阅读说明：本技术 碳纤维前体用处理剂的水性液和碳纤维前体 (Aqueous liquid of treating agent for carbon fiber precursor, and carbon fiber precursor ) 是由 西川武志 土井章弘 于 2020-10-06 设计创作，主要内容包括：本发明涉及碳纤维前体用处理剂的水性液,其通过包含碳纤维前体用处理剂以及水来构成,该碳纤维前体用处理剂含有氨基改性硅酮和分子量分布(Mw/Mn)为1.05～1.50的特定的非离子表面活性剂。上述氨基改性硅酮在25℃的运动粘度可以为50～4000mm～(2)/s。本发明的碳纤维前体附着有上述碳纤维前体用处理剂。(The present invention relates to an aqueous liquid for a carbon fiber precursor treating agent, which comprises a carbon fiber precursor treating agent containing an amino-modified silicone and having a molecular weight distribution (Mw/Mn) of 1.05E to E, and water1.50 of a specific nonionic surfactant. The kinematic viscosity of the amino modified silicone at 25 ℃ can be 50-4000 mm 2 And s. The carbon fiber precursor of the present invention is coated with the carbon fiber precursor treating agent.)

1. An aqueous liquid of a carbon fiber precursor treating agent, which comprises a carbon fiber precursor treating agent containing an amino-modified silicone and a nonionic surfactant having a molecular weight distribution (Mw/Mn) of 1.05 to 1.50, wherein the nonionic surfactant is represented by the following formula 1 and contains R in the formula 1, and water¹2 or more nonionic surfactants having different carbon atoms,

[ solution 1]

In the step of the reaction 1, the reaction mixture,

R¹: a straight-chain hydrocarbon group having 8 to 18 carbon atoms or a branched-chain hydrocarbon group having 8 to 18 carbon atoms;

AO: an oxyalkylene group having 2 to 3 carbon atoms;

R²: a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;

n: 1 to 60.

2. The aqueous liquid of a treatment agent for a carbon fiber precursor according to claim 1, wherein the amino-modified silicone has a kinematic viscosity of 50mm at 25 ℃²/s～4000mm²/s。

3. The aqueous liquid of a carbon fiber precursor treating agent according to claim 1 or 2, wherein the total content ratio of the amino-modified silicone and the nonionic surfactant is 20 to 50 parts by mass and the water is contained in a ratio of 50 to 80 parts by mass, when the total content ratio of the amino-modified silicone, the water, and the nonionic surfactant is 100 parts by mass.

4. The aqueous liquid of a treatment agent for a carbon fiber precursor according to any one of claims 1 to 3, wherein the mass ratio of the content of the amino-modified silicone to the content of the nonionic surfactant is 95/5 to 75/25.

5. A carbon fiber precursor characterized by having the carbon fiber precursor treatment agent according to any one of claims 1 to 4 attached thereto.

Technical Field

The present invention relates to an aqueous liquid of a carbon fiber precursor treatment agent capable of improving the stability over time and the strength of carbon fibers, and a carbon fiber precursor obtained by adding the aqueous liquid of the carbon fiber precursor treatment agent.

Background

Carbon fibers are generally used in various fields such as building materials and transportation equipment as carbon fiber composite materials combined with a matrix resin such as an epoxy resin. Carbon fibers are generally produced as a carbon fiber precursor through, for example, a step of spinning acrylic fibers, a step of drawing the fibers, a step of flame-resistant treatment, and a step of carbonization treatment. A carbon fiber precursor treatment agent is used for improving the bundling property of fibers in the production process of carbon fibers or for suppressing adhesion or fusion between fibers.

Conventionally, there have been known treatment agents for carbon fiber precursors disclosed in patent documents 1 to 3. Patent document 1 discloses an amino-modified silicone oil composition containing a silicone oil agent containing an amino-modified polysiloxane having a specific viscosity, an emulsifier containing a nonionic surfactant, and the like. Patent document 2 discloses a synthetic fiber treatment oil containing a polycyclic aromatic nonionic emulsifier having a specific chemical formula, an amino-modified silicone, and the like. Patent document 3 discloses a silicone oil composition containing silicone and a nonionic surfactant composed of an alkyl chain and a polyoxyalkylene chain.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3459305

Patent document 2: japanese patent No. 4311246

Patent document 3: japanese laid-open patent publication No. 2005-298689

Disclosure of Invention

Problems to be solved by the invention

However, the conventional carbon fiber precursor treating agent has a problem that the stability with time is lowered and the strength of the finally obtained carbon fiber is lowered when stored in an aqueous liquid state.

The present invention addresses the problem of providing an aqueous liquid of a treatment agent for a carbon fiber precursor, which can improve the stability over time and the strength of carbon fibers, and a carbon fiber precursor.

Means for solving the problems

The present inventors have made studies to solve the above problems, and as a result, have found that an aqueous liquid of a treatment agent for a carbon fiber precursor, which contains a nonionic surfactant having a specific molecular weight distribution in addition to an amino-modified silicone, is suitable.

An aqueous liquid of a carbon fiber precursor treating agent according to one aspect of the present invention for solving the above problems is characterized by comprising a carbon fiber precursor treating agent containing an amino-modified silicone and a nonionic surfactant having a molecular weight distribution (Mw/Mn) of 1.05 to 1.50, and water.

In the aqueous liquid of the carbon fiber precursor treating agent, the nonionic surfactant may be represented by the following formula 1.

[ solution 1]

(in the case of chemical formula 1,

R¹: a straight-chain hydrocarbon group having 8 to 18 carbon atoms or a branched-chain hydrocarbon group having 8 to 18 carbon atoms;

AO: an oxyalkylene group having 2 to 3 carbon atoms;

R²: a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;

n: 1 to 60. )

In the aqueous liquid of the carbon fiber precursor treating agent, the nonionic surfactant may contain R in the formula 1¹2 or more nonionic surfactants having different carbon atoms.

In the aqueous liquid of the carbon fiber precursor treating agent, the amino-modified silicone may have a kinematic viscosity at 25 ℃ of 50 to 4000mm²/s。

In the aqueous liquid of the carbon fiber precursor treating agent, when the total content ratio of the amino-modified silicone, the water, and the nonionic surfactant is 100 parts by mass, the total content ratio of the amino-modified silicone and the nonionic surfactant may be 20 to 50 parts by mass, and the water may be contained in a ratio of 50 to 80 parts by mass.

In the aqueous liquid of the carbon fiber precursor treating agent, the mass ratio of the content of the amino-modified silicone to the content of the nonionic surfactant may be 95/5 to 75/25.

The carbon fiber precursor according to another aspect of the present invention is characterized in that the treatment agent for a carbon fiber precursor is attached thereto.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the stability over time and the strength of the carbon fiber can be improved.

Detailed Description

(embodiment 1)

Next, embodiment 1 of an aqueous liquid (hereinafter, simply referred to as an aqueous liquid) for specifically realizing the carbon fiber precursor treating agent of the present invention will be described. The aqueous liquid of the present embodiment contains, as an essential component, a nonionic surfactant having a specific molecular weight distribution in addition to the amino-modified silicone.

The amino-modified silicone has a polysiloxane skeleton formed of (-Si-O-) repeating units, and a part of alkyl side chains of silicon atoms thereof is modified with an amino-modifying group. The amino-modifying group may be bonded to a side chain of the silicone as a main chain, may be bonded to a terminal, or may be bonded to both of them. Examples of the amino group-modifying group include an amino group and an organic group having an amino group. As the organic group having an amino group, the following formula 2 can be exemplified.

[ solution 2]

-R¹-(NH-R²)_z-NH₂

(in formula 2, R¹And R²Alkylene groups having 2 to 4 carbon atoms, each of which may beThe same may be different. z is an integer of 0 or 1. )

Specific examples of the amino-modified silicone having an amino-modified group in the formula 2 include dimethylsiloxane-methyl (aminopropyl) siloxane copolymer (aminopropyl polydimethylsiloxane), aminoethylaminopropylmethylsiloxane-dimethylsiloxane copolymer (aminoterminal polydimethylsiloxane), and the like.

The lower limit of the kinematic viscosity of the amino-modified silicone at 25 ℃ is not particularly limited, but is preferably 50mm²More than s. The lower limit of kinematic viscosity is 50mm²When the amount is more than s, the strength of the carbon fiber can be further improved. The upper limit of the kinematic viscosity of the amino-modified silicone at 25 ℃ is not particularly limited, and is preferably 4000mm²The ratio of the water to the water is less than s. The upper limit of the kinematic viscosity is 4000mm²When the ratio/s is less than or equal to the above range, the stability of the aqueous liquid with time can be further improved. When 2 or more kinds of amino-modified silicones are used, the actual measured value of a mixture of 2 or more kinds of amino-modified silicones used is used for the kinematic viscosity.

The molecular weight distribution (Mw/Mn) of the nonionic surfactant is in the range of 1.05 to 1.50. The molecular weight distribution of the nonionic surfactant is determined by GPC using a mixture of nonionic surfactants mixed in an aqueous liquid as a test sample. The nonionic surfactant to be mixed in the aqueous liquid is a reagent which is not monodisperse and has a wide distribution state of a specific molecular weight distribution, whereby the stability of the aqueous liquid over time can be improved.

The kind of the nonionic surfactant is not particularly limited as long as the above molecular weight distribution condition is satisfied, and examples thereof include a compound obtained by adding an alkylene oxide to an alcohol or a carboxylic acid, an ester compound obtained by adding an alkylene oxide to a carboxylic acid and a polyhydric alcohol, and an ether-ester compound obtained by adding an alkylene oxide to an ester compound obtained by adding a carboxylic acid and a polyhydric alcohol.

Specific examples of the alcohols used as the raw material of the nonionic surfactant include: (1) linear alkyl alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, heneicosanol, docosanol, tricosanol, tetracosanol, pentacosanol, hexacosanol, heptacosanol, octacosanol, nonacosanol, and triacontanol; (2) branched alkyl alcohols such as isopropyl alcohol, isobutyl alcohol, isohexyl alcohol, 2-ethylhexanol, isononyl alcohol, isodecyl alcohol, isotridecyl alcohol, isotetradecyl alcohol, isotridecyl alcohol, isohexadecyl alcohol, isoheptadecyl alcohol, isooctadecyl alcohol, isonicosyl alcohol, isoicosyl alcohol, isoeicosanediol, isoeicosatriol, isotetracosanol, isopentacosanol, hexacosanol, heptacosanol, isooctacosyl alcohol, isonicosyl alcohol, and pentacosanol; (3) linear alkenyl alcohols such as tetradecenol, hexadecenol, heptadecenol, octadecenol, and nonadecenol; (4) branched alkenyl alcohols such as isocetylenol and isostearyl enol; (5) cyclic alkyl alcohols such as cyclopentanol and cyclohexanol; (6) aromatic alcohols such as phenol, benzyl alcohol, monostyrenated phenol, distyrenated phenol, and tristyrenated phenol; and so on.

Specific examples of carboxylic acids used as a raw material of the nonionic surfactant include: (7) linear alkyl carboxylic acids such as octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, and behenic acid; (8) branched alkyl carboxylic acids such as 2-ethylhexanoic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic acid, isocetylic acid, and isostearic acid; (9) linear alkenyl carboxylic acids such as octadecenoic acid, octadecadienoic acid, and octadecatrienoic acid; (10) aromatic carboxylic acids such as benzoic acid; and so on. Alcohols or carboxylic acids may be used as one raw material, or two or more kinds of alcohols or carboxylic acids may be used in combination. Among these, it is preferable to use two or more kinds of alcohols or carboxylic acids in combination from the viewpoint of broadening the molecular weight distribution and further improving the stability of the aqueous liquid with time.

Specific examples of the alkylene oxide used as a raw material of the nonionic surfactant include ethylene oxide, propylene oxide, and the like. The number of moles of alkylene oxide added may be suitably set, and is preferably 0.1 to 60 moles, more preferably 1 to 40 moles, and still more preferably 2 to 30 moles. The addition mole number of the alkylene oxide represents the mole number of the alkylene oxide per 1 mole of the alcohol or carboxylic acid in the raw material to be charged. When the number of moles of alkylene oxide added is 0.1 mole or more, the molecular weight distribution can be easily adjusted to a broad distribution. On the other hand, when the number of moles of alkylene oxide added is 60 moles or less, the strength of the carbon fiber can be further improved.

Specific examples of the polyhydric alcohol used as a raw material of the nonionic surfactant include ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2-methyl-1, 2-propanediol, 1, 5-pentanediol, 1, 6-hexanediol, 2, 5-hexanediol, 2-methyl-2, 4-pentanediol, 2, 3-dimethyl-2, 3-butanediol, glycerin, 2-methyl-2-hydroxymethyl-1, 3-propanediol, 2-ethyl-2-hydroxymethyl-1, 3-propanediol, trimethylolpropane, sorbitan, sorbitol, and the like, Pentaerythritol, sorbitol, and the like.

One kind of the alkylene oxide or the polyhydric alcohol may be used, or two or more kinds of the alkylene oxide or the polyhydric alcohol may be used in combination.

In order to adjust the molecular weight distribution of the nonionic surfactant, a nonionic surfactant having a broad molecular weight distribution can be obtained by using 2 or more nonionic surfactants. In order to obtain a nonionic surfactant having a wide molecular weight distribution, a method of mixing 2 or more nonionic surfactants is exemplified. Further, a nonionic surfactant having a wide molecular weight distribution can be obtained by using 2 or more kinds of raw materials such as alcohols and carboxylic acids and changing the reaction conditions (for example, reducing the amount of the catalyst to be used compared with the usual amount).

Among these nonionic surfactants, a compound represented by the following formula 3 is preferably contained. By using this compound, the stability of the aqueous liquid over time can be further improved.

[ solution 3]

(in the case of the chemical formula 3,

R¹: a straight-chain hydrocarbon group having 8 to 18 carbon atoms or a branched-chain hydrocarbon group having 8 to 18 carbon atoms;

AO: an oxyalkylene group having 2 to 3 carbon atoms;

R²: a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;

n: 1 to 60. )

Furthermore, the nonionic surfactant more preferably contains R in the above formula 3¹2 or more nonionic surfactants having different carbon atoms. By using the nonionic surfactant, the molecular weight distribution can be easily adjusted to a broad distribution. This can further improve the stability of the aqueous liquid over time.

In the aqueous liquid, the content ratio of the amino-modified silicone, the water, and the nonionic surfactant is not particularly limited. In the aqueous liquid, when the total content ratio of the amino-modified silicone, water and the nonionic surfactant is 100 parts by mass, the total content ratio of the amino-modified silicone and the nonionic surfactant is preferably 20 to 50 parts by mass and the water is preferably 50 to 80 parts by mass. By limiting the blending ratio, the stability of the aqueous liquid with time can be further improved.

In the aqueous liquid, the mass ratio of the content of the amino-modified silicone to the content of the nonionic surfactant is not particularly limited. The mass ratio of the content of the amino-modified silicone to the content of the nonionic surfactant is preferably 95/5 to 75/25. By limiting the mixing ratio to this, the stability of the aqueous liquid over time can be further improved.

(embodiment 2)

Next, embodiment 2 of the carbon fiber precursor embodying the present invention will be described. The carbon fiber precursor of the present embodiment is adhered with the carbon fiber treatment agent described in embodiment 1.

In the method for producing a carbon fiber using the carbon fiber precursor of the present embodiment, for example, the aqueous liquid of embodiment 1 is adhered to a raw material fiber of the carbon fiber precursor to obtain a carbon fiber precursor, and then, if necessary, a drying treatment is performed, followed by a yarn-making step. The following steps are carried out: a fire-resistant treatment step for converting the carbon fiber precursor produced in the yarn-making step into a fire-resistant fiber in an oxidizing atmosphere at 200 to 300 ℃, preferably 230 to 270 ℃; and a carbonization treatment step of carbonizing the refractory fiber in an inert atmosphere at 300 to 2000 ℃, preferably 300 to 1300 ℃.

The yarn-forming step is a step of forming a carbon fiber precursor by adhering the aqueous solution of embodiment 1 to a raw material fiber of the carbon fiber precursor, and includes an adhesion treatment step and a drawing step.

The adhesion treatment step is a step of adhering an aqueous liquid after spinning the raw material fiber of the carbon fiber precursor. That is, the aqueous liquid is attached to the raw material fiber of the carbon fiber precursor in the attachment treatment step. The raw material fiber of the carbon fiber precursor is drawn immediately after spinning, but the high-magnification drawing after the adhesion treatment step is particularly referred to as a "drawing step". The stretching step may be a wet heat stretching method using high-temperature water vapor or a dry heat stretching method using a hot roll.

The raw material fiber of the carbon fiber precursor includes, for example, acrylic fiber. The acrylic fiber is preferably composed of a fiber mainly composed of polyacrylonitrile (this polyacrylonitrile is obtained by copolymerizing at least 90 mol% or more of acrylonitrile and 10 mol% or less of a fire-retardant accelerating component). As the flame-retardant accelerating component, for example, a vinyl-containing compound having a copolymerizability with acrylonitrile can be suitably used. The single fiber fineness of the carbon fiber precursor is not particularly limited, and is preferably 0.1 to 2.0dTex in terms of balance between performance and production cost. The number of single fibers constituting the fiber bundle of the carbon fiber precursor is not particularly limited, and is preferably 1,000 to 96,000 in terms of balance between performance and production cost.

The aqueous liquid may be attached to the raw material fiber of the carbon fiber precursor at any stage of the yarn-making step, but is preferably attached at once before the drawing step. In addition, the adhesion may be performed at any stage as long as it is a stage before the stretching step. For example, the adhesion may be performed immediately after spinning. Further, the adhesion may be performed again at any stage after the stretching step. For example, the re-adhesion may be performed immediately after the stretching step, may be performed at the winding stage, or may be performed immediately before the flame-retardant treatment step. In the yarn-making step, the number of times of adhesion is not particularly limited. After the aqueous liquid is attached to the carbon fiber precursor, a drying treatment may be performed as needed. After the adhesion treatment step, water is evaporated from the aqueous solution to adhere the carbon fiber treatment agent to the carbon fibers.

The ratio of the carbon fiber precursor treatment agent of embodiment 1 to be attached to the carbon fiber precursor is not particularly limited, but the carbon fiber precursor treatment agent (including no solvent) is preferably attached so as to be 0.1 to 2 mass%, more preferably 0.3 to 1.2 mass%, relative to the carbon fiber precursor. With this configuration, the effect of the present invention can be further improved. As the method for adhering the aqueous liquid according to embodiment 1, a known method can be applied, and examples thereof include a spray oil feeding method, a dip oil feeding method, a roll oil feeding method, and an oil feeding method using a metering pump.

The operation and effect of the aqueous liquid and the carbon fiber precursor of the present embodiment will be described.

(1) In the present embodiment, a nonionic surfactant having a specific molecular weight distribution is used in the preparation of an aqueous liquid containing an amino-modified silicone and water. This improves the stability of the aqueous liquid over time. Especially, the stability with time at high temperature in summer can be improved. Further, the strength of the carbon fiber synthesized from the carbon fiber precursor obtained by applying the aqueous liquid can be improved.

The above embodiment may be modified as follows. The above-described embodiment and the following modifications can be implemented in combination with each other within a range not technically contradictory.

In the aqueous liquid of the present embodiment, components generally used in the carbon fiber precursor treatment agent, such as a stabilizer, a charge control agent, a thickener, an antioxidant, an antiseptic, an antibacterial agent, a pH adjuster, an ultraviolet absorber, other surfactants, and other silicones, for maintaining the quality of the aqueous liquid, may be further blended within a range not to impair the effects of the present invention.

Examples

Hereinafter, examples and the like will be described in order to more specifically explain the configuration and effects of the present invention, but the present invention is not limited to these examples. In the following description of examples and comparative examples, parts means parts by mass, and% means% by mass.

Test group 1 (production of aqueous liquid of treating agent for carbon fiber precursor)

Method for producing nonionic surfactant (N-1)

Into the autoclave was charged R as a constituent of the above formula 3¹The raw material alcohol (2) was decanol 20 parts, undecanol 50 parts, dodecanol 30 parts, and potassium hydroxide 0.05 part was further added thereto, and the atmosphere was replaced with nitrogen gas. 76 parts of ethylene oxide was slowly added thereto at 150 ℃ to carry out etherification. The potassium hydroxide was subjected to adsorption treatment and then filtered to synthesize a nonionic surfactant (N-1).

Each structure (R) of the nonionic surfactant (N-1) represented by the constitutional formula 3¹、AO、R²) R in "formula 3" of Table 1¹Column "R" for carbon atom number of alkyl group of (1)¹"raw material mixing ratio of (1)," AO in chemical formula 3, "R in chemical formula 3²The "kind of (1)".

Method for producing nonionic surfactants (N-2) to (N-11)

R in "formula 3 based on Table 1 below¹Column "R" for carbon atom number of alkyl group of (1)¹The mixing ratio of raw materials in (1), (AO in formula 3), and (R in formula 3)²Under the column "type(s)" of (A), nonionic surfactants (N-2) to (N-11) were synthesized using the same formulation as described above.

Each structure (R) of the nonionic surfactants (N-2) to (N-11) represented by the composition No. 3¹、AO、R²) R in "formula 3" of Table 1¹Column "R" for carbon atom number of alkyl group of (1)¹Is prepared from raw materials"column of total ratio", "AO in formula 3", and "R in formula 3²The "kind of (1)".

(example 1)

An aqueous solution having a solid content of 35% of the treatment agent for a carbon fiber precursor of example 1 was prepared by sufficiently stirring 30 parts of (a) amino-modified silicone (Si-1), 5 parts of (B) nonionic surfactant (N-4), and 65 parts of ion-exchanged water, and then emulsifying the mixture using a homogenizer.

(examples 2 to 16, comparative examples 1 to 4)

Aqueous liquids of the carbon fiber precursor treatment agents of examples 2 to 16 and comparative examples 1 to 4 were prepared according to the same formulation as in example 1, based on the mixing amounts of (a) the amino-modified silicone, (B) the nonionic surfactant, and water described in the column of "parts by mass" in table 3.

The structures and kinematic viscosities of the silicones (Si-1) to (Si-5), (rSi-6), and (rSi-7) used in the examples and comparative examples are shown in the column "silicone structure" and the column "kinematic viscosity" in Table 2.

The types of (a) the amino-modified silicone and (B) the nonionic surfactant used in each example and comparative example are shown in the column of "type" of each component in table 3. The amounts of the amino-modified silicone (a), the nonionic surfactant (B) and water in the aqueous solution are shown in the column of "parts by mass" of the components in table 3. The total mass of the amino-modified silicone (a) and the nonionic surfactant (B) and the mass ratio of the content of the silicone (a) to the content of the nonionic surfactant (B) in each aqueous liquid are shown in the column of "total mass of components a and B" and the column of "mass ratio of component a/component B" in table 3, respectively.

Method for measuring molecular weight distribution

The molecular weight distribution of the nonionic surfactant was determined by the following method.

First, 0.02g of the mixture of the nonionic surfactants mixed in the aqueous solutions of examples and comparative examples was collected in a vial, and 30mL of Tetrahydrofuran (THF) was added thereto to dilute the mixture, thereby obtaining a sample solution. This sample solution was removed from 1mL using a syringe equipped with a GPC filter in a GPC sample bottle to remove foreign matters, thereby obtaining a sample solution. GPC measurement was carried out using TSKgel SuperH-RC equipped with a reference column, TSKguardcolumn SuperH-L equipped with TSKgel SuperH4000, TSKgel SuperH3000, HLC-8320GPC manufactured by Tosoh Co., Ltd. of TSKgel SuperH2000 equipped with a column for measurement. Regarding the number average molecular weight (═ Mn) and the mass average molecular weight (═ Mw), calibration curves were prepared using TSKgel standard polystyrene as a standard sample, and Mn and Mw of the nonionic surfactant mixture blended in the aqueous solutions of the respective examples and comparative examples were determined. The molecular weight distribution (═ Mw/Mn) was calculated using this value. The results of the molecular weight distribution are shown in the column "molecular weight distribution" in table 3.

[ Table 1]

The details of each nonionic surfactant of N-1 to N-11 described in the grouping columns of Table 1 are as follows.

N-1: polyoxyethylene (n-3: the number of moles of ethylene oxide added, the same applies hereinafter) decyl ether, polyoxyethylene (n-3) undecyl ether, and polyoxyethylene (n-3) dodecyl ether

N-2: mixtures of polyoxyethylene (n-9) decyl ether, polyoxyethylene (n-9) undecyl ether and polyoxyethylene (n-9) dodecyl ether

N-3: mixtures of polyoxyethylene (n-12) decyl ether, polyoxyethylene (n-12) undecyl ether and polyoxyethylene (n-12) dodecyl ether

N-4: mixtures of polyoxyethylene (n-5) lauryl ether and polyoxyethylene (n-5) tridecyl ether

N-5: mixtures of polyoxyethylene (n-10) lauryl ether and polyoxyethylene (n-10) tridecyl ether

N-6: mixture of polyoxyethylene (N ═ 25) lauryl ether and polyoxyethylene (N ═ 25) tetradecyl ether N-7: polyoxyethylene (n-15) polyoxypropylene (m-10: the number of moles of propylene oxide added, the same applies hereinafter) tetradecyl ether and a mixture of polyoxyethylene (n-15) polyoxypropylene (m-10) pentadecyl ether

N-8: mixtures of polyoxyethylene (n-40) polyoxypropylene (m-10) tetradecyl ether and polyoxyethylene (n-40) polyoxypropylene (m-10) pentadecyl ether

N-9: mixtures of polyoxyethylene (n-5) hexadecyl ether and polyoxyethylene (n-5) octadecyl ether

N-10: polyoxyethylene (n ═ 7) octyl ether

N-11: polyoxyethylene (n-5) polyoxypropylene (m-5) butyl ether

[ Table 2]

[ Table 3]

Test group 2 (production of carbon fiber precursor and carbon fiber)

Using the aqueous liquid of the treatment agent for a carbon fiber precursor prepared in test group 1, a carbon fiber precursor and a carbon fiber were produced.

A copolymer having an intrinsic viscosity of 1.80, which was composed of 95% acrylonitrile, 3.5% methyl acrylate and 1.5% methacrylic acid, was dissolved in Dimethylacetamide (DMAC) to prepare a dope having a polymer concentration of 21.0% and a viscosity of 500 poises at 60 ℃. The dope was discharged into a 70% aqueous solution of DMAC (Dimethylacetamide) coagulation bath maintained at a bath temperature of 35 ℃ at a draft ratio of 0.8 through a spinneret having a hole diameter (inner diameter) of 0.075mm and a hole number of 12,000.

The coagulated yarn was desolventized in a rinsing bath and simultaneously stretched 5 times to prepare an acrylic fiber strand in a water-swollen state. This was subjected to an oil feeding by an immersion method using a 4% ion exchange aqueous solution obtained by further diluting the aqueous solution of the carbon fiber precursor treatment agent prepared in test group 1 so that the amount of solid matter adhering to the carbon fiber precursor treatment agent was 1% (excluding solvent). Thereafter, the acrylic fiber strand was subjected to a dry densification treatment using a 130 ℃ heating roll, further subjected to 1.7-fold stretching between 170 ℃ heating rolls, and then wound around a yarn tube, thereby obtaining a carbon fiber precursor. The carbon fiber precursor is unwound from the yarn, and the yarn is subjected to a flame-resistant treatment for 1 hour in an air atmosphere in a flame-resistant furnace having a temperature gradient of 230 to 270 ℃, and then continuously fired in a nitrogen atmosphere in a carbonization furnace having a temperature gradient of 300 to 1,300 ℃ to be converted into carbon fibers, and then wound around a yarn tube.

The stability with time of the aqueous liquid of the carbon fiber precursor treatment agent and the strength of the carbon fiber were evaluated as follows.

Test group 3 (evaluation)

Evaluation of emulsion stability

100mL of an aqueous solution of a carbon fiber precursor treating agent was stored in a transparent closed container, and after standing at 40 ℃ for 3 days, the container was shaken 10 times and then allowed to stand at 40 ℃ for 3 days again. The appearance after standing was visually observed. The stored treatment agent was further diluted with ion-exchanged water so that the solid content became 5%, and the diluted appearance was visually observed. The evaluation was carried out according to the following criteria, and the results are shown in the column of "stability over time" in table 3.

Evaluation criteria for emulsion stability

Excellent: almost no separation and precipitation were observed, and the appearance was uniform. In addition, good emulsifiability was maintained after dilution.

O (good): creaming or separation was slightly observed, but the emulsifying property was good and was at a level that had no practical problem. In addition, good emulsifiability was maintained after dilution.

X (bad): significant creaming or separation was observed. Or precipitation or separation occurs after dilution.

Evaluation of carbon fiber Strength

The strength of the carbon fiber obtained above was measured in accordance with JIS R7606 (corresponding to International Standard ISO 11566:1996), and evaluated in accordance with the following criteria. The results are shown in the column "strength" of table 3.

Evaluation criteria for carbon fiber strength

O (excellent): 3.3GPa or more.

X (bad): less than 3.3 GPa.

-: since stability was poor, evaluation was not performed.

As is clear from the results in table 3, the present invention has an effect of improving the stability with time of the aqueous liquid of the carbon fiber precursor treatment agent and improving the strength of the carbon fiber.