Treatment agent for carbon fiber precursor and use of same

Abstract

The purpose of the present invention is to provide a treatment agent for a carbon fiber precursor, with which it is possible to suppress degradation of a carbon fiber precursor even in cases where the carbon fiber precursor that is produced by applying the treatment agent for a carbon fiber precursor is stored for a long period of time, and with which it is also possible to achieve carbon fibers that have excellent physical properties even in cases where a carbon fiber precursor that has been stored for a long period of time is used.　A treatment agent for a carbon fiber precursor according to the present invention contains a silicone (A) that has an amino group and an aromatic compound (B) that has a diphenylmethane skeleton, and this treatment agent for a carbon fiber precursor satisfies at least one selected from among the condition 1 and the condition 2 described below. Condition 1: The acid value of the treatment agent is 0.1-30 mgKOH / g. Condition 2: A Brønsted acid compound (D) is contained therein, and the proportion of the Brønsted acid compound (D) in the nonvolatile content of the treatment agent is 0.05-10 wt%.

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 (this 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 baking 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 it uniformly (see Patent Documents 1 and 2).

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

[0005] However, when a carbon fiber precursor produced by applying such a treatment agent is stored for a long period of time, there is a problem that the carbon fiber precursor deteriorates over time. Therefore, when a carbon fiber is produced by calcining a carbon fiber precursor that has been stored for a long period of time, there are problems such as the generation of fluff in the calcination process and a decrease in the strength of the carbon fiber after calcination. In view of this conventional technical background, an object of the present invention is to provide a treatment agent for carbon fiber precursors that can suppress the deterioration of a carbon fiber precursor when a carbon fiber precursor produced by applying a treatment agent is stored for a long period of time, a carbon fiber precursor using the treatment agent, and a method for producing carbon fiber 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 containing a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton and satisfying at least one selected from specific condition 1 and specific condition 2 can suppress deterioration of the carbon fiber precursor when the carbon fiber precursor produced by applying the treatment agent for carbon fiber precursors is stored for a long period of time, and have arrived at the present invention.

[0007] That is, the treatment agent for carbon fiber precursors of the present invention includes the following embodiments. <1> A treatment agent for carbon fiber precursors, containing a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton, and satisfying at least one selected from the following conditions 1 and 2. Condition 1: The acid value of the treatment agent is 0.1 to 30 mg KOH / g. Condition 2: The treatment agent contains a Brønsted acid compound (D), and the proportion of the Brønsted acid compound (D) in the non-volatile content of the treatment agent is 0.05 to 10 wt %. <2> The treatment agent for carbon fiber precursors according to <1>, wherein the aromatic compound (B) contains an aromatic compound having an oxyalkylene group. <3> The treatment agent for carbon fiber precursors according to <1> or <2>, wherein the aromatic compound (B) contains an aromatic compound having at least one skeleton selected from a bisphenol A skeleton and a bisphenol F skeleton. <4> The treatment agent for carbon fiber precursors according to any one of <1> to <3>, wherein the aromatic compound (B) contains an aliphatic (poly)oxyalkylene derivative (C). <5> The treatment agent for carbon fiber precursors according to any one of <1> to <4>, which contains a Bronsted acid compound (D). <6> The treatment agent for carbon fiber precursors according to any one of <1> to <5>, which satisfies the conditions 1 and 2. <7> The treatment agent for carbon fiber precursors according to any one of <1> to <6>, which contains an acetylene-based compound (E). <8> The treatment agent for carbon fiber precursors according to any one of <1> to <7>, in which the proportion of the aromatic compound (B) in the non-volatile content of the treatment agent is 10 to 99 wt %. <9> A carbon fiber precursor obtained by adhering the treatment agent for carbon fiber precursors according to any one of <1> to <8> to a raw material carbon fiber precursor for the carbon fiber precursor. <10> A method for producing carbon fibers, comprising: a flame retardant treatment step of converting the carbon fiber precursor according to <9> into a flame retardant fiber; and a carbonization treatment step of further carbonizing the flame retardant fiber.

[0008] The treating agent for carbon fiber precursors of the present invention can suppress deterioration of the carbon fiber precursor even when the carbon fiber precursor produced by applying the treating agent is stored for a long period of time, and carbon fibers with excellent physical properties can be obtained even when a carbon fiber precursor stored for a long period of time is used. The carbon fiber precursor and the method for producing carbon fiber of the present invention can obtain carbon fibers with excellent physical properties even when a carbon fiber precursor stored for a long period of time 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) will be described below. [Silicone (A) Having an Amino Group] The treating agent of the present invention contains a silicone (A) having an amino group. The silicone (A) having an amino group is not particularly limited as long as its main chain is an inorganic siloxane bond (—Si—O—Si—) and it has an organic group having an amino group on the side chain and / or terminal. Examples of the silicone (A) having an amino group include amino-modified silicones and amino polyether-modified silicones. In terms of achieving the effects of the present invention, it is more preferable to include an amino-modified silicone. Note that an 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). Known amino-modified silicones and amino polyether-modified silicones can be used. One or more types of silicone (A) having an amino group may be used.

[0010] The amino group-containing silicone (A) has a kinematic viscosity at 25°C of 50 to 20,000 mm3 in order to achieve uniform adhesion to fibers, suppress the scattering of the treatment agent, and provide fiber bundling properties. ２ The upper limit of the kinematic viscosity is more preferably 15,000 mm ２ / s, more preferably 12000 mm ２ / s, particularly preferably 10,000 mm ２ / s, most preferably 3000 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 preferable, and 200 to 3000 mm ２ / s is particularly preferred.

[0011] The amino group (including an organic group having an amino group) which is the modified group of the amino group-containing silicone (A) may be bonded to a side chain of the silicone main chain, or to an end, or may be bonded to both, but from the viewpoint of protecting the fibers in the flame-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, or a polyamine type, and both may coexist in one molecule, but from the viewpoint of uniformly applying the treatment agent to the inside of the fiber bundle in the flame-resistant treatment step and forming a film with the treatment agent to protect the fibers, the monoamine type or diamine type is preferred, and the diamine type is more preferred.

[0012] The amino equivalent of the amino group-containing 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. Meanwhile, the lower limit of the amino equivalent is more preferably 500 g / mol, even more preferably 1,000 g / mol, and particularly preferably 1,500 g / mol. Furthermore, for example, 500 to 9,000 g / mol is more preferable, and 1,000 to 8,000 g / mol is even more preferable. Here, the amino equivalent refers to the mass of the siloxane skeleton per amino group or ammonium group. The unit of g / mol is a value converted to per mol of amino groups or ammonium groups. Therefore, a smaller amino equivalent value indicates a higher ratio of amino groups or ammonium groups in the molecule.

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

[0014] Examples of the silicone (A) having an amino group include compounds represented by the following general formula (1).

[0015] (In formula (1), R １ represents an alkyl 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. a is 1≦a≦10000, and b is 0≦b≦1000. However, when b=0, R ３ At least one of the repeating units a and b is a group represented by the following general formula (2). The order of the repeating units bounded by a and b is not limited, and the bonding pattern may be alternating, block, or random.

[0016] In formula (1), R １ is preferably an alkyl 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. 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. ９is 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. a is a number from 1 to 10,000, preferably 30 to 5,000, and more preferably 50 to 2,000. b 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 or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and more preferably a hydrogen atom. c is a number from 0 to 6, preferably 0 to 3, and more preferably 0 to 1.

[0019] [Aromatic Compound (B) Having a Diphenylmethane Skeleton] The treatment agent of the present invention contains an aromatic compound (B) having a diphenylmethane skeleton (hereinafter sometimes referred to as aromatic compound (B)). There are no particular limitations on the aromatic compound (B) as long as it is an aromatic compound having a diphenylmethane skeleton. However, in terms of achieving the effects of the present invention, at least one selected from a compound (B-1) having a structure in which an alkylene oxide is added to an aromatic compound having a hydroxyl group and a diphenylmethane skeleton, and an aromatic compound (B-2) having a diphenylmethane skeleton and an ester group is preferred, and a compound (B-1) having a structure in which an alkylene oxide is added to an aromatic compound having a hydroxyl group and a diphenylmethane skeleton is more preferred. One or more types of aromatic compounds (B) having a diphenylmethane skeleton may be used.

[0020] The main skeleton of the aromatic compound (B) having a diphenylmethane skeleton includes, for example, diphenylmethane, more preferably bisphenol. Specific examples of bisphenol include bisphenol A, AP, AF, B, BP, C, E, F, G, M, S, P, PH, TMC, and Z. Among these, in terms of improving sizing ability during flame retardation, at least one selected from the group consisting of bisphenol A skeleton, bisphenol B skeleton, bisphenol E skeleton, and bisphenol F skeleton is preferred, and at least one selected from the group consisting of bisphenol A skeleton and bisphenol F skeleton is more preferred.

[0021] In terms of emulsion stability, it is preferable that the aromatic compound (B) having a diphenylmethane skeleton contains an aromatic compound having an oxyalkylene group. The oxyalkylene group contained in the aromatic compound (B) having a diphenylmethane skeleton is preferably at least one selected from an oxyethylene group and an oxypropylene group, more preferably an oxyethylene group or an oxyethyleneoxypropylene group, and even more preferably an oxyethylene group.

[0022] The compound (B-1) having a structure in which an alkylene oxide is added to an aromatic compound having a hydroxyl group and a diphenylmethane skeleton is not particularly limited as long as it is other than the aromatic compound (B-2) having a diphenylmethane skeleton and an ester group. From the viewpoint of improving sizing ability during flame retardation, preferred are bisphenol A alkylene oxide adducts, bisphenol B alkylene oxide adducts, bisphenol E alkylene oxide adducts, and bisphenol F alkylene oxide adducts, more preferred are bisphenol A ethylene oxide adducts, bisphenol E alkylene oxide adducts, and bisphenol F alkylene oxide adducts, and even more preferred is bisphenol A ethylene oxide adduct.

[0023] The number of moles of alkylene oxide added in compound (B-1) having a structure in which alkylene oxide is added to an aromatic compound having a hydroxyl group and a diphenylmethane skeleton is preferably 2 to 60 moles. The upper limit of the number of moles added is more preferably 30 moles, even more preferably 18 moles, and particularly preferably 10 moles. On the other hand, the lower limit of the number of moles added is more preferably 4 moles, even more preferably 6 moles, and particularly preferably 8 moles. Also, for example, 4 to 18 moles is more preferable, and 6 to 18 moles is particularly preferable. The alkylene oxide preferably includes at least one selected from ethylene oxide and propylene oxide, and more preferably includes ethylene oxide. The alkylene oxide may be added randomly or in blocks.

[0024] The aromatic compound (B-2) having a diphenylmethane skeleton and an ester group is not particularly limited as long as it has a diphenylmethane skeleton and an ester group, and examples thereof include esters of aromatic compounds having a diphenylmethane skeleton and aliphatic carboxylic acids. One or more aromatic compounds (B-2) having a diphenylmethane skeleton and an ester group may be used.

[0025] The aliphatic carboxylic acid constituting the aromatic compound (B-2) having a diphenylmethane skeleton and an ester group is not particularly limited, and examples thereof include an aliphatic monocarboxylic acid having 4 to 24 carbon atoms and an aliphatic polycarboxylic acid having 4 to 24 carbon atoms. The aliphatic carboxylic acid may be saturated or unsaturated, and may be linear or branched.

[0026] Examples of the aliphatic monocarboxylic acid having 4 to 24 carbon atoms include pentanoic acid, hexanoic acid, octanoic acid, 2-ethylhexanoic acid, octylic acid, decanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, isotridecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), isooctadecanoic acid (isostearic acid), hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), octadecenoic acid, hydroxyoctadecenoic acid, octadecadienoic acid, octadecatrienoic acid, docosanoic acid (behenic acid), tetracosanoic acid, hexacosanoic acid, octadocosanoic acid, octacosanoic acid, ricinoleic acid, oleic acid, isostearic acid, and isoarachic acid. In terms of compatibility with the silicone (A) having an amino group, decanoic acid, dodecanoic acid, and tridecanoic acid are preferred.

[0027] Examples of the aliphatic polycarboxylic acid having 4 to 24 carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, itaconic acid, mesaconic acid, and citraconic acid, and succinic acid and adipic acid are preferred in terms of improving sizing properties during flame retardation.

[0028] Examples of the aromatic compound (B-2) having a diphenylmethane skeleton and an ester group include a diester of a bisphenol A alkylene oxide adduct and a fatty acid, a monoester of a bisphenol A alkylene oxide adduct and a fatty acid, a diester of a bisphenol B alkylene oxide adduct and a fatty acid, a monoester of a bisphenol B alkylene oxide adduct and a fatty acid, a diester of a bisphenol E alkylene oxide adduct and a fatty acid, a monoester of a bisphenol E alkylene oxide adduct and a fatty acid, a diester of a bisphenol F alkylene oxide adduct and a fatty acid, a monoester of a bisphenol F alkylene oxide adduct and a fatty acid, etc. Among these, from the viewpoint of improving sizing ability during flame retardation, at least one selected from a diester of a bisphenol A alkylene oxide adduct and a fatty acid, a diester of a bisphenol B alkylene oxide adduct and a fatty acid, and a diester of a bisphenol F alkylene oxide adduct and a fatty acid is preferred.

[0029] [Aliphatic (poly)oxyalkylene derivative (C)] The treatment agent of the present invention may contain an aliphatic (poly)oxyalkylene derivative (C) (hereinafter, sometimes referred to as aliphatic derivative (C)). The aliphatic derivative (C) is not particularly limited as long as it is an aliphatic compound having a (poly)oxyalkylene group. Examples include aliphatic alcohol alkylene oxide adducts (C-1) and aliphatic alkylene oxide adducts (C-2) having an ester group, with aliphatic alcohol alkylene oxide adducts (C-1) being preferred in terms of emulsion stability. One or more types of aliphatic (poly)oxyalkylene derivatives (C) may be used. The aliphatic derivative (C) is other than the Bronsted acid compound (D) and the acetylene-based compound (E) described below.

[0030] Examples of the aliphatic alcohol alkylene oxide adduct (C-1) include alkylene oxide adducts of aliphatic alcohols that do not have an ester group. The aliphatic alcohol constituting the aliphatic alcohol alkylene oxide adduct (C-1) is not particularly limited, but examples include aliphatic alcohols having 2 to 24 carbon atoms. The aliphatic alcohol may be saturated or unsaturated, linear or branched, and may be a monohydric alcohol or a dihydric or higher alcohol. From the viewpoint of emulsion stability, monohydric linear saturated aliphatic alcohols and monohydric branched saturated aliphatic alcohols are preferred. One or more types of aliphatic alcohol alkylene oxide adduct (C-1) may be used. The upper limit of the carbon number of the aliphatic alcohol is preferably 20, more preferably 18, and even more preferably 16. On the other hand, the lower limit of the carbon number is more preferably 4, even more preferably 6, and particularly preferably 8. Furthermore, for example, 6 to 18 is preferred, and 8 to 16 is more preferred.

[0031] Examples of the aliphatic alcohol constituting the aliphatic alcohol alkylene oxide adduct (C-1) include butyl alcohol, octyl alcohol, nonanol, lauryl alcohol, stearyl alcohol, cetyl alcohol, isobutyl alcohol, 2-ethylhexyl alcohol, isododecyl alcohol, isohexadecyl alcohol, isostearyl alcohol, isotetracosanyl alcohol, 12-eicosyl alcohol, vinyl alcohol, butenyl alcohol, hexadecenyl alcohol, oleyl alcohol, eicosenyl alcohol, linear secondary alcohols having 10 to 16 carbon atoms, glycerin, trimethylolpropane, sorbitol, ethylene glycol, propylene glycol, and butylene glycol. From the viewpoint of emulsion stability, lauryl alcohol, stearyl alcohol, isododecyl alcohol, isohexadecyl alcohol, isostearyl alcohol, and linear secondary alcohols having 10 to 16 carbon atoms are preferred, and linear secondary alcohols having 10 to 16 carbon atoms are more preferred.

[0032] The number of moles of alkylene oxide added in the aliphatic alcohol alkylene oxide adduct (C-1) is preferably 2 to 50 moles. The upper limit of the number of moles added is more preferably 40 moles, even more preferably 30 moles, and particularly preferably 20 moles. On the other hand, the lower limit of the number of moles added is more preferably 3 moles, even more preferably 4 moles, and particularly preferably 5 moles. Also, for example, 3 to 40 moles is more preferable, and 5 to 20 moles is particularly preferable. The alkylene oxide preferably contains at least one selected from ethylene oxide and propylene oxide, and more preferably contains ethylene oxide. The alkylene oxide may be added randomly or in blocks.

[0033] Specific examples of the aliphatic alcohol alkylene oxide adduct (C-1) include polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene tetradecyl ether, polyoxyethylene cetyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene isocetyl ether, polyoxyethylene isostearyl ether, polyoxyethylene 1-hexylhexyl ether, polyoxyethylene 1-oct ... Examples of the ethoxylates include polyoxyethylene 1-octylhexyl ether, polyoxyethylene 1-hexyloctyl ether, polyoxyethylene 1-pentylheptyl ether, polyoxyethylene 1-heptylpentyl ether, polyoxyethylene 1-hexylheptyl ether, polyoxyethylene 1-heptylhexyl ether, polyoxyethylene 1-pentylcaptyl ether, polyoxyethylene 1-captylpentyl ether, polyoxyethylene oleyl ether, linear secondary alcohol ethoxylates having 10 to 16 carbon atoms, and oxyethylene-oxypropylene block or random copolymers.

[0034] Examples of the aliphatic alkylene oxide adduct (C-2) having an ester group include those (C-2-1) having a structure in which an alkylene oxide is added to an aliphatic carboxylic acid, those (C-2-2) having a structure in which an alkylene oxide is added to an ester compound of an aliphatic carboxylic acid and a polyhydric alcohol, etc. The aliphatic alkylene oxide adduct (C-2) having an ester group may be used alone or in combination of two or more kinds.

[0035] The aliphatic carboxylic acid constituting the aliphatic alkylene oxide adduct (C-2) having an ester group is not particularly limited, and examples thereof include an aliphatic monocarboxylic acid having 4 to 24 carbon atoms and an aliphatic polycarboxylic acid having 4 to 24 carbon atoms. The aliphatic carboxylic acid may be saturated or unsaturated, and may be linear or branched.

[0036] Examples of the aliphatic monocarboxylic acid having 4 to 24 carbon atoms include pentanoic acid, hexanoic acid, octanoic acid, 2-ethylhexanoic acid, octylic acid, decanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, isotridecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), isooctadecanoic acid (isostearic acid), hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), octadecenoic acid, hydroxyoctadecenoic acid, octadecadienoic acid, octadecatrienoic acid, docosanoic acid (behenic acid), tetracosanoic acid, hexacosanoic acid, octadocosanoic acid, octacosanoic acid, ricinoleic acid, oleic acid, isostearic acid, and isoarachic acid. From the viewpoint of emulsion stability, dodecanoic acid, oleic acid, and isostearic acid are preferred.

[0037] The number of moles of alkylene oxide added in the aliphatic alkylene oxide adduct (C-2) having an ester group is preferably 2 to 50 moles. The upper limit of the number of moles added is more preferably 40 moles, even more preferably 30 moles, and particularly preferably 20 moles. On the other hand, the lower limit of the number of moles added is more preferably 3 moles, even more preferably 4 moles, and particularly preferably 5 moles. Also, for example, 3 to 40 moles is more preferable, and 5 to 20 moles is particularly preferable. The alkylene oxide preferably contains at least one selected from ethylene oxide and propylene oxide, and more preferably contains ethylene oxide. The alkylene oxide may be added randomly or in blocks.

[0038] Examples of the compound (C-2-1) having a structure in which an alkylene oxide is added to an aliphatic carboxylic acid include the compounds in which an alkylene oxide is added to the aliphatic carboxylic acid listed above. From the viewpoint of emulsion stability, a compound having a structure in which 1 to 20 moles of ethylene oxide are added to an aliphatic carboxylic acid having 8 to 18 carbon atoms is preferred.

[0039] The polyhydric alcohol constituting the compound (C-2-2) having a structure in which an alkylene oxide is added to an ester compound of an aliphatic carboxylic acid and a polyhydric alcohol is preferably a dihydric, bromide, or tetrahydric alcohol having 2 to 6 carbon atoms, and more preferably a dihydric, bromide, or trihydric alcohol having 2 to 6 carbon atoms. Specific examples of the polyhydric alcohol include dihydric alcohols such as propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, and 1,6-hexanediol; trihydric alcohols such as glycerin and trimethylolpropane; and tetrahydric or higher alcohols such as pentaerythritol, sorbitan, and sorbitol.

[0040] Examples of the compound (C-2-2) having a structure in which an alkylene oxide is added to an ester compound of an aliphatic carboxylic acid and a polyhydric alcohol include the compounds in which an alkylene oxide is added to the ester compound of an aliphatic carboxylic acid and a polyhydric alcohol listed above. In terms of emulsion stability, alkylene oxide adducts of glycerin fatty acid esters and alkylene oxide adducts of sorbitan fatty acid esters are preferred.

[0041] [Bronsted Acid Compound (D)] The treatment agent of the present invention preferably contains a Bronsted acid compound (D) (hereinafter sometimes referred to as compound (D)) in that it exhibits the effects of the present invention and improves emulsion stability. The Bronsted acid compound (D) 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. The Bronsted acid compound (D) is a compound other than the aromatic compound (B) and the acetylene-based compound (E) described below.

[0042] 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.

[0043] 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.

[0044] 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 polyoxyethylenepolyoxypropylene groups.

[0045] 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.

[0046] The aromatic monocarboxylic acids include benzoic acid, cinnamic acid, naphthoic acid, toluic acid, and derivatives thereof.

[0047] Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and derivatives thereof.

[0048] 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.

[0049] Inorganic acids are acids containing non-metallic atoms, such as sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.

[0050] 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.

[0051] 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.

[0052] Examples of the organic sulfate compound include alkyl sulfate, polyoxyalkylene alkyl sulfate, alkylphenyl sulfate, and polyoxyalkylene alkylphenyl sulfate.

[0053] Examples of the organic phosphonic acid compound include alkyl phosphonic acid, aromatic phosphonic acid, and polyoxyalkylene alkyl ether phosphonic acid.

[0054] The pKa of the Bronsted acid compound (D) 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.

[0055] In terms of improving emulsion stability, the Brønsted acid compound (D) 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. One or more Brønsted acid compounds (D) may be used.

[0056] [Acetylene-based compound (E)] The treatment agent of the present invention preferably contains an acetylene-based compound (E) in that it inhibits the treatment agent from penetrating into the interior of the fiber structure. The acetylene-based compound refers to a compound having an acetylene group and a hydrophilic group such as a hydroxyl group in its molecular structure. The acetylene-based compound (E) may be used alone or in combination of two or more.

[0057] The acetylene compound (E) is preferably an acetylene surfactant, and more preferably at least one selected from acetylene alcohols (E1), acetylene diols (E2), compounds (E3) obtained by adding an alkylene oxide to an acetylene alcohol, and compounds (E4) obtained by adding an alkylene oxide to an acetylene diol. Among these, compounds (E3) obtained by adding an alkylene oxide to an acetylene alcohol and compounds (E4) obtained by adding an alkylene oxide to an acetylene diol are preferred, and compounds (E4) obtained by adding an alkylene oxide to an acetylene diol are even more preferred.

[0058] The acetylene alcohol (E1) is a compound having an acetylene group and one hydroxyl group in its molecular structure. The acetylene alcohol (E1) is preferably a compound represented by the following general formula (3): (In formula (3), R １０ and R １１ are each independently an alkyl group having 1 to 8 carbon atoms.

[0059] The acetylene diol (E2) is a compound having an acetylene group and two hydroxyl groups in its molecular structure. The acetylene diol (E2) is preferably a compound represented by the following general formula (4): (In formula (4), R １２ , R １３ , R １４ and R １５ are each independently an alkyl group having 1 to 8 carbon atoms.

[0060] The compound (E3) obtained by adding an alkylene oxide to an acetylene alcohol is a compound obtained by adding an alkylene oxide to a hydroxyl group of an acetylene alcohol. The compound (E3) obtained by adding an alkylene oxide to an acetylene alcohol is preferably a compound represented by the following general formula (5): (In formula (5), R １０ and R １１ are each independently an alkyl group having 1 to 8 carbon atoms. １６is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. AO is an oxyalkylene group having 2 to 4 carbon atoms. n is a number from 1 to 50.

[0061] The compound (E4) obtained by adding an alkylene oxide to an acetylenic diol is a compound obtained by adding an alkylene oxide to at least one of the hydroxyl groups of an acetylenic diol. The compound (E4) obtained by adding an alkylene oxide to an acetylenic diol is preferably a compound represented by the following general formula (6): (In formula (6), R １２ , R １３ , R １４ and R １５ are each independently an alkyl group having 1 to 8 carbon atoms. １６ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. １６ may be the same or different. AO represents an oxyalkylene group having 2 to 4 carbon atoms. m and n each independently represent a number from 1 to 50.

[0062] In formula (3) and formula (5), R １０ and R １１ are each independently an alkyl group having 1 to 8 carbon atoms. The alkyl group may be linear or may have a branched structure. The number of carbon atoms in the alkyl group is preferably 1 to 7, more preferably 1 to 6, and even more preferably 1 to 5. In formulas (4) and (6), R １２ , R １３ , R １４ and R １５ are each independently an alkyl group having 1 to 8 carbon atoms. The alkyl group may be linear or may have a branched structure. The alkyl group preferably has 1 to 7 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 5 carbon atoms.

[0063] In formula (5) and formula (6), R １６is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. In formulas (5) and (6), AO represents an oxyalkylene group having 2 to 4 carbon atoms. That is, it represents an oxyethylene group, an oxypropylene group, or an oxybutylene group. As the oxyalkylene group, an oxyethylene group or an oxypropylene group is preferred, and an oxyethylene group is more preferred. (AO) ｎ Or (AO) ｍ The AO constituting the formula (I) may be one kind or two or more kinds. When two or more kinds are used, the AO may be any of a block adduct, an alternating adduct, and a random adduct.

[0064] In formula (5), n is a number from 1 to 50. n is preferably a number from 1 to 45, more preferably a number from 1 to 40, and even more preferably a number from 1 to 35. In formula (6), m and n are each independently a number from 1 to 50. m and n are each independently a number from 1 to 45, more preferably a number from 1 to 40, and even more preferably a number from 1 to 35.

[0065] From the viewpoint of emulsifiability, the HLB of the acetylenic compound (E) is preferably 4 to 25. The upper limit of the HLB is more preferably 20, and even more preferably 18. On the other hand, the lower limit of the HLB is more preferably 5, and even more preferably 6. The HLB in the present invention can be experimentally determined by the Atlas method proposed by Griffin et al.

[0066] The acetylene compound (E) is a known compound and can be easily produced by a known method. For example, such a compound can be obtained by a method called the Reppe reaction, in which acetylene is reacted with a ketone or an aldehyde under pressure in the presence of a catalyst such as an alkali or a metal compound. Furthermore, the above-mentioned compound (E3) or compound (E4) can be obtained by addition polymerization of an alkylene oxide (e.g., ethylene oxide and / or propylene oxide) with an acetylene alcohol (E1) or an acetylenic diol (E2), respectively, in the presence of a catalyst such as an alkali or a metal compound.

[0067] [Treatment Agent for Carbon Fiber Precursors] The treatment agent for carbon fiber precursors of the present invention contains a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton, and satisfies at least one selected from the following conditions 1 and 2. Condition 1: The acid value of the treatment agent is 0.1 to 30 mg KOH / g. Condition 2: The treatment agent contains a Brønsted acid compound (D), and the proportion of the Brønsted acid compound (D) in the non-volatile content of the treatment agent is 0.05 to 10 wt %. It is more preferable that the treatment agent for carbon fiber precursors of the present invention satisfies conditions 1 and 2, in order to further exhibit the effects of the present application.

[0068] The treatment agent for carbon fiber precursors of the present invention contains a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton, and satisfies at least one selected from condition 1 and condition 2, so that when a carbon fiber precursor produced by applying the treatment agent is stored for a long period of time, deterioration of the carbon fiber precursor can be suppressed. This is believed to be because the aromatic compound (B) having a diphenylmethane skeleton forms a protective layer on the surface of the carbon fiber precursor, and further because (condition 1) the treatment agent has a specific acid value and / or (condition 2) the proportion of the Brønsted acid (D) in the non-volatile content of the treatment agent is within a specific range, which makes it possible to suppress crosslinking over time caused by oxidation of the amino group of the silicone (A) having an amino group.

[0069] The acid value of the treatment agent of the present invention is preferably 0.1 to 30 mgKOH / g, in terms of easily suppressing deterioration of the carbon fiber precursor over time and facilitating emulsion stabilization. The upper limit of the acid value is more preferred in the following order: (1) 28 mgKOH / g, (2) 25 mgKOH / g, (3) 20 mgKOH / g, (4) 15 mgKOH / g, and (5) 10 mgKOH / g (the larger the value in parentheses, the more preferred it is). Meanwhile, the lower limit of the acid value is more preferred in the following order: (1) 0.2 mgKOH / g, (2) 0.3 mgKOH / g, (3) 0.4 mgKOH / g, (4) 0.5 mgKOH / g, and (5) 0.6 mgKOH / g. (The larger the value in parentheses, the more preferable.) For example, 0.2 to 28 mgKOH / g is more preferable, 0.3 to 25 mgKOH / g is more preferable, 0.4 to 20 mgKOH / g is even more preferable, 0.5 to 15 mgKOH / g is particularly preferable, and 0.6 to 10 mgKOH / g is most preferable. The acid value of the treatment agent in the present invention is determined by the method described in the Examples.

[0070] The proportion of the amino group-containing silicone (A) in the non-volatile content of the treating agent of the present invention is not particularly limited, but is preferably 1 to 90% by weight, from the viewpoints of easily suppressing deterioration over time of the carbon fiber precursor and facilitating emulsion stabilization. The upper limit of this proportion is more preferably 88% by weight, even more preferably 85% by weight, and particularly preferably 80% by weight. Meanwhile, the lower limit of this proportion is more preferably 5% by weight, even more preferably 10% by weight, and particularly preferably 15% by weight. Furthermore, for example, 5 to 88% by weight is more preferable, 10 to 85% by weight is even more preferable, and 15 to 80% by weight is particularly preferable. The non-volatile content concentration in the present invention is determined by spreading 2.0 to 3.0 g of the treatment agent evenly on an aluminum sheet (φ110 mm), drying at 110°C under irradiation with an infrared lamp, accurately weighing the weight of the residue on the aluminum sheet when the fluctuation range of the volatile content over 150 seconds is 0.15%, and calculating the ratio (percentage) of the remaining weight after heating to the weight before heating. The non-volatile content in the present invention refers to the residue on the aluminum sheet when the fluctuation range of the volatile content over 150 seconds is 0.15%, which was determined in the same manner as in the non-volatile content concentration measurement procedure.

[0071] The proportion of the aromatic compound (B) having a diphenylmethane skeleton in the non-volatile content of the treating agent of the present invention is not particularly limited, but is preferably 99% by weight or less in terms of easily suppressing deterioration over time of the carbon fiber precursor and facilitating emulsion stabilization. The upper limit of this proportion is more preferably 95% by weight, even more preferably 90% by weight, and particularly preferably 85% by weight. On the other hand, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Furthermore, for example, 10 to 99% by weight is more preferred, 10 to 90% by weight is even more preferred, 15 to 95% by weight is particularly preferred, and 20 to 85% by weight is most preferred.

[0072] The proportion of the aliphatic (poly)oxyalkylene derivative (C) in the non-volatile content of the treating agent of the present invention is not particularly limited, but is preferably 1 to 30% by weight from the viewpoints of easily suppressing deterioration over time of the carbon fiber precursor and facilitating emulsion stabilization. The upper limit of this proportion is more preferably 25% by weight, even more preferably 20% by weight, and particularly preferably 15% by weight. On the other hand, the lower limit of this proportion is more preferably 2% by weight, even more preferably 3% by weight, and particularly preferably 5% by weight. Furthermore, for example, 2 to 25% by weight is more preferable, 3 to 20% by weight is even more preferable, and 5 to 15% by weight is particularly preferable.

[0073] When the treatment agent of the present invention further contains a Brønsted acid compound (D), the proportion of the Brønsted acid compound (D) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 0.05 to 10 wt % from the viewpoints of easily suppressing deterioration over time of the carbon fiber precursor and easily stabilizing the emulsion. The upper limit of this weight proportion is more preferably 8 wt %, even more preferably 7 wt %, and particularly preferably 5 wt %. Meanwhile, the lower limit of this weight proportion is more preferably 0.1 wt %, even more preferably 0.15 wt %, and particularly preferably 0.3 wt %. Furthermore, for example, 0.1 to 8 wt % is more preferable, 0.15 to 7 wt % is even more preferable, and 0.3 to 5 wt % is particularly preferable.

[0074] When the treatment agent of the present invention further contains an acetylenic compound (E), the proportion of the acetylenic compound (E) in the non-volatile content of the treatment agent of the present invention is not particularly limited, but is preferably 0.1 to 10 wt % in order to suppress penetration of the treatment agent into the interior of the fiber structure. The upper limit of this weight proportion is more preferably 8 wt %, even more preferably 7 wt %, and particularly preferably 5 wt %. Meanwhile, the lower limit of this weight proportion is more preferably 0.3 wt %, even more preferably 0.5 wt %, and particularly preferably 1 wt %. Furthermore, for example, 0.3 to 8 wt % is more preferable, 0.5 to 7 wt % is even more preferable, and 1 to 5 wt % is particularly preferable.

[0075] [Other Component (F)] The treatment agent of the present invention preferably further contains another nonionic surfactant as the other component (F) in order to enhance emulsion stability. The other nonionic surfactant refers to a nonionic surfactant other than the aromatic compound (B) having a diphenylmethane skeleton, the aliphatic (poly)oxyalkylene derivative (C), and the acetylene compound (E). 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.

[0076] When the treatment agent of the present invention contains other nonionic surfactants, the weight proportion of the other nonionic surfactants in the nonvolatile content of the treatment agent is not particularly limited, but from the viewpoint of emulsion stability, it is preferably 0.1 to 10 wt%. The upper limit of this proportion is more preferably 8.5 wt%, even more preferably 7.0 wt%, and particularly preferably 5.0 wt%. Meanwhile, the lower limit of this proportion 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.

[0077] [Other Surfactants] The treatment agent of the present invention may contain surfactants other than the aromatic compound (B) having a diphenylmethane skeleton, the aliphatic (poly)oxyalkylene derivative (C), the Bronsted acid compound (D), the acetylene compound (E), 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 from anionic surfactants, cationic surfactants, and amphoteric surfactants and used. The other surfactants may be used alone or in combination of two or more.

[0078] Examples of anionic surfactants include ether carboxylates, ether sulfates, sulfosuccinates, (poly)oxyethylene coconut oil fatty acid monoethanolamide sodium sulfate, sulfonates having an alkyl group, phosphates having an alkyl group, fatty acid salts, acylated amino acid salts, and amine-neutralized products of fatty acids.

[0079] 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-sulfate; acylamidoalkyl quaternary ammonium salts such as tearamidopropyl 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.

[0080] 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.

[0081] [Other Components] The treating agent for carbon fiber precursors of the present invention may contain other components in addition to the above-mentioned components, as long as the effects of the present invention are not impaired. Examples of other components include antioxidants such as phenols, amines, sulfurs, phosphorus, and quinones; antistatic agents such as quaternary ammonium salt-type cationic surfactants and amine salt-type cationic surfactants; smoothing agents such as alkyl esters of higher alcohols and waxes; antibacterial agents; preservatives; rust inhibitors; and moisture absorbents.

[0082] 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 the amino group-containing silicone (A). The content of the low molecular weight silicone in the treatment agent of the present invention is preferably 5 parts by weight or less per 100 parts by weight of the amino group-containing silicone (A).

[0083] The carbon fiber precursor treatment agent of the present invention preferably comprises an amino group-containing silicone (A), a diphenylmethane skeleton-containing aromatic compound (B), and, optionally, an aliphatic (poly)oxyalkylene derivative (C), a Bronsted acid compound (D), an acetylene compound (E), and other components (F) dissolved, solubilized, emulsified, or dispersed in water. The weight percentage of water and the weight percentage of nonvolatile matter in the entire carbon fiber precursor treatment agent are not particularly limited. These may be determined appropriately, for example, taking into consideration the transportation costs of transporting the carbon fiber precursor treatment agent of the present invention and the ease of handling due to emulsion viscosity. The weight percentage of water in the entire carbon fiber precursor treatment agent is preferably 0.1 to 99.9 wt %, more preferably 10 to 99.5 wt %, and particularly preferably 50 to 99 wt %. The weight ratio (concentration) of the nonvolatile matter in the entire carbon fiber precursor treating 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.

[0084] The treating agent for carbon fiber precursors of the present invention can be produced by mixing the components described above. The method for emulsifying and dispersing the components described above is not particularly limited, and known techniques can be used. Examples of such methods include a method in which each component constituting the treating agent for carbon fiber precursors is added to warm water under stirring to emulsify and disperse the components, and a method in which each component constituting the treating agent for carbon fiber precursors is mixed and then subjected to mechanical shear force using a homogenizer, homomixer, ball mill, or the like while gradually adding water to perform phase inversion emulsification. Alternatively, a method in which some components are emulsified and then the remaining components are dissolved and dispersed may be used.

[0085] The treating agent for carbon fiber precursors of the present invention can be suitably used as a treating agent for carbon fiber precursors.

[0086] [Carbon fiber precursor, its manufacturing method, and carbon fiber manufacturing method] The carbon fiber precursor of the present invention is obtained by adhering the above-mentioned carbon fiber precursor treating agent to a raw material carbon fiber precursor of a carbon fiber precursor and spinning it into a fiber. The method for manufacturing a carbon fiber precursor of the present invention includes a spinning step of adhering the above-mentioned carbon fiber precursor treating agent to a raw material carbon fiber precursor of a carbon fiber precursor and spinning it into a fiber. The method for manufacturing a carbon fiber of the present invention includes a flame-resistant treatment step of converting the carbon fiber precursor having the above-mentioned carbon fiber precursor treating agent adhered thereto into a flame-resistant fiber, and a carbonization treatment step of further carbonizing the flame-resistant fiber. The flame-resistant treatment step is preferably a flame-resistant treatment step of converting the carbon fiber precursor into a flame-resistant fiber in an oxidizing atmosphere at 200 to 300°C, and the carbonization treatment step is preferably a step of further carbonizing the flame-resistant fiber in an inert atmosphere at 300 to 2000°C. According to the carbon fiber manufacturing method of the present invention, the treatment agent for carbon fiber precursor of the present invention is used, so that high-quality carbon fiber can be manufactured even if the carbon fiber precursor manufactured by applying the treatment agent is stored for a long period of time.

[0087] 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.

[0088] The carbon fiber precursor is preferably composed of acrylic fibers whose main component is polyacrylonitrile obtained by copolymerizing at least 95 mol% or more of acrylonitrile and 5 mol% or less of a flame retardant-promoting component. A vinyl group-containing compound copolymerizable with acrylonitrile can be suitably used as the flame retardant-promoting component. The single fiber fineness of the carbon fiber precursor is not particularly limited, but is preferably 0.1 to 2.0 dtex in view 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 view of the balance between performance and production costs.

[0089] The treating agent for carbon fiber precursors may be applied to the raw material carbon fiber precursor of the 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, spraying method, or the like.

[0090] 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.

[0091] 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 usually 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 subjected to a heat treatment for, for example, 20 to 100 minutes (preferably 30 to 60 minutes) while applying a tension at a draw ratio of, for example, 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.

[0092] 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 of, for example, 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 of, for example, a draw ratio of 0.95 to 1.05, in 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] <Treatment Agent Application Rate> The application rate of the treatment agent for carbon fiber precursors was calculated by the ethanol extraction method using a Soxhlet extractor. However, for treatment agents containing silicone, the application rate was calculated using the following method. The carbon fiber precursor to which the treatment agent had been applied was alkali-fused with potassium hydroxide / sodium butyrate, then dissolved in water and adjusted to pH 1 with hydrochloric acid. Sodium sulfite and ammonium molybdate were added to this to develop color, and colorimetric quantification of silicomolybdenum blue (wavelength 815 mμ) was performed to determine the silicon content. The application rate (wt%) of the carbon fiber precursor treatment agent was calculated using the silicon content determined here and the silicon content in the treatment agent previously determined by the same method.

[0097] <Acid Value of Treatment Agent> Measurement was carried out in accordance with the neutralization titration method specified in JIS K0070, and the average value of five measurements was taken as the acid value of the treatment agent.

[0098] <Number of fluffs in carbon fiber bundle> Carbon fibers were produced using carbon fiber precursors stored under the following two conditions, and the number of fluffs was measured by the following method. Storage condition 1: Stored at room temperature for 7 days. 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 pass. ⊚: The number of fluffs was less than 3 fluffs / m, and the number of fluffs was particularly good with little fluff. ◯: The number of fluffs was 3 fluffs / m or more but less than 10 fluffs / m, and the number of fluffs was good with little fluff. ×: The number of fluffs was 10 fluffs / m or more, and the number of fluffs was poor with much fluff.

[0099] <Carbon fiber strength> Carbon fibers were produced using carbon fiber precursors stored under the following two conditions, and measurements were performed in accordance with the test method for tensile properties of single fibers specified in JIS-R-7606. The average value of 10 measurements was taken as the carbon fiber strength (GPa). Storage condition 1: Stored at room temperature for 7 days. Storage condition 2: Stored at room temperature for 12 months. The maintenance rate of carbon fiber strength after changes over time was calculated using the following formula: (Maintenance rate (%)) = (Strength of carbon fiber produced using carbon fiber precursor after storage at room temperature for 12 months) / (Strength of carbon fiber produced using carbon fiber precursor after storage at room temperature for 7 days) × 100

[0100] <Deterioration Inhibition of Carbon Fiber Precursor> In the evaluation of the fluff and carbon fiber strength of the carbon fiber bundle, the deterioration inhibition of the carbon fiber precursor was judged according to the following criteria. Pass was marked with ◯, and fail was marked with ×. Pass criteria: The number of fluff of the carbon fiber bundle was ◯ or more under both storage condition 1 and storage condition 2, and the maintenance rate of carbon fiber strength was 95% or more.

[0101] Example 1: A silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton were mixed to obtain the nonvolatile composition of the treatment agent shown in Table 1. The temperature of the mixture during emulsification was adjusted to 60-80°C, and water was added little by little while stirring using a stirring blade at a blade tip speed of 3 m / s to emulsify. After emulsification, a Brønsted acid compound (D) was dissolved and dispersed to prepare a treatment agent for carbon fiber precursors with a nonvolatile content of 30 wt%. The weight percentage of the silicone (A) in the nonvolatile content of the treatment agent was 15 wt%, the weight percentage of the aromatic compound (B) having a phenylmethane skeleton was 84.5 wt%, and the weight percentage of the Brønsted acid compound (D) was 0.5 wt%. The prepared treatment agent was then further diluted with water to obtain a diluted solution with a nonvolatile content of 3.0 wt%. The 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.

[0102] [Examples 2 to 31, Comparative Examples 1 to 10] The nonvolatile composition was changed as shown in Tables 1 to 4, and when the aliphatic (poly)oxyalkylene derivative (C), the Brønsted acid compound (D), and the acetylene compound (E) were added, they were dissolved and dispersed after emulsification to prepare the treatment agent. Otherwise, treatment agents for carbon fiber precursors, carbon fiber precursors, and carbon fibers were prepared and evaluated in the same manner as in Example 1. The results of evaluating each property value are shown in Tables 1 to 4.

[0103]

[0104]

[0105]

[0106]

[0107] The details of the nonvolatile composition in Tables 1 to 4 are as follows: <Silicone (A) having an amino group> Amino-modified silicone A1: kinematic viscosity at 25°C: 90 mm ２ / s, amino equivalent: 3900 g / mol, side chain diamine type amino-modified silicone A2: 25°C kinematic viscosity: 250 mm ２ / s, amino equivalent: 7600 g / mol, side chain diamine type amino-modified silicone A3: 25°C kinematic viscosity: 1300 mm ２ / s, amino equivalent: 1700 g / mol, side chain diamine type amino-modified silicone A4: 25°C kinematic viscosity: 1500 mm ２ / s, amino equivalent: 3800 g / mol, side chain diamine type amino-modified silicone A5: 25°C kinematic viscosity: 20000 mm ２ / s, amino equivalent: 1800 g / mol, side chain diamine type amino-modified silicone A6: 25°C kinematic viscosity: 1700 mm ２ / s, amino equivalent: 3800 g / mol, side chain monoamine type amino polyether modified silicone A7: 25°C kinematic viscosity: 3300 mm ２ / s, amino equivalent: 1800 g / mol, side chain amino polyether type

[0108] <Aromatic Compounds (B) Having a Diphenylmethane Skeleton> Aromatic compound B1 having a diphenylmethane skeleton: bisphenol A ether having 8 moles of oxyethylene groups added Aromatic compound B2 having a diphenylmethane skeleton: bisphenol A ether having 10 moles of oxyethylene groups Aromatic compound B3 having a diphenylmethane skeleton: bisphenol F ether having 10 moles of oxyethylene groups added Aromatic compound B4 having a diphenylmethane skeleton: bisphenol A ether having 10 moles of oxypropylene groups added Aromatic compound B5 having a diphenylmethane skeleton: bisphenol A ether having 17.5 moles of oxyethylene groups Aromatic compound B6 having a diphenylmethane skeleton: diesterification product of 1 mole of bisphenol A ether having 10 moles of oxyethylene groups added with 2 moles of lauric acid

[0109] <Aliphatic (poly)oxyalkylene derivatives (C)> Aliphatic (poly)oxyalkylene derivative C1: a secondary alkyl ether having 12 to 14 carbon atoms in the alkyl group to which 5 moles of oxyethylene groups have been added. Aliphatic (poly)oxyalkylene derivative C2: a secondary alkyl ether having 12 to 14 carbon atoms in the alkyl group to which 9 moles of oxyethylene groups have been added. Aliphatic (poly)oxyalkylene derivative C3: a secondary alkyl ether having 12 to 14 carbon atoms in the alkyl group to which 12 moles of oxyethylene groups have been added.

[0110] <Bronsted Acid Compound (D)> Bronsted Acid Compound D1: Acetic Acid Bronsted Acid Compound D2: Phosphoric Acid Bronsted Acid Compound D3: Dodecyl ether acetic acid having 10 moles of oxyethylene groups added

[0111] <Acetylenic Compounds (E)> Acetylene-based compound E1: acetylene-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Olfine (registered trademark) E1010) Acetylene-based compound E2: acetylene-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Olfine (registered trademark) EXP-4123) Acetylene-based compound E3: acetylene-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfynol (registered trademark) 104E)

[0112] As can be seen from Tables 1 to 4, the carbon fiber precursor treating agents of Examples 1 to 31 contained a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton, and satisfied at least one selected from Condition 1 and Condition 2, and were therefore able to suppress deterioration of the carbon fiber precursor over time. On the other hand, the carbon fiber precursor treating agents of Comparative Examples 1 and 4 to 10 were not the carbon fiber precursor treating agents of the present invention, and therefore were unable to suppress deterioration of the carbon fiber precursor when the carbon fiber precursor produced by applying the treating agent was stored for an extended period of time. The carbon fiber precursor treating agents of Comparative Examples 2 and 3 had poor emulsion stability and did not adhere uniformly to the precursor, preventing normal production of carbon fiber precursors and making them unusable as treating agents for carbon fiber precursors.

[0113] The treating agent for carbon fiber precursors of the present invention is a treating agent used in producing a treating agent for carbon fiber precursors, and is useful for producing high-quality carbon fibers. The treating agent for carbon fiber precursors of the present invention is treated with the treating agent of the present invention, and is useful for producing high-quality carbon fibers. High-quality carbon fibers can be obtained by the carbon fiber production method of the present invention.

Claims

1. A treatment agent for carbon fiber precursors, comprising a silicone (A) having an amino group and an aromatic compound (B) having a diphenylmethane skeleton, and satisfying at least one of the following conditions 1 and 2: the aromatic compound (B) is at least one selected from the group consisting of a bisphenol A alkylene oxide adduct, a bisphenol B alkylene oxide adduct, a bisphenol E alkylene oxide adduct, and a bisphenol F alkylene oxide adduct; A treatment agent for carbon fiber precursors that satisfies the above condition 1. Condition 1: The acid value of the treatment agent is 0.1 to 30 mgKOH / g. Condition 2: The treating agent contains a Bronsted acid compound (D), and the proportion of the Bronsted acid compound (D) in the nonvolatile components of the treating agent is 0.05 to 10% by weight.

2. A treatment agent for carbon fiber precursors as described in claim 1, wherein the proportion of the aromatic compound (B) in the non-volatile content of the treatment agent is 5 to 99 weight %.

3. The proportion of the silicone (A) having an amino group in the non-volatile content of the treatment agent is 1 to 90 wt %, 2. The treatment agent for carbon fiber precursors according to claim 1, wherein the proportion of the aromatic compound (B) in the non-volatile content of the treatment agent is 10 to 99% by weight.

4. The treating agent for carbon fiber precursors according to any one of claims 1 to 3, which contains an aliphatic (poly)oxyalkylene derivative (C).

5. The treating agent for carbon fiber precursors according to any one of claims 1 to 3, further comprising a Bronsted acid compound (D).

6. The treatment agent for carbon fiber precursors according to any one of claims 1 to 3, which satisfies the conditions 1 and 2.

7. The treating agent for carbon fiber precursors according to any one of claims 1 to 3, further comprising an acetylene-based compound (E).

8. A carbon fiber precursor obtained by adhering the treating agent for carbon fiber precursors according to any one of claims 1 to 3 to a raw material carbon fiber precursor of the carbon fiber precursor.

9. A method for producing a carbon fiber, comprising: 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.