JP2024063057A - Treatment agent for acrylic fibers and use of the same - Google Patents

Abstract

To provide a treatment agent for acrylic fibers with which it is possible to improve bundling properties of acrylic fibers for manufacturing carbon fibers in a step for enhancing the flame resistance of the acrylic fibers for manufacturing carbon fibers; acrylic fibers for manufacturing carbon fibers in which the treatment agent is used; and a method for manufacturing carbon fibers using the treatment agent.SOLUTION: A treatment agent for acrylic fibers according to the present invention contains: amino-modified silicone (A); and at least one selected from compounds (B) that have five-member ring structures including sulfur atoms and nitrogen atoms, and derivatives of the compounds (B). Acrylic fibers for manufacturing carbon fibers according to the present invention are obtained by bonding the treatment agent for acrylic fibers according to the present invention to raw-material acrylic fibers of the acrylic fibers for manufacturing carbon fibers.SELECTED DRAWING: None

Description

The present invention relates to a treatment agent for acrylic fibers and its uses. More specifically, the present invention relates to a treatment agent used in the production of acrylic fibers, acrylic fibers for carbon fiber production using the treatment agent (hereinafter sometimes referred to as precursors), and a method for producing carbon fibers using the treatment agent.

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 applications, sports applications, general industrial applications, and the like.
The method of producing carbon fiber is to first produce acrylic fiber (sometimes called precursor) for carbon fiber production (the manufacturing process of this precursor is sometimes called spinning process). This precursor is generally converted into flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C (this process is sometimes called flame-resistant treatment process hereinafter), and then carbonized in an inert atmosphere at 300 to 2000°C (this process is sometimes called carbonization treatment process hereinafter) (hereinafter, the flame-resistant treatment process and carbonization treatment process are sometimes collectively called baking process). The production of this precursor goes through a drawing process in which it is drawn at a higher ratio than normal acrylic fiber. At that time, the fibers are likely to stick together, and the high-ratio drawing is not performed uniformly, resulting in a non-uniform precursor. There is a problem that the carbon fiber obtained by baking such a precursor does not have sufficient strength. In addition, there is a problem that fusion occurs between single fibers during the baking of the precursor, which reduces the quality and grade of the obtained carbon fiber.

Many techniques have been proposed for applying treatments to precursors to prevent the precursor from sticking and the carbon fibers from fusing, including silicone-based treatments that reduce fiber-to-fiber friction in wet and high-temperature environments, and amino-modified silicone-based treatments that can improve fusing prevention (see Patent Documents 1 and 2).

Japanese Patent Publication No. 2001-172879 Japanese Patent Publication No. 2002-129481

However, when flame-retardant treatment is performed using a precursor to which such a treatment agent has been added, there is a problem that the bundle strength of the precursor is reduced due to the peeling action of the silicone and the action of reducing friction between fibers. As a result, insufficient bundle strength may cause disorder of the fiber bundle and uneven drawing during the flame-retardant treatment process and carbonization treatment process, which may cause deterioration in workability, process passability, and quality of the carbon fiber.
Therefore, an object of the present invention is to provide a treatment agent for acrylic fibers that can improve the bundling ability of acrylic fibers for use in carbon fiber production in a flame-retardant process for acrylic fibers for use in carbon fiber production, acrylic fibers for use in carbon fiber production using said treatment agent, and a method for producing carbon fibers using said treatment agent.

As a result of intensive research to solve the above problems, the present inventors have discovered that an acrylic fiber treatment agent containing an amino-modified silicone (A) and at least one selected from a compound (B) having a five-membered ring structure containing a sulfur atom and a nitrogen atom and a derivative of said compound (B) can improve the bundling of precursors in the flame-retardant process of acrylic fibers for carbon fiber production, and have arrived at the present invention.

（式（１）中、Ｒ^１は、炭素数１～１２のアルキル基、アラルキル基又は水素原子であり、Ｘ及びＹは独立して水素原子又はハロゲン原子である。）

（式（２）中、Ｒ^２は、炭素数１～８のアルキル基又は水素原子である。）
＜３＞ブレンステッド酸化合物（Ｃ）をさらに含有する、＜１＞又は＜２＞に記載のアクリル繊維用処理剤。
＜４＞前記ブレンステッド酸化合物（Ｃ）が、カルボン酸化合物、無機酸、スルホン酸化合物、リン酸エステル化合物、硫酸エステル化合物及びホスホン酸化合物から選ばれる少なくとも１種を含む、＜３＞に記載のアクリル繊維用処理剤。
＜５＞前記アミノ変性シリコーン（Ａ）のアミノ基に対する、前記ブレンステッド酸化合物（Ｃ）のモル比が、０．０１～５．０である、＜３＞又は＜４＞に記載のアクリル繊維用処理剤。
＜６＞前記ブレンステッド酸化合物（Ｃ）１００重量部に対する、前記化合物（Ｂ）及び前記化合物（Ｂ）の誘導体の合計の重量が０．０１～５０重量部である、＜３＞～＜５＞のいずれかに記載のアクリル繊維用処理剤。
＜７＞親水性溶媒（Ｄ）をさらに含有し、前記親水性溶媒（Ｄ）が下記一般式（３）で表される化合物及び非プロトン性含窒素有機化合物から選ばれる少なくとも１種を含む、＜１＞～＜６＞のいずれかに記載のアクリル繊維用処理剤。

（式（３）中、ＡＯは炭素数２～４のオキシアルキレン基であり、ｎは１～３の整数である。）
＜８＞処理剤の不揮発分に占める前記アミノ変性シリコーン（Ａ）の重量割合が２０～９０重量％である、＜１＞～＜７＞のいずれかに記載のアクリル繊維用処理剤。
＜９＞非イオン性界面活性剤（Ｅ）をさらに含有する、＜１＞～＜８＞のいずれかに記載のアクリル繊維用処理剤。
＜１０＞炭素繊維製造用アクリル繊維の原料アクリル繊維に、＜１＞～＜９＞のいずれかに記載のアクリル繊維用処理剤を付着させてなる、炭素繊維製造用アクリル繊維。
＜１１＞＜１０＞に記載の炭素繊維製造用アクリル繊維を、２００～３００℃の酸化性雰囲気中で耐炎化繊維に転換する耐炎化処理工程と、前記耐炎化繊維をさらに３００～２０００℃の不活性雰囲気中で炭化させる炭素化処理工程とを含む、炭素繊維の製造方法。 That is, the treating agent for acrylic fibers of the present invention includes the following embodiments.
<1> A treatment agent for acrylic fibers, comprising an amino-modified silicone (A) and at least one selected from a compound (B) having a five-membered ring structure containing a sulfur atom and a nitrogen atom and a derivative of the compound (B).
<2> The treatment agent for acrylic fibers according to <1>, wherein the compound (B) includes at least one selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2):

In formula (1), R ¹ is an alkyl group or an aralkyl group having 1 to 12 carbon atoms, or a hydrogen atom, and X and Y are each independently a hydrogen atom or a halogen atom.

(In formula (2), ^R2 is an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.)
<3> The treatment agent for acrylic fibers according to <1> or <2>, further comprising a Bronsted acid compound (C).
<4> The treatment agent for acrylic fibers according to <3>, wherein the Bronsted acid compound (C) includes at least one selected from the group consisting of a carboxylic acid compound, an inorganic acid, a sulfonic acid compound, a phosphoric acid ester compound, a sulfuric acid ester compound, and a phosphonic acid compound.
<5> The treatment agent for acrylic fibers according to <3> or <4>, in which a molar ratio of the Bronsted acid compound (C) to the amino groups of the amino-modified silicone (A) is 0.01 to 5.0.
<6> The treatment agent for acrylic fibers according to any one of <3> to <5>, in which a total weight of the compound (B) and the derivative of the compound (B) is 0.01 to 50 parts by weight based on 100 parts by weight of the Bronsted acid compound (C).
<7> The treatment agent for acrylic fibers according to any one of <1> to <6>, further comprising a hydrophilic solvent (D), the hydrophilic solvent (D) including at least one selected from the group consisting of a compound represented by the following general formula (3) and an aprotic nitrogen-containing organic compound:

(In formula (3), AO is an oxyalkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 3.)
<8> The treatment agent for acrylic fibers according to any one of <1> to <7>, wherein the weight ratio of the amino-modified silicone (A) to the non-volatile content of the treatment agent is 20 to 90% by weight.
<9> The treatment agent for acrylic fibers according to any one of <1> to <8>, further comprising a nonionic surfactant (E).
<10> An acrylic fiber for carbon fiber production, comprising a raw acrylic fiber for carbon fiber production, and the treating agent for acrylic fiber according to any one of <1> to <9> adhered to the raw acrylic fiber.
<11> A method for producing carbon fibers, comprising: a flame-retardant treatment step of converting the acrylic fiber for carbon fiber production according to <10> into a flame-retardant fiber in an oxidizing atmosphere at 200 to 300°C; and a carbonization treatment step of further carbonizing the flame-retardant fiber in an inert atmosphere at 300 to 2000°C.

When the acrylic fiber treatment agent of the present invention is applied to acrylic fiber for carbon fiber production, and the acrylic fiber produced by the treatment agent is used, the bundling property of the acrylic fiber for carbon fiber production in the flame-resistant process can be improved, and the disorder and uneven stretching of the fiber bundles due to insufficient bundling property can be improved. When the acrylic fiber for carbon fiber production of the present invention is used, the disorder and uneven stretching of the fiber bundles can be improved by improving the bundling property in the flame-resistant treatment process, and workability and process passability can be improved. According to the carbon fiber production method of the present invention, the disorder and uneven stretching of the fiber bundles can be improved by improving the bundling property, and workability and process passability can be improved, resulting in high-quality carbon fiber.

Each component of the treating agent for acrylic fibers of the present invention will now be described.
[Amino-modified silicone (A)]
The treatment agent of the present invention contains an amino-modified silicone (A). The amino group (including an organic group having an amino group) which is a modified group of the amino-modified silicone may be bonded to the side chain of the silicone main chain, or may be bonded to the end, or may be bonded to both, but from the viewpoint of fiber protection in the flame-resistant treatment process, it is preferable that it is bonded to the side chain (having an amino group on the side chain). In addition, the amino group may be any of a monoamine type, a diamine type, and 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-resistant treatment process and protecting the fiber by forming a film with the treatment agent, the monoamine type or the diamine type is preferable. In addition, the amino-modified silicone may contain an amino polyether-modified silicone. The amino polyether-modified silicone is a silicone having at least one amino group and a polyether group in its structure.

The kinetic viscosity of the amino-modified silicone (A) at 25°C is preferably 50 to 20,000 mm ² /s in terms of uniform adhesion to fibers, inhibition of scattering of the treatment agent, and imparting focusing properties to fibers. The upper limit of the kinetic viscosity is more preferably 15,000 mm ² /s, even more preferably 10,000 mm ² /s, and particularly preferably 8,000 mm ² /s. On the other hand, the lower limit of the kinetic viscosity is more preferably 100 mm ² /s, even more preferably 150 mm ² /s, and particularly preferably 200 mm ² /s. Also, for example, 200 to 10,000 mm ² /s is more preferable, and 200 to 8,000 mm ² /s is even more preferable.

The amino equivalent of the amino-modified silicone (A) 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. On the other hand, 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. Also, 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 means the mass of the siloxane skeleton per one amino group or ammonium group. The unit of g/mol is a value converted per 1 mol of amino group or ammonium group. Therefore, the smaller the amino equivalent value, the higher the ratio of amino group or ammonium group in the molecule.

Amino-modified silicone (A) may be used in combination with multiple amino-modified silicones with different amino equivalents and kinetic viscosities (25°C). When two or more types of amino-modified silicones are used, the above amino equivalent refers to the amino equivalent of the entire amino-modified silicone (mixture), and the above kinetic viscosity at 25°C refers to the kinetic viscosity of the entire amino-modified silicone (mixture).

The amino-modified silicone may be, for example, a compound represented by the following general formula (4):

（式（４）中、Ｒ^３は炭素数が１～２０のアルキル基又はアリール基を示す。Ｒ^４は下記一般式（５）で示される基である。Ｒ^５は、Ｒ^３、Ｒ^４又は－ＯＲ^１１（Ｒ^１１は水素原子又は炭素数が１～６のアルキル基）である。ｐは５≦ｐ≦１００００、ｑは０≦ｑ≦１０００である。ただし、ｑ＝０の場合、Ｒ^５のうち少なくとも１つは下記一般式（５）で示される基である。）

(In formula (4), R ³ represents an alkyl group or an aryl group having 1 to 20 carbon atoms. R ⁴ represents a group represented by the following general formula (5). R ⁵ represents R ³ , R ⁴ or -OR ¹¹ (R ¹¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms). p represents 5≦p≦10000, and q represents 0≦q≦1000. However, when q=0, at least one of R ⁵ represents a group represented by the following general formula (5).)

In formula (4), R ³ represents an alkyl group or an aryl group having 1 to 20 carbon atoms. R ³ 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. Note that, multiple R ^3s in formula (4) may be the same or different. R ⁴ is a group represented by the following general formula (5). R ⁵ is a group represented by R ³ , R ⁴ , or -OR ¹¹ , and is preferably R ^3. Note that, multiple R ^11s in formula (4) may be the same or different.
^R11 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 0.1 to 500, and more preferably 0.2 to 100.

In formula (5), ^R6 and ^R8 are each independently an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 1 to 3 carbon atoms. ^R7 , ^R9 and ^R10 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.

[Compound (B) having a 5-membered ring structure containing a sulfur atom and a nitrogen atom, and derivatives of compound (B)]
The treatment agent of the present invention contains at least one selected from compound (B) having a five-membered ring structure containing a sulfur atom and a nitrogen atom (hereinafter, sometimes referred to as compound (B)) and derivatives of compound (B).
The compound (B) is not particularly limited as long as it is a compound having a five-membered ring structure containing a sulfur atom and a nitrogen atom, but from the viewpoint of improving the collectibility of the fiber bundle by the treatment agent in the flame-resistant step, it is preferable for the compound (B) to have a bond between heteroatoms in the five-membered ring, since this further promotes the crosslinking reaction of the amino-modified silicone (A) and improves the collectibility of the fiber bundle, it is preferable for the compound (B) to have a nitrogen-sulfur bond in the five-membered ring, since this further promotes the crosslinking reaction and improves the collectibility of the fiber bundle, and it is particularly preferable for the compound (B) to contain at least one compound selected from the compounds represented by the following general formula (1) and the following general formula (2), since this further promotes the crosslinking reaction and improves the collectibility of the fiber bundle.
The derivative of compound (B) is not particularly limited as long as it is a derivative of compound (B), and examples thereof include a product in which compound (B) forms a salt and a reaction product of compound (B) with a compound having nucleophilicity.
It is believed that the reason why the bundling ability of the fiber bundle is improved is that when a bond between heteroatoms is present in the five-membered ring structure, the bond between the heteroatoms is cleaved by heat, and the radicals generated by the cleavage further promote the crosslinking reaction of the amino-modified silicone (A). It is believed that when the bond between the heteroatoms is a nitrogen-sulfur bond, the cleavage of the bond between the heteroatoms is further promoted, and that the cleavage of the bond between the heteroatoms is particularly promoted in the case of compounds represented by the following general formulas (1) and (2). It is believed that the reason why the derivative of compound (B) further improves the bundling ability of the fiber bundle is that the derivative is decomposed by heat, and the radicals generated by the decomposition promote the crosslinking reaction of the amino-modified silicone (A).
The compound (B) may contain one type or two or more types, and it is more preferable to contain two or more types in terms of excellent abrasion resistance.

In formula (1), it is preferable that R ¹ is an alkyl group having 1 to 12 carbon atoms, an aralkyl group, or a hydrogen atom, and X and Y are independently a hydrogen atom or a halogen atom in terms of achieving the effects of the present invention.
R ¹ is more preferably an alkyl group having 1 to 10 carbon atoms, an aralkyl group, or a hydrogen atom, and particularly preferably an alkyl group having 1 to 8 carbon atoms, or a hydrogen atom.
Specific examples of ^R1 include a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a phenyl group, and a hydrogen atom. In terms of compatibility with the amino-modified silicone, a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, or a hydrogen atom is more preferable, and a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, or a hydrogen atom is particularly preferable.
In formula (1), X and Y are each preferably independently a hydrogen atom, a chlorine atom, or a bromine atom, and more preferably a hydrogen atom or a chlorine atom.
When at least one of X and Y is a hydrogen atom, in terms of compatibility with the amino-modified silicone, ^R1 is more preferably a methyl group, ethyl group, isopropyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, or hydrogen atom, and even more preferably a methyl group, ethyl group, isopropyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, or hydrogen atom.

In formula (2), R ² is preferably an alkyl group having 1 to 8 carbon atoms or a hydrogen atom in terms of achieving the effects of the present application, more preferably an alkyl group having 1 to 6 carbon atoms or a hydrogen atom, and particularly preferably an alkyl group having 1 to 4 carbon atoms.
Specific examples of ^R2 include a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a hydrogen atom. In terms of compatibility with the amino-modified silicone, a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or a hydrogen atom is more preferable, and a methyl group, an ethyl group, an isopropyl group, a propyl group, a butyl group, or a hydrogen atom is particularly preferable.

Examples of the compound (B) include the compounds represented by the general formulas (1) and (2) as well as thiazoles and thiadiazoles.
The thiazoles include 4-bromothiazole, 4-methylthiazole, 2,4-dichlorothiazole, 2-methyl-4-methylthiazole, 2-isopropyl-4-methylthiazole, 2-methyl-4-methylthiazole, 2-mercaptothiazole, 2-aminothiazole, 2-methylthiazole, 2-ethylthiazole, 2-propionylthiazole, 2-acetylthiazole, 5-methylthiazole, 2,5-dibromothiazole, and 5-(2-hydroxyethyl)-4-methylthiazole.
Thiadiazoles include 2-amino-1,3,4-thiadiazole, 1,3,4-thiadiazole-2-thiol, 1,3,4-thiadiazole-2,5-diamine, 2-amino-5-mercapto-1,3,4-thiadiazole, and 5-methyl-1,3,4-thiadiazole-2-thiol.

Examples of salts of compound (B), which are derivatives of compound (B), include sodium salts, potassium salts, calcium salts, and amine salts. Examples of nucleophilic compounds that produce derivatives of compound (B) include compounds having at least one group selected from a thiol group, an amino group, and an alkoxyl group, and specific examples thereof include organic thiol compounds, organic amine compounds, organic alcohol compounds, and amino acid compounds, and examples of the organic groups include alkyl groups, alkenyl groups, and aryl groups.

[Bronsted Acid Compound (C)]
The fiber treatment agent of the present invention preferably contains a Bronsted acid compound (C) in that it inhibits the decomposition over time of compound (B) and derivatives of compound (B) and improves the strength of the carbon fiber. The Bronsted acid compound (C) refers to a proton donor, and examples of the compound (C) include carboxylic acid compounds, inorganic acids, sulfonic acid compounds, phosphoric acid ester compounds, sulfuric acid ester compounds, and phosphonic acid compounds.

Carboxylic acid compounds are compounds that have a carboxyl group in their molecular structure. Examples of carboxylic acid compounds include, but are not limited to, aliphatic monocarboxylic acids, alkyl ether carboxylic acids, aliphatic polycarboxylic acids, aromatic monocarboxylic acids, aromatic polycarboxylic acids, and amino acids.

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, isoeicosaic acid, gadoleic acid, eicosenoic acid, docosanoic acid, isodocosanoic acid, erucic acid, tetracosanoic acid, isotetracosanoic acid, nervonic acid, cerotic acid, montanic acid, and melissic acid.

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 moles. Examples of the alkyl group include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of the polyoxyalkylene group include polyoxyethylene, polyoxypropylene, and polyoxypolypropylene groups.

Aliphatic polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecane diacid, dodecane diacid, tridecane diacid, tetradecane diacid, pentadecanedioic acid, and derivatives thereof.

Aromatic monocarboxylic acids include benzoic acid, cinnamic acid, naphthoic acid, toluic acid, and their derivatives.

Aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and derivatives thereof.

Amino acids are compounds that have both amino and carboxyl groups in their molecular structure, and examples include alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, proline, glycine, tyrosine, serine, threonine, cysteine, asparagine, glutamine, lysine, arginine, histidine, aspartic acid, and glutamic acid.

An inorganic acid is an acid that contains nonmetallic atoms. Examples of inorganic acids include sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.

Examples of sulfonic acid compounds include alkylbenzene sulfonic acid, polyoxyalkylene alkyl ether sulfonic acid, higher fatty acid amide sulfonic acid, alkyl sulfate monoester, and polyoxyalkylene sulfate monoester.

Examples of phosphate ester compounds 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.

Examples of sulfate ester compounds include alkyl sulfate esters, polyoxyalkylene alkyl sulfate esters, alkyl phenyl sulfate esters, and polyoxyalkylene alkyl phenyl sulfate esters.

Examples of phosphonic acid compounds include alkyl phosphonic acids, aromatic phosphonic acids, and polyoxyalkylene alkyl ether phosphonic acids.

The pKa of the Bronsted 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 groups of the amino-modified silicone.

The Bronsted acid compound (C) preferably contains at least one selected from a carboxylic acid compound, a phosphate ester compound, and an inorganic acid, more preferably contains at least one selected from lactic acid, an alkyl ether carboxylic acid, a phosphate ester compound, phosphoric acid, and acetic acid, and even more preferably contains at least one selected from an alkyl ether carboxylic acid, a phosphate ester compound, acetic acid, and phosphoric acid, in order to suppress the decomposition over time of compound (B) and derivatives of compound (B). One or more Bronsted acid compounds (C) may be used.

[Hydrophilic Solvent (D)]
The treating agent for acrylic fiber of the present invention preferably contains a hydrophilic solvent (D) in order to improve the compatibility of the amino-modified silicone (A) with the compound (B) and the derivatives of the compound (B) and to improve the strength of the carbon fiber.
The hydrophilic solvent (D) is not particularly limited as long as it has a solubility in water of 0.05 g/ml or more at 25° C., but it is more preferable that the hydrophilic solvent (D) contains at least one selected from the group consisting of a compound represented by the following general formula (3) and an aprotic nitrogen-containing organic compound. One or more kinds of hydrophilic solvents (D) may be used.

In formula (3), AO is an oxyalkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 3.
The compound represented by general formula (3) is preferably at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol, and more preferably at least one selected from ethylene glycol, diethylene glycol and propylene glycol, in that the compatibility of the amino-modified silicone (A) with the compound (B) or a derivative of the compound (B) is improved and the effects of the present application are more easily obtained. One or more of the compounds represented by general formula (3) may be used.

From the viewpoint of improving the compatibility between the amino-modified silicone (A) and the compound (B) or a derivative of the compound (B), the aprotic nitrogen-containing organic compound is preferably at least one selected from N,N-dimethylformamide, 1-methyl-2-pyrrolidone, N,N-dimethylacetamide, and acetonitrile, and more preferably at least one selected from 1-methyl-2-pyrrolidone and N,N-dimethylformamide. One or more types of aprotic nitrogen-containing organic compounds may be used.

[Acrylic fiber treatment agent]
The treatment agent for acrylic fibers of the present invention contains the above-mentioned amino-modified silicone (A) and at least one selected from compound (B) and compound (B), and may further contain at least one selected from a Brønsted acid compound (C) and a hydrophilic solvent (D).

The reason why the acrylic fiber treatment agent of the present invention improves the bundling ability of acrylic fibers by containing amino-modified silicone (A) and at least one selected from compound (B) and a derivative of compound (B) is believed to be that compound (B) or a derivative of compound (B) appropriately promotes the crosslinking reaction of amino-modified silicone (A) in the flame-resistant process, resulting in a balanced increase in the molecular weight and viscosity of the amino-modified silicone.

The total weight percentage of compound (B) and derivatives of compound (B) in the non-volatile content of the treatment agent of the present invention is preferably 0.001 to 1% by weight in order to promote the crosslinking reaction of the amino-modified silicone in the flame-proofing process. The upper limit of the weight percentage is more preferably 0.5% by weight, even more preferably 0.1% by weight, particularly preferably 0.07% by weight, and most preferably 0.04% by weight. On the other hand, the lower limit of the weight percentage is more preferably 0.005% by weight, even more preferably 0.008% by weight, particularly preferably 0.01% by weight, and most preferably 0.02% by weight. Also, for example, 0.005 to 0.5% by weight is more preferable, and 0.008 to 0.04% by weight is even more preferable.

The weight ratio of the amino-modified silicone (A) in the non-volatile content of the treatment agent of the present invention is preferably 20 to 90% by weight in order to impart high bundling ability to the fiber bundle. The upper limit of the weight ratio is more preferably 85% by weight, and particularly preferably 80% by weight. On the other hand, the lower limit of the weight ratio is more preferably 30% by weight, even more preferably 40% by weight, and particularly preferably 50% by weight. Also, for example, 40 to 90% by weight is more preferable, and 50 to 90% by weight is even more preferable.

The total weight of compound (B) and derivatives of compound (B) per 100 parts by weight of amino-modified silicone (A) is preferably 0.001 to 5 parts by weight in order to promote the crosslinking reaction of the amino-modified silicone in the flame-proofing process. The upper limit of the weight is more preferably 1.0 part by weight, even more preferably 0.5 part by weight, and particularly preferably 0.25 part by weight. On the other hand, the lower limit of the weight is more preferably 0.003 part by weight, even more preferably 0.005 part by weight, and particularly preferably 0.007 part by weight. Also, for example, 0.003 to 0.5 parts by weight is more preferable, and 0.003 to 0.25 parts by weight is even more preferable.

When the treatment agent of the present invention further contains a Bronsted acid compound (C), the molar ratio of the Bronsted acid compound (C) to the amino groups of the amino-modified silicone (A) is preferably 0.01 to 5.0 in terms of storage stability of the treatment agent. The upper limit of the ratio is more preferably 4.5, even more preferably 4.0, particularly preferably 3.5, and most preferably 2.5. On the other hand, the lower limit of the ratio is more preferably 0.05, even more preferably 0.1, particularly preferably 0.2, and most preferably 0.3. Also, for example, 0.05 to 4.5 is more preferable, and 0.1 to 4.0 is even more preferable. The molar ratio of the Bronsted acid compound (C) to the amino groups of the amino-modified silicone (A) refers to the ratio of the total number of moles of the Bronsted acid compound (C) to the total number of moles of the amino groups of the amino-modified silicone (A) contained in the treatment agent.

The total weight of compound (B) and derivatives of compound (B) relative to 100 parts by weight of the Bronsted acid compound (C) is preferably 0.01 to 50 parts by weight in order to suppress the decomposition of compound (B) and derivatives of compound (B) over time. The upper limit of the weight is more preferably 30 parts by weight, even more preferably 20 parts by weight, and particularly preferably 10 parts by weight. On the other hand, the lower limit of the weight is more preferably 0.05 parts by weight, even more preferably 0.1 parts by weight, and particularly preferably 0.3 parts by weight. Also, for example, 0.05 to 30 parts by weight is more preferable, and 0.1 to 20 parts by weight is even more preferable.

The weight ratio of the Bronsted acid compound (C) in the non-volatile content of the treatment agent of the present invention is preferably 0.02 to 30% by weight in order to suppress the decomposition over time of compound (B) and derivatives of compound (B). The upper limit of the weight ratio is more preferably 26% by weight, even more preferably 20% by weight, and particularly preferably 15% by weight. On the other hand, the lower limit of the weight ratio is more preferably 0.05% by weight, even more preferably 0.1% by weight, and particularly preferably 0.3% by weight. Also, for example, 0.05 to 15% by weight is more preferable, and 0.1 to 15% by weight is even more preferable.

When the treatment agent of the present invention further contains a hydrophilic solvent (D), the weight ratio of the hydrophilic solvent (D) to the non-volatile content of the treatment agent of the present invention is preferably 0.05 to 10% by weight in terms of improving the compatibility between the amino-modified silicone (A) and at least one selected from the compound (B) and a derivative of the compound (B). The upper limit of the weight ratio is more preferably 7% by weight, even more preferably 5% by weight, and particularly preferably 3% by weight. On the other hand, the lower limit of the weight ratio is more preferably 0.07% by weight, even more preferably 0.1% by weight, and particularly preferably 0.15% by weight. Also, for example, 0.05 to 7% by weight is more preferable, and 0.07 to 5% by weight is even more preferable.

[Nonionic Surfactant (E)]
The treatment agent of the present invention preferably further contains a nonionic surfactant (E) from the viewpoint of enhancing emulsifiability. Examples of the nonionic surfactant (E) include polyoxyalkylene linear alkyl ethers such as polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene tetradecyl ether, and polyoxyethylene cetyl ether; polyoxyalkylene branched primary alkyl ethers such as polyoxyethylene 2-ethylhexyl ether, polyoxyethylene isocetyl ether, and polyoxyethylene isostearyl ether; polyoxyethylene 1-hexylhexyl ether, polyoxyethylene 1-octylhexyl ether, and polyoxyethylene 1-octylhexyl ether; polyoxyalkylene secondary alkyl ethers such as polyoxyethylene 1-hexyl octyl ether, polyoxyethylene 1-pentyl heptyl ether, polyoxyethylene 1-heptyl pentyl ether, polyoxyethylene 1-hexyl heptyl ether, polyoxyethylene 1-heptyl hexyl ether, polyoxyethylene 1-pentyl captyl ether, and polyoxyethylene 1-captyl pentyl ether; polyoxyethylene oleyl ether and other polyoxyalkylene alkenyl ethers; polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and polyoxyethylene dodecyl phenyl ether; polyoxyethylene tristyryl phenyl ether, polyoxyethylene distyryl ether, and other polyoxyethylene tertyl ethers. polyoxyalkylene alkylaryl phenyl ethers such as polyoxyethylene styryl phenyl ether, polyoxyethylene tribenzyl phenyl ether, polyoxyethylene dibenzyl phenyl ether, and polyoxyethylene benzyl phenyl ether; acetylene surfactants in which alkylene oxide is added to acetylene alcohol or acetylene diol; polyoxyalkylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monooleate, polyoxyethylene monostearate, polyoxyethylene monomyristate, polyoxyethylene dilaurate, polyoxyethylene diolate, polyoxyethylene dimyristate, and polyoxyethylene distearate; sorbitan monopalmitate. sorbitan esters such as sorbitan monooleate and the like; polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monostearate and polyoxyethylene sorbitan monooleate; glycerin fatty acid esters such as glycerin monostearate, glycerin monolaurate, glycerin monopalmitate and the like; polyoxyalkylene sorbitol fatty acid esters; sucrose fatty acid esters; polyoxyalkylene castor oil ethers such as polyoxyethylene castor oil ether; polyoxyalkylene hydrogenated castor oil ethers such as polyoxyethylene hydrogenated castor oil ether; oxyethylene-oxypropylene block or random copolymers; and sucrose-etherified products of oxyethylene-oxypropylene block or random copolymers at their terminals.

Among these, from the viewpoint of emulsion stability, it is preferable to include at least one selected from polyoxyalkylene linear primary alkyl ethers, polyoxyalkylene linear secondary alkyl ethers, polyoxyalkylene branched primary alkyl ethers, polyoxyalkylene branched secondary alkyl ethers, polyoxyalkylene alkyl phenyl ethers, polyoxyalkylene alkylaryl phenyl ethers, and acetylene surfactants, and it is preferable to include at least one selected from polyoxyalkylene linear primary alkyl ethers, polyoxyalkylene linear secondary alkyl ethers, polyoxyalkylene branched primary alkyl ethers, and polyoxyalkylene branched secondary alkyl ethers.
The weight average molecular weight of the nonionic surfactant (E) is preferably 2000 or less, more preferably 200 to 1800, more preferably 300 to 1500, and even more preferably 500 to 1000. One or more types of nonionic surfactants may be used.

When the treatment agent of the present invention contains a nonionic surfactant (E), the weight percentage of the nonionic surfactant (E) in the nonvolatile content of the treatment agent is preferably 5 to 75% by weight in terms of emulsion stability. The upper limit of the weight percentage is more preferably 60% by weight, even more preferably 50% by weight, and particularly preferably 40% by weight. On the other hand, the lower limit of the weight percentage is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Also, for example, 5 to 50% by weight is more preferable, and 10 to 40% by weight is even more preferable.

[Other surfactants]
The acrylic fiber treatment agent of the present invention may contain a surfactant other than the above nonionic surfactant and the Bronsted acid compound (C) within a range that does not impair the effects of the present invention. The surfactant is used as an emulsifier, an antistatic agent, etc. The other surfactant is not particularly limited, and a known surfactant may be appropriately selected from anionic surfactants, cationic surfactants, and amphoteric surfactants and used. The surfactant may be one type, or two or more types may be used in combination.

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 hydroxyloxyacetic 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); polyoxyethylene 2-ethylhexyl ether acetate (sodium salt); polyoxyalkylene alkyl ether sulfonic acids (salts) such as silyl 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 N (sodium), palmitoyl methyl taurine (sodium); N-acyl sarcosinic acids (salts) such as lauroyl sarcosinic acid (sodium); alkyl phosphonic acids (salts) such as octyl phosphonate (potassium salt); aromatic phosphonic acids (salts) such as phenyl phosphonate (potassium salt); 2-ethylhexyl phosphonate mono 2-ethylhexyl ester (potassium salt) and the like. alkylphosphonic acid alkyl phosphate esters (salts); nitrogen-containing alkyl phosphonic 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); alkyl phosphate esters (salts) such as lauryl phosphate (potassium salt), cetyl phosphate (potassium salt), and stearyl phosphate (diethanolamine salt); polyoxyethylene lauryl ether phosphate (potassium salt), polyoxyethylene oleyl ether phosphate Examples of suitable phosphates include polyoxyalkylene alkyl (alkenyl) ether phosphate esters (salts) such as polyoxyethylene nonyl phenyl ether phosphate (triethanolamine salt); polyoxyalkylene alkyl phenyl ether phosphate esters (salts) such as polyoxyethylene nonyl phenyl ether phosphate (potassium salt) and polyoxyethylene dodecyl phenyl ether phosphate (potassium salt); long-chain sulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate and sodium dioctyl sulfosuccinate; long-chain N-acyl glutamate salts such as sodium monosodium N-lauroyl glutamate and disodium N-stearoyl-L-glutamate; and the like.

Among these, from the viewpoint of emulsion stability, it is preferable to include at least one selected from polyoxyalkylene alkyl ether acetate (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), alkylbenzene sulfonic acid (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), and alkyl phosphate ester (salt), and it is preferable to include at least one selected from polyoxyalkylene alkyl ether acetate (salt), polyoxyalkylene alkyl ether sulfonic acid (salt), and alkyl phosphate ester (salt).

Examples of cationic surfactants include 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 dimethylethyl ammonium ethosulfate, dioctyl dimethyl ammonium chloride, dilauryl dimethyl ammonium chloride, distearyl dimethyl ammonium chloride, octadecyl diethyl methyl ammonium sulfate, etc. alkyl quaternary ammonium salts of the above; (polyoxyalkylene) alkyl amino ether salts such as (polyoxyethylene) lauryl amino ether lactate, stearyl amino ether lactate, di(polyoxyethylene) lauryl methyl amino ether dimethyl phosphate, di(polyoxyethylene) lauryl ethyl ammonium ethosulfate, di(polyoxyethylene) hardened beef tallow alkyl ethyl amine ethosulfate, di(polyoxyethylene) lauryl methyl ammonium dimethyl phosphate, and di(polyoxyethylene) stearyl amine lactate; acyl amido alkyl quaternary ammonium salts such as N-(2-hydroxyethyl)-N,N-dimethyl-N-stearoyl amido propyl ammonium nitrate, lanolin fatty acid amido propyl ethyl dimethyl ammonium ethosulfate, and lauroyl amido ethyl methyl diethyl ammonium methosulfate; dipalmityl poly alkylethenoxy quaternary ammonium salts such as ethenoxyethyl ammonium chloride and distearyl polyethenoxymethyl ammonium chloride; alkylisoquinolinium salts such as lauryl isoquinolinium chloride; benzalkonium salts such as lauryl dimethyl benzyl ammonium chloride and stearyl dimethyl benzyl ammonium chloride; benzethonium salts such as benzyl dimethyl {2-[2-(p-1,1,3,3-tetramethylbutylphenoxy)ethoxy]ethyl} ammonium chloride; pyridinium salts such as cetyl pyridinium chloride; imidazolinium salts such as oleyl hydroxyethyl imidazolinium ethosulfate and lauryl hydroxyethyl imidazolinium ethosulfate; acyl basic amino acid alkyl esters such as N-cocoyl arginine ethyl ester pyrrolidone carboxylate and N-lauroyl lysine ethyl ester chloride tert-butylamine salts; primary amine salts such as laurylamine chloride, stearylamine bromide, hardened beef tallow alkylamine chloride, and rosinamine acetate; 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, diethanolstearylamideethylamine trihydroxyethylphosphate salt, and stearylamideethylethanolamine urea polycondensate acetate; fatty acid amide guanidinium salts; and alkyltrialkylene glycol ammonium salts such as lauryltriethyleneglycolammonium hydroxide.

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 dimethylaminoacetate 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.

[Other ingredients]
The acrylic fiber treating agent of the present invention may contain other components in addition to the above-mentioned components, so 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 cationic surfactants and amine salt cationic surfactants, smoothing agents such as alkyl esters of higher alcohols, higher alcohol ethers, and waxes, antibacterial agents, preservatives, rust inhibitors, and moisture absorbents.

The treatment agent of the present invention may contain modified silicones other than the amino-modified silicones described above, provided that the effects of the present invention are not impaired. Examples of modified silicones include amide-modified silicones, amide polyether-modified silicones, epoxy-modified silicones, polyether-modified silicones, epoxy polyether-modified silicones (see, for example, Patent No. 4616934), carbinol-modified silicones, alkyl-modified silicones, phenol-modified silicones, methacrylate-modified silicones, alkoxy-modified silicones, and fluorine-modified silicones. One type of modified silicone may be used, or multiple modified silicones may be used in combination.

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 (5) above. These low molecular weight silicones may be included as a minor component of the amino-modified silicone (A).
The content of the low molecular weight silicone in the treatment agent of the present invention is preferably 15 parts by weight or less per 100 parts by weight of the amino-modified silicone (A).

The treating agent for acrylic fibers of the present invention is preferably in a state in which the amino-modified silicone (A), at least one selected from the compound (B) and a derivative of the compound (B), and, optionally, the Bronsted acid compound (C), the hydrophilic solvent (D) and the nonionic surfactant (E) are dissolved, solubilized, emulsified or dispersed in water.
There are no particular limitations on the weight percentage of water and the weight percentage of non-volatile matter in the entire acrylic fiber treatment agent. For example, they may be appropriately determined in consideration of the transportation cost when transporting the acrylic fiber treatment agent of the present invention, the handleability due to the emulsion viscosity, and the like. The weight percentage of water in the entire acrylic fiber treatment agent is preferably 0.1 to 99.9% by weight, more preferably 10 to 99.5% by weight, and particularly preferably 50 to 99% by weight. The weight percentage (concentration) of non-volatile matter in the entire acrylic fiber treatment agent is preferably 0.01 to 99.9% by weight, more preferably 0.5 to 90% by weight, and particularly preferably 1 to 50% by weight.

The acrylic fiber treatment agent of the present invention can be manufactured by mixing the components described above. There is no particular limitation on the method for emulsifying and dispersing the components described above, and known methods can be used. Examples of such methods include a method in which each component constituting the acrylic fiber treatment agent is added to warm water under stirring to emulsify and disperse, and a method in which each component constituting the acrylic fiber treatment agent is mixed, and water is gradually added while mechanical shear force is applied using a homogenizer, homomixer, ball mill, etc. to cause phase inversion emulsification. A method in which some of the components are emulsified and then the remaining components are dissolved and dispersed may also be used.

The acrylic fiber treatment agent of the present invention can be suitably used as a treatment agent (precursor treatment agent) for acrylic fibers (precursors) used in carbon fiber production. It may also be used as a spinning oil agent for acrylic fibers other than precursors.

[Acrylic fiber for producing carbon fiber, its manufacturing method and manufacturing method for carbon fiber]
The acrylic fiber (precursor) for carbon fiber production of the present invention is obtained by adhering the above-mentioned acrylic fiber treatment agent to the raw acrylic fiber of the precursor and spinning the resulting fiber. The method for producing the precursor of the present invention includes a spinning step of adhering the above-mentioned acrylic fiber treatment agent to the raw acrylic fiber of the precursor and spinning the resulting fiber.
The method for producing carbon fiber of the present invention includes a flame-retardant treatment step of converting the precursor having the above-mentioned acrylic fiber treating agent attached thereto into a flame-retardant fiber in an oxidizing atmosphere at 200 to 300°C, and a carbonization treatment step of further carbonizing the flame-retardant fiber in an inert atmosphere at 300 to 2000°C.
According to the carbon fiber manufacturing method of the present invention, since the treating agent for acrylic fiber of the present invention is used, bundle collection is improved, and disorder of the fiber bundle and uneven drawing are reduced, making it possible to manufacture high-quality carbon fiber.

The spinning process is a process in which a treatment agent for acrylic fibers is applied to raw acrylic fibers of a precursor to spin the precursor, and preferably includes an application treatment process and a drawing process.
The adhesion treatment step is a step of adhering a treatment agent for acrylic fibers after spinning the raw acrylic fiber of the precursor. That is, the treatment agent for acrylic fibers is adhered to the raw acrylic fiber of the precursor in the adhesion treatment step. When the raw acrylic fiber of the precursor is stretched immediately after spinning, the high-ratio 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 acrylic fiber immediately after spinning.

The precursor is preferably composed of acrylic fibers mainly composed of polyacrylonitrile obtained by copolymerizing at least 95 mol % or more of acrylonitrile and 5 mol % or less of a flame retardant promoting component. As the flame retardant promoting component, a vinyl group-containing compound that is copolymerizable with acrylonitrile can be suitably used. There is no particular restriction on the single fiber fineness of the precursor, but it is preferably 0.1 to 2.0 dtex in terms of the balance between performance and production costs. There is also no particular restriction on the number of single fibers that make up the precursor fiber bundle, but it is preferably 1,000 to 96,000 in terms of the balance between performance and production costs.

The acrylic fiber treatment agent may be applied to the precursor raw material acrylic fiber at any stage in the carbon fiber manufacturing process, but it is preferable to apply it once before the drawing process. It may be applied at any stage before the drawing process, for example immediately after spinning. It may also be applied at any stage after the drawing process, for example immediately after the drawing process, at the winding stage, or immediately before the flame-retardant treatment process. As for the method of application, it may be applied using a roller or the like, or it may be applied by a dipping method, spraying method, etc.

In the attachment process, the application rate of the acrylic fiber treatment agent is preferably 0.1 to 5% by weight, more preferably 0.3 to 1.5% by weight, based on the weight of the precursor, in order to strike a balance between obtaining the effect of preventing adhesion and fusion between fibers and preventing deterioration of the quality of the carbon fiber due to the tarred products of the treatment agent in the carbonization process. Note that the application rate of the acrylic fiber treatment agent here is defined as the percentage of the weight of the non-volatile matter attached to the acrylic fiber treatment agent relative to the weight of the precursor.

The flame-retardant treatment process is a process in which the precursor to which the acrylic fiber treatment agent is attached is converted into a flame-retardant fiber in an oxidizing atmosphere at 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-retardant treatment process, the acrylic fiber after the attachment treatment is heat-treated for 20 to 100 minutes (preferably 30 to 60 minutes) while applying a tension of a draw ratio of 0.90 to 1.10 (preferably 0.95 to 1.05). In this flame-retardant treatment, a flame-retardant fiber with a flame-retardant structure is produced through intramolecular cyclization and oxygen addition to the rings.

The carbonization process is a process in which the flame-resistant fiber is further carbonized in an inert atmosphere at 300 to 2000°C. In the carbonization process, it is preferable to first perform a preliminary carbonization process (first carbonization process) by applying a tension of a draw ratio of 0.95 to 1.15 to the flame-resistant fiber for several minutes in a baking furnace having a temperature gradient from 300°C to 800°C in an inert atmosphere of nitrogen, argon, etc. Then, in order to further advance the carbonization and graphitization, the flame-resistant fiber is heat-treated for several minutes in an inert atmosphere of nitrogen, argon, etc. while applying a tension of a draw ratio of 0.95 to 1.05 to the first carbonization process, and the flame-resistant fiber is carbonized. Regarding the control of the heat treatment temperature in the second carbonization process, 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 of the carbon fiber (tensile strength, elastic modulus, etc.).

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

The carbon fibers obtained in this manner can be surface-treated to increase the adhesive strength with the matrix resin when made into a composite material, depending on the purpose. Gas-phase or liquid-phase treatment can be used as the surface treatment method, and from the viewpoint of productivity, liquid-phase treatment using an electrolyte such as an acid or alkali is 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.

The present invention will be described in detail below with reference to examples, but is not limited to the examples described here. In the following examples, percentages (%) and parts are by weight unless otherwise specified. Each characteristic value was measured according to the method shown below.

<Applying rate of treatment agent>
The precursor after the treatment was applied was alkali-fused with potassium hydroxide/sodium butyrate, 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 colorimetry (wavelength 815 mμ) of silicomolybdenum blue. The silicon content thus determined and the silicon content in the treatment previously determined by the same method were used to calculate the application rate (wt%) of the acrylic fiber treatment agent.
<Firing operation (bundling ability)>
In the precursor calcination step, the condition of the flame-resistant fiber bundle immediately after passing through the flame-resistant furnace was evaluated according to the following criteria.
⊚: The fiber bundle width does not expand, there is no interference with adjacent fiber bundles, and the operability is particularly good.
◯: The fiber bundle width expands slightly, but there is no interference with adjacent fiber bundles, and operability is good.
×: The fiber bundle width is expanded, there is interference with adjacent fiber bundles, fluff is generated, and operability is poor.

<Abrasion resistance>
Using a TM-type frictional embracing force tester TM-200 (manufactured by Daiei Scientific Instruments Co., Ltd.), the precursor strand (12K) was rubbed 1,000 times at a tension of 50 g through three mirror-finished chrome-plated stainless steel needles arranged in a zigzag pattern (reciprocating speed: 300 times/min), and the state of fluffing of the precursor strand was visually evaluated according to the following criteria.
⊚: No fuzzing was observed, just like before abrasion, and abrasion resistance was very good.
A: A few fluffs are observed, but the abrasion resistance is good.
Δ: There is a little bit of fluff and the abrasion resistance is a little poor.
×: Much fuzz, significant single yarn breakage, and poor abrasion resistance.

<Carbon fiber strength>
The measurement was carried out in accordance with the epoxy resin impregnated strand method specified in JIS-R-7601, and the average value of 10 measurements was taken as the carbon fiber strength (GPa).

Example 1
Amino-modified silicone A1, nonionic surfactants E1 and E2, antioxidants F1 and F2, and water were mixed together to form an aqueous emulsion so as to obtain the nonvolatile composition of the treatment agent shown in Table 1, and then compounds B2 and B3 having a five-membered ring structure containing sulfur atoms and nitrogen atoms, Bronsted acid compound C2, hydrophilic solvent D4, and antistatic agent were dissolved and dispersed to prepare a treatment agent for acrylic fibers with a nonvolatile concentration of 30% by weight. The weight percentage of amino-modified silicone A1 in the nonvolatile content of the treatment agent was 85% by weight, the total weight percentage of compounds B2 and B3 having a five-membered ring structure containing sulfur atoms and nitrogen atoms was 0.02% by weight, the weight percentage of Bronsted acid compound C2 was 2.5% by weight, the weight percentage of hydrophilic solvent D4 was 0.18% by weight, the weight percentage of nonionic surfactant E1 was 3% by weight, the weight percentage of nonionic surfactant E2 was 5.3% by weight, the antistatic agent was 3% by weight, and the total weight percentage of antioxidants F1 and F2 was 1% by weight.
The prepared treatment agent was then further diluted with water to obtain a diluted solution having a non-volatile content of 3.0% by weight.
The dilution solution was applied to the raw material acrylic fiber of the precursor obtained by copolymerizing 97 mol % of acrylonitrile and 3 mol % of itaconic acid so that the non-volatile content of the treatment agent was 1.0 wt %, and the precursor was produced through a drawing process (steam drawing, drawing ratio 2.1 times) (single fiber fineness 0.8 dtex, 24,000 filaments). This precursor was flame-resistant treated in a flame-resistant furnace at 250°C for 60 minutes, and then baked in a carbonization furnace with a temperature gradient of 300 to 1400°C under a nitrogen atmosphere to convert it into carbon fiber. The evaluation results of each property value are shown in Table 1.

[Examples 2 to 83, Comparative Examples 1 to 40]
Precursors and carbon fibers after application of the treatment agent were obtained in the same manner as in Example 1, except that the treatment liquid was adjusted so that the non-volatile composition of the treatment agent was as shown in Tables 1 to 12. The evaluation results of each characteristic value are shown in Tables 1 to 12.

The details of the non-volatile composition in Tables 1 to 12 are as follows.
<Amino-modified silicone (A)>
Amino-modified silicone A1: 25° C. kinetic viscosity: 90 mm ² /s, amino equivalent: 3900 g/mol, diamine type (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) BY 16-205)
Amino-modified silicone A2: kinematic viscosity at 25° C.: 60 mm ² /s, amino equivalent: 2700 g/mol (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) BY 16-213)
Amino-modified silicone A3: 25° C. kinematic viscosity: 1200 mm ² /s, amino equivalent: 600 g/mol, diamine type (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) BY 16-849 Fluid)
Amino-modified silicone A4: 25° C. kinematic viscosity: 1500 mm ² /s, amino equivalent: 7500 g/mol, diamine type (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) BY 16-879B)
Amino-modified silicone A5: 25° C. kinematic viscosity: 220 mm ² /s, amino equivalent: 1700 g/mol, diamine type (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) FZ-3760)
Amino-modified silicone A6: 25° C. kinematic viscosity: 3500 mm ² /s, amino equivalent: 6000 g/mol, diamine type (manufactured by Dow Toray Co., Ltd., product name DOWSIL (registered trademark) FZ-3785)
Amino-modified silicone A7: 25° C. kinematic viscosity: 250 mm ² /s, amino equivalent: 7600 g/mol, diamine type (manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-860)
Amino-modified silicone A8: 25° C. kinetic viscosity: 3500 mm ² /s, amino equivalent: 2000 g/mol, diamine type (manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-861)
Amino-modified silicone A9: kinematic viscosity at 25° C.: 1700 mm ² /s, amino equivalent: 3800 g/mol, monoamine type (manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-864)
Amino-modified silicone A10: 25° C. kinematic viscosity: 1300 mm ² /s, amino equivalent: 1700 g/mol, diamine type (manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-867S)
Amino-modified silicone A11: 25° C. kinematic viscosity: 1500 mm ² /s, amino equivalent: 3800 g/mol, diamine type (manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-869)
Amino-modified silicone A12: kinematic viscosity at 25° C.: 7000 mm ² /s, amino equivalent: 4000 g/mol (manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name WACKER (registered trademark) FINISH WT 1200)
Amino-modified silicone A13: kinematic viscosity at 25° C.: 200 mm ² /s, amino equivalent: 4000 g/mol (manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name WACKER (registered trademark) FINISH WT 1270)
Amino-modified silicone A14: kinematic viscosity at 25° C.: 75 mm ² /s, amino equivalent: 8,300 g/mol (manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name WACKER (registered trademark) L653)
Amino-modified silicone A15: kinematic viscosity at 25° C.: 25 mm ² /s, amino equivalent: 800 g/mol (manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name WACKER (registered trademark) L656)
Amino-modified silicone A16: kinematic viscosity at 25° C.: 3300 mm ² /s, amino equivalent: 1800 g/mol (manufactured by Shin-Etsu Chemical Co., Ltd., product name X-22-3939A)
Amino-modified silicone A17: 25° C. kinetic viscosity: 15000 mm ² /s, amino equivalent: 3600 g/mol, diamine type Amino-modified silicone A18: 25° C. kinetic viscosity: 9000 mm ² /s, amino equivalent: 9000 g/mol, diamine type

<Compound (B) and derivatives of compound (B)>
Compound B1: A compound of formula (1) in which R ¹ is an octyl group, and X and Y are hydrogen atoms. Compound B2: A compound of formula (1) in which R ¹ is a methyl group, X is a chlorine atom, and Y is a hydrogen atom. Compound B3: A compound of formula (1) in which R ¹ is a methyl group, and X and Y are hydrogen atoms. Compound B4: A compound of formula (2) in which R ¹ is a hydrogen atom. Compound B5: A compound of formula (2) in which R ¹ is a butyl group. Compound B6: 4-bromothiazole. Compound B7: 2-amino-1,3,4-thiadiazole. Compound B8: Reaction product of B1 and cysteine (molar ratio 1:1).
Compound B9: Sodium salt of B4 <Components other than compound (B) and derivatives of compound (B)>
Compound B'1: 1,4-thiazine Compound B'2: 3-methylthiophene Compound B'3: indole

<Bronsted Acid Compound (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: alkyl ether acetic acid having 12 carbon atoms and 4.5 moles of oxyethylene groups added (manufactured by Kao Corporation, product name Kao Akipo (registered trademark) RLM-45)
Bronsted acid compound C6: an alkyl ether acetic acid having 12 carbon atoms and 6 moles of oxyethylene groups added (manufactured by Taiko Yushi Kagaku Kogyo Co., Ltd., product name: Taipol Soft ECA-490)
Bronsted acid compound C7: an alkyl ether acetic acid having 12 carbon atoms and 10 moles of oxyethylene groups added (manufactured by Kao Corporation, product name Kao Akipo (registered trademark) RLM-100)
Bronsted acid compound C8: an alkyl ether phosphate ester having 18 carbon atoms and 3 moles of oxyethylene groups added (manufactured by Toho Chemical Industry Co., Ltd., trade name Phosphanol (registered trademark) RL-310)
Bronsted acid compound C9: secondary alkyl ether phosphate ester having 12 to 15 carbon atoms and having 3 moles of oxyethylene groups added (manufactured by Toho Chemical Industry Co., Ltd., trade name Phosphanol (registered trademark) RS-410)
Bronsted acid compound C10: secondary alkyl ether phosphate ester having 12 to 15 carbon atoms and having 9 moles of oxyethylene groups added (manufactured by Toho Chemical Industry Co., Ltd., trade name Phosphanol (registered trademark) RS-710)

<Hydrophilic Solvent (D)>
Hydrophilic solvent D1: monoethylene glycol Hydrophilic solvent D2: diethylene glycol Hydrophilic solvent D3: propylene glycol Hydrophilic solvent D4: tripropylene glycol Hydrophilic solvent D5: N,N-dimethylformamide Hydrophilic solvent D6: 1-methyl-2-pyrrolidone

<Nonionic Surfactant (E)>
Nonionic surfactant E1: an alkyl ether having 12 carbon atoms and 3 moles of oxyethylene groups added (manufactured by Kao Corporation, trade name Emulgen (registered trademark) 103)
Nonionic surfactant E2: an alkyl ether having 12 carbon atoms and 6 moles of oxyethylene groups added (manufactured by Kao Corporation, trade name Emulgen (registered trademark) 108)
Nonionic surfactant E3: an alkyl ether having 18 carbon atoms and 13 moles of oxyethylene groups added (manufactured by Kao Corporation, trade name Emulgen (registered trademark) 320P)
Nonionic surfactant E4: Polyoxyethylene tribenzyl phenyl ether (manufactured by Kao Corporation, product name Emulgen (registered trademark) B-66)
Nonionic surfactant E5: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., trade name Olfine (registered trademark) E1010)
Nonionic surfactant E6: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., trade name Olfine (registered trademark) EXP-4123)
Nonionic surfactant E7: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., trade name Olfine (registered trademark) PD-001)
Nonionic surfactant E8: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., product name Surfynol (registered trademark) 104E)
Nonionic surfactant E9: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., product name Surfynol (registered trademark) 440)
Nonionic surfactant E10: Acetylenic surfactant (manufactured by Nisshin Chemical Industry Co., Ltd., product name Surfynol (registered trademark) 485)
Nonionic surfactant E11: A secondary alkyl ether having 12 to 14 carbon atoms and 5 moles of oxyethylene groups added (manufactured by Nippon Shokubai Co., Ltd., trade name Softanol (registered trademark) 50)
Nonionic surfactant E12: A secondary alkyl ether having 12 to 14 carbon atoms and 9 moles of oxyethylene groups added (manufactured by Nippon Shokubai Co., Ltd., trade name Softanol (registered trademark) 90)
Nonionic surfactant E13: A secondary alkyl ether having 12 to 14 carbon atoms and 12 moles of oxyethylene groups added (manufactured by Nippon Shokubai Co., Ltd., trade name Softanol (registered trademark) 120)
Nonionic surfactant E14: Polyoxyethylene polyoxypropylene butyl ether (manufactured by Sanyo Chemical Industries, Ltd., product name Newpol (registered trademark) 50-HB)
Nonionic surfactant E15: Polyoxyethylene polyoxypropylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name Newpol (registered trademark) MAP-4000)
Nonionic surfactant E16: Polyoxyethylene polyoxypropylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name Newpol (registered trademark) PE-64)
Nonionic surfactant E17: Polyoxyalkylene branched decyl ether (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name Noigen (registered trademark) XL-41)
Nonionic surfactant E18: Polyoxyalkylene branched decyl ether (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name Noigen (registered trademark) XL-80)
Nonionic surfactant E19: Nonylphenyl ether having 3 moles of oxyethylene groups added (manufactured by Aoki Oil Industries Co., Ltd., product name Brownon (registered trademark) BNP-30A)
Nonionic surfactant E20: an alkyl ether having 16 carbon atoms and 3 moles of oxyethylene groups added (manufactured by Aoki Oil Industries Co., Ltd., product name Brownon (registered trademark) CH-313)
Nonionic surfactant E21: Nonylphenyl ether having 5 moles of oxyethylene groups added (manufactured by Aoki Oil Industries Co., Ltd., product name Brownon (registered trademark) N-505)

<Other ingredients>
Antioxidant F1: Triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate Antioxidant F2: Dioleyl thiodipropionate Antistatic agent: Ethylene bis(hydroxyethyl)octadecyl ammonium ethyl sulfate

As is clear from Tables 1 to 12, the acrylic fiber treatment agents of the examples have excellent bundling properties in the manufacturing process and flame-resistant process of acrylic fiber for carbon fiber production, compared to the comparative example treatment agents that do not contain amino-modified silicone (A) and/or compound (B), and can produce high-quality carbon fibers.

Claims (11)

A treatment agent for acrylic fibers, comprising an amino-modified silicone (A) and at least one selected from a compound (B) having a five-membered ring structure containing a sulfur atom and a nitrogen atom and a derivative of the compound (B). The treatment agent for acrylic fibers according to claim 1, wherein the compound (B) comprises at least one selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2):

In formula (1), R ¹ is an alkyl group or an aralkyl group having 1 to 12 carbon atoms, or a hydrogen atom, and X and Y are each independently a hydrogen atom or a halogen atom.

(In formula (2), ^R2 is an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.) The treatment agent for acrylic fibers according to claim 1 or 2, further comprising a Bronsted acid compound (C). The acrylic fiber treatment agent according to claim 3, wherein the Bronsted acid compound (C) comprises at least one selected from a carboxylic acid compound, an inorganic acid, a sulfonic acid compound, a phosphoric acid ester compound, a sulfate ester compound, and a phosphonic acid compound. The acrylic fiber treatment agent according to claim 3 or 4, wherein the molar ratio of the Brønsted acid compound (C) to the amino groups of the amino-modified silicone (A) is 0.01 to 5.0. The treatment agent for acrylic fibers according to any one of claims 3 to 5, wherein the total weight of the compound (B) and the derivative of the compound (B) is 0.01 to 50 parts by weight per 100 parts by weight of the Bronsted acid compound (C). The treatment agent for acrylic fibers according to any one of claims 1 to 6, further comprising a hydrophilic solvent (D), the hydrophilic solvent (D) containing at least one selected from the group consisting of a compound represented by the following general formula (3) and an aprotic nitrogen-containing organic compound:

(In formula (3), AO is an oxyalkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 3.) The treatment agent for acrylic fibers according to any one of claims 1 to 7, wherein the weight ratio of the amino-modified silicone (A) to the non-volatile content of the treatment agent is 20 to 90% by weight. The treatment agent for acrylic fibers according to any one of claims 1 to 8, further comprising a nonionic surfactant (E). Acrylic fiber for carbon fiber production, obtained by adhering the acrylic fiber treatment agent according to any one of claims 1 to 9 to the raw acrylic fiber for carbon fiber production. A method for producing carbon fiber, comprising a flame-retardant treatment step of converting the acrylic fiber for producing carbon fiber according to claim 10 into a flame-retardant fiber in an oxidizing atmosphere at 200 to 300°C, and a carbonization treatment step of further carbonizing the flame-retardant fiber in an inert atmosphere at 300 to 2000°C.