JP6798734B1 - Treatment agent for carbon fiber precursor, carbon fiber precursor, and method for producing flame-resistant fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment agent for a carbon fiber precursor, a carbon fiber precursor, and a method for producing a flame resistant fiber, which can suppress contamination of a flame resistant furnace and fluff of the flame resistant fiber. The present invention is a treatment agent for a carbon fiber precursor containing silicone, wherein a 1% by mass aqueous diluted solution of the treatment agent for a carbon fiber precursor has a pH of 4.0 or more and 10 at 25 ° C. The concentration is 0.0 or less, and the concentration of the low molecular weight siloxane in the treatment agent for the carbon fiber precursor determined by the gas chromatography mass analysis method is 6.9% by mass or less. [Selection diagram] None

Description

The present invention relates to a treatment agent for a carbon fiber precursor, a carbon fiber precursor, and a method for producing a flame-resistant fiber.

In general, carbon fibers or flame-resistant fibers are widely used in various fields such as building materials and transportation equipment as carbon fiber composite materials or flame-retardant / flame-retardant materials combined with a matrix resin such as an epoxy resin. For example, carbon fiber is produced as a carbon fiber precursor through, for example, a step of spinning acrylic fiber, a step of stretching the fiber, a flame resistance step, and a carbonization step. As the carbon fiber precursor, a treatment agent for a carbon fiber precursor may be used in order to suppress the adhesion or fusion between the fibers that occurs in the carbon fiber manufacturing process.

Conventionally, a treatment agent for a carbon fiber precursor disclosed in Patent Document 1 is known. Patent Document 1 describes an aminocarboxylic acid substance with respect to 100 parts by weight of a mixture of a silicone oil containing a predetermined amino-modified polysiloxane, an oil composed of a predetermined lower aliphatic monocarboxylic acid, and a predetermined nonionic emulsifier. A treatment agent for a carbon fiber precursor containing 0.2 to 10 parts by weight is disclosed.

Japanese Unexamined Patent Publication No. 6-220722

However, the conventional treatment agent for a carbon fiber precursor has a problem that the furnace is contaminated in the flame resistance step and the obtained flame resistant fiber is fluffed.
An object to be solved by the present invention is to provide a treatment agent for a carbon fiber precursor, a carbon fiber precursor, and a method for producing a flame resistant fiber, which can suppress contamination of a flame resistant furnace and fluff of the flame resistant fiber. ..

As a result of research to solve the above-mentioned problems, the present inventors have specified a pH within a predetermined range, and a treatment agent for a carbon fiber precursor in which the concentration of low molecular weight siloxane is specified to be a predetermined value or less is very suitable. I found that there is.

In order to solve the above problems, the treatment agent for carbon fiber precursor according to one aspect of the present invention is a treatment agent for carbon fiber precursor containing 30 to 60 % by mass of silicone, and the treatment for carbon fiber precursor. The pH of the 1 mass% aqueous diluted solution of the agent at 25 ° C. is 4.0 or more and 10.0 or less, and the low molecular weight siloxane in the treatment agent for carbon fiber precursor determined by the gas chromatography mass analysis method. The concentration of the above is 6.9% by mass or less.

The treatment agent for a carbon fiber precursor has a silicon strength ratio K2 / K1 of more than 0.4, which is obtained from the following silicon strength before flame resistance treatment (K1) and the following silicon strength after flame resistance treatment (K2). It is preferable to have.

The pre-flame resistance treatment silicon strength (K1) indicates the strength of silicon measured by fluorescent X-ray elemental analysis from the carbon fiber precursor to which the treatment agent for carbon fiber precursor is attached.
The silicon strength (K2) after the flame-resistant treatment is measured by fluorescent X-ray element analysis from the flame-resistant yarn obtained by performing the flame-resistant treatment on the carbon fiber precursor to which the treatment agent for the carbon fiber precursor is attached. Shows the strength of silicon.

In the treatment agent for carbon fiber precursor, the silicon strength ratio K2 / K1 preferably satisfies 0.5 to 0.95.
It is preferable that the treatment agent for carbon fiber precursor further contains a nonionic surfactant.

In the treatment agent for carbon fiber precursors, it is preferable that the nonionic surfactant contains an alkylene oxide adduct of a branched alcohol.
In the treatment agent for carbon fiber precursor, it is preferable that the silicone contains an amino-modified silicone.

In order to solve the above problems, the carbon fiber precursor of another aspect of the present invention is characterized in that the treatment agent for the carbon fiber precursor is attached.
In order to solve the above problems, another method of producing a flame-resistant fiber of the present invention is characterized by subjecting the carbon fiber precursor to a flame-resistant treatment.

According to the present invention, contamination of the flame-resistant furnace and fluffing of flame-resistant fibers can be suppressed.

(First Embodiment)
Hereinafter, a first embodiment in which the treatment agent for a carbon fiber precursor of the present invention (hereinafter, also simply referred to as a treatment agent) is embodied will be described. The treatment agent of the present embodiment contains 30 to 60 % by mass of silicone and has a pH of 4.0 or more and 10.0 or less at 25 ° C. of a 1% by mass aqueous diluted solution of the treatment agent, and is used for gas chromatography. The concentration of low molecular weight siloxane in the treatment agent determined by mass spectrometry is 6.9% by mass or less.

By blending silicone, the effect of the present invention, particularly the fluffing of flame-resistant fibers is suppressed. Specific examples of silicone include, for example, dimethyl silicone, phenyl-modified silicone, amino-modified silicone, amide-modified silicone, polyether-modified silicone, aminopolyether-modified silicone, alkyl-modified silicone, alkyl aralkyl-modified silicone, alkyl polyether-modified silicone, and ester. Examples thereof include modified silicone, epoxy-modified silicone, carbinol-modified silicone, mercapto-modified silicone, and polyoxyalkylene-modified silicone. As the silicone, one kind of silicone may be used alone, or two or more kinds of silicones may be used in combination as appropriate. Of these, amino-modified silicone is preferable. By applying the amino-modified silicone, contamination of the carbonization furnace can be suppressed when the carbonization step is further performed after the flame resistance step.

Kinematic viscosity at 25 ° C. of the silicone is not particularly limited, but is preferably 200mm ² / s~12000mm ² / s. When amino-modified silicone is used as the silicone, the amino equivalent is not particularly limited, but is preferably 1000 to 10000 g / mol.

The treatment agent of the present embodiment preferably further contains a nonionic surfactant. By blending this nonionic surfactant, the treatment agent is emulsified to improve handleability and adhesiveness. As the nonionic surfactant used in the treatment agent of the present embodiment, known ones can be appropriately adopted. Types of nonionic surfactants include, for example, compounds obtained by adding alkylene oxide to alcohols or carboxylic acids, ester compounds of carboxylic acids and polyhydric alcohols, and ester compounds of carboxylic acids and polyhydric alcohols added alkylene oxide. Examples include ether ester compounds.

Specific examples of alcohols used as raw materials for nonionic surfactants include (1) methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, and tetradecanol. , Pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eikosanol, heneicosanol, docosanol, tricosanol, tetracosanol, pentacosanol, hexacosanol, heptacosanol, octacosanol, nonacosanol, triacon Linear alkyl alcohols such as tanol, (2) Isopropanol, Isobutanol, Isohexanol, 2-Ethylhexanol, Isononanol, Isodecanol, Isoddecanol, Isotridecanol, Isotetradecanol, Isotriacontanol, Isohexadeca Noll, isoheptadecanol, isooctadecanol, isononadecanol, isoeicosanol, isoheneicosanol, isodocosanol, isotricosanol, isotetracosanol, isopentacosanol, isohexacosa Branched alkyl alcohols such as ol, isoheptacosanol, isooctacosanol, isononacosanol, isopentadecanol, (3) linear alkenyl alcohols such as tetradecenol, hexadecenol, heptadecenol, octadecenol, nonadecenool, (4) isohexadecene. Branched alkenyl alcohols such as ol and isooctadecenols, (5) cyclic alkyl alcohols such as cyclopentanol and cyclohexanol, (6) phenols, benzyl alcohols, monostyrene phenols, distyrene phenols, tristyrene phenols and the like. Aromatic alcohols and the like can be mentioned.

Specific examples of carboxylic acids used as raw materials for nonionic surfactants include (1) octyl acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, and heptadecane. Linear alkylcarboxylic acids such as acids, octadecanoic acid, nonadecanic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid, (2) 2-ethylhexanoic acid, isododecanoic acid, isotoridecanic acid, isotetradecanoic acid, isohexadecanoic acid, isooctadecanic acid Examples thereof include branched alkylcarboxylic acids such as (3) octadecenoic acid, octadecadienoic acid, linear alkenylcarboxylic acids such as octadecatrienoic acid, and (4) aromatic carboxylic acids such as benzoic acid.

Specific examples of the alkylene oxide used as a raw material for the nonionic surfactant include ethylene oxide and propylene oxide. The number of moles of alkylene oxide added is appropriately set, but is preferably 0.1 to 60 mol, more preferably 1 to 40 mol, and even more preferably 2 to 30 mol. The number of moles of alkylene oxide added indicates the number of moles of alkylene oxide with respect to 1 mole of alcohols or carboxylic acids in the charged raw material.

Specific examples of polyhydric alcohols used as raw materials for nonionic surfactants include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4. -Butandiol, 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, sorbitane, pentaerythritol, sorbitol and the like.

As the above-mentioned nonionic surfactant, one kind of nonionic surfactant may be used, or two or more kinds of nonionic surfactants may be used in combination.
Of these, alkylene oxide adducts of branched alcohols are preferred. When such a nonionic surfactant is used, the fluff of the flame-resistant fiber can be further suppressed.

In the treatment agent of the present embodiment, the lower limit of pH at 25 ° C. when the treatment agent is dissolved in water and adjusted as a 1% by mass aqueous diluent is 4.0 or more, preferably 4.5 or more. When the pH is 4.0 or more, the effect of the present invention is improved. Further, when the pH is 4.5 or more, the fluff of the flame-resistant fiber is particularly suppressed.

Further, the upper limit of pH at 25 ° C. when the treatment agent is dissolved in water and adjusted as a 1% by mass aqueous diluent is 10.0 or less, preferably 9.5 or less. When the pH is 10.0 or less, the effect of the present invention is improved.

A known pH adjuster can be appropriately used to adjust the pH of the treatment agent. Examples of the pH adjuster include organic acids such as octanoic acid, oleic acid, acetic acid, citric acid and tartaric acid, derivatives thereof, salts thereof, inorganic acids such as hydrochloric acid, and alkalis such as sodium hydroxide and potassium hydroxide. Examples include amines such as alkanolamines, alkylamines and alkylene oxide adducts of alkylamines.

The treatment agent of the present embodiment has a concentration of low molecular weight siloxane in the treatment agent determined by gas chromatography-mass spectrometry of 6.9% by mass or less, preferably 6% by mass or less, more preferably 5.0% by mass. It is as follows. When such a concentration is 6.9% by mass or less, the effect of the present invention is improved. The concentration of the low molecular weight siloxane indicates the total content of the low molecular weight (poly) siloxane (including cyclic siloxane) having 6 or less silicon elements in the molecule. Quantitative analysis can be performed for each low molecular weight siloxane by creating a calibration curve for each. The concentration of the low molecular weight siloxane can be adjusted by using a known method, for example, a method such as distillation of a raw material.

The treatment agent of the present embodiment has a lower limit of the silicon strength ratio K2 / K1 obtained from the following pre-flame resistance silicon strength (K1) and the following post-flame resistance silicon strength (K2) of more than 0.4. It is preferably 0.5 or more, and more preferably 0.5 or more. When the silicon strength ratio K2 / K1 satisfies more than 0.4, the silicone-derived component tends to remain on the fiber even after the flame-resistant treatment, so that contamination of the flame-resistant furnace and fluffing of the flame-resistant fiber can be further suppressed.

The upper limit of the silicon strength ratio K2 / K1 described above is preferably 0.95 or less. When the silicon strength ratio K2 / K1 is 0.95 or less, contamination of the carbonization furnace can be suppressed when the carbonization step is further performed after the flame resistance step.

The pre-flame resistance treatment silicon strength (K1) indicates the strength of silicon measured by fluorescent X-ray elemental analysis from the carbon fiber precursor to which the treatment agent for the carbon fiber precursor is attached.
The silicon strength (K2) after the flame-resistant treatment is measured by fluorescent X-ray element analysis from the flame-resistant yarn obtained by performing the flame-resistant treatment on the carbon fiber precursor to which the treatment agent for the carbon fiber precursor is attached. Indicates strength. The intensity of silicon measured by fluorescent X-ray elemental analysis is determined by the detection peak intensity of a signal derived from silicon.

Regarding the carbon fiber precursor to which the treatment agent used for determining the silicon strength before the flame resistance treatment (K1) and the silicon strength after the flame resistance treatment (K2) is attached, the amount of the treatment agent attached is the adhesion during general use. Amounts, such as 1% by weight, are applied.

Further, the flame resistance treatment for determining the silicon strength (K2) after the flame resistance treatment is performed under the condition that the silicon strength (K2) is heated from 150 ° C. to 240 ° C. at a heating rate of 5 ° C./min and then held at 240 ° C. for 1 hour. ..

(Second Embodiment)
Next, a second embodiment embodying the carbon fiber precursor according to the present invention will be described. In the carbon fiber precursor of the present embodiment, the treatment agent of the first embodiment is attached to the raw material fiber of the carbon fiber precursor.

Further, in the method for producing flame-resistant fiber or carbon fiber using the carbon fiber precursor of the present embodiment, first, the above-mentioned treatment agent is attached to the raw material fiber of the carbon fiber precursor to obtain the carbon fiber precursor, and then the carbon fiber precursor is obtained. A yarn-making process for spinning is performed. Next, a flame-resistant treatment step is performed in which the carbon fiber precursor produced in the silk-reeling step is converted into flame-resistant fibers in an oxidizing atmosphere at 200 to 300 ° C., preferably 230 to 270 ° C. Further, when carbon fibers are obtained, a carbonization treatment step of carbonizing the flame-resistant fibers in an inert atmosphere at 300 to 2000 ° C., preferably 300 to 1300 ° C. is performed. The carbonization treatment step may be performed following the flame resistance treatment step.

The yarn-making step is a step of spinning a carbon fiber precursor obtained by adhering the treatment agent of the first embodiment to the raw material fibers of the carbon fiber precursor, and includes an adhering treatment step and a drawing step.
The adhesion treatment step is a step of spinning the raw material fiber of the carbon fiber precursor and then attaching the treatment agent. That is, the treatment agent is adhered to the raw material fiber of the carbon fiber precursor in the adhesion treatment step. Further, the raw material fiber of this carbon fiber precursor is stretched immediately after spinning, and the high-magnification stretching after the adhesion treatment step is particularly called a "stretching step". The stretching step may be a moist heat stretching method using high-temperature steam, or a dry heat stretching method using a hot roller.

Examples of the raw material fiber of the carbon fiber precursor include acrylic fiber and the like. The acrylic fiber is preferably composed of a fiber containing polyacrylonitrile as a main component, which is obtained by copolymerizing at least 90 mol% or more of acrylonitrile and 10 mol% or less of a flame resistance promoting component. As the flame resistance promoting component, for example, a vinyl group-containing compound having copolymerizability with acrylonitrile can be preferably used. The single fiber fineness of the carbon fiber precursor is not particularly limited, but is preferably 0.1 to 2.0 dTex from the viewpoint of the balance between performance and manufacturing cost. 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 from the viewpoint of the balance between performance and manufacturing cost.

The treatment agent may be attached to the raw material fibers of the carbon fiber precursor at any stage of the silk reeling step, but it is preferable to attach the treatment agent once before the drawing step. Further, it may be attached at any stage as long as it is a stage before the stretching step. For example, it may be attached immediately after spinning. Further, it may be reattached at any stage after the stretching step. For example, it may be reattached immediately after the stretching step, may be reattached at the winding step, or may be reattached immediately before the flame resistance treatment step. During the silk reeling process, the number of times of adhesion is not particularly limited.

The ratio of the treatment agent of the first embodiment to the carbon fiber precursor is not particularly limited, but the treatment agent (without solvent) is attached so as to be 0.1 to 2% by mass with respect to the carbon fiber precursor. It is preferable to allow it to adhere, and it is more preferable to attach it so that the content is 0.3 to 1.2% by mass. With such a configuration, the effect of the present invention is further improved. As a method for adhering the treatment agent of the first embodiment, a known method can be applied, and examples thereof include a spray refueling method, an immersion refueling method, a roller refueling method, a guide refueling method using a measuring pump, and the like. Examples of the form for adhering the treatment agent of the first embodiment to the fiber include an organic solvent solution and an aqueous solution.

The actions and effects of the treatment agent and the carbon fiber precursor of the present embodiment will be described.
(1) In the present embodiment, contamination of the flame-resistant furnace and fluffing of the flame-resistant fiber can be suppressed. Further, when the carbonization step is performed after the flame resistance step, contamination of the carbonization furnace can be suppressed.

The above embodiment may be changed as follows.
-The treatment agent of the present embodiment includes surfactants other than the above, such as anionic surfactants, as stabilizers and antistatic agents for maintaining the quality of the treatment agent, as long as the effects of the present invention are not impaired. , Antistatic agents, binders, antioxidants, UV absorbers and other components commonly used in treatment agents may be further added. Examples of the anionic surfactant include alkyl phosphoric acid esters, N-acylamino acid salts, ether carboxylic acid-based surfactants and the like.

Hereinafter, examples and the like will be given in order to make the configuration and effects of the present invention more specific, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, parts mean parts by mass and% means% by mass.

Test Category 1 (Preparation of treatment agent for carbon fiber precursor)
As the treatment agent for the carbon fiber precursor of Reference Example 1, first, 80 g of diamine-type amino-modified silicone (viscosity 250 mm ² / s, equivalent 7600 g / mol) (A-1) and 10 mol of ethylene oxide of isotetradecyl alcohol were used. And 15 g of propylene oxide 6 mol addition (B-1), 4 g of ethylene oxide 10 mol addition (B-2) of isododecyl alcohol, 1-ethyl-2- (heptadecenyl) -4,5-dihydro-3. 1 g of ethyl sulfate (C-1) of − (2-hydroxyethyl) -1H-imidazolinium was added to the beaker and mixed well. A 30% aqueous solution of the treatment agent for the carbon fiber precursor of Reference Example 1 was prepared by gradually adding ion-exchanged water so that the solid content concentration became 30% while continuing stirring.

Each of the carbon fiber precursor treatment agents of Examples 3 to 7, 12 to 15, Reference Examples 1, 2, 8 to 11 and Comparative Examples 1 to 4 uses each component shown in Table 1, and Reference Example 1 It was adjusted in the same way as above.
The types and contents of silicone, the types and contents of nonionic surfactants, and the types and contents of other components in the treatment agents for carbon fiber precursors of each example are shown in the "Silicone" column and "Nonionic" in Table 1. As shown in the "Surfactant" column and the "Other ingredients" column.

Further, a 1% aqueous diluted solution was prepared from a 30% aqueous solution of the treatment agent for carbon fiber precursor, and the pH at 25 ° C. was measured according to a conventional method. The measured pH values are shown in the "pH of 1% aqueous diluent" column of Table 1.

In addition, the concentration of low molecular weight siloxane in the treatment agent for carbon fiber precursor of each example was measured. For the low molecular weight siloxane, the concentration of the low molecular weight (poly) siloxane (including cyclic siloxane) having 6 or less silicon elements in the molecule was measured by gas chromatography-mass spectrometry according to the following conditions. The measurement conditions were an injection temperature of 300 ° C. and a column temperature condition of 100 ° C. to 300 ° C. at 10 ° C./min, and then held at 300 ° C. for 40 minutes. The concentration of low molecular weight (poly) siloxane in the treatment agent is shown in the "Low molecular weight siloxane concentration" column.

In Table 1,
A-1: Viscosity: 250 mm ² / s, equivalent 7600 g / mol, diamine-type amino-modified silicone A-2: Viscosity: 1300 mm ² / s, equivalent 1700 g / mol, diamine-type amino-modified silicone A-3: Viscosity: 1700 mm ² / s, equivalent 3800 g / mol, monoamine type amino-modified silicone A-4: viscosity: 5000 mm ² / s, equivalent 7000 g / mol, diamine-type amino-modified silicone A-5: viscosity: 10000 mm ² / s, equivalent 2000 g / mol, diamine-type amino-modified silicone A-6: viscosity: 600 mm ² / s, equivalent 3000 g / mol, diamine-type amino-modified silicone A-7: viscosity: 10000 mm ² / s dimethyl silicone A-8: viscosity : 500 mm ² / s, ethylene oxide / propylene oxide = 80/20, silicone / polyether mass ratio = 50/50 polyether-modified silicone B-1: 10 mol of ethylene oxide and 6 mol of propylene oxide of isotetradecyl alcohol Additive B-2: 10 mol addition of ethylene oxide of isododecyl alcohol B-3: 8 mol addition of ethylene oxide of isononyl alcohol B-4: 20 mol addition of ethylene oxide of dodecyl alcohol B-5: Tridecyl alcohol C-1: 1-ethyl-2- (heptadecenyl) -4,5-dihydro-3- (2-hydroxyethyl) -1H-ethyl sulfate of imidazolinium C-2: iso Dodecyl phosphate C-3: Lauryl ether (average of 10 mol of ethylene oxide) Acetic acid C-4: Acetic acid C-5: Diethanolamine C-6: Lauroyl sarcosinate C-7: Oleoil sarcosinate.

Test Category 2 (Manufacture of carbon fiber precursors, flame resistant fibers, and carbon fibers)
The carbon fiber precursor, the flame-resistant fiber, and the carbon fiber were produced using the treatment agent for the carbon fiber precursor prepared in Test Category 1.

A copolymer having an ultimate viscosity of 1.80 consisting of 95% by mass of acrylonitrile, 3.5% by mass of methyl acrylate, and 1.5% by mass of methacrylic acid is dissolved in dimethylacetamide (DMAC) to have a polymer concentration of 21.0% by mass. %, A spinning stock solution having a viscosity at 60 ° C. of 500 poise was prepared. The spinning stock solution was discharged into a coagulation bath of a 70% by mass aqueous solution of DMAC maintained at a spinning bath temperature of 35 ° C. from a spinning cap having a pore diameter (inner diameter) of 0.075 mm and a hole number of 12,000 at a draft ratio of 0.8.

The coagulated yarn was stretched 5 times in a water washing tank at the same time as desolvation to prepare a water-swelled acrylic fiber strand. By dipping the 4% ion exchange aqueous solution of the carbon fiber precursor treatment agent prepared in Test Category 1, the adhesion amount of the carbon fiber precursor treatment agent is 1% by mass (solvent-free). I refueled. After that, the acrylic fiber strands are dried and densified with a heating roller at 130 ° C., further stretched 1.7 times between the heating rollers at 170 ° C., and then wound around a thread tube to form a carbon fiber precursor. Obtained. A yarn was unwound from this carbon fiber precursor and treated for flame resistance in an air atmosphere of 200 ° C. to 300 ° C. to obtain a flame resistant fiber. Then, it was calcined in a carbonization furnace having a temperature gradient of 300 to 1,300 ° C. in a nitrogen atmosphere to convert it into carbon fibers, and then wound on a thread tube.

The silicon strength ratio (K2 / K1), contamination of the flame-resistant furnace, fluff during flame resistance, and contamination of the carbonization furnace were evaluated as shown below. The results are shown in the "Silicon strength ratio K2 / K1" column, the "Flame resistance furnace contamination" column, the "Fluff during flame resistance" column, and the "Carbonization furnace contamination" column in Table 1.

Test category 3 (evaluation)
-Measurement conditions for silicon strength ratio (K2 / K1) The carbon fiber precursor obtained in Test Category 2 and the carbon fiber precursor obtained in Test Category 2 were heated at a heating rate of 5 ° C./40 ° C. between 150 and 240 ° C. The flame-resistant fiber obtained by raising the temperature with a temperature gradient of min and performing a flame-resistant treatment at 240 ° C. for 1 hour in an air atmosphere in a flame-resistant furnace was used. The silicon element intensities K1 and K2 were measured by fluorescent X-rays using a scanning fluorescent X-ray elemental analyzer (manufactured by Rigaku Corporation: ZSX Primus), which was cut to 1.5 cm each. The silicon intensity ratio (K2 / K1) was determined from the value of the detected peak intensity of the signal derived from the obtained silicon.

・ Contamination of flame-resistant furnace The cleaning cycle of the flame-resistant furnace due to silica adhesion was evaluated according to the following criteria. A longer cleaning cycle indicates less silica adhesion in the flameproof furnace.

⊚: Cleaning in 3 weeks or more and less than 4 weeks ○: Cleaning in 2 weeks or more and less than 3 weeks ×: Cleaning in less than 2 weeks ・ Fluffing during flameproofing The fluffing after passing through the flameproofing process was visually confirmed and evaluated according to the following criteria. ..

◎: Almost no fluffing and good operability ○: Slight fluffing but no effect on operability ×: Fluff is conspicuous and wrapping of yarn occurs to affect operability ・Contamination of carbonization furnace The cleaning cycle of carbonization furnace due to silica adhesion was evaluated according to the following criteria. A longer cleaning cycle indicates less silica adhesion in the carbonization furnace.

⊚: Can be operated without cleaning in 2 months or more ○: Cleaning in 1 month or more and less than 2 months ×: Cleaning in less than 1 month As is clear from the evaluation results of each example for each comparative example in Table 1. In addition, according to the treatment agent of the present invention, contamination of the flame-resistant furnace and fluffing of the flame-resistant fiber can be suppressed. In addition, pollution of the carbonization furnace can be suppressed.

Claims (8)

A treatment agent for carbon fiber precursors containing 30 to 60 % by mass of silicone.
The pH of the 1% by mass aqueous diluted solution of the carbon fiber precursor treatment agent at 25 ° C. is 4.0 or more and 10.0 or less.
A treatment agent for carbon fiber precursors, wherein the concentration of low molecular weight siloxane in the treatment agent for carbon fiber precursors determined by gas chromatography-mass spectrometry is 6.9% by mass or less. The treatment agent for carbon fiber precursor has a silicon strength ratio K2 / K1 of more than 0.4, which is obtained from the following silicon strength before flame resistance treatment (K1) and the following silicon strength after flame resistance treatment (K2). The treatment agent for a carbon fiber precursor according to claim 1.
The pre-flame resistance treatment silicon strength (K1) indicates the strength of silicon measured by fluorescent X-ray elemental analysis from the carbon fiber precursor to which the treatment agent for carbon fiber precursor is attached.
The silicon strength (K2) after the flame-resistant treatment is measured by fluorescent X-ray element analysis from the flame-resistant yarn obtained by performing the flame-resistant treatment on the carbon fiber precursor to which the treatment agent for the carbon fiber precursor is attached. Shows the strength of silicon. The treatment agent for a carbon fiber precursor according to claim 2, wherein the silicon strength ratio K2 / K1 satisfies 0.5 to 0.95. The treatment agent for a carbon fiber precursor according to any one of claims 1 to 3, further comprising a nonionic surfactant. The treatment agent for a carbon fiber precursor according to claim 4, wherein the nonionic surfactant contains an alkylene oxide adduct of a branched alcohol. The treatment agent for a carbon fiber precursor according to any one of claims 1 to 5, wherein the silicone contains an amino-modified silicone. A carbon fiber precursor to which the treatment agent for a carbon fiber precursor according to any one of claims 1 to 6 is attached. A method for producing a flame-resistant fiber, which comprises treating the carbon fiber precursor according to claim 7 with a flame-resistant treatment.