amino-modified silicones, polyether-modified silicones, and aminopolyether-modified silicones. It is preferable for the silicone (A) to contain at least one selected from amino-modified silicones and aminopolyether-modified silicones, and more preferably contains amino-modified silicones, in order to achieve the effects of the present invention, to easily satisfy conditions 1 and 2, and to easily satisfy the (Y2 / Y1) ratio of 100 to 1200. One or more types of silicones can be used.

[0010] The kinematic viscosity of the silicone (A) at 25°C is 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, the viewpoints of easily satisfying conditions 1 and 2, the viewpoints of easily satisfying (Y2 / Y1) of 100 to 1,200, and the viewpoints of easily satisfying (Z2 / Z1) of 5 to 13. ２ The upper limit of the kinematic viscosity is more preferably 15,000 mm ２ / s, more preferably 10,000 mm ２ / s, particularly preferably 8000 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.

[0011] The amino group (including an organic group having an amino group) that is the modifying group of the amino-modified silicone 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-resistant 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, and a polyamine type, and both may coexist in one molecule. However, from the viewpoints of uniformly applying the treatment agent to the inside of the fiber bundle in the flame-resistant treatment step and forming a film with the treatment agent to protect the fibers, easily satisfying conditions 1 and 2, and easily satisfying (Y2 / Y1) of 100 to 1200, the monoamine type or diamine type is preferred, and the diamine type is more preferred. The polyether group (including an organic group having a polyoxyalkylene group) that is the modifying group of the polyether-modified silicone may be bonded to a side chain of the silicone main chain, to an end, or to both. However, from the viewpoint of fiber protection in the flame-proofing treatment step, and because it is more likely to satisfy conditions 1 and 2 and (Y2 / Y1) of 100 to 1200, it is preferably bonded to a side chain (having a polyether group in the side chain). Furthermore, in order to form a film with the treatment agent and protect the fiber, it is preferable that the polyether group contains at least one group selected from a polyoxyethylene group, a polyoxypropylene group, and a polyoxyethylene polyoxypropylene group. 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).

[0012] The amino equivalent of the amino-modified silicone is preferably 300 to 10,000 g / mol from the viewpoints of preventing adhesion and fusion between fibers, easily satisfying Conditions 1 and 2, and easily satisfying the (Y2 / Y1) ratio of 100 to 1,200. 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 into per mol of amino groups or ammonium groups. Therefore, the smaller the amino equivalent value, the higher the proportion of amino groups or ammonium groups in the molecule.

[0013] The amino-modified silicone may be a combination of multiple amino-modified silicones with different amino equivalents or kinematic viscosities (25°C). When two or more types of amino-modified silicones are used, the amino equivalent refers to the amino equivalent of the entire amino-modified silicone (mixture), and the kinematic viscosity at 25°C refers to the kinematic viscosity of the entire amino-modified silicone (mixture).

[0014] The amino-modified silicone may, for example, be a compound represented by the following general formula (1):

[0015] (In formula (1), R １ represents an alkyl group or an aryl group having 1 to 20 carbon atoms. ２ is a group represented by the following general formula (2): ３ is R １ , R ２ Or -OR ９ (R ９ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. p is 5≦p≦10000, and q is 0≦q≦1000. However, when q=0, R ３At least one of the repeating units p and q is a group represented by the following general formula (2). The order of the repeating units bounded by p and q is not limited, and the bonding pattern may be alternating, block, or random.

[0016] In formula (1), R １ represents an alkyl group or an aryl group having 1 to 20 carbon atoms. １ is preferably an alkyl group or an aryl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and even more preferably a methyl group. １ may be the same or different. ２ is a group represented by the following general formula (2): ３ is R １ , R ２ Or -OR ９ and preferably R １ In addition, the plurality of R in formula (1) ９ may be the same or different. ９ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and more preferably a hydrogen atom or a methyl group. p is a number from 5 to 10,000, preferably 30 to 5,000, and more preferably 50 to 2,000. q is a number from 0 to 1,000, preferably 1 to 500, and more preferably 2 to 100.

[0017]

[0018] In formula (2), R ４ and R ６ are each independently an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 1 to 3 carbon atoms. ５ , R ７ and R ８ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group, preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and more preferably a hydrogen atom. r is a number from 0 to 6, preferably 0 to 3, and more preferably 0 to 1.

[0019] [(Poly)oxyalkylene Derivative (B)] The treatment agent of the present invention contains a (poly)oxyalkylene derivative (B) (hereinafter, sometimes referred to as derivative (B)). There are no particular limitations on the derivative (B) as long as it is a compound having a (poly)oxyalkylene group. Examples of derivative (B) include polyoxyalkylene linear alkyl ethers, polyoxyalkylene branched alkyl ethers, polyoxyalkylene secondary alkyl ethers, polyoxyethylene alkenyl ethers, alkylene oxide adducts of alkynediols, polyoxyalkylene alkylphenyl ethers, alkylene oxide adducts of bisphenols, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan esters, polyoxyalkylene castor oil ethers, polyoxyalkylene hydrogenated castor oil ethers, polyoxyethylene polyoxypropylene polymers, and polyoxyalkylene alkylamino ethers. Among these, from the viewpoint of achieving the effects of the present application, easily satisfying Conditions 1 and 2, and easily satisfying the ratio (Z2 / Z1) of 5 to 13, it is preferable to include at least one selected from polyoxyalkylene linear alkyl ethers, polyoxyalkylene branched alkyl ethers, polyoxyalkylene secondary alkyl ethers, alkylene oxide adducts of alkynediols, polyoxyalkylene alkylphenyl ethers, alkylene oxide adducts of bisphenols, and polyoxyethylene polycyclic phenyl ethers, and it is more preferable to include a compound having a structure in which an alkylene oxide having 2 to 4 carbon atoms is added to at least one selected from alcohols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups and phenols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups.

[0020] Examples of the alcohols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups and the phenols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups include linear alcohols such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, and octadecyl alcohol; branched alcohols such as 2-ethylhexyl alcohol, isodecyl alcohol, isotridecyl alcohol, and isooctadecyl alcohol; secondary alcohols such as secondary dodecyl alcohol, secondary tridecyl alcohol, and secondary tetradecyl alcohol; alkenyl alcohols such as octadecenyl alcohol; alkynediols such as alkynediols having 12 to 18 carbon atoms; alkylphenols such as nonylphenol; bisphenols such as bisphenol A and bisphenol F; polycyclic phenols such as styrenated phenol, distyrenated phenol, and tristyrenated phenol; sorbitan esters such as sorbitan fatty acid esters; and polyoxyalkylenes such as polyethylene glycol and polypropylene glycol. In terms of achieving the effects of the present invention, the alcohols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups and the phenols having 6 to 20 carbon atoms and 1 to 3 hydroxy groups preferably include at least one selected from hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, 2-ethylhexyl alcohol, isodecyl alcohol, isotridecyl alcohol, isooctadecyl alcohol, secondary dodecyl alcohol, secondary tridecyl alcohol, secondary tetradecyl alcohol, nonylphenol, bisphenol A, bisphenol F, styrenated phenol, distyrenated phenol, and tristyrenated phenol. Examples of alkylene oxides having 2 to 4 carbon atoms include ethylene oxide, propylene oxide, and butylene oxide.The alkylene oxide is preferably at least one selected from ethylene oxide and propylene oxide, in that it exhibits the effects of the present invention, is likely to satisfy conditions 1 and 2, and is likely to satisfy the ratio (Z2 / Z1) of 5 to 13. The derivative (B) may contain one or more types, and it is more preferable to contain two or more types in that it has excellent emulsifiability.

[0021] The number of moles of alkylene oxide added in the polyoxyalkylene chain of the (poly)oxyalkylene derivative (B) is preferably 1 to 25 moles, from the viewpoints of achieving the effects of the present invention, easily satisfying conditions 1 and 2, and easily satisfying the (Z2 / Z1) ratio of 5 to 13. The upper limit of the number of moles added is more preferably 20 moles, even more preferably 18 moles, and particularly preferably 15 moles. On the other hand, the lower limit of the number of moles added is more preferably 2 moles, even more preferably 3 moles. Also, for example, 2 to 18 moles is more preferable, and 3 to 15 moles is even more preferable.

[0022] [Bronsted Acid Compound (C)] The treating agent of the present invention preferably contains a Bronsted acid compound (C) because it is more likely to satisfy conditions 1 and 2. The Bronsted acid compound (C) 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Aliphatic polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tetradecanedicarboxylic acid, pentadecanedioic acid, and derivatives thereof.

[0027] The aromatic monocarboxylic acids include benzoic acid, cinnamic acid, naphthoic acid, toluic acid, and derivatives thereof.

[0028] Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and derivatives thereof.

[0029] 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.

[0030] Inorganic acids are acids containing non-metallic atoms, such as sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.

[0031] 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.

[0032] 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.

[0033] Examples of the organic sulfate compound include alkyl sulfate, polyoxyalkylene alkyl sulfate, alkylphenyl sulfate, and polyoxyalkylene alkylphenyl sulfate.

[0034] Examples of the organic phosphonic acid compound include alkyl phosphonic acid, aromatic phosphonic acid, and polyoxyalkylene alkyl ether phosphonic acid.

[0035] The pKa of the Bronsted acid compound (C) is preferably 0 to 7, more preferably 1 to 6.5, and even more preferably 2 to 6, from the viewpoints of corrosion and safety of equipment and of suppressing crosslinking over time due to the amino group of the amino-modified silicone.

[0036] The Brønsted acid compound (C) preferably contains at least one selected from an organic carboxylic acid compound, an inorganic acid, and an organic phosphate compound, more preferably contains at least one selected from lactic acid, an alkyl ether carboxylic acid, an organic phosphate compound, phosphoric acid, and acetic acid, and even more preferably contains at least one selected from an alkyl ether carboxylic acid, an organic phosphate compound, acetic acid, and phosphoric acid, in that it is likely to satisfy conditions 1 and 2. One or more Brønsted acid compounds (C) may be used.

[0037] [Treatment agent for carbon fiber precursors] The treatment agent for carbon fiber precursors of the present invention contains the above-mentioned silicone (A) and (poly)oxyalkylene derivative (B), and satisfies the following conditions 1 and 2. Condition 1: When made into an aqueous dispersion with a nonvolatile content of 1 wt%, the absorbance (X1) at 600 nm is 0.07 to 1.0. Condition 2: When made into an aqueous dispersion with a nonvolatile content of 5 wt%, the absorbance (X2) at 900 nm is 0.05 to 0.8. 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.

[0038] The reason why the treating agent for carbon fiber precursors of the present invention contains silicone (A) and a derivative (B) and satisfies conditions 1 and 2 above and, therefore, can reduce fuzz and thread breakage when producing carbon fiber precursors and carbon fibers even when using a treating agent that has been stored for a long period after preparation, is not particularly limited, but is thought to be that the ability to maintain an aqueous dispersion state that shows absorbance within a specific range at each of two levels of non-volatile content, 1% by weight and 5% by weight, allows stable adsorption to the fiber surface to be maintained even against local changes in the concentration of the treating agent that occur when components in the treating agent are adsorbed to the carbon fiber precursor in the oiling bath, and the treating agent can be uniformly adsorbed even to the surface of single fibers inside the fiber bundle, making it less likely that changes will occur in the degree of adsorption of the treating agent components to the carbon fiber precursor even with a treating agent that has been stored for a long period of time.

[0039] The absorbance (X1) described in the condition 1 and the absorbance (X2) described in the condition 2 were measured by an ultraviolet-visible-near-infrared spectrophotometer after diluting the carbon fiber precursor treatment agent with water as necessary so that the non-volatile content concentration of the treatment agent becomes an aqueous dispersion of 1 wt % or 5 wt %, and were measured by the method described in the examples.

[0040] The absorbance (X1) described in the condition 1 is 0.07 to 1.0. If the absorbance (X1) is less than 0.07, the treatment agent penetrates into the interior of the single fiber, resulting in increased fuzz and thread breakage. If the absorbance (X1) is more than 1.0, the adsorption of the treatment agent to the carbon fiber precursor after long-term storage deteriorates, resulting in increased fuzz and thread breakage. The lower limit of the absorbance (X1) is preferably 0.08, more preferably 0.1, and even more preferably 0.2. On the other hand, the upper limit of the absorbance (X1) is preferably 0.9, more preferably 0.8, and even more preferably 0.7. Furthermore, for example, the absorbance is preferably 0.08 to 0.9, more preferably 0.1 to 0.7, and even more preferably 0.2 to 0.7.

[0041] The absorbance (X2) described in the condition 2 is 0.05 to 0.8. If the absorbance (X2) is less than 0.05, the treatment agent penetrates into the interior of the single fiber, resulting in increased fuzz and thread breakage. If the absorbance (X2) is more than 0.8, the adsorption of the treatment agent to the carbon fiber precursor after long-term storage deteriorates, resulting in increased fuzz and thread breakage. The lower limit of the absorbance (X2) is preferably 0.06, more preferably 0.08, and even more preferably 0.2. On the other hand, the upper limit of the absorbance (X2) is preferably 0.7, more preferably 0.6, and even more preferably 0.55. Furthermore, for example, 0.06 to 0.7 is more preferable, 0.08 to 0.6 is even more preferable, and 0.2 to 0.55 is particularly preferable.

[0042] The non-volatile content of the treatment agent of the present invention １ In a spectrum measured by H-NMR, the ratio (Y2 / Y1) of the area of ​​the peak (Y2) in the range of -0.3 to 0.3 ppm to the area of ​​the peak (Y1) in the range of 0.4 to 0.7 ppm indicates the proportion of modifying groups in the silicone. A ratio of 100 to 1200 is considered to indicate excellent thermal stability of the silicone, making it less likely to generate tar during the flame-proofing process and preventing damage to the fibers due to contact between the tar and the fibers. The upper limit of the peak area ratio (Y2 / Y1) is more preferably 1100, even more preferably 1000, and particularly preferably 900. Meanwhile, the lower limit of the peak area ratio (Y2 / Y1) is more preferably 200, even more preferably 300, and particularly preferably 400. For example, a ratio of 200 to 1100 is more preferable, 300 to 1000 is more preferable, and 400 to 900 is particularly preferable.

[0043] The non-volatile content of the treatment agent of the present invention １In a spectrum measured by H-NMR, the ratio (Z2 / Z1) of the area of ​​the peak (Z2) in the range of -0.3 to 0.3 ppm to the area of ​​the peak (Z1) in the range of 3.5 to 4.0 ppm indicates the ratio of the silicone main chain to the (poly)oxyalkylene group of the (poly)oxyalkylene derivative, and a ratio of 5 to 13 is preferred from the perspective of emulsification, as it is believed to contain an appropriate amount of (poly)oxyalkylene group for emulsifying the silicone. The upper limit of this peak area ratio (Z2 / Z1) is more preferably 12, even more preferably 11, and particularly preferably 10. Meanwhile, the lower limit of this peak area ratio (Z2 / Z1) is more preferably 5.5, even more preferably 6.0, and particularly preferably 6.5. For example, a ratio of 5.5 to 12 is more preferred, 6.0 to 11 is more preferred, and 6.5 to 10 is particularly preferred.

[0044] When the treatment agent of the present invention is dispersed in water with a nonvolatile content of 1% by weight, the surface tension is preferably 20 to 35 mN / m in terms of uniform adhesion of the treatment agent. The upper limit of the surface tension is more preferably 34 mN / m, even more preferably 33 mN / m, and particularly preferably 32 mN / m. Meanwhile, the lower limit of the surface tension is more preferably 22 mN / m, even more preferably 23 mN / m, and particularly preferably 24 mN / m. Furthermore, for example, 22 to 34 mN / m is more preferable, 23 to 33 mN / m is more preferable, and 24 to 32 mN / m is particularly preferable.

[0045] The proportion of silicone (A) in the non-volatile content of the treating agent of the present invention is preferably 50 to 95% by weight, in that it is easy to satisfy conditions 1 and 2 and easy to satisfy the (Z2 / Z1) ratio of 5 to 13. The upper limit of this proportion is more preferably 90% by weight, even more preferably 87% by weight, and particularly preferably 85% by weight. On the other hand, the lower limit of this proportion is more preferably 55% by weight, even more preferably 65% ​​by weight, and particularly preferably 75% by weight. Furthermore, for example, 55 to 90% by weight is more preferable, 65 to 87% by weight is even more preferable, and 75 to 85% by weight is particularly preferable.

[0046] The proportion of derivative (B) in the non-volatile content of the treatment agent of the present invention is preferably 5 to 25% by weight, since this makes it easier to satisfy conditions 1 and 2 and to satisfy the (Z2 / Z1) ratio of 5 to 13. The upper limit of this proportion is more preferably 23% by weight, even more preferably 20% by weight, and particularly preferably 18% by weight. Meanwhile, the lower limit of this proportion is more preferably 6% by weight, even more preferably 7% by weight, and particularly preferably 8% by weight. Furthermore, for example, 6 to 23% by weight is more preferable, 7 to 20% by weight is even more preferable, and 8 to 18% by weight is particularly preferable.

[0047] The ratio of derivative (B) to 100 parts by weight of silicone (A) is preferably 5 to 35 parts by weight, since this makes it easier to satisfy conditions 1 and 2 and to have (Z2 / Z1) of 5 to 13. The upper limit of this ratio is more preferably 30 parts by weight, even more preferably 25 parts by weight, and particularly preferably 23 parts by weight. Meanwhile, the lower limit of this weight ratio is more preferably 6 parts by weight, even more preferably 8 parts by weight, and particularly preferably 1 part by weight. Furthermore, for example, 6 to 30 parts by weight is more preferable, 8 to 25 parts by weight is even more preferable, and 1 to 23 parts by weight is particularly preferable.

[0048] When the treatment agent of the present invention further contains a Brønsted acid compound (C), the proportion of the Brønsted acid compound (C) in the non-volatile content of the treatment agent of the present invention is preferably 0.05 to 10 wt %, in order to more easily satisfy conditions 1 and 2. The upper limit of this weight proportion is more preferably 8.5 wt %, even more preferably 7 wt %, and particularly preferably 5 wt %. On the other hand, the lower limit of this weight proportion is more preferably 0.65 wt %, even more preferably 0.80 wt %, and particularly preferably 1 wt %. Furthermore, for example, 0.80 to 7 wt % is more preferable, and 1 to 5 wt % is even more preferable.

[0049] When the treatment agent of the present invention further contains a Brønsted acid compound (C), the weight ratio of the Brønsted acid compound (C) to the silicone (A) ((C) / (A)) is preferably 0.005 to 0.075, in order to more easily satisfy conditions 1 and 2. The upper limit of this ratio is more preferably 0.070, even more preferably 0.065, particularly preferably 0.060, and most preferably 0.055. On the other hand, the lower limit of this ratio is more preferably 0.0065, even more preferably 0.008, particularly preferably 0.01, and most preferably 0.012. Furthermore, for example, the ratio is more preferably 0.010 to 0.060, and even more preferably 0.012 to 0.055.

[0050] [Other Component (D)] The treatment agent of the present invention preferably further contains another nonionic surfactant as the other component (D) in order to enhance emulsifiability. The other nonionic surfactant refers to a nonionic surfactant other than the derivative (B). Examples of the other nonionic surfactant include sorbitan esters such as sorbitan monopalmitate and sorbitan monooleate; glycerin fatty acid esters such as glycerin monostearate, glycerin monolaurate, and glycerin monopalmitate; and sucrose fatty acid esters. The weight-average molecular weight of the other nonionic surfactant is preferably 2,000 or less, more preferably 200 to 1,800, more preferably 300 to 1,500, and even more preferably 500 to 1,000. One or more types of the other nonionic surfactant may be used.

[0051] When the treatment agent of the present invention contains other nonionic surfactants, the weight ratio of the other nonionic surfactants to the nonvolatile content of the treatment agent is preferably 0.1 to 10 wt % in terms of emulsion stability. The upper limit of this ratio is more preferably 8.5 wt %, even more preferably 7.0 wt %, and particularly preferably 5.0 wt %. Meanwhile, the lower limit of this ratio is more preferably 0.25 wt %, even more preferably 0.4 wt %, and particularly preferably 0.5 wt %. Furthermore, for example, 0.25 to 8.5 wt % is more preferable, 0.4 to 7.0 wt % is even more preferable, and 0.5 to 5.0 wt % is particularly preferable.

[0052] [Other Surfactants] The treatment agent of the present invention may contain surfactants other than the derivative (B), the Bronsted acid compound (C), and other nonionic surfactants, as long as the effects of the present invention are not impaired. The other surfactants are used as emulsifiers, antistatic agents, etc. The other surfactants are not particularly limited, and known surfactants can be appropriately selected and used from anionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactants may be used alone or in combination of two or more.

[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; N-(2-hydroxyethyl)-N,N-dimethyl-N- acylamidoalkyl quaternary ammonium salts such as stearoylamidopropyl ammonium nitrate, lanolin fatty acid amidopropylethyl dimethylammonium ethosulfate, and lauroylamidoethyl methyldiethylammonium methosulfate; alkylisoquinolinium salts such as laurylisoquinolinium chloride; benzalkonium salts such as lauryldimethylbenzyl ammonium chloride and stearyldimethylbenzyl 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 ethyl ester chloride; primary amine salts such as laurylamine chloride, stearylamine bromide, hardened beef tallow alkylamine chloride, and rosinamine acetate;Examples of the amine salts include secondary amine salts such as cetylmethylamine sulfate, laurylmethylamine chloride, dilaurylamine acetate, stearylethylamine bromide, laurylpropylamine acetate, dioctylamine chloride, and octadecylethylamine hydroxide; tertiary amine salts such as dilaurylmethylamine sulfate, lauryldiethylamine chloride, laurylethylmethylamine bromide, diethanolstearylamidoethylamine trihydroxyethylphosphate salt, and stearylamidoethylethanolamine urea polycondensate acetate salt; fatty acid amide guanidinium salts; and alkyltrialkyleneglycolammonium salts such as lauryltriethyleneglycolammonium 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] [Other Components] The treating agent for carbon fiber precursors of the present invention may contain other components in addition to the above-mentioned components, as long as the effects of the present invention are not impaired. Examples of other components include antioxidants such as phenols, amines, sulfurs, phosphorus, and quinones; antistatic agents such as quaternary ammonium salt-type cationic surfactants and amine salt-type cationic surfactants; smoothing agents such as alkyl esters of higher alcohols, higher alcohol ethers, and waxes; antibacterial agents; preservatives; rust inhibitors; and moisture absorbents.

[0056] 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 with a group represented by the general formula (2) above. These low molecular weight silicones may be included as a trace component of silicone (A). The content of 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 silicone (A).

[0057] The carbon fiber precursor treatment agent of the present invention is preferably in a state in which the silicone (A) and derivative (B), as well as the Brønsted acid compound (C) and other components (D), as necessary, are dissolved, solubilized, emulsified, or dispersed in water. The weight percentages of water and nonvolatile components 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 components in the entire carbon fiber precursor treatment agent is preferably 0.01 to 99.9 wt %, more preferably 0.5 to 90 wt %, and particularly preferably 1 to 50 wt %.

[0058] The carbon fiber precursor treatment agent 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 of the carbon fiber precursor treatment agent is added to warm water under stirring to emulsify and disperse the components, or a method in which each component of the carbon fiber precursor treatment agent 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 also be used. The method for producing the carbon fiber precursor treatment agent of the present invention is not particularly limited, but using a homomixer during emulsification is preferred because it is easier to satisfy Conditions 1 and 2, and emulsification is more preferably performed at a peripheral tip speed of 15 m / s or higher. On the other hand, when using a stirring impeller during emulsification, stirring is preferably performed at a blade tip speed of 2.0 m / s or higher, and more preferably at a blade tip speed of 2.5 m / s or higher, because it is easier to satisfy Conditions 1 and 2. Furthermore, the proportion of the (poly)oxyalkylene derivative (B) in the nonvolatile content during emulsification is preferably 5% by weight to 25% by weight, in order to easily satisfy conditions 1 and 2. The temperature during emulsification is preferably 70°C or higher, and more preferably 75°C or higher, in order to easily satisfy conditions 1 and 2.

[0059] The treating agent for carbon fiber precursors of the present invention can be suitably used as a treating agent for carbon fiber precursors for producing carbon fibers.

[0060] [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 treatment 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 treatment step in which the flame-resistant fiber is further carbonized. The flame-resistant treatment step is preferably a flame-resistant treatment 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 treatment 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 improves bundleability, reduces fiber bundle disorder and uneven drawing, and enables the production of high-quality carbon fiber.

[0061] 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.

[0062] The carbon fiber precursor is preferably composed of acrylic fibers, and more 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.

[0063] 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 retardant treatment process. The application method may be by using a roller or the like, or by a dipping method, a spraying method, or the like.

[0064] 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 treatment step. Note that the application rate of the treatment agent for carbon fiber precursors here is defined as the percentage of the weight of the nonvolatile content of the treatment agent for carbon fiber precursors adhered to the weight of the carbon fiber precursor.

[0065] The flame-resistant treatment step is a step of converting a carbon fiber precursor having a carbon fiber precursor treating agent attached thereto into a flame-resistant fiber in an oxidizing atmosphere at, for example, 200 to 300°C. The oxidizing atmosphere may typically be an air atmosphere. The temperature of the oxidizing atmosphere is preferably 230 to 280°C. In the flame-resistant treatment step, the 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.

[0066] 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 the same as that in 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] <Applied rate of treatment agent> 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 the silicon content was determined by colorimetric quantification (wavelength 815 nm) of silicomolybdenum blue. The applied 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.

[0071] <Number of fluffs in carbon fiber bundle> Carbon fibers were produced using a treating agent for carbon fiber precursors with a non-volatile content concentration of 30% by weight stored under the following two conditions, and the number of fluffs was measured using the following method. Storage condition 1: Stored at room temperature for 1 month. Storage condition 2: Stored at room temperature for 12 months. The carbon fiber bundle was pulled out from the bobbin without tension, and any fluff was collected until the number reached 50. The length of the carbon fiber bundle pulled out until 50 fluffs were collected was measured, and the number of fluffs per unit length (fuzz / m) was calculated from the measured length of the carbon fiber bundle as the number of fluffs present on the surface of the carbon fiber bundle, and ⊚ and ◯ were evaluated as acceptable. ⊚: The number of fluffs was less than 3 fluffs / m, and the fluff was particularly good with little fluff. ◯: The number of fluffs was 3 fluffs / m or more but less than 10 fluffs / m, and the fluff was good with little fluff. ×: The number of fluffs was 10 fluffs / m or more, and the fluff was excessive, and poor.

[0072] <Operability during firing (bundling ability)> When carbon fibers were produced using a treating agent for carbon fiber precursors with a non-volatile content of 30% by weight that had been stored under the following two conditions, the state of the flame-resistant fiber bundle immediately after passing through the flame-resistant furnace in the firing step of the carbon fiber precursor was evaluated according to the following evaluation criteria, with ⊚ and ◯ representing pass. Storage condition 1: Stored at room temperature for 1 month. Storage condition 2: Stored at room temperature for 12 months. ⊚: The fiber bundle width did not expand, there was no interference with adjacent fiber bundles, and the operability was particularly good. ◯: The fiber bundle width expanded slightly, but there was no interference with adjacent fiber bundles, and the workability was good. ×: The fiber bundle width expanded, there was interference with adjacent fiber bundles, and fluffing may occur, resulting in poor workability.

[0073] <Measurement of absorbance> Pure water was transferred to a polystyrene cell with a 12.5 mm square and a 10 mm optical path length, and the absorbance of the pure water was measured at 20 ° C. using a UV-visible near-infrared spectrophotometer (V-750 manufactured by JASCO) at a specified wavelength. A water dispersion of the carbon fiber precursor treatment agent was prepared by diluting it with water so that the non-volatile content concentration was 1 wt % or 5 wt %. The diluted solution was used as a sample, and the sample was transferred to the same polystyrene cell as the pure water. The absorbance of the sample at 20 ° C. was measured using a UV-visible near-infrared spectrophotometer (V-750 manufactured by JASCO) at a specified wavelength. The absorbance of the sample was calculated by subtracting the absorbance of pure water at the same wavelength from the absorbance. For samples with a non-volatile content concentration of 1 wt %, the absorbance (X1) at a wavelength of 600 nm was measured, and for samples with a non-volatile content concentration of 5 wt %, the absorbance (X2) at a wavelength of 900 nm was measured.

[0074] < １ H-NMR Measurement> 1 g of a treatment agent for carbon fiber precursors with a non-volatile content of 30 wt % was collected and placed in a beaker to dry off the water, after which 3 mL of chloroform-d (for NMR) was added to dissolve it uniformly, and this solution was poured into an NMR sample tube until the measurement solution reached a depth of 4 to 5 cm. １A spectrum was obtained by measuring with a H-NMR (JNM-ECZ400R manufactured by JEOL) at room temperature with 16 scans. In the obtained spectrum, the ratio (Y2 / Y1) of the area of ​​the peak (Y2) in the range of −0.3 to 0.3 ppm to the area (Y1) of the peak in the range of 0.4 to 0.7 ppm, and the ratio (Z2 / Z1) of the area of ​​the peak (Z2) in the range of −0.3 to 0.3 ppm to the area (Z1) of the peak in the range of 3.5 to 4.0 ppm were calculated.

[0075] <Measurement of surface tension> A sample was prepared by diluting the carbon fiber precursor treatment agent with water to an aqueous dispersion with a non-volatile content of 1% by weight. The surface tension of the prepared sample was measured using an automatic surface tensiometer (DY-500 manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 25°C by the Wilhelmy method using a platinum plate.

[0076] Example 1 Amino-modified silicone A1, (poly)oxyalkylene derivatives B5, B6, and B7, and antioxidants D1 and D2 were mixed to obtain the non-volatile content composition of the treatment agent shown in Table 1. The temperature of the mixture during emulsification was adjusted to 80 to 90°C (condition I), and emulsification was carried out by adding water little by little while stirring using a stirring blade at a blade tip speed of 3 m / s (condition A). Thereafter, Brønsted acid compound C6, antistatic agent D3, and acetylene-based surfactant D4 were dissolved and dispersed to prepare a treatment agent for carbon fiber precursors with a non-volatile content of 30 wt%. The weight percentage of silicone A1 in the nonvolatile content of the treatment agent was 80.8% by weight, the weight percentage of polyoxyalkylene derivative B5 was 3.7% by weight, the weight percentage of B6 was 2.5% by weight, the weight percentage of B7 was 2% by weight, the weight percentage of Brønsted acid compound C6 was 4.0% by weight, the weight percentage of antistatic agent D3 was 4% by weight, the total weight percentage of antioxidants D1 and D2 was 1% by weight, and the weight percentage of acetylene surfactant D4 was 2.0% by weight. The prepared treatment agent was then 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.

[0077] [Examples 2 to 16, 22 to 29, Comparative Examples 1 to 6] 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 nonvolatile content composition, temperature conditions during emulsification, and stirring conditions during emulsification were changed as shown in Tables 1 to 3 and 5. The results of evaluating each property value are shown in Tables 1 to 3 and 5. In addition, the addition order of the Bronsted acid compound (C) and the other component (D) other than the antioxidant was the same as in Example 1.

[0078] Examples 17, 18, and 30 to 33 Regarding the nonvolatile composition, a treating agent for carbon fiber precursors, a carbon fiber precursor, and a carbon fiber were prepared and evaluated in the same manner as in Example 1, except that B11 and B12 were not mixed during emulsification, but were mixed after emulsification, and the temperature conditions and stirring conditions during emulsification were changed as shown in Tables 2 and 3. The evaluation results for each property value are shown in Tables 2 and 3. The order of addition of the Bronsted acid compound (C) and the other component (D) other than the antioxidant was the same as in Example 1.

[0079] Example 21 With regard to the nonvolatile composition, 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 B5 was not mixed during emulsification but was mixed after emulsification, and the temperature conditions and stirring conditions during emulsification were changed as shown in Table 2. The results of evaluating each property value are shown in Table 2. The order of adding the Bronsted acid compound (C) and the other component (D) other than the antioxidant was the same as in Example 1.

[0080] Examples 34 to 36 Regarding the nonvolatile composition, 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 B14 was not mixed during emulsification but was mixed after emulsification, and the temperature conditions and stirring conditions during emulsification were changed as shown in Table 4. The results of evaluating each property value are shown in Table 4. The order of adding the Bronsted acid compound (C) and the other component (D) other than the antioxidant was the same as in Example 1.

[0081] Example 37 With regard to the nonvolatile composition, 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 B11, B12, and B14 were not mixed during emulsification, but B11, B12, and B14 were mixed after emulsification, and the temperature conditions and stirring conditions during emulsification were changed as shown in Table 4. The results of evaluating each property value are shown in Table 4. The order of adding the Bronsted acid compound (C) and other components (D) other than the antioxidant was the same as in Example 1.

[0082] Examples 38 to 44 Regarding the nonvolatile composition, 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 other components, alkyl esters (D6, D7, D8) and wax (D9), were added before emulsification, and the temperature conditions and stirring conditions during emulsification were changed as shown in Table 4. The results of evaluating each property value are shown in Table 4. The order of adding the Brønsted acid compound (C) and the other components, antistatic agent (D3) and acetylene surfactant (D4), was the same as in Example 1.

[0083] The temperature conditions and stirring conditions during emulsification shown in Tables 1 to 5 were as follows: (Temperature during emulsification) Condition I: 80-90°C Condition II: 30-40°C (Stirring conditions) Condition A: Stirring using a stirring blade at a blade tip speed of 3 m / s. Condition B: Stirring using a stirring blade at a blade tip speed of 0.5 m / s. Condition C: Stirring using a homomixer at a peripheral tip speed of 25 m / s.

[0084] The details of the nonvolatile composition in Tables 1 to 5 are as follows. Components with an asterisk next to the number in the tables indicate that they were not mixed during emulsification, but were mixed after emulsification. <Silicone (A)> Amino-modified silicone A1: kinematic viscosity at 25°C: 250 mm ２ / s, amino equivalent: 7600 g / mol, side chain diamine type amino-modified silicone A2: 25°C kinematic viscosity: 3500 mm ２ / s, amino equivalent: 2000 g / mol, side chain diamine type amino-modified silicone A3: 25°C kinematic viscosity: 1700 mm ２ / s, amino equivalent: 3800 g / mol, side chain monoamine type amino-modified silicone A4: 25°C kinematic viscosity: 1300 mm ２ / s, amino equivalent: 1700 g / mol, side chain diamine type amino-modified silicone A5: 25°C kinematic viscosity: 1500 mm ２ / s, amino equivalent: 3800 g / mol, side chain diamine type amino-modified silicone A6: 25°C kinematic viscosity: 90 mm ２ / s, amino equivalent: 3900 g / mol, diamine type amino-modified silicone A7: 25°C kinematic viscosity: 200 mm ２ / s, amino equivalent: 4000 g / mol Amino polyether modified silicone A8: 25°C kinematic viscosity: 3300 mm ２ / s, amino equivalent: 1800 g / mol, side chain amino polyether type amino-modified silicone A9: 25°C kinematic viscosity: 15000 mm ２ / s, amino equivalent: 3600 g / mol, diamine type amino-modified silicone A10: 25°C kinematic viscosity: 9000 mm ２ / s, amino equivalent: 9000 g / mol, diamine type amino-modified silicone A11: 25°C kinematic viscosity: 70 mm ２ / s, amino equivalent: 350 g / mol, diamine type polyether modified silicone A12: 25°C kinematic viscosity: 130 mm ２ / s, HLB = 4, Polyether type amino-modified silicone A13: 25 °C kinematic viscosity: 2500 mm ２ / s, amino equivalent: 3600 g / mol, side chain diamine type

[0085] <(Poly)oxyalkylene Derivatives (B)> (Poly)oxyalkylene Derivative B1: A 12-carbon alkyl ether having 3 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B2: A 12-carbon alkyl ether having 9 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B3: A 18-carbon alkyl ether having 13 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B4: Tribenzyl phenyl ether having 14 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B5: A 12-14-carbon secondary alkyl ether having 5 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B6: A 12-14-carbon secondary alkyl ether having 9 moles of oxyethylene groups added. (Poly)oxyalkylene Derivative B7: A 12-14-carbon secondary alkyl ether having 12 moles of oxyethylene groups added. (Poly)oxyalkylene derivative B8: Polyoxyethylene polyoxypropylene butyl ether (PO / EO=50 / 50, weight average molecular weight 540) (Poly)oxyalkylene derivative B9: Branched decyl ether having 4 moles of oxyethylene groups added (Poly)oxyalkylene derivative B10: Nonylphenyl ether having 5 moles of oxyethylene groups added (Poly)oxyalkylene derivative B11: Bisphenol A ether having 10 moles of oxyethylene groups added (Poly)oxyalkylene derivative B12: Polyoxyethylene polyoxypropylene polyether (PO / EO=25 / 75, weight average molecular weight 12000) (Poly)oxyalkylene derivative B13: Secondary alkyl ether having 12 to 14 carbon atoms having 7 moles of oxyethylene groups added (Poly)oxyalkylene derivative B14: Polymer of polyoxyethylene bisphenol A ether, adipic acid, and coconut oil fatty acid

[0086] <Bronsted Acid Compounds (C)> Bronsted Acid Compound C1: Acetic Acid Bronsted Acid Compound C2: Phosphoric Acid Bronsted Acid Compound C3: Benzoic Acid Bronsted Acid Compound C4: Arginine Bronsted Acid Compound C5: C12 alkyl ether acetic acid to which 4.5 moles of oxyethylene groups have been added Bronsted Acid Compound C6: C12 alkyl ether acetic acid to which 10 moles of oxyethylene groups have been added Bronsted Acid Compound C7: C12-C15 secondary alkyl ether phosphate to which 6 moles of oxyethylene groups have been added Bronsted Acid Compound C8: C12-C15 secondary alkyl ether phosphate to which 9 moles of oxyethylene groups have been added Bronsted Acid Compound C9: C11-C15 secondary alkyl ether phosphate to which 12 moles of oxyethylene groups have been added

[0087] <Other Components (D)> Antioxidant D1: triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate Antioxidant D2: dioleyl thiodipropionate Antistatic agent D3: ethylenebis(hydroxyethyl)octadecylammonium ethyl sulfate Acetylenic surfactant D4: acetylene surfactant Preservative D5: isothiazolinone preservative (manufactured by Thor Japan Co., Ltd., trade name ACTICIDE (registered trademark) MV4) Alkyl ester D6: triisodecyl trimellitate Alkyl ester D7: sunflower oil Alkyl ester D8: hexaester of dipentaerythritol and 3,5,5-trimethylhexanoic acid Wax D9: paraffin wax (melting point 61°C)

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] As can be seen from Tables 1 to 5, the treating agents for carbon fiber precursors in Examples 1 to 44 contained silicone (A) and a (poly)oxyalkylene derivative (B) and satisfied the following conditions 1 and 2. Therefore, even when using treating agents that had been stored for a long period after preparation, fuzz and thread breakage could be reduced when producing carbon fiber precursors and carbon fibers. On the other hand, when condition 1 was not satisfied (Comparative Example 1), condition 2 was not satisfied (Comparative Example 4), conditions 1 and 2 were not satisfied (Comparative Examples 2, 3, 5, and 6), or silicone (A) was not included (Comparative Example 7), fuzz and thread breakage could not be reduced when producing carbon fiber precursors and carbon fibers using treating agents that had been stored for a long period after preparation.

[0094] 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 treating agent for carbon fiber precursors, containing silicone (A) and (poly)oxyalkylene derivative (B) and satisfying the following Condition 1 and Condition 2. Condition 1: The absorbance (X1) at 600 nm when it is made into an aqueous dispersion with a non-volatile content concentration of 1% by weight is 0.07 to 1.

0. Condition 2: The absorbance (X2) at 900 nm when it is made into an aqueous dispersion with a non-volatile content concentration of 5% by weight is 0.05 to 0.

8.

2. The non-volatile content of the treatment agent is １ In the spectrum measured by H-NMR, the ratio (Y2 / Y1) of the area (Y2) of the peak within the range of -0.3 to 0.3 ppm to the area (Y1) of the peak within the range of 0.4 to 0.7 ppm is 100 to 1200. The treatment agent for carbon fiber precursor according to claim 1.

3. The non-volatile content of the treatment agent １ In the spectrum measured by H-NMR, the ratio (Z2 / Z1) of the area (Z2) of the peak within the range of -0.3 to 0.3 ppm to the area (Z1) of the peak within the range of 3.5 to 4.0 ppm is 5 to 13. The treatment agent for carbon fiber precursor according to claim 1 or 2.

4. The treating agent for carbon fiber precursors according to any one of claims 1 to 3, wherein the surface tension when the treating agent is made into an aqueous dispersion with a non-volatile content concentration of 1% by weight is 20 to 35 mN / m.

5. The treating agent for carbon fiber precursors according to any one of claims 1 to 4, wherein the proportion of the silicone (A) in the non-volatile content of the treating agent is 50% to 95% by weight, and the proportion of the derivative (B) is 5% to 25% by weight.

6. The treating agent for carbon fiber precursors according to any one of claims 1 to 5, further containing a Bronsted acid compound (C).

7. The treating agent for carbon fiber precursors according to any one of claims 1 to 6, wherein the derivative (B) contains a compound having a structure in which 2 to 4 carbon atoms alkylene oxide is added to at least one selected from alcohols having 6 to 20 carbon atoms having 1 to 3 hydroxy groups and phenols having 6 to 20 carbon atoms having 1 to 3 hydroxy groups.

8. A carbon fiber precursor obtained by attaching the treating agent for carbon fiber precursors according to any one of claims 1 to 7 to a raw material carbon fiber precursor of the carbon fiber precursor.

9. A method for producing carbon fibers, including a flame-resistant treatment step of converting the carbon fiber precursor according to claim 8 into a flame-resistant fiber, and a carbonization treatment step of further carbonizing the flame-resistant fiber.

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